Publications Details

Constitutive behavior of 40Sn-40In-20Pb and 50In-50Pb solders

Frear, D.R.

This work was performed to characterize the time dependent deformation behavior of two solder alloys typically used in radar applications, 40Sn-40In-20Pb and 50In-50Pb by weight percent. The near-eutectic 60Sn-40Pb alloy was sued as a baseline comparison. The time-dependent deformation was measured using isothermal uniaxial compression creep tests. The data was reduced and, using a least squares fit algorithm, formatted into the Sherby-Dorn power law creep equation. The derived constitutive relationships were then used as a primary input to a solid mechanics, finite element model to predict solder joint lifetime and reliability. For a fixed applied stress, 40Sn-40In-20Pb had slower creep rates, at all temperatures, compared to 50In-50Pb and the baseline near eutectic 60Sn-40Pb solder. At temperatures above 70 C, the 50In-50Pb had faster creep rates than 60 Sn-40Pb. At lower temperatures, the 60Sn-40Pb solder had a higher creep rate due, in part, to its heterogeneous structure and large number of grain boundaries available for grain boundary sliding and rotation compared to 50In-50Pb.