Cleaning of PCBA's

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Hello We are currently getting Proto's of legacy product bu... - Apr 14, 2005 by

boards greater than this spec. can cause latent failure, Do... - Apr 14, 2005 by RDR

Hi John, A primary consideration is the type of flux you ... - Apr 14, 2005 by SheanDalton

Shean made some good points and offered some good starting r... - Apr 15, 2005 by sarag

John O'reilly

#33708

Cleaning of PCBA's | 14 April, 2005

Hello We are currently getting Proto's of legacy product built up in Europe. Our current supplier uses a spec of 14 micrograms or less of sodium chloride per square inch as measured on a omega meter. THe product is Industrial and I am not sure do we need to adhere to this as many european Contract Manufactures do not offer washing. Does anyone clean their boards unless its consumer electronics !!

Any help would be appreciated

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RDR

#33718

Cleaning of PCBA's | 14 April, 2005

boards greater than this spec. can cause latent failure, Do not confuse no-clean assembly materials (nocleaning required) vs. clean chemistries that must be cleaned. You do not want ionic contaminants on your products.

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SheanDalton

#33722

Cleaning of PCBA's | 14 April, 2005

Hi John,

A primary consideration is the type of flux you are using. If it's water soluble (organic acid) then cleaning is highly recommended. Any other flux that fails the copper mirror test, we'd strongly recommend cleaning. Passing the copper mirror test though doesn't mean a flux should not be cleaned, other factors should be considered such as bulk residue and its effect on the circuit and test.

Many factors contribute to why a company does clean. They basically boil down to reliability and yeild. Field failures, production yield, internal manufacturing problems related to testability, handling, the application of a range of fluxes on a single assembly, etc are some more specific reasonings.

Leadfree is a big transition currently underway, and, leadree flux residues do appear to present a stronger case for the need to clean.

Regarding standards of cleanliness, IPC-A-610 section 10.4 offers a review for acceptability, and, IPC-J-STD-001D chapter 8 covers requirements for cleaning. IPC-TM-650 details test methods to determine residue levels. There's a lot of reading and defining in these documents; that said, typically assemblies fall under a requirement for less than 10 micrograms per square inch (1.56 micrograms per cm2).

If you like to discuss this at greater length and detail, please contact us.

Have a Great Week!

Shean Dalton Austin American Technology www.aat-corp.com (+1) 512-335-6400 ext. 20 contactus@aat-corp.com

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sarag

#33743

Cleaning of PCBA's | 15 April, 2005

Shean made some good points and offered some good starting resources. Adding to what he said, I would also mention that many times, even a no-clean flux can cause contamination that requires cleaning. Our lab has dealt with numerous cases of clients that use no clean fluxes that are not getting fully activated, and are left to react with moisture on circuit boards to create reliability issues. It is not the easiest task, but even a no-clean assembly can be cleaned if needed. Whatever the flux chemistry is, it all comes down to the amount and type of residue that is on the board, which can come from numerous sources. We endorse ion chromatography testing which tells you the exact types and quantities of residues on a board (IPC TM 650-2.3.28, rather than the bulk reading that comes from a ROSE tester - each type has different implications. For further help and advice on cleanliness levels and cleaning, you can look at some of our case studies at http://www.residues.com or contact us for more specific information.

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