IPC-D-620-2013
This is the IPC-D-620_Jan2013 variant selected by the 7-31K committee at APEX
2013 (02/20/2013) to serve as the requirement document.
It retains the Performance Classification (1-2-3) but modifies the original draft’s
QA requirement format (N/A/P/D) to an Applicable / Not Applicable format (A/N),
and brings in a new Appendix A (CLASS 3/A Military / Space).
IPC-D-620
DESIGN AND CRITICAL PROCESS
REQUIREMENTS
FOR
CABLE AND WIRING HARNESSES
7-31h/7-31k Wire Harness Design Task Group
Working Draft: IPC-D-620
Includes edits from IPC Fall 2013 meeting (10/17/2013)
Includes working edits from IPC APEX 2014 meeting (03/26/2014)
09/02/2014 – SMTAI14
HIEARARCHY OF IPC DESIGN SPECIFICATIONS
(IPC-D-620 SERIES)
IPC-D-620-1
DESIGN
Appendix A
Class 3/A Military / Space
IPC-HDBK-620
HANDBOOK
Appendix B
Red Plague Control Plan
Appendix C
Restricted Materials
Appendix D
Foreign Object Debris (FOD) Control
Appendix E
Electrical Wire And Cable Acceptance Tests
FOREWORD
Appendix F
Bend Radius
Appendix G
Lead-Free Control Plan (LFCP)
This standard is intended to provide information on the design requirements for cable and wiring harness
design, to the extent that they can be applied to the broad spectrum of cable and wiring harness design.
It is therefore crucial that decisions concerning the choice of product classification, wiring technology,
connectorization requirements, and performance and reliability requirements be made as early as
possible.
IPC-D-620 is supplemented by Appendices A-E and a handbook (IPC-HDBK-620), which provide the
engineering rationale and technical guidance on cable and wiring harness design. The USER needs, as
a minimum, the Design Requirements document (IPC-D-620), and the engineering description of the final
product.
As wiring and connector technology changes, specific requirements will be updated or new requirements
added to the document set.
The IPC invites input on the effectiveness of the documentation and encourages USER response through
completion of ‘‘Suggestions for Improvement’’ forms located at the end of each document
TABLE OF CONTENTS
1.
PURPOSE ..................................................................................................................................... 7
1.1
SCOPE ......................................................................................................................................... 7
1.2
PERFORMANCE / PRODUCT CLASSIFICATION ................................................................................... 7
1.3
DEFINITION OF REQUIREMENTS
1.3.1
REQUIREMENT FORMAT (A/N) ........................................................................................................ 8
1.3.2
LINE DRAWINGS AND ILLUSTRATIONS ............................................................................................. 8
1.4
MEASUREMENT UNITS AND APPLICATIONS ...................................................................................... 8
1.5
DEFINITION OF TERMS ................................................................................................................... 8
1.6
ENGINEERING DOCUMENTATION .................................................................................................... 9
1.7
ORDER OF PRECEDENCE ............................................................................................................... 9
1.7.1
CONFLICT .................................................................................................................................... 9
1.7.2
CLAUSE REFERENCES ................................................................................................................... 9
1.8
APPENDICES ................................................................................................................................ 9
1.9
APPROVAL OF DEPARTURES FROM STANDARDS AND REQUIREMENTS ............................................... 9
2.
APPLICABLE DOCUMENTS ............................................................................................................ 11
2.1
AEROSPACE ............................................................................................................................... 11
2.2
COMMERCIAL ............................................................................................................................. 11
2.3
FEDERAL
2.4
MILITARY HANDBOOKS ................................................................................................................ 12
2.5
MILITARY SPECIFICATIONS........................................................................................................... 12
2.6
REFERENCE ............................................................................................................................... 13
3.
DESIGN PHILOSOPHY .................................................................................................................. 15
3.1
GENERAL DESIGN REQUIREMENTS ............................................................................................... 15
3.1.1
END-PRODUCT REQUIREMENTS ................................................................................................... 16
3.1.1.1
PERFORMANCE AND RELIABILITY ................................................................................................. 16
3.1.1.2
INTERCHANGEABILITY ................................................................................................................. 16
3.1.1.3
DESIGN FOR MAINTENANCE (DOM) ............................................................................................... 16
3.1.1.4
CABLE / HARNESS MANAGEMENT (ROUTING)................................................................................. 16
3.1.1.5
ERGONOMIC DESIGN ................................................................................................................... 17
3.1.1.6
SERVICE LIFE ............................................................................................................................. 17
3.1.2
ENVIRONMENT
3.1.3
STORAGE AND TRANSPORTABILITY .............................................................................................. 17
3.1.4
WORKMANSHIP ........................................................................................................................... 18
..................................................................................................... 7
................................................................................................................................... 12
........................................................................................................................... 17
4.
SELECTION OF PARTS, MATERIALS AND PROCESSES ..................................................................... 19
4.1
COMMONALITY ........................................................................................................................... 19
4.2
FLAMMABILITY ............................................................................................................................ 19
4.3
OUTGASSING.............................................................................................................................. 19
4.4
RESTRICTED MATERIALS / PROCESSES
4.4.1
GLASS / GLASS-LIKE MATERIALS .................................................................................................. 19
4.4.2
CRIMPING OF SOLDER-TINNED AND SOLID CONDUCTORS ............................................................... 19
4.4.3
SPLICES..................................................................................................................................... 20
4.4.4
CUPROUS OXIDE CORROSION (RED PLAGUE) ................................................................................ 20
4.4.5
FLUORINE ATTACK (WHITE PLAGUE) ............................................................................................. 20
4.4.6
LEAD-FREE TIN (<3% PB) TECHNOLOGY – CONTROL LEVEL 2C...................................................... 20
4.5
TIME-CRITICAL OR LIMITED-LIFE ................................................................................................... 21
4.6
WIRE & CABLE
4.6.1
CONDUCTOR SIZING.................................................................................................................... 21
4.6.2
CONDUCTOR MATERIAL AND COATING .......................................................................................... 22
4.6.3
MULTI-CONDUCTOR CABLES ........................................................................................................ 22
4.6.4
COAXIAL CABLES ........................................................................................................................ 23
4.6.5
OPTICAL FIBER, OPTICAL FIBER CABLE, AND OPTICAL FIBER ASSEMBLIES........................................ 23
4.7
CONNECTORS ............................................................................................................................ 24
4.7.1
MATING PROVISIONS ................................................................................................................... 25
4.7.2
MOISTURE PROTECTION .............................................................................................................. 25
4.7.3
PIN ASSIGNMENT ........................................................................................................................ 25
4.7.4
PROTECTION OF CONNECTORS .................................................................................................... 26
4.7.5
PROTECTION OF SEVERED ELECTRICAL CIRCUITS ......................................................................... 26
5
ELECTRICAL REQUIREMENTS ....................................................................................................... 27
5.1
DERATING .................................................................................................................................. 27
5.2
CORONA SUPPRESSION .............................................................................................................. 27
5.3
CIRCUIT CATEGORIES ................................................................................................................. 28
5.3.1
CATEGORY I (POWER AND CONTROL) .......................................................................................... 28
5.3.2
CATEGORY II (HIGH LEVEL SIGNALS) ............................................................................................ 28
5.3.3
CATEGORY III (LOW -LEVEL SIGNALS) ........................................................................................... 28
5.3.4
CATEGORY IV (ELECTRO EXPLOSIVE DEVICE CIRCUITS) ................................................................ 28
5.3.5
CATEGORY V (HIGH-FREQUENCY SIGNALS) .................................................................................. 28
5.4
SHIELDING (BY CIRCUIT CATEGORY)............................................................................................. 28
5.4.1
CATEGORY I CIRCUITS
........................................................................................ 19
.......................................................................................................................... 21
................................................................................................................ 28
5.4.2
CATEGORY II CIRCUITS ................................................................................................................ 28
5.4.3
CATEGORY III CIRCUITS ............................................................................................................... 28
5.4.4
CATEGORY IV CIRCUITS............................................................................................................... 29
5.4.5
CATEGORY V CIRCUITS ............................................................................................................... 29
5.4.6
ADDITIONAL SHIELDING ............................................................................................................... 29
5.5
BONDING ................................................................................................................................... 29
5.6
SHIELD DESIGN AND GROUNDING ................................................................................................. 30
5.6.1
ELECTROMAGNETIC PULSE (EMP) ENVIRONMENT .......................................................................... 30
5.6.2
CATEGORY IV CIRCUITS............................................................................................................... 30
5.6.3
CATEGORY I, II, III, AND V CIRCUITS (NO EMP)................................................................................ 31
5.6.4
UNGROUNDED / FLOATING SHIELD TERMINATIONS (NO EMP) .......................................................... 31
5.6.5
MAGNETIC SHIELDS .................................................................................................................... 31
5.7
CIRCUIT ISOLATION ..................................................................................................................... 31
5.7.1
GROUP-GROUNDING OF INDIVIDUAL SHIELD TERMINATIONS ........................................................... 32
5.7.2
SEPARATION OF REDUNDANT SYSTEMS ........................................................................................ 32
6
ASSEMBLY / FABRICATION REQUIREMENTS ................................................................................... 38
6.1
WIRE TERMINATIONS................................................................................................................... 38
6.1.1
SPLICES (USE OF)....................................................................................................................... 38
6.1.2
DEAD-ENDING ............................................................................................................................ 38
6.1.3
INSULATION COMPATIBILITY WITH SEALING AND SERVICING ........................................................... 39
6.2
FORM LAYOUT FIXTURE ............................................................................................................... 39
6.3
FORMING WIRES INTO CABLES AND HARNESSES ........................................................................... 40
6.4
WIRE LAY ................................................................................................................................... 40
6.5
BEND RADIUS ............................................................................................................................. 40
6.6
PROTECTION AND SUPPORT ........................................................................................................ 40
6.7
ETCHING FLUOROPOLYMER-INSULATED ELECTRICAL WIRE
6.8
IDENTIFICATION AND MARKING..................................................................................................... 41
6.8.1
CABLE AND HARNESS ASSEMBLIES
6.8.2
OPTICAL CABLE .......................................................................................................................... 42
6.8.3
COAXIAL CABLE .......................................................................................................................... 42
6.8.4
CONNECTORS ............................................................................................................................ 42
6.8.5
CLAMP LOCATING MARKS ............................................................................................................ 42
7
QUALITY ASSURANCE REQUIREMENTS
7.1
RESPONSIBILITY FOR INSPECTIONS AND TESTS............................................................................. 44
7.2
CLASSIFICATION OF INSPECTIONS AND TESTS ............................................................................... 44
........................................................... 41
.............................................................................................. 42
......................................................................................... 44
7.3
WORKMANSHIP, ACCEPTANCE, AND TESTING ................................................................................ 44
7.4
QUALIFICATION........................................................................................................................... 44
8
DOCUMENTATION ....................................................................................................................... 46
8.1
DATA ......................................................................................................................................... 46
8.2
CONNECTOR ORIENTATION (CLOCKING) ....................................................................................... 46
8.3
CONNECTOR PIN-OUT ................................................................................................................. 47
8.4
DIMENSIONING AND TOLERANCE .................................................................................................. 47
9
TAILORING ................................................................................................................................. 48
10
DEFINITIONS AND ACRONYMS ...................................................................................................... 50
10.1
DEFINITIONS............................................................................................................................... 50
10.2
ACRONYMS AND ABBREVIATIONS ................................................................................................. 53
APPENDIX A - CLASS 3/A
MILITARY / SPACE .................................................................................................... 56
APPENDIX B - RED PLAGUE CONTROL PLAN ....................................................................................................... 62
APPENDIX C - RESTRICTED MATERIALS / PROCESSES ......................................................................................... 74
APPENDIX D - FOREIGN OBJECT DEBRIS (FOD) CONTROL................................................................................... 80
APPENDIX E - ELECTRICAL WIRE AND CABLE ACCEPTANCE TESTS ...................................................................... 82
APPENDIX F – BEND RADIUS ............................................................................................................................ 84
APPENDIX G – LEAD-FREE CONTROL PLAN (LFCP)............................................................................................. 87
1.
PURPOSE
“Design Requirements for Cable and Wiring Harnesses” is the design requirements companion to
IPC/WHMA-A-620, “Requirements and Acceptance for Cable and Wire Harness Assemblies”, and
IPC/WHMA-A-620(Space), “Space Applications Electronic Hardware Addendum to IPC/WHMA-A-620A”.
With the present transition from prescriptive ‘‘how to’’ specifications to performance-based standards,
much of the design requirements were removed from IPC/WHMA-A-620A and IPC/WHMA-A-620AS.
The intent of this document is to set forth the general design requirements for electrical wiring harnesses
and cable assemblies. The target USER of this document is a design engineer, manufacturing engineer,
quality engineer, or other individual responsible for the tailoring of specific requirements of this document
to the applicable performance class.
For purposes of this document, the Supplier is considered the Design Authority.
1.1
SCOPE
This document provides design and critical process requirements and technical insight that have been
removed from the acceptance standards for cable and wire harness assemblies. Reference materials
listed in this text are among those considered as required reading. The USER is encouraged to obtain all
relevant referenced materials as this document cannot (nor can any single document) cover every
material, process, environment, performance, or safety aspect that affect a given design.
1.2
PERFORMANCE / PRODUCT CLASSIFICATION
This document recognizes that electrical wiring harnesses and cable assemblies are subject to
performance / product classifications by intended end-item use. Three general end-product classes have
been established to reflect differences in producibility, complexity, functional performance requirements,
and verification (inspection/test) frequency. It SHOULD be recognized that there may be requirement
overlaps between classes.
The USER is responsible for defining the product class. The contract shall [A1A2A3] specify the
performance class required, whether compliance to any of the A through E Appendices is required, and
indicate any exceptions to specific parameters where appropriate.”
CLASS 1 - General Electronic Products
Includes consumer products, as well as general military hardware suitable for applications where
cosmetic imperfections are not important and the major requirement is function of the completed
assembly.
CLASS 2 - Dedicated Service Electronic Products
Includes products where continued performance and extended life is required, and for which
uninterrupted service is desired but not critical. Typically, the end-use environment would not cause
failures.
CLASS 3 - High Performance Electronic Products
Includes products where continued high performance or performance-on-demand is critical, equipment
downtime cannot be tolerated, end-use environment may be uncommonly harsh, and the equipment must
function when required, such as life support or other critical systems.
Space
Space classification deviations to IPC-D-620 are defined and listed in Appendix A.
1.3
DEFINITION OF REQUIREMENTS
The imperative form of action verbs are used throughout this document to identify design requirements
that may require compliance, depending upon the Performance Classification of the hardware. To assist
the USER, these action verbs are in bold text.
a. SHALL / SHALL NOT. The words shall or shall not are used whenever a requirement is intended to
express a provision that is mandatory. Deviation from a shall or shall not requirement for a
particular Performance Class may be considered if sufficient technical rationale / objective evidence
(OE) is supplied to the USER to justify the exception.
b. SHOULD / MAY. The words should and may are used whenever a requirement is intended to
express a provision that is non-mandatory, and which reflects general industry practice and / or
procedure.
c.
WILL. The word will is used to express a declaration of purpose and is intended to express an action
that is mandatory.
1.3.1
REQUIREMENT FORMAT (A/N)
To assist the USER, each requirement is identified by its Performance Classification (x1x2x3) and
applicability, where “x” represents:
N = No requirement has been established for this Class
A = Applicable
Examples:
[A1A2A3] is Applicable for all Classes
[N1N2A3] is Not Established Class 1 and Class 2, and Applicable Class 3
[N1N2N3] is Not Established for all Classes
Applicability for a Class 1 product means that the characteristic is also applicable for Class 2 and 3. A
applicability for a Class 2 product means that the characteristic is also applicable for a Class 3
product, but may not be applicable for a Class 1 product where less demanding criteria may apply.
1.3.2
LINE DRAWINGS AND ILLUSTRATIONS
Line drawings and illustrations are depicted herein to assist in the interpretation of the written
requirements of this standard. The written requirement always takes precedence over the drawings
and illustrations.
1.4
MEASUREMENT UNITS AND APPLICATIONS
All dimensions and tolerances, as well as other forms of measurement in this standard are expressed in
SI (System International) units (with Imperial English equivalent dimensions provided in brackets).
Dimensions and tolerances use millimeters (mm) as the main form of dimensional expression;
micrometers are used when the precision required makes millimeters too cumbersome.
Non-dimensional units, expressed as wire / wire harness / cable diameters (d) are expressed where a
numerical dimension is solely dependent on a physical attribute of the hardware (e.g.: wire gauge,
harness diameter, etc.). For the purposes of determining conformance to this specification, all specified
limits in this standard are absolute limits as defined in ASTM E29.
1.5
DEFINITION OF TERMS
For purposes of this document, the acronyms, abbreviations, and terms used, but in addition to those
listed in IPC-T-50, “Terms and Definitions for Interconnecting and Packaging Electronic Circuits” are listed
in Section 10 “Definitions and Acronyms”. Specialized definitions and acronyms related to “Red Plague”
are listed in Appendix B.
1.6
ENGINEERING DOCUMENTATION
The design engineer is responsible for ensuring that all applicable design details are clearly and
completely depicted on the engineering documentation (drawings). Drawings shall document, including
the appropriate Product Class, that cable and harness assemblies shall [A1A2A3] be fabricated,
inspected, and tested in accordance with IPC/WHMA-A-620 and/or IPC/WHMA-A-620 (SPACE), for the
particular Product Class, unless otherwise specified by the USER.
1.7
ORDER OF PRECEDENCE
The contract always takes precedence over this document, referenced standards and drawings.
1.7.1
CONFLICT
a. In the event of conflict between the requirements of this document and the approved assembly
drawing(s)/documentation, the USER approved assembly drawing(s) / documentation shall
[A1A2A3] govern.
b. In the event of a conflict between the text of this document and the applicable documents cited
herein, the text of this document shall [A1A2A3] take precedence.
c.
In the event of conflict between the requirements of this document and an assembly drawing(s)/
documentation that has not been USER approved, this document shall [A1A2A3] govern.
d. If no criteria is specified, required, or cited, criteria shall [A1A2A3] be established and agreed upon
between the Manufacturer and USER.
1.7.2
CLAUSE REFERENCES
When a clause in this document is referenced, its subordinate clauses shall [A1A2A3] also apply.
1.8
APPENDICES
Appendices to this document shall not [D1D2D3] be binding, unless separately and specifically included
by the applicable contract, approved drawing(s), or purchase order. When contractually invoked, the
applicable requirements of appendices shall be imposed on all applicable subcontracts, assembly
drawing(s), documentation and purchase orders.
1.9
APPROVAL OF DEPARTURES FROM STANDARDS AND REQUIREMENTS
Special requirements may exist which are not covered by, or do not comply with, the visual examples
depicted in this document, and which are in conflict with program-specific documents, and / or programspecified design requirements.
This document may be tailored for the specific application or program prior to contract award.
Engineering documentation shall [A1A2A3] contain the details for such instances, and take precedence
over appropriate sections of this document and the applicable requirements document(s).
Suppliers are encouraged to identify to the USER, any requirements imposed by this document that are
believed to be excessive or not applicable to the design and intended use. Departures from standards or
requirements imposed by this document, or use of requirements that conflict with program-specific
documents or design requirements, shall [A1A2A3] require prior USER Approval unless specifically
allowed by contract.
See Section 9 Tailoring for additional information.
THIS PAGE IS INTENTIONALLY BLANK.
2.
APPLICABLE DOCUMENTS
The following documents form a part of this document to the extent specified herein. Unless otherwise
specified, the issue in effect on the date of bids, or request for proposal, shall [A1A2A3] apply.
2.1
AEROSPACE
AIR1329 ................................. Compatibility of Electrical Connectors and Wiring
AIR4487 ................................ Investigation of Silver Plated Conductor Corrosion (Red Plague)
AIR4789 ................................ Evaluating Corrosion Testing of Electrical Connectors and Accessories
for the Purpose of Qualification
AIR5468 ................................ Ultraviolet (UV) Lasers for Aerospace Wire Marking
AIR5558 ................................ Ultraviolet (UV) Laser Marking Performance of Aerospace Wire
Constructions
AIR5575 ................................. Hot Stamp Wire Marking Concerns for Aerospace Vehicle Applications
AIR5717 ................................ Mitigating Wire Insulation Damage during Processing and Handling
AMS2491 ............................... Surface Treatment of Polytetrafluoroethylene, Preparation for Bonding
AS4373 .................................. Test Methods for Insulated Electric Wire
AS4461 .................................. Assembly and Soldering Criteria For High Quality/High Reliability
Soldered Wire And Cable Termination In Aerospace Vehicles
AS5382 .................................. Aerospace Cable, Fiber Optic
AS5649 .................................. Wire and Cable Marking Process, UV Laser
AS7928 .................................. Terminals, Lug: Splices, Conductor: Crimp Style, Copper, General
Specification For
AS22759.................................. Wire, Electric, Fluoropolymer-Insulated Copper or Copper Alloy (Slash
Sheet: /11, /89B, /90B, 91B, /92B)
AS83519 ................................ Shield Termination, Solder Style, Insulated, Heat-Shrinkable,
Environment Resistant, General Specification For (Slash Sheet: /1, /2)
AS9100 .................................. Quality Management Systems - Requirements for Aviation, Space and
Defense Organizations
2.2
COMMERCIAL
A-A-52083 ............................. Commercial Item Description, Tape, Lacing and Tying, Glass
A-A-59569 ............................. Commercial Item Description, Braid, Wire (Copper, Tin-Coated, SilverCoated, or Nickel Coated, Tubular or Flat)
ANSI/EIA-359-A ..................... Standard Colors for Color Identification and Coding
ANSI/NEMA WC 27500 ........ Standard for Aerospace and Industrial Electrical Cable
ASME Y14.100 ...................... Engineering Drawing Practices
ASME Y14.24 ........................ Types and Applications of Engineering Drawings
ASME Y14.34M ..................... Associated Lists
ASME Y14.35M ..................... Revision of Engineering (Chapter Drawings and Associated Lists)
ASTM B174-10 ...................... Standard Specification for Bunch-Stranded Copper Conductors for
Electrical Conductors
ASTM B8-11 .......................... Standard Specification for Concentric-Lay-Stranded Copper Conductors,
Hard, Medium-Hard, or Soft
ASTM B172-01 ...................... Standard Specification for Rope-Lay-Stranded Copper Conductors
Having Bunch- Stranded Members, for Electrical Conductors
ASTM B173-01 ...................... Standard Specification for Rope-Lay-Stranded Copper Conductors
Having Concentric-Stranded Members, for Electrical Conductors
ASTM B263-04 ...................... Standard Test Method for Determination of Cross-Sectional Area of
Stranded Conductors
ASTM B738-03 ...................... Standard Specification for Fine-Wire Bunch-Stranded and Rope-Lay
Bunch-Stranded Copper Conductors for Use as Electrical Conductors
GEIA-STD-0005-2 ................. Standard for Mitigating the Effects of Tin Whiskers in Aerospace and
High Performance Electronic Systems
IEEE Std. 315-1975 .............. Graphic Symbols for Electrical and Electronics Diagrams (Including
Reference Designation Letters)
IPC-2611 ............................... Generic Requirements for Electronic Product Documentation
IPC-OI-645 ............................ Standard for Visual Optical Inspection Aids
IPC-TM-650 ............................ IPC Test Methods Manual
IPC/WHMA-A-620 .................. Requirements and Acceptance for Cable and Wire Harness Assemblies
IPC/WHMA-A-620(SPACE) .. Space Applications Electronic Hardware Addendum to IPC/WHMA-A620
J-STD-001 ............................. Requirements for Soldered Electrical and Electronic Assemblies
J-STD-001(SPACE) .............. Space Applications Electronic Hardware Addendum to IPC J-STD-001
Requirements for Soldered Electrical and Electronic Assemblies
J-STD-004 ............................. Requirements for Soldering Fluxes
J-STD-006 ............................. Requirements for Electronic Grade Solder Alloys and Fluxed and NonFluxed Solid Solders for Electronic Soldering Applications
SAE ARP 6167 ...................... Etching of Fluoropolymer Insulations
2.3
FEDERAL
NASA PUBLICATION 1124 ... Outgassing
Data
for
(http://outgassing.nasa.gov)
Selecting
Spacecraft
Materials
NASA-STD-6001 ................... Flammability, Odor, Offgassing, and Compatibility Requirements and
Test Procedures for Materials in Environments That Support Combustion
NASA-STD-6016 ................... Standard Materials and Processes Requirements for Spacecraft
QQ-B-575 ............................... Braid, Wire Copper, Tin-Coated Tubular
2.4
MILITARY HANDBOOKS
MIL-HDBK-216 ....................... R. F. Transmission Lines and Fittings; cancelled 8 Sept 2001; no
replacement
MIL-HDBK-863 ....................... Handbook for Wiring Data and System Schematic Diagrams Preparation
of
2.5
MILITARY SPECIFICATIONS
MIL-A-46146 ......................... Adhesives-Sealants, Silicone, RTV, Noncorrosive (For Use With
Sensitive Metals and Equipment)
MIL-C-17 ................................ Cables, Radio-Frequency, Coaxial, Dual Coaxial, Twin Conductor, and
Twin Lead
MIL-C-27500 ........................... Cable, Electrical Shielded and Unshielded, Aerospace
MIL-C-39012 ........................... Connector, Coaxial, Radio-Frequency, General Specification for
MIL-DTL-17 ............................ Cables, Radio Frequency, Flexible and Semi-rigid, General Specification
for
MIL-DTL-5846 ........................ Chromel and Alumel Thermocouple Electrical Wire, Detail Specification
for
MIL-DTL-24308 ...................... Connectors, Electrical, Rectangular, Non-environmental, Miniature,
Polarized Shell, Rack and Panel, General Specification for
MIL-DTL-38999 ...................... Connectors, Electrical, Circular, Miniature, High Density, Quick
Disconnect, (Bayonet, Threaded, and Breech Coupling), Environmental
Resistant, Removable Crimp and Hermetic Solder Contacts, General
Specification for
MIL-DTL-81381 ...................... Wire, Electric, Polyimide-Insulated, Copper or Copper Alloy, General
Specification for
MIL-DTL-83723 ...................... Connectors, Electrical, (Circular, Environment Resisting), Receptacles
and Plugs, General Specification for
MIL-DTL-83733 ...................... Connectors, Electrical, Miniature, Rectangular Type Rack to Panel,
Environment Resisting, 200 Degrees C Total Continuous Operating
Temperature, General Specification for
MIL-I-631 ............................... Insulation, Electrical, Synthetic-Resin Composition, Non-Rigid
MIL-I-22129 ............................. Insulation Tubing, Electrical, Polytetrafluorethylene (PTFE) Resin, NonRigid
MIL-I-23053 ............................. Insulation Sleeving, Electrical, Heat Shrinkable, General Specification for
MIL-PRF-39012 ...................... Connectors, Coaxial, Radio Frequency, General Specification for
MIL-STD-202 ......................... Test Method Standard, Electronic and Electrical Component Parts
(Method 107, Test Condition B)
MIL-STD-704 ......................... Aircraft Electric Power Characteristics
MIL-T-43435 ............................ Tape, Impregnated, Lacing, and Tying
MIL-W-81044 ......................... Wire, Electric, Crosslinked Polyalkene, Crosslinked Alkane-imide
Polymer, or Polyarylene Insulated, Cooper or Cooper Alloy
MIL-W-83575 ......................... Military Specification Wiring Harness, Space Vehicle, Design and
Testing, General Specifications for – This is superseded by DOD-WW83575A (USAF)
MIL-W-22759 .......................... Wire, Electric, Fluoropolymer-Insulated Copper or Copper Alloy
2.6
REFERENCE
DOD-HDBK-83575 ................ General Handbook for Space Vehicle Wiring Harness Design and
Testing
NA-GSFC-2003-03 ................ NASA Goddard Advisory, Fluoropolymer Degradation Resulting in
Corrosion of Packaged Pre-wired Connector Assemblies
THIS PAGE IS INTENTIONALLY BLANK
3.
