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| Date: | Thu, 5 Mar 2009 17:49:17 -0500 |
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It might been that there is actually a foot on the pads and you have some bridging going on if the pads are very close. That is normally caused by the catalyst that the nickel/gold adheres to during plating remaining on the laminate. Check a part before processing and see if the pads have a large foot and if you can see any plating between them.
Scott B. Westheimer
5709 Clarks Fork Drive
Raleigh, NC 27616
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Home: (919)713-0748
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> Date: Thu, 5 Mar 2009 15:09:02 -0500
> From: [log in to unmask]
> Subject: [TN] ENIG Question
> To: [log in to unmask]
>
> Hello All,
> I have a question regarding a strange situation regarding reflow
> soldering ENIG finish boards.
> We have seen a few boards that have what seems to be gold "washing "
> down between pads and creating shorts. This seems to come and go. This
> is a flex circuit that is placed on a pallet to go through our SMT line.
> One other bothersome issue is that we are having difficulty getting
> proper solder stencil alignment across all the flexes in the pallet. I
> am pushing to have the flex "panelized" from the vendor to increase
> positional accuracy but the jury is still out on that.
> I suspect these two issues are related. If the solder gets deposited
> "off pad"slightly could the washing process be moving some of the gold
> in between pads? I attached an example.
> Has anybody come across this?
> If so, what was the solution?
>
> Thanks,
> Dave Connitt CID+
>
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