Thermal performance and reliability of high temperature SiC power module with direct-cooled stacked Si3N4 substrates

This work is concerned with the thermal performance and reliability of the SiC power module with direct-cooled stacked Si 3 N 4 substrates for high temperature applications. First, finite element thermal and thermo-mechanical simulations have been carried out on the half bridge switch-like module accommodating 4 SiC diodes of 20 A-3.3 kV. The simulation results can be used to justify the selections of direct-cooled stacked Si 3 N 4 substrates and high temperature die attachments in terms of good thermal performance and thermo-mechanical reliability. Then the corresponding half bridge switch-like module samples have been prepared using high temperature Pb5Sn, Zn5Al0.1Ge and sintered Ag joints to attach SiC diodes on commercially available stacked Si 3 N 4 substrates for transient thermal and thermal cycling tests. The test results cannot compare the thermal performance and thermo-mechanical reliability of the different high temperature die attachments, but reveal unusually high contribution and rapid increase of the thermal resistance from the brazed AgCuInTi joint in the commercial stacked Si 3 N 4 substrates. Further work is needed and ongoing for providing better understanding, while the results obtained so far reveal that new stacked substrates especially new brazing or bonding technology for producing the stacked substrates are required for the relevant SiC power module applications.