DESIGN PHILOSOPHY
Cables and wiring harnesses are equivalent to the
human circulatory and nervous system. They deliver
energy, transmit command and control instructions,
and collect and distribute sensory data describing not
only the environment external to the system, but the
health and status of the system itself.
Often the most overlooked, ignored, and “taken for
granted” component in a design, high quality cables
and wiring harnesses are essential to the
performance and reliability of any electrical /
electronic hardware.
Fig. 3.1
Wire, Cables, and Harnesses
It is the SUPPLIER’s responsibility to ensure that the
technical issues associated with the design and manufacture of cable assemblies and wiring harnesses
are conveyed to the USER, and that a dialogue is established, so that appropriate and timely decisions
are made commensurate with realistic expectations and reality. After all, it doesn’t matter how elegant or
innovative the design is if the cable assembly or wiring harness cannot be built, doesn’t fit, or won’t
perform as required during use.
3.1
GENERAL DESIGN REQUIREMENTS
The design of electrical wiring harnesses and cable assemblies shall [A1A2A3] be based on the worstcase operational requirements and expected use. These include, but are not limited to: assembly
processes; shipping and storage; installation; test; service environment (operational temperature limits,
mechanical, thermal, and vibration stress; contamination; corrosives; EMC/EMI/RFI, ionizing / nonionizing radiation, moisture or other fluid media exposure); post-use test and data recovery; and, life
expectancy.
Conditions that contribute to degradation of performance and/or reliability of hardware in service shall
[A1A2A3] require special consideration.
The basic design considerations to assure reliable interconnecting cable and wire assemblies include, but
are not limited to:
a. The physical and electrical properties of the wire and cable, including gauge/size; base metal;
coatings; strand count and construction (e.g.: rope-lay strand, bunch-lay strand, concentric-laystranded, Litz / woven, etc.); weight; tensile strength; current and voltage derating; conductivity and
signal propagation rates; etc.
b. The physical and electrical properties of the cable and harness assembly, including active and spare
wire count; connectors; EMI / RFI / magnetic shielding; ionizing / non-ionizing radiation; construction
(coaxial, discrete wire, hybrid, multi-conductor; optical fiber); redundancy; voltage drop; identification /
marking; etc.
c.
Material properties, including arc tracking resistance; chemical / material compatibility; flammability;
odor, outgassing; low-pressure / vacuum stability; ultra-violet stability; resistance / reactance to
corrosives, solvents, oxidizers, chemicals, etc.; resistance to heat / cold; resistance to abrasion
damage and cold flow; etc.
d. Application issues, including acoustic, mechanical, thermal shock; acceleration (g-load); environment
(condensing / corrosive / explosive atmosphere), electric field density (high voltage / lightning)
e. Non-metallic components - insulation jackets, potting materials, lacing tapes, braid sleeving, plastic
straps, wrap sleeving, and plastic tubing
f.
Special handling, storage, and processing requirements that may contribute to degradation of
performance and/or reliability of hardware in service (i.e.: Red Plague / White Plague control)
g. Foreign Object Debris (FOD)
h. Unique testing requirements
i.
Proprietary and export control
j.
Environmental / Regulated materials (e.g.: RoHS, REACH, etc.)
k.
Safety, maintainability, reliability, cost, etc.
3.1.1
END-PRODUCT REQUIREMENTS
3.1.1.1
PERFORMANCE AND RELIABILITY
The design shall [N1A2A3] assure that the overall performance and reliability requirements are met
under the most severe extremes of acceptance testing, storage, transportation, and operational
environments.
3.1.1.2
INTERCHANGEABILITY
Any two (2) or more wiring harnesses or cable assemblies bearing the same part number shall possess
such functional and physical characteristics as to be equivalent in performance, durability, and
connectivity; and, shall [A1A2A3] be capable of being changed, one for another, without alteration of the
items themselves or of adjoining items.
3.1.1.3
DESIGN FOR MAINTENANCE (DOM)
Cable and wiring harness assemblies shall [A1A2A3] be designed with features that contribute to the
ease and rapidity of maintenance without removal of other equipment, interconnections, wire bundles,
and / or fluid lines. All wiring shall [A1A2A3] be accessible, repairable, and replaceable at the
maintenance level specified by the USER.
a. Cable and wiring harness length should provide enough additional wire length for reworking the
entire connection at least one (1) time, at both ends of the wire. Conductors connecting contacts
within the same connector (i.e.: jumpers) shall [N1A2A3] be captivated or restrained (e.g.: cable
clamp, wire tie, lacing, sealing gland, etc.).
b. Access – When cable and wiring harness assemblies are required to be disconnected and/or
reconnected, the design shall [N1N2A3] incorporate sufficient flexibility, length, and protection to
permit disconnection and reconnection without damage to wiring or connectors.
c.
Ease of Connect / Disconnect - Electrical connections and cable installations should require no more
than one (1) operation to disconnect and reconnect without damage to wiring or connectors.
3.1.1.4
CABLE / HARNESS MANAGEMENT (ROUTING)
System reliability shall [A1A2A3] be a primary consideration in selecting the routing for wiring harnesses
or cable assemblies. Cables and harnesses should be routed along flat surfaces (either vertical or
horizontal) whenever possible, shall [A1A2A3] be properly supported and secured by cable clamps, and
shall not [A1A2A3] be routed near high electrical noise, magnetic, energy, thermal, or vibration sources.
The following shall [A1A2A3] be considered in the routing of cables and harnesses:
a. Provide accessibility for easy removal and replacement of attached equipment as well as the wire
harness.
b. Minimize flexing and handling of the harness during installation through small structural openings.
c.
Avoid interference with air ventilation flow patterns.
d. Prevent possible damage from fumes and fluids. The clearance between wires or cables and heat
generating devices should be such as to avoid deterioration of wires or cable from the heat
dissipated by the devices.
e. Provide slack lengths or maintenance loops sufficient for the mating / unmating of the connectors
after the component / hardware has been extracted from its installed location / position, unless
adequate internal access (physical and visual) is provided.
f.
Wiring installations where relative movement occurs (such as at hinges, rotating pieces, vibrationisolated hardware, etc.) shall [N1N2A3] be installed or protected in such manner as to prevent
deterioration of the wiring by the relative movement of the assembly parts. This deterioration includes
abrasion of one wire or cable upon another, cold flow, and excess twisting, bending, and pinching.
Cables and harnesses should be installed to twist instead of bend across hinges. Cables and
harness assemblies in the vicinity of equipment expected to be routinely serviced or replaced shall
[N1N2A3] be protected against damage caused by flexing, pulling, abrasion and other handling
stress.
g. Cables or wire harnesses crossing a moving or rotating interface shall not [N1N2A3] contain strainenergy elements to assist deployment. Where cables or wire harnesses cross a moving or rotating
interface, the installation drawings shall [N1N2A3] define dimensions including loop sizes and
distances to attachments. Attachment clamps shall [N1N2A3] be provided sufficiently close to any
loops so that movement into the path of motion of the moving mechanical assembly cannot occur
under any conditions.
h. Connectors shall [N1N2A3] be provided at each end of the loop to permit assembly and disassembly
without disturbing the harness configuration in the area of the interface.
i.
Cable and harness assemblies shall [N1N2A3] be routed so that they:
(1) Cannot be pinched by doors, lids, or slides.
(2) Will not be used as a translation device (i.e.: a hand hold, step, anchor point, etc.).
(3) Will not be bent sharply when connected or disconnected.
(4) Are readily accessible for inspection and repair.
(5) Do not infringe into the operational envelope nor constitute a safety hazard (i.e.:, sagging,
hooking, etc.).
(6) Are not external to the face of the equipment rack, unless otherwise required as an interface to
other equipment/enclosures.
3.1.1.5
ERGONOMIC DESIGN
Cables and wiring harnesses designed for use, or deployment, by humans shall [A1A2A3] be designed
to work with the human body in the intended environment and application.
3.1.1.6
SERVICE LIFE
Cables and wiring harnesses shall [A1A2A3] meet the design service life requirements specified in the
detail specification and/or contract.
3.1.2
ENVIRONMENT
Cables and wiring harnesses shall [A1A2A3] be capable of meeting the environmental design
requirements specified in the detail specification and/or contract.
3.1.3
STORAGE AND TRANSPORTABILITY
Cable / wire harness shall [A1A2A3] be packaged, handled, and transported in a manner that prevents
damage or environmental degradation.
3.1.4
WORKMANSHIP
All details of workmanship concerned with the fabrication and installation of cables and wiring harnesses
shall [A1A2A3] be controlled such that the finished item is of sufficient quality to ensure proper operation,
safety, reliability, and service life, and in compliance with IPC/WHMA-A-620 requirements.
4.
SELECTION OF PARTS, MATERIALS AND PROCESSES
Unless otherwise specified in the contract, the parts, materials, and processes shall [A1A2A3] be
selected and controlled in accordance with the approved Materials and Processes Plan / Requirements,
and specified on the drawing.
4.1
COMMONALITY
An additional objective in the selection of parts, materials, and processes should be to maximize
commonality and thereby minimize the variety of parts, related tools, and test equipment required in the
fabrication, installation, and maintenance of cables and wiring harness assemblies.
a. Whenever a selected specification provides more than one (1) characteristic or tolerance for an item,
the SUPPLIER shall [A1A2A3] use items of broadest characteristics in the equipment and of the
greatest allowable tolerances that will fulfill the performance and reliability requirements of the design.
b. When identical items of higher than minimum quality are readily available, the utilization of which
would not increase the life cycle costs, may be used.
c.
When maximum physical dimensions of an item are indicated in the selected specification for the
item, all new equipment shall [A1A2A3] be designed to accommodate the maximum physical size
specified, so that all parts having the same type designation will be physically interchangeable in the
hardware.
4.2
FLAMMABILITY
Insulation materials shall [A1A2A3] be non-combustible or self-extinguishing. Selection and use shall
[A1A2A3] be traceable to acceptable flammability test reports.
4.3
OUTGASSING
Collected Volatile Condensable Material (CVCM) outgassing of nonmetallic materials shall not [A1A2A3]
exceed Total Mass Loss (TML) specified by contract.
4.4
RESTRICTED MATERIALS / PROCESSES
All parts, materials, and processes shall [A1A2A3] be compatible with each other and have acceptable
life. See Appendix C “Restricted Materials / Processes” for technical guidance.
4.4.1
GLASS / GLASS-LIKE MATERIALS
Windows and other glass structures (e.g.: optics, instrument covers, etc.) that include any piece of glass
and other glass-like materials (e.g.: germanium, sapphire, etc.) shall not [A1A2A3] be used for Class 3
and Space products unless it is suitably contained or protected.
E/E components (e.g.: connectors, RF feed-through, diodes, components with glass-body seals, fiber
optic, etc.) that use glass as the component body, dielectric, wave guide, or hermetic seal are specifically
exempted from this requirement.
4.4.2
CRIMPING OF SOLDER-TINNED AND SOLID CONDUCTORS
Stranded wire shall [A1A2A3] be used for crimping. Designs requiring any of the following shall
[A1A2A3] detail the process and acceptance criteria on the engineering documentation and prior
approval from the User:
a. Crimping of solid wire
b. Crimping of solder-tinned stranded wire.
c.
Soldering of completed crimp terminations.
4.4.3
SPLICES
Splices shall not [N1N2A3] be used for Category IV (EED, Flight Termination System, etc.) cables. The
use of splices in a harness design should only be considered in the following design applications:
a. The routing of a dedicated, continuous, and unbroken conductor from point to point is not practical
b. The use of a connector is prohibited by contact under-utilization, weight, and/or size restrictions
c.
The use of a splice can optimize complicated wiring (i.e.: when the harness supports common branch
circuits or parallel-connected devices).
d. The use of a splice facilitates installation (i.e.: joining harness sections / branches).
Exception. The above is not applicable to shield terminations.
See 6.1.1 for requirements for use of splices.
4.4.4
CUPROUS OXIDE CORROSION (RED PLAGUE)
The use of silver-coated copper conductors (e.g.: wiring,
shielding, terminations, etc.) shall [N1A2A3] require the
implementation of a User-approved Red Plague Control Plan
(RPCP) to reduce and control exposure to environmental
conditions and contamination that promote the development of
cuprous oxide corrosion (Red Plague) and latent damage.
See Appendix B “Red Plague Control Plan (RPCP)” for
technical guidance.
Note:
[1.8].
Use of appendices must be separately invoked per
Figure 4.4.4
Red Plague (Cuprous Oxide Corrosion)
M22759/20-22-09
4.4.5
FLUORINE ATTACK (WHITE PLAGUE)
To reduce the risk of fluorine attack (White Plague), when
fluoropolymer-insulated silver-coated copper wiring is either
stored in sealed packaging (e.g.: vapor-proof bagging, MBB) or
used in enclosed environments / compartments, the fluorine
evolution rate shall not [N1A2A3] exceed 20 PPM when tested
in accordance with SAE AS4373 Method 608, Fluoride
Offgassing.
Figure 4.5
Fluorine Attack (White Plague)
M22759/43-24-96
4.4.6
LEAD-FREE TIN (<3% Pb) TECHNOLOGY – CONTROL LEVEL 2C
The use of lead-free Tin (Sn) technology in Class 3 and Space applications shall [N1A2A3] be prohibited
unless documented and controlled through a User-approved Lead Free Control Plan (LFCP) in
conformance with Control Level 2C requirements of GEIA-STD-0005-2, "Standard for Mitigating the
Effects of Tin Whiskers in Aerospace and High Performance Electronic Systems". The use of lead-free
Tin (Sn) technology in applications with exposure to temperatures at or below -30°C (-22°F) shall
[N1A2A3] be prohibited unless controlled through mitigation. See Appendix C “Restricted Materials /
Processes” and Appendix G “Lead-Free Control Plan (LFCP)” for technical guidance.
Note: Use of appendices must be separately invoked per [1.8]. <Chair: Synergy with IPC-A-640-081814>
4.5
TIME-CRITICAL OR LIMITED-LIFE
Completed cables, harness assemblies, and associated hardware shall [A1A2A3] have sufficient life
remaining to adequately support the design service life (3.1.1.6) requirement specified in the detail
specification and/or contract.
4.6
WIRE & CABLE
Wire and cable shall [A1A2A3] be of a type suitable for the intended application. Selection of wire and
cable shall [A1A2A3] take into account all requirements of this specification and the following design
considerations:
a. Conductor sizing, strand count, and construction
b. Conductor material and coating
c. Conductor count (individual insulated conductor, multi-conductor, coaxial, etc.)
d. Electrical characteristics (nominal and maximum voltage, allowable voltage drop, steady-state and
intermittent current load, derating, frequency)
e. Temperature (operational and storage)
f. Mechanical (tensile strength, vibration, flexure, etc.)
g. Insulation (dielectric rating, abrasion / cold-flow / cut-through resistance, arc-tracking resistance,
flammability / smoke rating, outgassing, ionizing / non-ionizing radiation resistance, etc.)
h. Outgassing
i. Shielding (EMI / RFI, EMP, magnetic)
j. Pressure / partial-pressure / vacuum requirements
k. Aging effects
l. Extreme environments (corrosive, Severe Wind and Moisture Problem - SWAMP areas, fluid /
moisture contact / submersion, etc.)
m. Limitations on weight, size, and cost
4.6.1
CONDUCTOR SIZING
Wire and cable shall [A1A2A3] be selected so that the rated maximum conductor temperature is not
exceeded for any combination of loading (amperage, power factor, voltage drop), ambient temperature,
dielectric withstanding voltage (DWV), and heating effects of bundles, conduit, and other enclosures.
a. Data / Signal / Instrumentation. The size of individual wires shall [N1N2A3] be a minimum of 22
AWG. Copper / Coated Copper wire or cable shall [A1A2A3] be made of soft annealed copper (22
AWG or larger), high-strength copper alloy (24 AWG to 28 AWG), or beryllium-copper alloy (30 AWG
or smaller).
b. Power Distribution. The size of individual wires or cable used in power distribution circuits shall
[A1A2A3] be a minimum of 18 AWG, and sized to ensure that, when under maximum current load,
the voltage at the load equipment terminals is within the limits of MIL-STD-704, or USER
specification.
c.
Thermistor. Thermistor wire sizes smaller than 24 AWG may be considered for use in applications
where the wiring is stress relieved and adhesively bonded to structure.
d. Magnetic Survey. Nickel, nickel-coated copper, and high-strength copper alloy (HSC) shall
[N1N2A3] be subjected to a magnetic survey if project requirements indicate a design sensitivity to
magnetic interference.
e. Derating. See 5.1 for conductor derating requirements.
4.6.2
CONDUCTOR MATERIAL AND COATING
a. Copper / Copper Alloy. The conventional conductor material for electrical wiring has been soft,
annealed, uncoated copper. Uncoated copper / copper alloy has an upper temperature limitation of
150°C (302°F), and shall [N1N2A3] only be considered for general wiring applications where the
end-use environment would not cause failures.
(1) Copper / copper-alloy wire may be terminated by solder or crimp processes.
(2) Copper / copper-alloy wire is susceptible to oxidation and corrosion.
(3) In applications where the weight is an overriding factor, with resistance a secondary concern, a
high-strength copper alloy is available. High-strength copper alloy also provides increased
flexure life.
(4) The number of flexures that pure copper wire can withstand without work hardening or breaking is
severely limited.
b. Tin-Coated Copper. Tin, the most common and least expensive coating used in electronic wiring, has
an upper temperature limitation of 150°C (302°F), and should be considered for use in low frequency
circuits.
(1) Tin-coated copper wire may be terminated by solder or crimp process
(2) Tin-coated copper wire is prone to oxidation and metallic whisker issues.
c.
Silver-Coated Copper. Silver-coated copper, or silver-coated copper alloy has an upper temperature
limitation of 200°C (392°F), and should be considered for wiring carrying high frequency circuits.
(1) Silver-coated wire may be terminated by solder or crimp processes.
(2) Due to potential fire hazard, silver-coated conductors shall not [A1A2A3] be used in areas
where they are subject to contamination by ethylene glycol solutions.
(3) Silver-coated wire is susceptible to cuprous oxide corrosion (Red Plague) when produced, stored,
or used in a moist or high humidity environment. Use of silver-coated copper or silver-coated
copper alloy shall [N1N2A3] require use of a Red Plague Control Plan (RPCP). See 4.4 and
Appendix B.
d. Nickel / Nickel-Coated Copper. Nickel and nickel-coated copper has an upper temperature limitation
of 260°C (500°F), and should be considered for use in low frequency circuits (i.e.: dc and ac power
circuits) and corrosive / wet environments.
(1) Due to the difficulty of soldering nickel and its typical use in high temperature, corrosive and wet
applications, this wiring should be terminated by crimp process.
(2) Nickel wire can be soldered, provided that high temperature soldering equipment and active
fluxes are used.
(3) Nickel and nickel-coated copper shall [N1N2A3] be subjected to a magnetic survey if project
requirements indicate a design sensitivity to magnetic interference.
e. Aluminum. The use of aluminum wire (including copper-clad variants) shall [N1N2A3] require prior
USER approval. Aluminum wire shall [N1N2A3] be terminated using processes and materials
specifically designed for this application.
f.
Solid conductors. The use of solid conductor in wiring harness design shall [N1N2A3] require prior
USER approval.
4.6.3
MULTI-CONDUCTOR CABLES
Because multi-conductor cables are made up of individually-insulated wires, the limitations of the cable as
a system shall [A1A2A3] be considered, using the selection criteria outlined in 4.6.
4.6.4
COAXIAL CABLES
The design of coaxial cable and coaxial cable assemblies shall [A1A2A3] be based on the worst-case
operational requirements and expected use. For applications above 400 MHz and in critical RF circuits,
critical electrical characteristics such as attenuation, capacitance, structural return loss, environmental
requirements, short leads and grounding shall [A1A2A3] be considered in design.
Coaxial cable shall [A1A2A3] be in accordance with MIL-DTL-17H. MIL-HDBK-216 should be used as a
guide for the selection of coaxial cable.
4.6.5
OPTICAL FIBER, OPTICAL FIBER CABLE, AND OPTICAL FIBER ASSEMBLIES
The design of optical fiber, optical fiber cable, and
optical fiber assemblies shall [A1A2A3] be based on
the worst-case operational requirements and
expected use. These include, but are not limited to:
assembly processes; shipping and storage;
installation; test; service environment (operational
temperature limits, mechanical, thermal, and vibration
stress; contamination; corrosives; ionizing / nonionizing radiation, moisture or other fluid media
exposure); post-use test and data recovery; and, life
expectancy. Conditions that contribute to degradation
Fig. 4.7
of performance and/or reliability of hardware in
Fiber Optic Cable
service shall [A1A2A3] require special consideration.
4.7
CONNECTORS
Connectors used in the fabrication of wire harnesses and cable assemblies shall [A1A2A3] be suitable
for the application; designed and approved for mating and demating in the expected operating
environment, under the maximum voltage and current loads being carried, without producing electrical
arcs that will damage connector contacts; ignite surrounding materials or vapors; or, expose the USER to
electrical shock or injury.
a. Equipment, wire harnesses, and connectors shall [A1A2A3] be designed such that blind connections
or disconnections (e.g., connectors that will be hidden from sight during mate/demate) are not
required to be made during installation, operation, removal, or maintenance unless the design
includes scoop-proof or other protective features, and maintains grounding during mating/demating.
b. Connector Pins/Sockets. The powered (live / hot) side of a connector pair shall [A1A2A3] be
terminated in sockets, rather than pins; and, recessed to prevent electrical arcs that will damage
connector contacts; ignite surrounding materials or vapors; or, expose the USER to electrical shock
or injury.
c.
Metal-shell Connectors. Metal-shell connectors shall [A1A2A3] have a grounded backshell, when
grounding is required for EMI considerations and when such grounding will not result in unacceptable
ground loops.
d.
Connectors to be used in an EMP or High level RF environment shall [A1A2A3] be capable of
incorporating RF finger stock at the connector-receptacle interface to provide for shield continuity and
shall [A1A2A3] be mechanically capable of being subjected to the coupling nut torque.
e. Connectors that are not self-locking, and which are used in high vibration, mechanical shock, or
thermal-cycling environments, shall [A1A2A3] be capable of being safety wired, staked, or locked
with thread adhesive.
(1) Adhesives / doping / staking compounds shall [A1A2A3] be compliant with flammability and
outgassing requirements.
(2) Safety wire shall not [A1A2A3] be used in applications where the connector is frequently mated /
demated during normal operations, where cutting the safety wire may create an unacceptable
metallic FOD concern, or where the safety wires present a sharp edge, puncture, snagging or
injury concern to operating personnel.
f.
High Voltage. Circuits carrying potentials in excess of 200VAC RMS, or 300VDC through critical
pressure environments shall [N1N2A3] be terminated in single-contact, high voltage connectors. If
the design requires that high voltage circuits be terminated in multi-contact connectors, contacts shall
[N1N2A3] be selected which are the most distant from ground potentials. Shielded wire should not
be used in high voltage circuits unless required by special designs.
High voltage connectors shall [A1A2A3] be kept free of any contamination which would decrease the
voltage flashover threshold.
g. High Power. Connector interfaces categorized as high-power shall [N1N2A3] have one verifiable
upstream inhibit which removes voltage from the connector prior to mate / demate. The design shall
[N1N2A3] provide for verification of the inhibit status.
Note: For purposes of this document, high-power connector interfaces are those that do not limit the
short circuit outputs to 16 W or less, or have an open-circuit output voltage of greater than 32 V.
h. Micro-D Connectors. Micro-D size connectors shall not [N1A2A3] be used for Category IV (EED,
Flight Termination System, etc.) cables, unless approved by the User.
i.
