The correlation between the microstructure and mechanical property of low temperature sintering nano Ag paste

Power electronics are developing towards miniaturization, high power and high density. In respond, the increasing operation temperature brought by high packaging density and power density imposes higher requirements on die attachment. Ag nanoparticle paste is a promising interfacial material in high-power electronic packaging, which meet the demand of low-temperature bonding and high-temperature service. The sintered silver has similar physical characteristics to its bulk counterpart, such as high thermal conductivity, high electrical conductivity, high mechanical strength, excellent thermal shock resistance and high creep temperature. The evolutions of microstructure during sintering has a great influence on its bonding strength, deformation behaviors and even electrical and thermal properties. Previous studies barely described the relationship between mechanical properties and microstructure of sintered nano-Ag joints. In this study, the sintered Ag films with different microstructure were obtained by setting different sintering parameters. We characterized the microstructure morphology and mechanical properties of there sintered Ag films. It is found that the porosity of sintered bulk is mainly determined by sintering pressure, the size distribution and shape of pores are affected by sintering pressure and temperature and the coarsening behavior is controlled by sintering temperature. Meanwhile, mechanical properties of sintered bulk are mainly affected by porosity and intergranular microstructure, while the size distribution and shape of pores, ligament size and grain size have minor importance.