The sealing of AC DC power supply module is very important. This process not only involves the protection of AC DC power supply module (waterproof, moisture-proof, dustproof, corrosion prevention, etc.), but also involves the thermal design of AC-DC power supply module.

Power module potting materials are commonly divided into three categories: epoxy resin, polyurethane and silicone rubber

Because of its hardness, epoxy resin cannot be used for stress sensitive and module encapsulation with SMT components, so it is basically eliminated in module power supply. However, due to its low cost, the epoxy resin is also used in micropower power sources with high cost requirements. Some domestic manufacturers of defective power supply also use this epoxy resin for AC DC power supply module, but due to the stress problem, the failure rate of this power supply is very high, the buyer is suffering.

At present, most of the power modules are sealed with molded silica gel, which is usually in a 1:1 ratio to facilitate operation. When designed for AC DC power modules, attention should be paid to the thermal conductivity. However, the bonding ability is not very strong, so a substrate coating can be used to improve the sealing.

Polyurethane has been used in China for a period of time, but due to its high hardness, inconvenient maintenance, coupled with silicone rubber price factor, polyurethane is not cost-effective. Domestic basically disappear its application.

Special attention should be paid to the thermal conductivity related to thermal design. In general, the thermal conductivity of 0.5w /M·K is defined as high thermal conductivity, and that of greater than 1 is defined as very high thermal conductivity.