Massive spalling of Cu-Zn and Cu-AI intermetallic compounds at the interface between solders and Cu substrate during liquid state reaction

摘要

The interfacial intermetallic compound (IMC) formation between Cu substrate and Sn-3.8Ag-0.7Cu-X (wt.%) solder alloys has been studied, where X consists of 0-5% Zn or 0-2% Al. The study has focused on the effect of solder volume as well as the Zn or Al concentration. With low solder volume, when the Zn and Al concentrations in the solder are also low, the initial Cu-Zn and Al-Cu IMC layers, which form at the solder/substrate interface, are not stable and spall off, displaced by a Cu_6Sn_5 IMC layer. As the total Zn or Al content in the system increases by increasing solder volume, stable CuZn or Al_2Cu IMCs form on the substrate and are not displaced. Increasing concentration of Zn has a similar effect of stabilizing the Cu-Zn IMC layer and also of forming a stable Cu_5Zn_8 layer, but increasing Al concentration alone does not prevent spalling of Al_2Cu. These results are explained using a combination of thermodynamic- and kinetics-based arguments.