Surface mount capacitors have leads which are soldered to the circuit boards. When the circuit boards are subjected to random vibration, capacitors in turn are subject to random vibration and leads may fail in fatigue. Experiment is performed toobtain fatigue life of capacitors. Two different experimental set ups are used. First using laser vibrometer, natural frequencies are obtained. Next, the capacitors are excited under random vibration by a shaker driven by an analyzer. Using extender board and data acquisition card connected to a computer, fatigue life of various capacitors are obtained. In order to perform theoretical analysis, owing to the complex lead geometry, modeling and meshing are done in Pro/Engineer. Then finite element analysisis done to estimate stress concentration. Taking into account of the stress concentration factor, stress in the leads due to given input power spectral density are calculated using single degree of freedom model because there is only one natural frequency in the frequency range of interest. Then assuming Rayleigh distribution of stress, fatigue life of the capacitors are estimated. Finally theoretical and experimental results are compared.
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