Mechanical Constitutive Properties of Two High-Temperature Lead-Rich Solders

This study focuses on the mechanical properties of two kinds of solders for high temperature interconnections (melting temperature above 280 °C after reflow). They are both lead-rich solders in wire form: 93.5Pb/5Sn/1.5Ag and 92.5Pb/5Sn/2.5Ag. The mechanical constitutive tests conducted in this study include: (i) monotonic elastic-plastic stress-strain response at constant strain rates and constant temperatures; and (ii) isothermal, viscoplastic creep strain response at several constant stress levels and different temperatures. The sensitivities of the material viscoplastic constitutive response to temperature, loading rate and stress level were systematically studied, so that the mechanical performance of these two solders could be compared with those of other solders, at similar test conditions. Both the Pb-rich solders studied had statistically similar behavior at the tested stress levels and temperatures in creep tests. The Ramberg-Osgood model and the Garofalo model were used to represent the elastic-plastic and creep behavior, respectively, of each solder and the corresponding model constants are presented in the paper.