Effect of Prolonged Storage up to 1-Year on the High Strain Rate Properties of SAC Leadfree Alloys at Operating Temperatures up to 200 °C

Abstract

Transient dynamic loads in addition to prolonged periods of high temperature exposure are a part of number of high profile applications with high reliability needs. Examples include - electronics in automotive applications may be mounted under the hood or in the trunk of the car resulting in prolonged periods of high temperature exposure followed by operation under vibration while at environmental temperature extremes, and electronics in downhole drilling applications may be mounted close to the drill tip resulting in exposure to transient dynamic loads. High strain rates encountered subsequent to prolonged periods of non-operational high temperature storage encountered in downhole drilling, and automotive underhood applications require the development of computational tools and techniques for prediction of material deformation behavior and reliability. In this study, mechanical properties of lead free SAC105 and SAC305 has been measured for strain rates 1-100 per sec at elevated temperature 200°C after prolonged storage for periods up to 1-year. Stress-Strain curves have been plotted over a wide range of strain rates and temperatures for pristine specimen which have been fabricated using reflow profiles representative of solder-joint production assemblies. The fabricated SAC105 and SAC305 leadfree alloys specimen have been tested at strain rates of 10, 35, 50 and 75 per sec at various operating temperatures of 50°C, 75°C, 100°C, 125°C, 150°C, 175°C, and 200°C. Experimental data for the aged specimen has been fit to the ANAND's viscoplastic model.