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Strictly speaking, the manufacturing of PCBs in HDI factories is not simple. In addition, our common PCB boards are not only single-layer boards, but also multilayer boards, so the processing technology of manufacturing multi-layer boards is more complicated and the cost is higher; Generally speaking, the design and manufacture of PCB is a complex science, which requires professional PCB engineers to design; when you buy all large and small circuit boards on the market, these PCB boards are in use due to Will be in different environments, such as chemical substances (fuels, coolants, etc.), vibration, high dust, salt spray, humidity and high temperature, etc., so the PCB board itself is an extreme test. In these environments, the circuit board It is easy to produce softening, deformation, mildew, corrosion and other problems, which will lead to failure of the PCB board circuit.
Therefore, there is a substance called three-proof paint that plays a very important role. Three-proof refers to moisture-proof, anti-salt spray, and anti-mildew. It is a specially formulated paint that coats the three-proof paint on the PCB of the HDI board factory. On the surface, a three-proof protective film is formed. The protective film can protect the circuit from damage in the environment of chemical, vibration, high dust, salt spray, humidity and high temperature, improve the reliability of the circuit board, and increase its safety factor. In addition, because the three-proof paint can prevent leakage, it allows higher power and closer printed board spacing, which can meet the purpose of component miniaturization.
In addition, there is copper on each layer on both sides of the PCB. In the production of PCB, whether the copper layer is manufactured by additive or subtractive methods, a smooth and unprotected surface will eventually be obtained. Although the chemical properties of copper are not as active as aluminum, iron, magnesium, etc., in the presence of water, pure copper is easily oxidized by contact with oxygen; because oxygen and water vapor exist in the air, the surface of pure copper is exposed to air. Oxidation reaction will occur soon. Because the thickness of the copper layer in the PCB is very thin, the oxidized copper will become a poor conductor of electricity, which will greatly damage the electrical performance of the entire PCB.
In order to prevent copper oxidation, to separate the soldered and non-soldered parts of the PCB in HDI board factory during soldering, and to protect the surface of the PCB, a solder mask is also used. This kind of paint can be easily painted on the surface of the PCB to form a protective layer with a certain thickness and block the contact between copper and air.
