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RESEARCH PAPERS

Behavior of Anisotropic Conductive Film (ACF) Joint under Mechanical Shock

[+] Author and Article Information
Rashed Adnan Islam

Department of Electronic Engineering, City University of Hong Kong, 83, Tat Chee Avenue, Kowloon Tong, Kowloon, Hong Kong

Y. C. Chan1

Department of Electronic Engineering, City University of Hong Kong, 83, Tat Chee Avenue, Kowloon Tong, Kowloon, Hong Kongeeycchan@cityu.edu.hk

1

Corresponding author. Tel.: +852-2788-7130; fax: +852-2788-7579.

J. Electron. Packag 127(4), 375-380 (Feb 14, 2005) (6 pages) doi:10.1115/1.2056570 History: Received February 20, 2004; Revised February 14, 2005

The contact resistances investigated by this study of ACF joints using AuNi bumps and flexible substrates are found to be increased by the induced mechanical shock and also by the combined effect of heat/humidity and the mechanical shock. The samples humidified at 85°C/85% RH for 384 h, on which a load of 3.164 Kg was dropped four times from a height of 0.4 m, exhibit the most severe results. The contact resistance increases by 700%, which had been about 62 mΩ in the as-bonded condition. The samples without humidification showed a sluggish and gentle increase in contact resistance with the induced mechanical shock. The contact resistance was found to be increased by 400% after the sixth drop from a height of 0.5 m. Scanning electron microscope images show particle deformation due to abrasion and friction between the contacting surfaces resulting from the sudden impact. Joints are also observed with no connections, which signify open circuits. Almost 25% of the circuits were found open in the samples (after 384 h in a humid environment), which have suffered severe mechanical shock (load drops four times from 0.4 m height). Breaking of the conductive layer of the particle and exposing the underlying polymeric portion were also observed.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 10

Percentage open circuits versus hours in the humidity chamber (after fourth drop)

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Figure 11

SEM image showing a perfectly bonded sample (as-bonded) and a completely open circuit condition

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Figure 12

SEM image showing hydrolysis due to the humidity attack

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Figure 1

Experimental setup of inducing mechanical shock and the side view of a chip package. Here X=0.2–0.5m

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Figure 2

Variation of contact resistance with dropping height as a function of number of drops

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Figure 3

SEM image of the deformed conducting particle due to abrasion

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Figure 4

The force distribution results from the mechanical shock

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Figure 5

SEM image showing loose conductive particle between the two connecting surfaces

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Figure 6

SEM image showing the eroded conductive layer leaving the polymer exposed

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Figure 7

Variation of contact resistance with hours in humidity chamber as a function of number of drops (height=0.2m)

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Figure 8

Variation of contact resistance with hours in humidity chamber as a function of number of drops (height=0.3m)

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Figure 9

Variation of contact resistance with hours in humidity chamber as a function of number of drops (height=0.4m)

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