Improved understanding of the enhancement of sintering of mixtures of Cu microparticles and sn nanoparticles for electronic packaging

Because of their excellent conductivity and low sintering temperature, Cu particles have attracted much attention as interconnect materials in electronic manufacturing. Compared with Cu nanoparticles, Cu microparticles have better oxidation resistance and lower cost, but their poor sintering properties prohibit their use. In this paper, we attempt to improve the sintering property of Cu microparticles by mixing them with Sn nanoparticles. Microscopic images show that Sn can form a dispersed Cu₃Sn intermetallic compound (IMC) on the surface of Cu microparticles during sintering, and thereby improve the metallurgical bonding between Cu microparticles. However, with further addition of Sn, a brittle Cu₆Sn₅ IMC forms throughout the joint, leading to a reduction of shear strength. At an optimal Sn content of 25 wt%, the shear strength of the particle mixture sintered at 260 °C can be significantly improved from 33 to 70 MPa. These results offer an experimental basis for improving the sintering of Cu microparticles by the second phase strengthening provided by Cu–Sn IMCs.