Current Sharing Behavior and Characterization of a 1200 V, 6.5 m Omega SiC Half-Bridge Power Module with Flexible PCB Gate Loop Connection

This paper describes 1.2 kV, 6.5 m Omega, half-bridge SiC MOSFET power module design, fabrication and initial testing exploring the benefits of flexible PCB gate loop connection and symmetrically patterned direct bonded copper (DBC). Paralleling power devices in modules increases current handling capability for the same bus voltage. Although simple, paralleling is challenging due to inherent parametric differences between dies and can lead to unbalanced current sharing causing overstress and thermal issues. Novel packaging techniques include use of the flexible PCB as the gate-source connection further reducing the possibility of external loop mismatches by using symmetric design for both switches keeping loop connections minimized. Furthermore, the DBC is patterned with symmetrical current pathways for both switches, thereby mitigating possible differences in the power loops. Therefore, variation in switching behavior can be attributed to the differences in the selected dies. Finally, the die are matched according to their threshold voltages so they turn on at the same time, increasing the likelihood of balanced current sharing. Static and initial dynamic characterization demonstrate efficacy of the techniques utilized for this power module.