Solvent Selection
Cleaning
Process Options
Why do we Clean?
• We clean to ensure product reliability
– remove ionic / acidic contamination and particulates
that can cause problems in use of the product
• We clean to prepare surfaces
– remove oils and flux residues that can inhibit the
bonding of conformal coatings / insulation coatings
– remove flux residue from underfill areas
– prepare surfaces for bonding or coating
• We clean to meet specification requirements
– because it is in the contract
Was No-Clean technology
developed by Military Intelligence?
The phrase “No-Clean” is
incorrect. These types of
fluxes and pastes correctly
should be referred to as
“Synthetic” Fluxes
Many “Synthetic” fluxes and
pastes are cleaned
Steve Stach / AAT
No-Clean Fluxes really are
Synthetic Fluxes
• Traditional fluxes are limited
• Rosin fluxes must contain rosin
– Inherently sticky
• not as printable for Fine Pitch
• Water solubles must be water soluble
– Shorter printing life, less tack
• harder to process -must be cleaned
• Synthetic Fluxes have no formulary restrictions
– Can be formulated to optimize the process
• Printability, tack, printing life, cleaning or no clean
Steve Stach / AAT
Flip Chip cleaning prior to under-fill improves reliability
by preventing under-fill voids and delamination
Delamination
of under-fill
will cause
premature
solder failure
Under-fill Void
traps foreign
matter and
concentrates
physical force
Steve Stach AAT
Lead free soldering requires stronger
fluxes/cleaning or nitrogen oven inertion
No-lead residues are
discolored due to higher
temperature profiles
Vapor Degreasing
LENIUM GS, 3M HFEs
Aqueous
ALPHA 2110
Semi-Aqueous
Types of
HYDREX SP / SP-50
KYZEN 4520
ZESTRON AC200
BIOACT EC-7R
AXAREL 32 / 36 / 46
Cleaning
Options
Evaporative Solvents
IPA, Acetone, MEGASOLV JB, AXAREL 2200
BIOACT SC-22
Cleaning Technologies with
Differing Benefit Trade-offs
•
•
•
•
•
Aqueous Cleaning
Evaporative Solvent Cleaning
Semi-aqueous Cleaning
Vapor Degreasing
Out-Sourced Cleaning
Cleaning Options
• Aqueous
– Water Wash with Water Rinse
• Semi-Aqueous
– Hydrocarbon Wash / Water Rinse
• Vapor Degreasing
– Heated Solvent Vapor Wash and
Rinse
• Evaporative Solvents
– Hydrocarbon Wash and Rinse
• Contract Cleaning
– Contractor Responsible for Part
Cleaning
Cleaning Trade-offs
Capital
Cost
Environmental Complicated
Cost
Process?
Process
Time
Cleaning
Ability
Aqueous
$10-100K
Low/Medium
Medium
Medium
Very Good
Evaporative
Solvent
1-10k
High
Low
Short
Good
SemiAqueous
$50-200k
Medium
High
Long
Very Good
Out
Sourced
None
None
Lowest
Long
Very Good
Vapor
Degreasing
$25-150K
Medium
Low
Short
Good
Aqueous Cleaning
• Advantages
–
–
–
–
–
Low VOCs
Cleans Most Contamination
Chemicals Inexpensive
Equipment low to Moderately Expensive
Short process cycle - inline
• Disadvantages
–
–
–
–
Wastewater Treatment / Neutralization
High Energy Cost
Medium to Long Process Cycle - Batch
Government Restrictions on Water Use
Evaporative Solvents
• Advantages
–
–
–
–
Easy to use
Chemicals Relatively Inexpensive
Process Time Under 20 minutes
Good for Cleaning Stencils / CCAs / Misprints
• Disadvantages
–
–
–
–
High VOC Content
Safety concern, Flammable/combustible
Waste Disposal
Can just move dirt around
Semi-Aqueous Cleaning
• Advantages
–
–
–
–
High VOCs, but Low Evaporation
Cleans Most Contamination
Chemicals Moderately Expensive
Many Products are Biodegradable
• Disadvantages
– Moderate Energy Cost
– Medium to Long Process Cycle
– Good Machines Are Expensive
Vapor Degreasing
• Advantages
–
–
–
–
Solvent is Continuously Recycled
Cleans Most Organic Contamination
Process Time Under 10 Minutes
Excellent for Cleaning Fine Pitch / BGAs / Blind Holes /
Machined Parts
• Disadvantages
–
–
–
–
–
Not so good for polar soils
Low to Moderate Energy Cost
Chemicals Must Be Handled Carefully
Chemicals Expensive & volitile
Systems can can become acidic with water
contamination
– VOC issues
Contract Cleaning
• Advantages
– Contract Professional Manages the Cleaning
Process
– No Chemicals to Buy; No Maintenance
– No Permits to Meet
– No Equipment to Purchase
• Disadvantages
– Not many