Drop impact of a typical portable electronic device

Abstract

Drop impact reliability is an important concern for the design and use of portable electronic products. When the product is accidentally dropped on the ground, impact forces are transmitted from the product case to the printed circuit board (PCB) and other components within the case. These forces may cause severe functional damage in the form of component failure and/or interconnection breakage. This paper reports our investigation on the dynamic behaviours of a typical portable electronic device under drop impact loading. Firstly, an idealized system which contains an outer case and a PCB attached with a package was adopted as specimen. With an innovative design, the actual impact force pulses were measured by employing a Hopkinson bar in the dynamic test rig. Dynamic strains of the PCB were simultaneously recorded to explore the correlation between the strains and the impact pulse. Particular attention has been paid to the dependence of the shock response of the PCB on the impact velocity, impact force pulse, as well as the impact orientation. Analysis is carried out to explain the experimental results. A deep understanding of the shock response of typical electronic product systems will help to guide the design of rugged and highly impact-resistant devices Keywords: portable electronic products, drop test, impact. IntroductionBenefit from the advancements of new technologies, electronic components have become smaller, thinner and lighter. Today, portable electronics, such as cellular phones, PDAs (personal digital assistants), digital cameras etc. Kowloon, Hong Kong, China substantial market share worldwide. It should be noted, however, that portable devices are often exposed to relatively harsh operating environments due to the likelihood of dropping these devices and also making impact with other objects. And drop/impact induces failure is one of the most dominant causes of damage for portable devices. Therefore, drop impact reliability is one of the major concerns in product design.Traditionally, the rigidity of products is obtained through a design-failureredesign process. It is evident from engineering practice that in order to improve the shock protection of portable electronics, instead of making protective designs on a trial-and-error basis, one must understand how electronic components or portable electronic devices respond to shock and impact loading. And drop testers were firstly designed by researchers to assess drop/impact performance of the products. Jason Wu et al. [1] pointed out that drop tests through hand-drop and eye-check can only give a qualitative but no quantitative information about impact behavior. They introduced a drop tester which can control drop orientation by two slide cables. In order to control the orientation of the object at impact and to instrument the drop tests, S. Goyal and E. K. Buratynski [2] also proposed a method that the specimen be suspended onto a guided drop-table in desired orientation. The drop-table hits the ground first, but just before impact, the t...