The solder mask exposure and development process in the PCB board manufacturing process is a PCB board with solder mask after screen printing. Cover the pads on the PCB board with diazo film so that they will not be irradiated by ultraviolet light during the exposure process, and the solder resist protection layer is more firmly attached to the PCB surface after ultraviolet light irradiation, and the pads are not exposed to ultraviolet light. Light irradiation can expose the copper pads so that lead and tin can be applied during hot air leveling.

The purpose of the circuit board exposure is to irradiate and block by ultraviolet light. The transparent part of the film and the dry film undergo optical polymerization reaction, that is, under ultraviolet light irradiation, the photoinitiator absorbs the light energy and decomposes into free radicals, and the free radicals initiate light again. The polymerized monomer undergoes polymerization and cross-linking reaction, and forms a macromolecular structure insoluble in dilute alkali solution after the reaction. The film is brown, ultraviolet light cannot penetrate, and the film cannot undergo optical polymerization with its corresponding dry film. Exposure is generally carried out in an automatic double-sided exposure machine.

There are two types of exposure: circuit exposure and solder mask exposure. The function is to cure the irradiated local area through ultraviolet light irradiation, and then develop it to form a circuit pattern or a solder resist pattern.

The process of circuit exposure is to put a photosensitive film on the copper clad board, and then put it together with the circuit pattern negative and expose it with ultraviolet rays. The photosensitive film irradiated by ultraviolet rays will undergo polymerization reaction. The photosensitive film here can resist Na2CO3 weak alkali during development. The solution is washed away, and the non-sensitized part will be washed away during development. In this way, the circuit pattern on the negative film is successfully transferred to the copper clad board;

The process of solder mask exposure is the same: apply photosensitive paint on the circuit board, and then cover the areas that need to be soldered during exposure, so that the pads are exposed after development.