• Journal of the Microelectronics and Packaging Society
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• v.18 no.3
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• pp.25-32
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• 2011

We have studied on the slicing and polishing processes of R-plane sapphire wafers for the substrates of UHB nonpolar a-plane GaN LED. The fabrication conditions of the R-plane and c-plane wafers were influenced by the large anisotropic properties (mechanical properties) of the sapphire. The slicing process was more affected by the anisotropic properties of R-plane than the polishing process. When the slicing direction was $45^{\circ}$ to the a-flat, the slicing time was shorter and the quality of as-slicing wafers was better than the slicing direction of normal to the a-flat. The MRR(Material removal rate) of mechanical polishing processes such as lapping and DMP(Diamond mechanical polishing) did not show significant differences between the R-plane and c-plane. The MRR of the c-plane was about two times higher than that of R-planes at the CMP(Chemical mechanical polishing) process due to the formation of hydrolysis reaction layers on the surface of the c-plane.

• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.4
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• pp.637-642
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• 2010

Pre-treatment steps of fresh produce as Saengshik raw materials are followed by initial clean-up, dipping, primary washing, and cutting. Hypochlorous acid solution was applied in the dipping step to reduce natural microflora. Also, procedures were changed by cutting, dipping and then primary washing, and the efficacy of hypochlorus acid was evaluated. Potatoes, carrots, kales, and angelicas were submerged in water or 100 ppm of hypochlorous acid for 5 min. After initial clean-up, the aerobic plate counts of potatoes, carrots, kales and angelicas were 4.7, 5.3, 5.6, and 5.7 log CFU/g, respectively. When samples were submerged into water, it only reduced the population of natural microflora by 0.2 to 1.1 log CFU/g, whereas when treated with hypochlorous acid, it reduced the population by 0.5 to 2.8 log CFU/g. Reductions of natural microflora in green leafy vegetables were more highly achieved than bulbs such as potatoes and carrots. However, the numbers of natural microflora were increased after cutting step. To control the cross contamination at the cutting process, the process was changed as follows: initial clean-up, cutting, dipping in hypochlorous acid, and then primary washing. It showed effective reduction of the population by 2.3 to 3.2 log CFU/g. Hypochlorous acid solution could be useful as a sanitizer for surface washing of fresh vegetables.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.5748-5755
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• 2015

Scribing is cutting process to determine production amount and characteristic of LED chip. So it is an important process for fabrication of LED chip. Mechanical process and conventional scribing process with laser source has several problems such as thermal deformation, decreasing of material strength and limitation of cutting region. To solve these problems, internal laser scribing process that generates void in wafer and derives self-crack has been researched. However, studies of sapphire wafer cutting by internal laser scribing process for fabrication of LED chip are still insufficient. In this paper, cutting parameters were determined to apply internal laser scribing process for sapphire wafer for fabrication of LED chip. Then, foundation of cutting condition was established to set up internal laser scribing system through investigation of cutting characteristics by several experiments.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2418-2425
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• 1993

A two-dimensional transient heat transfer model for reactive gas assisted laser cutting process with a moving Gaussian heat source is developed using a numerical finite difference technique. The kerf width, melting front shape and temperature distribution were calculated by using the boundary-fitted coordinate system to handle the ejection of workpiece material and heat input from reaction and evaporation. An analytical solution for cutting front movement was adopted and numerical simulation was performed to calculate the temperature distribution and melting front thickness. To calculate the moving velocity of cutting front, the normal distribution of the cutting gas velocity was used. The kerf width was revealed to be dependent on the cutting velocity, laser power and cutting gas velocity.

• Proceedings of the KWS Conference
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• 1995.10a
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• pp.54-57
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• 1995

• 방재와보험
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• s.66
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• pp.32-36
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• 1995

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.334.1-334.1
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• 2016

다른 재료에 비해 에너지 변환 효율의 관점에서 높은 경쟁력을 가진 결정질 실리콘은 지난 수십 년 동안 그 특성이 태양전지 분야에 널리 이용되어 왔다. 하지만 결정질 실리콘 웨이퍼는 일반적으로 제조 단계에서 많은 양의 에너지를 소비하고 절단 단계에서 절단 손실(Kerf-loss)이 발생된다. Epoxy Resin을 이용한 Kerf-less Wafering은 초박형 실리콘 웨이퍼 제조 기술 중 하나로, 비교적 간단한 장비와 공정을 통하여 절단 손실 없이 $50{\mu}m$이하의 초박형 실리콘 웨이퍼를 얻을 수 있는 기술이다. 실리콘과 Epoxy Resin 간의 열팽창 계수 차이를 이용하여 초박형 실리콘을 박리 시키는 기술로, 실리콘 기판 위에 Epoxy Resin으로 stress inducing layer를 올려 공정을 진행한다. stress inducing layer를 경화시키는 열처리가 끝나고 급냉되는 과정에서 stress inducing layer에 의해 실리콘 기판에 큰 응력이 가해지게 되고 실리콘 기판에 crack이 발생된다. 공정이 계속 됨에 따라 발생된 crack은 실리콘 표면과 평행한 방향으로 전파 되고 초박형 실리콘 layer가 실리콘 기판에서 박리 된다. 본 실험에서 중요한 공정 변수로는 stress inducing layer의 구성성분 및 두께, 열처리 온도 및 시간, cooling rate 등이 있다. 이러한 공정 변수들을 조절 하여 Epoxy Resin을 이용하여 $100{\mu}m$ 이하의 박리된 wafer를 얻을 수 있었다. 박리된 wafer의 단면과 두께를 Scanning Electron Microscopy(SEM)을 통해 관찰 하였고, 이를 통해 초박형 실리콘 박리 공정에 대한 연구를 진행하였다.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.910-915
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• 2004

The objective of this study is to investigate the influence of process parameters, such as power of laser, travel speed of laser and material thickness, on the practical cutting region and the kerfwidth for the case of cutting of CSP 1N sheet using high power Nd:YAG laser with continuous wave(CW). In order to find the practical cutting region and the relationship between process parameters on the kerfwidth, several laser cutting experiments are carried out. The effective heat input is introduced to consider the influence of power and travel speed of laser on the kerfwidth together. From the results of experiments, the allowable cutting region and the relationship between the effective heat input and kerfwidth for the case of cutting of CSP 1N sheet using high power CW Nd:YAG laser have been obtained to improve the dimensional accuracy of the cut area.

• The Optical Journal
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• v.11 no.6 s.64
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• pp.60-68
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• 1999

지난 호에는 일반적인 광학부품의 제조공정을 알아보고, 제조 공정 및 특기 사항 가운데 소재선정, 소재 절단 및 blank 제작, 응력 제거, Chemical etching, Blocking을 살펴보았다. 이번 호에는 Lapping, Polishing, 세척, 측정에 대해서 기술한다.

• Laser Solutions
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• v.4 no.2
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• pp.47-57
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• 2001

This study deals with the laser cutting of stencil for the PCB. The most important aim of this study is to determine optimal conditions which make good-qualify stencil in Nd:YAG laser cutting. We made an experiment according to various variables (power. type of mask. gas pressure, cutting speed, and pulse width) and analyzed the cutting characteristics (surface roughness, kerf width. dross) . Each variable has optimal value for good-qualify cut edge under fixed condition. And neural network after learning experimental data with a million time iteration could predict surface roughness of cut edge under arbitrary condition approximately.