Temperature and strain rateeffect on mechanical properties of 63SN/37PB solder alloy

摘要

In the present investigation, tensile tests of 63Sn/37Pb solder commonly used in surface mount assemblies were carried out at strain rates from 10~(-5) s~(-1) to 10~(-1) s~(-1), over a wide temperatured range from-40 deg C, to study the effects of strain rates and testing temperatures on the mechanical properties in a systematic manner. It is found that the yield stress and ultimate tensile strength decrease with temperature and increase with strain rate. The Uoung's modulus decrases linearly with temperature at any given strain rate, and increases linearly with the logarithmic strain rate at any given temperature. A statistical method incorporating the multiple linear regression was employed to derive a set of empirical formulae to describe the effects of temperature and strain rate, quantitatively. The formulae were applied to explain the differences in the mechanical properties published by other researchers. It is found that the empirical formulae characterize well the mechanical properties of the solder at different temperatures and strain rates. A visco-elasto-plasticity constitutive model was applied to understand the relationship between Young's modulus and strain rate. It is concluded that the stress-strain relation is a function of strain rate except at extremely low stresses or high stain rates. Using the variation in the Young's modulus with stain rate and stress, a new method was proposed to determine the true Young's modulus of the material.