Torque. When torque of connector hardware (e.g.: threaded backshells, strain relief, etc.) is required
by design, it shall [A1A2A3] be specified on the drawing.
4.7.1
MATING PROVISIONS
Electrical connectors, plugs, and receptacles shall [A1A2A3] be designed to prevent incorrect
connection with other accessible connectors, plugs, or receptacles; pin damage; and/or, inadvertent pin
connections due to misalignment.
a. The selection of the technique used shall [A1A2A3] be:
(1) Use of physical constraints (i.e.: bends, differing branch lengths, etc.) built into a cable or harness
that locate similar connectors so they cannot be interchanged.
(2) Selection of different contact count, contact pattern, shell size, or connector types (e.g.: round,
square/rectangular, D-sub, etc.) of connectors to be located adjacent to each other.
(3) Selection of alternative polarization, keying, colors, electrical interlock / confidence loop circuits,
and/or clocking of adjacent, similar connectors only if this requirement cannot be met with either
method (1) or (2) above.
b. The following techniques shall [A1A2A3] only be employed when the above techniques are not
practical by design:
(1) Permanent identification of mating connectors provided on each side of each connector pair.
(2) Unique labels on each end of the cable / harness assembly identifying the connector name /
number and mating connections.
(3) A label located approximately in the center of the cable / harness assembly length identifying
cable / harness assembly name / number and purpose.
c.
Test connectors should comply with the above requirements when mated with product connectors.
d. Blind mating of connectors. Blind-mated connectors shall [A1A2A3] have design features (e.g.:
guide pins, keying, float, or other means of connector alignment) to ensure correct alignment and
mating.
4.7.2
MOISTURE PROTECTION
When electrical connectors and wiring junctions to connectors are to be exposed to a condensing
environment they shall [N1N2A3] be protected from moisture by methods which are demonstrated by
test or analysis to provide adequate protection to prevent open and short circuits or a harmful unintended
conductive current path.
This requirement shall [N1N2A3] include test conditions (except for
environmental test articles) and all operating conditions.
4.7.3
PIN ASSIGNMENT
Electrical circuits shall not [N1A2A3] be routed through adjacent pins of an electrical connector if a short
circuit between them would constitute a single failure that would cause injury to the USER; cause
emission of arcs, sparks, molten metal; cause ignition of surrounding materials or vapors; cause loss or
degradation of a critical system, or result in violation of electrical creepage or clearance distance
requirements.
When allowable by connector design:
a. Signal assignments shall [N1A2A3] be designated such that contacts are utilized from the center of
the connector out leaving any unused contacts at the outer most position(s).
b. Critical signals shall [N1A2A3] be assigned to the inner most contacts.
c.
Leads of twisted pairs shall [N1A2A3] be assigned to contacts that are next to each other.
d. Connectors shall [N1A2A3] be chosen to allow for 10% spare contacts.
4.7.4
PROTECTION OF CONNECTORS
Unmated connectors shall [N1N2A3] be individually protected from contamination and/or damage by
protective materials (e.g.: covers, caps, wrap, etc.). Materials selected shall not [A1A2A3] damage or
degrade the electrical or mechanical integrity of the connector.
4.7.5
PROTECTION OF SEVERED ELECTRICAL CIRCUITS
Cables and harness assemblies which are to be severed in the normal course of operation (e.g., vehicle
separation) shall [N1N2A3] be protected against short circuiting or compromising other circuits during the
remaining phases of the mission by dead-facing to remove all voltages.
Note: For purposes of this standard, the term “severed” is defined as permanently separated by cutting
conductors using guillotine devices or separating mated connectors using a lanyard device.
5
ELECTRICAL REQUIREMENTS
The electrical characteristics required for interconnecting wiring are the first considerations to be
established in designing cables and wiring harnesses. In particular, the cable / wire type required
depends upon the circuit category, circuit count, maximum operating voltage, current capacity, frequency
response, and expected environmental / operational stresses.
5.1
DERATING
Degradation of conductors when exposed to environmental conditions shall [N1A2A3] be taken into
account in the selection and application of wiring and cable.
a. The selection of wire size shall [A1A2A3] be based upon circuit current and cable size in accordance
with the derating requirements of SAE AS50881 paragraph 3.8.8.1, thermal math model, USER
specification, or Table 5.1 - Derating.
b. Electrical Wire Current Carrying Capacity. Wires shall [A1A2A3] be of such cross section as to
provide ample and safe current carrying capacity. The maximum design current in any wire shall
[A1A2A3] be limited so that "wire total temperature" will never exceed the rated wire temperature or
the touch temperature (see 5.1.d).
c.
Voltage Drop. The total impedance of wires and ground return paths shall [A1A2A3] be such that
the maximum voltage drop between the power supply bus and the load does not exceed the limits
under maximum continuous load conditions. For power distribution circuits, the wire or cable shall
[A1A2A3] be sized to ensure that, when under maximum current load, the voltage at the load
equipment terminals is within the limits of MIL-STD-704 or USER specification.
d. Touch Temperature. Wire harnesses and cable assemblies shall [A1A2A3] be designed to preclude
exposure to surface temperatures that can cause injury. The following defines the recommended
temperature limits for normally exposed surfaces that would not cause injury for the stated condition.
(1) Maximum of 45C (113F) for continuous contact (more than 30 seconds)
(2) Maximum of 49C (120F) for incidental contact (less than 30 seconds)
(3) Minimum of 4C (39F) for continuous contact (more than 30 seconds)
(4) Minimum of -18C (0F) for incidental contact (less than 30 seconds)
e. Contact / Connector Current Ratings. The continuous current ratings of Table 5.1 were derived only
for wire and cable applications, and shall not [A1A2A3] be applied to wire termination devices (e.g.,
connectors, contacts, lugs, etc). Contact / connector current ratings are limited by the design
characteristics (e.g.: materials of construction, plating, thermal mass, etc.) of the termination device
and the installation configuration (e.g.: cable mount versus bulkhead mount, etc.). Care shall
[A1A2A3] be taken to ensure that continuous current thermal loading does not damage or degrade
the contact / connector and lead to premature failure (e.g.: fractured contact body, loss of dielectric
strength, loss of mechanical integrity, etc.). Acceptable temperature levels of contact / connector
components shall [A1A2A3] be those defined by the component and/or USER specification.
5.2
CORONA SUPPRESSION
Installed cable and wiring harness assemblies susceptible to corona shall [A1A2A3] be designed such
that detrimental corona discharge will not occur under any operating conditions. Test(s) or analysis shall
[A1A2A3] be performed to demonstrate that the cable and wiring harness assemblies will remain
protected for the design service life of the hardware (See 3.1.1.6).
Note: For purposes of this standard, the term "corona" is defined as an electrical discharge caused by
ionization of gas in the vicinity of an energized conductor. Ionization can occur on the surface of an
insulated or uninsulated conductor, as well as in voids and cracks within the insulation jacket.
5.3
CIRCUIT CATEGORIES
The five major categories and the various subcategories of circuits are defined in the following
subparagraphs and summarized in Table 5.3. Each circuit in each wiring harness or cable assembly
shall [N1N2A3] be categorized in accordance with these definitions.
5.3.1
CATEGORY I (POWER AND CONTROL)
Includes (a) DC circuits over 10V; (b) DC circuits below 10V and over 5 A; (c) AC circuits below 0.1 MHz
with voltages above 25 Vrms; and, (d) pulse circuits with maximum voltages above 25V with rise and fall
times greater than 1 microsecond.
5.3.2
CATEGORY II (HIGH LEVEL SIGNALS)
Includes (a) digital circuits with voltage levels from 5 to 25V maximum and rise and fall times greater than
1 microsecond; (b) digital circuits with maximum voltage levels from 1V to 10V and rise and fall times less
than 1 microsecond; (c) AC circuits below 0.1 MHz with voltages between 5V and 25V, and (d) AC circuits
between 0.1 MHz and 1.0 MHz with voltage levels between 1V to 10V and rise or fall times less than 1
microsecond; (c) AC circuits below 0.1 MHz with voltages between 5V and 25V; and, (d) AC circuits
between 0.1 MHz and 1.0 MHz with voltage levels between 1V and 10V.
5.3.3
CATEGORY III (LOW-LEVEL SIGNALS)
Includes (a) DC circuits below 10V and less than 5A; (b) AC circuits between 0.1 MHz and 1.0 MHz with
voltage levels less than 1V; (c) AC circuits below 0.1 MHz with voltages less than 5V; (d) digital circuits
with maximum voltages less than 1V with rise times less than 1 microsecond; and, (e) digital circuits with
maximum voltages less than 5V and rise and fall times greater than 1 microsecond.
5.3.4
CATEGORY IV (ELECTRO EXPLOSIVE DEVICE CIRCUITS)
Includes all electro explosive device (EED) circuits.
5.3.5
CATEGORY V (HIGH-FREQUENCY SIGNALS)
Includes (a) all AC circuits above 1 MHz; (b) high level digital circuits with maximum voltages above 10V
and with rise or fall times less than 1 microsecond; and, (c) AC circuits between 0.1 MHz and 1.0 MHz
with voltages levels above 10 V.
5.4
SHIELDING (BY CIRCUIT CATEGORY)
When specified, shielding by circuit category shall [A1A2A3] be provided as indicated in the following
sub-paragraphs. All shielding shall [A1A2A3] be insulated to prevent uncontrolled grounding / ground
loops.
5.4.1
CATEGORY I CIRCUITS
Wiring for category I circuits shall [A1A2A3] have the power or signal wire(s) twisted with the return wire.
The wiring may be unshielded.
5.4.2
CATEGORY II CIRCUITS
Wiring for category II circuits shall [A1A2A3] have twisted signal and return wires with each pair, or
circuit, shielded.
5.4.3
CATEGORY III CIRCUITS
a. Wiring for category IIIa shall [A1A2A3] have twisted signal and return wires, and be shielded as a
group from category IIIb and other categories.
b. Wiring for category IIIb shall [A1A2A3] have twisted signal and return wires with each pair, or circuit,
shielded.
c.
Wiring for category IIIc shall [A1A2A3] have twisted signal and return wires, and be shielded as a
group from category IIIa, IIIb, and other categories.
d. Wiring for category IIId and category IIIe shall [A1A2A3] have twisted signal and return wires with
each pair, or circuit, shielded.
5.4.4
CATEGORY IV CIRCUITS
Wiring shall [A1A2A3] be twisted pairs, each pair shielded. with multipoint grounding of shields at source
and load. The method of shield termination shall [A1A2A3] be via full-peripheral (360 degree)
termination at all connector backshells. Wiring for Electro-Explosive (EED) / Bridge Wire Activated
Device (BWAD) circuits shall [A1A2A3] be double-shielded.
5.4.5
CATEGORY V CIRCUITS
Wiring interconnections, other than waveguide, shall [A1A2A3] be shielded coaxial cable, balanced
shielded cable, or balanced cabled with a characteristic impedance of 100 ohms or less.
5.4.6
ADDITIONAL SHIELDING
Shielding shall [N1N2A3] be added over that specified for the category of each circuit to provide
additional protection against conducted or radiated electrical noise / interference.
a. Coax or balanced shielded cable may be used instead of twisted shielded pairs, particularly in
applications where capacitance-per-meter is critical.
b. Shielding shall [N1N2A3] be added over that specified for the category of each to the extent required
when an electromagnetic pulse (EMP) environment is specified.
c.
Shielded circuits may be routed together in a common bundle with a secondary (overbraid) shield,
provided the close proximity of each circuit in the bundle does not increase conducted or radiated
electrical noise in any individual circuit in the bundle.
5.5
BONDING
Electrical bonding designs shall [A1A2A3] prevent electrical current from flowing in ground references,
except under fault conditions. Cable and harness assemblies (which include the electrical wiring and
connectors, tie and protective materials and installation hardware) shall [A1A2A3] be designed and
routed such that adequate protection is afforded per applicable shielding and EMI/RFI/EMC criteria. See
Table 5.5.
a. Electrical bonds, particularly those intended to be semi-permanent or permanent, shall [N1N2A3] be
sealed to mitigate the intrusion of moisture, corrosion, or oxidation into the mating surfaces.
b. Bonds which are intended to be opened and re-connected during planned or contingency
maintenance shall [N1N2A3] be designed to accommodate re-establishing an acceptable bond using
techniques and materials that are suitable for the application and the environment.
c.
Harness shields external to the equipment, requiring grounding at the equipment, shall [N1N2A3]
have provisions for grounding the shields to the equipment chassis through the harness connector
backshell. Equipment or element internal secondary power supplies and signal and shield networks
may utilize those grounding techniques most appropriate for the application as long as the isolation
specified above is maintained.
d. Class L (Lightning) bonds shall not [A1A2A3] be terminated by solder process.
Notes:
1. Bonding is designed to ensure USER safety, proper operation of electrical fault avoidance / detection
systems, and electromagnetic interference reduction by establishing a minimum series impedance
path between the electrical equipment and the ground plane.
2. A ground is used to establish a zero signal reference for any equipment or other item required to be
grounded.
5.6
SHIELD DESIGN AND GROUNDING
Shielding shall [A1A2A3] provide maximum EMI/RFI coverage in the intended application and
environment, with a minimum cover limit of 85 percent, or as specified by USER.
a. Metal braid shielding shall [N1N2A3] either be woven directly over a core or obtained in prebraided
form (woven tubing) and installed by sliding it over the wire bundle.
(1) Copper or silver-coated copper round-wire or flat braid should be considered for wiring subjected
to operating environments below +200°C (+392°F), and in environments with high frequency
electrical noise. Silver-coated copper braid must be protected from cuprous/cupric oxide
corrosion (Red Plague) and contact with glycol solutions (fire risk).
(2) Nickel and nickel-coated copper should be considered for applications where the wire is expected
to be exposed to temperatures up to +260°C, long duration elevated temperature applications,
water, or corrosives. Nickel / nickel-coated wire may also be slightly magnetic, making use in
some sensitive applications unacceptable.
(3) Copper-clad steel, stainless steel, or nickel braid should be considered for use as an over-braid
shielding material.
b. Multiple-point shield grounding shall [A1A2A3] be used on high-frequency circuits (above 0.1 MHz),
on digital circuits with rise or fall times less than 1 microseconds, and on all Category IV circuits.
c.
Single and shield grounding shall be maintained on all other circuits, expect that when multiple
shields are used to prevent induced interference, the outer shield shall [A1A2A3] be multipoint
grounded.
d. When single and shield grounding is used to protect a circuit against induced radiation, the ground
shall [A1A2A3] be at the receiver or high impedance end.
e. When single and shield grounding is used to minimize radiation from a circuit, the ground shall
[A1A2A3] be at the signal source end.
5.6.1
ELECTROMAGNETIC PULSE (EMP) ENVIRONMENT
Shielding shall [A1A2A3] be added over that specified for the category of each to the extent required
when an electromagnetic pulse (EMP) environment is specified. Shielded circuits may be routed together
in a common bundle with a secondary (overbraid) shield, provided the close proximity of each circuit in
the bundle does not increase conducted or radiated electrical noise in any individual circuit in the bundle.
a. Wire shields in all categories shall [A1A2A3] be bonded around the circumference (360 degrees),
and preferably within the backshell of the connectors.
b. Inner shields that are designed to be ungrounded at one end shall [A1A2A3] be insulated from
adjacent shields, the grounded and floating ends terminated within their respective connector shell(s),
and the floating end insulated and secured against fraying and shorting.
c.
Ungrounded inner shield terminations (floating shields) shall [A1A2A3] be insulated from the
connector pins, the backshell of the connector, and from adjacent shields.
5.6.2
CATEGORY IV CIRCUITS
Wire shields in category IV circuits (EEDS) shall [A1A2A3] be bonded around the circumference, and
preferably within the backshell of the connectors.
a. Circuits such as pyrotechnic event instrumentation circuits that make a direct connection to the
electro explosive device circuit shall [A1A2A3] employ shields which are bonded around the
circumference (360 degrees), and preferably with the backshell at the pyro junction or relay box
connector.
b. If an EMP environment is not specified, the shield ground at the other instrumentation circuit
connector may be grounded through a pigtail to a pin in the connector or directly to the structure.
5.6.3
CATEGORY I, II, III, AND V CIRCUITS (NO EMP)
Wire shields in these categories of circuits that require grounding and are not subjected to an EMP
environment, shall [A1A2A3] be grounded to chassis / reference ground by the shortest feasible route.
5.6.4
UNGROUNDED / FLOATING SHIELD TERMINATIONS (NO EMP)
Wire shield terminations that are to be ungrounded, and are not subjected to an EMP environment, shall
[A1A2A3] be secured against fraying and insulated from the back shell of the connector and from
adjacent shields.
5.6.5
MAGNETIC SHIELDS
Magnetic shields (i.e.: mu-metal) shall [A1A2A3] be electrically isolated from the EMI/RFI and over-braid
shields (if specified) by protective insulation overwrap / separator over the length of the cable / harness
assembly and mechanically and electrically connected to the chassis / structure, either by:
a. pig-tail / ground-lead to a chassis-mounted bonding post
b. through the connector backshell at the source end of the cable / harness assembly.
5.7
CIRCUIT ISOLATION
Interconnect wiring in each of the five categories shall [A1A2A3] be isolated from wiring in other
categories by maintaining, to the extent practicable, a minimum separation of 30 mm (1.18 in.) between
wires and wire bundles of the different circuit categories. When wires from different circuit categories use
the same connector, the pin assignments and layout shall [A1A2A3] stress isolation between different
categories, and grounded spare pins shall [A1A2A3] be utilized to provide circuit separation.
a. Category IV circuits (electro-explosive devices) shall [A1A2A3] maintain a minimum distance of 30
mm from other category circuits and shall not [A1A2A3] share the same connector with other
category circuits.
b. High impedance circuits above 1000 ohms, or sensitive circuits, below 5 V, shall [A1A2A3] be
isolated by routing or shielding or both from other circuits even in the same category.
c.
Antenna cables shall [A1A2A3] be separated from each other and from other wiring.
d. Wiring to redundant subsystems or equipment shall [A1A2A3] be run in separate harnesses or cable
assemblies to prevent damage to one subsystem affecting the other.
e. Safety ground wire (if specified) shall [A1A2A3] be routed through the connector to the chassis /
structure.
f.
EMI/RFI and over-braid shields (if specified) shall [A1A2A3] be mechanically and electrically
connected to the chassis / structure, either by pig-tail / ground-lead to chassis-mounted bonding post
or through the connector backshell(s).
g. EMI/RFI and over-braid shield circuits shall not [A1A2A3] be routed through connector contacts,
unless specifically specified by drawing.
h. Current shall not [A1A2A3] intentionally flow through the shield(s) or chassis / structure.
5.7.1
GROUP-GROUNDING OF INDIVIDUAL SHIELD TERMINATIONS
When grounding wires of individual cable shields are grounded to one point, they shall [A1A2A3] be
spliced to a common bond grounding wire.
a. No more than four (4) shield conductors, plus one (1) common bond wire, shall [A1A2A3] be
terminated in one splice.
b. The common bond wire shall [A1A2A3] be derated for the combined maximum short circuit / fault
current of the shielded circuits.
c.
For ordinary RFI/EMI protection, the shield shall [A1A2A3] be terminated within 100mm (4 inches) of
the center conductor termination for the x-distance, and the combined length of shield grounding
wires shall not [A1A2A3] exceed 190mm (7.5 inches). See Fig. 5.7.1.
d. For interference sensitive circuits, the shield shall [A1A2A3] be terminated within 20 mm (0.75 in.) of
the center conductor termination, and the combined length of shield grounding wires shall not
[A1A2A3] exceed 115mm (4.5 in.). When this does not provide adequate isolation, RFI/EMI
connector backshells may be necessary.
5.7.2
SEPARATION OF REDUNDANT SYSTEMS
In cases where wiring redundancy is a requirement, separate cable bundles / wiring harnesses shall
[A1A2A3] be formed to prevent damage to one subsystem from affecting the other. This requirement is
not applicable to cable and wiring harness assemblies installed in common enclosures within a redundant
system, sub-system, or sub-system element (i.e.: redundant redundancy is not required.).
a. Cable and wiring harness assemblies of redundant systems, redundant sub-systems, or redundant
major elements of sub-systems, having different circuit classifications or redundancy codes and
routed in the same area, shall not [A1A2A3] be commonly bundled or routed in the same wire
bundle, but may be routed through a common connector if a 20 dB coupling margin is maintained.
b. Verification. Cable and wiring harness assemblies shall [A1A2A3] be designed to permit verification
of redundant functions or operational modes any time the system, subsystem, or equipment requires
testing prior to use.
c.
Coding. Each bundle shall [A1A2A3] be coded with a bundle code which is the same as the circuit
classification of the circuits which it contains.
d. Classification. Each bundle classification shall [A1A2A3] be designated on drawings in which the
bundle appears, and coded with the circuit classification code, plus a numeric designator code to
identify the redundancy classification.
DERATING
Table 5.1
Environmental Conditions
Atmospheric / Non-vacuum (≥ 4.3PSIA)
Vacuum (< 4.3PSIA)
Wire Size
(AWG)
Maximum Nominal Allowed Single Wire
Current (Isw), (amps)
(94) 1/, 3/, 5/, 6/, 7/
Maximum Nominal Allowed Single Wire
Current (Isw), (amps)
(94) 1/, 2/, 3/, 4/
26
3.8
3.4
24
5.4
4.7
22
7.4
6.5
20
10.0
8.8
18
13.2
11.6
16
15.0
13.3
14
20.0
18.0
12
29.0
25.0
10
40.0
34.8
8
63.0
56.0
6
92.0
80.0
4
120.0
110.0
2
170.5
150.0
1/0
260.0
220.5
NOTES:
1/ When wire is bundled, the maximum design current for each individual wire shall be derated according to the following:
For N < 15
For N > 15
IBW = ISW x (29 - N)/28
IBW = (0.5) x ISW
Where:
N = number of wires
IBW = current, bundle wire
ISW = current, single wire
2/
These currents are for wires in a vacuum at 94°C (200°F) ambient.
3/
Deratings listed are for wire rated for 200°C maximum temperature. Derating factors for lower temperature rated wire
shall be as follows:
a. For 150°C wire, use 65% of value shown in vacuum column, and 80% of value shown in non-vacuum column.
b. For 135°C wire, use 45% of value shown in vacuum column, and 75% of value shown in non-vacuum column.
c. For 105°C wire, do not use this wire in vacuum environments, and use 65% of value shown in non-vacuum column.
4/
Maximum wire temperature for the maximum single wire current is 147°C (295°F).
5/
These currents are for ambient (room temperature) conditions: +22°C (72°F), per IPC-TM-650 [1.3].
1/
Maximum wire temperature for the maximum single wire current 118°C (242°F).
Table 5.3
Circuit Character
Direct Current (DC)
Alternating Current (AC)
< 0.1 MHz
Alternating Current (AC)
0.1 MHz to 1 MHz
Alternating Current (AC)
> 1 MHz
Pulse with rise or fall time
> 1 microsecond
Pulse with rise or fall time
< 1 microsecond
Electro-explosive (EED)
Bridge Wire Activated
Device (BWAD)
Summary of Circuit Categories and Shielding Requirements
Signal Level
Volts (V) or Amperes (A)
Category
< 10 V and < 5 A
IIIa
Shielded as a group from other
categories
< 10 V and > 5A
Ib
None
≥ 10 V
Ia
None
< 5V RMS
IIIc
Shielded as a group from other
categories
5V to 25 V RMS
IIc
Each pair shielded
> 25 V RMS
Ic
None
< 1 V RMS
IIIb
Each pair shielded
1 V to 10 V RMS
IId
Each pair shielded
> 10 V RMS
Vc
Coax or balanced shielded
Cable
All
Va
Wave guide, coax, or balanced
shielded cable
< 5 V peak
IIIe
Each pair shielded
5V to 25V peak
IIa
Each pair shielded
> 25V peak
Id
None
< 1 V peak
IIId
Each pair shielded
1 V to 10 V peak
IIb
Each pair shielded
> 10 V peak
Vb
Coax or balanced shielded cable
All
IV
Each pair double-shielded
Shielding
TABLE 5.5
CLASS
BOND CLASSIFICATION
FUNCTION
DESIGN REQUIREMENT
C
POWER CURRENT RETURN PATH (C) - Applies to electrical All circuit and systems that use the hardware chassis / structure for a
systems / designs where the hardware chassis / structure is used as power return path shall satisfy Class C bonding requirements.
the power current return.
• Bonding resistance requirement: Rmax = VIRmax / Imax
• Used in small, self-contained systems / packages.
Maximum allowable circuit resistance (Rmax) is determined by
• NOT RECOMMENDED FOR NEW DESIGN. A dedicated power
maximum supply current at maximum allowable voltage drop, and
return circuit path (wire) is preferred over the use of hardware
includes the wire, connectors, and all structural bond joints in the
chassis / structure for power current return in large, complex, recircuit return path.
configurable, and distributed systems.
• Design Max. Voltage Drop (VIR): <3.5%
(28V system = ≤ 1V; 120V system = ≤ 4V)
• Permanent jumpers and straps acceptable.
• Cable / harness shields and/or connector shells shall not be used
as the power return path.
• Requires mechanically secure bonds with low circuit impedance to
assure adequate circuit power and to minimize circuit voltage drop.
Improper assembly / unsecured bonds can result in loss of power,
structural damage / galvanic corrosion, unintentional heating,
EMC/EMI, fire, ground faults, or shock hazards to personnel.
All cable and harness assemblies that use the shield as the fault
current return path shall satisfy Class H bonding requirements.
