Introduction to the three-prevention process of the circuit board and its cause analysis

Moisture is the most common and destructive factor for PCB boards. Excessive moisture greatly reduces the insulation resistance between the conductors, accelerates high-speed decomposition, lowers the Q value, and corrodes the conductor. The three anti-treatment processes of PCB circuit boards, currently I know three main types: three anti-paint, electronic wax, nano-coating.

Circuit board three anti-paint, also known as circuit board three anti-paint, is a specially formulated coating to protect the circuit board and its related equipment from the environment, thereby improving and extending their service life and ensuring the safety of use. Sex and reliability. Circuit board three anti-paint can be divided into acrylate, silicone, polyurethane three anti-paint from the chemical composition. Generally, brushing, spraying, soaking and other processes are adopted. After the coating is dried and solidified, a protective film is formed to protect the circuit board from moisture, salt spray and mildew. This is also the most used in the electronics industry. A wide range of three prevention processes. Due to the volatility and irritating odor of the three anti-paints, special rooms and equipment are required to complete the operation to reduce the health hazard to the operator. The three anti-paint process includes pre-slag removal, cleaning, solder paste protection, solvent dilution, dip coating, drying, and de-protection. The process is cumbersome and the working time is relatively long. The entire process is completed for more than 12 hours. If the circuit board dip-coated with three anti-paints is reworked, it will damage the coating and affect the three-proof effect of the board.

The soaking process of the circuit board is to melt and melt the electronic wax of two different melting points according to a certain ratio, and then directly immerse the circuit board in the wax water, and then take it out to dry. The process is mainly divided into four steps of proportioning, melting, soaking and drying. It is simple and convenient to operate, has no irritating odor, low cost, and does not affect welding and circuit board maintenance. It can also be good for solder joints. Protection. The process of immersing electronic wax mainly considers the influence of the softening point of the electronic wax on the product. Since the general industrial white wax is blown at about 60°, for the outdoorly installed smart water meter, the temperature inside the module is likely to be in the case of direct sunlight at high temperature. When it reaches 60°, it causes the wax to melt and does not play a good protective role. Therefore, the softening point of the electronic wax is improved by a suitable ratio and process to provide better protection.

The nano-waterproof coating for circuit board is a colorless transparent, non-toxic and harmless, non-combustible liquid nano-material which is protected from moisture, moisture and salt spray, and is generally brushed, sprayed, immersed and the like. Its characteristics are shorter film forming time, surface drying and dry time are obviously faster than ordinary three anti-paint; the film thickness is thinner than the three anti-paint, the surface of the PCB after coating appears cleaner and neat ; A few micrometers, so the heat dissipation is stronger and the heat is faster. However, the current cost of nano-waterproof coatings is relatively high, mainly used for current smart wear, portable electronic terminals and other electronic products PCB waterproof and moisture-proof .