Effect of Sintered Silver Layer Porous Structure on Shear Properties of Sintered Silver Joint

The silver-plated copper sheet, micron silver solder paste and silver-plated copper sheet were stacked into a“sandwich”structure, and then the sintered silver joints were prepared by hot pressing and sintering under different sintering pressures (0, 0.5, 1, 3, 6 MPa). The effects of sintering pressure on the porosity, pore size and layer thickness of the sintered silver layer in the middle of the joint were studied. The shear property of sintered silver joints was tested by combining test and finite element simulation, and the influence of porous structure characteristics of the sintered silver layer on the shear properties of sintered silver joints was analyzed. The results show that with the increase of sintering pressure, the porosity of the sintered silver layer decreased from 19.3% to 7.5%, the average pore size decreased from 1 560 nm to 1 390 nm, and the layer thickness decreased from 67 μm to 36 μm; the fracture mode of the sintered silver joint changed from the mixed fracture mode to the interlaminar fracture mode, and the plastic deformation degree of the sintered silver layer increased. The simulation of interlaminar fracture micromorphology of the sintered silver layer and the load-displacement curve and shear strength of the sintered silver joint under different sintering pressures were basically consistent with the test results, and the maximum relative error of the shear strength under pressure sintering conditions was 13%, which verified the accuracy of the finite element simulation. As the porosity of the sintered silver layer increased from 7.5% to 15.1%, the deformation degree of the sintered silver layer decreased when the shear load reached the peak and the shear strength of the joint decreased by 40%. As the average pore size of the joint increased from 1 390 nm to 1 510 nm, the deformation degree of the sintered silver layer did not change much when the shear load reached the peak, and the shear strength of the joint decreased by 6%. As the layer thickness of the sintered silver layer increased from 36 μm to 53 μm, the deformation degree of the sintered silver layer increased when the shear load reached the peak and the shear strength of the joint increases by 24%.