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Öğe Combination of thermal cycling and vibration loading effects on the fatigue life of solder joints in a power module(Sage Publications Ltd, 2019) Ghaderi, Davood; Pourmahdavi, Maryam; Samavatian, Vahid; Mir, Omid; Samavatian, MajidIn this work, the combination of vibration loading and thermal cycle effects on the fatigue properties of a solder joint in a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) discrete was investigated. The fatigue mechanism under each loading mode was individually analyzed, and then according to the incremental damage superposition approach, the simultaneous effects were thoroughly studied. Under thermal cycling, the creep behavior of the solder is linked to the fatigue life. In fact, the creep accumulated strain in each thermal cycle has a straight relation to the failure time of solder joint. The origin of stress/strain in the assembly is owing to the sharp difference between coefficients of thermal expansions of the components in the electronic package. Regarding the vibration loading, the root mean square of peeling stress as a widely acceptable failure indicator was used to evaluate the vibration effects on the fatigue life. It is determined that the maximum stress is concentrated at the corner of solder layer. This result was similar to the outcomes of thermal cycling. The results also indicated that the combination of thermal and mechanical loadings accelerates the failure of the solder joint of the power MOSFET. Furthermore, the experimental and simulation studies showed similar results and approved the crack initiation at the corner of solder layer.Öğe Influence of Directional Random Vibration on the Fatigue Life of Solder Joints in a Power Module(Ieee-Inst Electrical Electronics Engineers Inc, 2019) Samavatian, Vahid; Masoumian, Armin; Mafi, Mehdi; Lakzaei, Mostafa; Ghaderi, DavoodIn this paper, fatigue life of solder joints of the power module and the printed circuit board in a power inverter under directional random vibration using the finite element method (FEM) was evaluated. Five angles of 0 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees were selected for direction of vibration loading. The simulation results showed that the outermost corner of the solder layer undergoes the maximum stress during the vibration frequencies in all the situations. In general, with the increase of input frequency, the solder joints got more susceptible to the catastrophic failure. Moreover, it was found that in lower angles of loading direction, the peeling stress is dramatically increased in the solder layer. This event can be attributed to the considerable portion of shear stress in loading directions with lower angles. The experimental results also proved the FEM simulation and showed that the void growth and coalescence, resulted by fatigue, are intensified in the lower angles of vibration loading. Overall, this paper indicates that the reliability of a power module under a normal loading (90 degrees) is the highest among all other conditions.