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Micro-PIV measurements of capillary underfill flows and effect of bump pitch on filling process

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Abstract

This study is devoted to investigate the effects of the bump pitch on the capillary underfill flow. A micro particle image velocimetry (μPIV) system was used to visualize the flows and the shape of meniscus. Transparent flip chip specimens with quadrilateral bump arrangements were fabricated by etching silicon on glass wafer. Six bump pitches from 60 to 160 μm were tested and glycerin was dispensed to fill into the flip chip specimens. From the present experiments, it is shown that the overall filling speed becomes faster at larger bump pitch and changes abruptly when the bump pitch is twice the bump diameter. The detailed meniscus movement also has different behavior if the bump pitch gets smaller and larger than twice the bump diameter. The variation of dynamic contact angle is synchronized with that of the meniscus velocity throughout the whole process. During the interaction with the flip chip bumps, the contact line of the meniscus becomes concave or convex. The curvature of the concave and convex lines is larger at the smaller bump pitch.

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Acknowledgments

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0009054).

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Authors and Affiliations

  1. Graduate School of Energy and Environment, Seoul National University of Science and Technology, 172, Gongreung-dong, Nowon-gu, Seoul, 139-743, Korea

    Young Bae Kim

  2. Department of Mechanical Engineering, Seoul National University of Science and Technology, 172, Gongreung-dong, Nowon-gu, Seoul, 139-743, Korea

    Jaeyong Sung & Myeong Ho Lee

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  1. Young Bae Kim
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  2. Jaeyong Sung
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  3. Myeong Ho Lee
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Correspondence to Jaeyong Sung.

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Kim, Y.B., Sung, J. & Lee, M.H. Micro-PIV measurements of capillary underfill flows and effect of bump pitch on filling process. J Vis 14, 237–248 (2011). https://doi.org/10.1007/s12650-011-0073-2

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  • DOI: https://doi.org/10.1007/s12650-011-0073-2

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