Looks to me like the board wasn't cleaned well before coating.  The same "thinness" that's apparent around to the vias is also apparent around the components.  They're the same area's you'd expect to see entrapped contaminants after cleaning. Although it's not a complete dewetting, the coating has regressed from those areas.

Although your cleaning process seems like it should be fine, is there a possibility the machine was not functioning properly for this lot? Has this been a continual problem or was it just this small group of boards? Could the boards have been loaded so that they were shadowed from the spray head(s) by other, larger boards?

Gregg

-----Original Message-----
From: Rob Strecker [mailto:[log in to unmask]] 
Sent: Monday, March 22, 2010 12:46 PM
To: [log in to unmask]
Subject: [TN] Conformal Coating Issue?

Hi all,
We have an issues with one of our customers that we build PCA's for.
After we complete the build the customer sends it out for conformal
coating.  It appears the coating or florecent does not like via holes.
I believe they are still getting good coverage and I don't think this is
a dewetting problem as there is still coating present in the darker
locations.  I don't see these boards after they get coating but that's
what I am tolled.

These boards are double sided, lead free using water soluble paste/flux
washed in a batch cleaner with a 6% chemical concentration.  We go
through many rinse cycles and clean to 1.4Meg (resistivity monitoring of
the rinse water, for what it's worth).

What might the casue of this be?... wash solution in the vias??  Below
is a link to the picture.

http://ipc-technet.groupsite.com/galleries/photo/117131


Rob

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