Design for Affordability
How to design for reliability and the importance and cost benefits of
designing in reliability early in the life cycle.
SMTA Nutmeg Chapter Tech Expo
November 16, 2011
Walter Tomczykowski
Outline
o
o
How is Design for Affordability (DfA) defined?
Design for Affordability Enablers
o
o
o
o
2
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Design for Reliability
Design for Manufacturability
Design for Supportability
Summary
2004 - 2010
2007
Design Costs
Reduce Costs by Improving
Reliability Upfront
3
©
2004 - 2010
2007
Design Costs
o
Traditional OEMs
spend almost 75%
of product development
costs on test-fail-fix
o
Electronic OEMs that use design analysis tools shorten
or eliminate this feedback loop
o
o
o
Hit development costs 82% more frequently
Average 66% fewer re-spins
Save up to $26,000 in re-spins
Gene Allen and Rick Jarman .Collaborative R&D; (New York John Wiley&Sons. Inc. 1999). 17.
Aberdeen Group, Printed Circuit Board Design Integrity: The Key to Successful PCB Development, 2007 http://new.marketwire.com/2.0/rel.jsp?id=730231
4
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2004 - 2010
2007
Why DfA? Total Costs are Determined During Design
95% of the O&S Cost Drivers are Based on Decisions Made during Design.
Source: Architectural Design for Reliability, R. Cranwell and R. Hunter, Sandia Labs, 1997
© 2004 - 2010
2007
5
Timeline



Implement “Design for” Early
Simultaneously optimize the design
Conduct gating activities (design reviews)
© 2004 - 2010
2007
Functional
Performance
Design for
Reliability
Design for
Manufacture
Design for
Supportability
6
Design for Affordability (DfA)
o
The decisions made during the design and development
process greatly influence the ultimate life cycle costs
experienced by end users.
o
DfR Solutions defines Design for Affordability as a
comprehensive design strategy that includes:
o
o
o
o
o
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2004 - 2010
2007
Design for Reliability (DfR)
Design for Manufacturability (DfM)
Design for Supportability (DfS)
DfA =
𝑀𝑖𝑙𝑒𝑠𝑡𝑜𝑛𝑒 𝐶
𝐷𝑓𝑅
𝑀𝑖𝑙𝑒𝑠𝑡𝑜𝑛𝑒 𝐴
+ 𝐷𝑓𝑀 + 𝐷𝑓𝑆
= Optimized Total Ownership Cost
Optimized Total Ownership Cost ???
© 2004 - 2010
2007
8
Design for Reliability (DfR)
© 2004 - 2010
2007
9
What is Design for Reliability (DfR)?
o
Reliability is the measure of a product’s ability to
o
o
o
o
Design for Reliability is a process for ensuring the
reliability of a product or system during the design
stage before physical prototype
o
10
©
2004 - 2010
2007
…perform the specified function
…at the customer (with their use environment)
…over the desired lifetime
Often part of an overall Design for Excellence (DfX)
strategy
Toyota Approach


Toyota's development engineers have been
4X as productive as U.S. counterparts.
Why?


o
Focus on learning as much as possible
Use of that knowledge to develop a stream of excellent products
Western engineers
o
o
o
o
o
© 2004 - 2010
2007
Define several product concepts
Select the one that has the most
promise
Draw up specifications and divide
them into subsystems;
Subsystems are designed, built and
rolled up for system testing.
Failures? Rework the specs and the
designs accordingly (non-optimized
and confusing endeavor)
o
Toyota engineers
o
o
Efforts concentrated at lowest
possible design level
Thorough understanding of the
technology of a subsystem so it can
be used appropriately in future
designs
11
Toyota Example: Radiators
o
Traditional approach: Design radiator for a specific vehicle based
on mechanical specifications written for that vehicle
o
Toyota considers a range of radiator solutions based on cooling
capacities and the cooling demands of various engines that might
be used.
o
o
Toyota's system is "test & design" rather than the traditional "design
& test."
