Effects of reinforcements on the structure and properties of tin based lead free alloys

Abstract

The role of reinforcements with Al2O3 and Ni on the bulk properties of Sn-Ag-Cu solder has been investigated in this research. Sn-3Ag-0.5Cu-xAl2O3 and Sn-3Ag- 0.5Cu-xNi solder composites with x = 0.0, 0.5, 1.0, 2.0 and 3.0 were synthesized by the conventional solid-state powder metallurgy method. The mixtures were blended manually for at least 30 minutes at room temperature to create a uniform distribution and then sintered at a temperature of 175°C for holding times in the range of 1-2 hours. Compositional, thermal, microstructural and mechanical properties of these composite solders were analyzed and compared accordingly. Differential thermal analysis (DTA) revealed that the melting temperature of base Sn-3Ag-0.5Cu alloy was 226.4°C. The melting temperature increased up to 228.8°C with the addition of Al2O3 content into the base alloy and for Ni addition it increased up to 229.8°C. From microstructural observation it is found that the reinforcing particles were more or less uniformly distributed. With longer sintering time the amounts of voids within the matrix were found to be lesser in the bulk Sn-Ag-Cu alloy. Nano Al2O3 particles could not be identified from XRD study because of its presence in segregation form into the sample and on the other hand micron sized Ni was found as Ni2O2(OH) in the XRD patterns. Hardness increased with the increase in Al2O3 content in Sn-3Ag- 0.5Cu alloy up to a certain amount (i.e. 1 wt.%) then decreased again. However with the increase of Ni content hardness increased for Sn-3Ag-0.5Cu-xNi alloys.