Comparative Evaluation of Kelvin Connection for Current Sharing of Multi-Chip Power Modules

Abstract

High-capacity power module with multiple parallel chips is a key component for renewable energy applications. Imbalance electro-thermal stresses among the parallel chips challenge the high-capacity power modules. Advanced packaging is considered as a promising solution toward higher capacity of power modules. In this paper, based on a commercial wire-bonding packaging, to enhance the current sharing in the multi-chip insulated-gate bipolar transistor (IGBT) power module, the capability of Kelvin connection to overcome the imbalance transient current and switching loss among parallel chips is comparatively surveyed. Taking parasitics into account, equivalent electric circuit and finite element analysis are proposed to illustrate the influences of Kelvin connection. Based on the customized power modules and a double-pulse test rig, simulation and experimental results are presented to comprehensively demonstrate the current sharing of parallel chips affected by Kelvin connection. It reveals the Kelvin connection can boost switching speed and reduce switching loss. However, the capability to eliminate imbalance current by using Kelvin connection is limited. Optimized direct bonded copper (DBC) layout to eliminate the asymmetric parallel loops is needed for multi-chip modules.