Influence of interfacial interaction on the reliability of the bond between encapsulation epoxy and copper substrate

Gel encapsulation is gradually replaced by epoxy encapsulation for power modules due to the miniature of epoxy encapsulation. The epoxy and the copper substrate form a dissimilar bond. Generally, the mismatch of the coefficient of thermal expansion (CTE) is thought as the reason for the bond failure. Here, we investigated the influence of copper/epoxy interface interaction on reliability under various reliability tests. It shows that besides the mismatch of CTE, the interfacial interaction also influences greatly. Copper diffuses into epoxy. The diffused copper causes epoxy degradation under high temperatures and humidity, which fails the copper/epoxy bond.