• 한국레이저가공학회지
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• 제15권3호
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• pp.7-10
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• 2012

Dimensions (line/space) of circuits in IC substrates for high-end chips (e.g. CPU, etc.) are anticipated to decrease as small as $10{\mu}m/10{\mu}m$ in 2014. Since current etch-based circuit-patterning processes are not able to address the urgent requirement from industry, laser-based circuit patterning processes are under active research in which UV laser is used to engrave embedded circuits patterns into IC substrates. In this paper, we used a nanosecond UV laser to directly fabricate embedded circuit patterns into IC substrates with/without ceramic powders. In experiments, we engraved embedded circuit patterns with dimensions (width/depth) of abut $10{\mu}m/10{\mu}m$ and $6{\mu}m/6{\mu}m$ into the IC substrates. Due to the recoil pressure occurring during ablation, the circuit patterning of the IC substrates with ceramic powders showed the higher ablation rate.

• 수산해양기술연구
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• 제51권2호
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• pp.163-170
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• 2015

Recently LED fish-attracting lamps have been more widely used in fisheries as low-cost and high-efficiency fishing gear, and development of long-life high-efficiency lamps is required through the design of LED packages to optimize heat resistance. This study developed an improved LED fish-attracting lamp with excellent heat performance, which was verified using a numerical model. Heat-resistance design factors such as the heat-radiation fin shape, PCB type, and LED chip count were investigated and optimized. Comparison with a commercial 180-W LED fishing lamp showed that the increase in initial temperature was 40% higher than that of the surrounding LED chip because of design errors in contact thermal resistance. The 250-W LED lamp developed in this study has a characteristic with thermal rising in linearly stable according to the heat source. In addition, luminance efficiency was improved by 20-65% by using flow-visualization simulation. A decrease of 45% in total power consumption with a fuel-cost reduction of over 55% can be expected when using these optimized heat release design factors.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.179-180
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• 2012

Aluminum alloys are widely known as non-ferrous metal with light weight and high strength. Consequently, these materials take center stage in the aircraft and automobile industry. The Al7075 aluminum alloy is based on the Al-Zn-Mg-Cu and one of the strongest wrought aluminum alloys. Aluminum nitride has ten times higher thermal conductivity($319W/m{\cdot}K$) than Al2O3 and also has outstanding electric insulation($1{\times}1014{\Omega}{\cdot}cm$). Furthermore, it has high mechanical property (430 MPa) even though its co-efficient of thermal expansion is less than alumina For these reasons, it has great possibilities to be used for not only the field which needs high strength lightweight but also electronic material field because of its suitability to be applied to the insulator film of PCB or wafer of ceramic with high heat conduction. This paper investigates the mechanical properties and corrosion behavior of aluminum alloy Al7075 deposited with aluminum nitride thin films To improve the surface properties of Al7075 with respect to hardness, and resistance to corrosion, aluminum nitride thin films have been deposited by pulsed DC reactive magnetron sputtering. The pulsed DC power provides arc-free deposition of insulating films.

• 방사선산업학회지
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• 제9권3호
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• pp.137-141
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• 2015

A single-shot dual-energy x-ray imaging technique has been developed using a sandwich detector by stacking two detectors, in which the front and rear detectors respectively produce relatively lower and higher x-ray energy images. Each detector layer is composed of a phosphor screen coupled with a photodiode array. The front detector layer employs a thinner phosphor screen, whereas the rear detector layer employs a thicker phosphor screen considering the quantum efficiency for x-ray photons with higher energies. We have applied the proposed method into the inspection of printed circuit boards, and obtained dual-energy images with background clutter suppressed. In addition, the single-shot dual-energy method provides sharper-edge images than the conventional radiography because of the unsharp masking effect resulting from the use of different thickness phosphors between the two detector layers. It is promising to use the single-shot dual-energy x-ray imaging for high-resolution nondestructive testing. For the reliable use of the developed method, however, more quantitative analysis is further required in comparisons with the conventional method for various types of printed circuit boards.

