• Journal of the Korea Safety Management & Science
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• v.4 no.2
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• pp.209-221
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• 2002

Machinability improvement by the use of liquid nitrogen in cryogenic machining has been reported in various studies. This has been mostly attributed to the cooling effect of liquid nitrogen. However, No study has been found in discussion on whether liquid nitrogen possesses lubrication effect in cryogenic cutting. In machining tests, cryogenic machining reduced the force component in the feed direction, indicating that the chip slides on the tool rake face with lower friction. This study also found that the effectiveness of LN2 lubrication depends on the approach how LN2 is applied regarding cutting forces related.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.2
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• pp.195-206
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• 2002

The conjugate heat transfer from the simulated module in a horizontal channel with the variation of inlet air temperature is experimentally investigated. The aim of this study is to estimate temperature difference between a module and inlet air. This study is performed with the variation of parameters that are inlet air temperature(Ti=25~$55^{\circ}C), thermal resistance( $R_c$=0.05, 4.11, 158 K/W), inlet air velocity(Vi=0.1~1.5m/s), and input power(Q=3, 7 W). The results show that the effect of inlet air temperature is little, at the case of using conductive board. And input power was most effective parameter on the temperature difference between module and Inlet air.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.49-55
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• 2011

Recently, various efforts to make more speedy and precision machine tool to improve productivity and also various efforts to solve environmental problem are going on, so that dry cutting in manufacturing industry, which needs environmental conscious design and development of manufacturing technique, is becoming a very important assignment to solve. Because dry cutting does not use cutting fluid, we need other methods that can be used instead of cutting fluid, which does cooling, lubricating, chip washing, and anti-corrosion. Especially, because turning is a continuous work, the consideration of tool life and surface roughness due to continuous heat and poor lubrication is important. The purposes of this paper are the consideration of how well the compressed air can work instead of cutting fluid, and also the development of the method to select the optimum machining condition by the minimum numbers of experiments through the Taguchi method.

• Journal of Astronomy and Space Sciences
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• v.17 no.1
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• pp.53-66
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• 2000

We developed low light CCD imaging system using thermoelectric cooling method collaboration with a company to design a commercial model. It consists of Kodak KAF-0401E(768$\times$512 pixels) CCD chip, thermoelectric module manufactured by Thermotek. This TEC system can reach an operative temperature of $-25^{\circ}C$. We employed an Uniblitz VS25s shutter and it has capability a minimum exposure time 80ms. The system components are an interface card using a Korea Astronomy Observatory (hereafter KAO) ISA bus controller, image acquisition with AD9816 chip, that is 12bit video processor. The performance test with this imaging system showed good operation within the initial specification of our design. It shows a dark current less than 0.4e-/pixel/sec at a temperature of $-10^{\circ}C$, a linearity 99.9$\pm$0.1%, gain 4.24e-/adu, and system noise is 25.3e-(rms). For low temperature CCD operation, we designed a TEC, which uses a one-stage peltier module and forced air heat exchanger. This TEC imaging system enables accurate photometry($\pm$0.01mag) even though the CCD is not at 'conventional' cryogenic temperatures(140k). The system can be a useful instrument for any other imaging applications. Finally, with this system, we obtained several images of astronomical objects for system performance tests.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.12
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• pp.540-551
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• 2008

Today's microprocessor designs are not free from temperature as well as power consumption. As processor technology scales down, an on-chip circuitry increases power density, which incurs excessive temperature (hotspot) problem. To tackle thermal problems cost-effectively, Dynamic Thermal Management (DTM) has been suggested: DTM techniques have benefits of thermal reliability and cooling cost. However, they require trade-off between thermal control and performance loss. This paper proposes a dual integer register file structure to minimize the performance degradation due to DTM invocations. In on-chip thermal control, the most important functional unit is an integer register file. It is the hotspot unit because of frequent read and write data accesses. The proposed dual integer register file migrates read data accesses by adding an extra register file, thus reduces per-unit dynamic power dissipation. As a result, the proposed structure completely eliminates localized hotspots in the integer register file, resulting in much less performance degradation by average 13.35% (maximum 18%) improvement compared to the conventional DTM architecture.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.103-110
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• 2014

