• The Journal of Information Technology
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• v.7 no.1
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• pp.155-161
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• 2004

During normal machine operation, partial discharge(PD) measurements were performed with turbine generator analyzer(TGA) in imitation stator winding of high voltage motors. The motor was energized to 4.47kV, 6.67, respectively. Applied voltage to Imitation winding was used two voltage level, 4.47[kV] and 6.67[kV]. Motors having imitation stator winding were installed with 80pF capacitive couplers at the terminal box. Case of PD Pattern regarding applied voltage phase angel, the PD patterns were displayed two dimensional and three dimensional. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). As the result, we could discrimidate using TGA the difference of internal and surface discharge for imitation stator winding. We have used the other technique, in order to feature extraction of faulty signals on stator winding, Daubechies Discrete wavelet transform and Harmonics analysis(FFT) about faulty signals.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.2 s.31
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• pp.23-28
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• 2004

We utilized Ag capping layer for fluxless bonding. To investigate the effect of Ag capping layer, two sets of sample were used. One set was bare In and Sn solders. The other set was In and Sn solders with Ag capping layer. In ($10{\mu}m$) and Sn ($10{\mu}m$) solders were deposited on Cu/Ti/Si substrate using thermal-evaporation, and Ag ($0.1{\mu}m$) capping layers were deposited on In and Sn solders. Solder joints were made by joining two In and Sn deposited specimens at $130^{\circ}C$ for 30 s under 0.8, 1.6, 3.2 MPa using thermal compression bonder. The contact resistance was measured using four-point probe method. The shear strength of the solder joints was measured by the shear test of cross-bar sample in the direction. The microstructure of the solder joints was characterized with SEM and EDS. In and Sn solders without Ag capping layers were only bonded at $130^{\circ}C$ under high bonding pressure. Also the shear strength of the In-Sn solder joints under was lower than that of the Ag/In-Ag/Sn solder joints. The resistance of the solder joints was $2-4\;m{\Omega}$ The solder joints consisted of In-rich phase and Sn-rich phase and the intermixed compounds were found at the interface. As bonding pressure increased, the intermixed compounds formed more.

• Korean Journal of Materials Research
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• v.7 no.10
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• pp.877-883
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• 1997

Ar 및 Ar과 $N_{2}$ 분위기하에서 rf 마그네트론 스퍼터링방법으로 Ta-AI과 Ta-AI-N합금막을 제조하였다. Ta-7.9at.% AI계열, Ta-26.7 at% AI게열과 Ta-45.4at.%AI계열에 Ar에 대한 질서유량비로 26%까지 질소를 첨가하여 Ta-AI-N박막을 증착한후, 300-$600^{\circ}C$온도 구산에서 열처리 전후의 구조 및 전기적 특성과 열적안정성을 통하여 레지스터의 적용가능성을 조사하였다. 구조 및 조성 분석은 X-선 회절과 Rutherford Backscattering Spectrometry(RBS)로 관찰하였고 열적안정성은 4단자법(four point probe method)을 이용한 저항변화를 통하여 측정하였다. 순수 Ta에 AI을 첨가하면 확장된 $\beta$($\beta$-Ta)N 합금박막에서 가장 열적안정성이 우수하게 나타났던 질소첨가 범위는 Ta $N_{hcp}$또는 TaN/ sub fcc/또는 Ta $N_{fcc}$와 비정질과의 혼합상순으로 상천이를 나타내었다. Ta-AI-N 합금박막에서 가장 열적안정성이 우수하게 나타났던 질서첨가 범위는 Ta-26.7at. % AI계열의 경우 19-36at.% $N_{2}$구간이었고, Ta-45.5at.% AI계열의 경우는 30-45at.%구간이었다. Ta-AI합금박막은 질소가 첨가되지 않아도 열처리 온도 및 시간에 따라 약 10% 이내의 비교적 작은 저항변화를 보여 열적안정성이 우수하지만 질소를 첨가하여 Ta-AI-N합금박막을 형성시킬경우, 증착된 상태에서 이미 큰 비저항을 나타내었고 열처리 동안 3%이내의 매우 작은 저항변화를 나타내었기 때문에 레지스터용 재료로써 열적안정성에 대한 잠재력이 크다.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.189-195
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• 2001