H
SHOCK AND FAULT PROTECTION (H) - Applies to electrical
systems / designs where a dedicated circuit path (wire) is employed
for power current return,
• Protects against fault currents, due to a short circuit between a
power wire and a metallic component or other conductive
structure, that may cause electrical shock to personnel or fire
hazards.
LIGHTNING PROTECTION (L) - Applies to electrical systems /
designs that would carry surge current resulting from a direct or
indirect lightning strike.
• Bonding components are required to withstand high current
without arcing.
• Bond strap / conductor terminations must withstand high resistive
heating effects and intense magnetic forces during current pulse.
All cable and harness assemblies that could carry lightning current
shall be completely enclosed in overbraid shields with a
circumferential 360 degree termination into bulkhead penetrations,
connectors, or connector backshells to satisfy Class L bonding
requirements.
• Class L bond paths, and the joints in that path, shall have low
resistance and adequate contact area to carry its share of lightning
current without sustaining a burning, melting, distorting, or other
heating effect due to the long duration, high-current portion of the
lightning strike.
L
•
Bonding resistance requirement: ≤ 0.1 ohm (≤ 0.1 Ω)
•
•
Design fault current: 500% overload current , 0.5 sec.
Jumpers and straps acceptable.
•
•
R
S
Bonding resistance requirement: ≤2.5 milliohm (≤2.5mΩ) at
200,000A (<500 volts) across any joint.
Low inductance required. Bond strap / conductor terminations
shall not be soldered.
ELECTROMAGNETIC OR RADIO FREQUENCY (R) - Applies to
equipment that could generate, retransmit, or be susceptible to radio
frequency (RF) interference. Includes antenna mounts and cable
shield connections. Provides a uniform low impedance path for all
electrical equipment at radio frequencies (RF).
• Protects equipment from RF emissions.
• Direct contact preferred. No jumpers.
• Short, wide strap may be used as last resort.
All Class R bond paths to structure, and the joints in that path, shall
be designed such that the inductance and overall impedance,
including resonances, are low enough to prevent interference at the
frequencies of interest, Z=R + iωL.
• Bonding resistance requirement: ≤ 2.5 milliohms (≤ 2.5mΩ)
• Electrical connectors and their backshells used to terminate cable
shields shall be installed to provide a low impedance path from the
backshell to the equipment case: ≤ 2.5 milliohms.
• Antennas that require low impedance to the ground plane for
proper operation shall meet Class R requirements.
• Bond straps should be flat with length to width ratio less than 5:1
ELECTROSTATIC CHARGE (S) - Applies to conducting items,
except active antenna elements, which are subject to precipitation
static effects, triboelectric charging effects, fluid flow, air flow, plasma
charging, separation of elements, and/or other charge generating
mechanisms.
• Protects against electrostatic discharge (ESD).
• Applies to any item subject to electrostatic charging.
• Allows moderate impedance.
All cable and harness assemblies that could accumulate a surface
electrostatic charge of sufficient amplitude to damage interconnected
hardware / electrical systems shall satisfy Class S bonding
requirements.
•
Bonding resistance requirement: ≤1.0 ohm (≤1 Ω)
•
A mechanically secure and continuous electrical bond path that
maintains specified dc resistance across the connection after
exposure to shock, vibration, thermal loads, and other expected
mechanical movement.
≤ 1 Ohm: Conducting Structural Items (>100cm2)
≤1000 Ohm: Conductive Mechanical Subassemblies / Parts
(>100cm2)
≤ 1000 Ohm: Non-metallic / Composite Structural Items
Jumpers and straps acceptable.
•
•
•
•
Notes:
1. Low frequency bonds allow use of straps and jumpers.
2. High frequency bonds require low inductance paths. Short straps are sometimes acceptable.
3. High current bonds require large cross sectional areas.
4. Low current bonds allow use of small contact areas.
5. Hazardous Area Bonding - All conductive items in areas where flammable materials, gases, or vapors may be present shall have (at a minimum) a Class S
electrical bond not to exceed 1.0 ohm.
6
ASSEMBLY / FABRICATION REQUIREMENTS
Wiring shall [A1A2A3] be assembled into interconnecting cables or harnesses using fabrication methods
and assembly techniques that assure the production of high quality interconnecting cables and
harnesses.
6.1
WIRE TERMINATIONS
Wire terminations to connectors or terminals shall [A1A2A3] be compliant with the termination
technology (i.e.: crimp terminations to crimp contacts, solder terminations to solder contacts, insulation
displacement terminations to IDC contacts, etc.) of the connector / terminal.
a. Not more than one wire (conductor) shall [A1A2A3] be terminated to any single contact of
environmentally sealed connectors.
b. For lug-type terminations, the harness design shall [A1A2A3] be such that the maximum number of
lugs to be connected to any one screw termination on a terminal board shall [A1A2A3] be four (4) for
ring type lugs, or two (2) for spade type lugs, unless the terminal board was designed to
accommodate more than the specified number of terminations.
c.
Screw type terminals should be torqued to engineering specification.
d. Smaller wire in crimp contact. For a smaller wire into a larger contact, it is permissible to fold the
copper conductor once and crimp per the folded CMA into a larger contact or to utilize equivalent filler
wire. The resultant CMA of the doubled / filler wire shall [A1A2A3] be within the CMA range of the
crimp contact.
6.1.1
SPLICES (USE OF)
When splices are used in accordance with [4.9.2], the following is applicable:
a. The splice termination shall not [A1A2A3] be located in a flexure zone or in breakout / branch areas.
b. Splices shall [A1A2A3] be provided with acceptable stress relief, and be protected from abrasion,
cold flow, cut through, flexure, vibration, chafing, flexing, and sharp edges.
c.
For applications involving the mass splicing of conductors in a harness, the splices shall [N1N2A3]
be staggered along the length of the harness to minimize the final cross-sectional profile.
d. Splices shall [A1A2A3] be completed with conductors that are properly sized to safely accommodate
the power load expected, at the recommended derating.
e. The completed splice termination and any exposed metallization shall [N1N2A3] be over-sleeved
with heat shrink tubing / sleeving per IPC/WHMA-A-620.
f.
The cable / harness materials shall [A1A2A3] be chosen to allow for any additional width of the cable
/ harness bundle to ensure minimal stress at the joined area. The drawing shall [N1N2A3] designate
the size of any fill-wire / material required to assemble the splice.
Examples of splices demonstrated to be acceptable for high-reliability and space flight applications
designs are listed in Table 6.1.1. It is the engineer’s responsibility to choose the splice most suitable to a
specific application.
6.1.2
DEAD-ENDING
Undesignated / unterminated (i.e.: spare) wires shall [N1N2A3] be dead-ended with AS25274 caps or
with insulation sleeving in compliance with IPC/WHAM-A-620, and in a manner acceptable to the USER.
Dead-ending shall [N1N2A3] be located within 101-152 mm [4-6 in.] of connectors, breakouts, or
bulkhead feed-through bushings. Dead-ending shall not [N1D2D3] be located under mounting clamps or
cable identification labels.
TABLE 6.1.1
Splice Description
TYPES OF SPLICES
Classification
Termination Method
Assembly
Difficulty
Level
Crimp
Discrete
Solder
Solder
Sleeve
Butt
Mechanical
Easy
X
End
Mechanical
Easy
X
Lap
Non-Mechanical
Easy
X
X
Lash
Mechanical
Moderate
X
X
Modified Pin Terminal (MTP)
Mechanical
Moderate
X
Parallel
Mechanical
Moderate
X
Jiffy Junction
Mechanical
Easy
X
Western Union / Lineman
Mechanical
Difficult
X
X
6.1.3
INSULATION COMPATIBILITY WITH SEALING AND SERVICING
Wiring termination devices designed to provide an environment-resistant joint, shall [N1N2A3] be
chemically compatible with the wiring insulation, and have sealing features (e.g.: elastomer grommet,
cable gland, etc.) compliant with the insulation construction.
a. When the diameter of the wire is smaller than the minimum allowable diameter, a length of shrink
AMS-DTL-23053/5 Class 1 & 3, /8, /11, /12 Class 3, 4, & 5, or /18 Class 2 & 3 sleeving shall
[N1N2A3] be installed in back of the contact and shall [N1N2A3] protrude through the environmental
seal a minimum of two (2) insulated wire diameters.
b. Elastomer grommets are generally qualified to seal on wires and electrical/optical cables having
smooth extruded insulations. Only one wire/optical cable per grommet hole shall [N1N2A3] be
permitted.
c.
The sealing of grommets on tape wrapped, braided, striped, or other than smooth circular insulations
shall [N1A2A3] be demonstrated in the qualification of the terminating device.
d. Post Installation. After installation into the hardware, the integrity of the sealing features of all such
devices shall [N1N2A3] be intact, and able to perform their function. A device shall [N1N2A3] be
considered as sealed if the outermost sealing feature (web) is in full contact with the device when
visually inspected.
e. Routing and installation design shall [N1N2A3] ensure there will be no transverse (angular) loading
that will degrade or compromise the integrity of the sealing feature.
Note: For technical guidance on wire to connector sealing grommet compatibility see SAE AIR1329,
“Compatibility of Electrical Connectors and Wiring”.
6.2
FORM LAYOUT FIXTURE
A full-sized, three-dimensional (3-D) form layout fixture should be provided for all complex
interconnecting cables and harnesses to ensure proper routing, wire lengths, connector configurations,
support requirements, and access requirements of the wiring harnesses. The form layout fixture may be
limited to partial installations which contain the more complex wiring harnesses.
6.3
FORMING WIRES INTO CABLES AND HARNESSES
Spacing dimensions for spot tie, plastic strap, and stitch lacing for trunk, branches, and breakouts shall
[N1A2A3] be at increments that maintain the bundle’s desired form in accordance with IPC/WHMA-A620.
a. Ties shall [A1A2A3] be spaced at intervals required to maintain bundle configuration.
b. Spot ties shall [A1A2A3] consist of a clove hitch followed by a surgeon’s square knot or other nonslip knot.
c.
Spot tie ends shall [A1A2A3] be trimmed.
d. When knots are staked or spot tie ends are required to be treated to prevent fraying, the necessary
adhesive / doping / staking compounds, as well as any special design requirements, shall [A1A2A3]
be specified on the engineering documentation. Adhesive / doping / staking compounds shall
[A1A2A3] be compliant with flammability and outgassing requirements.
6.4
WIRE LAY
Harness assemblies consisting of more than four (4) discrete wires or cables that are expected to be
flexed during use or connector mating / demating operations shall [N1N2A3] be fabricated with a
unidirectional or helical wire twist (lay), with the direction of twist (lay) either right or left to produce an
essentially circular cross section for that portion of the wire harness or cable assembly that is subject to
movement.
Engineering documentation shall [N1A2A3] identify locations where harness assemblies consisting of
more than four (4) discrete wires or cables are expected to be flexed during use or connector mating /
demating operations and shall [N1A2A3] document the method to be used to provide the flexure (e.g, a
unidirectional or helical wire twist (lay) to produce an essentially circular cross section for that portion of
the wire harness or cable assembly that is subject to movement).
Wires that are twisted as supplied, such as twisted wire pairs or triplets, shall [N1A2A3] be treated as a
single cable (do not untwist).
a. Twisted Pair. When constructing twisted pairs or triplets by the twisting of single conductors is
specified by engineering drawings, the twist operation should produce a uniform twist pattern. The
single conductors defined for twisting by the engineering drawing shall [N1N2A3] be twisted at a
uniform rate of twist throughout the length of the harness or the length of the signal run in the harness
(i.e., from connector to connector, to splice, etc....).
b. Parallel or Straight Wire Lay. When unidirectional or helical wire twist (lay) is not required, a wiring
harness or cable assembly may be fabricated with a parallel or straight wire lay, by laying the discrete
wires / cables parallel to each other with minimal cross-over, for that portion of the wiring harness or
cable assembly which is permanently installed, and which is not subject to movement after
installation.
c.
Harness assemblies requiring preformed bends using this assembly technique shall [N1N2A3] be
constructed on a 3-D form board. Minimum bend radius requirements shall [N1N2A3] be observed
when constructing preformed bends.
6.5
BEND RADIUS
The bend radius for wires, cables, and harness assemblies shall [A1A2A3] conform to IPC/WHMA-A620, Table 14-1. For fiber optic cable, see IPC-A-610DC, Table 16-1.
6.6
PROTECTION AND SUPPORT
Installed wiring harnesses and cable assemblies shall [A1A2A3] be protected and supported in
accordance with IPC/WHMA-A-620. Support devices specified by the engineering drawing (i.e.: cable
clamps, etc.) shall hold the wiring harnesses and cable assemblies in place without deforming or
damaging the wire or cable insulation, or without causing undue mechanical strain on the connections.
a. Main Bundle Support. The main bundle shall [A1A2A3] be secured within two harness diameters
(2d) of the emergence of the breakout from the main bundle, within two harness diameters (2d)
following the emergence of the breakout, and at intervals not to exceed 24 inches.
b. Breakout Support. Breakouts shall [A1A2A3] be long enough to provide proper support at
installation. Breakouts shall [A1A2A3] be secured by connector backshells or clamps as close to the
connector as practical but shall not [A1A2A3] violate stress relief.
c.
Cable Support Material. The cable support material shall [A1A2A3] be compatible with the cable
material (e,g,, no chemical reaction between the materials).
6.7
ETCHING FLUOROPOLYMER-INSULATED ELECTRICAL WIRE
Designs requiring the development of a mechanical bond and/or environmental seal to fluoropolymerinsulated / coated electrical wire or cable shall [N1N2A3] require the portion of the wire or cable to be
wetted to be etched prior to application of adhesive / polymer.
a. Applicable:
Polytetrafluoroethylene
(PTFE/TFE),
fluorinated-ethylene-propylene
(FEP),
perfluoroalkoxy copolymer (PFA), Polyvinylidene Flouride (PVDF/PVF2), and EthyleneTetrafluoroethylene (ETFE), Ethylene Chlorotrifluoroethylene (ECTFE)
b. Not applicable: Cross-Linked Ethylene-Tetrafluoroethylene (XL-ETFE)
c.
Wet processing (chemical etching) shall [N1N2A3] be per SAE ARP6167, “Etching of Fluoropolymer
Insulations”.
d. Etched surfaces shall [N1A2A3] be processed within 24 hours, or packaged per SAE ARP6167.
e. Etched surfaces packaged per SAE ARP6167shall [N1N2A3] be processed within two (2) years.
f.
Potting shall [N1N2A3] be accomplished within 1 year of etching, provided the etched wires have
been protected from ultraviolet light and contamination.
g. When etching of wire insulation is required to provide satisfactory bonding to potting materials, the
end of the wire to be stripped and terminated shall not [N1A2A3] be exposed to the etchant. The
preferred process is to form the wire into a U-shape, immersing only the bent portion in the etchant
with the open end of the wire above the etchant level. The un-etched end of the wire shall not
[N1A2A3] be cut off prior to neutralization of the etchant.
6.8
IDENTIFICATION AND MARKING
When the identification, isolation, modification, and repair of interconnecting wires, electrical / optical
cables, wire harnesses is required, the identification coding, marking methods, materials, and
location/spacing shall [A1A2A3] be specified.
a. The identification code shall [A1A2A3] be printed to read horizontally from left to right or vertically
from top to bottom. The characters shall [A1A2A3] be legible and permanent and the method of
identification shall not [A1A2A3] impair the electrical or mechanical characteristics of the wiring.
b. Hot Stamping. Hot Stamping processes that reduce the insulation thickness below minimum
requirements, reduce dielectric strength, or which reduce environmental protection or structural
integrity shall not [A1A2A3] be used. Hot stamping shall not [A1A2A3] be used for optical cable.
c.
Exceptions:
(1) Individual wires or cables in a jacketed or shielded-jacketed cable.
(2) Internal Wiring. Color coding or physical marking of individual conductors used in internal wiring
of electronic equipment is not required.
6.8.1
CABLE AND HARNESS ASSEMBLIES
Each cable and harness assembly shall [N1A2A3] be permanently marked with a unique identification
code identifying the cable / harness assembly, per the detailed wire and cable specification.
a. The identification code should be printed to read horizontally from left to right or vertically from top to
bottom. The characters shall [N1A2A3] be legible and permanent and the method of identification
shall not [N1A2A3] impair the electrical or mechanical characteristics of the wiring.
b. When it is not possible to print directly upon a cable / harness assembly, an identification marker (i.e.:
heat shrinkable sleeving, tape, etc.) should be used. The marker shall not [N1A2A3] be used as an
electrical insulating device or clamp locator mark.
c.
For repairable, protected harnesses, the marker shall [N1A2A3] be visible during maintenance within
the accessible area at the rear of the connector.
d. Hot stamp marking shall not [N1A2A3] be used for wire used in aerospace applications.
6.8.2
OPTICAL CABLE
Optical cable shall [A1A2A3] be uniquely color-coded to facilitate identification and marked with a printed
legend to identify the quantities and types of fibers within the cable (e.g.: 12 Fiber 8 x 50/125, 4 x
62.5/125). The outer cable jacket may be any color specified by the USER, but the de facto industry
standard, per TIA/EIA-598 is:
• Orange for multi-mode (MM)
• Yellow for single-mode (SM)
6.8.3
COAXIAL CABLE
Coaxial cable shall [A1A2A3] be identified by a colored marker (1 inch nominal width) at intervals not
greater than 24 inches of length and within 6 inches of termination. Unless specified by the User, the
color of the marker shall be solid violet (VIO, 7) in accordance with EIA RS-359.
6.8.4
CONNECTORS
Each connector shall [N1A2A3] be identified by a permanent label / marking on the connector body or
affixed to the cable adjacent to the connector, identifying both the connector and mating receptacle.
The identification device / marker may be placed directly on the connector or on the cable / harness
assembly within 15 cm [6 in.] of the connector. In all cases, the identification device shall [N1A2A3] be
of a material, either as applied or with the aid of a protective overcoat (i.e.: tape, clear shrink tubing, etc.),
that will resist damage or degradation that would obscure or make the identification information illegible.
a. The identification code should be printed to read horizontally from left to right or vertically from top to
bottom. The characters shall [N1A2A3] be legible and permanent and the method of identification
shall not [N1A2A3] impair the electrical or mechanical characteristics of the wiring.
b. All plugs shall [N1A2A3] be identified with a “P” designation.
c.
Mating connectors / receptacles shall [N1A2A3] be Identified with a “J” designation.
d. All bulkhead / structure mounted receptacles shall [N1A2A3] be Identified with a “J” number on both
sides of the structure, adjacent to the receptacle.
e. Receptacles, such as test and power, to which a mating plug is not normally attached, shall
[N1A2A3] have, in addition, the function of the receptacle identified on the plug side of the structure.
6.8.5
CLAMP LOCATING MARKS
Marking tape used to position and locate harnesses and cables may be either permanent or temporary in
nature. Permanent type marking tapes shall [A1A2A3] be specified on the engineering drawing and
meet M&P and environmental requirements.
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7
QUALITY ASSURANCE REQUIREMENTS
7.1
RESPONSIBILITY FOR INSPECTIONS AND TESTS
Unless otherwise specified in the contract, the SUPPLIER shall [A1A2A3] be responsible for the
performance of all inspections and test requirements as specified in IPC/WHMA-A-620 and IPC/WHMA-A620 (SPACE). The SUPPLIER may use their own facility, or any other facilities for the performance of the
inspection and test requirements specified herein, unless disapproved by the USER, or as otherwise
specified in the contract.
7.2
CLASSIFICATION OF INSPECTIONS AND TESTS
The tests and inspections specified herein are classified as follows:
a. Parts, materials, and process controls
b. Physical configuration audit
c.
Acceptance tests
d. Qualification tests
7.3
WORKMANSHIP, ACCEPTANCE, AND TESTING
Workmanship, acceptance, and testing shall [A1A2A3] be specified to conform to the Product
Classification specified in 1.2 and IPC/WHMA-A-620. Any deviation from, or additions to, the default
requirements contained within IPC/WHMA-A-620 shall [A1A2A3] be noted on the drawing. Electrical test
potentials shall not [A1A2A3] exceed the dielectric and/or current rating of the most sensitive component
in the cable / harness assembly.
Post Installation. After installation into the hardware, the integrity of the sealing features of all such
devices shall [N1N2A3] be intact, and able to perform their function. A device shall [N1N2A3] be
considered as sealed if the outermost sealing feature (web) is in full contact with the device when visually
inspected.
7.4
QUALIFICATION
When required by contract, cable and wiring harness qualification may be partially or totally satisfied by
qualification of higher levels of assembly that include the cable / wire harness.
a.
Qualification tests shall [A1A2A3] be conducted to approved test plans that indicate what tests and
test procedures will be conducted at what levels of assembly.
b. Applications having constraints on allowable outgassing shall [A1A2A3] qualify to that requirement
either by test, or by an analysis using applicable materials test data to determine the estimated total
mass loss and the estimated loss of volatile condensable materials for each wiring harness during its
service life.
c.
Applications of harnesses that cross moving or rotating interfaces shall include harness stiffness
measurements and fatigue testing that may be appropriate. These tests and measurements shall
[A1A2A3] be conducted under the case dimensional conditions, with maximum motion, at ambient
conditions as well as under worst case design environmental conditions.
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8
DOCUMENTATION
Effective communication between the design and manufacturing functions is the most important element
in managing the development and maintenance of any electronic product, whether it is designed and built
by a company that is vertically integrated (all functions under the same organization) or if the product is
being outsourced to one or multiple suppliers each of which provides a particular function or service in the
development, manufacture or maintenance of the product. The degree of detail and clarity will determine
the success or failure of all the factors that make up the life cycle of the end product.
The documentation package may consist of multiple pieces of information (data) that fully describe the
characteristics and functional performance requirements of the hardware to which the documentation
pertains. This package may include functional and schematic diagrams, assembly descriptions,
fabrication data (master drawing), wire lists, test requirements, specification performance control
documents, and material identification descriptions / Bills of Materials (BOMs).
Since the stages of manufacture vary, and different industry contributors need different information, the
completeness of any data set should be predicated on need and updated accordingly. The revision
methodology of any data set should follow proven concepts of Configuration Management and Control,
thereby ensuring that there is no ambiguity as to the meaning or effectivity of information or requirements
at any point during the development, design, and assembly cycles.
8.1
DATA
The preparation of the documentation package shall [A1A2A3] be in accordance with IPC-2611, MILHDBK-863, or USER-approved format, or an equivalent format agreed upon by the SUPPLIER and
USER.
a. Straight-line Format. When practical, each wire harness or cable assembly should be presented on
a separate sheet, and in a straight line (elementary) format.
b. Connection Lists. Connection lists shall [A1A2A3] list all modules / assemblies to which the cable /
harness assembly is connected and identify each connection and attached wiring.
c.
Critical Circuit Wiring. Circuit functions that may be affected by wire length, routing, direction,
bundling, bend radii, etc., shall [N1A2A3] be identified as critical.
d. Marking and Identification. To facilitate installation and servicing, each wiring harness or cable
assembly and each connector shall [N1A2A3] be identified and physically marked with:
(1) its reference designation,
(2) the reference designation of its mating connector,
(3) the drawing part number, and
(4) a unique serial number at the time of fabrication, when specified by the USER.
The method and location of the physical identification shall [A1A2A3] assure legibility when installed
and shall not [A1A2A3] impair the functional characteristics of the wire harness or cable assembly.
e. Symbols. Symbols that define items on a drawing shall [A1A2A3] be consistently used.
Recommended symbols include:
(1) Circle - item number
(2) Square - Note reference
(3) Vertical Triangle – Operation
(4) The initials “INT” surrounded by a rectangle – Interface dimensions.
8.2
CONNECTOR ORIENTATION (CLOCKING)
Unless specified otherwise, the connector shall [N1N2A3] be depicted with the connector mating key or
keyway at position 12, with a clocking tolerance of + 15 degrees. Angle type cable clamps shall
[N1N2A3] be depicted at position 6 (pointing downward) as shown in Figure 8.2.
8.3
CONNECTOR PIN-OUT
Unless specified otherwise on the approved
drawing, the connector pin-out shall
[N1N2A3] be depicted as the mating face
view.
8.4
DIMENSIONING AND TOLERANCE
Unless specified otherwise on the approved drawing, the following shall [N1N2A3] apply:
a. Datum. Wire harness dimensions, including location of breakout points, bends, etc., shall [N1N2A3]
be measured from the connector or terminator face at one end of the wire harness (DATUM).
b. Wire Harness Length. Wire harness length shall [N1N2A3] be measured from the DATUM to the
final termination (i.e. connector face, terminals, splice, etc.).
c.
Breakout Length. Breakout length shall [N1N2A3] be referenced from the approximate center-line of
the wire harness at the breakout point to its final termination (i.e. connector face, terminals, splice,
etc.).
d. Tolerance. Cable length measurement tolerance shall be as specified in IPC/WHMA-A-620, Table
11-1 “Cable Length Measurement Tolerance”, unless otherwise on the drawing / documentation. If
the engineering drawing has multiple dimensions called out between a connector and termination,
breakout, or overall length, the tolerances shall [N1N2A3] be considered noncumulative and will be
applied to the sum of the dimensions (entire length to the termination point), not each individual
dimension.
<use graphic from A-620>.
9
TAILORING
This specification is intended for use in equipment specifications or contracts to incorporate those
requirements which are common to most wiring harnesses. The requirements stated in the specification
are a composite of those that have been found to be cost effective for high reliability applications. This
document establishes the minimum requirements for most applications.
Where possible, the requirements are stated in ways that are self-tailored to each application.
For example, the EMP requirements are not imposed by this specification unless an EMP environment is
indicated by some other compliance document, or contract. Nevertheless, all requirements of this
specification shall [A1A2A3] be evaluated for each application and those that are not appropriate, or
clearly increase program life cycle costs, shall [A1A2A3] be excluded or changed.
