In daily life, for the solder mask color of PCB circuit board, green is the most seen. With the progress of the times, various ink colors such as red, blue, purple, black and pink have been gradually introduced.

Liquid Photo Imaging Solder Mask for Circuit Boards, commonly referred to as LPI or LPISM, is a two-component liquid ink that is mixed before application to preserve its shelf life and is a relatively economical product designed for spray, curtain or wire coating Designed for screen printing applications. Masks are mixtures of solvents and polymers that form a thin coating that adheres to different surfaces of the PCB. Masks typically accomplish the original purpose of soldermask by coating areas of the circuit board that do not require any of the various final plating finishes available today. Unlike older epoxy inks that use shielding pads that require solder or other finishes, LPI inks are sensitive to UV light. The PCB board panel is completely covered by a mask, and after a short "sticky cure cycle" is exposed to a UV light source by using photolithography (exposure through a film tool or laser direct imaging with a UV laser).