With the rapid development of electronics industry, on the printed circuit board (PCB) of the welding process and welding quality requirements higher and higher. Previous thermal curing and UV curing resists are using screen printing of graphics. Complete coverage from the line, size precision, consider using silk screen graphic methods have been incompatible, so the researchers developed a dry film resist. But the dry film resist because of its inherent limitations, can not fully meet the performance requirements of PCB, although technically its resolving power can reach nearly 25 m, but the scale is the actual production can be 75 ~ 100 m. The development of electronic technology, has asked the resolving power of high-density PCB on the forefront of the 75 m, and will be developed to 50 m, or even fine lines. Therefore, the urgent need for new photoresist, the resolving power to a higher level, especially at the board’s inner board manufacturing. In addition, PCB price competition, are becoming increasingly fierce, forcing manufacturers to ensure that the PCB PCB quality and performance of the premise, do everything possible to reduce the PCB manufacturing costs. Dry film resist according to their structure characteristics, its cost is difficult to reduce. In addition, the high-density PCB pad area required to minimize, or even a “no” pads, dry film resist is difficult to adapt to such a request. Therefore, many PCB manufacturers to shift attention to the liquid photoresist [1 ~ 5].
Present a new generation of liquid photoresist is an outstanding representative of the liquid photosensitive imaging inks (also known as wet-film resist) and the electrodeposition liquid photoresist (ED resist). Resist using these new, easy to get high resolution. For example, the usual source of non-alignment and standard imaging devices, imaging obtained after the resolution of 50 m. The use of a collimated light source, as long as the clean environment and ensure the appropriate base map conditions, the resolving power of up to 25 m. Outer or inner layer in the subsequent etching process, as compared with the dry film, liquid photoresist etching can give excellent results. This high resolution allows fine line PCB manufacturers can produce very low defect density of the product, and higher yield.
Photosensitive resist ink is a liquid solution developed for fine wire drawing production of a printing ink, commonly known as the wet film. It overcomes the thermosetting resist ink and dry production process in a number of challenges for fine wire and fine wire production. The most thin wide reach in 2. 54mm centered between the two pads three wires (0. 125mm) or four wires (0. 075mm), can also be used for high-precision craft, stencil mask, gravure printing production purposes, can be used to produce multilayer inner layer of fine wire. It consists of photosensitive resin, photosensitive agents, fillers, additives, pigments and solvents. Ink resolution up to 50 ~ 100 m, and good adhesion of copper clad board, there does not exist in the dry film production arising from the edge of the interface of bubble diffusion coating thereby causing the wire spikes, gaps, short circuit and other Defects. Ink is usually yellow light area in the security context of the handling, storage of about one year. Liquid photo plating resist ink of a brief technical operation procedures are as follows: