Effects of adding some elements on solderability of Sn-0.7Ag-0.5Cu solder

Some alloy elements were added to Sn-0.7Ag-0.5Cu solder, to fabricate two new solders, Sn-0.7Ag-0.5Cu-0.05Ni-XBi(X=0, 2.0, 2.5, 3.0, 3.5, 4.0 wt%) and Sn-0.7Ag-0.5Cu-XIn(X=0, 0.2, 0.5, 0.8, 1.0, 1.2, 1.5, 1.8 and 2.0 wt %). The solderability tests of the two solder alloys have been conducted to study effect of bismuth, nickel and indium content on melting temperature and wettability of solder alloys. Melting point test was carried out with DSC (Differential Scanning Calorimetry) instrument. Wetting area is referred as the index to evaluate the wettability. The results of melting point experiment showed that the peak melting point of Sn-0.7Ag-0.5Cu solder was 220.05°C. The peak melting point of Sn-0.7Ag-0.5Cu-0.05Ni-3.5Bi solder was 215.74°C. And the peak melting point of Sn-0.7Ag-0.5Cu-1.5In solder was 215.27°C. The melting points of two new solders were lower than the recommendatory that of Sn-Ag-Cu solders. The results of wettability experiment of Sn-0.7Ag-0.5Cu-0.05Ni-XBi showed that with the increasing amount of Bi addition, wetting area of alloy solder increased from 54.93 mm² to 63.27 mm². The Sn-0.7Ag-0.5Cu-0.05Ni-3.5Bi solder showed best wettability in accordance with wetting area. It also showed that with the increasing amount of indium addition in Sn-0.7Ag-0.5Cu-XIn, wetting area increased from 64.26 mm² to 77.96 mm². The Sn-0.7Ag-0.5Cu-1.8In solder showed best wettability in accordance with wetting area.