The transient response of a PBGA256 assembly to random excitation is explored with quasi-static and transient finite element analysis, as well as with experiments. The quasi-static approximation is based on the first modal contribution to the measured PWB response. The dynamic prediction for solder strain and resulting damage accumulation rate are found to be significantly larger than in the quasi-static approximation. The quasi-static model is clearly missing additional stress drivers such as the dynamic movement of the component relative to the PWB and higher resonant modes of PWB flexure. The dynamic mode of the component is verified in this paper with two accelerometers placed on the component and on the PWB. Investigation of the higher modes of the PWB is deferred to a future study.

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