Tin-lead alloys are widely used as solder in the electronics industry. For concerns of environment and human health, it is necessary to develop new bonding method using Pb-free material for microelectronic packaging. There have been some reports about low temperature bonding using Ag nanoparticles. Compared with Ag nanoparticles, Cu nanoparticles have some advantages, such as low cost and good ionic migration property. In this study we report a low temperature bonding process using Cu nanoparticles. The polymer coated on the surface of Cu nanoparticles can protect them from oxidation. Strong joints were formed at bonding temperatures as low as 180°C under 5MPa in air atmosphere. This novel sintering-bonding technology using Cu nanoparticles as interconnection material has a potential application for electronic packaging.