Printed wiring board (PWB) for mobile devices continues to have higher wiring density and more complicated structures from functionality requirements in addition to product size restriction. With enhancing the functionality, PWB failures occurred by drop impact is one of the most critical stresses to mobile devices. This paper illustrates the influences of the PWB in the detailed structures level “micro-scale structures” over drop reliability. The micro-scale structures studied include microvias, dielectric layers and copper layers. In order to characterize those influences, board-level drop tests and 2-dimensional mechanical simulation in micro-scale were conducted. It was clarified that the micro-scale structures had significant influences to drop reliability, and also the effectiveness of micro-scale approach was verified.
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