Thermal analysis of LED lamp with LTCC-COB package

Lee, Chang Keun,Ahn, Jung Keun,Lee, Cheul Ro,Kim, Daesuk,Baek, Byung Joon Emerald Group Publishing Limited 2013 Microelectronics international Vol.30 No.1

<B>Purpose</B> - The purpose of this paper is to investigate the thermal behaviors of high power LED packages to enhance the thermal performances of low temperature co-fired ceramic chip on board (LTCC-COB) package. Thermal analysis demonstrated an improved LTCC-COB package design that is comparable to a metal lead frame package with low thermal resistance. <B>Design/methodology/approach</B> - The LED device developed in this study is a LTCC package mounted directly on the metal PCB. A numerical simulation was performed to investigate the thermal characteristics of the LED module using the finite volume method, which is embedded in commercial software (Fluent V.6.3). Thermal resistance and temperature measurement validate the simulated results. <B>Findings</B> - The effect of the thickness of the die attach material on the thermal resistance was dominant due to low thermal conductivity, and the junction temperature decreased significantly with slight increases in thermal conductivity, especially when the value was less than 5?W/mK. The results reveal that the thermal resistance of MCPCB is about 49 per cent-58 per cent of the junction to board thermal resistance. The thermal model results showed good agreement with experimental results. <B>Originality/value</B> - The developed model overcomes the large thermal resistance of a conventional LTCC package for high power LED module. The extensive results have demonstrated an improved thermal design, optimal dimensions of each component and boundary conditions for high power LTCC-COB type package.

벨벳과 안감의 소재 조합에 따른 의복의 열저항에 관한 연구

이욱자,류덕환,조지현 한국의류학회 1999 한국의류학회지 Vol.23 No.1

This study was performed for the purpose of getting fundamental information requisite to wear velvet clothes that is more comfortable for the human body and also the environment. It was carried out in a human wearing test and thermal manikin test at the same time in a controlled-condition chamber. The experimental environment had a ambient temperature of 15±0.5℃, with the relative humidity at 50±5% and with air velocity at less than 0.2m/sec. Velvet differ from common plain weaves in thermal properties, because it's constructed in two parts, one is ground part and the other part is pile part. In order to investigate the thermal resistance of velvet, eight different combination of 4 velvet kinds and 2 lining kinds as experimental clothes. [(4 velvet kinds: Acetate, cuprammoium Rayon, Cotton, Wool), (2 lining kinds: acetate, viscose rayon)→8 combination: Aa, Av, Ra, Rv, Ca, Cv, Wa, Wv: the simplified character] The results of this study can be summarized as follows; 1. For the regional thermal resistance, the differences in eight clothes as well as the differences in each part were significant. As a whole, the breast part showed the highest thermal resistance, and the leg part was higher than the shank part. The rank of the total thermal resistance was put at Wa>Wv>Ca>Cv>Aa>Av>Ra>Rv in this order. 2. Considered clothing microclimate, microclimate temperature has a similar tendency to the total thermal resistance. It showed a significance in the differences of eight clothes and each parts. The belly part was highest in every combination. On the other hand, for clothing humidity there was a significance between back and breast part only in the human wearing test. 3. It was indicated that CLO value was highly positively correlated with the clothings weight and showed a high negative correlation with the air permeability.

Thermal Resistance of Insulated Precast Concrete Sandwich Panels

Sani Mohammed Bida,Farah Nora Aznieta Abdul Aziz,Mohd Saleh Jaafar,Farzad Hejazi,Nabilah Abu Bakar 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.6

