High strain rate mechanical behavior of SAC-Q solder

Electronics components in automotive, oil-exploration industries, military applications may be exposed to high temperature and high strain rates when subjected to shock and vibration. In harsh environment applications, electronic products may experience strain rates of 1-100 per sec and environmental temperatures up to 200°C. There is need of material data for leadfree solder alloys at high strain-rates and temperatures. In response to the need more reliable lead free solder alloys which can survive in extreme harsh environments and prolonged periods of aging - several doped SAC solder alloys (SAC-Q (CYCLOMAX), and innolot) have been introduced. SAC-Q are formulated with Sn-Ag-Cu with addition of Bi (SAC+Bi). Prior research has shown that addition of dopants (Bi, Ni, In, Mg, Mn, La, Ti) to SAC solder alloys can improve wettability, melting temperature, shock and drop reliability and microstructure [Cai 2010, Matahir 2011 and Pandher 2007]. Previously, mechanical properties for doped SAC alloys (SAC-R, SAC-Q and innolot) have been reported at low strain rate and high temperature [Ahmed 2015 and Chowdhury 2016] but there are no material properties available in published literature at high strain rate at very high operating temperature (25°C200°C) for SAC-Q lead-free solder alloy. In this study, mechanical properties for doped SAC lead-free solder alloys (SAC-Q) have been measured at strain rates of 10, 35, 50 and 75 per sec at operating temperatures up to 200°C using uniaxial tensile testing. Stressstrain curves have been plotted over a wide range of strain rates and temperatures. In addition, nine-anand parameters for SAC-Q have been computed from stress-strain curves. SACQ's solder alloys have been compared to traditional SAC solder alloys (SAC105). High-speed imaging and DIC have been used to measure the full-field strain in the specimen at frame-rates up to 75,000 fps. Experimental data for the pristine specimen has been fit to the anand viscoplastic model.