Rudy,
I'd like to hear more about this
"oxide" you're using.
Seems we're still having a rough time with s-m adhesion after
immersion "white tin".
I learned from TechNet that an adhesion promoter would benefit
us; however, I have yet to find something compatible. Any help would be
appreciated, thanks
Franklin
ps: We have switched from Electra to Coates on
recommendations, has anyone had worse or better luck with them
(Coates)?
Steve:
You finally asked something that I
can answer! Thanks!
The problem of adhesion of Dryfilm soldermask
to bare Copper is a legend, and
it is NOT your cleaner, almost
certainly. Dryfilm soldermask does not adhere
to Copper well. H-P
(remember them, they used to make PCB's) had an
especially, ahh,
"interesting" test for soldermask adhesion, where they
floated the
board on molten solder for 1250 hours, or some such, and no sort
of cleaning
could get them through the test....and they further said that
essentially all
cleaning gave the same results, whether chemical, or
mechanical
abraision.
However, oxide made the soldermask stick so strongly that you
had to destroy
the mask to get it off.....
So, we formulated an oxide
chemistry for them that they sprayed on, that was
SO light you could not see
it. We got to calling it the "Emporer's Oxide",
as only the
faithful could see it!!!!
They had some non-believers (at H-P) that at
one point, removed panels from
the oxide line, and put soldermask on them to
see if they could tell a
difference between panels that had been run through
the oxide line, or not.
THERE WAS, BIG TIME.
This is a bit extreme, to
consider oxide under soldermask, but it do work,
and is the best possible
bond enhancer.
Hope this helps, in some way.
Best,
Rudy
Sedlak
RD Chemical
Company
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