Suppliers are encouraged to identify to the USER, any requirements imposed by this document that are
believed to be excessive or not applicable to the design and intended use. However, Suppliers are
reminded that deviations from contractually imposed requirements can be granted only by the
USER.
Tailoring of shielding requirements should be based upon electromagnetic compatibility analysis or tests
for particular applications. Because of the similarity of requirements, this specification may be used to
specify requirements for interconnecting cables and wiring harnesses for use in the three general endproduct classes established by the IPC (Class 1-2-3), as well as aviation, military, and spaceflight
applications .
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10
DEFINITIONS AND ACRONYMS
For purposes of this document, the following additional acronyms, abbreviations, and terms are listed in
addition to those listed in IPC-T-50, “Terms and Definitions for Interconnecting and Packaging Electronic
Circuits”. Specialized definitions and acronyms related to “Red Plague” are listed in Appendix B.
10.1
DEFINITIONS
Accessories
Mechanical devices, such as cable clamps or backshells, added to
connector bodies.
Adapter
An intermediate device to provide for attaching special accessories or
to provide special mounting means.
Ambient (laboratory /test)
Temperature: 15°C to 35°C [59°F to 95°F]
Relative Humidity (RH): 35% to 75%
Ambient (normal / room)
Temperature: 22°C±3°C [72°F±5°F]
Relative Humidity (RH): 50%±10%
Barrel (Contact Wire Barrel)
The section of contact that accommodates the stripped conductor.
Bend Radius
The radius of a formed bend, either temporary or permanent,
measured in multiples of cross-sectional diameters, to which a
component lead, conductor, cable (metallic, fiber, hybrid), harness
(metallic, fiber, hybrid), optical fiber, or wire, can be bent without
inducing permanent damage or reduction in performance, power, or
reliability.
Bend Radius, Long-term
The radius of a formed bend in a component lead, conductor, cable
(metallic, fiber, hybrid), harness (metallic, fiber, hybrid), optical fiber, or
wire, in the permanently installed configuration.
Bend Radius, Short-term
The radius of a formed bend in a component lead, conductor, cable
(metallic, fiber, hybrid), harness (metallic, fiber, hybrid), optical fiber, or
wire, during assembly, installation, or storage.
Bonding, Electrical
The process by which a low impedance path for the flow of an electric
current is established between two metallic objects.
Bubble Pack
A laminated plastic sheet that is formed with patterned air entrapment
("bubbles"). The bubbles provide excellent cushioning for anything
enclosed between layers of the material.
Cable, Biaxial (twin-lead)
An engineered wiring product, consisting of two individually insulated
50Ω coaxial cables, bonded together to resemble a lamp or speaker
wire.
Cable, Coaxial
An engineered wiring product, typically supplied in the form of a central
solid or stranded conductor insulated by a dielectric material, held in
concentric orientation to a conductive tubing or braided sheathing that
serves both as an EMI/RFI shield and as a return circuit path. Coaxial
systems are available in different technologies, ranging from flexible,
insulated cable, formable, and semi-rigid metallic sheathed.
Cable, Coaxial, Flexible
Flexible coaxial cable is constructed of a central solid or stranded
conductor surrounded by a flexible low loss r-f dielectric core material,
which holds the inner conductor in concentric orientation to a braided
metal outer conductor(s), and covered by a protective outer jacket /
covering.
Cable, Coaxial, Formable /
Hand-formable
Formable / hand-formable coaxial cables are constructed of a central
solid conductor surrounded by a flexible low-loss r-f dielectric core
material, which holds the inner conductor in concentric orientation to a
tin-dipped and fused metallic braid as the outer conductor. This offers
the advantage of being capable of being bent and formed without the
use of tools or bending jigs, while providing the electrical signal
performance of semi-rigid coaxial.
Cable, Coaxial, Semi-rigid
Semi-rigid, coaxial cables are constructed of a central solid conductor
surrounded by a flexible low-loss r-f dielectric core material, which
holds the inner conductor in concentric orientation to a solid,
continuous, metal outer conductor (tube).
Cable, Flat
An engineered wiring product, consisting of two or more individually
insulated, round or flat solid conductors that are mechanically bonded
in a parallel alignment, to a flat insulating base material to form a
planar composite construction.
Cable, Fiber Optic
A cable containing one or more optical fibers (see figure below). The
optical fiber elements are typically individually coated with polymer
layers and contained in a protective tube suitable for the environment
where the cable will be deployed.
Cable, Hybrid
An engineered wiring product consisting of two or more wiring
technologies (i.e.: multi-conductor, coaxial, and / or fiber optic) bound
together by an overall insulation jacket (unshielded); or, bound and
wrapped with an overall metallic covering (braid or foil), and covered
by an overall insulation jacket (shielded).
Cable, Multiconductor
An engineered wiring product, typically constructed of two (2) or more
individually insulated conductors, bound together by an overall
insulation jacket (unshielded); or, bound and wrapped with an overall
metallic covering (braid or foil), and covered by an overall insulation
jacket (shielded).
Cable, Shielded
An engineered wiring product consisting of one or more insulated
conductors, wrapped with an overall metallic covering (braid or foil),
and covered by an outer insulation jacket.
Connector, Backshell
The rear portion of a connector assembly, designed to provide
environmental protection (i.e.: dirt, moisture, EMI, etc.) and
accommodations (physical space) to provide stress relief to the wire
terminations. Most backshell designs include an integral clamping
device to mechanically secure the cable / wire harness to the
connector.
Connector, Body
The main portion of a connector assembly to which contacts and other
accessories are attached.
Connector, Grommet
An elastomeric seal used on the cable side of a connector body to seal
the connector against contamination and to provide stress relief.
Connector, Contact Insert
The part of a connector that holds the contacts in position and
electrically insulates them from each other and the shell.
Contact, Insertable/Removable A contact that can be mechanically joined to or removed from a
connector contact insert. Usually, special tools are used to insert (lock)
the contact into place or to remove it.
Contact, Pin
Male-type contact designed to slip inside a socket contact.
Contact, Socket
A female-type contact designed to slip over a pin contact.
Contaminant
An impurity or foreign substance present in a material that affects one
or more properties of the material. A contaminant may be either ionic
or nonionic.
An ionic, or polar compound, forms free ions when dissolved in water,
making the water a more conductive path.
A nonionic substance does not form free ions, nor increase the water's
conductivity. Ionic contaminants are usually processing residue such
as flux activators, finger prints, and etching or plating salts.
Crimp
The physical compression (deformation) of a contact barrel around a
conductor to make an electrical and mechanical connection to the
conductor.
Crimping
A method of mechanically compressing or securing a terminal, splice,
or contact to a conductor.
Critical Pressure Environment
The localized environment created by a combination of environmental
factors, such as contamination (foreign gasses, dust particles, oxides
and salts, and outgassing products), gas pressure, and temperature at
which a destructive corona discharge becomes an issue, as defined by
Paschen’s Law. In an air environment, this may occur at voltages
greater than 190V (RMS) at gas pressures less than 50 Torr (0.06 atm)
Design Authority
For purposes of this document, the Supplier is considered the Design
Authority. (See Section 1)
Lay
The twist (helical) pattern of wire stands in a stranded wire, insulated
wires in a cable, or insulated wires and cables in a harness assembly.
Length of lay
The axial length of one complete turn of the wiring helix.
Offgassing
The release of a volatile part(s) from a substance when placed in a
vacuum environment.
Qualification
The test process that proves the design, manufacturing, and assembly
of the hardware and software complies with the design requirements.
Radiofrequency (RF)
The frequency spectrum from 15 kHz to 100 GHz. Cables are seldom
used above 18 GHz.
Radiofrequency Interference
(RFI)
Electromagnetic radiation in the radiofrequency spectrum from 15 kHz
to 100 GHz.
Red Plague (Cu2O).
The sacrificial corrosion of copper in a galvanic interface comprised of
silver and copper, resulting in the formation of red cuprous oxide
(Cu2O) and black cupric oxide (CuO). Risk of developing Red Plague
in silver-plated copper wiring is relatively low, if the wire has a nonporous silver plating with a uniform plating thickness of at least 2 µm (
0.078 mil), and is stored in a humidity-controlled environment.
Typical MTTF: 15 – 25 years
Scoop-proof (connector)
A physical design feature where the connector's long shell prevents
inadvertent angular cocking of the mating plug connector into the
mating receptacle. This feature prevents physical damage to the pins
and connector shell, reducing the possibility of electrical shorting.
In the event of connector "mismates," scoop-proofing will also preclude
the inadvertent partial electrical mating of differently keyed connectors.
Solder Sleeve
A heat-shrinkable solder termination device with meltable sealing
preforms at ends.
Splice (v)
The joining of two or more conductors to each other.
Stranded Conductor
A conductor composed of a group of smaller wires.
Tin Pest (a.k.a.: Tin Disease /
Tin Plague)
The progressively destructive and irreversible allotropic transformation
of pure tin from an electrically conductive metal (a.k.a.: beta-tin / β-tin),
to a crumbly, white, non-metallic, non-conductive powder (a.k.a.:
alpha-tin / α-tin / white tin), when exposed to temperatures below
+13°C (+56°F) for long periods of time. Alloying pure tin with at least
5% lead (Pb) or at least 0.5% antimony (Sb) or bismuth (Bi) is
considered to be effective at preventing tin pest.
Wire Dress
The arrangement of wires and laced harnesses in an orderly manner.
10.2
ANSI ............
ACRONYMS AND ABBREVIATIONS
American National Standards Institute
ASTM ..........
American Society for Testing and Materials
cm2
Square Centimeters
..............
CVCM ..........
Collectable Volatile Condensable Material
DWV ............
Dielectric Withstanding Voltage
EEE .............
Electrical, Electronic and Electromechanical
EIA ...............
Electronic Industries Association
ESD .............
Electrostatic Discharge
IEEE ............
Institute of Electrical and Electronics Engineers
IPC ..............
Interconnecting and Packaging Electronic Circuits
MIL-STD ......
Military Standard
mm .............
Millimeter
MTTF ...........
Mean Time To Failure
NASA ...........
National Aeronautics and Space Administration
NASA-STD ..
NASA Standard
RH ...............
Relative Humidity
RMS ............
Root Mean Square
TML .............
Total Mass Loss
VDC .............
Volts Direct Charge
THIS PAGE IS INTENTIONALLY BLANK.
APPENDIX A - CLASS 3/A MILITARY / SPACE
Number:
Revision
A-1
CLASS 3/A MILITARY / SPACE
Page
Date:
1 of
Note: Appendices to IPC-D-620 are not binding, unless separately and specifically included by the
applicable contract, approved drawing(s), or purchase order.
STATEMENT OF STANDARD
TECHNICAL BACKGROUND
Though not officially recognized as a separate performance classification, a specialized classification for
spaceflight is levied by IPC/WHMA-A-620(SPACE), “Space Applications Electronic Hardware Addendum
to IPC/WHMA-A-620”. Commonly referred to as Class 3/A, this classification includes products where
continued high performance or performance-on-demand is critical, equipment downtime cannot be
tolerated, end-use environment may be uncommonly harsh, and the equipment must survive the vibration
and thermal cyclic environments experienced in military and spaceflight applications.
Space and Military Avionics classification deviations to IPC-D-620-2 are defined and listed in Table 1.
1.1
GENERAL REQUIREMENTS
1.2
SCOPE
This Addendum provides requirements to be used in addition to, and in some cases, in place of, those
published in IPC-D-620 to ensure the reliability of cable and wire harness assemblies that must survive
the vibration and thermal cyclic environments of military and/or spaceflight applications.
1.3
PURPOSE
When required by procurement documentation/drawings, this Addendum supplements or replaces
specifically identified requirements of IPC-D-620.
1.4
PRECEDENCE
The contract takes precedence over this Addendum, referenced standards and USER-approved drawings
(see IPC-D-620 [1.7.1]). In the event of a conflict between this Addendum and the applicable documents
cited herein, this Addendum takes precedence. Where referenced criteria of this Addendum differ from
the published IPC-D-620, this Addendum takes precedence. See Table 1 of this addendum, and clauses
1.7 Order of Precedence and 1.7.1 Conflict.
1.5
EXISTING OR PREVIOUSLY APPROVED DESIGNS
This Addendum shall not constitute the sole cause for the redesign of previously approved designs.
When drawings for existing or previously approved designs undergo revision, they should be reviewed
and changes made that allow for compliance with the requirements of this Addendum.
1.6
USE
This Addendum is not to be used as a standalone document. Where criteria are not supplemented, Class
3 shall apply. Where IPC-D-620 criteria are supplemented or new criteria are added by this Addendum,
the clause is listed in Table A1, Class 3/A - Military / Space Applications Requirements, and the entire
IPC-D-620 clause is replaced by this Addendum except as specifically noted.
The clauses modified by this Addendum do not include subordinate clauses unless specifically stated
(e.g., 1.4 does not include 1.4.1). Clauses, Tables, Figures, etc. in IPC-D-620 that are not listed in this
Addendum are to be used as-published.
TABLE A1
CLASS 3/A MILITARY / SPACE
IPC-D-620 Reference
CLASS 3/A Military / Space Requirement (as changed by this Addendum)
3.1.1.3.c
EASE OF CONNECT / DISCONNECT
Electrical connections and cable installations shall require no more than one
(1) turn to disconnect and reconnect without damage to wiring or connectors.
3.1.1.6
SERVICE LIFE
The design service life of a cable / wiring harness assembly shall be
specified as one (1) year in addition to the expected service life of the
hardware / system for which it has been designed.
4.2
FLAMMABILITY
Insulation materials shall be non-combustible or self-extinguishing. Selection
and use shall be traceable to acceptable flammability test reports. When no
test report exists, flammability testing shall be performed using the procedure
of NASA-STD-6001, previously NHB 8060.1C (Flammability, Odor,
Offgassing, and Compatibility Requirements and Test Procedures for
Materials in Environments that Support Combustion), or as otherwise
specified by the USER.
4.3
OUTGASSING
Nonmetallic materials shall not exceed 1% Total Mass Loss (TML) or 0.1%
Collected Volatile Condensable Material (CVCM), when tested in accordance
with ASTM-E595 (Test Method, Outgassing).
4.5
TIME-CRITICAL OR LIMITED-LIFE
Cables, wiring, associated hardware, and materials which are time-critical,
cycle-critical, or which have limited storage life / limited shelf life shall be
stored and controlled in accordance with the material manufacturer’s
recommendations, and the following additional controls:
Special storage requirements, and procedures for controlling shelf life and
shelf life extensions shall be carefully defined and strictly observed.
Each time-critical or limited-life assembly, subassembly, component, and
spare shall be clearly and indelibly marked with a serial number.
Appropriate documentation shall accompany all time-critical and limited-life
items and shall include the date of manufacture of the item and of its most
time-critical component.
Realistic life limits shall be assigned and documented for each item and shall
be suitably altered as new data and new evidence are obtained.
Operating-time logs shall be maintained for all items having limited operating
lives (e.g.: connector mating).
A time-age-life cycle database shall be maintained for verification (and
notification) of time-age-life component status. Status records shall be
maintained on all such items after installation.
Completed cables, harness assemblies, and associated hardware shall have
sufficient life remaining to adequately support the design service life
(3.1.1.6).requirement specified in the detail specification and/or contract.
4.8*
4.8.1.b
CONNECTORS
Connectors used in the fabrication of wire harnesses and cable assemblies
shall be suitable for the application; designed and approved for mating and
demating in the expected operating environment, under the maximum voltage
and current loads being carried, without producing electrical arcs that will
damage connector contacts; ignite surrounding materials or vapors; or,
expose the USER to electrical shock or injury.
*This change retains all subordinate clauses.
b. Test connectors shall comply with the above requirements when mated
with product connectors. <APEX14>
LEAD-FREE TIN (<3% Pb) TECHNOLOGY – CONTROL LEVEL 2C
The use of lead-free Tin (Sn) technology shall be prohibited unless
documented and controlled through a USER-approved Lead Free Control
Plan (LFCP) in conformance with Control Level 2B requirements of GEIASTD-0005-2, "Standard for Mitigating the Effects of Tin Whiskers in
Aerospace and High Performance Electronic Systems"
The use of lead-free Tin (Sn) technology in applications with exposure to
temperatures at or below -30°C (-22°F) shall be prohibited unless controlled
through mitigation.
4.8.5 (New)
For the purpose of this document, lead-free Tin (Sn) is defined as metallic Tin
(Sn) containing less than 3 percent lead (<3% Pb) by weight as an alloying
constituent. Lead-free Tin (Sn) technology is defined as electrical / electronic
components and associated mechanical hardware and materials composed
of, or coated / plated (internal / external surfaces) with metallic Tin (Sn)
containing less than 3 percent lead (<3% Pb) by weight as an alloying
constituent.
Lead-free Tin (Sn) technology shall include:
Wiring technology (i.e.: wire, cable, contacts, connectors, backshells,
terminators, clamps, braid / over-braid shield, etc.) composed of, or coated /
plated with metallic Tin (Sn) containing less than 3 percent lead (<3% Pb) by
weight as an alloying constituent.
Lead-free Tin (Sn) solder alloys containing less than 3 percent lead (<3% Pb)
by weight as an alloying constituent. Exception: Sn96.3Ag3.7
Any EEE components, electrical / electronic assembly, printed wiring
assembly (PWAs), cable assembly, and/or wire harness assembly assembled
with lead-free tin solder alloy except high temperature solder alloy
Sn96.3Ag3.7 (Sn96A).
Note: Sn96.3Ag3.7 shall only be used where specifically indicated by
approved drawings.
4.9.c (New)
PYROTECHNIC CIRCUITS - WIRE SPLICING
Splicing of wiring in pyrotechnic circuits is prohibited on both hardware firing
circuits and ground test firing circuits.
6.1*
WIRE TERMINATIONS
While wire terminations to connectors or terminals shall be made with a
crimp device (where practicable), all wire terminations shall be compliant with
the termination technology (i.e.: crimp terminations to crimp contacts, solder
terminations to solder contacts, insulation displacement terminations to IDC
contacts, etc.) of the connector / terminal.
*This change retains all subordinate clauses.
6.1.d
Screw type terminals shall be torqued to engineering specification and staked
to prevent loosening. Thread locking compounds are not recommended.
Adhesive / doping / staking compounds shall be compliant with flammability
and outgassing requirements. <APEX14>
6.1.1.f
The completed splice termination and any exposed metallization shall be
over-sleeved with heat shrink tubing / sleeving per IPC/WHMA-A-620SPACE. For mission critical harnesses incorporating splices, two (2) layers
of shrink sleeving shall be used over the splice area. Splices shall be
wrapped with protective tape to prevent cold flow of adjacent wiring and
possible abrasion of shrink sleeving over the splice area. <APEX14>
6.2
FORM LAYOUT FIXTURE
A full-sized, three-dimensional (3-D) form layout fixture shall be provided for
all complex interconnecting cables and harnesses to ensure proper routing,
wire lengths, connector configurations, support requirements, and access
requirements of the wiring harnesses. The form layout fixture may be limited
to partial installations which contain the more complex wiring harnesses.
6.5
BEND RADIUS
The bend radius for cables and harness assemblies shall conform to
IPC/WHMA-A-620 (SPACE), Table 14-1.
6.8*
IDENTIFICATION AND MARKING
To facilitate the rapid identification, isolation, and repair of circuits, each wire,
cable, and connector in interconnecting cables and wiring harnesses shall be
permanently marked with a unique identification code.
*This change retains all subordinate clauses.
6.13.c
Sealing on tape wrapped, braided, striped, or other than smooth circular
insulations shall be subject to USER approval, unless compatibility has been
demonstrated in the qualification of the terminating device. <119 – A/M, move
to A - APEX14>
REMARKS
THIS PAGE IS INTENTIONALLY BLANK.
APPENDIX B - RED PLAGUE CONTROL PLAN
Number:
Revision
B-1
RED PLAGUE CONTROL PLAN (RPCP)
Page
Date:
1 of
Note: Appendices to IPC-D-620 are not binding, unless separately and specifically included by the
applicable contract, approved drawing(s), or purchase order.
STATEMENT OF STANDARD
TECHNICAL BACKGROUND
Red Plague (cuprous oxide corrosion) can develop in silvercoated soft or annealed copper conductors (component leads,
single and multi-stranded wires and PCB conductors) when a
galvanic cell forms between the copper base metal and the
silver coating in the presence of moisture (H2O) and oxygen
(O2). Once initiated, the sacrificial corrosion of the copper
base conductor can continue indefinitely in the presence of
oxygen. The color of the corrosion by-product (cuprous oxide
crystals) may vary depending on the different levels of oxygen
available, but is commonly noted as a red/reddish-brown
discoloration on the silver coating surface.
Figure B-2
Red Plague (Cuprous Oxide Corrosion)
M22759/20-22-09
Mechanical Damage The primary initiator of cuprous / cupric
oxide corrosion (Red Plague) is mechanical damage of the
silver coating during wire manufacturing (i.e.: drawing, stranding, application of insulation jackets, etc.)
resulting in exposure of the copper-silver interface to atmospheric moisture and oxygen. Other common
sources of mechanical damage include improper assembly and installation practices (i.e.: excessive
flexing. improper bend radius, etc.).
Environmental Conditions
In order for cuprous / cupric oxide corrosion (Red Plague) to develop, a
galvanic cell must form between the copper base metal and the silver coating in the presence of water
(H2O) and oxygen (O2). Since only a small amount of water is required, protection from high humidity and
oxygen and other contaminants such as aqueous solvents and cleaning systems is considered the
greatest significant mitigation against cuprous / cupric oxide (Red Plague).
Inadequate Silver Coating Thickness Porous, discontinuous, and thin silver coatings are more likely to
develop cuprous / cupric oxide corrosion (Red Plague) since a greater number of sites for galvanic cells to
form between the copper base metal and the silver plating are possible. Silver coating thicknesses below
1 micron (~ 40 micro-inches) are more easily damaged during manufacturing and handling, thus
increasing susceptibility. Increasing the silver coating thickness to 2 micron (~ 80 micro-inches) has
shown improved resistance to corrosion.
High Temperature Though the upper continuous operating temperature rating of most silver-coated
wiring is +200°C (+392°F), exposure to temperatures approaching +200°C (+392°F) or higher, induces
migration of the copper base metal through the silver coating. This may reduce the silver coating
thickness and create porosity sites for cuprous/cupric oxide corrosion to occur. This effect is typically
experienced only in long duration operation at temperatures beyond the wire’s continuous rating, or in
instances where the wiring is exposed to excessive heat during test or highly accelerated burn-in.
Chemical Attack
Exposure to chemicals present in the environment (oxygen, sulfur compounds, salt,
etc.) may result in corrosion and corrosion by-products that attack and compromise the mechanical
integrity of the silver coating. Common “green” packaging materials, paper wrapping materials, rubber
bands, and cardboard boxes should be avoided because such materials often contain and outgas small
amounts of sulfur. Exposure to atomic oxygen (AO) in spaceflight applications has been shown to tarnish
and pit silver coatings.
1
GENERAL REQUIREMENTS
1.1
SCOPE
This document prescribes requirements for the control and mitigation of performance and reliability risks
associated with the use of silver-coated copper conductors and technology in the manufacture of electrical
and electronic assemblies, including optical and metallic cable and wiring harness assemblies, and elements
thereof.
1.2
PURPOSE
The intent of this document is to establish a baseline of requirements, procedures, practices, and process
attributes based on Lessons Learned and Best Practices that have been demonstrated through use and
experience, to result in a robust design and high reliability.
It is not the intent of this document to exclude any alternate or contractor-proprietary documents or
processes that meet or exceed the baseline of requirements established by this document. Use of alternate
or contractor-proprietary documents or processes shall require review and prior approval of the User.
1.3
APPLICABILITY
This document is targeted for applications where exposure to assembly processes, environmental
conditions, and contamination may promote the development of cuprous / cupric oxide corrosion (a.k.a. Red
Plague) in silver-coated copper wire, cable, and harness assemblies. The requirements of this document
apply to all organizations involved in the design, manufacture, and installation of silver-coated copper wire,
cable, and harness assemblies. The User is responsible for determining whether the control of cuprous /
cupric oxide corrosion (Red Plague) may be required to ensure performance or reliability.
1.3.1 REQUIREMENTS FLOWDOWN
This document shall not be binding, unless separately and specifically included by the applicable contract,
approved drawing(s), or purchase order. When this standard is contractually invoked, the applicable
requirements of this standard shall be imposed on all applicable subcontracts, assembly drawing(s),
documentation and purchase orders.
1.3.2 AUTHORITY
The authority for this document derives from requirement 0.1.7 Red Plague (Cuprous/Cupric Oxide
Corrosion) of IPC/WHMA-A-620B-S “Space Applications Electronic Hardware Addendum to IPC/WHMA-A620B”, and requirement 0.1.7 Red Plague (Cuprous Oxide Corrosion) of IPC J-STD-001ES “Space
Applications Electronic Hardware Addendum to IPC J-STD-001E Requirements for Soldered Electrical and
Electronic Assemblies”.
1.3.3 COMMERCIAL OFF-THE-SHELF (COTS)
The requirements of this document shall not apply to suppliers of commercial off-the-shelf (COTS) items.
Projects which use COTS hardware for applications described above shall be responsible for identifying
and managing risks associated with hardware that was built without a control plan to reduce the harmful
effects of Red Plague (cuprous oxide corrosion).
1.3.4 EXISTING OR PREVIOUSLY APPROVED DESIGNS
The requirements of this document shall not constitute the sole cause for the redesign of previously
approved designs. When drawings for existing or previously approved designs undergo revision, they
should be reviewed and changes made that allow for compliance with the requirements of this document.
