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Reply To: | TechNet Mail Forum. |
Date: | Wed, 29 Oct 1997 14:39:32 +0000 |
Content-Type: | multipart/mixed |
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In the IPC soldering flux spec J-STD-004 there are a couple of
non quantitative tests, IPC-TM-650 method 2.3.33 Silver Chromate
for Halides and method 2.3.35.1 Fluoride spot test. If these
tests are pass then the flux is Halide and Flouride free. If
they fail then there are quantitative tests that can be used to
determine the Halide and Fluoride concentration. My question is
what is the limit of detection of these qualitative tests? What
concentration of halide or Fluoride in the flux would just pass
the silver chromate or fluride spot test?
I'm planning on using a water wash flux that passes these
tests for placing solder balls on silicon wafers. My semiconductor
assembly experience with die attach materials and epoxy
encapsulants makes me very wary of halides. How concerned should I
be if the Aluminium bond pad is protected by good subsequent
metallisation and chip passivation? Data sheets for most
semiconductor assembly materials will give ppm of Chloride, etc
with "good" values being below 10 or 20. Is there a direct
comparison possible with fluxes?
regards, Jeremy Drake
Design to Distribution ltd
Stoke on Trent
England
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