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Date: | Fri, 10 Mar 2006 09:52:40 -0500 |
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Hi all,
We currently process flex circtuits with immersion tin finish. The
thickness is specfied on the pcb drawing as 4 millionths minimum.
We were seeing PCBs come from our supplier with corrosion on the traces and
plating. We screened for this, and allowed those without corrosion through
the two-sided SMT process. After washing, we see corrosion on the traces
UNDER the solder mask. I have photos if anyone would like.
A few questions..
1) Is there an IPC spec that deals with platings and corrosion? I bought
IPC-A-600G, but I don't see what I am looking for in there.
2) Shouldn't the soldermask be preventing air & moisture from getting to the
traces?
3) I have read some old Technet postings on immersion tin, and it seems it
has known issues with corrosion, shelf life, etc. True? Can someone
summarize?
Thanks!
Kevin Glidden
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