o
12
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2004 - 2010
2007
How the radiator actually fits into a vehicle would be kept loose so that
Toyota's knowledge of radiator technology could be used to create the
optimum design
Toyota engineers test at the fundamental knowledge level so they don't
have to test at the later, more expensive stages of design and
prototyping
Why the Automotive Industry Is Using More Virtual Computer Aided Engineering Methods
o
Growing complexity and vehicle electrification
prompting a major change in design processes.
o
Intense competitive pressure to improve efficiency
& effectiveness to shortened development cycles
and reduce costs.
o
The combination of physical and virtual testing
accelerates the product development process
by early identification of deficiencies.
o
Physics based models makes it easier to try out
new designs, since evaluations can be performed
without building physical prototypes.
o
Simulations can be created and run in far less time &
cost than building and testing physical prototype,
models can than be quickly revised to evaluation
alternative configurations and option content.
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2004 - 2010
2007
Computer Aided Engineering Advancement Have Enabled
Reduced Dependence on Costly Physical D-B-T-F Testing.
Test
CAE-M&S
As the use of CAE based
modeling & simulation methods
increase, dependence on physical
testing can be reduced and
refocused.
By 2004 GM was able to reduce vehicle road testing to the point that the southern portion of their
Mesa Az. Proving Grounds was sold. In 2006 the remaining northern 5 square miles, that formerly
operated with 1,200 people, was sold for Real Estate Development.
GM now operates with a much smaller DPG in Yuma Az.
and realized a significant reduction in structural costs.
© 2004 - 2010
2007
14
What is Design for Reliability (DfR)?
o
Reliability is the measure of a product’s ability to
o
o
o
o
Design for Reliability is a process for ensuring the
reliability of a product or system during the design
stage before physical prototype
o
15
©
2004 - 2010
2007
…perform the specified function
…at the customer (with their use environment)
…over the desired lifetime
Often part of an overall Design for Excellence (DfX)
strategy
Failure Rate
Why is Desired Lifetime Important?
Electronics: Today and the Future
Electronics: 1960s, 1970s, 1980s
Wearout!
No wearout!
Time
© 2004 - 2010
2007
16
Design Review: Network Switch
o
Manufacturer of network switches
wanted to understand potential costs of
switch from 3-yr warranty to
lifetime warranty
o
Identified components that could experience wearout
o
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Performed circuit/thermal analysis to identify overstressed components
o
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Especially based on usage model (validated through internal DfR testing)
Predicted reliability for each component based on validated algorithms
o
o
17
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Fans, electrolytic capacitors, integrated circuits, solder joints, plated through
holes, ceramic capacitors, connectors, LEDs, overstressed components
2004 - 2010
2007
Primarily conducted through Sherlock™
Conducted component testing when necessary
PoF and Wearout
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What is susceptible to long-term degradation in electronic designs?
o
o
o
o
o
o
o
o
o
o
o
18
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2004 - 2010
2007
Ceramic Capacitors (oxygen vacancy migration)
Integrated Circuits
Memory Devices (limited write cycles, read times)
Electrolytic Capacitors (electrolyte evaporation)
Resistors (if improperly derated)
Silver-Based Platings (if exposed to corrosive environments)
Relays and other Electromechanical Components
Light Emitting Diodes (LEDs) and Laser Diodes
Connectors (stress relaxation)
Tin Whiskers
Interconnects (Creep, Fatigue)
o
Plated through holes
o
Solder joints
What is Design for Reliability (DfR)?
o
Reliability is the measure of a product’s ability to
o
o
o
o
Design for Reliability is a process for ensuring the
reliability of a product or system during the design
stage before physical prototype
o
19
©
2004 - 2010
2007
…perform the specified function
…at the customer (with their use environment)
…over the desired lifetime
Often part of an overall Design for Excellence (DfX)
strategy
“Let’s Use a COTS Board as a Solution”
20
©
2004 - 2010
2007
Know the Use Environment (Best Practice)
o
Use standards when…
o
o
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Measure when…
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2004 - 2010
2007
Certain aspects of your environment are unique
Strong relationship with customer
Do not mistake test specifications for the actual use
environment
o
21
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Certain aspects of your environment are common
No access to use environment
Common mistake with vibration loads
Failure Analysis of High Power DC-AC Power Inverter
22
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o
Catastrophic damage
to IGBT Module
o
Used knowledge of
electrical function to
trace damage path
o
Developed multiple
theories, including
defective wirebonding
o
Identified root-cause
as current inbalance at
elevated temperatures
2004 - 2010
2007
How to Implement DfR?
