Abstract
In this paper, a novel method of Cu-Cu bonding by using the Cu nanosolder paste was proposed. The pure Cu nanoparticles used for preparing the Cu nanosolder paste were synthesized with simple routes and relatively high yields. The Cu nanoparticles were homogeneously dispersed with an average size around 60 nm. The sintering and bonding performance of Cu nanosolder paste were investigated, while an Ar-H2 gas mixture atmosphere was introduced in the whole experimental process to provide an antioxidative environment. In order to research the sintering properties, we conducted the sintering experiment in the sintering temperature range of 200 °C to 300 °C without any pressure. The Cu nanosolder paste represented significant fusion phenomenon and macroscopic color changes after sintering at 300 °C, and a low sintered layer resistivity of 12×10-8 m can be achieved. The Cu-Cu bonding experiment was proceeded at the same temperature range as sintering, with a bonding pressure of 0.98 MPa. After bonding at 300 °C, the bonding interface showed compact microstructure, and the shear strength of the bonded joint can reach a high level of 28.78 MPa. The high Cu-Cu bonding strength and the low condition requirements of bonding process indicate that the Cu-Cu bonding by using the pure Cu nanosolder paste is a promising method in 3D-IC packaging.