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Research Papers

Measurement and Characterization of the Moisture-Induced Properties of ACF Package

[+] Author and Article Information
Ji-Young Yoon

Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Gu-seong, Yu-seong gu, Daejeon 305-701, Koreakoths82@kaist.ac.kr

Ilho Kim, Soon-Bok Lee

Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Gu-seong, Yu-seong gu, Daejeon 305-701, Korea

J. Electron. Packag 131(2), 021012 (Apr 21, 2009) (8 pages) doi:10.1115/1.3111252 History: Received January 10, 2007; Revised October 14, 2007; Published April 21, 2009

This study is to observe the exact behavior of anisotropic conductive adhesion (ACF) package under humid environments by obtaining the moisture-induced properties such as diffusion coefficient (the rate of moisture movement into the materials), saturated moisture content (the maximum absorbed quantity), and swelling coefficient (length change due to the chemical interaction). So the experiments were performed to get the moisture-induced properties of ACF and FR4 using newly developed method at various temperature and relative humidity conditions. Experimental results showed that the diffusion coefficient of ACF and FR4 follows Arrhenius’ equation very well, and the saturated moisture content of them follows Henry’s law, which means linear relationship between saturated moisture content and relative humidity, but the saturated moisture content of ACF is influenced by temperature as well as relative humidity. And the swelling coefficient of ACF and FR4 increases with temperature. Especially in the case of ACF, it shows the dramatic degradation due to Tg (glass transition temperature) at nearby 85°C. Finally, as using these experimental results, the behavior of the ACF package under humid environment is predicted through finite element simulation. When wetness defined by moisture content over saturated moisture content changes from 0 to 0.9, the center of the ACF package is subject to compression and the edge of the ACF package is subject to tension in the case of transient state. After all, because the edge of the ACF package is very weak due to bending moment, the failure is easy to occur under humid environment.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematics of the ACF flip chip joint

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Figure 2

Diagram of the model to calculate the diffusion coefficient

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Figure 3

The microscopic structure of the polymer

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Figure 4

The composition of the occupied volume

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Figure 5

Variation of moisture according to time

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Figure 6

The weight reduction in ACF according to time at various conditions

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Figure 7

The D of ACF versus temperature

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Figure 8

The Msat of ACF versus relative humidity

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Figure 9

In(D) versus 1/kT(K) curve of ACF

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Figure 10

ln(Msat) versus 1/kT curve of ACF

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Figure 11

The method to measure β of ACF

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Figure 12

Hygrostrain results from TGA and TMA for ACF

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Figure 13

The swelling coefficient of ACF versus temperature

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Figure 14

The measurement for Tg of dry ACF

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Figure 15

The measurement for Tg of wet ACF

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Figure 16

The weight change in FR4 versus time at various conditions

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Figure 17

The diffusion coefficient of FR4 versus temperature at various conditions

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Figure 18

The saturated moisture content of FR4 versus relative humidity at various conditions

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Figure 19

The fringe result of FR4 at 85°C/90%

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Figure 20

The swelling coefficient of FR4 versus relative humidity at various conditions

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Figure 21

Finite element model

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Figure 22

The wetness distribution in the ACF package after 1 year

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Figure 23

The von Mises stress distribution in ACF after 1 year

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Figure 24

The normal stress distribution in ACF after 1 year

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Figure 25

The change in von Mises stress according to time

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Figure 26

The change in normal stress according to time

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Figure 27

The deformation of the ACF package by bending moment under moisture environment

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