Effect of 0.5 wt% nano-TiO_2 addition into low-Ag Sn0.3Ag0.7Cu solder on the intermetallic growth with Cu substrate during isothermal aging

摘要

The interfacial evolution of nano-TiO_2 reinforced low-Ag Sn0.3Ag0.7Cu composite solder on Cu substrate was investigated during 100 and 175 ℃ isothermal aging for up to 7 days. The thickness of interfacial intermetallic compound (IMC) layers was quantitatively evaluated from SEM micrographs using imaging software. It was found that the mean thickness of interfacial Cu-Sn IMC layers increased linearly with the square root of the aging time. This relationship indicates that the growth of the IMC layer is a diffusion-controlled process. Kinetics analysis shows that the apparent activation energies for the growth of Cu-Sn IMC layers were 40.25 kJ/mol for low-Ag Sn0.3Ag0.7Cu solder and 50.85 kJ/mol for low-Ag Sn0.3Ag0.7Cu composite solder. The reduced diffusion coefficient was proved for the low-Ag Sn0.3Ag0.7Cu composite solder/Cu joints.