• Journal of the Microelectronics and Packaging Society
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• v.25 no.1
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• pp.29-33
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• 2018

Flexible electronics must be stable under various deformations such as bending, folding, and rolling. The reliability of ITO (Indium Tin Oxide) film used widely as a transparent electrode for flexible electronics has been studied using rolling fatigue test and bending test. During repeated rolling deformations, the electrical resistance was in-situ measured with different number of rotation. During rolling fatigue test, the electrical resistance of ITO film was significantly increased with increasing the number of rotation. As the stress state of ITO film is different according to the relative position of ITO and substrate, the rolling fatigue test was investigated under both outer and inner bending conditions. Inner rolling fatigue test showed superior electrical stability because the crack nucleation and propagation were retarded under compressive stress state.

• Journal of Welding and Joining
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• v.14 no.2
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• pp.57-64
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• 1996

In this paper, authors are trying to find optimum spot weldig conditions to minimize indentation of the plate surface which is crucial to quality of stainless rolling stocks. At first, to derive a simple equation to estimate the depth of indentation, a simplified one-dimensional bar model is proposed and validity of the model is confirmed by experiments. And also, to find proper welding conditions giving satisfied tensile strength of the welded joint, a simple formula is derived referring to the standard spot welding conditions by AWS. Optimization problem is formulated to find welding conditions such as welding current, time and applied force which give minimum indentation and proper tensile strength of joint, and solutions are found out. According to the results, the depth of indentation can be expressed by applied electrode froces and it can be shown that an optimum applied force exists.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.10a
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• pp.118-118
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• 2003

In a rolling wire probe, a key component of an inspection apparatus for PDP electrode patterns, the electric performance of it is known to be strongly dependent on the surface condition of a collet pin, a needle pin, and a wire. However, the collet and needle pins rotate very rapidly in contact with each other, which results in the degradation of the surface by the heat and friction and finally the formation of black wear marks on the surface after a several hundred hours test. Once the black wear marks appear on the surface, the electric resistance of the probe increases sharply and so the integrity of the probe is severely damaged. In this experiment, TiN coating, which has excellent electric conductances and good wear-resistance, has been applied on the surface of collect and needle pins for preventing the surface damages. In order to achieve the homogeneous coating with a good adhesion property, special coating substrate stages and jigs were designed and applied during coating. TiN has been deposited using 99.999% Titanium target by a DC reactive sputtering method. According to the components and jigs, processing parameters, such as DC power, RF bias and the flow rate ratio of Ar and N$_2$ used as reactive gases, has been controlled to obtain good TiN films. Detailed problems and solutions for applying the new substrate stages and jigs will be discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5039-5044
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• 2015

In this study, we evaluated corrosion behavior of a common rolling stock axle material, RSA1, in seawater. 3-electrode electrochemical cell experiment was conducted using artificial sea water, fabricated according to ASTM-D1141 set by American Society for Testing and Materials, where the corrosion current density and corrosion rate were determined to be $18.3{\mu}A/cm2$ and 0.217 mm/yr, respectively, by employing potentiodynamic test method and impedance spectroscopy method. Considering the fact that life time of railway car is ~25 years, the expected corrosion layer depth is 5mm. Constant-current corrosion test was conducted to accelerate the corrosion process, to reach corrosion periods of 1,3 and 4 years based on Faraday's law, followed by tension tests where the reduced specimen gauge cross-section was re-measured for stress calculation. While no apparent corrosion-related changes in mechanical properties were observed in the elastic regime, the reduction in ductility of the material was found to be increased as the corrosion period increased. The results of this study are expected to be basic corrosion data for the design of rolling stock axles, which will be operated in the sea water environment.

• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.77-81
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• 2005

Porous-composite electrodes have been developed using silica gel, which reduce carbon aerogel usage with high cost. Silica gel powder was added to the carbon aerogel to simplify the manufacturing procedure and to increase the wet-ability, the mechanical strength and the CDI efficiency. Porous composite electrodes composed of carbon aerogel and silica gel powder were prepared by paste rolling method. Carbon aerosol composite electrodes with $10\times10cm^2$ are placed face to face between spacers, and assembled the four-stage series cells for CDI process. Each stage is composed of 45 cells. Four-stage series cells (flow through cells) for CDI process are put in continuous-system reactor containing 1,000ml-NaCl solution bath of 1,000 ppm. The four-stage series cells with carbon aerogel electrodes are charged at 1.2V and are discharged at 0.001V, and then read the current. Conclusively, removal efficiencies of ions using the four-stage series cells composed of carbon aerogel composite electrodes show good removal efficiency of $99\%$ respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.181.2-181.2
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• 2016

OLED 소자는 발광 방향에 따라 Bottom Emission 방식과 Top Emission 방식으로 나뉜다. 이 중 대면적 OLED TV 적용에 개구율이 더 높은 Top Emission방식을 선호하는 추세이다. 높은 개구율을 가진 Top Emission OLED소자를 위해서는 투명하고 전도성이 높은 캐소드가 중요하다. 본 연구에서는 Themal Evaporation 시스템을 이용하여 증착한 $SnO_2/Ag-Pd-Cu(APC)/SnO_2$ hybrid 전극의 특성을 연구하고 Oxide/Metal/Oxide(OMO) hybrid 박막의 bending mechanism을 제시하였다. base pressure는 $1{\times}10^{-6}Torr$로 고정하고 $SnO_2$ 박막은 0.34A / 0.32V, APC 박막은 0.46A / 0.40V의 power로 성막하였다. APC와 $SnO_2$의 두께를 변수로 OMO 전극을 제작하였고 그 전기적, 광학적 특성을 Hall measurement, UV/Visible spectroscopy을 이용하여 분석하고 Figure of merit 값을 바탕으로 최적 두께를 설정하였다. UPS(Ultraviolet Photoelectron Spectroscopy) 분석으로 $SnO_2/APC/SnO_2$ 전극의 일함수을 통해 투명 cathode로 쓰였을 때 $SnO_2$ 층이 buffer layer역할을 함을 확인하였다. XPS(X-ray photoelectron spectroscopy)를 이용하여 정성분석과 정량분석을 하였고 OMO hybrid 전극의 bending mechanism 연구를 위해 다양한 bending test (Inner/Outer dynamic fatigue test, twisting test, rolling test)를 진행하였다. 물리적 힘이 가해진 OMO hybrid 전극의 표면과 구조는 FE-SEM(Field Emission Scanning Electron Microscope) 분석을 통해서 확인할 수 있었다.

• Journal of Welding and Joining
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• v.27 no.3
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• pp.92-96
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• 2009

Metallic sandwich plate has many good properties such as high specific stiffness, high specific strength, good impact absorptivity, effective thermal insulation and soundproofing. In our study, a new bonding method, 3-layer roll projection welding, is introduced to fabricate the metallic sandwich plate. The new method uses a pair of roll electrodes like the seam welding, and projection welding is made at two internal interfaces of the 3-layer weldment consisting of a structured inner sheet and a pair of skin sheets. During the welding process, skin sheet temperature are measured to produce metallic sandwich plate with uniform and good quality. But it is difficult to observe or measure the temperature at the welding points during welding process because the welding points exist at the internal interfaces. Therefore FEM numerical analysis using ABAQUS is conducted to estimate the generated heat at the welding points with different welding conditions.

• Journal of the Korean Electrochemical Society
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• v.3 no.4
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• pp.204-210
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• 2000

The control of dissolved aluminum concentration in the hot dip zinc galvanizing bath is greatly important in producing galvannealed steel sheets. The purpose of present study is to provide basic data for measurement of the aluminum concentration in site in hot dip zinc bath at the temperature of $460^{\circ}C\~500^{\circ}C$ using $CaF_2$ solid electrolyte sensor with three kinds of reference electrode. Good workability and stability of the sensor were confirmed with the $Bi+BiF_3$ reference electrode from the emf measurement. In order to measure the aluminum concentration in Zn-Al bath, the galvanic cell of fluorine ion was constructed with $CaF_2$ solid electrolyte as follows; $$(-)W|Zn-Al,\;AlF_3|CaF_2|Bi,BiF_3|W(+)$$. The emf measurement was made at the temperature of $460\pm10^{\circ}C$ in the Zn-Al bath. The following correlationship between aluminum concentration and emf was obtained by the least square regression analysis; $$E/mV=56.795log[\%Al]+1881.7\;R=0.9704$$,$$0.026wt\%{\leq}[\%Al]{\leq}0.984wt\%$$

