Photoresist is crucial in the photolithography process, which refers to polymeric material whose solubility changes after being irradiated or radiated by electromagnetic waves, such as ultraviolet light, X-rays and electron beams. It can be widely used in displays, integrated circuits, micro-electro-mechanical systems (MEMS), optoelectronic devices and other micrographic processing fields.
PCB is the abbreviation of printed circuit board. It refers to a medium with conductive and insulating layers on which electronic components are connected by circuits formed by conductive copper wires. There are several types of PCBs, including single-sided, double-sided and multilayered boards, and they can be rigid or flexible.
With photolithography, complex wiring of electronic systems can be reproduced rapidly, cost-effectively, and accurately in the same way as if they had been printed. So photoresists, as the key materials of photolithography technology, are used commonly in PCB manufacture.
Classification
PCB photoresist can be divided into dry film photoresist, photosensitive solder resist ink and wet film photoresist . The latter two are often collectively called PCB ink. The important physical properties of PCB ink are viscosity, thixotropy and fineness, which are closely related to the ability of ink.
A dry film photoresist is formed by uniformly coating liquid photoresist on a carrier polyethylene terephthalate (PET) film, baking and cooling, and covering with polyethylene (PE) film. The dry film photoresist is pressed on the copper-clad board, and circuit patterns are transferred to the photoresist after exposure and development. Upon subsequent etching and other processes, circuit patterns are formed on printed circuit boards. It is suitable for 75-100 μm process.
- Photosensitive Solder Resist Ink
Photosensitive solder resist ink is applied to form a permanent insulating protective layer on the circuit, which is helpful to prevent short circuits during soldering, ensuring PCB safety during transportation, storage and use. Photosensitive solder resist inks can be further divided into liquid photo imageable solder masks (LPI) and UV curable etching resist inks. Generally, UV curable etching resist inks are used for PCBs that do not require a high degree of precision, since they have poor adhesion. In contrast, LPI solder mask ink is usually used on high-density, high-precision printed circuit boards due to its excellent precision properties. In a word, photosensitive solder resist inks play a significant role in the manufacture of low-end and high-end electronic products.
Wet film photoresist is also known as liquid photosensitive state link ink. It can be classified into anti-plating ink and anti-etching ink. The process is similar to dry film photoresist with a lower material cost. Wet film photoresist is mainly used in the 25-75 μm process.
PCB is used in a wide range of electronic devices, including household electronics, sophisticated sensors in automotive, medical imaging systems, light-emitting diodes (LEDs), monitoring equipment required for aerospace, and some industrial equipment. Therefore, PCB photoresist plays an important role in several industries as well. Alfa Chemistry offers a wide range of PCB photoresists. Please feel free to contact us.
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