• 반도체디스플레이기술학회지
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• 제19권4호
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• pp.51-58
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• 2020

Many types of optical plastic films are essential in optoelectronics display unit fabrication and it is important to develop high precision laser cutting methods of optical films with extremely low level of film surface contamination by fume particles. This study investigates the effects of suction and blowing air motions with air flow misalignment in removing fume particles from laser cut line by employing random particle trajectory simulation and probabilistic particle generation model. The computational results show fume particle dispersion behaviors on optical film under suction and blowing air flow conditions. It is found that suction air flow motion is more advantageous to blowing air motion in reducing film surface contamination outside designated target margin from laser cut line. While air flow misalignment adversely affects particle dispersion in blowing air flows, its effects become much more complicated in suction air flows by showing different particle dispersion patterns around laser cut line. It is required to have more careful air flow alignment in fume particle removal under suction air flow conditions.

• 한국기계가공학회지
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• 제14권6호
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• pp.104-110
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• 2015

LED has added value as a lighting source in the illuminating industry because of its high efficiency and low power consumption. In LED production processes, the chip cutting process, which mainly uses a scribing process with a laser has an effect on quality and productivity of LED. This scribing process causes problems like heat deformation, decreasing strength. The inner laser method, which makes a void in wafer and induces self-cracking, can overcome these problems. In this paper, cutting sapphire wafer for fabricating LED chip using the inner laser scribing process is proposed and evaluated. The aim is to settle basic experiment conditions, determine parameters of cutting, and analyze the characteristics of cutting by means of experimentation.

• 한국산학기술학회논문지
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• 제16권9호
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• pp.5748-5755
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• 2015

스크라이빙 공정은 LED 칩 생성을 위한 절단 공정으로 칩의 특성 및 생산량을 결정하는 중요한 공정이다. 기존의 기계적 방식 및 레이저 방식의 스크라이빙 공정은 칩의 열 변형 및 강도 저하, 절단 영역의 제한 등의 문제점이 있다. 이러한 문제를 해결하기 위해 웨이퍼 내부에 공극을 생성하여 자가 균열을 유도하는 내부 레이저 스크라이빙 공정이 연구되고 있으나 LED 칩 제작을 위한 사파이어 웨이퍼의 절단에 대한 연구는 미비한 실정이다. 본 논문은 LED 칩 제작에 사용되는 사파이어 웨이퍼의 내부 레이저 스크라이빙 공정을 적용하기 위해 주요 가공 변수를 정립하고 가공 실험을 통하여 절단 특성을 분석함으로써 내부 레이저 스크라이빙 시스템 구축을 위한 기초 가공 조건을 확립하였다.

• 한국정밀공학회지
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• 제16권9호
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• pp.62-67
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• 1999

In milling, cutting tool ins directly attached to spindle and this tells that spindle can provide very useful information on the cutting tool condition such as wear or breakage. Since spindle is rotating at a high speed, measuring spindle velocity using a noncontacting measurement system gives the best information which can be obtained. Due to the force applied to spindle through cutting tool, velocity of spindle changes. And any change in cutting tool condition affects cutting force and consequently spindle vibration. With the intent of continuously monitoring cutting tool condition in intermittent machining operations in a benign manner, a noncontacting velocity measurement system using a laser Doppler velocimeter was assembled to measure spindle torsional vibration. Spindle vibration was measured and analysis of it in the frequency domain yielded a measure which corresponded to amount of cutting tool wear in milling.

• Design & Manufacturing
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• 제17권2호
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• pp.15-21
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• 2023

In this study, a diamond turning machine and a laser-assisted machining module were utilized for the complex combined cutting of aspheric shapes and fine patterns on the surface of high-hardness brittle material, silicon. The analysis of material's form accuracy and corrective machining was conducted based on key factors such as laser output, rotational speed, feed rate, and cutting depth to achieve form accuracy below 1 ㎛ and surface roughness below 0.1 ㎛. The cutting condition and corrective machining methods were investigated to achieve the desired form accuracy and surface roughness. The rotational speed of the spindle and the linear feed rate of the diamond turning machine were varied in five stages for the cutting condition test. Surface roughness and form accuracy were measured using both a contact surface profilometer and a non-contact surface profilometer. The experimental results revealed a tendency of improved surface roughness with increased rotational speed of the workpiece, and the best surface roughness and form accuracy were observed at a feed rate of 5 mm/min. Furthermore, based on the cutting condition experiments, corrective machining was performed. The experimental results demonstrated an improvement in form accuracy from 0.94 ㎛ to 0.31 ㎛ and a significant reduction in the average value of the surface roughness curve from 0.234 ㎛ to 0.061 ㎛. This research serves as a foundation for future studies focusing on the machinability in relation to laser output parameters.

• 반도체디스플레이기술학회지
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• 제19권2호
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• pp.37-44
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• 2020

In improving laser cutting of optical plastic films for mass production of optoelectronics display units, it is important to understand particle contamination over optical film surface due to fume particle generation and dispersion. This numerical study investigates the effects of downward and upward air flow motions on fume particle dispersion around laser cut line. The simulations employ random particle sampling of up to one million fume particles by probabilistic distributions of particle size, ejection velocity and angle, and fume particle dispersion and surface landing are predicted using Basset-Boussinesq-Oseen model of low Reynolds number flows. The numerical results show that downward air flow scatters fume particles of a certain size range farther away from laser cut line and aggravate surface contamination. However, upward air flow pushes fume particles of this size range back toward laser cut line or sucks them up with rising air motion, thus significantly alleviating surface contamination.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권4호
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• pp.226-234
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• 2004

A rapid Prototyping system that laser-cuts and laminates thick layers can fabricate 3D objects promptly with a variety of materials. Building such a system must consider the surface distortions due to both vertical-cut layers and triangular surfaces. We developed a tangential layer-cutting algorithm by rearranging tangential lines such that they reconstruct 3D surfaces more closely and also constitute smoother laser trajectories. An energy function that reflects the surface-closeness with the tangential lines was formulated and then the energy was minimized by a gradient descent method. Since this simple method tends to cause many local minima for complex 3D objects, we tried to solve this problem by adding a simulated annealing process to the proposed method. To view and manipulate 3D objects, we also implemented a 3D visual environment. Under this environment, experiments on various 3D objects showed that our algorithm effectively approximates 3D surfaces and makes laser-trajectory feasibly smooth.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.453-454
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• 2011

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 1999년도 춘계학술발표대회 논문개요집
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• pp.5-8
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• 1999

• 한국정밀공학회지
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• 제26권4호
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• pp.47-54
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• 2009

In the last few years, lasers have found new applications as tools for ceramic machining which is laser-assisted machining(LAM). LAM process for the machining of difficult-to-machine materials such as structural ceramics, has recently been studied on silicon nitride workpiece for a wide range of operating condition. However, there have been few studies on rake angle in LAM process. In this paper we analyzed difference of machinability between positive and negative rake angle in tools. We have obtained interesting results that we could eliminate chattering, lower specific cutting and cutting ratio in case of positive rake angle. The results suggest that positive rake angled tools can make more plastic deformation and stable cutting of silicon nitride in comparison with negative rake angled one.