This is a summary of the newest PCB cleanliness and residue measuring requirements as part of the IPC J-STD-001H. More on this standard including training at solder.net
2. Hts of component
Background
How did we get here?
• J-STD-001 revisions F and lower based on ROSE testing
• ROSE testing was initially developed as a process monitoring tool for
entire process and assembly
• ROSE testing developed when component spacing and standoff
heights of components were much greater
• Processes when the standard was developed had a much wider
window-rosin-based fluxes, CFC-based cleaners
• ROSE testing developed in 1970’s now considered an obsolete
practice
3. Hts of component
Background
How did we get here?
• Data generated by Navy established 1.56 ug NaCl eq/cm as the
pass/fail criteria
• Now PCBs in harsh environments such as mining, space, human body
functional monitoring
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• Standoff height were soils can hide are now 2-3 mils
• Spacing between components now as small as 3-4 mils
• Fluxes less aggressive-”no cleans” in style
• More critical to get boards clean that are going in harsh
environment-like space , oil wells and underneath vehicles
Where we are At Today
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• Tanks are contaminated
• It can tell if saponifier mixture ratios are incorrectly mixed
• It can indicate that a reflow profile has run amuck-more chemical
species which have not been activated from fluxes
ROSE testing can be used for process monitoring
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ROSE can answer the question-What Changed?
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• Outlined in Section 8-Cleanliness Testing Specification of J-STD-001
• IPC White Paper 019A is companion document where a lot of process
questions answered-How do I do this?
NEW Standard for Cleanliness Testing Developed
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• J-STD-001H-if no overwhelming electrical failures due to
electrochemical interaction of residues on PCBs-then can continue
process monitoring using the ROSE testing as a go/no-go gauge
• No issues with dendritic growth or electromigration under
temperature or bias in operating conditions then continue to use
ROSE testing
“If It Ain’t Broke Don’t Fix It”
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• Have to have “objective evidence” that chemical species on the
board due not impact the reliability of the electronics assembly
based on data
• Data can be generated through SIR testing, ionic cleanliness testing
or other functional testing as agreed to by the user and the
manufacturer
What About a New Material Set?
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• Flux is changed
• Cleaning agents or cleaning agent mix ratios changed
• Changes in cleaning or flux suppliers
• Changes in soldering material
• Changes in board metallization
• Changes in solder mask
• Geographic change in manufacturing locations
When Will a New Requalification of the Process Need t Happen?
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• Changes in assembly location
• Changes in cleaning parameters (e.g. belt speed, pressure of
cleaning jets)
• Changes in reflow profiles established in the process qualification
When will a lower level –i.e.“objective evidence” – be required?
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• Objective evidence-proof that the cleaning process removes all
harmful “soils” that can impact the reliability negatively
• These soils, under device operating conditions-usually temperature
and humidity will not migrate to a point where their electromigration
will cause harmful effects
When will a lower level –i.e. “objective evidence” – be required
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12. Ce bias cond
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• Ionic cleanliness testing is just a chemical test
• Have to be able to relate this chemical measurement to a biased
level of performance her the species “migrate/move” and cause
harmful electrical effects for the given assembly
• SIR or other reliability testing of the circuit under the biased conditions
When will a lower level –i.e. “objective evidence” – be required
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13. Ce bias cond
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• ROSE testing for qualification an obsolete practice
• Have to determine a cleanliness level where residues on the board left behind
due not under bias with temp and humidity conditions cause the board to fail
• ROSE testing is a gross overall number and NOT a determiner of “clean” vs
“dirty”
• There is no single cleanliness “number” good for every assembly
• Have to determine the level of residues which could undermine the board’s
function under real operating conditions-testing is required! (MIL, AUTO, MED,..)
Final Points
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