Recent TSV based 3D Integrated Circuit (IC) technology needs more powerful thermal management techniques. However, because cooling cost and form factor are restricted, thermal management are emphasis on software based techniques. But in case of throttling thermal management which one of the most candidate technique, increasing bus occupation induce total performance decrease. To solve communication bottleneck issue in TSV based 3D SoC, we proposed adaptive throttling technique Experimental results show that the proposed method can improve throughput by about 72% compare with minimal path routing.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.35-39
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• 2023

ESG (Environment, Social, Governance) has become a major guideline for many companies to improve corporate value and enable sustainable management. Among them, the environment requires a technological approach. This is because technological solutions are needed to reduce or prevent environmental pollution and save energy. Semiconductor package technology has been developed to better satisfy the essential roles of semiconductor packaging: chip protection, electrical/mechanical connection, and heat dissipation. Accordingly, technologies have been developed to improve heat dissipation effect, improve electrical/mechanical properties, improve chip protection reliability, stacking and miniaturization, and reduce costs. Among them, heat dissipation technology increases thermal efficiency and reduces energy consumption for cooling. Also, technology to improve electrical characteristics has had an impact on the environment by reducing energy consumption. Technologies that recycling or reducing material consumption reduce environmental pollution. And technologies that replace environmentally harmful substances contribute to environmental improvement, in particular. In this paper, I summarize trends in semiconductor package technologies to prevent pollution and improve environment.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.91-98
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• 2010

The increasing of power and processing speed and miniaturization of central processor unit (CPU) used in electronics equipment requires better performing thermal management systems. A typical thermal management package consists of thermal interfaces, heat dissipaters, and external cooling systems. There have been a number of experimental techniques and procedures for estimating thermal conductivity of thin, compressible thermal interface material (TIM). The TIM performance is affected by many factors and thus TIM should be evaluated under specified application conditions. In compact packaging of electronic equipment the chip is interfaced with a thin heat spreader. As the package is made thinner, the coupling between heat flow through TIM and that in the heat spreader becomes stronger. Thus, a TIM characterization system for considering the heat spreader effect is proposed and demonstrated in detail in this paper. The TIM test apparatus developed based on ASTM D-5470 standard for thermal interface resistance measurement of high performance TIM, including the precise measurement of changes in in-situ materials thickness. Thermal impedances are measured and compared for different directions of heat dissipation. The measurement of the TIM under the practical conditions can thus be used as the thermal criteria for the TIM selection.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1345-1356
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• 2014

The thermal behavior of power modules is an important criterion for the design of cooling systems and optimum thermal structure of these modules. An important consideration for high power and high frequency design is the spacing between semiconductor devices, substrate structure and influence of the boundary condition in the case. This study focuses on the thermal behavior of hybrid power modules to establish a simplified method that allows temperature estimation in different module components without decapsulation. This study resulted in a correction of the junction temperature values estimated from the transient thermal impedance of each component operating alone. The corrections depend on mutual thermal coupling between different chips of the hybrid structure. A new experimental technique for thermal mutual evaluation is presented. Notably, the classic analysis of thermal phenomena in these structures, which was independent of dissipated power magnitude and boundary conditions in the case, is incorrect.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.1
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• pp.59-64
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• 2005

This paper describes an investigation about the fluid delivering method that minimizes the generation of hydrodynamic pressure and improves the grinding accuracy. Traditionally, grinding fluid is delivered for the purpose of cooling, chip flushing and lubrication. Hence, a number of conventional investigations are focused on the delivering method to maximize fluid flux into the contact arc between the grinding wheel and the work piece. It is already known that hydrodynamic pressure generates due to this fluid flux, and that it affects the overall grinding resistance and machining accuracy. Especially in the ultra-precision mirror grinding process that requires extremely small amount of cut per pass, its influence on the machining accuracy becomes more significant. Therefore, in this paper, a new delivering method of grinding fluid is proposed with focus on minimizing the hydrodynamic pressure effect. Experimental data indicates that the proposed method is effective not only to minimize the hydrodynamic pressure but also to improve the machining accuracy.