Dynamic Mechanical Properties Of Lead Free Solders

Electronics packaging is key component of electronic products. Solder joints in the packaging, which play a role of mechanical connection and electrical continuity, will bear impact load and generate high strain rate deformation when the mobile and automotive electronic products drop inadvertently or work at high acceleration circumstance. Hence the dynamic mechanical behavior of lead-free solders under high strain rate is important issue for reliability design of electronic packages.In this paper quasi-static mechanical property and dynamic stress-strain behavior under high strain rate of 63Sn37Pb, 96.5Sn3.5Ag and 96.5Sn3.0Ag0.5Cu, were obtained by quasi-static tests and the split Hopkinson tension/pressure bar testing technique. The experimental results show that the three materials are sensitive to strain rate and their dynamic flow stresses are much greater than the static flow stresses, especially 96.5Sn3.5Ag. And it increased the intensity by adding element Cu which made 96.5Sn3.0Ag0.5Cu to have the highest yield stress and tensile strength. Furthermore, the higher the strain rate, the greater their tensile strength but less their fracture strain. This suggests that they tend to brittle fracture under high strain rate. And the temperature rise induced by transformation of plastic work to heat makes the material have obvious thermal softening.Based on experimental data, Johnson-Cook models for the two lead-free materials were derived, which was embedded in ABAQUS for numerical simulation. The good agreement of dynamic stress-strain curves between the numerical simulations and the experiments indicates that presented Johnson-Cook models are suitable to describe the dynamic behavior of the two materials. And the numerical results show that there is significant temperature rise in dynamic tension of the two materials and this has a softening effect on the stress-strain behavior.The research results provide necessary basic data for numerical simulation of solders under drop / impact loading.