Dan

In the late 90's we saw a great deal of this and called it skip plating.
Unfortunately, it was often a precursor to black pad. We eventually
attributed it to the board design and the uniformity of the immersion gold
bath which created an opposing voltage that inhibited the immersion
process. The design issue had to do with long nets that ran from one end
of the board to the other. Eventually, many designers if they knew in
advance that ENIG was to be used confined the length of the nets. When
this was the case we seldom saw the problem. Obviously, this did not put
the horse back into the barn, but it will minimize future problems. For
current problems, process were institruted to keep the plating bath
homogeneous, sometimes by stirring which can cause other problems.

Best regards

Lee

J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389

Best regards

Lee

J. L. Parker Ph.D.
JLP Consultants LLC
(804) 779 3389


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dan Skweres
Sent: Monday, September 18, 2006 5:54 PM
To: [log in to unmask]
Subject: [TN] ENIG

We have, at times, had an outside plating service have difficulties with
plating of ENIG on our bare boards. The interesting anomaly we have
encountered is lack of plating on certain pads. They tell us there is
something on the surface of the pads but when they return the panels to us
we micro etch (copper looks beautiful) and all pads look similar in
appearance. We even took a panel and coated immersion white tin with out
problems. This tells me that there isn't any thing on the surface of the
copper. 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? It's
almost like there is a charge being created in certain nets not allowing
the ion exchange to happen. Could it be entrapped chemistry within vias?
Any help and/or direction would be greatly appreciated.
Thanks,


Dan Skweres
Engineering Manager
Bartlett Manufacturing
Phone:847-639-2102 Ext.#230
Fax:847-639-8838


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