Reliability enhancement of Sn-1.0Ag-0.5Cu nano-composite solders by adding multiple sizes of TiO₂nanoparticles

This paper demonstrates a novel low silver content TiO₂nanoparticle composite solder alloys, and discusses the TiO₂size effect on reliability of the solder and its solder joints with copper. 6 nm and 20 nm TiO₂nanoparticles were synthesized and added into Sn-1.0Ag-0.5Cu (SAC105) solder to prepare the nano-composite solders. The microstructure, coefficient of thermal expansion of the solders, and the shear strength, interfacial intermetallic compound growth of the solder joints under thermal cycling (1000 cycles) between −55 °C and 125 °C were investigated. The experimental results show that TiO₂nanoparticles can refine β-Sn grain size, decrease CTE of the solders, as well as suppress the interfacial intermetallic compound formation and growth. Also, after thermal cycling, the nano-composite solder joints have higher shear strength than the joints without TiO₂nanoparticles. Most importantly, smaller TiO₂nanoparticles (6 nm) shows larger influence on the respects of microstructure refinement, coefficient of thermal expansion reduction, interfacial IMC thickness decrease, and shear strength enhancement of the solder joints. The TiO₂nano-composite solder joints show higher electrical reliability than the original SAC105 solder joint according to the results of electric resistance change during thermal cycling.