Influence of thermal exposure upon mechanical/electrical properties and microstructure of sintered micro-porous silver

Abstract Silver sinter paste has been considered as promising joint materials for SiC and GaN power modules due to its excellent thermo-stability and high electrical/thermal conductivity. However, sintered Ag has experienced mechanical/electrical properties deterioration and microstructural variations under high temperature exposure. It is strongly related with reliability of power modules. Thus, we evaluated thermal exposure effects on the mechanical properties, electrical resistivity and microstructure of sintered micro-porous silver specimens under high temperature exposure of 250 °C. Silver paste was printed in a specimen shape of a tension test, and was sintered at 250 °C for 1 h in air with no pressure. The sintered silver was exposed for 0, 50, 200, 500, and 1000 h at 250 °C. Tensile strength and electrical resistivity were obtained at each aging stage. The tensile strength decreased and again recovered during high temperature exposure, while the electrical resistivity decreased. For microstructure evolution, sintered silver grains, porous structure and fracture surface were characterized by SEM and EBSD. The relationship between microstructural variations and mechanical/electrical properties was discussed in detail.