Sintering mechanisms and mechanical properties of joints bonded using silver nanoparticles for electronic packaging applications

The low-temperature bonding process using metal nanoparticles has attracted considerable attention due to its potential applications including electronic packaging. However, the fundamental understanding of this advanced bonding technology is still limited. In this study, Ag nanoparticle paste used as a bonding material is prepared by the chemical reduction method. The sintering behaviors of Ag nanoparticles during the bonding process were investigated using the classical sphere-to-sphere approach. At low sintering temperatures (160–250 °C), the calculated mechanism-characteristic exponent n is 7.9, which indicates that surface diffusion is the dominant diffusion mechanism. With the increase of temperatures (300–350 °C), mechanism-characteristic exponent n changes to 3.75. This indicates that volume diffusion is probably the prevailing diffusion mechanism at this stage. Based on the classical sphere-to-sphere model, the relationship between the joint strength evolution and neck growth of Ag particles is revealed. It is found that the joint strength is proportional to square of neck size ratio (x/r)2 of sintered Ag particles.