Didn't get your example, but I'm not familiar with "gold washing down 
between pads". It may be that the immersion gold is "background plating" 
onto the board surface during the ENIG process, and not being detected 
prior to assembly. This can be a problem for ENIG platers. Check you 
incoming boards.

Tom Kemp 
SR QAE
Rockwell Collins



Dave Connitt <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
03/05/2009 02:09 PM
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[TN] ENIG Question






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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