High-temperature creep and hardness of eutectic 80Au/20Sn solder

Eutectic 80Au/20Sn solder is widely used for device packaging in optoelectronic and high power electronic industries. The knowledge of thermomechanical properties of the solder is critical for design and application. In this piece of work, Berkovich depth-sensing indentation test has been used to study the effect of temperature on the hardness and the creep behavior of the 80Au/20Sn solder alloy at temperatures ranging from 25 °C to 200 °C. The results showed that the hardness of eutectic 80Au/20Sn solder decreased as temperature increased. The change of hardness with temperature in the range from 25 °C to 150 °C could be considered as linear and a temperature coefficient of hardness of −1.1 × 10−2 GPa/°C could be estimated; thereafter the change of hardness tapers off as the temperature increases to 200 °C. On the other hand, the creep penetration and creep strain rate increased and its associated stress exponent decreased with temperature, which resulted in large plastic deformation during indentation.