• 마이크로전자및패키징학회지
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• 제23권4호
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• pp.35-41
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• 2016

고출력 LED 조명용 패키지를 제조함에 있어서 발열은 LED의 광출력과 수명에 매우 중요한 영향을 주는 인자로 알려져 있다. 본 연구에서는 가로등용 고출력 LED 패키지를 개발함에 있어서 효과적인 방열을 하기 위하여 방열효과가 상대적으로 우수한 구조인 chip-on-a-heat sink 구조를 가지는 세라믹-메탈 기반의 패키지를 제조하였다. 열확산 기능을 하는 heat sink 기판소재는 알루미늄 합금을, LED 어레이 회로를 형성하는 절연막으로는 저온동시소성용 glass-ceramics을 사용하였다. 특히 열처리 시 가장 이슈가 되는 세라믹-금속 하이브리드 패키지 기판의 휨을 억제하기 위한 수단으로서, glass-ceramic 절연막을 부분 코팅함으로써 휨현상을 용이하게 줄일 수 있게 되었다. 또한, LED 패키지의 방열특성의 향상 즉 열저항도 기존의 MCPCB 패키지나 전면 코팅형 절연막 패키지에 비해 훨씬 낮아지는 효과를 얻었을 뿐 아니라, 세라믹 코팅소재의 절감효과도 볼 수 있게 되었다.

• 반도체디스플레이기술학회지
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• 제3권4호
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• pp.29-32
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• 2004

Fully depleted Silicon-on-Insulator (FD-SOI) devices lead to better electrical characteristics than bulk CMOS devices. However, the presence of a thin top silicon layer and a buried SiO2 layer causes self-heating due to the low thermal conductivity of the buried oxide. The electrical characteristics of FDSOI devices strongly depend on the path of heat dissipation. In this paper, we present a new three-dimensional (3-D) analysis technique for the self-heating effect of the finger-type and bar-type transistors. The 3-D analysis results show that the drain current of the finger-type transistor is 14.7% smaller than that of the bar-type transistor due to the 3-D self-heating effect. We have learned that the rate of current degradation increases significantly when the width of a transistor is smaller that a critical value in a finger-type layout. The current degradation fro the 3-D structures of the finger-type and bar-type transistors is investigated and the design issues are also discussed.

• 한국전기전자재료학회논문지
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• 제13권4호
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• pp.337-342
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• 2000

We fabricated resistive superconducting fault current limiters based on YB $a_{2}$/C $u_{3}$/ $O_{7}$ thin films and investigated their quench propagation characteristics. The YB $a_{2}$/C $u_{3}$/ $O_{7}$ films was coated with a gold layer and patterned into 1 mm wide meander lines by photolithography. The quench was concluded to start locally and propagates until completed. The quench propagation characteristics were explained based on the heat transfer within the film as well as between the film and the surrounding liquid nitrogen. The quench completion time depended strongly on potential fault current amplitude and not significantly on fault angle which indicates that the quench propagation speed is affected more by heat dissipation rate than by fault current increase rate. The quench completion time was 1 msec at the fault current of 65 $A_{peak/{\ak}}$.

• 대기
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• 제32권4호
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• pp.277-295
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• 2022

The global weather prediction model, Korean Integrated Model (KIM), has been in operation since April 2020 by the Korea Meteorological Administration. This study assessed the performance of heat waves (HWs) in Korea in 2020. Case experiments during 2018-2020 were conducted to support the reliability of assessment, and the factors which affect predictability of the HWs were analyzed. Simulated expansion and retreat of the Tibetan High and North Pacific High during the 2020 HW had a good agreement with the analysis. However, the model showed significant cold biases in the maximum surface temperature. It was found that the temperature bias was highly related to underestimation of downward shortwave radiation at surface, which was linked to cloudiness. KIM tended to overestimate nighttime clouds that delayed the dissipation of cloud in the morning, which affected the shortage of downward solar radiation. The vertical profiles of temperature and moisture showed that cold bias and trapped moisture in the lower atmosphere produce favorable conditions for cloud formation over the Yellow Sea, which affected overestimation of cloud in downwind land. Sensitivity test was performed to reduce model bias, which was done by modulating moisture mixing parameter in the boundary layer scheme. Results indicated that the daytime temperature errors were reduced by increase in surface solar irradiance with enhanced cloud dissipation. This study suggested that not only the synoptic features but also the accuracy of low-level temperature and moisture condition played an important role in predicting the maximum temperature during the HWs in medium-range forecasts.

• 마이크로전자및패키징학회지
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• 제23권4호
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• pp.87-92
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• 2016

전자소자의 방열모듈에서 두께 방향의 열방출 특성에 대한 중요성이 증가하고 있다. 금속과 금속의 본딩 및 유전체와 금속의 본딩 구조를 갖는 2가지 종류의 2층 층상재료를 제조한 후 두께 방향으로 열확산계수를 측정하였다. 금속(STS439)과 금속(Al6061)으로 이루어진 2층 층상재료에서는 섬광법(LFA)으로 열확산계수를 측정했을 때, 열흐름의 방향을 반대로 변화시켜도 열확산계수의 변화가 없었다. 그런데, 유전체(AlN-Polymer)와 금속(Al6061)의 2층 층상재료에서는 열흐름의 방향을 반대로 인가하였을 때 열확산계수는 17.5% 정도 다르게 나타났다. 유전체와 금속의 단면구조를 갖는 2층 층상재료에서, 금속에서 유전체 방향으로 측정한 열확산계수가 유전체에서 금속 방향으로 측정한 열확산계수에 비해 17.5% 작게 나타난 이유는, 금속내의 전자가 갖고 있던 에너지가 유전체 쪽으로 전달되기 위해서는 계면 주변에서 포논의 에너지 형태로 변환될 때 저항이 생기기 때문이다.

