Reliability enhancement of Sn-1.0Ag-0.5Cu nano-composite solders by adding multiple sizes of TiO2 nanoparticles

This paper demonstrates a novel low silver content TiO2 nanoparticle composite solder alloys, and discusses the TiO2 size effect on reliability of the solder and its solder joints with copper. 6 nm and 20 nm TiO2 nanoparticles 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 degrees C and 125 degrees C were investigated. The experimental results show that TiO2 nanoparticles can refine beta-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 TiO2 nanoparticles. Most importantly, smaller TiO2 nanoparticles (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 TiO2 nano-composite solder joints show higher electrical reliability than the original SAC105 solder joint according to the results of electric resistance change during thermal cycling. (C) 2016 Elsevier B.V. All rights reserved.