Steve:

Remember the process a PCB goes through prior to HASL....

Develop of soldermask
BAKE to set soldermask
Clean up of oxides caused by baking (usually microetch)
Flux
HASL

If you do not take ALL soldermask residue off during developing, that BAKE
puts it on almost permenantly.

And taking all the soldermask residue off during developing means turning the
solution over to keep mask contaminants in the developer solution low, and
GOOD rinsing.

Yeah, sure cleaners exist that will remove these residues after bake, but
properly done (and we all do things properly, at all times, don't we?) you
should not need it.

Rudy Sedlak
RD Chemical Company

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