Synthesis and characterization of highly-dispersed copper submicron particles for low temperature sintering joints

The wide band-gap semiconductors are increasingly used in high-power devices. Due to the increasing operating temperature of high-power devices, stringent matertial properties are required. Nano-Ag paste has been widely utilized in the interface connection of high-power devices. However, sintered Ag has migration and cost concern. Compared with Ag, copper is cheaper and has comparable electrical and thermal properties. Cu nanoparticles(CuNPs) are likely to aggregate and oxidizd, which prevents its application. It is indicated that the particle size of copper should be controlled carefully, by which high sintering performance and aggregation and oxidation resistance can be achieved. In this paper, antioxidant and highly-dispersed Cu submicron-particles(CuSPs) with an average particles size of 500 nm were synthesized. Polyvinyl pyrrolidone and ascorbic acid were used as mixed capping agents to enhance antioxidant properties and dispersibility. According to the result of XRD, peaks of oxidized copper were not detected. The Cu-Cu joints were prepared with pressure sintering in vacuum environment. The shear strengths of the joints were 80.89 MPa at 270°C for 10 minutes under 20 MPa, showing high reliability of the joints.