Low-Temperature High Strain Rate Constitutive Behavior of Doped and Undoped SnAgCu Solder Alloys after Prolonged Storage at High Temperature

Abstract

Exposure to extreme-low environmental temperatures in conjunction with high strain-rates may be encountered by electronics in several harsh-environment applications. Examples include down-hole drilling, aerospace, automotive electronics - which may endure high or low operating temperatures during operation. The automotive operating temperature range is -40°C to + 125°C. The equipment operating range for defense equipment is -55°C to + 125°C. In addition, electronic systems may experience prolonged periods of non-climate-controlled exposure to high and low temperature prior to deployment in the intended application. Materials properties of interconnects at extreme-low temperatures and high strain-rates are not well-studied and there is a scarcity of published data on undoped and doped solder alloys. The current paper fills this void in the state of art through measurements of properties of doped SAC alloys at low temperatures in the range of -65°C to high temperatures up to 200°C, at high strain rates after various durations of thermal aging. Alloys studied include SAC305, SAC-Q, and M758. In each case, the stress-strain curves have been measured at low operating temperatures using impact-hammer based tensile tests with cooling chamber. Anand Viscoplasticity model constants have been computed to model the material behavior over the whole range of temperatures and strain rates in the range of 1-100 per sec. In addition, the evolution of the model constants with the duration of thermal storage at high temperature has been quantified. The computed anand parameters has been used to simulate the drop events for a ball-grid array package on printed circuit board assembly to determine hysteresis loop and plastic work density.