Transient Dynamic Simulation and Full-Field Test Validation for A Slim-PCB Of Mobile Phone under Drop / Impact

Abstract

Product durability due to drop shock is a critical element for assessment of reliability for handheld devices. So far, no simulation model for a board-level drop has been extensively validated by experiments for its predictions of global (full-field) dynamic response. Accelerometers and strain gages which are traditionally utilized to measure the response at selected locations, fail to assess the global strain gradients and complex mode shapes. In this work, a novel non-contact optical technique has been proposed for measurement of full-field impact response. Pair of synchronized high-speed cameras capture the images of board assembly subjected to JEDEC standard impact, at rates up to 15,000 pictures per second. A digital image correlation (DIC) system has been integrated with the cameras to analyze the acquired images to give dynamic deformation, shape and strain over the entire surface of board during impact. A finite element model for the drop test has been developed using ANSYS/LS-DYNA. The numerical solution has been fully validated against experimental measurements of acceleration, strain and warpage at series of instants of time after impact. Effect of tightening torque at PCB mounts has been studied comprehensively with regards to the eigenvalues and mode shapes, and the necessity for accurate modeling of dynamic contact conditions existing at the supports has been demonstrated. Simulation model has been further used to assess the drop impact reliability of components on the board. Excellent correlation of all simulation results with the measured data validates the experimental and numerical propositions made in this work for analyzing a board-level drop impact.