I use Ostech 953 Soldermask remover, and make a dam of peelable mask
around the area to be removed.
http://www.os-tech.com/ostech.html

OS-953* Dry Film Solder Mask Remover is an aqueous, alkaline liquid
designed to remove fully cured dry film solder mask and most
photoimageable solder masks from printed circuit boards.  OS-953*
removes solder mask with much shorter exposure time than most
competitive products.  Solder mask is removed without damaging the
circuitry or epoxy laminate.
Michael Wolf
EH&S Manager
EVI Technology LLC
7138 Columbia Gateway Drive
Columbia MD 21046
Phone # 443-542-2826
Fax      # 410-290-1925
[log in to unmask]
www.evitechnology.com

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