Moisture is the most common and destructive factor to PCB circuit boards. Excessive moisture will significantly reduce the insulation resistance between conductors, accelerate high-speed decomposition, reduce the Q value, and corrode conductors. Currently, there are three main types of three-proof processing technology that I know about PCB circuit boards: three-proof paint, electronic wax, and nano-coating.
Circuit board conformal paint, also known as circuit board conformal paint, is a specially formulated coating used to protect circuit boards and related equipment from the erosion of the environment, thereby improving and extending their service life and ensuring safe use. performance and reliability. Circuit board conformal coatings can be divided into acrylic, silicone and polyurethane conformal coatings in terms of chemical composition. Generally, processes such as brushing, spraying, and soaking are used. After the coating is dried and solidified, a protective film will be formed to protect the circuit board from moisture, salt spray, and mildew. This is currently the most commonly used in the electronics industry. Extensive three-proof technology. Due to the volatility and pungent smell of conformal paint, dedicated rooms and equipment are required throughout the entire operation to reduce the harm to the operator’s health. The three-proof paint process roughly includes slag removal, cleaning, solder joint protection, solvent dilution, paint dipping, drying, deprotection and other processes. The process is cumbersome and the working hours are relatively long. The entire process takes more than 12 hours to complete. If the circuit board dip-coated with conformal anti-paint is reworked and welded, the coating will be damaged and the conformal anti-corrosion effect of the circuit board will be affected.
The soaking process of the circuit board is to heat and melt two kinds of electronic wax with different melting points according to a certain ratio, then directly soak the circuit board in the wax water, and then take it out to dry. This process is mainly divided into four steps: proportioning, melting, soaking, and drying. It is simple and convenient to operate, has no irritating smell, is low in cost, does not affect welding, and is convenient for circuit board maintenance. It can also have a good effect on welding points. protective effect. The process of soaking electronic wax mainly takes into account the impact of the softening point of electronic wax on the product. Since the fuse of general industrial white wax is around 60°, for smart water meters installed outdoors, under high temperature direct sunlight, the internal temperature of the module is likely to increase. Reaching 60° will cause the wax to melt and cannot provide a good protective effect. Therefore, appropriate proportions and processes are used to increase the softening point of the electronic wax and provide better protection.
The special nano waterproof coating for circuit boards is a liquid nano material that is colorless, transparent, non-toxic, non-flammable, moisture-proof, salt-spray corrosion-proof, and generally adopts brushing, spraying, soaking and other processes. Its characteristics are shorter film formation time, surface drying and full drying time are significantly faster than ordinary conformal paint; the film thickness is thinner than conformal paint, and the PCB surface after coating appears cleaner and tidier; because the film layer is only A few microns, so the heat dissipation capacity is stronger and the heat evaporates quickly. However, the current cost of nano-waterproof coating is relatively high, and it is mainly used for waterproofing and moisture-proofing PCBs of electronic products such as smart wearables and portable smart terminals.
