• Journal of the Microelectronics and Packaging Society
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• v.8 no.1
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• pp.33-38
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• 2001

We investigate the via-size dependance of as-electroplated- and reflow-bump shapes for realizing both high-density and high-aspect ratio of solder bump. The solder bump is fabricated by subsequent processes as follows. After sputtering a TiW/Al electrode on a 5-inch Si-wafer, a thick photoresist for via formation it obtained by multiple-codling method and then vias with various diameters are defined by a conventional photolithography technique using a contact alinger with an I-line source. After via formation the under ball metallurgy (UBM) structure with Ti-adhesion and Cu-seed layers is sputtered on a sample. Cu-layer and Sn/pb-layer with a competition ratio of 6 to 4 are electroplated by a selective electroplating method. The reflow-bump diameters at bottom are unchanged, compared with as-electroplated diameters. As-electroplated- and reflow-bump shapes, however, depend significantly on the via size. The heights of as-electroplated and reflow bumps increase with the larger cia, while the aspect ratio of bump decreases. The nearest bumps may be touched by decreasing the bump pitch in order to obtain high-density bump. The touching between the nearest bumps occurs during the overplating procedure rather than the reflowing procedure because the mushroom diameter formed by overplating is larger than the reflow-bump diameter. The arrangement as zig-zag rows can be effective for realizing the flip-chip-interconnect bump with both high-density and high-aspect ratio.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.351-357
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• 2013

In flip chip packaging, underfill process is used to fill epoxy bonder into the gap between a chip and a substrate in order to improve the reliability of electronic devices. Underfill process by capillary motion can give rise to unwanted air void formations since the arrangement of solder bumps affects the interfacial dynamics of flow meniscus. In this paper, the unsteady flows in the capillary underfill process are visualized and then the racing effect and merging of the meniscus are investigated according to the arrangement of solder bumps. The result is shown that at higher bump density, the fluid flow perpendicular to the main direction of flow becomes stronger so that more air voids are formed. This phenomenon is more conspicuous at a staggered bump array than at a rectangular bump array.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.4
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• pp.307-320
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• 1989

This paper presetns new design of the Modified Chemical Vapor Deposition(MCVD) system for optical fiber preform fabrication. It contains a glass working lathe, raw material supplier and exhaust gas treatment apparatus as fundamental instruments for MCVD process, graded index fiber design, characteristic of process and the experimenta arrangement to measure the refractive index profile of MCVD preforms, respectively. From the investigation results, it is shown that an ideal graded index fiber preform does not exhibit a center dip or bump.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.4
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• pp.367-375
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• 2014

In numbers of kinds of heat exchanger, the shell-tube heat exchanger is the most commonly used type of heat exchanger in the industry field. In order to improve the thermal performance of the heat exchanger, this study was analyzed heat transfer characteristics according to arrangement of baffle and direction of baffle and bump phase of baffle about shell-tube heat exchanger using appropriate SST (Shear Stress Transport) turbulence model for flow separation and boundary layer analysis. As the boundary condition for CFD (Computational Fluid Dynamics) analysis, the inlet temperature of shell side was constantly 344 K and the variation of the water flow rate was 6, 12, 18 and 24 l/min. As the result of analysis, zigzag baffle arrangement enhances heat transfer rate and pressure drop. Furthermore, in the direction of the baffle, heat transfer rate is more improved with vertical type and angle $45^{\circ}$ type than existing type, and pressure drop was little difference. Also, the bump shape of baffle surface contributes to heat transfer rate and pressure drop improvement due to the increased heat transfer area. Through analysis results, we knew that the increase of the heat transfer was influenced by flow separation, fluid residual time, contact area with the tube, flow rate, swirl and so on.