• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05b
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• pp.164-169
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• 2005

A.T.S.의 스위칭 구조와 접점 환경은 주로 아크 전류, 접촉 저항, 아크 시간 등의 불리적 요인이 주로 마모와 특성에 영향을 미치게 된다. 사용되는 접점 재료는 W 또는 WC-Cu 계로 형상과 크기는 전형적인 반구형 구조의 접촉으로 구동이 이루어진다. 따라서 A.T.S.용 접점의 아크 마모 특성 시험을 위한 고려 요인은 이러한 점을 고려하여 시험과 분석이 이루어 졌다. 접점의 마모 특성 실험식으로부터 실제적인 관점에서 보면 제한된 수명을 나타내는 $n_L$을 보장하기 때문에 b<1의 경우가 가장 바람직한 결과로 ATS 접점 시편의 경우 $b{\fallingdotseq}0.99$로 안정된 접점 아크 마모 특성을 갖는 것으로 판단된다. 아크 전압에 대한 모델링과 실험에서 접점 간극 거리 1<0.1mm, 아크전류 i<100A의 시험 조건에 대해 검토한 결과 ATS 접점 시편의 아크전압은 $u_a=10.2V$로 계산되었다. 이 값은 설험적인 값과 상당히 접근하는 특성을 갖는 것으로 나타났으며, 아크에 의한 마모를 억제하기 위해 첨가하는 WC 또는 W의 복합 소결로 인해 아크 에너지가 감소되는 것을 보여준다. 한편 접점의 아크 동작이 분리되는 순간의 동작 시험에서 기존 W(50%wt)-Cu(50%wt) 접점의 값과 비교하면 분리시 아크 전압은 상대적으로 낮아지는 현상은 W강화 첨가량의 증가로 인한 아크 에너지 감소의 제한성을 나타내는 것으로 사료된다.

• Journal of Applied Reliability
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• v.13 no.2
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• pp.109-116
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• 2013

The solder is any of various fusible alloys, usually tin and lead, used to join metallic parts that provide the contact between the chip package and the printed circuit board. Solder plays an important role of electrical signals to communicate between the two components. In this study, two kinds of Ag-free solder as sample is made to conduct the thermal shock test and the high humidity temperature test. Low resistance is measured to estimate crack size of solder, using daisy chain. The low speed shear test is also performed to analyze strength of solder. The appropriate degradation model is estimated using the result data. Depending on the composition of solder, lifetime estimation is conducted by adopted degradation model. The lifetime estimated two kinds of Ag-free solder is compared with expected lifetime of Sn-Ag-Cu solder. The result is that both Ag-free composition are more reliable than Sn-Ag-Cu solder.

• Korean Journal of Materials Research
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• v.24 no.3
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• pp.123-128
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• 2014

To realize high-performance thin film solar cells, we prepared CIGS by the co-evaporation technique on both sodalime and Corning glass substrates. The structural and efficient properties were investigated by varying the thickness of the Mo:Na layer, where the total thickness of the back contact was fixed at 1${\mu}m$. As a result, when the Mo:Na thickness was 300 nm on soda-lime glass, the measured Na content was 0.28 %, the surface morphology was a plate-like compact structure, and the crystallinity by XRD showed a strong peak of (112) preferential orientation together with relatively intense (220) and (204) peaks as the secondary phases influenced crystal formation. In addition, the substrates on soda-lime glass effected the lowest surface roughness of 2.76 nm and the highest carrier density and short circuit current. Through the optimization of the Mo:Na layer, a solar conversion efficiency of 11.34% was achieved. When using the Corning glass, a rather low conversion efficiency of 9.59% was obtained. To determine the effects of the concentration of sodium and in order to develop a highefficiency solar cells, a very small amount of sodium was added to the soda lime glass substrate.

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.151-155
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• 2015

We fabricated the Cu Schottky contact on an n-type Ge wafer and investigated the forward bias current-voltage (I-V) characteristics in the temperature range of 100~300 K. The zero bias barrier height and ideality factor were determined based on the thermionic emission (TE) model. The barrier height increased and the ideality factor decreased with increasing temperature. Such temperature dependence of the barrier height and the ideality factor was associated with spatially inhomogeneous Schottky barriers. A notable deviation from the theoretical Richardson constant (140.0 Acm^-2K^-2 for n-Ge) on the conventional Richardson plot was alleviated by using the modified Richardson plot, which yielded the Richardson constant of 392.5 Acm^-2K^-2. Finally, we applied the theory of space-charge-limitedcurrent (SCLC) transport to the high forward bias region to find the density of localized defect states (N_t), which was determined to be 1.46 × 10¹² eV^-1cm^-3.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.271.1-271.1
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• 2013

Titania is usually used in sun-screens, tooth paste, and other daily used objects as a pigment. However, scientists have focused on titania as photocatalyst due to its excellent activities. By fabricating vanadium doped TiO2 and CuOx co-catalyzed TiO2 nano-size filter, the degradation level of the volatile organic compound (VOC) concentration was tested using 365nm UV LED as light source in a closed chamber. Main purpose for this test is to evaluate the activities of various catalysts for degrading the VOCs which are detrimental to human body and toluene and p-xylene were chosen in the VOC removal test. Target gas materials were injected into the test chamber with dry air as carrier gas which was flowed into the gas washer bottle filled with liquid form of VOC substance. When the VOC gas flows into the chamber, it is circulated by 200 mm fan in order to contact with the set-up filter on the aluminum holder. Target gas concentration in the chamber was monitored using VOC detector (miniRae3000, Raesystems) which was also placed inside the chamber. With the measured concentration, the VOC degradation efficiency and the degradation rate were evaluated and used to compare the catalytic activities.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.10
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• pp.1809-1816
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• 2000

