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Research Papers

Shock and Dynamic Loading in Portable Electronic Assemblies: Modeling and Simulation Results

[+] Author and Article Information
A. F. Askari Farahani, M. Al-Bassyiouni

Mechanical Engineering Department,  Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD 20742

A. Dasgupta1

Mechanical Engineering Department,  Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD 20742

1

Corresponding author.

J. Electron. Packag 133(4), 041012 (Dec 09, 2011) (12 pages) doi:10.1115/1.4005091 History: Received March 12, 2010; Revised April 13, 2011; Published December 09, 2011; Online December 09, 2011

In this study, the transient response of electronic assemblies to mechanical loading encountered in drop and shock conditions are investigated with transient finite element methods. Many manufacturers face design challenges when evolving new designs for high strain-rate life cycle loading. Examples of high strain-rate loading include drop events, blast events, vibration, ultrasonic process steps, etc. New design iterations invariably bring new unexpected failure modes under such loading and costly trial-and-error design fixes are often necessary after the product is built. Electronics designers have long sought to address these effects during the design phase, with the aid of computational models. However, such efforts have been difficult because of the nonlinearities inherent in complex assemblies and complex dynamic material properties. Our goal in this study is to investigate the ability of finite element models to accurately capture the transient response of a complex portable electronic product under shock and drop loading. Finite element models of the system are generated and calibrated with experimental results, first at the subsystem level to calibrate material properties and then at the product level to parametrically investigate the contact mechanics at the interfaces. The parametric study consists of sensitivity studies for different ways to model soft, nonconservative contact, as well as structural damping of the subassembly under assembly boundary conditions. The long-term goal of this study is to demonstrate a systematic modeling methodology to predict the drop response of future portable electronic products, so that relevant failure modes can be eliminated by design iterations early in the design cycle.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Portable electronic product subjected to drop testing and simulations

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Figure 2

Clamped PWB meshed geometry

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Figure 3

The first two mode shapes of the clamped PWB with 20% increase in elastic modulus

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Figure 4

Natural frequencies of the bare PWB

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Figure 5

FEA input pulse applied at post holes 1 and 2

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Figure 6

Acceleration at the free end of the clamped PWB. Acceleration is measured in the out-of-plane direction—FEA versus experiment.

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Figure 27

Drop test of full product assembly (acceleration response): FEA predictions versus test measurements

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Figure 28

FFT response of the strain gage on the PWB to drop loading

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Figure 29

Acceleration FFT response of the PWB to drop loading

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Figure 26

Drop test of full product assembly (strain response): FEA predictions versus test measurements

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Figure 25

Effect of Raleigh damping on strain and acceleration range of the first cycle and rms values

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Figure 24

Effect of fraction of critical damping on strain and acceleration range of the first cycle, as well as the normalized strain and acceleration rms values

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Figure 23

Effect of contact stiffness on the strain and acceleration range of the first cycle, as well as normalized strain and acceleration rms values

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Figure 22

Comparison of the experimental strain response of the PWB with those of the FEA models with soft and hard contact properties

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Figure 21

Comparison of the experimental strain histogram with those of the FEA models with soft and hard contact properties

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Figure 20

Comparison of the experimental acceleration histogram with those of the FEA models with soft and hard contact properties

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Figure 19

Comparison of the experimental acceleration response with those of the FEA models with soft and hard contact properties

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Figure 18

Shock test FEA predictions versus test measurements. The acceleration is measured on the PWB in the out-of-plane direction.

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Figure 17

Full product assembly

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Figure 16

Frequency response function of the empty housing measured at the accelerometer T

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Figure 15

Dynamic mode shapes for the empty housing

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Figure 14

FEA model of empty housing. Acceleration is measured in the out-of-plane direction at T and B locations.

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Figure 13

Natural frequencies of the spring-mounted PWB

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Figure 12

Spring-mounted model

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Figure 11

FFT response of the strain gage to drop loading

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Figure 10

Strain at the post of the clamped PWB: FEA versus experiment

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Figure 9

Acceleration at the free end of the clamped PWB: FEA versus experiment

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Figure 8

FFT response of the strain gage to shock loading

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Figure 7

Strain at the post of the clamped PWB. Strain is measured in the xx direction—FEA versus experiment.

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