• 마이크로전자및패키징학회지
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• 제28권2호
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• pp.65-70
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• 2021

본 연구에서는 레이저 접합 공정을 이용하여 flame retardant-4 (FR-4) 인쇄회로기판 (printed circuit board, PCB)의 organic solderability preservative (OSP) 표면처리 된 Cu pad와 전자부품을 Sn-57Bi-1Ag 저온 솔더 페이스트로 접합을 한 후 접합부의 계면 특성과 기계적 특성에 대하여 보고 하였다. 레이저 접합 공정은 레이저 파워 및 시간 등을 다르게 진행하여 접합 공정 조건이 접합부의 계면 및 기계적 특성에 미치는 영향을 살펴보았다. 레이저 접합 공정의 산업적 적용을 위하여 산업적으로 많이 이용되고 있는 리플로우 접합 공정을 이용한 접합부의 특성과도 비교 하였다. 레이저 접합 공정 적용 결과 2, 3 s의 짧은 공정 시간에도 계면에 Cu₆Sn₅ 금속간화합물 (intermetallic compound, IMC)를 생성하여 접합부를 안정적으로 형성함을 확인 하였다. 또한, 리플로우 공정과 비교해 보았을 때 레이저 접합 공정을 적용할 경우 접합부의 보이드 형성이 억제됨을 확인할 수 있었으며 접합부의 전단강도도 리플로우 공정 접합부보다 높은 기계적 강도를 나타냈다. 따라서, 레이저 접합 공정을 적용할 경우 짧은 접합 공정 시간에도 불구하고 안정적인 접합부 형성 및 높은 기계적 강도를 확보할 수 있는 것으로 기대된다.

• 한국전자통신학회논문지
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• 제10권5호
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• pp.615-622
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• 2015

반도체 제조기술의 발달로 고효율 및 고휘도의 LED가 개발됨에 따라 재래식 조명들로부터 LED를 이용한 조명으로 조명산업이 이동하는 추세이다. LED 조명등은 에너지 효율이 재래식 조명보다 뛰어나지만 많은 열이 발생한다는 단점이 있다. 특히 대형 LED 조명등에서는 이러한 발열문제가 심각한 실정으로, LED에 의한 메탈기판의 열은 납땜 부분을 열화시켜 조명등의 수명을 단축시키는 주된 원인이 된다. 따라서 대형 조명등을 개발하기 위해서는 이러한 열 문제를 해결하는 것이 매우 중요하다. 본 연구에서는 대형 LED 조명등에서 열문제를 해결하기 위한 방법을 제시하였고, 제시한 방식으로 1200W급 LED 조명등을 개발하였다. 본 연구에서 이용한 방법은 LED 조명등에 워터재킷을 설치하여 냉각수를 채웠으며, 소형의 수중펌프를 이용하여 냉각수를 순환시키는 방법을 이용하였다.

• Journal of Biosystems Engineering
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• 제43권2호
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• pp.94-102
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• 2018

Purpose: In this study, a maintenance free super-capacitor battery charging system based on the photovoltaic module, to be used in agricultural electric carriers, was developed and its charging characteristics were studied in detail. Methods: At first, the electric carrier system configuration is introduced and the electric control components are presented. The super-capacitor batteries and photovoltaic module used in the experiment are specified. Next, the developed charging system consisting of a constant current / constant voltage Buck converter as the charging device and a super-capacitor cell as a balancing device are initiated. The proposed circuit design, a developed PCB layout of each device and a proportional control to check the current and voltage during the charging process are outlined. An experiment was carried out using a developed prototype to clarify the effectiveness of the proposed system. A power analyzer was used to measure the current and voltage during charging to evaluate the efficiency of the energy storage device. Finally, the conclusions of this research are presented. Results: The experimental results show that the proposed system successfully controls the charging current and balances the battery voltage. The maximum voltage of the super-capacitor battery obtained by using the proposed battery charger is 16.2 V, and the maximum charging current is 20 A. It was found that the charging time was less than an hour through the duty ratio of 95% or more. Conclusions: The developed battery charging system was successfully implemented on the agricultural electric carriers.

