• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.125.1-125.1
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• 2011

빛 에너지를 전기에너지로 변환하는 발전소자인 태양전지는 청정 재생 에너지원으로 최근 Si 박막 태양전지의 고 효율화를 위해 여러 기술적인 면에서 개발되어지고 있다. 현재 박막형 태양전지는 실리콘계가 주류를 이루고 있으며, 유리 혹은 유연성기판(금속 or 고분자)에 비정질 실리콘 박막을 형성시킨 태양전지와 실리콘웨이퍼의 양면에 태양전지를 형성함으로써 효율을 극대화시킨 이종접합태양전지 등이 연구되고 있다. 특히 flexible 태양전지는 hard 기판에 비해 비교적 저가인 플라스틱 필름과 금속 foil을 기판으로 이용함으로서 저가화가 용이하며, 가볍고 유연성을 갖추고 있어 휴대와 시공에 있어 매우 우수한 장점을 가지고 있다. 본 연구에서는 flexible 기판(stainless steel)을 이용하여 태양전지 내 반사막 층이 미치는 영향을 알아보기 위하여 AZO/Ag 이중구조 박막의 특성을 연구하였다. RF magnetron sputtering system을 이용하였으며, 상온에서 Ag/AZO 이중구조 박막을 제조하였다. stainless steel 기판 위에 Ag층을 25nm 두께로 증착하였으며 연속공정으로 AZO 박막을 100~500nm의 두께경사를 가지도록 성장시켰다. 이 때의 AZO/Ag 이중구조 박막의 표면 morphology는 AFM 분석결과 7nm~3nm의 값을 나타내었으며, AZO 박막의 두께가 증가할수록 rms 값이 감소하는 경향을 보여주었다. 본 발표에서는 flexible 기판 상에 성장된 AZO/Ag 이중구조 박막의 전기적, 광학적 특성 등에 관하여 추가적으로 토론한 후 태양전지 효율 중 흡수층 내 반사막 층이 미치는 역할을 알아보겠다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.726-729
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• 2010

Copper Pillar Tin Bump (CPTB) was investigated for high density chip interconnect technology development, which was prepared by electroplating and electro-less plating methods. Copper pillar tin bumps that have $100{\mu}m$ pitch were introduced with fabrication process using a KM-1250 dry film photoresist (DFR), with copper electroplating for Copper Pillar Bump (CPB) formation firstly, and then tin electro-less plating on it for control oxidation. Electric resistivity and mechanical shear strength measurements were introduced to characterize the oxidation effects and bonding process as a function of thermo-compression. Electrical resistivity increased with increasing oxidation thickness, and shear strength had maximum value with $330^{\circ}C$ and 500 N thermo-compression process. Through the simulation work, it was proved that when the CPTB decreased in its size, it was largely affected by the copper oxidation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.55-55
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• 2008

