PCB contamination

Hello everyone!

I have a problem with PCB, we detect that some contamiation apear (dark spots similar to glue or underfill) we detect that this element is Policarbonate. I don't know if on PCB fabrication process some policarbonate are used. We already review all our process because at the begining we think that the problem could be flux but this contamination can not be removal with flux cleaning chemical.

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