Solder Mask (S/M) Solder Mask, Solder Mask, and Solder Mask Although the Solder Mask is more general, it is more like a Solder Resist. The so-called solder mask refers to the part of the circuit board surface that is not intended to be soldered. It is covered with a permanent resin film and not tinned. This layer is called S/M. In addition to solder masks, green paint can also protect and insulate the covered circuits. Vertical-Cavity Surface-Emitting Lasers Vertical-Cavity Surface-Emitting Lasers,Vertical External Cavity Surface Emitting Laser,Vertical Cavity Laser,Vertical Emitting Cavity Surface Laser AcePhotonics Co.,Ltd. , https://www.cgphotonics.com