Many nations are already working toward full implementation of energy efficiency in buildings known as Green Building. In line with this perspective, this paper aims to develop a thermally efficient precast concrete sandwich panels (PCSP) for structural applications. Therefore, an experimental investigation was carried out to determine the thermal resistance of the proposed PCSP using Hotbox method and the results were validated using finite element method (FEM) in COMSOL Multiphysics Software. The PCSP were designed with staggered shear connectors to avoid thermal bridges between the successive layers. The staggered connectors are spaced at 200 mm, 300 mm and 400 mm on each concrete layer, while the control panel is designed with 200 mm direct shear connection. In the experimental test, four (4) panels of 500 mm × 500 mm and 150 mm thick were subjected to Hotbox Test to determine the thermal resistance. The result shows that thermal resistance of the PCSP with staggered shear connection increases with increase in spacing. The PCSP with 400 mm staggered shear connectors indicates the best thermal efficiency with a thermal resistance (R value) of 2.48 m²K/W. The thermal performance was verified by FEA which shows less than 5% error coupled with a precise prediction of surface temperature gradient. This indicates that, with conventional materials, thermal path approach can be used to develop a precast concrete building with better thermal resistant properties. Hopefully, stakeholders in the green building industry would find this proposed PCSP as an alternative energy efficient load bearing panel towards sustainable and greener buildings.

계면 열전달 매칭 기반 온도감응 열메타물질 열기능 제어

경대현(Daehyeon Kyeong),이현민(Haunmin Lee),최원준(Wonjoon Choi) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12

We propose the concept of phase change thermal metamaterial which is appropriate to manipulate the heat flux based on a specific temperature by controlling the interfacial thermal resistance. The phase change thermal metamaterial is a material capable of controlling the heat path in response to a specific temperature through a combination of a metal and a phase change material. Therefore, when the phase of materials is changed from solid to liquid or vice versa, the characteristics of the interface between the materials change continuously so that the interfacial thermal resistance acts as a more important factor. Because interfacial thermal resistance is mainly determined by the contact area and the degree of phonon scattering between the materials, it is conclusively related with the effective thermal conductivity in phase change material. Here, we demonstrated the impacts of the graphene nanofiller in phase change material and Layer-by-Layer coatings (MWCNT-PEI, MWCNT-PEI-Silane) via simulation tool and experimental setups using thermal unit-cell shifter which is proper to manipulate the interfacial thermal resistance, thereby optimally designing temperature responsive thermal metamaterals.

용사 코팅된 스틸바의 트라이볼로지적 특성의 형상학적 관찰

이덕규(Duk Gyu Lee),조희근(Hee Keun Cho) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.5

제철공장의 소결대차 스틸바의 내열성, 내마모성, 내부식성 등의 성질을 향상시키기 위하여 용사코팅을 적용한 연구가 진행되었다. 약 700℃의 고온환경에서 내열, 내마모, 부식 등에 노출되어 있는 스틸의 표면에 Al₂O₃, Cr₂O₃, WC 코팅을 적용하여 국부적으로 고온내마모성, 내식성, 내열성, 내열충격성등을 향상시킴으로써 기존 제강공정에서 사용되는 스틸바의 수명을 향상시켰다. 스틸바에 적용한 금속용사 코팅층에 대하여 고온내마모시험, 열충격시험, 내부식시험을 수행하였다. 코팅층의 물리적, 화학적, 기계적 특성이 코팅이 안된 재료에 비해 매우 우수하였다. Plasma coatings have been conducted to improve the mechanical properties of thermal resistance, wear resistance, corrosion resistance and thermal shock with respect to Great-Bar which is used as a carrier device for ironstone sintering under 700℃. The surface coatings on the upper side of the Great-Bar exposed on extreme environments of high temperature, severe wear, corrosion and thermal shock extended the life time due to the barrier coating layer. Al₂O₃, Cr₂O₃, WC coatings were applied to Great-Bar and their mechanical and chemical properties are analyzed by several experimental tests such as thermal resistance, wear resistance, corrosion resistance and thermal shock resistance. It shows excellent advantages with respect to wear, thermal shock and corrosion.

Effects of some factors on the thermal-dissipation characteristics of high-power LED packages

Ji, Peng Fei,Moon, Cheol-Hee The Korean Infomation Display Society 2012 Journal of information display Vol.13 No.1

Decreasing the thermal resistance is the critical issue for high-brightness light-emitting diodes. In this paper, the effects of some design factors, such as chip size (24 and 35 mil), substrate material (AlN and high-temperature co-fired ceramic), and die-attach material (Ag epoxy and PbSn solder), on the thermal-dissipation characteristics were investigated. Using the thermal transient method, the temperature sensitivity parameter, $R_{th}$ (thermal resistance), and junction temperature were estimated. The 35-mil chip showed better thermal dissipation, leading to lower thermal resistance and lower junction temperature, owing to its smaller heat source density compared with that of the 24-mil chip. By adopting an AlN substrate and a PbSn solder, which have higher thermal conductivity, the thermal resistance of the 24-mil chip can be decreased and can be made the same as that of the 35-mil chip.

