Try to use a two-step stripping process.  The first step to strip the intermetallic layer and the second step with no antitarnish.  Most two-step processes use an antitarnish in the second step for full panel stripping, and this could cause adhesion problems if not removed.

Ed

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Ed Wright	Technical Support 
Oliver Sales Company 	Phone:  (214) 231-1522
13445 Floyd Circle 	Fax:  (214) 644-3585
Dallas, Texas  75243-1595 	E-mail:  [log in to unmask]
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From:  [log in to unmask][SMTP:[log in to unmask]]
Sent:  Wednesday, April 24, 1996 7:08 PM
To:  [log in to unmask]
Subject:  gold plating problem

Our Process
Isolated tabs in the center of the board to be gold plated are defined by a primary layer of resist.  After copper and tin-lead plating them, we vacuum laminate 3 mil dry film resist.(over the plated tin-lead and over the primary layer or resist)  This top layer of resist is selectively imaged to produce an opening exposing the area to be gold plated (which now has tin-lead on it). Then the tin-lead is stripped, and the nickel and gold are plated using our usual sulfamate nickel/soft gold process. 
The Problem
The plated nickel peels from the copper surface.  The peeling is always near traces connecting to the tabs.  Therefore I suspect that tin-lead stripper is being trapped under the top layer of resist and coming out during plating. 
Solutions?
I don't suspect the nickel/gold process is the problem, as the usual yield on products without this tin-lead stripping step is nearly 100%. 
We have no option to change the design of the board to facilitate manufacturing. ie: No bussing of the tabs is possible therefore base copper must be used as a conductive path prior to etching.
We've tried: 140 degree F water rinse after stripping, conveyorized nitric tin-lead stripper, immersion and conveyorized peroxide tin-lead strip, a second strip cycle, UV bump (160mJ), among other things.
Any help would be appreciated.