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Research Papers

Variable-Length Link-Spring Model for Kink Formation During Wire Bonding

[+] Author and Article Information
Fuliang Wang

e-mail: wangfuliang@csu.edu.cn

Lei Han

State Key Laboratory of High Performance
Complex Manufacturing,
Changsha 410083, China;
School of Mechanical and Electrical Engineering,
Central South University,
Changsha 410083, China

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received June 5, 2012; final manuscript received July 13, 2013; published online September 19, 2013. Assoc. Editor: Kaustubh Nagarkar.

J. Electron. Packag 135(4), 041004 (Sep 19, 2013) (6 pages) Paper No: EP-12-1061; doi: 10.1115/1.4025308 History: Received June 05, 2012; Revised July 13, 2013

Kinks have a strong influence on the structural performance of wire bonds. In this study, a variable-length link-spring model has been developed to better understand kink formation. In this model, a gold wire was decomposed into segments that were represented by a link and a torsional spring. One end of the gold wire was fixed, and the other end was free. The friction and air tension forces at the wire ends were considered a function of the capillary position, and the wire segments and moment balance equations were added at the free end as the wire length increased. By using this model, the wire profile, moment, and curvature diagrams at the reverse motion stage were obtained to study the dynamical kink formation and wire-length increasing processes. The analysis result was verified experimentally. Good agreement is obtained between the analytical and the experimental wire profiles. This study indicates that a moment magnitude of several hundred mN·μm is required to form a kink, and the wire profile is the result of the residual curvature and the instantaneous bending moment.

FIGURES IN THIS ARTICLE
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Copyright © 2013 by ASME
Topics: Wire , Springs , Deformation
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References

Figures

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Fig. 1

Wire-length increase and kink formation processes

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Fig. 2

Schematic of variable-length link-spring model

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Fig. 3

Relation between M and Δθ [11]

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Fig. 4

Wire profiles at different capillary positions

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Fig. 5

Images at four positions from the experiment

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Fig. 6

Comparison of loop profiles between the experimental and the analysis results

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Fig. 7

Moment and curvature distribution along the wire (−55 μm RM)

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Fig. 8

Moment and curvature distribution along the wire (−155 μm RM)

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Fig. 9

Moment and curvature distribution along the wire (−411.6 μm RM)

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