Combining vibration test with finite element analysis for the fatigue life estimation of PBGA components

Abstract

The study develops a methodology that combines the vibration failure test, finite element analysis (FEA), and theoretical formulation for the calculation of the electronic component’s fatigue life under vibration loading. A specially designed plastic ball grid array (PBGA) component with built-in daisy chain circuits is mounted on a printed wiring board (PWB) as the test vehicle for the vibration test. It is then excited by a sinusoidal vibration whose frequency equals the fundamental frequency of the test vehicle and tested until the component fails. Because the solder balls are too small for direct measurement of their stresses, FEA is used for obtaining the stresses instead. Thus, the real displacements in the vibration test are then inputted to the FEA model when performing the stress analysis. Consequently, the stress versus failure cycles ( S– N) curve is constructed by correlating both the obtained stresses on the solder balls and the number of failure cycles in the vibration test. Furthermore, the Miner’s rule is applied in calculating the fatigue damage index for those test components when failed. Finally, a formula for the prediction of the component failure cycle is deduced from all these procedures studied. It is also examined later by firstly predicting the fatigue failure cycle of a component and then conducting a vibration test for the same component for the verification purposes. The field test results have proven to be consistent with predicted results. It is then believed that the methodology is effective in predicting component’s life and may be applied further in improving the reliability of electronic systems.