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April 1997

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Subject:
From:
Ed Cosper <[log in to unmask]>
Date:
Tue, 15 Apr 1997 09:31:31 -0500
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Have you checked your plating racks for possible fractures or breaks under the coating ( if you use coated racks)?  I have seen similar instances that you describe- but not with the border condition- when there is intermittent continuity thru the racks.  Also, the sulfuric concentration and brightners have a direct impact on how the panels plate. Have these been checked? Does the hull cell show a problem?  These are just a few thinks to check. I would recommend calling your supplier if the problem is not readily identifiable. 

Ed Cosper
Graphic Electronics Inc. 

----------
From:  sam mccorkel[SMTP:[log in to unmask]]
Sent:  Tuesday, April 15, 1997 8:31 AM
To:  [log in to unmask]
Subject:  FAB: Plating mystery

We're experiencing a strange phenomenon at copper and tin plating. We have 3
copper baths with a separate rectifier for each. Some boards will only plate
a thin layer of copper and then a thin to no amount of tin. A strange, but
consistent occurrence is a perfect image of a "frame" around the outside
edge of the board that does not plate at all. This "frame" SHAPE is from the
tape that we use to adhere our artwork to glass packs while imaging. The
tape DOES NOT contact the board, it's between the glass pack and the
artwork. We have not changed anything and it suddenly is happening. There is
no dry film breakdown, no copper adhesion problem, and no copper voids.
Also, it does not happen on all boards, it's lot specific. Lots that have
this problem have a larger area of copper burned away from the contact area
of the plating rack. Boards that plate properly will have a small area of
copper burned away at each contact. We also found that if we scotch brite
the contact area, before plating lots that have been identified as having
this phenomenon, they plate better. Any help with this mystery would be
greatly appreciated!

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