• 한국정밀공학회지
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• 제29권1호
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• pp.41-47
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• 2012

The LDS(Laser Direct Structuring) is one of the new direct writing methods to fabricate conductive patterns by energy beam. It uses thermoplastic polymers with an additive compound that serves as plating seed after the activation by laser. The advantages of LDS include the miniaturization of electrical components, design flexibility, and a reduced number of production steps. The purpose of this study is to investigate the fundamental mechanism for LDS and the characteristics of conductive patterns by laser parameters. These results were studied by SEM, EDX, and XPS analysis. We have used a 20W pulse-modulated fiber laser and copper electroless plating to fabricate conductive patterns on polymer. The result showed that electroless copper plating seed caused the laser cracking of additive compound. In particular, the additive compound contained in copper metal oxides atoms will be changed to copper metal elements. Also, the characteristics of conductive patterns were dependent on laser parameter, especially laser fluence.

• 전기전자학회논문지
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• 제10권1호
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• pp.22-29
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• 2006

본 논문에서는 마이크로프로세서와 주변블록 사이에서 SDRAM을 사용함에 있어서 DMA(Direct Memory Access)에 의한 효율적인 SDRAM 접근방식을 제시하고 있다. 여기에서 마이크로프로세서는 AMBA 버스를 통해서 SDRAM에 접근을 하고 DMA는 DMA 전용 버스를 통해서 SDRAM에 접근한다. 마이크로프로세서가 SDRAM에 접근하지 않고 다른 레지스터에 접근하거나, 아니면 마이크로프로세서 캐쉬에서 히트(hit)신호가 발생하여 SDRAM에 접근할 필요가 없을 때에 주변 블록에서는 DMA를 통해서 SDRAM에 접근하여 데이타를 읽거나 쓰기 동작을 통해서 SDRAM을 효율적으로 사용할 수 있다. 이 방법은 DMA가 마이크로프로세서의 SDRAM 억세스를 최소한의 방해로 SDRAM을 사용할 수 있다. 이와 같은 방법을 이용함으로써 전체적인 시스템 효율을 높여 약 16.8% 정도의 성능 향상 효과를 가져옴을 확인 할 수 있었다.

• 한국정밀공학회지
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• 제22권1호
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• pp.199-206
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• 2005

Mask manufacturing is a high COC and COO process in developing of semiconductor devices because of mask production tool with high resolution. Direct writing has been thought to be the one of the patterning method to cope with development or small-lot production of the device. This study consists two categories. One is the additional process of the direct and maskless patterning generation using SLA for easy and convenient application and the other is a removal process using wet-etching process. In this study, cured status of epoxy pattern is most important parameter because of the beer-lambert law according to the diffusion of UV light. In order to improve the contact force between patterns and substrate, prime process was performed and to remove the semi-cured resin which makes a bad effects to the pattern, spin cleaning process using TPM was also performed. At a removal process, contact force between photo-curable resin as an etching mask and Si wafer is important parameter.

• 한국정밀공학회지
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• 제31권12호
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• pp.1077-1083
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• 2014

Multi-material Additive Manufacturing (AM) is being focused to apply for direct manufacturing of a product. In this paper, a three-dimensional circuit device (3DCD) fabrication technology based on the multi-material AM technology was proposed. In contrast with conventional two-dimensional Printed Circuit Board (PCB), circuit elements and conducting wires of 3DCD are placed in threedimensional configuration at multiple layers of the structure. Therefore, 3DCD technology can improve design freedom of an electronic product. In this paper, 3DCD technology is proposed based on AM technology. Two types of 3DCD fabrication systems were developed based on the Stereolithography and the Fused Deposition Modeling technologies. And the 3DCD samples which have same function were fabricated, successfully.

• 한국레이저가공학회지
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• 제6권1호
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• pp.33-40
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• 2003

The ablative decomposition mechanism of PMMA(polymethyl methacrylate) and PET(polyethylene terephthalate) with KrF excimer laser(λ : 248nm, pulse duration: 5㎱) is investigated. The UV/Vis spectrometer analysis showed that PMMA is a weak absorber and PET is a strong absorber at the wavelength of 248nm. The results(surface debris, melt, etch depth, etching shape) from drilling and direct writing experiments imply that ablation mechanism of PMMA is dominated by photothermal process, while that of PET is dominated by photochemical process.

• 한국정밀공학회지
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• 제26권5호
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• pp.57-63
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• 2009

Interface friction in blanking dies, cold forging and extrusion of aluminum alloys is a major cause of inefficient process. This paper describes an investigation of femtosecond laser texturing for reduction of interface friction on sliding surfaces in forming process. Femtosecond direct writing technology was used to fabricate a laser micro-machined die and to create microgroove patterns with varying size and density on metal forming dies. A systematic approach to find the optimum parameters and computer simulation comparison of friction coefficients are provided to study the relation of friction coefficients and die profiles. In metal forming tests, the effectiveness of various laser-machined patterns for enhancing interface lubrication is determined.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1179-1180
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• 2005

3D micro scaled shapes are fabricated with the method of direct writing and superposing grooving in ambient air using femto-second laser pulses and copper, aiming at establishing an industrially useful femto-second laser processing machine to be able to fabricate three dimensional micro-scale structures, especially micro scaled molds, and processing techniques. For the several advantages, there is no thermally influenced region around the area irradiated by the laser beam and surfaces irradiated laser beam are smooth and substances ablated to form are no attached on the surface of works and so on, the femto-second laser technology is anticipated for advanced micro/nano precision technology.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 추계학술발표대회 개요집
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• pp.79-81
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• 2004

In this study EB(Electron Beam) welder was modified to apply Ef welder to micro-joining for soldering and micro-brazing. The power and beam current of EB welder is 6kW, 100mA(60kV) and the minimum current was 1mA. The minimum current of EB welder was modified to decrease the amount of beam current to 0.0lmA and the monitoring system to observe materials was made up. The system is developed including teaching function for generating patterns. The control system and CAD/CAM software for EB direct writing was developed and the deflection beam was controlled without moving workpieces. the possibility of applying EB welder to micro-joining for soldering and brazing was studied through this experiments.

• 영어어문교육
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• 제10권2호
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• pp.113-132
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• 2004

This study aims to suggest desirable directions through analyzing English test items of college entrance examinations(CEE) in Korea, China, and Japan. To achieve this, English test items of Scholastic Ability Test(SAT) in Korea were compared with those of CEE in China and Japan, and test items of TOEFL and IELTS. It was found that there were not many items for testing productive skills relatively to the tests of other countries including TOEFL and IELTS. Especially, there were integrated items for writing test in China. In case of speaking test, all the other country adopted direct ways like interview and oral test, not indirect test as in the SAT in Korea. It is suggested that there need to be included test items comprising long passages in order to measure extensive reading ability. It can be suggested that doze test be adopted for testing integrated proficiency of English.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2018년도 춘계학술대회
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• pp.638-640
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• 2018

본 논문에서는 800nm급 펨토초 레이저를 이용하여 FBG 센서를 제작하였다. 제작된 센서는 누적 방사선량 100kGy 감마선에 조사하였고, 광섬유 코팅재료에 따른 방사선 영향을 평가하였다.