1.4
ORDER OF PRECEDENCE
The following shall be applicable in the resolution of conflict between the requirements or the text of this
document; and, applicable documents, and approved / unapproved engineering documentation in the order
indicated:
a. Contract / Program Requirements
b. Engineering Documentation (User-Approved Drawings / Referenced Documents)
c. This Document
d. Engineering Documentation (Applicable Documents / Published IPC Standard)
e. Engineering Documentation (Un-approved Drawings)
f. Verbal Correspondence (ALWAYS get it in writing!)
1.5
MEASUREMENT UNITS AND TOLERANCES
All dimensions and tolerances, as well as other forms of measurement (temperature, weight, etc.) in this
standard are expressed in SI (System International) units (with Imperial English equivalent dimensions
provided in brackets). Dimensions and tolerances use centimeters (inches) as the main form of dimensional
expression; microns (micro-inches) are used when the precision required makes centimeters too
cumbersome. Celsius (Fahrenheit) is used to express temperature.
1.6
TERMS AND DEFINITIONS
Terms and definitions are consistent with those listed in IPC-T-50. For the understanding of this document,
selected terms and definitions are listed in Section 9.
1.7
APPROVAL OF DEPARTURES FROM THIS DOCUMENT
Any changes, revisions, or deviations to this document or to the requirements referenced by this document
shall require technical evaluation and approval by the User prior to handling or processing of hardware.
a. Oral statements shall not be permitted in any manner or degree to modify or otherwise affect the
requirements of any portion of this document.
b. Use of alternate control plans, documents, or processes shall require review and approval of the User
prior to use.
c. Less stringent control plans, documents, or processes are allowed in exceptional cases with the review
and approval of the User prior to use.
d. Requests for relief from requirements in this document shall require review and approval of the User
prior to use.
2
APPLICABLE DOCUMENTS
The following documents are applicable to the extent specified herein. The applicable revision shall be that
identified herein or the revision in effect on the date of the contract or work authorizing document.
2.1
FEDERAL STANDARDS
FED-STD-228 .......................... Cable and Wire, Insulated; Methods of Testing
2.2
MILITARY STANDARDS
MIL-D-3464E ........................... Desiccants, Activated,
Dehumidification (Type II)
Bagged,
Packaging,
MIL-I-8835A ............................. Indicator, Humidity, Card, Chemically
Reversible), 50-60-70-80-90% RH
Use
Impregnated
and
Static
(Irreversible
/
MIL-PRF-81705-A1 ................. Barrier Materials, Flexible. Electrostatic-Free. Heat Sealable (Type 1)
MIL-STD-2073-1E ................... Standard Practice for Military Packaging (Method 50)
MIL-STD-2223 ......................... Test Methods for Insulated Electric Wire
MIL-W-29606 ........................... Wire, Electrical, Stranded, Uninsulated Copper, Copper Alloy, or
Aluminum, or Thermocouple Extension, General Specification For
2.3
INDUSTRIAL STANDARDS
ASTM B 263-04 ....................... Standard Test Method for Determination of Cross-Sectional Area of
Stranded Conductors
ASTM B 298-07 ....................... Standard Specification for Silver-Coated Soft or Annealed Copper Wire
ASTM B 624-99 (R2005) ......... Standard Specification for High-Strength, High-Conductivity Copper-Alloy
Wire for Electronic Application
ASTM B 961-08 ....................... Standard Specification for Silver Coated Copper and Copper Alloy
Stranded Conductors for Electronic Space Application
ASTM E3 ................................. Standard Guide for Preparation of Metallographic Specimens
IPC-QL-653A ........................... Certification of Facilities that Inspect / Test Printed Boards, Components,
and Materials
IPC-T-50H ................................ Terms and Definitions for Interconnecting and Packaging Electronic
Circuits
SAE AMS-DTL-23053/4 ............ Insulation Sleeving, Electrical, Heat Shrinkable, Polyolefin, Dual-Wall,
Outer Wall Cross-linked
2.4
REFERENCE DOCUMENTS
Unless otherwise specified, these documents fall in order of precedence behind the contract, approved
drawings, and any standards imposed on the program. The requirements and recommendations in these
documents are not binding and are not to be construed as implied requirements to be imposed on the
program. Nor are they to be used if they conflict with any contractual or program-specific requirements.
ECSS Q-70-20A ...................... Determination of the Susceptibility of Silver-Plated Copper Wire and Cable
to “Red-Plague” Corrosion
MIL-HDBK-338B ...................... Electronic Reliability Design Handbook
MIL-HDBK-1250A .................... Handbook for Corrosion Prevention and Deterioration Control in Electronic
Components and Assemblies
SAE AIR4487 .......................... Investigation of Silver Plated Conductor Corrosion (Red Plague)
“Corrosion of Silver-Plated Copper Conductors”, B.D. Dunn, A. de Rooij & D.S. Collins
Metallurgical Assessment of Spacecraft Parts, Materials and Processes; “Red Plague Corrosion of SilverPlated Copper”; Barrie D. Dunn; 6.8.3 / pg. 446-447; Wiley-Praxis; 1997; ISBN 0-471-96428-X
3
RED PLAGUE CONTROL PLAN (RPCP)
The use of silver-coated copper conductors shall require the implementation of a User-approved Red
Plague Control Plan (RPCP) to reduce and control exposure to environmental conditions and
contamination that promote the development of cuprous oxide corrosion (Red Plague) and latent damage.
The minimum requirements are as outlined below:
3.1
CONDUCTOR STRAND MATERIAL AND COATING
All strands used in conductors specified herein shall conform to the applicable ASTM standards for the
material listed in Table 1, or User-approved standards.
TABLE 1
3.2
CONDUCTOR STRAND MATERIAL AND COATING
Thickness
Application ASTM
or ANSI standard
Designator
Strand material
SCC
Annealed copper
SCC1
Annealed copper
SCA
High strength copper alloy
1 MICRON (~40 MICROINCH)
ASTM B298
ASTM-B624
SCA1
High strength copper alloy
2 MICRON (~80 MICROINCH)
ASTM B298
ASTM-B624
ASTM-B961
SCU
Ultra-high strength copper alloy
1 MICRON (~40 MICROINCH)
None
1 MICRON (~40 MICROINCH)
2 MICRON (~80 MICROINCH)
ASTM-B298
ASTM-B298
ASTM-B961
SILVER COATING REQUIREMENTS
3.2.1 1 MICRON (~40 MICRO-INCHES)
Primary and shield conductors shall have a coating thickness of not less than 1 micron (~40 micro-inches)
average, when measured in accordance with ASTM B 298-07.
3.2.2 2 MICRON (~80 MICRO-INCHES)
Primary and shield conductors shall have a coating thickness of not less than 2 micron (~80 micro-inches)
average, when measured in accordance with ASTM B 298-07. After stranding, the coating thickness on
each of the individual conductor strands shall not be less than 1 micron (~40 micro-inches) when inspected
using micro-section analysis in accordance with ASTM B 961-08.
3.2.3 ADDITIONAL REQUIREMENTS
The following additional requirements are applicable to all silver-coated copper wire and cable:
a. After stranding (drawing and twisting strand groups), the silver coating shall exhibit a non-porous,
smooth, and continuous finish free from lumps, kinks, splits, scrapes, corrosion, contamination, exposed
base material, or coating impurities.
a. Micro-section inspections shall be in accordance with ASTM-B961, except that the coating thicknesses
specified herein shall be in effect. Micro-section analysis shall be performed by a lab certified to IPCQL-653A, or as agreed upon by the USER.
b. Photographs / micrographs. When required by the procurement specification, photographs /
micrographs shall be provided as proof of inspection. The magnification scale shall be identified.
3.3
PROCUREMENT
All silver-coated copper wire and cable shall be procured in accordance with the wire procurement
specification. The source shall be from suppliers listed on the wire suppliers’ Qualified Manufacturers List
(QML), Defense Supply Center Columbus (DSCC), SAE International (SAE), or suppliers approved by the
User.
a. All wire and cable shall have full lot traceability and manufacturer’s test reports.
b. Test reports, and all tested and untested micro-section analysis coupons, shall be delivered to the
USER as part of the procurement.
c.
When required by the procurement specification, Government Source Inspection (GSI) shall certify that
the tests have been performed on the length of wire procured.
3.4
FLUORINE ATTACK (WHITE PLAGUE)
To reduce the risk of fluorine attack (White Plague), when fluoropolymer-insulated silver-coated copper
wiring is either stored in sealed packaging (e.g.: vapor-proof bagging, MBB) or used in enclosed
environments / compartments, the fluorine evolution (outgassing) rate of the insulation shall not exceed
20 PPM when tested in accordance with SAE AS4373E Method 608, Fluoride Offgassing. Bulk wiring
exhibiting fluorine attack on the coating surface (a dull, dusty, grey/white texture and/or reduced
solderability), and harness assemblies exhibiting surface corrosion / pitting on connectors and
accessories, shall be rejected.
3.5
LIMITED LIFE ARTICLE
a. Silver-coated copper wire and cable that has exceeded a shelf life of ten (10) years from
manufacturing date shall not be used on assemblies fabricated to this standard.
b. Completed cable, harness assemblies, and hardware incorporating silver-coated copper conductors,
with a combined storage and use life exceeding 10 years from date of assembly should be identified
and tracked as a “Limited-Life Article”. Surveillance (Functional Test) prior to use is recommended.
3.5.1 SURVEILLANCE (FUNCTIONAL TEST)
A surveillance program involving subjecting hardware to functional test prior to use is recommended as
limited mitigation of performance and reliability risks associated with the use of silver-coated copper
conductors and technology in electrical and electronic assemblies with a combined storage and use life
exceeding 10 years from date of assembly.
a. The User must recognize and accept that there is a significant assumption of risk in using this
strategy because a false sense of security can be generated if no corrosion is detected and/or the
hardware passes functional acceptance tests.
b. Functional acceptance testing only verifies that hardware performance has not degraded to a level
detectable by the test. As such, the tests should not be used as “certification” that the tested
hardware corrosion-free – only that the hardware was functional at the time of test.
4
ENVIRONMENTAL REQUIREMENTS
Silver-coated copper wire and cable shall be protected to reduce and control exposure to environmental
conditions and contamination that promote the development of cuprous / cupric oxide corrosion (Red
Plague).
4.1
PACKAGING - SHIPPING AND STORAGE
Silver-coated copper wire and cable shall be shipped and stored in sealed water-vapor-proof packaging
(i.e.: Moisture Barrier Bag, dry pack, etc.), with capped ends, activated desiccant, and an irreversible
humidity indicator card (i-HIC).
a.
Water-vapor-proof packaging shall meet MIL-STD-2073-1E Method 51.
b.
Moisture Barrier Bags (MBB) shall meet MIL-PRF-81705, TYPE 1.
c.
Capping. Wire and cable ends shall be capped with heat shrinkable end-caps conforming to SAE-AMSDTL-23053/4, or dipped in Red “GLPT” Insulating Varnish (10-9002-A / 10-9008 / N.S.N. 5970-00-9015331) for a length of approximately 2.5 cm (1 in). [See 6 – Capping]
d.
Desiccant (Activated). The bagged, activated desiccant shall conform to MIL-D-3464 Type 2. The minimum
quantity of desiccant to be used (unit packs) shall be based on the protective package’s interior
exposed surface area, in accordance with MIL-STD-2073-1E, Method 50, Formula 1.
e.
Irreversible Humidity Indicator Card (i-HIC)
(1) Indication (50-60-70-80-90% RH).
(2) The Irreversible Humidity Indicator Card (i-HIC) shall be retained as a Quality Record (QR).
f.
Prohibited Packaging Materials. Silver-coated copper wire and cable shall not be stored unprotected in
paper wrapping materials or cardboard boxes.
4.2
ASSEMBLY PROCESSES
All assembly processes, including Receiving Inspection and Kitting, shall be conducted in an
environmentally-controlled and monitored area where dew point is not attained and the relative humidity is
less than 70%RH.
a. Wire and cable shall not be removed from its protective packaging until it has reached thermal
equilibrium with the assembly environment to reduce the risk of condensation formation.
b. Unused Wire. Prior to returning unused wire to storage, the wire ends shall be capped per 4.1.c to
prevent diffusion of air and water vapor into the wire through the open end(s). The wire shall be stored
per 4.1.
c.
Wiring, cable, and harness assemblies shall be stored in an environmentally-controlled and monitored
area where dew point is not attained and the relative humidity is less than 70%RH:
(1) Wiring, cable, and harness assemblies that are not being actively worked on.
(2) Completed cable and harness assemblies until ready for installation.
d. Aqueous (water / water-based) solvents and cleaning systems shall not be used.
5
QUALITY ASSURANCE
Quality Assurance (QA) shall verify conformance to the requirements of this RPCP and the wire
procurement specification. Any evidence of non-conformance shall require quarantine of the entire spool
and disposition by the appropriate Material Review Board (MRB). [See 6, Nonconformance]
5.1
RECEIVING INSPECTION
Primary and shield conductors shall be visually inspected for mechanical damage and cuprous / cupric
oxide corrosion (Red Plague).
a. Test Specimen. One (1) test specimen, approximately 30 cm (12 in) in length (including the capped
end), to perform the required inspection(s) shall be required:
(1) From each end of each continuous, unspliced length reel or spool.
(2) From each end of reeled or spooled wire sections (non-continuous lengths).
(3) From each end of coiled lengths.
b. Magnification. Magnification power for visual inspection shall be based on the inspection activity or
conductor size, per J-STD-001 or IPC/WHMA-A-620. For wire and cable with mixed conductor sizes,
the greater magnification power may be used for the entire inspection.
c.
Illumination. Illumination intensity on the surface being inspected shall be at least 1000 lm/m2 (~93 footcandles). The light source type shall be as specified by engineering documentation.
Note:
In selecting illumination, temperature (color) and source type (shadowless / oblique) are important
considerations. Light temperatures ranging from 3000 - 5000 °K increase the ability to differentiate base
metals, coatings, and porosity. Shadowless lighting is useful for cleanliness and general damage inspection,
while oblique lighting is useful for detecting surface anomalies such as plating cracks, nodules, and whiskers.
d. Acceptance. The silver coating shall exhibit a non-porous, smooth, and continuous shiny or satin
finish, with no evidence of lumps, kinks, splits, flaking, scrapes, corrosion, contamination, discoloration,
oxidation, or exposed base conductor. Exposed base conductor on the wire end(s) is acceptable.
5.2
STORAGE
Wire and cable that has been accepted shall be stored per 4.1 – Shipping and Storage, or stored in an
environmentally-controlled and monitored area where dew point is not attained and the relative humidity is
less than 70%RH.
5.3
70% RH Indication
An indication of 70%RH (or higher) on the humidity indicator card (i-HIC) shall result in immediate rejection
and segregation of the wire, cable and/or harness assemblies from stock and production. [See 7 –
Nonconformance]
6
ASSEMBLY REQUIREMENTS
The following controls shall be imposed during the assembly of hardware incorporating silver-coated copper
wire and cable:
6.1
PRE-PRODUCTION SAMPLE
Prior to material take off for assembly or kitting, a pre-production sample of the wire / cable shall be visually
inspected for mechanical damage and cuprous oxide corrosion. Any evidence of non-conformance shall
require quarantine of the entire spool and disposition by the appropriate Material Review Board (MRB).
6.2
WIRE STRIPPING
To reduce exposure to moisture and oxygen, wire insulation shall be stripped just prior to termination.
a. Solder terminations. The insulation shall be left on the wire until assembly, at which time the wire shall
be stripped and immediately solder tinned to minimize the exposure time of the silver-copper endface to
atmospheric moisture and oxygen.
b. Crimped terminations. The crimp termination of silver-coated cooper wire is not recommended, unless
additional mitigation (i.e.: heavier plating thickness, environmentally rated connector, conformal coating,
shrink sleeving, etc.) is implemented to protect the exposed end of the conductor(s).
6.3
BEND RADIUS
Wire and cable shall not be bent less than minimum bend radius requirements to avoid cracking of the
insulation and/or silver coating.
6.4
CLEANING SOLVENTS
Aqueous (water-based) solvents and cleaning systems shall not be used for cleaning.
7
NON-CONFORMANCE
Non-conformance to any of the above requirements shall require:
a. Immediate rejection and segregation of the wire, cable and/or harness assemblies from stock and
production.
b. Relocation of the wire, cable and/or harness assemblies to a dry area or otherwise protected (i.e.: placed in
a nitrogen-purged dry box, MBB, etc.) to prevent continued environmental exposure / damage.
c.
Disposition by the appropriate Material Review Board (MRB).
d. Non-conformances dispositioned other than scrap shall be approved by the USER.
8
CAPPING
Capping provides a simple and effective environmental barrier to oxygen and moisture contamination of the
cut / exposed ends of silver-coated copper wire and cable by sealing the cut / exposed ends of the wire /
cable with double-wall (melt-liner) heat shrinkable tubing or preformed end cap, or by dip coating with Red
“GLPT” Insulating Varnish.
8.1
SHRINK TUBING METHOD
This method uses double-wall (melt-liner) shrink tubing conforming to SAE-AMS-DTL-23053/4D to create a
crimped-end “cap” to environmentally seal the exposed end of the wire / cable. If a preformed double-wall
(melt-liner) heat shrinkable end cap is used, the crimping of the “tail” (step e) is not required.
a. Clean the wire / cable end and approximately 5 cm (2 in) of the insulation jacket with IPA. The wire /
cable shall be positioned with the cut end pointed downward to minimize wicking of cleaning solvent.
b. Cut shrink tubing sections approximately 5 - 8 cm (2 to 3 in) in length.
c. Insert approximately 2.5 cm (1 in) of the open-end silver-plated copper wire / cable into one end of the
shrink tubing, with the remaining shrink tubing forming an open “tail”.
d. Use a heat gun to shrink the tubing down over the wire / cable and to shrink the “tail”.
e. When the inner wall of the shrink tubing has melted, crimp the “tail” (only) with smooth-jaw pliers to
flatten and close the tubing. Hold pressure on the “tail” for 20 to 40 seconds until the inner liner cools
and solidifies.
Visually inspect to verify that the tubing has been shrunk tightly, that the melt liner has adhered to the
wire / cable insulation, and that the crimped “tail” is sealed. The sleeving shall not exhibit damage (i.e.:
blisters, lumps, dents, tears, pinholes, seams, cracks, foreign matter, or other defect) that would
compromise the environmental seal.
f.
8.2
DIP COATING METHOD
This method creates an environmental seal by coating and saturating the exposed end of the wire / cable
with Red “GLPT” Insulating Varnish (or other approved sealant). Though the basic process involves dipping
the wire / cable end into the varnish / sealant, the process could be modified to use brush or swab
applicators, if approved by the USER.
a. Clean the wire / cable end and approximately 5 cm (2 in.) of the insulation jacket with IPA. The wire /
cable shall be positioned with the cut end pointed downward to minimize wicking of cleaning solvent.
Do not use aqueous cleaners.
b. Allow to dry and visually inspect for cleanliness.
c. Slowly dip the end of the cable / harness into the varnish to a depth of approximately 2.5 cm (1 in). A
slow dip speed is recommended to prevent bubbles forming on wire / cable end and to prevent
splashing of the varnish.
d. Slowly remove the wire / cable end from the varnish and allow to dry. The wire / cable end should be
positioned with the coated end pointed downward to minimize wicking of varnish and to allow excess
material to drip.
e. Visually inspect to verify that coverage is continuous and of uniform thickness. The coating shall not
exhibit defects (i.e.: incomplete coverage or cure, exposed conductor surfaces, pinholes, cracks, foreign
matter, etc.) that would compromise the environmental seal.
9
ACRONYMS, ABBREVIATIONS, AND TERMS
For purposes of this document, the following additional acronyms, abbreviations, and terms are listed in
addition to those listed in IPC-T-50J, “Terms and Definitions for Interconnecting and Packaging Electronic
Circuits”.
9.1
ACRONYMS AND ABBREVIATIONS
Acronym
Definition
GSI
Government Source Inspection
i-HIC
Irreversible Humidity Indicator Card
SCA
Silver-Coated Copper-Alloy, 1 micron (~40 micro-inches)
SCA1
Silver-Coated Copper-Alloy, 2 micron (~80 micro-inches)
SCC
Silver-Coated Copper, 1 micron (~40 micro-inches)
SCC1
Silver-Coated Copper, 2 micron (~80 micro-inches)
SCU
Silver-Coated Ultra-High Strength Copper Alloy
9.2
GLOSSARY OF TERMS
Term
Description
Capping
A process involving the sealing of the cut / exposed ends of the wire / cable
with a double-wall (melt-liner) heat shrinkable tubing or preformed end cap, or
by dip coating with Red “GLPT” Insulating Varnish, to create an environmental
barrier to oxygen and moisture contamination.
Desiccant
A chemically-inert media used to absorb moisture from the air within a
sealed container or package to induce or sustain a level of dryness
(desiccation).
Dew Point
The temperature at which a volume of air at a given atmospheric pressure
reaches saturation and the entrained water vapor precipitates and condenses.
Dry Pack
An environmental protection system consisting of activated desiccant material,
a Humidity Indicator Card (HIC), and water-vapor-proof packaging (i.e.:
Moisture Barrier Bag – MBB).
Red Plague (Cu2O)
The sacrificial corrosion of copper in a galvanic interface comprised of silver
and copper, resulting in the formation of red cuprous oxide (Cu2O). Galvanic
corrosion is promoted by the presence of moisture (H2O) and oxygen (O2) at
an exposed copper-silver interface (i.e.: conductor end, pin-hole, scratch, nick,
etc.).
Unit Pack (Desiccant)
The standardized unit of desiccant material, which at thermal equilibrium with
air at +77°F (+25°C), will adsorb at least 3 gm (~0.1 oz) of water vapor at 20%
relative humidity (RH) and at least 6 gm (~0.2 oz) of water vapor at 40%RH.
REMARKS
THIS PAGE IS INTENTIONALLY BLANK.
APPENDIX C - RESTRICTED MATERIALS / PROCESSES
Note: Appendices to IPC-D-620 are not binding, unless separately and specifically included by
the applicable contract, approved drawing(s), or purchase order.
Beeswax
Wax (all types)
Beeswax impregnated lacing tape shall not be used for Class 3 products.
Wax impregnated lacing tape shall not be subjected to cleaning solvents.
Beryllium (Be)
Beryllium shall not be used for primary structural applications or as an alloying
constituent exceeding 4% (percent) by weight. Beryllium is allowed as an
alloying constituent up to a maximum of 4% (percent) by weight.
Cadmium (Cd)
Cadmium and cadmium plating in electrical connectors, cables, wiring harness
assemblies, and mechanical fasteners shall not be used where exposure to
elevated temperatures and reduce atmospheric pressures could cause
sublimation (vaporization) and deposition of cadmium on optical or electrically
energized surfaces.
Rationale
There are several reasons for prohibiting the use of Cadmium plating.
1. Cadmium has the ability to sublimate (vaporize), if exposed to temperatures
in excess of +75 °C (+167 °F), and reduced atmospheric pressure or
vacuum. This temperature is well under the rated temperatures of
approved wire insulations, thereby reinforcing the need for a cadmium
prohibition as today’s wire gauge selections often take advantage of
insulation temperature tolerances. The resulting toxic, heavy-metal vapor
can be inhaled by the USER, or condense onto surfaces as a thin,
electrically conductive layer, impacting the performance of electrical circuits
and optical systems.
2. Cadmium plating on tool surfaces can be transferred to the surfaces of
hardware and fasteners.
3. Cadmium is subject to the spontaneous growth of Cadmium whiskers. The
propensity of Cadmium to grow whiskers appears to be lower than that of
zinc and especially tin. Cadmium whiskers (like tin whiskers) grow
spontaneously and are capable of causing electrical failures ranging from
parametric deviations to sustained plasma arcing that can result in
catastrophic short circuits.
Recommendations
Cadmium plating is commonly used on connectors, connector hardware and
mechanical hardware such as fasteners. It provides excellent resistance to salt
corrosion and is therefore offered in many military specifications predominantly
for use in naval applications. However, most applications are not concerned
with salt corrosion and the risks associated with use of Cadmium plating noted
above outweigh the benefits of its use.
There are several alternatives to Cadmium plating that are suited for spaceflight
use:
1. For connectors, electroless nickel plating is preferred. Gold plating is
preferred when the application requires additional shielding effectiveness,
improved electrical conductivity in RF applications, or where low residual
magnetism is desired.
2. Passivated stainless steel is the preferred material for hardware items such
as fasteners.
Consult your materials or parts specialists for suggested alternatives to Cadmium
plating.
Glass (157)
Windows and other glass structures (e.g.: optics, instrument covers, etc.) that
include any piece of glass and other glass-like materials (e.g.: germanium,
sapphire, etc.) shall not [N1N2D3] be used for Class 3 and Space products
unless it is suitably contained or protected.
E/E components (e.g.: connectors, RF feed-through, diodes, components with
glass-body seals, fiber optic, etc.) that use glass as the component body,
dielectric, wave guide, or hermetic seal are specifically exempted from this
requirement.
Rationale:
The breakage / shattering of glass presents an acute eye and laceration injury
and Foreign Object Debris (FOD) hazard.
Glycol
Ethylene Glycol
Propylene Glycol
When solutions containing ethylene glycol and propylene glycol are used in
hardware which have electrical or electronic circuits containing silver or silvercoated copper, a silver chelating agent such as benzotriazole (BZT) shall be
added to the solution to prevent spontaneous ignition from the reaction of silver
with ethylene glycol and propylene glycol.
When solutions containing other glycols (aliphatic dihydric alcohols) are used in
these conditions, testing shall be conducted to determine if the same
spontaneous ignition reaction can occur as with ethylene glycol and propylene
glycol, and a silver chelating agent shall be added to the solution if ignition can
occur.
Magnesium (Mg)
Magnesium alloys shall not be used except in areas where minimal exposure to
corrosive environments can be expected and protection systems can be
maintained with ease and high reliability.