• 한국재료학회지
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• 제21권5호
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• pp.283-287
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• 2011

As the performance of microelectronic devices is improved, the use of copper as a heat dissipation member is increasing due to its good thermal conductivity. The high thermal conductivity of copper, however, leads to difficulties in the joining process. Satisfactory bonding with copper is known to be difficult, especially if high shear and peel strengths are desired. The primary reason is that a copper oxide layer develops rapidly and is weakly attached to the base metal under typical conditions. Thus, when a clean copper substrate is bonded, the initial strength of the joint is high, but upon environmental exposure, an oxide layer may develop, which will reduce the durability of the joint. In this study, an epoxy adhesive formulation was investigated to improve the strength and reliability of a copper to copper joint. Epoxy hardeners such as anhydride, dihydrazide, and dicyandiamide and catalysts such as triphenylphosphine and imidazole were added to an epoxy resin mixture of DGEBA and DGEBF. Differential scanning calorimetry (DSC) analyses revealed that the curing temperatures were dependent on the type of hardener rather than on the catalyst, and higher heat of curing resulted in a higher Tg. The reliability of the copper joint against a high temperature and high humidity environment was found to be the lowest in the case of dihydrazide addition. This is attributed to its high water permeability, which led to the formation of a weak boundary layer of copper oxide. It was also found that dicyandiamide provided the highest initial joint strength and reliability while anhydride yielded intermediate performance between dicyandiamide and dihydrazide.

• 한국광학회지
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• 제26권4호
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• pp.226-232
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• 2015

$8m{\times}6m$(400인치)의 대형 화면 액정 화상 투영기에 쓸 수 있는 광원부로서 엘이디를 2층으로 촘촘하게 배열한 광원과 그에 수반되는 조명광학계 설계의 개념을 제시하였다. 엘이디를 촘촘히 배열할 때 생기는 방열문제는 엘이디를 2층으로 배열하면 해결됨을 열분석을 통해 보였다. 뒤 층의 엘이디에서 나오는 빛이 앞 층에 가려질 수 있는 문제는 앞뒤로 어긋나게 배열하여 해결했고, 엘이디 배열에서 나온 빛을 투영렌즈에 맞추어 액정판을 고르게 비추는 조명광학계를 함께 설계하였다.

• Journal of Magnetics
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• 제22권2호
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• pp.181-187
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• 2017

Flow of electrically conducting nanofluids is of pivotal importance in countless industrial and medical appliances. Fluctuations in thermophysical properties of such fluids due to variations in temperature have not received due attention in the available literature. Present investigation aims to fill this void by analyzing the flow of copper-water nanofluid with temperature dependent viscosity past a Riga plate. Strong wall suction and viscous dissipation have also been taken into account. Numerical solutions for the resulting nonlinear system have been obtained. Results are presented in the graphical and tabular format in order to facilitate the physical analysis. An estimated expression for skin friction coefficient and Nusselt number are obtained by performing linear regression on numerical data for embedded parameters. Results indicate that the temperature dependent viscosity alters the velocity as well as the temperature of the nanofluid and is of considerable importance in the processes where high accuracy is desired. Addition of copper nanoparticles makes the momentum boundary layer thinner whereas viscosity parameter does not affect the boundary layer thickness. Moreover, the regression expressions indicate that magnitude of rate of change in effective skin friction coefficient and Nusselt number with respect to nanoparticles volume fraction is prominent when compared with the rate of change with variable viscosity parameter and modified Hartmann number.

• 한국수소및신에너지학회논문집
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• 제26권2호
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• pp.184-191
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• 2015

As the power electronics system increases the frequency, the power loss and thermal management are paid more attention. This research presents a real time model of dissipation power with junction temperature response for 120kw IGBT inverter which is applied to the thermal management of high power IGBT inverter. Since the computational time is critical for real time simulation, look-up tables of IGBT module characteristic curve are implemented. The power loss from IGBT provides a clue to calculate the temperature of each module of IGBT. In this study, temperature of each layer in IGBT is predicted by lumped capacitance analysis of layers with convective heat transfer. The power loss and temperature of layers in IGBT is then communicated due to mutual dependence. In the dynamic model, PWM pulses are employed to calculation real time IGBT and diode power loss. Under Matlab/Simulink$^{(R)}$ environment, the dynamic model is validated with experiment. Results showed that the dynamic response of power loss is closely coupled with effective thermal management. The convective heat transfer is enough to achieve proper thermal management under guideline temperature.

• 한국정밀공학회지
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• 제18권12호
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• pp.60-65
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• 2001

To simulate the real molding conditions, the effects of phase change and compressibility of the resin were considered in the present investigation. A modified Cross model with either an Arrhenius-type or WLF-type functional form was used for modeling viscosity of the resin. A double-domain Tait equation of state was employed to describe the compressibility of the resin during molding. The energy balance equation including latent-heat dissipation fur semi-crystalline materials was solved in order to predict the solidified layer and temperature profile. Injection molding experiments were carried out using polypropylene(PP) in the present study. Based on the comparison between experiments and simulations, it was found out the predicted pressure distributions and melt front propagations were accurate. Thus it was concluded that the program developed in this study was proved to be useful in simulations of injection molding process.