Effective Acquisitions of Plastic, Creep, Viscoplastic Parameters of Solder Using the Stress Relaxation Method

In electronic equipment, the estimated lifetime of a solder joint is being intensively investigated. For the assessment of thermal fatigue reliability, the mechanical properties of solder joints with regard to inelastic characteristics at a range of temperatures must be known. However, measuring solder´s material properties is costly and time-consuming. Thus, a quick and simple technique should be established immediately. In this paper, a tensile test with a stress relaxation method is proposed in order to obtain parameters such as the creep constant and index, and also the viscoplastic parameters defined by L. Anand et al. We discuss acquiring solder parameters by the conventional method (tensile testing), and an effective method using stress relaxation, which reduces the number of necessary tests. Then, we compare our experimental results and FEM analysis results, and the effectiveness of the proposed technique is confirmed. We use a thermoelectric module as an example.