Correlation between interfacial reactions and shear strengths of Sn-Ag-(Cu and Bi-In)/ENIG plated Cu solder joints

A comparative study was undertaken of the interfacial reactions of the Ni–P layer with four kinds of solder, Sn-37Pb, Sn-3.5Ag, Sn-3.5Ag-0.75Cu, and Sn-3Ag-6Bi-2In (wt.%), by performing isothermal aging at 150 °C for up to 2400 h. The formation and growth of the interfacial compound phases were investigated. The ball shear strength was also measured to investigate the effect of the microstructures and interfacial reactions on the reliabilities of these solder joints. The study results confirmed that the Sn-Ag based Pb-free solders are mechanically more reliable than the Sn-Pb solder.