• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.171-171
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• 2013

2층 FCCL (연성회로기판, Flexible Copper Clad Laminate)에 있어서 폴리이미드 필름과 구리의 접착력을 향상 시키기 위해 기존에 사용되고 있는 Ni-Cr대신 박리강도가 높고 에칭성도 매우 뛰어난 Ni-Mo-Nb 박막을 Roll-to roll 스퍼터 장비를 이용하여 개발하였다. 새롭게 개발된 Ni-Mo-Nb 박막은 기존 연구되어진 Ni-Cr 물질 대비 고온 박리강도 약 1.5~2.0배, 에칭성 8배 이상의 매우 우수한 특성을 보였다. Ni-Mo-Nb 접착층의 두께가 7~40 nm로 증가함에 따라 상온 박리강도가 향상 되는 것을 확인하였다. Ni-Mo-Nb 박막을 증착 하기 전 폴리이미드 기판표면을 RF 플라즈마 전처리 하였을 때 0.67 kg f/cm의 우수한 상온 박리강도를 나타내었으며 FCCL 샘플을 $150^{\circ}C$에서 168시간동안 열처리 한 후 접착력을 측정하였을 때도 0.54 kg f/cm의 높은 고온 박리강도를 보였다. FCCL의 박리강도, 표면 거칠기, 원소들의 화학적 결합, 박막의 미세구조를 peel test, atomic force microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy를 이용하여 폴리이미드 기판 플라즈마 전처리 효과를 확인하였다. 그 결과 플라즈마 전처리를 한 폴리이미드 기판의 경우 처리하지 않은 기판보다 상온과 고온에서 더 우수한 접착력을 가지는 것을 확인 할 수 있었는데 이것은 폴리이미드 기판의 표면 거칠기 증가에 의한 mechanical interlocking effect가 아닌 전처리를 통한 폴리이미드 표면 개질로 C-0, C-N와 같은 chemical functional group이 증가했기 때문인 것으로 확인되었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.9-18
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• 1999

The seismic over-strength factor Ω is evaluated for 4-story reinforced concrete buildings in Korea, which has low seismic intensity. For this study, the seismic load suggested in' Aseismic guideline research- phase ll' (in Korea) is used. When 3D study-models are designed, span length and bay number are varied and accidental torsional moment is considered. And the models are analyzed by push-over analysis, in which external and internal frame are connected by rigid-link. As a result of numerical experiments, Ω is increased as the bay number or span length is increased. Because, by the including of accidental torsional moment in designing process, the increased ratio of strength of external columns is larger than the increased ratio of span length or bay number. And this makes the failure mode of model closer or strong-column and weak-beam mechanism.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.429-437
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• 2008

In this study the progressive collapse potential of braced frames were investigated using the nonlinear static and dynamic analyses. All of nine different brace types were considered along with a special moment-resisting frame for comparison. According to the pushdown analysis results, most braced frames designed per current design codes satisfied the design guidelines for progressive collapse initiated by loss of a first story mid-column; however most model structures showed brittle failure mode. This was caused by buckling of columns after compressive braces buckled. Among the braced frames considered, the inverted- V type braced frames showed superior ductile behavior during progressive collapse. The nonlinear dynamic analysis results showed that all the braced frame model structures remained in stable condition after sudden removal of a column, and their deflections were less than that of the moment-resisting frame.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.111-119
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• 2010

Many researchers have studied on the optimal seismic design with the development of the computer. So far the application structure of most researches on the optimal seismic design was almost the moment resisting frame. Because the braced frames are the representative lateral load resisting system with the moment resisting frames, it is estimated that the effect on the practice will be great if it can is provided a design guideline through the development of optimal seismic design model for the braced frames. The purpose of this study is to propose the optimal seismic design model for the inverted V-type special concentrically braced frames considering the buckling of braces. The objective functions of this are to minimize the structural weight and maximize the total dissipated energy of the structure and the constraints of this are the strength conditions for the column, beam, brace and inter-story drifts condition. To verify the proposed model, it is applied to 2D steel concentrically braced frames of 3-story and 9-story.

• Polymer(Korea)
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• v.27 no.1
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• pp.52-60
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• 2003

In this work, two types of Ni-plating, namely electrolytical and electroless Ni-platings on carbon fiber surfaces, were carried out to enhance the impact resistance of composites. And the comparison between electrolytical and electroless methods on their impact properties of composite system was studied. The surface properties of carbon fibers were characterized using XRD, SEM, and contact angle measurements. The impact behaviors were investigated using an Izod type impact tester. As experimental results, it was observed that electrolessly plated Ni layers had Ni-P alloys on carbon fiber surfaces as revealed by XRD, and electrolytically Ni-plated carbon fibers showed higher surface free energies than those of the electrolessly Ni-plated carbon fibers. In particular, the impact strengths of electrolessly Ni-plated carbon fibers-reinforced plastics were strongly increased. These results were probably due to the difference of wettabilities according to the different types of Ni-plating methods.