Magnesium alloys shall not be used in the primary structure or in other areas
subject to wear, abuse, foreign object damage, abrasion, erosion, or at any
location where fluid or moisture entrapment is possible.
Mercury (Hg)
Equipment containing mercury shall not be used where the mercury could
come in contact with electrical connectors, cables, and wiring harness
assemblies during manufacturing, assembly, test, checkout, and use.
Rationale
Mercury (Hg) is a particularly hazardous material because of its toxicity and
tendency to penetrate joints and amalgamate structure materials. Metal
contaminated while under high stress will receive greater penetration of mercury
and degradation of ability to withstand stress than will metals under relatively low
stress. Aluminum contaminated by contact with mercury will rapidly corrode, as
the mercury prevents formation of the protective oxide layer on the aluminum’s
surface.
An environment containing mercury vapor in concentrations of 0.005 mg/m3 () or
greater is not acceptable for continuous human occupancy.
Coronal discharge can occur at low voltage potentials in the presence of mercury
vapor.
Recommendations
1. Well-protected lamps containing mercury, including those used in the
fluorescent die-penetrant inspection are exempt from this requirement.
2. Mercury must not be removed from metal surfaces with any abrasive
cleaning method. The removal of oxide films on the metal will cause
immediate mercury penetration.
Polyvinyl Chloride
(PVC)
(158, 161)
The use of polyvinylchloride (PVC) insulated wire or cable shall not be used in
applications where temperatures exceed +49°C (+120°F), or in low pressure
(<20684 Pa [<3 PSIA] environments, under normal or emergency conditions.
Non-lead stabilized PVC (classified as RoHS compatible) shall not be used
without USER approval.
Rationale:
1. PVC is subject to insulation displacement at bends and other pressure points
in the wire (i.e., “cold flow”) which can cause shorts to occur over time.
2. Outgassed products are hazardous and corrosive. Products include
hydrogen chloride, phosgene, CO, CO2 chlorine monoxide, and acidic
carbonaceous coke.
3. Plasticiser loss causes discoloration and embrittlement.
Silver (Au)
Silver-plated hardware and finishes shall not be used in applications where
condensing moisture, salt fog, sulfur compounds, or atomic oxygen are present.
Use of electroplated silver is prohibited as a plated surface on printed wiring
boards, terminal boards and bus bars.
Rationale
1. Bare or defectively insulated silver or silver-coated copper components such
as wire, pins, sockets, or connectors impressed with a direct current potential
can spontaneously ignite and burn when exposed to ethylene glycol solutions
that do not contain a silver chelating agent.
2. Porosity in the gold plating on contacts can expose the silver underplate,
resulting in oxidation, increased electrical resistance, and fretting.
3. Silver is known to be susceptible to electro-migration, resulting in short
circuits.
Lead-Free Tin (<3%
Pb) Technology
(162)
The use of lead-free Tin (Sn) technology in Class 3 and Space applications shall
be prohibited unless documented and controlled through a User-approved Lead
Free Control Plan (LFCP) in conformance with Control Level 2C requirements of
GEIA-STD-0005-2, "Standard for Mitigating the Effects of Tin Whiskers in
Aerospace and High Performance Electronic Systems".
The use of lead-free Tin (Sn) technology in applications with exposure to
temperatures at or below -30°C (-22°F) shall [N1A2A3] be prohibited unless
controlled through mitigation. See Appendix C “Restricted Materials / Processes”
and Appendix G “Lead-Free Control Plan (LFCP)” for technical guidance.
Rationale
Lead-Free Tin (<3% Pb) Technology is susceptible to the spontaneous growth of
electrically conductive single crystal structures known as tin whiskers. Over time
these whiskers may grow to be several millimeters (mm) long. Tin whiskers are
capable of causing electrical failures ranging from parametric deviations to
sustained plasma arcing (in vacuum) that can result in catastrophic short circuits.
Recommendations:
1. Growth of whiskers has been shown to be controllable by tinning with tin-lead
(SnPb) solder, and as little as 2 %Pb (lead) in the alloy or tin plating will
significantly reduce whisker growth.
2. Conformal coatings will not stop whisker development. Preliminary results
from various NASA and industry-sponsored studies indicate that resilient
conformal coatings (i.e.: urethanes (UR), silicones (SR), etc.) appear to only
slow whisker growth.
3. Rigid coatings such as acrylics (AR), epoxies (ER), and paraxylene (XY) may
offer some whisker protection, but present additional reliability and rework
issues that must be taken into consideration by the design engineer.
Titanium (Ti)
Titanium shall not be used with Liquid Oxygen (LOX) or Gaseous Oxygen (GOX)
at any pressure or with air at oxygen partial pressures above 34.5 kPa (5 psia).
Rationale
With a few exceptions, common structural metallic materials are flammable in
oxygen at modest pressures. However, most metals can be used safely in
oxygen, provided that the system is designed to eliminate potential ignition
sources.
Recommendation(s):
1. Titanium alloys are extremely flammable and should be used only in
exceptional circumstances.
2. In some applications, use of Titanium (Ti) may be acceptable via a Project
approved waiver process that includes review and approval by both
Materials and Parts Engineering disciplines.
3. Care shall be exercised to ensure that cleaning fluids and other chemicals
used on titanium are not detrimental to performance or reliability. Surface
contaminants which can induce stress corrosion, hydrogen embrittlement,
or reduce fracture toughness include the following: hydrochloric acid,
cadmium, silver, chlorinated cutting oils and solvents, methyl alcohol,
fluorinated hydrocarbons, and components containing mercury.
Zinc (Zn)
Zinc plating shall not be used on EEE parts and connector hardware in critical
applications.
Rationale:
1. Zinc is known to sublimate in a vacuum environment, especially at elevated
temperatures. The sublimation products are conductive and can result in
short circuits.
2. Electrically-deposited zinc (Zn) coatings have been shown to exhibit
spontaneous metallic whisker growth that appears to be more aggressive
than that observed with electrically-deposited bright tin (Sn).
3. The propensity for whisker growth and the possibility of microscopic metallic
fiber FOD presents a serious reliability and health concern.
4. Zinc whiskers are capable of causing electrical failures ranging from
parametric deviations to sustained plasma arcing that can result in
catastrophic short circuits.
Recommendation(s):
In some applications use of Zinc plating may be acceptable via a Project
approved waiver process that includes review and approval by both Materials and
Parts Engineering disciplines.
1. Zinc (galvanized) plating is occasionally used on mechanical hardware such
as fasteners for its corrosion resistant properties. By using alternative plating
materials most designs can avoid the risks associated with the use of Zinc
plating while still achieving suitable corrosion resistance.
2. Consult your materials or parts specialists for suggested alternatives to Zinc
plating.
Radiation
Cross- To reduce the risk of fluorine attack (White Plague), when fluoropolymer-insulated
Linked Tefzel (XL- silver-coated copper wiring is either stored in sealed packaging (e.g.: vapor-proof
TEFZEL, XL-ETFE)
bagging, MBB) or used in enclosed environments / compartments, the fluorine
evolution rate shall not exceed 20 PPM when tested in accordance with SAE
AS4373 Method 608, Fluoride Offgassing.
Lock Washers (Star Lock washers with a “star” or “tooth” locking feature have a potential to create
Foreign Object Debris (FOD) and shall not be used in critical applications.
and Tooth Type)
(163)
Rationale: Lock washers with a “star” or “tooth” locking feature have a potential to
create Foreign Object Debris (FOD) that may create an acute eye and laceration
injury electrical short hazard.
Recommendation(s):
Fasteners requiring a lock washer should use a split washer design.
Silver-Coated Copper Silver-coated copper conductors (e.g.: wiring, shielding, terminations, etc.) with
Wire With Less Than less than 40 micro-inches of silver coating shall not be used in critical
40 Micro-Inches of applications.
Silver Coating
Rationale:
Inadequate silver plating thickness and uncontrolled environmental exposure can
result in wire corrosion, known as “Red Plague.”
Recommendation(s):
The use of silver-coated copper conductors (e.g.: wiring, shielding, terminations,
etc.) shall require the implementation of a User-approved Red Plague Control
Plan (RPCP) to reduce and control exposure to environmental conditions and
contamination that promote the development of cuprous oxide corrosion (Red
Plague) and latent damage.
See Appendix B “Red Plague Control Plan (RPCP)” for technical guidance.
Parylene (Paraxylene)
Coatings Containing
Chlorine
Parylene-C coatings may corrode metals or form undesirable electrically
conductive substances shall not be used in critical applications.
Rationale:
Parylene (Paraxylene) coatings containing chlorine may corrode metals, or form
undesirable electrically conductive substances when subjected to high heat or
contact with flame.
Outgassed products are hazardous and corrosive.
Natural Rubber
Materials
Natural rubber materials shall not be used in critical applications.
Rationale:
Natural rubber materials outgas sulfur when subjected to heat, low pressure, or
vacuum conditions; have limited resistance to extreme temperatures, sunlight, or
ozone; are fungus nutrients; and, exhibit significant compositional variation from
batch to batch.
Acetic Acid Cure RTV Acetic acid cure RTV silicone sealants, adhesives, and coatings shall not be
Silicone
Sealants, used in the assembly or manufacture of electrical wiring harnesses and cable
Adhesives,
and assemblies or as environmental sealants for electrical enclosures (e.g.: conduit,
Coatings
fittings, boxes, etc.).
Rationale:
Release of acetic acid during cure of Room Temperature Vulcanizing (RTV)
silicones creates potential corrosion and contamination.
MIL-DTL-16878
Aromatic KaptonInsulated Wiring
WIRE - KAPTON INSULATED (ALL SLASH SHEETS)
MIL-HDBK-454 states that MIL-DTL-16878 wire shall not be used for Air Force
or Navy aerospace or NASA applications. In addition, the ordering requirements
for these specifications are inadequate to ensure that the wire, plating, and
insulation will satisfy flight requirements.
Sulfides or Free Sulfur Materials containing or coated with substances known to be detrimental to
metals used in electrical connectors or optics shall not be used adjacent to
exposed electrical contact or optical surfaces.
The use of materials containing or coated with sulfides or free sulfur is
prohibited.
APPENDIX D - FOREIGN OBJECT DEBRIS (FOD) CONTROL
Number:
Revision
D-1
PROTECTION FROM FOREIGN OBJECT
DEBRIS (FOD)
Page
Date:
1 of 1
Note: Appendices to IPC-D-620 are not binding, unless separately and specifically included by
the applicable contract, approved drawing(s), or purchase order.
STATEMENT OF STANDARD
A Foreign Object Debris (FOD) prevention program shall [N1N2A3] be established for the design,
development, manufacturing, assembly, repair, processing, testing, maintenance, operation, and
check out of the equipment to prevent immediate and latent damage and to ensure the highest
practical level of cleanliness.
a. Cable and wiring harness assemblies shall [N1N2A3] be designed with debris-proof covers,
shrouds, containers, housings, potting, or conformal coatings that protect the entire system prior to
use, or that prevent debris from entering into critical areas of the mechanism where the debris
could cause arcing, binding, jamming, seizing, or unwanted current paths.
b. Connectors not being actively assembled shall [N1N2A3] be individually protected by wrapping
them in bubble pack or other physical covering (i.e.: clean, ESD-rated dust caps, etc.).
c.
Clean, ESD-rated dust caps shall [N1N2A3] be installed on all unmated connectors.
d. Interim Assembly / Temporary Storage - Wiring, cable, connectors, and harness assemblies that
are not being actively worked on shall [N1N2A3] be stored in water-vapor-proof packaging, or
covered by Electrostatic Discharge (ESD) protective covering in accordance with ANSI/ESD
S20.20 and stored in an environmentally-controlled and monitored area where dew point is not
attained and the relative humidity is less than 70%RH.
If necessary, connectors that were subjected to frequent mating and demating operations during
fabrication and test shall [N1N2A3] receive additional cleaning prior to the final mating. Visual
examination of the contact surfaces of connectors shall [N1N2A3] not reveal the presence of
contaminants such as metal flakes or large dust particles. If required, additional cleaning should
be performed by vacuum removal methods and solvent-brushing.
e. After harness fabrication is complete and certified, the complete harness shall [N1N2A3] be
cleaned with an approved solvent, inspected with both black and white light and then vacuum
baked (bakeout) at a temperature of +20°C above the maximum environmental test temperature.
The bakeout will continue until a chamber pressure of 1X10-6 Torr is reached and the QCM
requirements have been fulfilled.
f.
Completed Assemblies - Completed cable and harness assemblies shall [N1N2A3] be placed in a
sealed, vapor-proof, protective bag, with desiccant and a humidity indicator card (HIC). Clean,
ESD-rated dust caps shall [N1N2A3] be installed on all unmated connectors.
g. Cleaning The Harness Assembly - Particles and debris shall [N1N2A3] be cleaned from the
harness or cable assembly by vacuum-removal methods. Solvent brushing with solvent, or wiping
with a clean lint free cloth and an approved solvent may be used as required to remove other
contamination. Under no circumstances should the harness assembly be submersion cleaned,
and aqueous solvents (water-based) should not be used in instances where the wiring is silvercoated copper.
h. Cleaning Harness Connectors - The following cleaning procedures shall [N1N2A3] be used with
connectors:
(1) For solder-type connectors, flux rundown into the mating part of socket contacts shall
[N1N2A3] be removed (Requirement). Solvent cleaning by brushing may be used. Contact
surfaces of pins, sockets, and connector bodies shall [N1N2A3] be free of flux residue (see
Figure 15-1), solder splash, metal flakes, moisture, and other contaminants that may
jeopardize the integrity of the connector system.
(2) Crimp-type multi-pin and coaxial electrical connectors should be solvent-cleaned by brushing
before assembly to the harness or unit cable. Contact surfaces of pins and sockets and the
interior surfaces of the connector shall [N1N2A3] be free of contaminants.
i.
Cleaning Connector Covers - The internal surfaces of dust covers and connector covers shall
[N1N2A3] be cleaned by solvent brushing and allowed to air dry before the covers are fitted onto
cleaned connectors.
j.
Cleaning Coaxial Connectors (Assembled) - Coaxial connectors shall [N1N2A3] not have
accumulated contaminants such as metal flakes, dirt, moisture, and other foreign materials. The
connector interface shall [N1N2A3] be cleaned by brushing with solvent, vacuum procedures, or
a combination thereof until the contaminants have been removed.
k.
Metallic Braid - All tubular metallic braid shall [N1N2A3] be cleaned with an approved solvent
before being incorporated into the harness. Aqueous (water-based) solvents shall not [N1D2A3]
be used.
l.
The FOD prevention program shall [N1N2A3] conform to NAS 412 "Foreign Object Damage/
Foreign Object Debris (FOD) Prevention".
REMARKS
Overbraid / metallic tubular braid shielding must be cleaned to remove the oils and the tarnish
inhibiters used during the weaving process. While use of an ultrasonic cleaning process is
recommended, a manual process of three immersion-removal-drain cycles (with a gentle agitation by
hand while immersed) with room temperature isopropyl alcohol (IPA) should be sufficient. The third
cycle should be clean IPA and used as a final rinse. Once dried, the braid should be visibly inspected
at 4X-10X magnification to verify it is clean, particulate free, and should not have a sticky / tacky feel
when touched.
Silver-coated copper braid should not exhibit visible indications of Red Plague (a dusty reddish / pink
tint at the intersections of braid weave).
Aqueous (water-based) solvents / cleaning processes shall not be used if the braid is silver-coated
copper (commonly used for flight hardware), as this may promote Red Plague.
APPENDIX E - ELECTRICAL WIRE AND CABLE ACCEPTANCE TESTS
Number:
Revision
APPENDIX E
ELECTRICAL WIRE AND CABLE
ACCEPTANCE TESTS
Page
Date:
1 of 1
STATEMENT OF STANDARD
Electrical wire and cable, including wiring used within containerized electrical / electronic assemblies
("black boxes") shall [N1N2A3] be procured and acceptance tested to the appropriate cable
specifications listed below:
•
Cable specification ANSI/NEMA WC27500, Standard for Aerospace and Industrial Electrical
Cable.
•
Cable specification MIL-C-17, Cables, Radio Frequency, Flexible and Semi-rigid.
•
Wire specification AS22759, Wire, Electrical, Fluoropolymer Insulated Copper or Copper Alloy
•
Other wire procurement specifications may be authorized by the USER.
•
Wire and cable shall [N1N2A3] also comply with applicable Materials and Process (M&P)
requirements.
If the wiring used in any application is unknown, as it may be in the case of off-the-shelf equipment,
pig-tailed components, heater strips, etc. and if the application is non-critical, the assembly is required
only to meet applicable program materials and process requirements.
Two methods for certifying wire are:
a. As required by the procurement specification, Government Source Inspection (GSI) shall
[N1N2A3] certify that the test specified below has been performed by the wire manufacturer on
the length of wire procured. In addition to meeting the requirements of the appropriate
procurement specification, each shipment shall be accompanied by the manufacturer’s test report.
b. Wire certification can also be performed by a USER-approved test facility.
In either case, testing shall [N1N2A3] consist of the tests below. Testing for insulation flaws of
cable’s basic wires shall [N1N2A3] be done prior to cable assembly.
100-Percent Testing
a. Insulated single conductor wires and cable basic wires
(1) Impulse dielectric test (no greater than 80% of military specification)
b. Cable
(1) Dielectric withstand of component wires
(2) Jacket flaws for shielded cables
Sample Testing
As a minimum, a sample or samples of each lot of wire/cable shall [N1N2A3] be subjected to the
following applicable quality conformance inspections. (Applicability is determined by the specifications
cited above).
1. Insulated single-conductor wires and cable basic wires
a. Conductor resistance
b. Wrap test
c. Shrinkage (heat resistance)
d. Cold bend followed by wet dielectric
e. Visual and mechanical examination (finished wire O.D., identification of product, conductor
diameter, strand diameter, conductor stranding, wire base metal, and the plating material)
f. Polyimide cure test (applicable to modified aromatic polyimide coatings only)
g. Cross-link proof testing for cross-linked insulation materials
2. Cable
a. Shield coverage
b. Identification of product
c. Jacket wall thickness
d. Cold bend
e. Thermal shock
f. Stress-Crack Resistance testing (MIL-C-17 Cable only)
Any failure during sample testing shall [N1N2A3] be cause for immediate rejection of the entire lot.
Certification Processes
Certification of a USER-approved test facility is done by an audit team with representatives from the
USER, or their representatives. The team shall [N1N2A3] assure the test lab is qualified to perform
the test methods referenced in this standard.
At the using installation, before placing wire/cable into bonded storage, representatives from the
Engineering team and/or receiving inspection function shall [N1N2A3] verify that the test report
indicating conformance with all applicable procurement specification requirements accompanies each
lot shipped.
Storage shelf life: Silver plated wire and cable that has exceeded a shelf life of 10 years from its
manufacturing date shall [N1N2A3] be downgraded to non-flight status and not be used on flight
hardware.
REMARKS
The primary reason for downgrading silver-coated wire after ten (10) years of age is to control
increased solderability problems with silver and the potential for Red Plague for wire stored in a high
moisture environment. See Red Plague Control Plan (RPCP), Appendix A.
APPENDIX F – BEND RADIUS
Number:
Revision
Page
Date:
BEND RADIUS
1 of
STATEMENT OF STANDARD
Optimum
Bend Radius
(O.D.) [1]
Minimum
Bend Radius
(O.D.) [1]
Space between
constraint point
to start of bend
(O.D.) [1], [4]
Bare bus or enamel-insulated wire
3
2
2
Cat5 Ethernet
10
4
2
Coaxial Cable, Flexible [2]
10
6
6
Coaxial Cable, Fixed [3]
10
6
6
Coaxial Cable (Rigid)
3.5
2
6
Coaxial Cable (Semi-Rigid)
3.5
2
6
Component Lead (Flat)
2
1
0.5mm (0.020 in.)
Component Lead (Round)
2
1
2
Fiber Optic Cable
15
10
10
Fiber Optic Cable (Hybrid)
20
10
10
Fiber Optic, Individual (Tight Buffer / jacketed)
15
10
10
Flat Cable
10
3
3
Flat Cable (Shielded)
10
3
3
Harness (with coaxial cable, fiber optic or individual
conductors 8 AWG or larger)
10
6
6
Harness (with individual conductors 10 AWG or
smaller, no coaxial or fiber optic)
10
3
3
Harness with polyimide (Kapton®) insulated wires
15
10
10
Individual Insulated Conductor
3
2
2
Multi-conductor Cable (Non-Shielded)
10
3
3
Multi-conductor Cable (Shielded)
10
6
6
Polyimide (Kapton®) Insulated
15
10
10
Ribbon Cable
10
3
3
Ribbon Cable (Shielded)
10
3
3
Shield / drain wire [5]
3
3
2
Conductor / Cable Type
Notes:
1. OD is the outer diameter of the wire / cable / harness assembly, including insulation / jackets / shielding.
2. Coaxial Cable (Flexible) - Coaxial cable that is or may be flexed during operation of the equipment.
3. Coaxial Cable (Fixed) - Coaxial cable that is secured to prevent movement; not expected to have the cable
repeatedly flexed during operation of the equipment.
4. Distance from the entrance/exit of the connector or connector accessory, strain relief, tie/strap, support
clamp, or breakout and start/end of the bend (measured as outside of the bend radius).
5. Wires used as shield terminators or jumpers that are required to reverse direction in a harness. Bend
radius is measured at the point of reversal plus constraint dimension, providing the wire is adequately
supported.
REMARKS
APPENDIX G – LEAD-FREE CONTROL PLAN (LFCP)
Number:
Revision
Page
Date:
LEAD-FREE CONTROL PLAN (LFCP)
STATEMENT OF STANDARD
Technical Background
The use of electrical / electronic components and mechanical hardware with a pure-tin or high-tin
content plating finish represents a potentially significant performance and reliability risk that may result
in degradation or loss of function / control over the expected lifetime of the hardware.
Effective control of the performance and reliability
problems related to the use of electrical / electronic
components and mechanical hardware with a pure-tin or
high-tin content plating finish requires a thorough and
complete assessment of the design, risk analysis, and
implementation of mitigation strategies. It should be noted
that despite any claims to the contrary, no single or
combination of mitigation strategies has been
demonstrated to completely prevent the development of
tin whiskers or pest. Even so, the presence of tin
whiskers in electrical / electronic hardware does not
automatically guarantee anomalous operation or
catastrophic failure.
Figure 3
Relay Destroyed by Suspected TinWhisker-Induced-Metal Vapor-Arc
Electrical / electronic components and mechanical
hardware with a pure-tin or high-tin content plating finish
utilized in applications having prolonged or repeated
exposure to temperatures below +13 °C (+56°F), may be
susceptible to a phenomenon known as “Tin Pest” or “Tin
Plague”, where an autocatalytic, allotropic transformation
converts electrically conductive, silver/white-colored
metallic Tin (a.k.a.: beta-tin/β-tin), to a semi-conductive,
gray-colored, crumbly powder (a.k.a.: alpha-tin/α-tin).
Above this temperature, white (β) Tin is the stable form.
The development of Tin Pest represents a potential
performance and reliability risk to spaceflight electronics
and DoD hardware subjected to temperature excursions
conducive to the allotropic transformation of tin.
Figure G-2
Tin Pest on ISS Truss Grounding Strap
(Photo courtesy NASA)
1
PURPOSE
This document prescribes requirements for the control and mitigation of performance and
reliability risks associated with the use of Lead-free Tin (Sn) and Lead-free Tin (Sn)
technology in the manufacture of electrical and electronic assemblies, including optical
and metallic cable and wiring harness assemblies, and elements thereof.
1.1
AUTHORITY
The authority for this document derives from requirement 0.1.6 - Use of Lead-Free Tin of
IPC/WHMA-A-620B-S “Space Applications Electronic Hardware Addendum to
IPC/WHMA-A-620B”, and requirement 0.1.6 - Use of Lead-Free Tin of IPC J-STD-001ES
“Space Applications Electronic Hardware Addendum to IPC J-STD-001E Requirements
for Soldered Electrical and Electronic Assemblies”.
1.2
APPLICABILITY
This document shall not be binding, unless separately and specifically included by the
applicable contract, approved drawing(s), or purchase order.
a. Commercial Off-The-Shelf (COTS). The requirements of this document shall not
apply to commercial off-the-shelf (COTS) items. Projects which use COTS hardware
for applications described above shall be responsible for identifying and managing
risks associated with hardware that was built without a control plan to reduce the
harmful effects of tin whiskers.
b. Existing or Previously Approved Designs. The requirements of this document shall
not constitute the sole cause for the redesign of previously approved designs. When
drawings for existing or previously approved designs undergo revision, they should
be reviewed and changes made that allow for compliance with the requirements of
this document.
1.3
ORDER OF PRECEDENCE
The following shall be applicable in the resolution of conflict between the requirements or
the text of this document; and, applicable documents, and approved / unapproved
engineering documentation in the order indicated:
a. Contract / Program Requirements
b. Engineering Documentation (User-Approved Drawings / Referenced Documents)
c. This Document
d. Engineering Documentation (Applicable Documents / Published IPC Standard)
e. Engineering Documentation (Un-approved Drawings)
f. Verbal Correspondence (ALWAYS get it in writing!)
1.4
APPROVAL OF DEPARTURES FROM THIS DOCUMENT
Any changes, revisions, or deviations to the requirements of this document shall require
technical evaluation and approval by the Lead Free Control Board (LFCB) with the User
having waiver authority.
a. Use of alternate control plans, documents, or processes shall require review and
approval of the Lead Free Control Board (LFCB) and the User prior to use.
b. Less stringent control plans, documents, or processes meeting Level "2B" are allowed
in exceptional cases with the review and recommendation of the Lead Free Control
Board (LFCB) and approval of the User prior to use.
c. Requests for relief from requirements in this document shall require review and
approval of the User prior to use.
