Effect of alloying elements on the creep behavior of high Pb-based solders

Abstract

This study examines the high temperature creep behavior of several Pb-based alloys. All compositions tested were found to follow power-law dislocation creep in the strain rate range of 10−9–10−3s−1. Both the stress exponent and activation energy were measured from 298 to 473K to identify the rate controlling mechanism for creep deformation. Creep of 95Pb–5In, 92.5Pb–5Sn–2.5Ag, 93Pb–3Sn–2Ag–2In was rate limited by dislocation climb from the observed stress exponent. A transition in the controlling climb mechanism from pipe diffusion to lattice diffusion was observed around 0.7Tm. Creep of 90Pb–10Sn was, however, rate limited by viscous solute drag rather than dislocation climb due to the greater concentration of Sn in Pb. The enhancement in self-diffusion of Pb was dependent on the degree of solid solution with solute atoms. The outcome of this work identifies variables related to the alloy elements that control creep behavior of Pb-based alloys used in high temperature applications where traditional solders cannot be used.