Wednesday, 3 October 2018: 14:40
Universal 5 (Expo Center)
We are developing a SiC power module that can operate at high temperatures. The high temperature operation of the power module has advantages such as increase in the output power of the converter and miniaturization. When the power module operates at high temperatures, reliability of large area solder such as ceramic substrate-to-baseplate bonding is decreased due to the thermal stress. Furthermore, to minimize the size of the power module, reduction of the thermal resistance is required for the baseplate. We demonstrated that mechanical specification and thermal specification of baseplate materials applicable to SiC power module that can operated at high temperature up to 250 °C. Figure 1 shows the overview of the test module structure. Table 1 shows the specification of baseplate materials. We investigated shear stress on the substrate-to-baseplate solder (BP-solder) can be suppressed with lower Young's modulus baseplate. Figure 2 shows the shear stresses of the BP-solder with various baseplate materials different in coefficient thermal expansion (CTE) and Young's modulus by finite element method (FEM) simulation. This result revealed the baseplate with copper-molybdenum-copper (CMC) has better thermo-physical properties and also lower Young's modulus than other baseplate materials. Figure 3 shows the transient thermal resistance measurement result according to baseplate materials. The CMC baseplate has been shown to have equivalent thermal resistance to the Cu baseplate. In figure 4, the CMC baseplate shows that the shear stress on the BP-solder was small and the better thermal characteristics than other baseplate materials. As the result, it was shown that by applying the CMC baseplate, it is possible to manufacture a power module with better solder reliability and thermal characteristics than other baseplate materials for the high temperature SiC power module.
Acknowledgement
This work was supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), "Next-generation power electronics / Consistent R&D of next-generation SiC power electronics" (funding agency: NEDO).