Daohui Li

Reliability design of direct liquid cooled power semiconductor module for hybrid and electric vehicles

Abstract With the global interests and efforts in popularizing low carbon vehicles, automotive power module has been becoming one of the fastest growing sectors in power semiconductor industry. As working in a harsh environment, the performance and reliability requirements of automotive module are stringent than industrial products. In this work, an integrated direct liquid cooled power module with enhanced reliability for hybrid and electric vehicles (HEV/EV) is developed. The design and assembly of the module were optimized in terms of performance, weight, cost and reliability. The module is integrated Al direct liquid cooling structure, leading to about 40% reduction of weight and cost and almost 50% reduction of junction to heat sink thermal resistance. Therefore, the junction temperature stays below the upper limit at the worst operation case which enhances the thermal reliability and lifetime. By incorporating advanced die lead bonding, the parasitics can be reduced by 50%, which is beneficial to efficiency and reliability. Furthermore, the die and terminal attach technologies are investigated to improve reliability. The lifetime prediction under a typical driving cycle shows that the proposed module is capable of working in the whole vehicle service period.

Improved surge current capability of power diode with copper metallization and heavy copper wire bonding

Copper metallization and copper wire bonding of high power semiconductor devices have attracted growing attention in recent years due to potentially much improved reliability and increased lifetime. However, significant technical challenges still remain for its wide commercial use. Here a thick copper layer has been successfully grown onto 3300V fast recovery diodes and subsequently 16mil copper wires were used to bond the chips onto substrates. Much improved surge current performance of these copper metallized and heavy copper wire-bonded diodes over its aluminium counterpart is reported here, and the results are analysed with the help of simulation.

3D multiphysics modelling of high voltage IGBT module packaging

140mm×190mm×38mm dimension single-switch high voltage insulated-gate bipolar transistor (IGBT) modules have been widely used in traction, high voltage converters as a standard package. The internal structural design and assembly processes have always been optimized to achieve lower parasitic inductance of the internal busbars, better thermal/mechanical characteristics of substrate and whole module. In this paper, 3D modelling technologies have been utilised for the electrical, electromagnetic, thermal, mechanical (multiphysics) aspects to speed up the design cycle and reduce the expensive research and development costs. By applying 3D modelling and simulation techniques, a 30% parasitic inductance reduction has been achieved.

Influence of Paralleling Dies and Paralleling Half-Bridges on Transient Current Distribution in Multichip Power Modules

This letter addresses the transient current distribution in the multichip half-bridge power modules, where two types of paralleling connections with different current commutation mechanisms are considered: paralleling dies and paralleling half-bridges. It reveals that with paralleling dies, both the high-side and low-side paralleled devices experience a similar transient current imbalance due to the mismatched stray inductance. However, with paralleling half-bridges and with the same mismatched stray inductances, the high-side paralleled devices have much smaller transient current imbalance, the cause of which is found be to the current commutation process. Theoretical analysis based on the circuit modeling and current commutation process elaborates the findings, which are then confirmed by experimental results.