Influence of nano-TiO2 reinforcements on the wettability and interfacial reactions of novel lead-free Sn3.5AgO.5Zn composite solder/Cu solder joints

The influences of intermixing nano-TiO₂ particles on the wettability and interfacial reaction of novel lead-free Sn3.5Ag0.5Zn composite solder with Cu substrate were investigated. The wettability of the Sn3.5Ag0.5Zn composite solder alloy was measured by the sessile-drop method under a 10^-3 Torr vacuum at different temperature up to 30 mins. Scanning electron microscopy (SEM) was used to quantify the interfacial microstructure for each processing condition. The continuous scallop-type Cu₆Sn₅ IMC layer was still the only original product at the SAZ solder/Cu and SAZ composite solder/Cu interface at temperature 300 °C. However, a new flat-type QisZrig IMC layer was formed at the Cu₆Sn₅/Cu interface at temperature 325 °C. The addition of nano-TiO₂ particles to the SAZ solder effectively improved in wetting property and corresponding suppressed the growth of the IMC layer at the interface.