Methods for increasing the Partial Discharge Inception Voltage of Power Module Substrates using Guard Ring Structures

This paper proposes novel geometric methods for reducing the maximum electric field of direct bonded copper (DBC) substrates, which can contribute to higher partial discharge inception voltage of medium-voltage power modules. The technology is based on the addition of guard ring structures pinned to a specific voltage between the high-voltage and grounded islands on the top layer, with the possible extension of removing the bottom-layer copper opposite the top-layer trench. In addition, a low-cost geometric solution is proposed to obtain the optimal guard ring voltage even under varying potential using an integrated voltage divider. The performance of the proposed methods is verified using finite element simulations and partial discharge (PD) experiments. The results show that by applying these methods, the maximum electric field can be decreased by up to 40%, and the partial discharge inception voltage (PDIV) can be increased by up to 39%.