Dear Technos,

 

I have an issue here, soldermask peeling off the boards after wash, in
areas under the mold seal.

 

I have this 0.125" thick PCB, with 4oz of Cu in both of the 2 layers. It
is a 100% TH power board, with huge coils and electrolytic caps. The
soldermask passes the incoming tape test, but after wave and wash, when
we remove the mold seal that masks mechanical assembly holes, we see
spots where the soldermask peels away. Most of these spots are where the
mold seal was. We rarely see smaller spots where there was no mold seal.

 

All the spots show on the solder side, I see nothing on the component
side.

 

The wash is plain water, to remove water soluble flux residue.

 

The question: is there something wrong with the soldermask, with the
mold seal, any compatibility issue, or simply something natural for 4oz
Cu?

 

Thank you for your help,

 

Ioan


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