Thermomechanical Behavior of 96Sn-4Ag and Castin Alloy

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Abstract
The time- and temperature-dependent deformation behavior of two Sn-Ag base alloys, 96Sn-4Ag and Castin (96.2Sn-2.5Ag-0.8Cu-0.5Sb), used as solder interconnect materials was determined over strain rates ranging from 10−6 s−1 to 10−2 s−1 and temperatures ranging from −55°C–125°C. Uniaxial strain rate jump tests along with isothermal and thermomechanical cyclic tests were conducted. The constitutive behavior of each alloy was modeled with both a simple power law creep equation and the McDowell unified creep-plasticity model. Accumulated deformation under unconstrained thermal cycling was also measured to determine the relative dimensional stability due to internal constraints in the alloy itself. Overall, the Castin alloy appeared to be more stable and was more resistant to inelastic deformation.