1.5
ROLES AND RESPONSIBILITIES
a. Supplier.
The Supplier shall document every incidence of use of lead-free tin
technology in compliance with the requirements of this document. See LFCP Report
for guidance on the minimum documentation and technical rationale content required
for a Lead-Free Control Plan (LFCP).
b. Lead-Free Control Board (LFCB).
The LFCB is the controlling authority for
establishing the configuration baseline for use of lead-free tin technology and
subsequent mitigation(s).The Lead-Free Control Board (LFCB) shall be convened on
an as needed basis as a decision-making forum for the technical review and approval
of requests for:
(1) changes, revisions, or deviations to the requirements of this document
(2) use of alternate control plans, documents, or processes
LEAD-FREE CONTROL BOARD (LFCB)
CO-CHAIR
Process Engineer (Supplier)
CO-CHAIR
Special Processes (Supplier)
EEE Parts Lead (1)
(Supplier)
Materials & Processes Lead (1)
(Supplier)
Quality Engineering Lead (1)
(Supplier)
User (1)
(Full Waiver Authority)
(1): Or designated alternate
Figure G-3: Typical Lead-Free Control Board (LFCB)
2
APPLICABLE DOCUMENTS
The following documents are applicable to the extent specified herein. The applicable
revision shall be that identified herein or the revision in effect on the date of the contract
or work authorizing document.
2.1
MILITARY STANDARDS
<None>
2.2
INDUSTRIAL STANDARDS
2.3
GEIA-STD-0005-1
Performance Standard for Aerospace and High
Performance Electronic Systems Containing Lead-free
Solder
GEIA-STD-0005-2
Standard for Mitigating the Effects of Tin Whiskers in
Aerospace and High Performance Electronic Systems,
Control Level 2C
GEIA-STD-0006
Requirements for Using Solder Dip to Replace the Finish on
Electronic Piece Parts
IPC-1601
Printed Board Handling and Storage Guidelines
IPC J-STD-001E-2010
Requirements for Soldered Electrical and Electronic
Assemblies
IPC J-STD-001ES
Space Applications Electronic Hardware Addendum to IPC
J-STD-001E Requirements for Soldered Electrical and
Electronic Assemblies
IPC/JEDEC J-STD-020D.1
Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices
IPC/JEDEC J-STD-033C
Handling, Packing, Shipping and Use of Moisture / Reflow
Sensitive Surface Mount Devices
IPC/WHMA-A-620B-S
Space Applications Electronic Hardware Addendum to
IPC/WHMA-A-620B
REFERENCE DOCUMENTS
The documents listed below provide technical guidance which may be helpful to readers of
this document. Unless otherwise specified, the requirements and recommendations in
these documents are not binding.
GEIA-HB-0005-1
Program Management / Systems Engineering Guidelines
for Managing the Transition to Lead-Free Electronics
GEIA-HB-0005-2
Technical Guidelines for Aerospace and High
Performance Electronic Systems Containing Lead-free
Solder and Finishes
GEIA-HB-0005-3
Rework / Repair Handbook to Address the Implications of
Lead-Free Electronics and Mixed Assemblies in Aerospace
and High Performance Electronic Systems
GEIA-STD-0003
Long Term Storage of Electronic Devices
IPC/JEDEC J-STD-609
Marking and Labeling of Components, PCBs and PCBAs to
Identify Lead (Pb), Pb-Free and Other Attributes
IPC-QL-653A
Certification of Facilities that Inspect / Test Printed Boards,
Components, and Materials
MIL-D-3464E
Desiccants, Activated, Bagged, Packaging, Use and Static
Dehumidification (Type II)
MIL-HDBK-338B
Electronic Reliability Design Handbook
MIL-STD-2073-1E
Standard Practice for Military Packaging (Method 50)
MS20003C
Indicator, Humidity, Card, Three Spot, Impregnated
Areas (Cobaltous Chloride), 30-40-50% RH
NASA-STD-8739.1A
Workmanship Standard for Polymeric Application on
Electronic Assemblies
Metallurgical Assessment of Spacecraft Parts, Materials and Processes, Barrie D. Dunn,
Wiley-Praxis,1997, ISBN 0-471-96428-X
3
LEAD-FREE CONTROL PLAN (LFCP)
The use of lead-free Tin (Sn) technology shall be prohibited unless documented and
controlled through a User-approved Lead Free Control Plan (LFCP) in conformance with
Control Level 2C requirements of GEIA-STD-0005-2, "Standard for Mitigating the Effects
of Tin Whiskers in Aerospace and High Performance Electronic Systems", or as directed
by the engineering documentation, and reviewed and approved by the LFCB and User
prior to implementation.
The use of lead-free Tin (Sn) technology in applications with exposure to temperatures at
or below -30°C (-22°F) shall be prohibited unless controlled through mitigation (see
3.2.6).
3.1
LEAD-FREE TIN (Sn)
For the purpose of this document, lead-free Tin (Sn) is defined as metallic Tin (Sn)
containing less than 3 percent lead (<3% Pb) by weight as an alloying constituent. Leadfree Tin (Sn) technology is defined as electrical / electronic components and associated
mechanical hardware and materials composed of, or coated / plated (internal / external
surfaces) with metallic Tin (Sn) containing less than 3 percent lead (<3% Pb) by weight as
an alloying constituent.
Lead-free Tin (Sn) technology shall include:
•
Lead-free Tin (Sn) coatings, platings or metallization on external surfaces of EEE
components, mechanical parts, or assemblies; or, on internal cavity surfaces of EEE
components (i.e.: hybrid, relay crystal cans, MEMS etc.).
•
Lead-free Tin (Sn) solder alloys containing less than 3 percent lead (<3% Pb) by
weight as an alloying constituent. Exception: Sn96.3Ag3.7
•
Wiring technology (i.e.: wire, cable, connectors, terminators, clamps, braid / over-braid
shield, etc.) composed of, or coated / plated with, metallic Tin (Sn) containing less
than 3 percent lead (<3% Pb) by weight as an alloying constituent.
•
Any EEE components, electrical / electronic assembly, printed wiring assembly
(PWAs), cable assembly, and/or wire harness assembly assembled with lead-free tin
solder alloy except high temperature solder alloy Sn96.3Ag3.7 (Sn96A).
Note: Sn96.3Ag3.7 shall only be used where specifically indicated by approved drawings.
3.2
MINIMUM REQUIREMENTS
At a minimum, the Lead Free Control Plan (LFCP) shall:
a. Avoid the use of lead-free Tin (Sn) technology whenever possible.
b. Document every incidence of lead-free tin technology and prevent its use without prior
review and approval of the LFCB. The documentation shall include a list of each
individual piece part with a Pb-free tin-finished surface and a description of the finish
composition, and a list of what applications will include that piece part.
c.
Incorporate a minimum of two (2) mitigation measures when the lead-free tin finish is
not completely replaced through a replating or hot solder dip (HSD) process.
d. Include any special design requirements, mitigation measures, test and qualification
requirements, quality inspection and screening, marking and identification,
maintenance, and repair processes.
3.2.1
LEAD-FREE CONTROL LEVEL DESIGNATION
The lead-free control level shall be set when all other project requirements are being
determined. The default lead-free control level shall be 2C.
3.2.2
LEAD-FREE TIN IDENTIFICATION AND REPORTING
For Control Levels 2C (or higher), the LFCP shall require X-ray fluorescence (XRF) or
similar testing of all parts with external surfaces that appear similar to tin in color and
texture (i.e. matte nickel, silver, etc.).
3.2.3
TIN WHISKER RISK DOCUMENTATION
The LFCP shall require an assessment of risk consistent with GEIA-STD-0005-2.
3.2.4
TIN WHISKER MITIGATION
Lead-free Tin (Sn) technology, which by package design or engineering decision prevents
/ prohibits protection by SnPb replating or Hot Solder Dip (HSD), shall be protected by at
least two (2) process or design mitigation techniques to reduce or eliminate the risks
created by metallic whisker formation and/or tin pest in the expected end-use application /
environment.
Mitigation is a systematic engineering approach to the control of risk. When considering
any mitigation strategy, the engineering function must assess the applicability, strengths
and weaknesses of the specific technique being employed. Use of mitigation techniques
shall require technical review and approval by the LFCB prior to implementation.
3.2.4.1
DESIGN
An evaluation of the relative risk of actively mitigating metallic whisker growth must be
part of the design process when the availability of components is limited to lead-free tin
finishes. This shall include an analysis to determine if the risk of whisker development is
partially mitigated by the design and topography of the hardware, spacing between
electrically uncommon conductive surfaces, or choice of finish.
a. Design and Topography.
Components, sub-assemblies, assemblies, and
mechanical hardware identified as having a lead-free tin finish shall be physically
positioned or mechanically isolated by board strengtheners, brackets, or other nonconductive components / structures to ensure the growth of conductive whiskers does
not adversely affect hardware performance or reliability.
b. Spacing.
Direct line-of-sight spacing between electrically uncommon conductive
surfaces shall be sufficient to ensure whisker growth rates (1mm/yr. nominal) over the
life of the mission do not violate minimum electrical spacing requirements.
c.
3.2.4.2
Finish - Adjacent Surfaces.
Surfaces adjacent to components, sub-assemblies,
assemblies, and mechanical hardware identified as having a lead-free tin finish shall
be finished with a non-electrically conductive coating.
HOT SOLDER DIP (HSD)
The Hot Solder-Dipping (HSD) process for tin whisker and tin pest mitigation differs from
the solder tinning process for solderability (ref: J-STD-001E [4.3, 4.4]) in that all exposed
surfaces of the lead-free tin plated conductors - up to the body-lead seal – are replated
with tin-lead (SnPb) solder alloy. Because the HSD process exposes components to
significant thermal stress, the process shall be repeatable, controlled, not introduce
immediate or latent damage, or degrade the performance of the component.
A device shall no longer be considered to be lead-free tin finished if all lead-free tin
finishes are replaced through a replating or hot solder-dipping (HSD) process with a SnPb
alloy having a minimum of 3% lead (Pb) by weight.
The HSD process shall wet and replace all exposed surfaces of the conductors with a tinlead (SnPb) alloy having a minimum of 3% lead (Pb) by weight. This will involve
immersion plating up to the body lead seal, and will require verification that the process is
controlled and does not introduce immediate or latent damage, or degrade the
performance of the component.
a. HSD solder alloy shall be Sn60Pb40, Sn62Pb36Ag02 or Sn63Pb37. Other alloys
may be used with prior approval from the User (See J-STD-001ES [3.1] / IPC/WHMAA-620B-S [4.1.1.2]).
b. Flux chemistry shall be ROL0 (R) or ROL1 (RMA). ROL2 (RA) or other chemistries
may be used with demonstration of process control, cleanability, and prior approval
from the User (See J-STD-001ES [3.1] / IPC/WHMA-A-620B-S [4.1.1.2]).
c.
Components shall be preheated prior to solder immersion to minimize thermal shock.
Thermal ramp rates shall not exceed the following, unless specified by engineering
documentation:
(1) Ramp-up: Not greater than +4°C / sec. (+7.2°F / sec.)
(2) Ramp-down: Not greater than -6°C / sec. (-10.8°F / sec.)
d. Solder immersion of conductors, terminations, or leads shall not exceed 5 seconds
duration. Duration of molten solder contact with the body-lead seal shall be
minimized but shall be sufficient to ensure full and complete wetting of the entire
conductor / termination / lead surface (generally less than 3 seconds maximum).
e. All components shall be properly cleaned, visually inspected per J-STD-001ES [4.2.3]
and [11.2.2], and demoisturized per IPC-1601, J-STD-020D, J-STD-033C, or other
demoisturization schedule approved by the User.
3.2.4.2.1
PRETINNING (PARTIAL HSD MITIGATION)
The pretinning process used to comply with
solderability requirements (ref.: J-STD-001E
[4.3], is recommended as an alternative to Hot
Solder Dip (HSD) only in cases where the
hardware design prohibits implementation of
Hot Solder Dip (HSD). It is considered a
partial mitigation because only the portions of
the lead-free tin-finished surfaces designated
to be part of the completed solder termination
are replaced with SnPb alloy.
Figure G-4
The remaining exposed lead-free tin finish
Partial HSD Mitigation - Tin Whisker Risk
between the pretinned section of the
(Note whiskers above plating edge)
component lead and the body-lead seal has
the potential for whisker development and
shall be protected by an additional mitigation, such as conformal coating, embedment /
encapsulation, or surveillance (inspection, functional test, etc.).
3.2.4.3
CONFORMAL COATING
External surfaces, platings, metallization, etc., with a lead-free Tin (Sn) finish shall be fully
coated with conformal coating with a total cured finish thickness of not less than 100 μm
[0.004 in.] for silicone (SR) and urethane (UR), and not less than 50 μm [0.002 in.] for
paraxylene coatings. Total cured finish thicknesses specified shall take precedence over
requirements imposed by J-STD-001(SPACE) [Table 10-1], or other user-approved
conformal coating / polymeric standard.
a. Spray or Brush Application. Spray-applied or hand-brush-applied conformal coating is
viewed as a significant mitigation tool as it increases environmental resistance,
retards the development and propagation of whiskers, and serves as an insulative
barrier to Foreign Object Debris (FOD). However, spray or hand-brush application
may only be capable of achieving partial coverage for complex PWA designs, as the
spray and hand-brush processes only coat the visibly exposed surfaces, with some
minor capillary flow under component bodies. This leaves the most whisker prone
areas of the assembly exposed, such as the backside of component leads and leads
located completely underneath component bodies (i.e.: BGA, flip chip, etc.).
b. Dip Coating. Dip coating, if performed correctly, will ensure the polymer flows under
and around all package types and terminations, producing a coating that wets all
surfaces. Using a low viscosity material and a slow submersion rate at a 30 – 45
degree angle will reduce the incidence of voiding (bubbles). Although there is always
some bridging of fine pitch component leads if a dip coat process is used, a slow and
steady withdrawal rate is recommended to minimize the effect.
c.
Chemical Vapor Deposition. Of all the conformal coating processes, Paraxylene
Resin (XY) is considered the best coating for mitigation against whisker growth
because it coats all exposed surfaces of the PWA with a stress-free, pin-hole free,
uniform thickness of material, including the backside of component leads and leads
located completely underneath component bodies (i.e.: BGA, flip chip, etc.).
d. Effectiveness. The effectiveness of conformal coating as a whisker mitigation
technique depends heavily on the coating material selected, application method,
process control, and workmanship.
(1) Silicone (SR) / Urethane (UR). The use of silicone (SR) or urethane (UR)
conformal coating as whisker mitigation is based on NASA and industry research
indicating that a finish thickness of not less than 50 μm [0.002 in], will increase
environmental resistance, retard the development and propagation of whiskers,
and reduce the potential performance and reliability issues of tin whiskers. This
is accomplished by using the conformal coating as a resilient barrier to trap and
contain a significant portion of whisker growths to within the coating layer, to
reduce or prevent whiskers from contacting and shorting adjacent conductors, to
limit exposure to moisture, and to limit the development of coronal discharge.
(2) Paraxylene (XY). While current research has suggested that a Paraxylene (XY)
coating thickness of greater than 25 μm (0.001 in) will control whisker growth, a
final coating thickness of 50 - 100 μm (0.002 – 0.004 in) is recommended to
provide optimal protection.
Minimum total cured thickness specified for
Paraxylene (XY) may require application of multiple coatings.
3.2.4.4
EMBEDMENT / ENCAPSULATION
Use of embedment and encapsulation as
mitigation is recommended for integrated
circuit, fine-pitch, area array device
packages, and modular assemblies where
conformal coating would have limited
effectivity at coating the surfaces of tightly
spaced component leads (i.e.: IC, QFP,
SOIC, etc.) or the terminations underneath
the component body (i.e.: BGA, flip-chip,
etc.).
The application process is similar to underfill,
in that the embedment / encapsulant material
Figure G-5
Encapsulation of Module
(Photo courtesy NASA)
must flow underneath and completely fill the space between the component body and the
printed wiring board (PWB), then fully wet and cover all termination surfaces. This
requires that the materials be selected to closely match the coefficient of thermal
expansion of the component and printed wiring assembly (PWA). Embedment and
encapsulation is often used selectively and in conjunction with conformal coating, as the
process is considered very labor intensive.
a. Embedment or encapsulant material shall fully wet and cover all surfaces of parts and
areas specified by the approved engineering documentation.
b. Cured material shall be compatible with the hardware and shall not adversely affect
hardware performance or reliability.
3.2.5
SURVEILLANCE (INSPECTION & FUNCTIONAL TEST)
A surveillance program involving visual inspection of a control unit for whiskers, and
functional testing of flight units is recommended as a supplement to other mitigations,
such as SnPb pretinning, conformal coating, etc. The User must recognize and accept
that there is a significant assumption of risk in using this strategy because the control unit
may not be fully representative of the flight units, and a false sense of security can be
generated if no whiskers are observed on the control unit and the flight units pass
functional / acceptance tests. Uncertainty issues that must be taken into consideration
when using this mitigation strategy include:
a. Inspection for whiskers requires extensive and repetitive handling of the hardware;
stereo-optical vision with a magnification power of 20X minimum; polarized, variableintensity light sources; and, an ability to rotate the hardware 360 degrees around a
fixed viewing axis point during inspection. Standard inspection stations with
fluorescent light-rings are incapable of performing this task and shall not be used.
b. Functional and acceptance testing only verifies that hardware performance has not
degraded to a level detectable by the test. As such, the tests should not be used as
“certification” that the tested hardware is whisker-free – only that the hardware was
functional at the time of test.
c.
3.2.6
Limited Life Article. Class 3 (high performance or performance-on-demand) hardware
incorporating lead-free tin surfaces, platings, metallization, etc., but which by package
design or engineering decision are not protected by SnPb replating or HSD, with a
storage or flight life of ten (10) years from its assembly date, should be identified and
tracked as a Limited-Life Article, and subjected to visual inspection and functional test
prior to use.
TIN PEST (TIN DISEASE) MITIGATION
Lead-free Tin (Sn) and Lead-free Tin (Sn) technology shall not be used in applications
with exposure to temperatures at or below -30°C -22°F), unless combined with one of the
following alloys by weight percentage:
a. Not less than 5 percent lead (Pb)
b. Not less than 0.3 percent bismuth (Bi)
c.
Not less than 0.5 percent antimony (Sb)
d. Not less than 3.5 percent silver (Ag)
4
ACRONYMS AND TERMS
For purposes of this document, the following additional acronyms, abbreviations, and
terms are listed in addition to those listed in IPC-T-50J, “Terms and Definitions for
Interconnecting and Packaging Electronic Circuits”.
Acronym
COTS
Definition / Term
Description
Commercial Off-The-Shelf
Items (i.e.: modules, assemblies, etc.) offered
without modification and available from a
vendor catalog or stock for sale, lease, or
license in substantial quantities in the
commercial / consumer marketplace.
Conformal Coating
A thin and electrically non-conductive coating
which conforms to the contours of the PWA to
provide protection against condensing moisture
and incidental contact (splash) water, Foreign
Object Debris (FOD), and other environmental
contamination.
Control Level 2B
For Level 2B hardware, these control plans may
cover families of piece part types or
applications. Separate assessments and control
plans for each individual item are not required.
For example, one assessment might allow use
of all tin-plated capacitors in a variety of
applications.
Control Level 2C
A
GEIA-STD-0005-2
selection
protocol
requiring the identification, risk assessment, and
controlled
use
of
electrical/electronic
components, assemblies and mechanical
hardware with Pb-free final finishes / platings,
underplating, base metals, solder; either
external or internal to an assembly, component,
printed wiring board, or other hardware
composed of lead-free tin.
Criticality
The FMEA categorization of a failure mode
based on the worst case potential failure
effect, regardless of probability of occurrence.
E/E
Electrical / Electronic
Assembly
Any configuration of discrete and/or integrated
electrical, electronic, and/or electro-mechanical
components; sub-assemblies; Printed Wiring
Assemblies (PWA); discrete wiring, cabling, or
harnesses; fiber optic components, or
combinations thereof, that are joined together
to perform a control or processing function
(i.e.: measurement, sensing, or transmission of
data or power).
EEE
Electrical, Electronic, and
Electromechanical
Embedment
The process of completely encapsulating a
component or module in a resin.
Encapsulation
The encasement of a component in a coating
by dipping, spraying, or embedding with or
without a mold, to provide mechanical support
and environmental protection.
Engineering
Documentation
Drawings
and
specifications
which
provide
instructions, design features,
requirements, acceptance criteria, and other
documentation to invoke and/or modify
requirements.
Failure Modes and Effects
Analysis
A systematic, qualitative, analysis technique for
the identification of potential failure modes of
components, assemblies, sub-systems and
systems. A FMEA is often the first step of a
system reliability study.
HSD
Hot Solder Dip
A documented and controlled process that
replaces the pure Tin (Sn) plating finish with a
Tin-Lead (SnPb) alloy finish by dipping the
component’s terminations in molten solder up
to the component body lead seal.
i-HIC
Irreversible Humidity
Indicator Card
A specially-designed paper card / strip
containing
moisture-sensitive
chemical
indicators that will permanently change color
when the designated relative humidity (RH)
level is exceeded. An i-HIC is a quality record.
LFCB
Lead Free Control Board
The controlling authority for establishing the
configuration baseline for all Lead-Free Control
Plans (LFCPs).
LFCP
Lead Free Control Plan
A documented process that assures that
Aerospace and High Performance (AHP),
high-reliability electronics systems containing
Pb-free solder and Pure tin (Sn) plated piece
part and board finishes will continue to be
reliable, safe, producible, affordable, and
supportable.
Lead-Free Tin (Sn)
Metallic Tin (Sn) containing less than 3 percent
lead (<3% Pb) by weight as an alloying
constituent.
Lead-Free Tin (Sn)
Technology
Electrical / electronic components and
associated mechanical hardware and materials
composed of, or coated / plated (internal /
external surfaces) with metallic Tin (Sn)
containing less than 3 percent lead (<3% Pb)
by weight as an alloying constituent.
FMEA
PWA
Printed Wiring Assembly
The generic term for an assembly that uses a
printed board for component mounting and
interconnecting purposes.
PWB
Printed Wiring Board
The general term for completely processed
printed
circuit
and
printed
wiring
configurations. (This includes single-sided,
double-sided and multilayer boards with rigid,
flexible, and rigid-flex base materials.)
Pure Tin
Metallic tin (Sn) in any form (i.e.: metal,
metallization, plating, solder, etc.), whose
composition is equal to or greater than 99.9
percent tin by weight.
Solder
A nonferrous, fusible metallic alloy used to join
metallic surfaces at temperatures below
+427°C (+800°F).
Tin Pest (Tin Disease)
The autocatalytic, allotropic transformation of
the element Tin (Sn) from an electrically
conductive, silver/white-colored metallic Tin
(a.k.a.: beta-tin/β-tin), to a semi-conductive,
gray-colored, crumbly powder (a.k.a.: alphatin/α-tin), when exposed to temperatures below
+13°C (+56°F).
Tin Whisker
Electrically
conductive,
mono-crystalline
structures with an aspect ratio (length/width)
greater than two (2), that grow from surfaces
where tin (especially bright electroplated tin) is
used as a plating finish.
Tin whiskers have been observed to grow at
rates of several millimeters (mm) per year and
in rare instances to lengths in excess of 10
mm. They may be cylindrical, kinked, or
twisted, with smooth, flaky, or striated
surfaces.
As crystalline structures, they are capable of
surviving high mechanical vibration and shock
stresses, and capable of conducting significant
amounts of power before melting or vaporizing.
XRF
X-Ray Fluorescence (XRF) A form of elemental analysis, where the
properties of a material excited by high-energy
X-rays or gamma rays are determined by the
emission of characteristic "secondary" (or
fluorescent) X-rays.
5
LEAD-FREE CONTROL PLAN (LFCP) REPORT
REPORT NUMBER
REVISION
LEAD FREE CONTROL PLAN (LFCP)
REPORT
PAGE
PROGRAM
SYSTEM
PROJECT
CRITICALITY
PROJECT
MANAGER
PHONE
OF
HARDWARE
E-MAIL
PART DESCRIPTION
PART NUMBER(S)
PART SPECIFICATION
ASSEMBLIES USED IN
LFCP CONTROL LEVEL
(GEIA-STD-0005-2)


3
2C

2B*

2A*

1*


0*
LIMITED LIFE*
*JUSTIFICATION FOR USE ( Please provide technical rationale if chosen Control Level is 2B or below)
MITIGATION MEASURES EMPLOYED

DESIGN

HOT SOLDER DIP (HSD)



RATIONALE
PRETINNING (PARTIAL HSD)
 Sn62Pb36Ag02
 Sn63Pb37
 Sn96.3Ag3.7
 OTHER
 Sn60Pb40
 Sn62Pb36Ag02
 Sn63Pb37
 Sn96.3Ag3.7
 OTHER
 SPRAY
CONFORMAL COATING
(MATERIAL)
EMBEDMENT / ENCAPSULATION
(MATERIAL)

SURVEILLANCE
(INSPECTION & FUNCTIONAL TEST)

 Sn60Pb40
 BRUSH
 DIP
 CV DEPOSITION
DESCRIBE
DESCRIBE
OTHER (PLEASE SPECIFY)
ADDITIONAL NOTE(S)
LFCB DISPOSITION
PROCESS ENGINEERING
SPECIAL PROCESSES
EEE PARTS
QUALITY ENGINEERING
MATERIALS & PROCESSES
USER
RESOLUTION (SELECT)
DATE
 APPROVE
 REJECT
EFFECTIVITY
 DEFER
 MEMO
STOP!!