• 한국초전도ㆍ저온공학회논문지
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• 제8권3호
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• pp.23-26
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• 2006

For mechanical and electrical stability and environment protection. Cu and stainless steel stabilizers are laminated to a Ag layer to produce a composite neutral-axis(N-A) architecture in which the YBCO layer is centered between the oxide buffered metallic substrate and stabilizer strip lamination. This architecture allows the wire to meet operational requirements including stresses at cryogenic temperature. winding tensions as well as mechanical bending requirements including thermal and electrical stability under fault current conditions. We have experimentally studied mechanical properties of the laminated stainless steel and Cu stabilizers on YBCO coated conductors. We have laminated YBCO coated conductors by continuous dipping soldering process. We have investigated lamination interface between solder and stabilizer of the YBCO coated conductor. We evaluated bonding properties. tensile / shear bonding strength. and peeling strength laminated YBCO coated conductors.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.363-364
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• 2009

본 연구는 IEC/TC 90 규격을 참조하여 Cu stabilizer/Ag/$LaMnO_3$/IBAD-MgO/$Y_2O_3$/$Al_2O_3$/Hastelloy C276/Cu stabilizer의 구조를 가지는 coated conductor의 DC 임계 전류의 결정에 대한 사전 연구를 위해 (1) 시편의 냉각시간, (2) 전류 선의 용량을 변화하여 임계 전류의 변화를 관찰하여 다음과 같은 결과를 얻었다. (1) 5분 이상의 시편 냉각시간은 COV가 약 0.4% 정도로 거의 임계 전류 결정에 영향을 주지 않았으며, 냉각 시간이 길면 길수록 임께 전류 이하에서 전압의 기저면이 낮아지는 경향을 보였다. (2) 전류 선의 용량이 클수록 임계 전류 이하에 전압의 기저면이 낮아지는 경향을 보였다.

• Journal of Welding and Joining
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• 제29권5호
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• pp.95-98
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• 2011

Recently, there is a growing tendency that fine-pitch electronic devices are increased due to higher density and very large scale integration. Finer pitch printed circuit board(PCB) is to be decrease insulation resistance between circuit patterns and electrical components, which will induce to electrical short in electronic circuit by electrochemical migration when it exposes to long term in high temperature and high humidity. In this research, the effect of soldering flux acting as an electrical carrier between conductors on electrochemical migration was investigated. The PCB pad was coated with OSP finish. Sn3.0Ag0.5Cu solder paste was printed on the PCB circuit and then the coupon was treated by reflow process. Thereby, specimen for ion migration test was fabricated. Electrochemical migration test was conducted under the condition of DC 48 V, $85^{\circ}C$, and 85 % relative humidity. Their life time could be increased about 22% by means of removal of flux. The fundamentals and mechanism of electrochemical migration was discussed depending on the existence of flux residues after reflow process.

• 한국전기전자재료학회논문지
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• 제23권7호
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• pp.550-553
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• 2010

The enhancement of quantum efficiency using a surface modified Ag anode in top-emitting organic light emitting diodes (TEOLEDs) is reported. The operation voltage at the current density of $1\;mA/cm^2$ of TEOLEDs decreased from 9.3 V to 4.3 V as the surface of anode coated with $CuO_x$ layer. The work function of these structures were quantitatively determined using synchrotron radiation photoemission spectroscopy. Secondary electron emission spectra revealed that the work function of the Ag/$CuO_x$ structure is higher by 0.6 eV than that of Ag. Thus, the $CuO_x$ structure acts as a role in reducing the hole injection barrier by about 0.6 eV, resulting in a decrease of the turn-on voltage of top-emitting light emitting diodes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.249-249
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• 2013

Surface-enhanced Raman spectroscopy (SERS) is a sensitive approach to detect and to identify a variety of molecules. To enhance the Raman signal, optimization of the gap between nanostructures is quite important. One-dimensional materials such as nanowires, nanotubes, and nanograsses have great potential to be used in SERS due to their unique sizes and shape dependent characteristics. In this study we investigate a simple way to fabricate SERS substrates based on randomly grown copper oxide (CuO) nanowires. CuO nanograss is fabricated on pre-cleaned Cu foils. Cu oxidized in an ammonium ambient solution of 2.5 M NaOH and 0.1 M $(NH_4)_2S_2O_8$ at $4^{\circ}C$ for 10, 30, and 60 minutes. Then, Cu(OH)2 nanostructures are formed and dried at $180^{\circ}C$ for 2 h. With the drying process, the Cu(OH)2 nanostructure is transformed to CuO nanograss by dehydration reaction. CuO nanograss are grown randomly on Cu foil with the average length of 10 ${\mu}m$ and the average diameter of a 100 nm. CuO nanograsses are covered by Ag with various thicknesses from 10 to 30 nm using a thermal evaporator. Then, we immerse uncoated and Ag coated CuO nanowire samples of various oxidation times in a 0.001M methanol-based 4-mercaptopyridine (4-Mpy) in order to evaluate SERS enhancement. Raman shift and SERS enhancement are measured using a Raman spectrometer (Horiba, LabRAM ARAMIS Spectrometer) with the laser wavelength of 532 nm. Raman scattering is believed to be enhanced by the interaction between CuO nanograss and Ag island film. The gaps between Ag covered CuO nanograsses are diverse from <10 nm at the bottom to ~200 nm at the top of nanograsses. SERS signal are improved where the gaps are minimized to near 10s of nanometers. There are many spots that provide sufficiently narrow gap between the structures on randomly grown CuO nanograss surface. Then we may find optimal enhancement of Raman signal using the mapping data of average results. Fabrication of CuO nanograss based on a solution method is relatively simple and fast so this result can potentially provide a path toward cost effective fabrication of SERS substrate for sensing applications.

