Mechanical Response of CuMo Alloy Spacer in Double-Sided Cooling Silicon Carbide Power Module Based on Nano-Cu Paste

With the development of chips towards high power and high current density, traditional single-sided silicon carbide (SiC) packaging structures are no longer able to meet application requirements. Double-sided cooling (DSC) power modules have great potential for application in SiC high-temperature packaging due to the excellent heat dissipation and low parasitic parameters. CuMo alloy spacer possesses mechanical load-bearing capacity and can play a role in supporting chips and electric thermal transmission. However, in most studies, nano-silver paste is used to connect chips with CuMo alloy spacer, which results in higher usage costs and lower mechanical reliability. In addition, there are differences in physical properties between CuMo alloy spacer structures with different alloy ratios, which can also lead to different electrical and thermal characteristics of DSC power modules. In this paper, we selected nano-Cu paste as the die-attach material and investigated the mechanical properties of DSC power modules with different Cu-Mo alloy ratios in spacer structures through finite element method (FEM). The mechanical response of DSC power module under temperature cycling service was revealed, including the influence mechanism of thermal stress distribution and thermal deformation behavior. The trend of plastic strain of nano-Cu paste with temperature cycling times and Cu-Mo alloy ratio was evaluated. The increase in Mo content changes the deformation mode of the nano-Cu paste, which results in residual stress increasing first and then decreasing. Large proportion of Mo was beneficial for alleviating the high deformation areas of the interconnect layer, but would exacerbate the deformation of SiC chips. The alloy ratio would affect the plastic strain of the paste layer, which could affect the service life of the DSC power module.