• Polymer(Korea)
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• v.33 no.6
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• pp.525-529
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• 2009

In order to manufacture 2-layer flexible copper clad laminate (FCCL) s having the excellent performance high adhesion properties between copper foil and polyimide film are required. Silane coupling agents with specific functional groups as an adhesion promoter are generally used to enhance the adhesion. In our study, we synthesized a novel silane coupling agent for increasing the adhesive property between copper layer and polyimide layer. The surface morphology of rolled copper foil, as a function of the concentrations of the coated silane coupling agent, was fully characterized. As fabricated 2-layer FCCL, we observed that adhesive properties were changed by the surface morphology and we confirmed that the novel silane coupling agent affects adhesive properties in FCCL with two types of poly (amic acid)s.

• Land and Housing Review
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• v.3 no.2
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• pp.195-202
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• 2012

This paper summarizes the seismic performance of two shear walls with different reinforcement details in boundary elements. One is a special shear wall designed by KBC2009 and the other is a shear wall with improved reinforcement details in boundary elements, which is a newly proposed type of special shear wall. Experimental tests under cyclic reversed loading were carried out with two 2/3 scale shear walls which were modelled from the lower part of seismic-resisting shear wall in 22-stories wall-slab apartment building. The experimental results show that seismic performance of shear wall with improved reinforcement details was almost similar to that of special shear wall with respect to the moment-drift ratio. However, energy dissipation capacity and ductility were slightly different. Also, shear wall with improved reinforcement details in boundary elements satisfied the inter-story drift limit of 1.5% from KBC2009.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.4
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• pp.521-528
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• 2021

In this study, to repair damaged economizer fin tubes on ships, sealing treatment was performed after applying arc thermal spray coating technology using Inconel 625. A solid particle erosion (SPE) experiment was conducted according to ASTM G76-05 to evaluate the durability of the substrate, thermal spray coating (TSC), and thermal spray coating+sealing treatment (TSC+Sealing) specimens. The surface damage shape was observed using a scanning electron microscope and 3D laser microscope, and the durability was evaluated through the weight loss and surface roughness analysis. Consequently, the durability of the substrate was superior to that of TSC and TSC+Sealing, which was believed to be owing to numerous pore defects in the TSC layer. In addition, the mechanism of solid particle erosion damage was accompanied by plastic deformation and fatigue, which were the characteristics of ductile materials in the case of the substrate, and the tendency of brittle fracture in the case of TSC and TSC+Sealing was confirmed.

• Journal of the Korean Geotechnical Society
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• v.25 no.5
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• pp.39-46
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• 2009

In this study, behavior of a rigid continuous wall, earth pressure distribution with construction stage, and axial force of earth anchors were evaluated based on field monitoring data and numerical analysis results. For this purpose, a construction site excavated using the diaphragm wall was selected and full instrumentation system was introduced. From monitoring results, it was found that the values of horizontal displacement of the wall measured from the inclinometers, which were installed within the diaphragm wall were similar to analytical value. The earth pressure increased with excavation progress due to jacking force of the ground anchors installed in previous excavation stages. When the excavation depth reached 60% of the final depth, observed earth pressure distribution was similar to that estimated from Peck's apparent earth pressure distribution. When the excavation depth was around 90% of the final depth, values of observed earth pressure showed middle values between those of Peck's and Tschebotarioffs apparent earth pressures. It was also observed that, when excavation depth is deep, values of the earth pressures from the rigid wall were similar to those estimated from conventional earth pressure distribution shape proposed for flexible walls.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.1 s.34
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• pp.41-46
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• 2005

A systematic investigation of shear testing was conducted to find a relationship between Ni-Sn intermetallic spatting and the brittle fracture observed in electroless Ni(P)/solder interconnection. Brittle fracture was found in the solder joints made of Sn-3.5Ag, while only ductile fracture was observed in a Cu-containing solder (Sn-3.0Ag-0.5Cu). For Sn-3.0Ag-0.5Cu joints, $(Ni,Cu)_3Sn_4$ and/or $(Cu,Ni)_6Sn_5$ compound were formed at the interface without spatting from the Ni(P) film. For Sn-3.5Ag, $Ni_3Sn_4$ compound was formed and brittle fracture occurred in solder pads where $Ni_3Sn_4$ had spalled. From the analysis of fractured surfaces, it was found that the brittle fracture occurs through the $Ni_3SnP$ layer formed between $Ni_3Sn_4$ intermetallic layer and the Ni(P) film. Since the $Ni_3SnP$ layer is getting thicker during/ after $Ni_3Sn_4$ spatting, suppression of $Ni_3Sn_4$ spatting is crucial to ensure the reliability of Ni(P)/solder system.