Soldermask and solder past layer on PCB When soldering a printed circuit board (PCB), areas that are not meant to be soldered are protected by a layer of solder resist, typically a polymer material that prevents short circuits and contamination. This layer, often green or red in color, is called the soldermask and can be applied to either or both sides of the board. The soldermask protects the conductive traces from shorting due to debris but must be selectively applied to leave component pads uncovered to allow electrical contact. Exposed areas of the board, such as pads and edge connectors, may be "tinned" or plated with solder, while gold plating is sometimes used for edge connectors due to its resistance to tarnish and good conductivity. Solder paste, used to assist in the soldering of surface mount components, is applied to the exposed copper regions, promoting better solder flow during bonding. When designing PCBs with surface mount components, solder paste files are required for both top and bottom layers where these
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