High Strain Rate Mechanical Properties of SAC-Q Solder for Extreme Temperatures After Exposure to Isothermal Aging Up to 90 Days

Abstract

Electronic components are subject to high strain, during shock and vibration in many applications such as the automobile and aerospace. In many cases, this kind of electronic components will also be exposed to harsh temperatures of –65 °C to 200 °C. Electronic devices in harsh environments are often subject to strain rates of 1–100 per second. A large number of doped SAC solder alloys have emerged including SAC-Q, SAC-R, Innolot for electronic component interconnection. SAC-Q consists of inclusion of the Bi composition in Sn–Ag–Cu. For maximizing electronic package stability and high temperature storage and strain rates, the mechanical characteristic results and data for lead-free solder alloys are extremely significant. Thermal aging has been previously shown to cause modification of the mechanical properties at low strain rates. High strain-rate SAC-Q solder alloy data are not available for high temperature aging and testing at very low to high operating temperatures. For this analysis, the SAC-Q solder material was measured and analyzed at operating temperatures between –65 °C and 200 °C, at strain rates of up to 75 per second. Comparison with solder material SAC305, which has been tested under similar conditions, has also been made. When tensile experiments were carried out at various working temperatures, specimens for isothermal aging were preserved at 100 °C for up to 90 days after production and reflowing. The stress–strain curves are developed and described in this paper for a wide range of strain rates and test temperatures. Furthermore, the test results and data measured have been matched to the Anand viscoplasticity model and Anand constants have been determined by estimation of the high strain rate behavior measured in the broad range of working temperatures and stress levels.