Pressureless and low temperature direct bonding on Si, SiC and GaN via Ag paste sinter-joining

Ag paste sinter-joining is an important connection method for die attach used for high-temperature applications. In this work, we report direct bonded Ag joints with Si, SiC and GaN by using Ag paste sinter-joining. The joints with no surface metallization are directly bonded via a sintered Ag flake paste. The shear strength of the Ag joint reaches a bonding strength of over 40 MPa under a pressureless, atmospheric sintering condition at 250°C. By investigating sintering properties of the Ag flake paste, cross section of Ag joints, and bonding interfaces, it is found that the direct bonding was mainly attributed to excellent sinter-ability of the Ag flake paste, which not only allowed to obtain a well sintered porous Ag structure but also wetting of sintered Ag on the bare surfaces.