Composition design of Sn-based active solder for soldering SiC ceramic using density functional theory calculation

Soldering SiC using Sn-based solder can lower residual interface stress due to low soldering temperature. Active elements can play key roles in interfacial bonding between Sn-based solder and SiC ceramics. In this study, density functional theory (DFT) calculation was performed to evaluate whether Ti, Al, Zr and Ag atoms can act as active elements to solder SiC. Work of adhesion (Wad), charge density difference and density of states were used to study the interfaces without and with active elements. β-Sn(001)/β-SiC(111) interface was built first and the C-terminated hollow site interface was found to have the largest Wad of 3.13 J/m2. It is found that with doping of Ti and Zr atoms, Wad values of interfaces increase to 5.70 and 5.35 J/m2, and thermodynamics stability of interfaces are also improved. In contrasting, Al and Ag atoms have the opposite effects. The electronic structure analysis shows that Ti and Zr can form strong ionic bonds with C atoms. Therefore, Sn–Ti and Sn–Zr alloys can be used as active solders to join SiC ceramic at low temperature.