Overview of three prevention process and design requirements in PCB

In electronic processing, the essence of "Three Prevention" is to apply a protective film on the protected surface, and the protective effect is related to the coating method and coating process. The spraying part is PCB Surface protection, dip coating can protect parts. Due to the fluidity of the coating and the non-uniformity of the substrate surface, the corresponding relationship between the coating times and the three prevention effects is determined.

Three prevention technical design requirements:

(1) In order to improve PCB For the insulation grade and corrosion resistance of the surface, the technology of cleaning free welding PCBA surface coating can generally be adopted.

(2) Effective three prevention protection is required, which must be painted in strict accordance with the three prevention technical requirements.

1. Protective elements:

Impregnation or sealing of transformers, coils, etc; The plug-in shall be protected by solid protective film; Special treatment of components.

2. Cleaning and drying PCB:

There are many rosin film residues in the non cleaning flux. On the one hand, it reacts with the three proofing paint to form pinholes. On the other hand, it crystallizes and expands after moisture absorption. Finally, the three process design prevents the coating from falling off. It requires good three proofing and must be cleaned.

It must be applied twice

For spraying, especially the use of solvent containing coatings, pinholes will appear after the film is cured. In order to achieve a good moisture-proof level, it must be coated twice. This is also one of the effective measures to ensure the coating thickness of the line. Generally, the thinnest coating thickness of the line shall be at least 25 μ M above (non line actually exceeds the standard, generally 25 ~ 225 μ m)。 Note: the effect of three prevention is related to the coating times and film thickness.

The most effective measure for offshore equipment is to seal the cabinet, which is the most important measure. Only by PCB The three prevention treatment is ineffective.

Three prevention main improvement PCB Anti corrosion level - the purpose can be achieved by covering the exposed place of Cu, isolating corrosive gas and moisture in the air, and destroying the conditions of vulcanization, electric movement, electrochemical corrosion and chemical corrosion.

The core of three proofing technology: three proofing paint, technology and film thickness. The effect of three prevention depends on the thickness of the paint film.

It should be pointed out that the three proofs only delay moisture absorption and cannot completely prevent moisture. If waterproof and dustproof are required, sealing technology shall be adopted.

Shenglan Technology Co., Ltd_ It focuses on the production of electronic connectors and research and development of precision components. Its products are widely used in consumer electronics, new energy vehicles, USB, 5g and other fields. Its industrial lines cover the Pearl River Delta, Southeast Asia and other regions. It has established long-term strategic cooperation relations with well-known enterprises such as Foxconn, Lixun precision, Huawei, Xiaomi, TCL, Hitachi Group, BYD and Great Wall Motors, with IATF 16949, ISO9001 ISO14001, QC080000 and other system certification and product safety certification, and provide professional connection and manufacturing solutions for the industry http://jctc.com.cn/