Influence of TiO₂ nanoparticles on IMC growth in Sn–3.0Ag–0.5Cu–xTiO₂ solder joints during isothermal aging process

The influence of TiO₂ nanoparticles on the growth of intermetallic compound (IMC) between Sn–3.0 wt% Ag–0.5 wt% Cu–x wt% TiO₂ (x = 0, 0.02, 0.05, 0.1, 0.3, and 0.6) composite solder and the Cu substrate during isothermal aging process at temperatures of 120, 150, and 190 °C has been investigated in this study. Scanning electron microscopy was used to observe the microstructural evolution of the solder joints and measure the thickness of IMC layer. The IMC phases were identified by energy-dispersive X-ray spectroscopy and X-ray diffractometry. Results show that two intermetallic layers, Cu₆Sn₅ and Cu₃Sn phase are formed at the interface and the morphology of the Cu₆Sn₅ phase transforms from scallop-type to layer-type in Sn–3.0Ag–0.5Cu–xTiO₂ solder joints. The addition of nano-TiO₂ has a strong influence on the growth of overall IMC layers, and the thickness of overall IMC layers rapidly increase with aging temperature and time. The growth rates and activation energies of the IMC growth of six solder alloys were determined. Results reveal that, for three different ageing temperatures, the growth rates of overall IMC layers decrease with an increase in nano-TiO₂ proportion. The activation energies for the growth of overall IMC layers range from 48.34 to 63.61 kJ/mol. Adding nano-TiO₂ to Sn–3.0Ag–0.5Cu solder could evidently increase the activation energy of overall IMC layers, reduce the atomic interdiffusion rate, and thus inhibit excessive growth of overall IMC layers.