Influence of Humidity on Thermal Resistance of Power Devices

Recently, more attention has been paid to the humidity-related failure of power devices, and some failure is related to thermal resistance increment at an early stage during aging tests. However, this phenomenon still needs further verification. In this article, the influence of humidity on the thermal resistance of power devices is studied based on three kinds of DUTs packaged with epoxy molding compound (EMC) and silica gel with/without baseplate. The results show that moisture can invade DUT and cause transient thermal impedance Zth variation in two aspects, one corresponds to the case surface of DUTs, and the other corresponds to the solder layer of DUTs.