Ag particles for sinter bonding: Flakes or spheres?

This paper examines a unique mechanism in Ag micrometer flake sintering which reveals that self-produced Ag nanoparticles, created by the heating of the sintering process, contribute to larger necking and lead to enhanced bonding strength. Ag nanoparticle production, followed by rapid crystal growth, realizes faster mass transfer than spherical Ag submicrometer particles governed by conventional atomic-scale thermal diffusion at the particle surface. Thus, the Ag flakes provide thicker necking, resulting in higher shear strength of the bond layer. The natural properties of the initial particles have obvious differences: Only the flakes have a certain microstrain due to the higher dislocation density of the crystalline structure. The release of microstrain in the flake particles during heating leads to the production of Ag nanoparticles, which is a significant driving force in the sintering process.