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March 2009

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Subject:
From:
R Sedlak <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, R Sedlak <[log in to unmask]>
Date:
Thu, 5 Mar 2009 13:04:59 -0800
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Dave:  Your "gold wash" problem used to be fairly common, and most ENIG systems have been modified to avoid the issue, or minimize it dramatically.   However there are some areas of the world who employ large numbers of workers with small sharp knives and magnifying lenses to make the problem go away.

The problem is caused by the fact that the EN will plate ANYWHERE that there is Palladium (or certain other expensive metals) on the board, and as part of the ENIG process, the board is put through a Palladium Catalyst.    If you have a particularly reactive substrate, and I suspect Flex qualifies, the Palladium deposits, and the EN, then IG plates.
Some ENIG systems even have a "Palladium remover" step to prevent this.

We have a catalyst system specifically developed to avoid this problem, so if all else fails, have your vendor contact me.

Rudy Sedlak
RD Chemical Company 

--- On Thu, 3/5/09, Dave Connitt <[log in to unmask]> wrote:
From: Dave Connitt <[log in to unmask]>
Subject: [TN] ENIG Question
To: [log in to unmask]
Date: Thursday, March 5, 2009, 12:09 PM

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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