Hi All,

I am looking for a good interpretation of IPC requirements concerning contamination on electronic assemblies.

Here's the situation:
On some part of the products (~0,5%) we are observing a non-metallic contamination (cloth fibres, human hair, ESD glove fibres). The product is conformal coated, so the contamination is trapped under the coating. We have never had any claims from our customers regarding those, and never seen an assembly functionally failing due to those.

The IPC requirement states that whatever there is that causes the minimum electrical clearance to be violated shall be treated as nonconforming. But it does not say about conformal coating (it presents definitely higher resistance to electrical current than air). 

Is there any document or a norm that says how to treat those contaminants trapped under CC?

Thanks in advance for all your help!

BR/Eileen

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