Effect of Moisture Absorption on Dielectric Property and AC Breakdown Characteristic of Epoxy Resin Insulation

Epoxy resin (EP) insulation is widely used in electronic packaging because of its excellent electrical properties. In special working conditions, EP insulation is susceptible to moisture. It reduces the insulation properties and affects the stability and reliability of electronic equipment operation. In order to clarify the effect of moisture on the electrical properties of the EP insulation, the broadband dielectric spectrum, electrical conductivity and AC breakdown strength of the EP insulation before and after moisture absorption were tested in this study. It was found that water penetrates inside the EP insulation and undergoes a strong polarization in the presence of an electric field, with a consequent increase in the dielectric constant. Three mechanisms exist for the effect of water on dielectric properties in high-temperature environments. These are increased electrical conductivity loss in the low-frequency region, decreased dielectric loss in the mid-frequency region due to plasticization, and increased dielectric loss in the high-frequency region due to its own strong polarization. Weak areas for breakdown are formed by water in close contact with each other, reducing the AC breakdown strength of EP insulation.