o
Many organizations have developed DfR Teams to
speed implementation
o
o
Challenges: Classic design teams consist of
electrical and mechanical engineers trained in the
‘science of success’
o
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2004 - 2010
2007
Success is dependent upon team composition and gating
functions
DfR requires the right elements of personnel and tools
What Team Members are Needed for DfR?
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2004 - 2010
2007
Component engineer
Physics of failure expert (mechanical / materials)
Manufacturing engineer
o Box level (harness, wiring, board-to-board connections)
o Board / Assembly
Systems Engineer
Engineer cognizant of environmental legislation
Thermal engineer (depending upon power requirements)
Reliability engineer
o Understanding of design guidelines, physics of failure,
and systems lifecycle engineering experience
DfR Overview
o
DfR at Concept / Block-Diagram Stage
o
o
Part (Vendor) selection
o
o
o
2004 - 2010
2007
Benchmarking
Derating and uprating
Wearout mechanisms and physics of failure
o
25
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Specifications
Predicting degradation in today’s electronics
Concept / Block Diagram
o
Can DfR mistakes occur at this stage?
o
Failure to capture and understand product
specifications at this stage lays the groundwork for
future development mistakes
o
Important specifications to capture at concept
stage
o
o
o
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2004 - 2010
2007
Reliability expectations
Use environment
Dimensional constraints
Reliability Goals
o
Typical reliability metrics
o
o
Desired lifetime
o
o
o
o
o
2004 - 2010
2007
Defined as when the customer will be satisfied
Should be actively used in development of part and product
qualification
Product performance
o
27
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Desired Lifetime / Product Performance
Returns during the warranty period
Survivability over lifetime at a set confidence level
To mitigate misinterpretation, try to avoid MTBF or MTTF and focus
on Annualized Failure Rate (AFR)
Product Performance: Survivability
o
Some companies set reliability goals based on
survivability
o
o
o
Advantages
o
o
o
2004 - 2010
2007
Helps set bounds on test time and sample size
Does not assume a failure rate behavior (decreasing,
increasing, steady-state)
Disadvantages
o
28
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Often bounded by confidence levels
Example: 95% reliability with 90% confidence over 15 years
Can be re-interpreted through mean time to failure (MTTF) or
mean time between failures (MTBF)
Limitations of MTTF/MTBF
o
MTBF/MTTF calculations tend to assume that failures are
random in nature
o
o
Easy to manipulate predictions
o
o
o
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2004 - 2010
2007
Tweaks are made to reach desired MTBF
E.g., quality factors for each component are modified
Often misinterpreted
o
o
Provides no motivation for failure avoidance
50K hour MTBF does not mean no failures in 50K hours
Better fit towards logistics and procurement, not failure
avoidance
Part Selection
o
The process of creating the bill of materials (BOM)
during the ‘virtual’ design process
o
o
For some companies, this is during the creation of
the approved vendor list (AVL)
o
30
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2004 - 2010
2007
Before physical layout
Design-independent
Part Selection (cont.)
o
KIS: Keep it Simple
o
o
o
o
Reality: Marketing hype far exceeds actual
implementation
o
o
o
31
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2004 - 2010
2007
New component technology can be very attractive
Not always appropriate for high reliability systems
Be conservative
Component manufacturers typically use portable sales to
boost numbers
Claim: We have built 100’s of millions of these
components without a single return!
