You are correct. The gold dissolves in the solder. The gold is meant to protect the nickel from oxidizing, so that you can solder to the nickel.
Obviously that didn�t work as planned. Your background information is very sparse. Two things come to mind: 1 Corroded nickel. 2 Black pad. [Search the fine SMTnet Archives for background, articles, and gnashing of teeth.] [An additional article on black pad that is not referenced in the Archives is: Ken Crouse's article in a recent PCFab Magazine http://www.pcfab.com/db_area/archive/2002/0202/cullen.html ]
Continuing with your �surely due to the abnormal stress� theory, what is the abnormal stress on these boards? What do think caused the solder to separate like this?
Here�s what you need to tell us: * What is the breadth and extent of this problem? * Are the defective pads solderable? * Are the pads on a bare board solderable? * What are the color and texture of the pads on the defect board? ... [pix would be nice] * What kind of solder mask is on the board and when, relative to applying the gold plating, was it applied? * What is the % level of P was in the EN tank? * What kind of gold is on the board? * What are the actual thickness of the nickel and the gold, before soldering?
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