Effects of active element Ti on interfacial microstructure and bonding strength of SiO2/SiO2 joints soldered using Sn3.5Ag4Ti(Ce,Ga) alloy filler

The active bonding between Sn3.5Ag4Ti(Ce, Ga) and silicon dioxide at low temperature has been investigated. The microstructure of the bonding interface, the distribution of Ti near the interface, and the formation of the interfacial reaction products have been explored. Experiment results show that there is obvious segregation of Ti at the SiO2/solder interface, and TiSi and TiO2 phases are formed at the interface. The mechanism of active bonding between Sn3.5Ag4Ti(Ce, Ga) and silicon dioxide has been analyzed based on the active adsorption and reaction thermodynamics theories. A soldering dynamic process model is established to better understand the soldering process. Both theoretical and experimental results suggest that the chemical adsorption of Ti on the silicon dioxide interface plays an important role in the initial bonding stage. The main bonding mechanism might be the reactant formation due to the interfacial reaction between Sn3.5Ag4Ti(Ce, Ga) solder and SiO2 substrate. The shear strength of SiO2/SiO2 joints is measured to be 11.15 MPa, 14.10 MPa, 16.37 MPa, and 17.91 MPa with soldering time of 1 min, 15 min, 30 min, and 60 min, respectively, which meets the requirements of SiOz or glass substrates bonding application.