Package Design Optimization for Electrical Performance of a Power Module using Finite Element Analysis

This paper presents the development of a high power module package having improved its electrical performance optimizing the package structure and the circuit layout on a substrate throughout Finite Element Analysis (FEA). The result of FEA shows that the modeling is finely calibrated from the verification, that is, comparing it with actual measurement values of several types of design configuration. This module package is used for synchronous rectification and contains MOSFETs, resistors and a driver IC. High electrical current over as much as 100A should flow through the devices, interconnect materials, traces and the Cu leads of the package. In order to decrease the on-state resistance or R_DS(ON), the package design needs to be investigated to find ways of improving the high electrical resistance paths such as the interconnect wires and traces. The authors initially worked on a simple 3D Finite Element Model using a commercial Finite Element Analysis (FEA) software ANSYS® and correlated the results with an actual experiment. After establishing the model, a variety of bonding configurations of Aluminum wire bonding and Cu clip bonding are investigated to achieve the optimum R_DS(ON), and modifying the design of the leadframe is also studied. Aside from improving the electrical resistance, it is also necessary that the circuit will have a comparable R_DS(ON) value so that the thermal effects of the individual devices would be similar.