Actuality: All sales were to two cell phone customers with
lifetimes of 18 months
Part Selection (cont.)
o
Even when used by hi-rel companies, some
modifications may have been made
o
o
Prior examples of where care should have been taken
o
o
o
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2004 - 2010
2007
Example: State-of-the-art crystal oscillator required
specialized assembly to avoid failures one to three years
later in the field
New technologies: X5R dielectric, SiC diodes, etc.
New packaging: Quad flat pack no lead (QFN), 0201, etc.
Critical actions for part selection include critical
component identification and derating
Component Ratings
o
Definition
o
o
Typical parameters
o
o
o
o
© 2004 - 2010
2007
A specification provided by
component manufacturers that
guides the user as to the
appropriate range of stresses
over which the component is
guaranteed to function
Voltage
Current
Power
Temperature
33
Derating
o
Derating is the practice of limiting stress on electronic parts to levels
below the manufacturer’s specified ratings
o
o
o
Goals of derating
o
o
o
o
o
o
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2004 - 2010
2007
Maintain critical parameters during operation (i.e., functionality)
Provide a margin of safety from deviant lots
Achieve desired operating life (i.e., reliability)
Sources of derating guidelines
o
o
Guidelines can vary based upon environment
(“severe, protected, normal” or “space, aircraft, ground”)
One of the most common design for reliability (DfR) methods
Governmental organizations and 3rd parties
OEM’s
Component manufacturers
Derating is assessed through component stress analysis
Criticality of Component Stress Analysis
o
Failure to perform component stress analysis can
result in higher warranty costs, potential recalls
o
o
Eventual costs can be in the millions of dollars
Perspective from Chief Technologist at major
Original Design Manufacturer (ODM)
“…based on our experience, we believe a
significant number of field returns, and the majority
of no-trouble-founds (NTFs), are related to
overstressed components.”
35
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2004 - 2010
2007
“Let’s Use a COTS Board as a Solution”
36
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2004 - 2010
2007
Define Reliability Goals
o
37
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2004 - 2010
2007
Compatible with wide variety of reliability metrics
Specify Environments
o
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2004 - 2010
2007
Handles very complex environments
Input Design Files
o
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2004 - 2010
2007
Takes standard output files (Gerber / ODB)
“Let’s Use a COTS Board as a Solution”
o
Know the actual use (operating) environment
o
o
o
o
40
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Temperature
Vibration
Power
Humidity
2004 - 2010
2007
PoF Vibration Results
Random Vibration Strain
41
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2004 - 2010
2007
PoF Vibration Results
Random Vibration Strain
42
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2004 - 2010
2007
Mount Point Added to Same COTS Board
43
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2004 - 2010
2007
Case Study: Pb-Free Transition
SnPb Assembly
o
Demonstrated to avionics customer that transition to Pb-free
would have a detrimental impact to product performance
o
44
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2004 - 2010
2007
SAC305 Assembly
Driven by severe use environment
Design for Manufacturability (DfM)
© 2004 - 2010
2007
45
DfM
o
Definition
o
o
Requirements
o
o
46
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2004 - 2010
2007
The process of ensuring a design can be consistently
manufactured by the designated supply chain with a
minimum number of defects
An understanding of best practices (what fails during
manufacturing?)
An understanding of the limitations of the supply chain
DfM Failures
o
DfM is often overlooked in the design process
o
Reasons
o
o
o
o
47
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2004 - 2010
2007
Design team often has poor insight into supply chain
OEM requests no feedback on DfM from supply chain
DfM feedback consists of standard rule checks (no
insight)
DfM activities at the OEM are not standardized or
distributed
Criticality of DfM
o
Failure to perform DfM increases the risk of a
defective product or lot reaching the end customer
o
o
Warranty costs can be significant
Perspective from a major Original Equipment
Manufacturer (OEM)
…we must fully address DfM <sic> to assure
successful product launches and continuing
volume production with acceptably low defect
levels.
48
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2004 - 2010
2007
DfM Failures
o
o
DfM is often overlooked in the design process
Reasons
o
o
o
o
49
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2004 - 2010
2007
Design team often has poor insight into supply chain (reverse
auction, anyone?)