압전폴리머 PVDF(polyvinylidene difluoride)의 기판소재를 기반으로 한 디스플레이 소자를 연구하였다. 압전 폴리머 PVDF의 양면은 두께 300nm정도의 ITO(Indium Tin Oxide)를 TCO(Transparent conducting oxide)로 R2R(roll to roll)증착하였으며, 이를 적외선 계열 Pulsed Laser로 상온 건식 에칭을 통해 패턴해내고, 이후 고진공 환경에서 Alq3 를 기반의 유기발광소자를 제작하였다. 전기적 신호에 대해서 기계적인 작동이 가능한 투명 압전 폴리머 재료를 디스플레이 발광소자의 기판 소재로 사용함으로써, 궁극적으로 발광기능과 더불어 압전효과에 의한 스피커 기능이 한 개의 개체내에서 독립적으로 구현될 수 있도록 설계하고, 기술적으로 실현시켰다는 점이 본 연구의 의의라고 할 수 있다. 이를 위해서, 섭씨 80도 이상의 온도에서 압전 성질을 상실하는 것으로 알려진 PVDF에 대해서 투명산화전극을 레이져를 이용한 비가열식 승화방법을 통해 패턴화하는 것을 사용했으며, 밀리미터 단위에서 수십 마이크로미터 수준까지 패턴화할 수 있었다. 제작된 복합형 유연 OLED소자는 기계적으로 휘어진 상태에서도 발광 성능과 스피커 성능을 각각 독립적으로 보였으며, Alq3에 의한 녹색발광을 보임을 확인하였고, 이 경우 양자효율은 약 3%이하의 값을 보였다. 또한 각주파수별 음압(SPL: Sound Pressure Level)측정 결과는 압번폴리머가 가청주파수 영역에서 작동함을 보였으며, 고주파영역에서의 SPL값이 증가하는 전형적인 PVDF사용 필름 스피커의 특성을 보였다. 이로부터 제작된 복합형 소자는 본 연구에서 제안된 목적에서 보인 것과 같이, 두 개의 기능이 서로간의 간섭없이 독립적으로 한 개의 개체 내에서 작동함을 확인할 수 있었다. 본 연구 결과로부터 새로운 유연 전자 소자에 대한 디자인 개념을 제시하고, 기타 다른 기능이 접합된 형태의 신개념 전자 소자를 제안하는 것도 가능할 것으로 기대된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.3
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• pp.204-211
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• 2007

Experiments were conducted to investigate the failure and strengths of carbon composite-to-aluminum single-lap bonded joints with 5 different bonding lengths. Joint specimens were fabricated to have secondary bonding of laminate and aluminum with a film type adhesive, FM73m. Tested joints have the bonding strengths between the values of aluminum-to-aluminum joints and composite-to-composite joints. In the joints with bonding length-to-width ratio smaller than 1, the strength decreases as the bonding length increases. In the joints with the ratio larger than 1, however, the strength converges to a constant value. Final failure mode of all the specimens was delamination. To use the maximum strength of the adhesive, it is important to design the joint to have strong resistance to delamination.

• Journal of the Korean institute of surface engineering
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• v.46 no.1
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• pp.9-15
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• 2013

The effect of the additionally applied electrical current on the adhesion strength between electroless Cu and polyimide films was investigated. Peel tests were performed after applying electrical current within the range from 0.1 to 100 mA for the duration from 1 to 30 minutes. Sample with more than 1 mA of additional electrical current for 1 minute showed higher adhesion strength than that without additional electrical current. However, samples with 10 mA of additional electrical current for more than 10 miniutes showed the degradation of adhesion strength. Ra and RMS values of the peeled polyimide surface were proportional to the adhesion strength though there were no significant changes in the morphology of the peeled surfaces with varied amount and time-length of additional electrical current. Applying electrical current could increase the density of chemical bonding, which results in increase of the adhesion strength between copper and polyimide. However, in the case of applying additional electrical current for excessive amount or time, the degradation of the adhesion strength owing to the formation of copper oxide at the interface could occur.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.338-339
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• 2008

현재 PCB (Printed circuit board) 산업은 디스플레이, 모바일 시장의 수요 증가로 인해 활성화 되면서 다앙한 분야로 확대 되어가고 있다. 전자기기의 직접화, 고속파, 사용 주파수 영역의 증가로 인해 수십 GHz 영역에서도 활용이 가능한 소재 및 기판의 필요성이 대두되어 지고 있어 이에 대응할 수 있는 소재 개발도 다양해지고 있다. 본 논문에서는 GHz 영역에서 인쇄회로기판의 회로형태가 특성에 미치는 영향에 대해 연구하였다. 이를위해 패턴도금법과 에칭법으로 회로를 형성하였다. 패턴도금법으로 형성된 시편은 무전해 구리도금 공정을 거친 후 감광성 필름을 이용하여 전해 도금방법을 패턴을 형성하여 회로를 구현하였고, 에칭 패턴 시편은 FR4를 이용하여 동박접합과 도금 공정 후 마스크 패턴을 사용하여 노광, 현상, 에칭 공정을 거쳐 회로를 구성하였다. GHz영역에서 Transmission Line 특성을 분석하였으며 구리 패턴과 절연체사이의 계면형태가 특성에 영향을 주는 것을 확인할 수 있었다.

