Intermetallic and tensile study of the newly developed Sn-2.0Ag-0.7Cu solder with addition of 0.5 wt.% zinc

Abstract

Sn-Pb solder is well known as an excellent solder in electronic packing. However, the Pb usage was eliminated in electronic assemblies due to its toxicity which can damage the kidneys, liver, and blood. Due to this problem, lead-free solders were proposed in order to replace lead-based solders. Sn-Ag-Cu solders were considered as a potential replacement. However, the SAC solders may increase the formation of intermetallic compound (IMC) and a small amount of Zn addition was found to retarded the growth of the intermetallic. In this study, 0.5 wt. % zinc was added into the Sn-2.0Ag-0.7Cu solder in order to improve the IMC and joint strength of the solder joint. The solder was prepared via powder metallurgy method which includes blending, compacting and sintering. The solder was manually soldered to copper substrate for 1 minute and 15 minutes at 250 °C temperature. The morphology of IMC was observed under Scanning Electron Microscopy (SEM) and ImageJ software was used to measure the thickness of IMC. There are two types of IMC which is Cu6Sn5 and Cu3Sn were formed. But, the Cu3Sn was not observed for 1 minute soldering for both Sn-2.0Ag-0.7Cu and Sn-2.0Ag-0.7Cu-0.5Zn solders. Based on the result, the total thickness of IMC in Sn-2.0Ag-0.7Cu-0.5Zn solder is thinner compared to the Sn-2.0Ag-0.7Cu solder. The melting temperature for both solders were measured by using Differential Scanning Calorimeter (DSC) and Sn-2.0Ag-0.7Cu-0.5Zn solder has lower melting temperature compared to plain solder. The joint strength of the Sn-2.0Ag-0.7Cu-0.5Zn was higher than Sn-2.0Ag-0.7Cu solder which indicates the additions of Zn increases the solder joint strength.