• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1065-1066
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• 2013

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.11
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• pp.33-41
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• 2014

This paper is research result for a development of sapphire silicon ingot glowing(SSIG) PWM converter system for 80kW 10kA. The system include 3-phase AC-DC diode rectifier of input voltage AC 380V and 60Hz, DC-AC single phase full bridge PWM inverter of high frequency, AC-DC single-phase full wave rectifier using center-tapped of transformer for low voltage 8.0V and large current 10,000A of output specification, tungsten resistor load 0.1[$m{\Omega}$]. PWM switching frequency for IGBT inverter control set 30kHz. The suggested researching contents are designed data sheets of power converter system, PSIM simulation, operating characteristics and analysis results of developed SSIG system. This paper propose

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.29-30
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• 2013

• Tribology and Lubricants
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• v.34 no.6
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• pp.209-216
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• 2018

Sapphire is a substrate material that is widely used in optical and electronic devices. However, the processing of sapphire into a substrate takes a long time owing to its high hardness and chemical inertness. In order to process the sapphire ingot into a substrate, ingot growth, multiwire sawing, lapping, and polishing are required. The lap grinding process using pellets is known as one of the ways to improve the efficiency of sapphire substrate processing. The lap grinding process ensures high processing efficiency while utilizing two-body abrasion, unlike the lapping process which utilizes three-body abrasion by particles. However, the lap grinding process has a high material removal rate (MRR), while its weakness is in obtaining the required surface roughness for the final polishing process. In this study, we examine the effects of free abrasives in lap grinding on the material removal characteristics of sapphire substrate. Before conducting the lap grinding experiments, it was confirmed that the addition of free abrasives changed the friction force through the pin-on-disk wear test. The MRR and roughness reduction rate are experimentally studied to verify the effects of free abrasive concentration on deionized water. The addition of free abrasives (colloidal silica) in the lap grinding process can improve surface roughness by three-body abrasion along with two-body abrasion by diamond grits.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.5
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• pp.350-355
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• 2000

The fabrication of sapphire wafer in C plane has been developed by horizontal Bridgeman method and GaN based semiconductor epitaxial growth has been carried out in metal organic chemical vapour deposition. The single crystalline ingot of sapphire has been utilized for 2 inch sapphire wafers and wafer slicing and lapping machines were designed. These several steps of lapping processes provided the mirror-like surface of sapphire wafer. The measurements of the surface flatness and the roughness were carried out by the atomic force microscope. The GaN thin film growth on the developed wafer was confirmed the wafer quality and applicability to blue light emitting devices.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1059-1060
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• 2013

• Tribology and Lubricants
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• v.32 no.2
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• pp.56-60
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• 2016

Sapphire has a high hardness and strength and chemical stability as a superior material. It is used mainly as a material for a semiconductor as well as LED. Recently, the cover glass industry used by a sapphire is getting a lot of attention. The sapphire substrate is manufactured through ingot sawing, lapping, diamond mechanical polishing (DMP) and chemical mechanical polishing (CMP) process. DMP is an important process to ensure the surface quality of several nm for CMP process as well as to determine the final form accuracy of the substrate. In DMP process, the material removal is achieved by using the mechanical energy of the relative motion to each other in the state that the diamond slurry is disposed between the sapphire substrate and the polishing platen. The polishing platen is one of the most important factors that determine the material removal characteristics in DMP. Especially, it is known that the geometric characteristics of the polishing platen affects the material removal amount and its distribution. This paper investigated the material removal characteristics and the effects of the polishing platen groove in sapphire DMP. The experiments were preliminarily carried out to evaluate the sapphire material removal characteristics according to process parameters such as pressure, relative velocity and so on. In the experiment, the monitoring apparatus was applied to analyze process phenomena in accordance with the processing conditions. From the experimental results, the correlation was analyzed among process parameters, polishing phenomena and the material removal characteristics. The material removal equation based on phenomenological factors could be derived. And the experiment was followed to investigate the effects of platen groove on material removal characteristics.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.6
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• pp.272-278
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• 2013

In this study, a c-axis displacement and an internal stress of the sapphire crystal of 300 mm length have been analyzed numerically and the crystal length having no sub-grain defects have been predicted. The hot zone structures were modified with the crucible geometry change and the additional insulation layer installed above the crucible. The simulation results show that the c-axis displacement difference between the original hot zone and others originated from the sub-grain defect formations in the sapphire ingot. When the crystal grown by CZ (Czochralski) grower using the modified hot zone, the crystal length having no sub-grain defects was increased about 57 mm maximum than the original one. When the simulation results compared with the experimental one, the predicted crystal length having no sub-grain defects were well corresponded with the experiment one in c-axis wafer of the 300 mm sapphire ingot. Therefore the sapphire crystal of 250 mm length having no sub-grain defects was successfully grown by CZ process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.147-148
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• 2012

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.1
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• pp.24-31
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• 2019

The current study demonstrates an efficient procedure to create ingots from $Al_2O_3$ powder using the skull melting method to use these ingots as a starting material in conventional methods for growing synthetic single-crystal sapphire. Dimension of the cold crucible was 24 cm in inner diameter and 30 cm in inner height, 15 kg of $Al_2O_3$ powder was completely melted within 1 h at an oscillation frequency of 2.75 MHz, maintained in the molten state for 3 h, and finally air-cooled. The areal density and components of the cooled ingot by parts were analyzed through scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The areal density and $Al_2O_3$ content of the ingot were related to the temperature distribution inside the cold crucible during high-frequency induction heating, and the area with high temperature was high tends to be high in areal density and purity.