• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.652-655
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• 2001

In this paper, I have studied minimization of the kerf-width and surface burning which are occurred after the singulation process of multi layer $\mu$-BGA( thickness 1.1 mm, 0.9 mm) with a pulsed Nd:YAG( = 532 nm, repetition rate = 10 Hz) laser. The thermal energy of a pulsed Nd:YAG laser is used to cut the copper layer. I have studied are minimization of the surface burning and kerf-width using a photo resist, $N_2$blowing and polyester double sided tape as a cutting parameter. The $N_2$blowing reduces a laser energy loss by debris and suppresses a surface carbonization. Also, I have studied characters of cutting with a choice of side of laser beam incidence. The SEM(Scanning Electron Microscope), non-contact 3D inspector and high-resolution microscope are used to measure kerf width and surface state. The optimum value of 1.1 mm $\mu$-BGA singulation is 524 $\mu$m that is reduced kerf width of 60 % with $N_2$blowing. And I obtained reduction of carbonization of 68 % with a polyester double side tape in 0.9 mm $\mu$-BGA. I used laser intensity of 1.91$\times$10$^{6}$ / $\textrm{cm}^2$ in this study.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.60-63
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• 1999

Application of reactive ion etching (RIE) technique to Ta-Al alloy thin film with a thickness of $1000{\AA}$ was studied. $CF_{4}$ gas could be used effectively to etch the Ta-Al alloy thin film. The etching rate in the thin film with Ta content of 50 mol% was about $67{\AA}/min$. NO selectivity between the Ta-Al alloy film and $SiO_{2}$ film was observed during the etching using the $CF_{4}$ gas. The etching rate of the $SiO_{2}$ layer was 12 times faster than that of the Ta-Al alloy thin film. It was also observed that photoresist of AZ5214 was more useful than Shiepley 1400-27 in RIE with the $CF_{4}$ gas.

• Steel and Composite Structures
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• v.18 no.2
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• pp.357-374
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• 2015

Orthotropic decks composed of deck plate, ribs, cross beams and wearing surface are frequently used in industry to span long distances due to their light structures and load carrying capacities. As a result they are broadly preferred in industry and there are a lot of bridges of this type exist in the world. Nevertheless, some of them cannot sustain the anticipated service life and damages in form of cracks develop in steel components and wearing surface. Main reason to these damages is seen as the repetitive wheel loads, namely the fatigue loading. Solutions to this problem could be divided into two categories: qualitative and quantitative. Qualitative solutions may be new design methodologies or innovative materials, whereas quantitative solution should be arranging dimensions of deck structure in order to resist wheel loads till the end of service life. Wearing surface on deck plate plays a very important role to avoid or mitigate these damages, since it disperses the load coming on deck structure and increases the bending stiffness of deck plate by forming a composite structure together with it. In this study the effect of Elastic moduli, Poisson ratio and thickness of wearing surface on the stresses emerged in steel deck and wearing surface itself is investigated using a FE-model developed to analyze orthotropic steel bridges.

• Korean Journal of Materials Research
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• v.32 no.4
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• pp.200-209
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• 2022

In this study, defects generated in the YSZ coating layer of the IN738LC turbine blade are investigated using an optical microscope and SEM/EDS. The blade YSZ coating layer is composed of a Y-Zr component top coat layer and a Co component bond coat layer. A large amount of Cr/Ni component that diffused from the base is also measured in the bond coat. The blade hot corrosion is concentrated on the surface of the concave part, accompanied by separation of the coating layer due to the concentration of combustion gas collisions here. In the top coating layer of the blade, cracks occur in the vertical and horizontal directions, along with pits in the top coating layer. Combustion gas components such as Na and S are contained inside the pits and cracks, so it is considered that the pits/cracks are caused by the corrosion of the combustion gases. Also, a thermally grown oxide (TGO) layer of several ㎛ thick composed of Al oxide is observed between the top coat and the bond coat, and a similar inner TGO with a thickness of several ㎛ is also observed between the bond coat and the matrix. A PFZ (precipitate free zone) deficient in γ' (Ni₃Al) forms as a band around the TGO, in which the Al component is integrated. Although TGO can resist high temperature corrosion of the top coat, it should also be considered that if its shape is irregular and contains pore defects, it may degrade the blade high temperature creep properties. Compositional and microstructural analysis results for high-temperature corrosion and TGO defects in the blade coating layer used at high temperatures are expected to be applied to sound YSZ coating and blade design technology.

• Advances in nano research
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• v.13 no.2
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• pp.199-206
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• 2022

We present the high-brightness large-area 10.1" in-cell polarizer display panel integrated with a wire grid polarizer (WGP) and metal reflector, from the initial design to final system development in a commercially feasible level. We have modeled and developed the WGP architecture integrated with the metal reflector in a single in-cell layer, to achieve excellent polarization efficiency as well as brightness enhancement through the light recycling effect. After the optimization of key experimental parameters via Taguchi method, the roll nanoimprint lithography employing a flexible large-area tiled mold has been utilized to create the 90 nm-pitch polymer resist pattern with the 54.1 nm linewidth and 5.1 nm residual layer thickness. The 90 nm-pitch Al gratings with the 51.4 nm linewidth and 2150 Å height have been successfully fabricated after subsequent etch process, providing the in-cell WGPs with high optical performance in the entire visible light regime. Finally we have integrated the WGP in a commercial 10.1" display device and demonstrated its actual operation, exhibiting 1.24 times enhancement of brightness compared to a conventional film polarizer-based one, with the contrast ratio of 1,004:1. Polarization efficiency and transmittance of the developed WGPs in an in-cell polarizer panel achieve 99.995 % and 42.3 %, respectively.

• Polymer(Korea)
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• v.38 no.5
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• pp.640-644
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• 2014

As a process of plat panel display production, slot coating is widely used for the coating of photoresist on a wide glass substrate. A uniform coating thickness is important, and the coating uniformity is divided into nozzle and machine directions. The machine and nozzle directions coating uniformities are influenced by the operation condition of coater and flow uniformity inside the die, respectively. Non-uniform coating during steady coating process occurs according to those factors, however, non-uniform coating along the machine and nozzle directions has been observed at the beginning of coating by unsteady flow. In this study, steady and unsteady state flow simulations have been performed and compared with experiment to examine the causes of non-uniform coating. Computational results exhibited that it took a time to get a uniform pressure distribution at whole inside the die, and during this period of time edge regions showed lower exit velocity compared with center region. Subsequently edge regions had thinner coated layers than center region. However edge regions showed higher exit velocity than center region after steady state, and this made edge regions had thicker coated layer than center region.