Hi All!
Another weird one again, I'll post a picture tomorrow when I get back into
work. But a preface to the picture, is that we built a board that was wave
soldered, and after post wave cleaning, you could see a faint outline of
where masking was applied over holes, we use water soluble dots over holes
etc...I've seen that before, but it usually isn't so noticable that it's a
big deal.
However, on this particular board we're doing some jumper wires that go from
the bottomside up to the top, this is done after wave and everything else.
The operators soldered the wires to where they needed to go, and then needed
to clean the boards prior to tak-pak'ing them to the board. So before sending
them to the cleaner, they used kapton tape to secure the wires to the board
so they didn't flop around in the cleaner...makes good sense to me. When they
got the boards back outta the cleaner and removed the tape, there were all
these dark spots in the mask beneath where the tape was...it looks kinda'
bad. But the mask is intact as far as I can see, there is no degradation at
all...it just looks bad...almost looks like something deeper, but I'm sure
it's just mask discoloration...
I baked the boards to see if that would change anything, but it didn't. The
mask is a LPI, don't know the brand. I'll post a picture tomorrow morning.
But have you ever run across LPI masks lightening or darkening, showing
outlines of masking materials after wave soldering, or cleaning (kapton
tapes, preformed dots, etc..)?
What causes that?
Thanks everybody!
-Steve Gregory-
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