Effects of some factors on the thermal-dissipation characteristics of high-power LED packages

Peng Fei Ji,문철희 한국정보디스플레이학회 2012 Journal of information display Vol.13 No.1

Decreasing the thermal resistance is the critical issue for high-brightness light-emitting diodes. In this paper, the effects of some design factors, such as chip size (24 and 35 mil), substrate material (AlN and high-temperature co-fired ceramic), and dieattach material (Ag epoxy and PbSn solder), on the thermal-dissipation characteristics were investigated. Using the thermal transient method, the temperature sensitivity parameter, Rth (thermal resistance), and junction temperature were estimated. The 35-mil chip showed better thermal dissipation, leading to lower thermal resistance and lower junction temperature, owing to its smaller heat source density compared with that of the 24-mil chip. By adopting an AlN substrate and a PbSn solder,which have higher thermal conductivity, the thermal resistance of the 24-mil chip can be decreased and can be made the same as that of the 35-mil chip.

단순 선형열원 모델을 이용한 지중 유효 열전도도와보어홀 유효 열저항 산정

손병후 대한설비공학회 2007 설비공학 논문집 Vol.19 No.7

The design of a ground-source heat pump system includes specifications for a ground loop heat exchanger where the heat transfer rate depends on the effective thermal conductivity of the ground and the effective thermal resistance of the borehole. To evaluate these heat transfer properties, in-situ thermal response tests on four vertical test boreholes with different grouting materials were conducted by adding a monitored amount of heat to circulating water. The line-source method is applied to the temperature rise in an in-situ test and extended to also give an estimate of borehole effective thermal resistance. The effect of increasing thermal conductivity of the grouting materials from 0.818 to 1.104W/m℃ resulted in overall increases in effective thermal conductivity by 15.8 to 56.3% and reductions in effec- tive thermal resistance by 13.0 to 31.1%.

열간단조 금형 육성용접부 내균열성 및 내열충격성 평가방법에 관한 연구

조상명,김성호,정연호,백승희,장종훈,박철규,우희철,정병호,Cho, Sang-Myung,Kim, Sung-Ho,Jung, Yun-Ho,Baek, Seung-Hui,Jang, Jong-Hun,Park, Chul-Gyu,Woo, Hee-Chul,Jung, Byong-Ho 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.3

Hardfacing is one of the frequently applying method to increase surface hardness in hot forging die. Recently, hardfacing receives great attention due to it's repair availability and low cost. In hot forging die, crack resistance and thermal shock resistance have been considered as major properties, However there are few studies for the assessment of these properties. So, it is necessary to establish the assessment method for crack resistance and thermal shock resistance in hardfacing for hot forging die. In this study, flux cored arc welding was applied to make hardfacing welds. Three point bending test was carried out to assess hardfacing weld's crack resistance, and high temperature bending test using salt bath was developed for thermal shock resistance. Consequently, it was possible to assess crack resistance and thermal shock resistance of hardfacing welds for hot forging die quantitatively.

Thermal Interface Modeling and Experiments with Novel Multi-layer Structure in Modular Microsatellite

Hao Zhang,Jun Zhou,Guanghui Liu,Zongyi Guo 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.5

The thermal interface of a modular microsatellite can be equated to a multi-layer structure which is used to transfer heat between modules to maintain the temperature in a healthy range. To describe the heat transfer process at the thermal interface, an improved one-dimensional RC heat transfer model based on a thermal–electric analogy is proposed, considering both three complex heat transfer modes (heat conduction, radiation, and convection) and thermal contact resistance to describe the temperature variation at the thermal interface. Then, the temperature response of the novel thermal interface with five layers of materials is solved using step temperature boundary conditions, and the obtained temperature response is compared with the models considering only heat conduction. The comparison results show that the temperature prediction accuracy of the proposed model increased by 4.1%. Finally, experiments are designed and compared with the simulation results, which verify the validity of the proposed model.