The microstructure and fracture behavior of Sn-3Ag-0.5Cu solder joints

Ball impact test and ball shear test have been used to investigate the joint strength. The joint strength of lead and lead-free solder joints under high strain rate condition were examined. Microstructure in the as-reflowed condition and fracture surfaces were investigated. The intermetallic compounds of Sn-3Ag-0.5Cu joints demonstrated as layer-type (Cu, Ni)₆Sn₅. Fractographies show that all of Sn37Pb solder joints exhibit the ductile fracture mode in both tests. On the other hand, Sn-3Ag-0.5Cu solder joints exhibit the interfacial fracture mode. The characteristic curve in both tests could demonstrate the failure feature. The ductile fracture behavior exhibits a long displacement and high fracture energy in both tests. The interfacial fracture behavior exhibits a short range displacement and low fracture energy during the test.