We conformally coat over no-clean without any problems.

At previous employers, I evaluated coating and no-clean flux compatability.
The biggest variable for coating performance was no-clean flux residue. Most
coatings and flux (but not all) combinations are compatable, provided that
no-clean deposition is below a certain level. Above that level, all coatings
have cosmetic problems. The specific level is flux specific and can still
pass IPC standards for SIR and ROSE testing.

Once I even traced a coating adhesion problem to a supplier's HASL flux
residues.

The process can work with adequate process control if you do your homework
first.


Aric Parr
Sr. Process Engineer
Eaton Corporation
1400 S. Livernois
PO Box 5020
Rochester Hills, MI 48308-5020
248 608 7780
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---------- Original Text ----------

From: C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG, on 7/21/99 12:08 PM:

Hi,

My company is currently running a no-clean PCB assembly process, and we
have started conformally coating one of our PCB assemblies, without cleaning.
The decision not to coat was based on a ROSE measurement on our existing
process and the fact that other companies were not cleaning.

I would be interested to hear from anyone else that conformally coats
without cleaning and why that decision was made.
I would especially like to understand what the differences are between
non-ionic and ionic contamination and the effects each can have on a PCB in
certain climates.

Thanks for any replies
Ben Hammond

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