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This study is devoted to investigate the effects of the bump pitch on the capillary underfill flow. A micro particle image velocimetry (lPIV) 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 lm 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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Abstract. Elimination of the smear layer and bacteria in the root canal is the most important in the endodontic treatment, and various irrigation devices have been developed. Nevertheless, it is hard to eliminate the smear layer and bacteria completely. In this paper, a micro bubble irrigation system has been developed for the root canal cleaning of tooth. Micro bubbles are generated when pressurized fluids passing through a porous material inside a hand-piece nozzle, and the bubbly flows excited by ultrasonic vibration are observed using a high-speed camera and a microscope. The results show that the diameter and number of bubbles increases with the applied pressure, and there found an optimum excitation frequency in order to minimize the bubble size. From in-vitro tests, it is also verified that the developed bubble irrigation system has the ability of antibacterial and infection removal. Thus, this biocompatible system would be well suited for root canal cleaning.