We have assumed  that there is a reaction between the mask and the Copper,
and an organo-metallic compound is formed, and this residue is insoluble in
developer or rinses.  The residue is largely, or completely invisible ( the
Emporers residue, only the faithful can see it.....!)

There are cleaners that will clean this residue away.  They must be used
prior to any microetch before HASL.

If you want information on one such cleaner, get back to me off Tecbnet

Rudy Sedlak
RD Chemical Company

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