Solid-liquid interdiffusion bonding of copper using Ag-Sn layered films

Abstract

Newly developed bonded materials and fabrication processes are expected to firmly bond copper leads to SiC chips for application in next generation power modules. Solid-liquid interdiffusion bonding of copper was performed using Ag-Sn layered films. Microstructural development and mechanical properties of bond layers were investigated. The bond layer grew at the thin film interfaces because of the solidliquid interdiffusion. Cu 6 Sn 5 and Ag 4 Sn or Ag 3 Sn phases were formed at the initial bonding stage, and subsequently, Cu 3 Sn formed between the Cu 6 Sn 5 and Cu as both bond time and temperature increased. Finally, the bond layer was primarily composed of Ag4Sn and Cu 3 Sn. The hardness and Young's modulus of Ag4Sn were much lower than those of Cu 3 Sn. The growth of the Cu 3 Sn layer that formed between Ag 4 Sn and Cu could be limited by optimizing the design of the faying surface.