High temperature ratcheting behavior of nano-silver paste sintered lap shear joint under cyclic shear force

Low temperature sintered nano-silver paste can be used for connected chips that require high temperature operation and high heat dissipate ability because of its higher melting temperature, and better thermal/electrical conductivity than conventional solders and adhesive films. In this study, high temperature ratcheting behavior of the nano-silver paste sintered lap shear joint was examined by cyclic shear force at room temperature and elevated temperatures at 225 °C, 275 °C and 325 °C. The effects of shear stress amplitude, mean shear stress, peak stress dwell time and temperature on the ratcheting response of sintered lap shear joint were analyzed. Results show that (1) the ratcheting strain and ratcheting strain rate of the nano-silver sintered lap shear joint increase with increasing shear stress amplitude or mean shear stress; (2) the ratcheting strain increases with the increasing temperature or the peak stress dwell time; (3) the ratcheting strain shakes down after it accumulates to a certain extent at room temperature; (4) even though 225 °C is a destructive temperature for solder and adhesive films, the ratcheting evolution of nano-silver sintered joint is very mild no matter whether the sample dwells at peak stress or not; (5) the influence of shear stress amplitude, mean shear stress or peak stress dwell time is more and more obvious at high temperatures.