Effect of Prolonged Storage on High strain rate Mechanical properties of QSAC10 and QSAC20 Solders after Exposure to Isothermal Aging of 50°C

In Aerospace, military, automotive, space and oil exploration industries, various electronic parts may be subjected to sustained operation at high and low surrounding temperatures as well as high strain-rate loads. These parts may also be stored in non-climate-controlled enclosures prior to deployment. Previous research studies have shown that material properties of undoped SAC alloys evolve even at moderate temperatures after a prolonged period of storage. A variety of dopants has been introduced into SAC alloy formulations in order to reduce the aging effects. In this study, two doped SAC solder called QSAC10 and QSAC20 has been subjected to high strain rate testing after keeping them in storage at temperature of 50°C for duration of 30 days. Samples with no aging and 30 days aged samples have been subjected to uniaxial tensile tests to measure the mechanical properties of SAC+Bi solders. The High and Low operating temperature used in this experiment ranged from -65°C to 200°C. Then the experimental material data has been used to compute the constants for the Anand Visco-Plasticity model and then the model predictions of the uniaxial tensile test has been compared with the experimental data. The material constitutive behavior has been implemented in a finite element framework to simulate the drop events using the Anand constitutive model. The plastic work per shock event has also been determined which is a measure of the damage progression in the solder interconnects. Lastly, the constitutive model has been used to simulate the shock event of a ball-grid array package on printed circuit board assembly