The catalytic combustion of methanol as a model volatile organic compound(VOC) was been investigated over metal-phthalocyanine(PC) in a fixed bed flow reactor system. The catalytic activity of Co-PC pretreated with air and methanol mixture at $450^{\circ}C$ and 60 cc/min for 1 hr was very excellent. The order of catalytic activity on methanol combustion was summarized as follows: metal free-PC < Zn-PC < Fe-PC < Cu($\alpha$)-PC < Co-PC. By TG/DTA analysis, the tendency of thermal decomposition was increased as follows: metal free-PC < Zn-PC < Cu($\alpha$)-PC < Co-PC < Fe-PC. Under this pretreatment condition, the basic structures of Co-PC, Cu($\alpha$)-PC and Fe-PC were destroyed, and the new metal oxide such as $Co_3O_4$ from Co-PC was confirmed by EA and XRD analysis. But Zn-PC and metal free-PC were retained its basic structure under this pretreatment condition. On the combustion of methanol over Co-PC, HCHO and $HCOOCH_3$ were observed as an intermediate products in the high concentration of reactant or the short contact time(W/F).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.251-254
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• 2001

This paper describes an efficiency improvement of buried contact solar cell (BSCS) with a structure of MgF$_2$/CeO$_2$/Ag/Cu/Ni grid/n$^{+}$ emitter/p-type Si base/p$^{+}$/Al. Theoretical and experimental investigations were performed on a double layer antireflection (DLAR) coating of MgF$_2$/CeO$_2$. We investigated CeO$_2$ films as an AR layer because they have a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. An optimized DLAR coating shewed a reflectance as low as 2.04 % in the wavelengths ranged from 0.4 ${\mu}{\textrm}{m}$ to 1.1 ${\mu}{\textrm}{m}$. BCSC cell efficiency was improved from 16.2 % without any AR coating to 19.9 % by employing DLAR coatings. Further details on MgF$_2$/CeO$_2$ DLAR coatings on the BCSC cells are presented in this paper.per.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1080-1083
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• 2002

In this paper, we have studied with regard to the use of lasers for modifying the surface properties of silicon in order to improve it's wettability and adhesion characteristics. Using an Nd:YAG pulse laser, the wettability and adhesion characteristics of silicon surface have been developed by an Nd:YAG pulse laser. It was found that the laser treatment of silicon surfaces modified the surface energy. In the result of wetting experiments, by the sessile drop technique using the distilled water, wetting characteristic of silicon after the laser irradiation shows a decreased value of the contact angle. In case of the laser treated silicon surface, laser direct writing of copper lines has been achieved by pyrolytic decomposition of copper formate films$(Cu(HCOO)_2{\cdot}4H_2Q)$, using a focused $Ar^+$ laser beam$(\lambda=514.5nm)$ on the silicon substrates. The deposited patterns were measured by energy dispersive X-ray(EDX), Scanning Electron Microscopy(SEM) and surface profiler($\alpha$-step) to examine the cross section of deposited copper lines and linewidth.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1840-1842
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• 2003

This paper describes an experiment of detecting a temperature and components of arc plasma of electrical circuit breaker with a spectroscopic system. The system includes an optical fiber, a monochromator which has three gratings from low to high resolution and ICCD of which time resolution is 50 ns. This system enables measuring a temperature and components of arc plasma of a circuit breaker which is generated and extinguished in a few ms. We use a Planck's law and Boltzmann Plot method for calculating a temperature of arc plasma. A Xenon lamp is used for calibrating the system and this is very important for calculating a temperature of arc plasma. In this study, Arc plasma of Ag and Cu contact was investigated and these represent the contact of low voltage and extra-ultra high voltage circuit breaker, respectively. 8 $kA_{rms}$ test current was applied with a capacitor bank.

• Journal of Korea Foundry Society
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• v.25 no.3
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• pp.115-122
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• 2005

In the present study, an EMC (Electromagnetic Casting) process, using a segmented Cu cold crucible under a high frequency alternating magnetic field of 20 kHz, was practiced for the fabrication of poly-crystalline Si ingot of 50 mm diameter. The effects of Joule heating and electromagnetic pressure in molten Si were systematically investigated with various processing parameters such as electric current and crucible configuration. A preliminary experimental work was initiated with the pure Al system for the establishment of a stabilized non-contact working condition, and further adapted to the semiconductor-off-grade Si system. A commercialized software such as Opera-3D was utilized in order to simulate electromagnetic pressure and Joule heating. In order to evaluate the meniscus shape of the molten melts, shape parameter was used throughout the research. A segmented graphite crucible, which was attached at the upper part of the cold crucible, was introduced to enhance significantly the heating efficiency of Si melt keeping non-contact condition during continuous melting and casting processes.