Getting alot of white blister marks on a batch
of boards. All boards seem to be from the same date code of board
manufacture. The marks seem to occur over all areas, not just over
copper. There is no residue and does not scrape, it looks like it is
subsurface. To me, it looks as though there is some weakness in the solder
mask which was brought out under the stress of wave solder. The marks are
only on the solder side, and only seem to appear after they've been
washed. Could a defective solder mask have been damaged by heat stress of
the wave, then providing a home from moisture during the wash
process?
Any ideas?
Paul Wareham
DynaGen Systems Inc.