Thermal conductivity and interface thermal resistance evaluation of DBC/DBA in power die attach modules

For WBG power modules, it is critical to measuring the thermal conductivity of substrates at a high temperature exceeding 200deg C. In this study, the thermal conductivity of direct bonded copper (DBC) and direct bonded aluminum (DBA) substrate with different ceramics (Si3N4, Al2O3, AlN) were measured by the steady-state method, and criteria for improving the measurement accuracy was derived. The results revealed that the thermal conductivity of all the types of substrate decreased with increased measurement temperature. AlN ceramic show the best thermal conductivity in both DBA and DBC. The measurement accuracy of the thermal conductivity was analyzed from both points of the thermal resistance of nano-diamond greases and the temperature uniformity ratio of the upper and lower cartridges.