• 한국환경과학회지
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• 제20권11호
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• pp.1499-1507
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• 2011

Practical disposal of transformer insulation oil laden with PCBs (polychlorinated biphenyls) by a chemical treatment has been studied in field work. The transformer insulation oil containing PCBs was treated by the required amounts of PEG (polyethylene glycol) and KOH, along with different reaction conditions such as temperatures and times. The reaction of PEG with PCBs under basic condition produces arylpolyglycols, the products of nucleophilic aromatic substitution. Removal efficiencies of PCBs in insulation oil before and after chemical treatment were examined. The removal efficiency of PCBs was very low at lower temperatures of 25 and $50^{\circ}C$. Under the reaction condition of PEG 600/KOH/$100^{\circ}C$/2hr, removal efficiency of PCBs was approximately 70%, showing completely removal of PCBs containing 7~9 chlorines on biphenyl frame which appear later than PCB IUPAC Number 183 (2,2',3,4,4',5',6-heptaCB) in retention time of GC/ECD. However, when increasing the reaction temperature and time to $150^{\circ}C$ and 4 hours, removal efficiency of PCBs reached 99.99% without any formation of PCDDS/PCDFs during the process. Such reaction conditions were verified by several official analytical institutions. In studying the reaction of PEG with PCBs, it confirmed that the process of chemical treatment led to less chlorinated PCBs through a stepwise process with the successive elimination of chlorines.

• 대한환경공학회지
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• 제31권3호
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• pp.208-216
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• 2009

본 연구에서는 토양 중 POPs 오염수준을 토지이용형태별로 구분 조사하여 오염특성을 규명하고 효율적인 토양 중 POPs 오염물질 관리방안 마련에 필요한 자료를 제공하였다. 농약류 중 Heptachlor, Aldrin, Endrin, Mirex, Toxaphene이 모든 지역에서 검출되지 않았고 Dieldrin은 N.D.-12.08 ${\mu}g$/kg, Chlordane은 N.D.-16.08 ${\mu}g$/kg, ${\Sigma}$DDT는 N.D.-38.19 ${\mu}g$/kg, HCB는 N.D.-1.32 ${\mu}g$/kg의 범위를 나타냈다. PCBs는 N.D.-172.12 ${\mu}g$/kg의 범위로 절연유오염지역이 높게 나타났으며, PCDD/Fs는 N.D.-6.68 pg I-TEQ/g으로 공단지역이 비교적 높게 나타났다.

• 마이크로전자및패키징학회지
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• 제26권3호
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• pp.63-69
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• 2019

전자부품에 대한 보드실장은 아직까지 솔더를 이용한 접합기술을 주로 이용하고 있다. 그러나, 솔더의 크? 및 피로특성으로 인한 접합부 내구한계로, 자동차 전장모듈에서는 반영구적인 접합기술인 프레스 핏(Press-fit) 접합기술 적용을 확대하고 있다. 프레스 핏 접합은 프레스 핏 금속단자를 보드내 쓰루 홀(Through hole)에 기계적으로 삽입하여 체결하는 접합기술로써, 적절한 금속단자의 소성변형으로 쓰루 홀 내부 표면접합을 밀착시킴으로써 강건한 접합을 유도한다. 본 논문에서는 보드내 쓰루 홀 크기 및 표면처리에 따른 프레스 핏 접합 특성 및 신뢰성을 솔더링과 함께 비교하기 위해, 보드 쓰루 홀 크기에 따른 삽입강도 및 삽발강도를 평가하였으며, 열충격 시험을 통한 실시간 저항변화를 통해 프레스 핏 및 솔더링 접합부의 저항변화를 관찰하였다. 또한, 각 접합부위 분석을 통한 프레스 핏 및 솔더링 접합열화를 분석하여 주요 파손모드를 고찰하고자 하였다.