OEM requests no feedback on DfM from supply chain
DfM feedback consists of standard rule checks (no insight)
DfM activities at the OEM are not standardized or distributed
Key Aspects of DfM
o
Proactive
o
Considers and optimizes all manufacturing functions
o
o
Assures that critical objectives are known, balanced,
monitored, and achieved
o
50
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Supplier selection and management, procurement, receiving,
fabrication, assembly, quality control, operator training, shipping,
delivery, service, and repair
2004 - 2010
2007
Cost, quality, reliability, regulatory compliance, safety,
time-to-market, and customer satisfaction
How to Implement DfM
o
Successful DFM efforts require integration of product
design and process planning
o
o
51
©
2004 - 2010
2007
If existing processes are used, new products must be designed to
parameters and limitations of these processes (whether build is
internal or external)
If new processes, then product and process need to be developed
concurrently and mindfully (carefully considering the risks
associated with “new”)
Old Style Product Development - “Sequential Over The Wall”
PRODUCT
ENRG.
R&D
VALIDATION
TESTING
MANUF./
ASSEMBLY
Stress
Requires 4.5 - 5
CHAMBER
Feedback Loops
o
o
o
Before DfM, it was “We designed it” ~ “You build it!”
Design engineers worked independently, then transferred designs
“Over the Wall” to the next department or external to the company (CM).
Eventually manufacturing has to assemble the product.
o
o
o
o
52
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2004 - 2010
2007
Usually inherit a product not designed for their processes and too late to make changes.
Manufacturing forced struggle to meet yield, quality, cost or delivery targets.
Often required trial & error crisis management
Followed by launch delays, then quality and reliability issues.
DEALERS
DISTRIBUTORS
SERVICE
Case Study: No DfM
o
Aerospace company
o
o
Division A
o
o
PCB manufacturer is a top supplier.
Division B
o
Wanted to blacklist the same
PCB manufacturer.
o
On-site audit found no
major process issues.
o
Root-cause: No prior DfM
engagement with supplier
in Division B
o
53
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Two divisions
2004 - 2010
2007
Resulted in numerous
field issues.
Key DfM Guidelines
54
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o
Foundation of a robust DfM system is a set of design
guidelines and tasks
o
Guidelines need to be customized to company’s culture,
products, technologies and based on a solid understanding
of the intended production system – whether internal or
external
o
“Top 10” DfM guidelines and tasks that are applicable to
most companies
2004 - 2010
2007
“Top 10 DfM Guidelines”
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
55
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2004 - 2010
2007
Know Your History (Learn from the Past)
Standardize Design Methods
Simplify the Design – Parts Reduction
Design for Lean Processes
Eliminate Waste
Design for Parts Handling
Design for Joining and Fastening
Use Error Proofing Techniques
Design for Process Capabilities
Design for Test, Repair, and Serviceability
DfM Guideline #1: Know Your History
“Those who do not learn from history are doomed to repeat it.”
o
Learn from the past
o
o
o
Develop and implement strategies to address and prevent recurrence of
mistakes.
Know and understand all problems and issues with current and past products
with respect to:
o
o
o
o
56
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2004 - 2010
2007
Process Yields, Returns, Corrective Actions, Recalls, etc.
Manufacturability / Delivery / Quality / Repairability / Regulatory / Recalls
Especially critical if carrying over existing technologies into new designs.
Best approach is to have an effective system for capturing and disseminating
this historical knowledge throughout the organization (e.g., FRACAS)
At minimum, initiate brain storming sessions (post-mortems) to collect lessons
learned/best practices from all areas of the organization.
DfM #2: Standardize Design Methods
o
o
o
57
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Standardize design, procurement, processes,
assembly, equipment throughout organization
o
Reduces overall cycle time.
o
Simplifies training and tasks.
o
Reduces repeated mistakes
o
Improves opportunity for bulk discounts.
o
Improves opportunity for automation and operation standardization.
Don’t Redesign the Wheel
o
Never custom design when you can buy off the shelf.
Limit exotic or unique components.
o
Higher prices due to low volumes and less supplier competition.
o
Lower quality for exotic components.
o
More opportunity for supply chain disruptions.
