Pressure Sintering of Micro-Silver Joints in SiC Power Devices: Optimization of Processing Parameters and FEM Analysis

The sintering process of micro-silver joints in SiC devices that operate in high temperatures has attracted considerable attention in recent years, owing to its advantages in low processing temperatures. The first part of this work carries out a thorough investigation into the effects of the processing parameters in pressure sintering on the shear strength and shear fracture surfaces of micro-silver joints. Optimization of the sintering parameters is then performed using orthogonal tests, validated by experiments, followed by an inspection of the microstructure of the sintered micro-silver joint. The second part of this work presents temperature and stress distribution analyses in the sintering process under the optimum parameters using the finite element method (FEM). The residual shear stress at the silver layer/SiC chip interface created during sintering is also examined. Results show that the shear strength of the silver joints increased significantly with the sintering temperature and time. The shear strength also increased with the sintering pressure initially, but a further increase in the sintering pressure (> 8 MPa) led to a decrease in the shear strength. Our findings demonstrate that the shear strength of the micro-silver joint may be correlated with the residual shear stress created during the sintering process. FEM showed that a further increase in sintering pressure resulted in an increase in residual shear stress, which reduced the shear strength. The optimum sintering parameters proposed for micro-silver joints based on these results are 290°C, 5 min, and 8 MPa, in which strong bonding strength of 44.31 MPa was achieved.