Fabrication and Sintering Behavior of Nano Cu–Ag Composite Paste for High-Power Device

Cu and Ag nanoparticle (NP) paste has emerged as a promising choice for high-power devices because of its excellent thermal and electrical properties. However, easy oxidation, high sintering temperature of Cu NPs, high cost, and high porosity of Ag NPs restrict the practical application. Although Cu–Ag composite paste can improve bonding reliability, there have been no reports of fabricating stable and reliable Cu–Ag composite paste joints. In this work, we reported a novel method for fabricating a nano Cu–Ag composite paste with excellent dispersibility and relatively uniform particle size distribution via polyol one-step reduction. These composite NPs exhibit outstanding antioxidant capacity. The sintering behavior of the composite NPs at different temperatures was analyzed. The electrical and mechanical reliability of nano Cu–Ag composite paste joints with different ratios were investigated. With the increase in Ag content, the porosity and resistivity of the joint decrease, and the shear strength increases. The bonding joint presents a low porosity of 1.92% and a high shear strength of 32.6 MPa under a 1:3 ratio of Cu to Ag. The molecular dynamics (MDs) simulation results imply that Ag-rich composite system can achieve low-temperature sintering and maintain the stability of the sintering process.