2004 - 2010
2007
DfM: Summary
o
DfM is a process
o
Earlier is always better
o
o
o
Always be aware of the tradeoffs
o
o
58
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Should be discussed at concept stage
E.g.: Interconnect strategy (backplane vs. tiering vs. single board)
DfM vs. DfR vs. DfS (or DfT – test)
Communication and knowledge are the core of DfM
2004 - 2010
2007
Design for Supportability (DfS)
© 2004 - 2010
2007
59
Design for Supportability
o
o
o
60
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2004 - 2010
2007
The best design is not only reliable and
manufacturable, products must also be Designed for
Supportability (DfS).
Designing products to be both reliable and
supportable is a critical step in the process one that
must be addressed if customers or end users have
repairable systems or products
Completes the DfA equation: DfR + DfM + DfS
“Top Ten DfS Logistics Design Elements”
o
o
o
o
o
o
o
o
o
o
61
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Baseline life cycle cost (estimated total ownership cost)
Use environment verification
Corrosion protection and mitigation
Supplier benchmarking and vendor maturity and stability
Maintenance planning, procedures, and real-time data collection,
warrantees
Prognostics and diagnostics
Readiness based spares
Open systems architecture, modular design, software re-use (includes
overall design re-use)
Technology refresh
Obsolescence management (planning ahead)
2004 - 2010
2007
Obsolescence Management
o
Obsolescence management is a key driver
that also mitigates the risk of counterfeit parts.
o
o
o
o
62
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Best practices and lessons learned are well
documented.
Planning ahead is key
Left unchecked obsolescence will increase support
costs (and also developmement and production
costs)
The First “M” in Diminishing Manufacturing Sources
and Material Shortages (Remember DfM)
2004 - 2010
2007
Design Change due to Obsolescence (DfS + DfR + DfM)
o
o
63
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2004 - 2010
2007
Automotive customer
evaluated replacement parts
PoF modeling identifies risk of replacement before
prototype. Modified design accordingly
Summary: DfA = integration of DfR + DfM+ DfS
o
Practice design for excellence (DfX) to optimize affordability
o
o
o
o
Use Automated Design Analysis
o
o
o
Facilitates collaboration
Implement tools and processes that allow in-depth assessment at
earliest stages in acquisition
Remember the first “M” in DMSMS and practice DfM
o
o
64
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Design for reliability
Design for manufacturability
Design for supportability
Know the quality and manufacturing of your suppliers
Know your suppliers (mitigate risk of counterfeit)
2004 - 2010
2007
“Let’s Use a COTS Board as a Solution”
65
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2004 - 2010
2007
With DfA = What Happens to Optimized Total Ownership Cost?
?
?
?
© 2004 - 2010
2007
66
Backup
© 2004 - 2010
2007
67
DfM #3: Simplify the Design - Parts Reduction
Everything should be made as simple as possible, but not one bit
simpler. - Albert Einstein
o
Parts reduction is one of the best ways to reduce
the cost of fabricating and assembling a product and
increase quality and reliability.
o
o
o
o
o
o
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2007
Reduces parts costs.
Reduces direct labor costs.
Reduces process equipment.
Reduces number or workstations.
Fewer opportunities for defective parts.
Fewer opportunities for assembly errors.
DfM #3: Parts Reduction (cont.)
o
Can also reduce structural costs.
o
o
Fewer parts rippling through the organization reduces the work
load for every department at every level.
Fewer items to be processed by:
o
Product Development
o
o
Manufacturing Support
o
o
o
69
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Inventory Warehousing, Material Handling, Service Parts.
Quality Management.
Manufacturing facilities
o
o
Engineering, Purchasing, Development/Test Labs.
Facility Size, Equipment, Processing/Assembly Time & Labor
Provides more opportunities for process automation.
