In a message dated 96-09-26 15:40:13 EDT, you write: > 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. > The above is right on the money. Look into developer/rinsing issues. Some of these soldermasks leave residues in the developer/rinse that are essentially impossible to remove chemically, and will eventually clog nozzles, etc. Another approach that one of customers found, quite incidently, was that a mildly alkaline (pH = 9-10) cleaner did a marvelous job of cleaning up the surface before microetch, did not attack the mask, and allowed a minimal microetch to give a thoroughly clean, and wettable surface. Rudy Sedlak RD Chemical Company phone 415-962-8004 fax 415-962-0370 *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************