A new nondestructive test technique using partial discharge method

DBC (Direct Bonding Copper-Ceramics) materials are more and more widely used in the power electronic industry because of their exceptional mechanical and electrical properties as well as high thermal conductivity. During the course of production, “air-filled voids” are often formed at the Copper-Ceramics interface due to locally imperfect bonding between the copper foil and the ceramic substrate, which can dramatically deteriorate the properties of the materials. So, it is necessary to measure the amount of voids inside DBC materials and reject the unqualified product. According to the characteristics of DEC materials, a model is established and it is found that these voids can change the capacitance of ceramic substrate, and the amount of change is determined by the amount of the voids. Therefore, dielectric capacitance and partial discharge measuring technique is a feasible approach to the non-destructive quality measurement of DBC materials. In this paper, the “parallelogram method” is used and it is proved to be effective by a large number of experiments. Theoretical analysis has also been conducted systematically and it agrees with the experimental results very well. Thus, a new practical method has been developed, which is much cheaper and less time-consuming than the common ultrasonic method