Effect of Creep and Fatigue on Individual SAC305 Solder Joint Reliability in Iso-Thermal Cycling
Authors: Mohammed Abueed, Raed Alathamneh, Sa'd Hamasha, Ph.D., Jeff Suhling, Ph.D., Pradeep Lall, Ph.D. Company: Auburn University Center for Advanced Vehicle and Extreme Environment Electronics (CAVE3) Date Published: 9/22/2019
Abstract: The fatigue behavior of lead-free solder joints in thermal cycling is complicated and not well-understood yet. The effect of thermal cycling conditions on life is influenced by several factors with different levels of contribution. Recent research results showed that the damage mechanism of solder joints in thermal cycling includes a combination of fatigue and creep. Damage due to creep is dominant during the dwell at high temperatures while damage due to fatigue is dominant during the cycling ramps. Therefore, it is vital to investigate the effect of the creep and dwell time on the fatigue of solder joints. Accelerated shear fatigue test on individual solder joints is used to simulate the effect of dwell time and stress amplitude on the fatigue performance. Individual SAC305 solder joints with OSP surface finish were cycled in stress control experiments where the strain at the maximum stress is held for a period of time. The stress amplitudes include 16, 20, and 24 MPa, and the dwell times include 0, 10, 60, and 180 seconds. Instron 5948 Microtester machine is used to execute the test on the individual solder joints using a customized fixture. The evolutions in the hysteresis (stress-strain) loop are demonstrated at different experimental conditions. The damage due to creep was distinguished from fatigue through quantifying the inelastic work per cycle and plastic strain range for each test condition.
The fatigue life of solder joints is decreased when increasing the dwell time. The value of life reduction due to increasing the dwell time is reduced until a point where extra dwell time does not affect. Increasing the stress amplitude leads to decrease the fatigue life significantly. The dwell time at higher stress leads to more damage and thus lower fatigue life. The inelastic work per cycle range is increased when increasing both the stress amplitude and dwell time. The creep damage was dominant when the dwell time is high and stress amplitude is low.