Formation of mechanical strains in the component board of a high-end handheld product during shock impact

Abstract

The effect of mechanical shock impacts on electronic component boards is a key factor in the reliability of modern handheld products. Due to differences in product enclosures, impact orientations, strike surfaces and mountings of component boards, the loading conditions induced by a drop of a complete product differ from those encountered in standardized board level tests. In order to better understand the correlation between the board level drop tests and an actual drop of a complete device, the component board of a high-end handheld product has been studied under both board level and product level test conditions. The mechanical vibration response of the component board with and without the product enclosure has been characterized with acoustic excitation. The results have been compared with measurements from 4-point supported board level and unsupported product-level drop tests. The comparison shows that the method of component board mounting has a profound effect on the rate and locations of the highest strains on the board. The product enclosure was found to influence the mechanical response due to increased mechanical damping. The response of the lowest fundamental vibration mode was found to be highly dominant in all test cases. The results suggest that the amplitude and shape of the lowest fundamental vibration mode of the product's component board can be used to characterize the critical component locations, strain rates and strain amplitudes. Based on the results, a modification to the standardized board level drop tests is proposed in order to better reproduce the interactions of the product enclosure and component board during the test.