Mechanical characterization of SAC305 lead free solder at high temperatures

The mechanical properties and constitutive behaviors of lead free solders are highly dependent on temperature. Properties of high interest include the initial effective elastic modulus, yield stress, ultimate tensile strength, and secondary creep strain rate. Prior work on mechanical characterization of lead free Sn-Ag-Cu (SAC) solders has emphasized stress-strain and creep testing at temperatures from 25 to 125 °C. Characterization of solder material behavior at higher temperatures from 125 to 200 °C is needed to support several harsh environment electronics applications in the automotive, avionics, and oil exploration industries, as well as for military uses. In the current work, we have extended our previous studies to explore mechanical properties for SAC305 solder at temperatures from 125-200 °C (e.g. 125, 150, 175, and 200 °C). For each elevated temperature, stress-strain curves were measured at three strain rates (0.001, 0.0001, 0.00001 sec -1 ), and the mechanical properties were extracted. The stress-strain data measured at eight temperatures over the range 25-200 °C and at three strain rates were then compared to the predictions of the Anand constitutive model. Our results show that mechanical properties of SAC305 solder are reduced significantly at higher temperatures. For example, the yield stress and ultimate tensile strength of SAC305 typically drop by 60-80% from T = 25 °C to T = 200 °C. Correlations of the predictions of the Anand model with the experimental stress-strain data show that it can represent the experimental data accurately over a wide range of temperatures and strain rates.