2004 - 2010
2007
DfM #3: Methods for Parts Reduction
o
Method 1: Parts Commonality via Multi-Use/Multi-Functional Parts
o
Develop an approved vendor list (AVL), aka preferred parts lists or
standardized bill of materials (S-BOM), to encourage different products lines to
share common parts.
o
o
Use of one-piece structures
o
From injection molding, extrusions, castings and powder metals or similar fabrication
techniques instead of bolt/glue together multi part assemblies.
o
Establish part families of similar parts based on proven materials, architecture
and technologies that are scaled for size or functionality
o
Use multi-functional parts:
o
o
o
70
©
Designer CAD/CAE systems can be configured to access preferred designs and parts
catalogs.
2004 - 2010
2007
An electric conductor that also serves as a structural member,
A cover or base plate that also serves as a heat sink
Incorporate guiding, aligning, or self-fixturing features into housing and structures.
DfM #3: Methods for Parts Reduction
o
o
Method 2: Modular design.
Can push DfM issues farther down the supply chain
o
Use complete modules and subassemblies, instead of
designing, fabricating and assembling everything yourself
or on one platform
o
Advantages
o
o
o
o
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Manufactured and tested before final assembly.
Facilitate the use of standard components to minimize product
variations.
Add flexibility to product update in the redesign process
Mitigates obsolescence risks
2004 - 2010
2007
DfM #4: Design for Lean Processes
Fundamental Principle of Lean
Anything that does not add value to
the product is waste and must be
reduced or eliminated
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2004 - 2010
2007
DfM #4: Design for Lean Processes
o
Lean supply, fabrication and assembly processes are
essential design considerations.
o
Simple lean fabrication/processing/assembly is more likely to
be done quickly and correctly
o
o
o
o
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2004 - 2010
2007
Right part at the right station at the right time
Reduced throughput time equals faster time to market and
lower costs (reduced labor hours and faster turns).
Designs that are easy to assemble manually will be more
easily automated.
Assembly that is automated will be more uniform, more
reliable, and of higher quality.
DfM #4: Design for Lean (cont.)
o
Develop and use standard guidelines appropriate for the process:
o
o
o
o
For assembly - design for human factors – the “Visual” Factory
o
o
o
Allow for visual, audio and/or tactile feedback to ensure correct assembly
operations.
Makes it obvious to follow the correct process flow.
Bottlenecks and problems are more easily identified
o
Provide adequate access clearances for tools and hands.
o
Design in self aligning and self guiding features such as tapered parts, guide
pins or groves.
o
Design work to use standard tools and settings: crimpers, splicers, cutters, solder
iron tips, drill bit sizes, torque settings, wire sizes
o
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Common hole sizes, lines, and spacings
Standard soldering temperature profiles
Standard handling (e.g., avoid MSL > 3 components)
Minimizes tool clutter and decision making on what to use
2004 - 2010
2007
DfM #5: Eliminate Waste
o
Seven Types of Waste
1.
Overproduction

2.
Waiting

3.

Walking, climbing, bending, searching, identifying
Defective products

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Excess raw material, excess WIP
Unnecessary Motions

7.
Unnecessary operations, too many inspections, not building to customer spec
Inventories/Storage

6.
Moving material, parts, tooling
Transferring product between locations, into/out of racks
Process Inefficiencies

5.
Stop build to look for parts, tools, material, information
Transportation/Moving

4.
Build more than required, before required.
2004 - 2010
2007
Low Yields, mistakes leading to large reworks, sorting, inspection
DfM #6: Design for Parts Handling
o
Minimize handling to correctly position, orient, and place
parts and avoid multiple or complex assembly orientations.
o
Use symmetrical parts.
o
o
o
Use parts oriented in magazines, tape, reels or strips or use parts designed to consistently
orient themselves when fed into a process
o
Reduce and avoid parts that can be easily damaged, bent, or broken.
o
Parts should be designed with surfaces that can be grasped, placed or fixtured.
o
o
o
o
Reduces the need for temporary fastening and complex fixtures.
Begin assembly with a large base component with a low center of gravity. Assembly
should proceed vertically with other parts added on top
o
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When non-symmetrical parts are needed, use keying features
to ensure proper orientation.