We prepared TMR junctions of NiFe(170 )/CoFe(48 )/Al(13 )-O/CoFe(500 )/Ta(50 ) structure on 2.5$\times$2.5 $\textrm{cm}^2$ area Si/SiO$_2$ substrates in order to investigate the uniformity of magnetoresistance(MR) value using a ICP magnetron sputter. Each layer was deposited by the ICP magnetron sputter and tunnel barrier was formed by the plasma oxidation method. We measured MR ratio and resistance of TMR devices with four-terminal probe system by applying external magnetic field. Although we used ICP sputter which is known as superior to make uniform films, the standard variation of MR ratio was 2.72. The variation was not dependent on the TMR devices location of a substrate. We found that MR ratio and spin-flip field (H's) increased as the resistance increased, which may be caused by local interface irregularity of the insulating layer. The variation of resistance value was 64.19 and MR ratio was 2.72, respectively. Our results imply that to improve the insulating layer fabrication process including annealing process to lessen interface modulation in order to mass produce the TMR devices.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.33-38
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• 2007

We studied a bonding at low temperature using polymer bump and Non-Conductive Adhesive (NCA), and studied the reliability of the polymer bump/Al pad joints. The polymer bumps were formed on oxidized Si substrates by photolithography process, and the thin film metals were formed on the polymer bumps using DC magnetron sputtering. The substrate used was AL metallized glass. The polymer bump and Al metallized glass substrates were joined together at $80^{\circ}C$ under various pressure. Two NCAs were applied during joining. Thermal cycling test ($0^{\circ}C-55^{\circ}C$, cycle/30 min) was carried out up to 2000 cycles to evaluate the reliability of the joints. The bondability was evaluated by measuring the contact resistance of the joints through the four point probe method, and the joints were observed by Scanning Electron Microscope (SEM). The contact resistance of the joints was $70-90m{\Omega}$ before the reliability test. The joints of the polymer bump/Al pad were damaged by NCA filler particles under pressure above 200 MPa. After reliability test, some joints were electrically failed since thinner metal layers deposited at the edge of bumps were disconnected.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.158-158
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• 2008

모바일 정보통신기기를 중심으로 실장모듈의 초소형화, 고집적화로 인해 접속단자의 피치가 점점 미세화 됨에 따라 플립칩 본딩용 접착제에 함유되는 무기충전제인 실리카 필러의 크기도 미세화되고 있다. 본 연구에서는 NCP (non-conductive paste)의 실리카 필러의 크기가 COB(chip-on-board) 플립칩 패키지의 신뢰성에 미치는 영향을 조사하였다. 실험에 사용된 실리카 필러는 Fused silica 3 종과 Fumed silica 3종이며 response surface 실험계획법에 따라 혼합하여 최적의 혼합비를 정하였다. 테스트베드로 사용된 실리콘 다이는 투께 $700{\mu}m$, 면적 5.2$\times$7.2mm로 $50\times50{\mu}m$ 크기의 Au 도금범프를 $100{\mu}m$ 피치, peripheral 방식으로 형성시켰으며, 기판은 패드를 Sn으로 finish 하였다. 기판을 플라즈마 전처리 후 Panasonic FCB-3 플립칩 본더를 이용하여 플립칩 본딩을 수행하였다. 패키지의 신뢰성 평가를 위해 $-40^{\circ}C{\sim}80^{\circ}C$의 열충격시험과 $85^{\circ}C$/85%R.H.의 고온고습시험을 수행하였으며 Die shear를 통한 접합 강도와 4-point probe를 통한 접속저항을 측정하였다.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1135-1141
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• 2008

