The principle of three defenses

It is a method of coating on a printed circuit board to form a protective film. This protective film is usually only a thin layer (about 30-210µm), which can be used to strengthen the moisture-proof, dirt-proof, dust-proof and chemical-proof of electronic products. The ability to contaminate can also prevent the solder joints and conductors from continuing to corrode in contact with the air, can shield and eliminate certain electromagnetic interference, and can also play a role in insulation.