We provide primarily surface finishing services to the printed circuit 
     board industry so about 80% of our business is deep tank nickel gold 
     plating.  We pumice scrub all panels prior to resist lamination unless 
     the panels have already been through a solder mask operation.  Our 
     preplate cleaning steps consist of a 15% sulfuric clean followed by a 
     25 microinch etch with sodium persulfate based etchant.  In the 5 
     years that I have been the engineer for the nickel/gold plating 
     operation we have never had one defect due to poor adhesion to the 
     copper.
     
     Michael Holan
     Process Engineer
     Radian International, LLC
     Electronics Div.
     512.310.4209
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: FAB: Manual Scrubbing prior to NiAu
Author:  [log in to unmask] at INTERNET
Date:    6/6/96 11:09 AM


Address,
     
EXPLANATION:
     
I have been conducting some experiments on the use of mechanical 
and chemical scrubbing on panels prior to resist lamination.  We 
currently perform a mechanical scrub to all panels prior to resist 
lamination.  
     
Based on minimal testing, we are successful in chemical cleaning 
panels prior to resist lamination with no resist breakdown in 
deep electrolytic Ni and Au.  However, in the test process 
we conducted a tape test and discovered NiAu peel from the base 
copper (no electrolytic copper applied due to reason of test).
     
The NiAu peel from the copper occurs on mechanical scrubbed 
and chemical clean sample panels, but on different sides.  The
mechanical scrubbed panel has peel on the component side and the 
chemical clean panel has peel on the solder side.
     
So the problem now points to the method in which we prepare 
panels prior to Ni and Au plating.  To insure good adhesion 
between Ni-copper and Au-Ni, panels are manually scrubbed with an 
abrasive pad.  Recent observation shows there is a large
variable associated with this type of method.
     
QUESTION:
     
-I would like to discuss with other manufacturers who use deep 
 Ni and Au plating?
     
-What types of methods are others using to prep panels prior 
 to Ni and Au plating?
     
-Is the method chemical or mechanical and if mechanical how are
 variables minimized?
     
Please advise.  Thank you.