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September 2006

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Subject:
From:
Dennis Fritz <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Mon, 18 Sep 2006 20:02:43 EDT
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In a message dated 9/18/2006 7:50:57 P.M. Eastern Daylight Time,
[log in to unmask] writes:

There is  one thing I did leave out. The pads that aren't taking ENIG all
happen to be  in the same net. Has anyone encountered this?


To me, this says that there is some "electrical" cause, stronger than the
catalyst that initiates the electroless nickel plating.  Remember, the  catalyst
in the ENIG process is a tightrope between getting plating everywhere
(extraneous plating) and not covering some pads (skip plating). Here you  have skip
plating

 If the same net skips board-to-board, likely it is a design issue  where
something is grounded out unintentionally and plating is getting defeated  in one
spot. It could be that some via is tented consistantly holding a  poisoning
fluid - tin stripper for instance.  If different nets skip on the  panel, then
I suspect a more random error - incomplete tin strip, etc. I guess  it could
be marginally weak catalyst.   I would expect developer residues  to be random
pads - not all in a single net. Something "electrical" is going on  here.

Denny Fritz
MacDermid

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