Investigation of the Thermal Loading and Random Vibration Influences on Fatigue Life of the Solder Joints for a Metal-Oxide-Semiconductor-Field-Effect Transistor in a DC-DC Power Boost Converter

This study presents the effects of the vibration and thermal cycling on the fatigue life of a power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) in a power converter circuit. The fatigue mechanism in per loading mode was investigated separately and based on the overlap approach, the synchronous effects were analyzed. The solder creeps' attitudes are depended on the fatigue life for the thermal loops. The success of the deposited strain per thermal loop is in direct relation with the fatigue lifetime. The main source of the stress in the packaging process is the differences between the components' thermal coefficients. To evaluate the effects of the vibration on the fatigue life for the solder layers, the RMS value of the peeling stress was considered. According to the results, the maximum stress and main affected points realized at the corners of the layers. It has been identified that the assembling of the thermal effects and mechanical loads are quickened the failure rate at the solder joints for this device. The Finite Element Method (FEM) is used for the simulation and the results confirm the estimated crack formation places in the layers.