Microstructural homogeneity of sintered Ag joint after pressureless sintering process

Ag sintering technology based on Ag paste is becoming an attractive alternative to soldering for high-temperature and high-reliability power electronics packaging. The Ag paste exhibits a complex viscous flow, during which solvent have a great effect on the movement, arrangements and distribution of Ag particles. These factors inevitably influence the porosity, pore size, and distribution of the sintered Ag joint, which furtherly determine the reliability of joint. However, few studies have focused on this. Herein, a structural inhomogeneity with changing porosity distribution in the Ag joint was observed after presureless sintering process. The porosity in the center of joint was far lower than that in the edge, which was closely related to interaction between particles and solvent. In addition, high-temperature aging process aggravated the degree of inhomogeneous microstructures, which will induce to the different distribution in thermal and mechanical performance in the joint.