I believe the advantage Persulfate has over peroxide sulfuric in 
     removing residues is it's undercutting ability due to the nature of 
     the etch.   At a previous job, I had used the Persulfate to do what 
     you suggest. I also have learned that it is better to spend the 
     resources trying to fix the residue problem than band-aid the problem 
     with a more aggressive etch.  What I found was that unless you want to 
     etch huge amounts of Copper to undercut the mask residue, the fix will 
     work when the residues are mild, but fail when they get bad.
     
     


______________________________ Reply Separator _________________________________
Subject: HASL Microetch
Author:  [log in to unmask] at corp
Date:    9/26/96 11:12


Does anyone have information, opinions or preferably data regarding micro 
etching with persulfate vs sulfuric acid/peroxide chemistries? We are 
currently using a sulfuric acid/peroxide based microetch at the HAL line, and 
are considering alternatives. I have seen some information which suggests a 
persulfate based chemistry is better at removing solder mask residues.  Any 
feedback would be appreciated.
     
Jim Kenny
     
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