Hardness profiles of Sn-3.0Ag-0.5Cu-TiO2 composite solder by nanoindentation

Improvement of the hardness values of Sn-3.0Ag-0.5Cu-TiO2 composite solders with different TiO2 weight percentages was evaluated by nanoindentation. The composite solders were prepared by ball milling of Sn-3.0Ag-0.5Cu solder with TiO2 nanoparticles at 300 rpm for 10 min prior to printing and reflowing. Structural analysis indicated that the TiO2 nanoparticles were successfully blended into the Sn-3.0Ag-0.5Cu solder. Finer Cu6Sn5 and Ag3Sn phases were observed in the composite solder micrographs. The optimum hardness of 1.775 GPa was obtained for the composite solders with a TiO2 content of 1 wt%. A further increment of the TiO2 content to 1.5 wt% significantly reduced the hardness value to 1.677 GPa. The hardness profiles were established based on the specific measurement pattern obtained from the nanoindentation. The mechanism of the influence of TiO2 nanoparticles on the refinement of the intermetallic phases and improvement of the hardness value is also presented.