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coating with no-clean?

jacqueline coia

#7877

coating with no-clean? | 13 January, 2000

Does anyone conformally coat PCBs that have been processed with a no-clean solder paste? Any comments on this subject would be appreciated. Cheers

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#7878

Re: coating with no-clean? | 13 January, 2000

Hey Jack: It's certainly "do-able." Conformal coating adhesion testing was done as part of the "Evaluation of Low Residue Soldering for Military and Commercial Applications: A Report from the Low Residue Soldering Task Force," published by Sandia National Labs in June 1995. You should be able to get a copy from the EMPF, since they were part of the consortium (I think). The EMPF is in Indianapolis, Indiana, USA where Tim Crawford (crawfot@empf.org or 317.655.3673) was the project manager.

Success differs from process to process and really depends on:

� Incoming parts and PCB cleanliness � Process approach (i.e., flux, amount of flux, solder process, etc) � End item use environment � does coating just have to "cure and stick" or do you do humidity exposure type testing?? � Whether your customer accepts this or not.

Additional points:

� Consider using SIR testing to validate your process (including the coating) to confirm that the effect of the residues you will be sealing on the board is largely unaffected by the coating material. � All coatings over low res fluxes have cosmetic problems. So, a proper description of "go/no go" should be an element of you acceptance criteria. � Most coatings and flux (but not all) combinations are compatible.

My2�

Dave F

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DaveH

#7879

Re: coating with no-clean? | 14 January, 2000

EMPF is now in Philadelphiaunder the auspices of the American Competitiveness Institute. Ph 610-362-1200 Fax 610-362-1290 www.empf.org

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