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research-article

Influence of Secondary Impact on Printed Wiring Assemblies-Part II: Competing Failure Modes in Surface Mount Components

[+] Author and Article Information
Jingshi Meng

Center for Advanced Life Cycle Engineering (CALCE) Mechanical Engineering Department University of Maryland College Park, MD 20742
mengjshi@umd.edu

Abhijit Dasgupta

Center for Advanced Life Cycle Engineering (CALCE) Mechanical Engineering Department University of Maryland College Park, MD 20742
dasgupta@umd.edu

1Corresponding author.

ASME doi:10.1115/1.4036187 History: Received September 26, 2015; Revised March 01, 2017

Abstract

Portable electronic devices are commonly exposed to shock and impact loading due to accidental drops. After external impact, internal collisions (termed “secondary impacts” in this study) between vibrating adjacent subassemblies of a product may occur if design guidelines fail to prevent such events. Secondary impacts can result in short acceleration pulses with much higher amplitudes and higher frequencies than those in conventional board level drop tests. Thus such pulses are likely to excite the high frequency resonances of printed wiring boards (PWBs) (including through-thickness ‘breathing’ modes) and also of miniature structures in assembled surface mount technology (SMT) components. Such resonant effects have a strong potential to damage the component, and therefore should be avoided. When the resonant frequency of a miniature structure (e.g. elements of a SMT MEMS component) in an SMT assembly is close to a natural frequency of the PWB, an amplified response is expected in the miniature structure. Components which are regarded as reliable under conventional qualification test methods, may still pose a failure risk when secondary impact is considered. This paper is the second part of a two-part series exploring the effect of secondary impacts in a printed wiring assembly (PWA). The first paper is this series focused on the ‘breathing’ mode of vibration generated in a PWB under secondary impact and this paper focuses on analyzing the effect of such ‘breathing’ modes on typical failure modes with different resonant frequencies in SMT applications. The results demonstrate distinctly different sensitivity of each failure mode to the impacts.

Copyright (c) 2017 by ASME
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