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Journal of Nanomaterials
Volume 2015, Article ID 485276, 8 pages
Research Article

A Study on the Conductivity Variation of Au Coated Conductive Particles in ACF Packaging Process

1Department of Mechanical and Electromechanical Engineering, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
2Department of Mechanical Engineering, National Kaohsiung University of Applied Science, Kaohsiung 80778, Taiwan
3Department of Mechanical Engineering, Cheng Shiu University, Kaohsiung 83347, Taiwan

Received 30 September 2014; Accepted 14 December 2014

Academic Editor: Antonios Kelarakis

Copyright © 2015 Jao-Hwa Kuang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In the ACF packaging process, a bonding force will be applied to the ACF structure. The finite element analysis is used to simulate the ACF packaging process. Material behavior is assumed to be superelastic for resin, viscoelastic for polymer matrix, and elastic-plastic for metal, such as bump, pad, chip, and Au-film. The axis-symmetric model is employed in FEA simulation with time-varying bonding force and operating temperature. In this study, the parameters, including conductive particle diameter, Au-film thickness, and bonding force, are analyzed with nonliner and temperature-dependent material properties. The simulation results indicate that bonding force and operating temperature have strong effects on the formation of concave on Au-film. In addition, surface wrinkle of Au-film will be induced by the bonding force. Both of the concaving and the wrinkling on Au-film will decrease the contact area between the conductive particle and the bump and the contact area between the conductive particle and the pad. Decrease of the contact area means increase of the total resistance for the ACF structure. The results show that the smaller the conductive particle diameter, the smaller the contact area. Generally, increasing the thickness of Au-film will decrease the contact areas, except at the Au-film thickness of 0.05 μm.