The $La_{1-x}(Ca\;or\;Sr)xCrO_3$(x=0 and 0.25) interconnect materials for high temperature electrolysis of steam were investigated in views of sinterability and electrical conductivity. $LaCrO_3$, $La_{0.75}Ca_{0.25}CrO_3$ (LCC), and $La_{0.75}Sr_{0.25}CrO_3$ (LSC) powders were synthesized by coprecipitation method. Crystal structure was confirmed by X-ray diffraction (XRD). The sintering characteristics were analyzed by relative density and scanning electron microscopy. The electrical conductivity was measured by a DC four probe method. From the analyses of relative densities, it was found that the doped $LaCrO_3$ showed better sinterability than $LaCrO_3$ and the those sinterability increased with decrease of those particle sizes. The XRD results at different sintering temperatures for LCC and LSC revealed that the sinterability is closely related to the second phase transformation, that is, the second phase melting above $1,300^{\circ}C$ for LCC and $1,400^{\circ}C$ for LSC significantly promotes the sinterability. In case of electrical conductivities of LCC and LSC, which had a similar relative density, LCC showed better electrical conductivity than LSC.

• Journal of the Korean Magnetics Society
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• v.25 no.4
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• pp.117-122
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• 2015

The holes with a diameter of $35{\mu}m$ inside the GMR-SV (giant magnetoresistance-spin valve) film were patterned by using the photolithography process and ECR (electron cyclotron resonance) Ar-ion milling. From the magnetoresistance curves of the GMR-SV film with holes measuring by 4-electrode method, the MR (magnetoresistance ratio) and MS (magnetic sensitivity) are almost same as the values of initial states. On other side hand, the $H_{ex}$ (exchange bias coupling field) and $H_c$ (coercivity) dominantly increased from 120 Oe and 10 Oe to 190 Oe and 41 Oe as increment of the number of holes inside GMR-SV film respectively. These results were shown to be attributed to major effect of EMD (easy magnetic domian) having a region positioned between two holes perpendicular to the sensing current. On the basis of this study, the fabrication of GMR-SV applying to the hole formation improved the magnetoresistance properties having the thermal stability and durability of bio-device.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.672-678
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• 2011

In this work, carbon fibers were electrolessly Ni-plated in order to investigate the effect of metal plating on the electromagnetic shielding effectiveness (EMI-SE) of Ni-coated carbon fibers-reinforced epoxy matrix composites. The surfaces of carbon fibers were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Electric resistance of the composites was tested using a 4-point-probe electric resistivity tester. The EMI-SE of the composites was evaluated by means of the reflection and adsorption methods. From the results, it was found that the EMI-SE of the composites enhanced with increasing Ni plating time and content. In high frequency region, the EMI-SE didn't show further increasing with high Ni content (Ni-CF 10 min) compared to the Ni-CF 5 min sample. In conclusion, Ni content on the carbon fibers can be a key factor to determine the EMI-SE of the composites, but there can be an optimized metal content at a specific electromagnetic frequency region in this system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.105-112
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• 2018

This paper proposes a method for fabricating heatable glass using the conduction characteristics of metal thin films deposited on the surface of Low-e(Low emissivity) glass. The heating value of Low-e glass depends on the Joule heat caused by Low-e glass sheet resistance. Hence, its prediction and design are possible by measuring the sheet resistance of the material. In this study, silver electrodes were placed at 50 mm intervals on a soft Low-e glass sample with a low emissivity layer of 11 nm. This study measured the sheet resistance using a 4-point probe, predicted the power consumption and heating value of the Low-e glass, and confirmed the heating performance through fabrication and experience. There are two conventional methods for manufacturing heatable glass. One is a method of inserting nichrome heating wire into normal glass, and the other is a method of depositing a conductive transparent thin film on normal glass. The method of inserting nichrome heating wire is excellent in terms of the heating performance, but it damages the transparency of the glass. The method for depositing a conductive transparent thin film is good in terms of transparency, but its practicality is low because of its complicated process. This paper proposes a method for manufacturing heatable glass with the desired heating performance using Low-e glass, which is used mainly to improve the insulation performance of a building. That is by emitting a laser beam to the conductive metal film coated on the entire surface of the Low-e glass. The proposed method is superior in terms of transparency to the conventional method of inserting nichrome heating wire, and the manufacturing process is simpler than the method of depositing a conductive transparent thin film. In addition, the heat characteristics were compared according to the patterning of the surface thin film of the Low-e glass by an emitting laser and the laser output conditions suitable for Low-e glass.