The Effect of Nano-Cu Interconnection Materials on the Thermomechanical Properties of SiC Double-Sided Power Modules

Abstract:
The high porosity and high coefficient of thermal expansion (CTE) of nano-silver limit its application in SiC double-sided power modules, and the easy electromigration of nano-silver reduces its reliability. Stress fluctuations and residual stress during the sintering process directly affect the yield limit and fatigue strength of the power module and determine the reliability of solder interconnection. Therefore, this paper uses nano-copper slurry with lower cost and better CTE matching as the interconnect material for SiC double-sided power modules to solve these problems. Through finite element simulation, we conducted thermo-mechanical stress simulations on three SiC double-sided power modules whose interconnect layer materials are nano-copper, nano-silver, and SAC305. The results show that during the sintering process, compared with nano-silver, the stress fluctuation of the three layers of nano-copper slurry is greatly reduced, and the average residual stress is reduced by 33.58%, 14.79%, and 37.22% respectively. The thin interconnect layer thickness of 50um makes the steady-state junction temperature of the nano-copper module lower and has a heat dissipation capability comparable to that of nano-silver. During the sintering heating and cooling processes, the overall average stress of the nano-copper module was 11.76% and 4.98% lower than that of the nano-silver module respectively, proving that nano-copper has an excellent ability to alleviate stress concentration and improve the reliability of SiC double-sided power modules.