Rattling and its effect on the reliability of portable electronic devices

In this paper, the rattling induced failure modes in product drop test have been investigated by using the nonlinear dynamic finite element analysis tool, ABAQUS/Explicit, and demonstrated through examples. For the selected product level assembly system, it is found that the side drop in both directions and the top-down drop are critical drop orientations when one of the critical assemblies is selected as a design object. The simulation results show that the higher stress field can be generated in the critical component of this assembly under the side drop and the top-down drop situations. After the further analysis of simulation results, it is shown that the rattling effect is the main reason to induce the higher stress field around this critical component as the history of contact force between this component and its contiguous part indicates that they hit each other three times during the period of time of the side impact, while the history of contact forces indicates that the front edge of this component severely hits another contiguous part once during the period of time of the top-down impact. The higher contact forces are produced in this assembly, or subsystem, under the side drop and the top-down drop situations. The limited space in this assembly, or subsystem, is the main cause that leads the subsystem to rattle. Through the redesign of this assembly structure in terms of the simulations, the rattling effect is successfully avoided. The stress level around critical component of this assembly is reduced by up to from 30% to 60% for the critical drop orientations. Such modeling results were correlated with physical drop test. It is shown that a validated modeling technique could be used to play a very important role in product reliability control and guarantee the product with high reliability to meet very competitive market