High strain rate constitutive behavior of SAC105 and SAC305 leadfree solder during operation at high temperature

•In this paper, Uniaxial tensile tests for SAC105 and SAC305 lead-free solders were carried out at 4 high strain rates (ε̇ = 10, 35, 50, 75 per sec) and 5 temperatures (T = 25, 50, 75, 100, 125 °C). High speed data acquiring system has been employed to capture the stress-strain curves.•The accuracy of the extracted Anand constants has been evaluated by comparing the model prediction with experimental data. The model predictions show good correlation with experimental data.•The Anand Viscoplastic model has been used to predict the deformation and strain history of the printed circuit board and the solder joints under a 1500 g, 0.5 ms mechanical shock.•The model predictions of board deformation and board strain have been predictions have been correlated with the measurements of board strain and board deformation from high-speed imaging in conjunction with digital image correlation.•Results indicate that is unreasonable to use linear elastic material properties to simulate the transient dynamic deformation and strain of solder joints under mechanical shock. There is a significant difference in the predicted solder joint strain values between the linear elastic model and the viscoplastic model predictions.

Industry migration to leadfree solders has resulted in a proliferation of a wide variety of solder alloy compositions. The most popular amongst these are the Sn–Ag–Cu family of alloys like SAC105 and SAC305. Electronics subjected to shock and vibration may experience strain rates of 1–100/s. Electronic product may often be exposed to high temperature during storage, operation and handling in addition to high strain rate transient dynamic loads during drop-impact, shock and vibration. Properties of leadfree solder alloys at high strain rates at low and high temperatures experienced by the solder joint during typical mechanical shock events are scarce. Previous studies have showed the effect of high strain rates and thermal aging on the mechanical properties of leadfree alloys including elastic modulus and the ultimate tensile strength. The ANAND viscoplastic constitutive model has been widely used to describe the inelastic deformation behavior of solders in electronic components. In this study, SAC105 and SAC305 leadfree alloys have been tested at strain rates of 10, 35, 50 and 75/s at various operating temperatures of 50 °C, 75 °C, 100 °C and 125 °C. Full-field strain in the specimen have been measured using high speed imaging at frame rates up to 75,000 fps in combination with digital image correlation. The cross-head velocity has been measured prior-to, during, and after deformation to ensure the constancy of cross-head velocity. Stress–strain curves have been plotted over a wide range of strain rates and temperatures. Experimental data for the pristine specimen has been fit to the ANAND's viscoplastic model.