Thinner printed wiring assemblies (PWA) and smaller clearances are driven by the continuing increase of functionality and miniaturization in portable electronic devices. The probability of secondary impact during accidental drop and impact between a circuit card and adjacent components increases with the decrease in the size and weight of the product. In particular, compared to the initial impact, impulses caused by contact during secondary impacts are typically characterized by significant increase of amplitudes and extremely short pulse widths. As a result, stress wave transmission and reflection in printed wiring boards (PWBs) can be at a frequency range close to the resonant frequencies of PWA components with miniature internal structures, such as MEMS. This study focuses on analyzing the high frequency content of the accelerations due to stress wave propagation, reflections and dispersions in the thickness direction of multilayered PWBs, caused by secondary impact, and on the consequential effects on typical failure modes with high resonant frequencies.

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