If you received flaking gold from an immersion process, I would not recommend using those parts. Gold should not be flaking. In addition, if the gold is flaking, how would you ensure the conductive flakes don't end up shorting components out? As a board manufacturer I can assure you we do not feel flaking gold is ever acceptable. The black edges can be a whole other problem. It sounds as if the part was not solder or tin stripped properly before the ni/au process. If that is the case, you could potentially end up with solderability issues and possibly a very brittle interface.  By no means am I  an expert on metallurgy but something sure sounds wrong with the picture you paint. I'm sure other responses will be more technical.

Just my thoughts...

Ed Cosper
Director Quality Assurance  and Engineering.
 
----------
From:  GuitarBud[SMTP:[log in to unmask]]
Sent:  Friday, April 17, 1998 10:00 AM
To:  [log in to unmask]
Subject:  [TN] NiAu Plating Problem

I recently received immersion gold finished boards from a PCB supplier where
some of the edges of the traces were black.  The gold was flaking or had a
bubbled appearance in areas as well.

I was told that the black was lead build-up from the plating bath since extra
lead was used to limit the reactivity of the bath.  I was also told that if we
could live with the flaking, the lead build-up was not a reliability concern
as long as we had good solderability.

Is it likely that it is only lead and that reliability is not a problem?

Frank

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