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March 2010

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Subject:
From:
Douglas Pauls <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 23 Mar 2010 07:53:04 -0500
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Rob,
What exactly is the customer's beef?  Are they expecting to see a 
completely uniform film everywhere across the board?  I don't really see 
anything wrong with the coating job.

What you may be seeing is residual material in the holes that can weep 
out.  Do you blow out the holes with compressed air after batch cleaning? 
Do you bake the boards after cleaning?

Doug Pauls



Rob Strecker <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
03/22/2010 02:46 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Rob Strecker <[log in to unmask]>


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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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