• 마이크로전자및패키징학회지
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• 제21권4호
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• pp.133-137
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• 2014

직경 수 마이크론급의 Ag 코팅 Cu 플레이크를 제조하기 위한 선행공정으로 습식 화학적 합성법으로 제조된 서브마이크론급의 Cu 입자를 볼 밀링 공정을 통해 프레이크화 하였다. 입자들의 산화 및 응집을 막기 위해 볼 밀링 유체로는 에틸렌글리콜을 사용하였고, 에틸아세테이트 표면개질제도 첨가하였다. 용기의 회전수에 따른 실험 결과를 통해 회전수에 따른 회전 모드의 변화가 밀링 후 Cu 입자들의 평균적인 형상과 형상 균일도를 크게 변화시킴을 확인할 수 있었다. 또한 첨가한 지르코니아 볼의 직경 역시 Cu 입자들의 플레이크화 균일도를 결정하는 대표 공정변수임을 확인할 수 있었다. 그 결과 다소간의 응집체를 포함한 서브마이크론급의 Cu 입자를 사용했음에도 불구하고, 회전수, 표면개질제 첨가량, 그리고 지르코니아 볼의 직경 등의 대표 공정변수들을 최적화한 볼 밀링 공정을 통해 분산성이 우수한 수 마이크론급의 Cu 플레이크를 성공적으로 제조할 수 있었다.

• 마이크로전자및패키징학회지
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• 제31권2호
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• pp.1-8
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• 2024

Bonding wires are composed of conductive metals of Au, Ag & Cu with excellent electrical conductivities for transmitting power and signals to wafer chips. Wire metals do not provide electrical insulation, adhesion promoter and corrosion passivation. Adhesion between metal wires is extremely weak, which is responsible for wire cut failures during thermal cycling. Organic coating for electrical insulation does not satisfy bondability and manufacturability, and it is complex to apply very thin organic coating on metal wires. Automotive packages require enhanced reliability of packages under harsh conditions. LED and power packages are susceptible to wire cut failures. Contrary to conventional OCB behaviors, forming gas was not required for free air ball formation for both Ag and Pd-coated Cu wires with Al₂O₃ passivation.

• 한국전기전자재료학회논문지
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• 제26권3호
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• pp.232-239
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• 2013

Thin light-active layers of the $CuInSe_2$ solar cell were prepared on Mo-coated sodalime glass substrates by one-step electrodeposition and post-annealing. The structure, morphology, and composition of $CuInSe_2$ film could be controlled by deposition parameters, such as the composition of metallic precursors, the concentration of complexing agents, and the temperature of post-annealing with elemental selenium. A dense and uniform Cu-poor $CuInSe_2$ film was successfully obtained in a range of parametric variation of electrodeposition with a constant voltage of -0.5 V vs. a Ag/AgCl reference electrode. The post-annealing of the film at high temperature above $500^{\circ}C$ induced crystallization of $CuInSe_2$ with well-developed grains. The KCN-treatment of the annealed $CuInSe_2$ films further induced Cu-poor $CuInSe_2$ films without secondary phases, such as $Cu_2Se$. The structure, morphology, and composition of $CuInSe_2$ films were compared with respect to the conditions of electrodeposition and post-annealing using SEM, XRD, Raman, AES and EDS analysis. And the conditions for preparing device-quality $CuInSe_2$ films by electrodeposition were proposed.

• 한국분말재료학회지
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• 제15권3호
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• pp.221-226
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• 2008

Silver coated copper composite powders were prepared by electroless plating method by controlling the activation and deposition process variables such as feeding rate of silver ions solution, concentration of reductant and molar ratio of activation solution $(NH_4OH/(NH_4)_2SO_4)$ at room temperature. The characteristics of the product were verified by using a scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic absorption (A.A.). It is noted that completely cleansing the copper oxide layers and protecting the copper particles surface from hydrolysis were important to obtain high quality Ag-Cu composite powders. The optimum conditions of Ag-Cu composite powder synthesis were $NH_4OH/(NH_4)_2SO_4$ molar ratio 4, concentration of reductant 15g/l and feeding rate of silver ions solution 2 ml/min.

• 마이크로전자및패키징학회지
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• 제19권1호
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• pp.47-53
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• 2012

무연 리플로우 공정 횟수에 따른 organic solderability preservative(OSP) 표면처리 두께변화 및 열화현상을 분석하였다. 무연솔더 접합부의 접합강도에 미치는 OSP 표면처리의 열화특성을 SnPb 표면처리 경우와 비교하여 조사하였다. 또한 리플로우 pass에 따른 무연솔더 접합강도 열화분석을 위해 OSP 및 SnPb 표면처리된 FR-4 재질 PCB를 각각 1-6회 리플로우 처리하였다. 이후 각 리플로우를 거친 PCB 위에 2012 칩 저항기를 실장한 후 접합강도 변화를 측정하였다. 그 결과, 리플로우 공정 중 열 노출에 의해 OSP 코팅두께가 감소되는 것이 관찰되었고, 코팅두께의 변화 및 OSP 코팅 층의 산화를 유발함으로써, 솔더의 젖음성이 감소될 수 있음을 확인할 수 있었다. OSP 열화에 따른 솔더 접합강도는 SnPb 표리처리시 평균 62.2 N 이였으며, OSP의 경우는 약 58.1 N 이였다. 리플로우 공정 노출에 따라 OSP 코팅 층은 열분해 되지만, 솔더 접합부의 접합강도 측면에서는 산업적으로 적용 가능성을 확인할 수 있었다.