Effect of Aging on the Fatigue Life and Shear Strength of SAC305 Solder Joints in Actual Setting Conditions

Solder alloy materials are utilized to form mechanical and electrical connections between printed circuit boards and the electronic components. Enhancing the reliability of the electronic components is mainly dependent on the reliability of the interconnected solder joints. Therefore, estimating the reliability and fatigue behavior of the solder joints under realistic operating conditions is crucial. Aging is one of the major factors that may reduce the fatigue and mechanical properties of solder joints. The objective of this study is to assess the fatigue life and the shear strength of SAC305 solder joints under several levels of cycling stress amplitudes and different aging conditions at actual setting conditions. Instron Micromechanical Tester is used to perform accelerated shear fatigue tests on individual SAC305 solder joints. The fatigue lives of SAC305 solder joints are examined at cycling loads of 16 MPa, 20 MPa, and 24 MPa, aging times of 0, 10 hrs and 100 hrs and aging temperatures of 100°C and 150°C. The total number of combinations tested is eighteen where each has seven solder joint samples. Two-parameter Weibull distribution was constructed for each combination to assess the reliability. The hysteresis loop for each cycle was developed, and the plastic strain and the inelastic work per cycle were measured. The effects of different aging conditions on the inelastic work per cycle and the plastic strain at different stress amplitudes are demonstrated. A power equation is used to express the correlation between the fatigue life and stress amplitude and the results indicated a significant reduction in the fatigue life when the stress amplitude is increased. The results also showed that increasing the aging time and the aging temperature leads to a reduction in the fatigue life. Finally, reliability prediction models as a function of time (cycles) and stress amplitude at different aging conditions are constructed. The effect of aging on the shear strength is investigated as well.