The mechanical properties degradation of solder joints under thermal cycling

The method of mounted strain gauges is used to measure the stress/strain hysteresis loops of solder joints in electronic packaging under thermal cycling. The results show that different solders have different loops; the shapes of the loops change and the shear modulus decreases along with the thermal cycling process, because the elements of the solder and matrix materials diffuse during the process and the voids in the solder joints increase, causing crystal lattice aberrances in the solder crystal; however, the creep index of the solder joints is not sensitive to the cycling process.