**4. Conclusions**

In this study, a power cycling test system based on a SiC micro-heater chip was developed to simulate the active SiC devices where the temperature of the heater chip can be recorded through the power cycling test in real-time. The new approach is useful for the evaluation of high-power devices with a similar condition to the real packaging system. The thermal resistance of of the SiC micro-heater chip power modules on DBC-AlN was lower than that of DBC-Al2O3 and DBC-Si3N4. In addition, thermal resistance of the SiC micro-heater chip power modules on the DBC-Al2O3 substrate tended to increase thermal resistance significantly with increasing power but there is almost not so much change for the DBC-AlN and DBC-Si3N4 with the same increased power. Furthermore, no delamination of the ceramic or degradation of the Ag sinter joint occurred during power cycling tests for both DBC-AlN and DBC-Si3N4, and it was clearly found that the temperature rise did not cause physical failure. The results exhibit that both DBC-AlN and DBC-Si3N4 are excellent candidates for high power modules with WBG semiconductor devices, suitable for industries demanding high energy efficiency, when the packaging like the die-attach and the cooling system is well optimized.

**Author Contributions:** Conceptualization, S.N. and K.S.; methodology, Y.Y.; software, S.N.; validation, C.C.; formal analysis, N.W., D.K.; investigation, D.K.; writing—original draft preparation, D.K.; writing—review and editing, C.C. and S.N.; visualization, D.K., C.C. and S.N.; supervision, K.S.; project administration, S.N. and K.S.; funding acquisition, S.N. and K.S.

**Funding:** The present study is supported by the METI project: Standardization for Energy Conservation as International Standardization of Thermal Property Measurements for Next Generation Power Electronics. The authors are grateful to all the members of the standardization project. The present study is supported by Yamato Scientific. Co. Ltd.

**Conflicts of Interest:** The authors declare no conflict of interest.
