Fatigue life assessment of electronic components under vibration using displacement as a response metric

Abstract

Classical vibration fatigue methods uses stress as the response metric of interest, which requires Stress vs. Number of cycles (S-N) curve as input material property. This paper describes estimation of vibration fatigue life using displacement as response for an axial through hole component mounted on Printed Circuit Board (PCB) of an automotive electronic product. Similar to S-N curve, this methodology requires a Relative Displacement vs. Number of cycles curve (RD-N curve) for fatigue life estimation, which is created from a series of tests using a Laser Vibrometer (non-contact method). Finite Element Analysis (FEA) has been performed for product assembly using damping values from test under random vibration input base excitation. Fatigue life estimations are performed in frequency domain. Predicted fatigue life under random vibration using Steinberg's three band approach and using Power Spectral Density (PSD) for both stress and displacement response are compared with experimental test results of leaded component. Response ranges for displacement and stress of respective PSD are evaluated using Dirlik's empirical formula for rainflow ranges.