Kathy,

I would argue against the "only a cosmetic issue" statement. The moisute (if this is the cause) takes up space in the polymer coating and will be a path for more moisture and contaminants to permiate to the surface.

Because you are spending time and money to coat the boards it is obvious you are expecting them to be exposed to harsh conditions. These residues/gaps in the coating material will reduce the protective ability of the coating.

What is the RH in the coating room?

David A. Douthit
Manager
LoCan LLC

Kathy Kuhlow wrote:

> What causes white residues after conformal coating?  The coating is an acrylic and after the first coat there appears to be a white residue and after the 24 hour cure the coating appears very dull and still has some of the white residues.  The residues almost look like water flux residue but it isn't.  The supplier that the coating was purchased from says it is strictly humidity related and only a cosmetic issue.  There is no visible loss of adhesion.  The solder mask is a LPI matte finish.  Can this be part of the problem?
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