• Journal of the Korean Society for Precision Engineering
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• v.29 no.1
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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.

• Journal of IKEEE
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• v.10 no.1 s.18
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• pp.22-29
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• 2006

In this paper, we present the efficient way of SDRAM accessing through the DMA(Direct Memory Access) when a microprocessor and peripheral blocks are sharing a SDRAM. The microprocessor is able to access a memory through the AMBA which is the system bus provided by ARM Corporation and DMAs are able to access a memory through their own bus. Peripheral block's reading and writing on the SDRAM memory are realized by the intermediate DMA in order to minimize times of access and addressing the memory. While the microprocessor doesn‘t access to the SDRAM aproaching other registers or occurring a hit signal for fetching program or data, the DMAs may read/write the data in the SDRAM without an interference of the AMBA. This way increases the efficient of the system and performance is more by 16.8%.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.1
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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.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.12
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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.

• Laser Solutions
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• v.6 no.1
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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.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.5
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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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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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.

• Proceedings of the KWS Conference
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• v.43
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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.

• English Language & Literature Teaching
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• v.10 no.2
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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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.638-640
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• 2018

In this paper, FBG sensor is fabricated using 800nm femtosecond laser. The sensor was irradiated with a cumulative dose of 100 kGy gamma ray, and the effect of radiation on the FBG coating material was evaluated.