Comparing and modifying estimation methods of fatigue life for PCBA under random vibration loading by finite element analysis

In this paper, a research on fatigue life estimation methods for printed circuit board assemblies (PCBA) under vibration loading is conducted. It mainly makes a comparison on fatigue life estimation results, for a FBGA mounted on the center of printed circuit board (PCB) with simply supported on all four sides and subjected to random vibration loading, between Steinberg´s model and three-band method. Because Steinberg´s model is a practical empirical model based on Steinberg´s testing and experience, and the reference of cycles to failure, N1, based on 3σ PCB displacement is an empirically determined value and uncertain for new products, using FEA to calibrate the parameter is meaningful for rapid fatigue life estimation. A finite element analysis (FEA) by ANSYS Workbench is performed to obtain the PCBA´s natural frequency and the 1-σ level von Mises stress of critical solder ball of the component. Using the results of FEA, the fatigue life or damage can be calculated by Steinberg´s two methods. And according to the damage equivalent principle, the Steinberg´s model (empirical formula) is modified to fit new PCBA´s fatigue life estimation and will be verified by test in the next work.