Stress-strain characteristics, dynamic recrystallization, grain growth, and melting point of the binary and ternary solder alloys

An advanced solder alloy, Pb-10wt%Sn-3wt%Zn, has been developed to improve the mechanical properties of the Pb-10wt%Sn based solders. Deformation behavior of Pb-10wt%Sn and Pb-10wt%Sn-3wt%Zn alloys was investigated in tension at strain rates from 0.005% to 0.25% s^−1 in the temperature range 383–433 K. The stress-strain characteristics curves showed two deformation modes: (i) continuous work softening and fracture following a sharp stress in Pb-10wt%Sn, (ii) work hardening with steady-state flow and fracture just after yielding in Pb-10wt%Sn-3wt%Zn. In the work softening type, relatively coarse grains ranging from 30 to 60 μm are produced by dynamic recrystallization (DRX). In the work hardening with steady-state flow type, fine grains less than 10μm are developed by alloying with zinc. Adding Zn into the solder makes the microstructure finer and more uniform. Microstructural characterization using optical microscope analysis (OMA) were conducted to investigate the deformation behavior and cleared that the grain boundary sliding is the dominant mechanism observed in the Pb-10wt%Sn-3wt%Zn. The melting points have been determined using differential thermal analysis (DTA) and differential scanning calorimetry (DSC). These temperatures are 587 and 555 K for Pb-10wt%Sn and Pb-10wt%Sn-3wt%Zn, respectively. The addition of a small amount of Zn leads to reduce high temperature performance and melting point.