Make orienting and mating parts as visually obvious as possible.
Exception: avoid upward orientation of debris /contamination sensitive features.
Prevent dust or moisture from falling into electrical, hydraulic, pneumatic connector or lines
Use appropriate and safe packaging for parts but minimize the creation of waste
2004 - 2010
2007
DfM #7: Design for Joining & Fastening
o
Design for efficient joining and fastening.
o Fasteners increase the cost of manufacturing, handling and
feeding operations.
o
o
o
Avoid threaded fasteners when possible, consider alternative,
o
o
o
o
o
2004 - 2010
2007
Consider the use of snap-fit.
Evaluate adhesive bonding techniques.
Where fasteners used, minimize variety
o
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Screws, bolts, nuts and washers are time-consuming to assemble & difficult to
automate.
Increased potential for defects (missing and improper assembly).
Use guidelines and standardize fasteners to
minimize the number, size, and variation.
Self-tapping and chamfered screws are preferred.
Use captive fasteners when possible.
DfM #8: Use Error Proofing Techniques
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o
Mistakes will happen, What can go wrong will go wrong.
o
Anticipate and Eliminate opportunities for error
o
Use error proofing techniques in product design and assembly
o
Make the correct assembly process visually obvious, well-defined and clear cut.
Remove confusion and interpretation.
o
Have written instructions in one location only – no competing docs
o
Minimize wording in instructions. Use pictures, icons, photos
o
Key unique parts so that they can be inserted only in the correct location.
o
Use notches, asymmetrical holes and stops to mistake-proof the assembly
process.
o
Design verifiability into the product and its components.
o
Sight, Sound or Feel - use visual, audio, tactile feedback
o
Use color coding
o
Electronic products can be designed to contain
self-test diagnostics
o
Avoid or simplify adjustments or modifications
2004 - 2010
2007
DfM #8: Error Proofing (example)
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o
All polarized SMT and through-hole components should be placed in the
same orientation and in only one axis.
o
This facilitates easier visual inspection.
o
Where this is not practical, try to group components in the same
orientation
2004 - 2010
2007
DfM #9: Design for Process Capabilities
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o
Make use of specific production DFM guidelines or know the process
capabilities of the production equipment
o
Avoid unnecessarily tight tolerances and tolerances that are beyond the
inherent capability of the manufacturing processes or operators in a
continuous production situation. Tighter is not always better!
o
Perform tolerance stack up analyses on multiple, connected processes
and parts.
o
Determine when new production process
capabilities are needed
o
Allow time to develop/optimize new processes
o
Determine optimal process parameters
o
Establish controlled processes.
2004 - 2010
2007
DfM #10: Design for Test, Repair, & Serviceability

Defects will occur. Design for ease of test and repair will make these processes
more efficient, cost effective, and reliable.
o
o
o
o
o
o

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2004 - 2010
2007
Use recommended component spacing to allow for safe repair or replacement
Design in diagnostics, self tests, meaningful error messages, and diagnostic interfaces.
ESD Considerations - provide warning labels and appropriate workstations where needed.
Standardize approaches and methods.
o
Minimize parts variety, minimize tools/special tools needed
Minimize disassembly steps to access replaceable/repairable Items.
o
Consider unfastening and refastening, disassembly and reassembly issues.
o
Use self-fastening and self-jigging features when possible.
o
Consider impact of adhesives, coating, and potting
Wiring/Hose Interconnection – consider disconnect and reconnect capabilities.
Failed products are often returned to the manufacturer for service and failure
analysis. Where possible, use the production test equipment/setup for returns
analysis.
DfM #10: Example
o
If BGA's are on both sides of the board, it is not
recommended that the BGA's are positioned on top of
each other.
o
o
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This method makes rework of a BGA extremely difficult.
Also makes x-ray inspection of solder balls very difficult
2004 - 2010
2007
Additional Questions ?
o
o
o
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2004 - 2010
2007
Walter Tomczykowski
5110 Roanoke Place
College Park, MD 20740
301-474-0607
[email protected]