Interfacial microstructure, shear strength and electrical conductivity of Sn-3•5Ag-o•5In/Cu lead free soldered joints

A Sn-Ag-In ternary alloy was considered as a substitute for eutectic Sn-Pb solder in the joining of electronic components. The microstructure in the diffusion zone of the assemblies was examined by scanning electron microscopy and the presence of CU6Sn5 intermetallics was confirmed by transmission electron microscopy. The width of brittle intermetallic phases present at the interface was found to control the strength of the solder joint. Sn-3.5Ag-0.5In/Cu joints exhibited better mechanical and electrical properties than Sn-37Pb/Cu joints.