• Polymer(Korea)
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• v.36 no.4
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• pp.434-439
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• 2012

To improve the performance of ionic polymer-metal composite (IPMC) actuators, Nafion films sandwiched with Nafion/conducting nanoparticulate electrospun webs were used as polymer electrolytes of IPMC. Multiwalled carbon nanotube (MWNT) and silver were the conducting nanoparticulates and the nanoparticles dispersed in a Nafion solution were electrospun. IPMCs with the Nafion/conducting nanoparticulate electrospun webs displayed improved displacements, response rates, and blocking forces. MWNT was superior to silver in terms of displacement and blocking force, and the webs without the conducting fillers also caused enhanced performances compared with the conventional IPMCs. These improvements were attributed to an elevated electrolyte flux through highly porous interlayers and capacitance induced by well dispersed conducting fillers, and low interfacial resistance between electrolyte and electrodes.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.371-378
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• 2021

The formation of hydrophilic surface based on polymers has received great attention due to the anti-adhesion of bacteria on solid substrates. Anti-adhesion coatings are aimed at suppressing the initial step of biofilm formation via non-cytotoxic mechanisms, and surfaces applied hydrophilic or ionic polymers showed the anti-adhesion effect for bioentities, such as proteins and bacteria. This is attributed to the formation of surface barrier from hydration layers, repulsions and osmotic stresses from polymer brushes, and electrostatic interactions between ionic polymers and cell surfaces. The antifouling polymer coating is usually fabricated by the grafting method through the bonding with functional groups on surfaces and the deposition method utilizing biomimetic anchors. This mini-review is a summary of representative antifouling polymers, coating strategies, and antibacterial efficacy. Furthermore, we will discuss consideration on the large area surface coating for application to public facilities and industry.

• Composites Research
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• v.19 no.4
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• pp.23-30
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• 2006

In the development of a cryogenic propellant tank, the proper selection of adhesives to bond composite and metal liner is important for the safety of operation. In this study, 3 types of adhesives were tested for the ability to bond CFRP composites developed for cryogenic use and aluminum alloy (Al 6061-T6) for lining the tank using double-lap joint specimens. The double-lap joint specimens were tested inside an environmental chamber at room temperature and cryogenic temperature ($-150^{\circ}C$) respectively to compare the bond strength of each adhesive and fracture characteristics. The material properties with temperature of component materials of double-lap joints were measured. In addition, ABAQUS was used for the purpose of analyzing the experimental results.

• Polymer(Korea)
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• v.36 no.4
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• pp.413-419
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• 2012

Multi-functional urethane acrylate monomers as the curing agent of poly(phenylene ether) (PPE) were synthesized and then the urethane bond formation was checked by FTIR spectrometry and NMR analysis. The synthesized monomers were mixed with PPE and fabricated to dielectric substrates. After forming PPE/monomer composite sheets by a film coater, several sheets were laminated to a test substrate in a vacuum laminator and then its properties depending on the type and the amount of monomers, such as dielectric constant, dielectric loss, and peel strength, were measured. Between the two different hydroxyl acrylates, when the monomer synthesized with 2-hydroxy-3-phenoxypropyl acrylate containing a phenyl group was used as a curing agent, a smaller dielectric loss was obtained and the dielectric constant and loss decreased with a decrease in the amount of the monomer. The peel strength values of the test substrates, however, did not show any specific difference between the cases of two synthesized monomers. As a result, it was obtained the polymer substrate for high frequency application having peel strength of about 10 N, low dielectric constant of 2.54, and low dielectric loss of 0.0027 at 1 GHz.