A technique in which the solder mask is applied in advance of the tin-lead plating. This results in lighter circuit boards because the tin-lead alloy is only used to plate the pads.

Soldermask Over Bare Copper

Solder Mask Over Bare Copper. A printed wiring board manufacturing technique whereby solder mask is applied over bare copper, exposed and developed, and then the board is dipped in molten solder to coat the exposed copper.