Development of High Power and High Junction Temperature SiC Based Power Packages

In this paper, a half-bridge leg single phase power package with SiC based MOSFETs (metal-oxide semiconductor field-effect transistors) on a AMB (active metal brazing) substrate was developed. The developed power package consists of a AMB substrate with specially designed cavities, four high power rated SiC chips, three types of customized copper clips forming the source and gate interconnects. High temperature die attach/solder material for the chip, substrate and copper clip bonding, and high temperature endurable encapsulation mould compound (EMC) for cavity and gap filling have been evaluated. The fabricated power packages were undergone the specified reliability assessments, i.e. unbiased highly accelerated stress test (HAST) test, thermal cycling (TC) test (-40~200°C), High temperature storage (HTS) test at 250oC and power cycling test (ΔT=150°C). 5 out of 5 samples passed the standard unbiased HAST test and HTS test for 500 hours. 4 out of 5 samples passed the TC test for 1000 cycles and 3 out of 5 samples passed the power cycling test for 10000 cycles. Electrical open failures were detected between clip 1, traces on the substrate and gate pads of the SiC chips. Interconnects between clip 2/3 and source pads of the SiC chips show good connections. Delamination between the clip 1 and sintered Ag were observed on the failed samples by the cross section failure analysis which is the potential root causes of electrical failure.