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.64-64
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• 2008

연속공정이 가능한 Roll to Roll sputter system을 이용하여 플렉시블 indium tin oxide(ITO) 투명전극을 PET(polyethlyene terephthalate) 기판위에 성막하였다. 연속 성막공정을 위해 Roll to Roll sputter system에서의 unwinder roller와 rewinder roller를 이용한 servomotor의 rolling으로 기판의 움직임이 완벽히 제어되었으며, 외부 응력으로 부터의 안정성 및 성막 공정 시의 PET 기판의 열적 변형을 최소화하기 위한 접촉식 냉각방식의 cooling system을 main drum으로 사용하였다. 또한 고분자 기판과 투명전극 사이의 adhesion을 향상시키기 위한 전처리 공정으로 gridless linear ion beam source를 pretreatment system으로 구축하였다. 이렇게 제작된 Roll to Roll sputter system을 이용하여 PET 기판위에 연속공정을 통해 ITO 투명전극을 성막하였다. 성막된 플렉시블 ITO/PET 투명전극은 XRD, HREM, SEM 분석을 통하여 main drum의 cooling에 의해 완전한 비정질 구조를 나타내었음을 확인할 수 있었으며, 비록 Roll to Roll sputter system을 통하여 상온에서 성막 되었음에도 불구하고 최적화 된 조건에서 가시광선 영역 83.46 %의 높은 광투과도 값과 47.4 Ohm/square의 비교적 낮은 먼저항 값을 얻을 수 있었다. 또한 Bending test 결과를 통하여 ion source의 전처리 공정으로 굽힘/평의 반복적 응력에 따른 전기적 특성 열화를 최소화 할 수 있음을 보였다. 최적화된 플렉시블 투명전극을 이용하여 P3HT:PCBM 기반의 플렉시블 유기태양전지를 제작하였으며, 제작된 유기태양전지로부터 1.88%의 power conversion efficiency (PCE)을 확보함으로써 플렉시블 유기태양전지 제작을 위한 ITO/PET 투명전극 성막 공법으로써 Roll to Roll sputter system의 적용가능성을 확인할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.201.1-201.1
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• 2014

본 연구에서는 Slot die coating 공법으로 코팅된 Poly (3-4 ethylenedioxythiophene): Poly (styrenesulfonate) (PEDOT:PSS) 박막과 비정질 ITO 박막의 전기적, 광학적, 기계적 특성을 비교 평가하여 Slot die coating 공법으로 코팅된 PEDOT:PSS 박막의 유기태양전지의 전극으로서의 적용가능성을 확인하였다. 상업용 PEDOT:PSS 박막은 보통 280 Ohm/sq.의 면저항과 가시광 영역에서 약 80%의 광투과도를 나타내며, 비정질 ITO 박막과 유사한 전기적, 광학적 특성을 나타내었다. Slot die coating 공법을 통해 제작된 PEDOT:PSS 투명 전극과 비정질 ITO 투명 전극의 기판 휘어짐에 따른 전기적 안정성을 비교 평가하기 위해 25 mm에서 1 mm까지 radius 변화에 따른 저항의 변화를 측정하였다. 그 결과, 비정질 ITO 투명 전극 대비 PEDOT:PSS 투명 전극이 더 우수한 전기적 안정성을 나타냄을 확인하였다. 또한, 다양한 Bending test (Inner/Outer bending, Rolling, Stretching, Twisting) 를 통해 비정질 ITO 투명 전극 보다 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 전극의 우수한 기계적 특성을 확인하였다. 이를 바탕으로 Flexible 유기태양전지에의 적용 가능성을 알아보기 위해 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 전극과 비정질 ITO 투명 전극을 유기태양전지의 anode 층에 적용하여 각각 제작하고 그 특성을 평가하였다. 비정질 ITO 투명 박막을 적용한 유기태양전지 대비 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 박막으로 제작한 유기태양전지에서 더 높은 효율이 나타났으며, 이로써 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 전극의 Flexible 유기태양전지로써의 적용 가능성을 확인하였다.