Papers by Keyword: Thermal Management

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Authors: Yutaka Furubayashi, Takafumi Tanehira, Kei Yonemori, Nobuhide Seo, Shinichiro Kuroki
Abstract: We propose 3-D integration of Peltier device onto a power device. In order to transport a heat from the power device, as a suitable material of the Peltier device, silicon was adopted because of its high Seebeck coefficient, high thermal conductivity, and applicability to semiconductor process. Bulk Si-based Peltier devices with conventional shape showed an active thermal transport over a Joule heat at the operation current less than 5 A. 3-D integration of 4H-SiC-based Schottky barrier diodes and Si-based film Peltier device, separated by intrinsic SiC layer, was realized by using conventional Si-based process flow.
Authors: Cong Wang, Won Sang Lee, Nam Young Kim
Abstract: A novel silicon-based packaging platform with the electroplated-based reflector and the electrode- guided interconnections is developed for the packaging component of a high-luminosity and high-efficiency multi-chip light-emitting diode (LED) module, which is patterned on a new type of insulating layer that consists of nanoporous anodized aluminum oxide (AAO) layer and plasma- enhanced chemical vapor deposition (PECVD) deposited silicon dioxide (SiO2) on a doped silicon substrate. The reflector and the electrical interconnections are successfully fabricated by using the electroplating method in the same body. In order to obtain the benefits of high efficiency LED modules, the requirements concerning thermal management and photomechanical layout have to be met. In this paper, we will discuss a novel fabrication method in LED module packaging platform, and then describe the thin layer of electroplated Cu/Ni/Au in order to reduce thermal resistance and to increase thermal diffusion efficiency. The heat generated by the LED chips is dissipated directly to the silicon body through the metal-plated platform, and truly excellent heat dissipation characteristics are observed. We demonstrate 987 lm 8 W-level cool-white light (5000 K, 16 V, 110 lm/W, CRI = 77) emission for 570 µm × 230 µm-chip LEDs at 600 mA operation.
Authors: Ying Ying Zhang, Jing Dong Huang, Ying Zhang
Abstract: The thermal management is crucial to the safety and lifespan of Solid Oxide Fuel Cell (SOFC) generation system. For the model-predictive control design, a model of SOFC thermal management system is proposed on the least squares support vector machine (LS-SVM). The model is composed of some thermal modules including SOFC stack, combustor, heat-exchanger and thermal equilibrium apparatus. It predicts the temperature distribution in SOFC generation system by computing the electrochemical reaction in the stack, the gas flow and the heat exchange through the modules. Checked by the experimental data, the model can be used for system temperature fast prediction with high precision and strong generalization ability, which meets the requirement of the research on the online predictive control design of SOFC generation system.
Authors: Jetsadaporn Priyadumkol, Chawalit Kittichaikarn
Abstract: The power trend of using server systems in data center is continuously increasing. Cooling system consumed 38% of total energy usage which is a significant contribution in the energy consumption. As a result, the efficient energy usage in data center is concerned.Normally a raised-floor is widely used in data center cooling system which delivers cool air through perforated tiles to a front of server racks. However it is usually found that this cool air cannot effectively remove a heat dissipation at the top of server racks. Therefore, the environmental condition in data center must be designed strictly to avoid disruption that caused by overheat.This paper gives some guidelines to help in the better design. Commercial Computational Fluid Dynamics (CFD) program was used to analyze the air flow from raised-floor air conditioning system. A tetrahedral of 1.8 million meshes with k- turbulence model were used to obtain the air flow velocity and temperature distributions in the room. The model was validated by comparing simulation results with actual measurements. As a result, dimensionless parameters in the form of supply heat index(SHI), for understanding the optimization of relative airflow distribution to the heat load of server rack was found. It shows that these parameters provide an effective tool to the improvement of energy efficiency in raised floor data center.
Authors: Jean François Silvain, Valérie Denis-Lutard, Pierre Marie Geffroy, Jean Marc Heintz
Abstract: Today, there is a strong push to improve the thermal management of electronic components in order to increase the performance and the reliability of electronic devices. Up to now, most of the heat sinks are mainly made of Copper that presents a good thermal conductivity (TC) but a coefficient of thermal expansion (CTE) much higher than the ceramic of the DBC (direct bonding Copper). It induces interfacial thermal stresses and indeed it decreases the reliability of the global electronic system. Therefore, there is a strong need for the development of novel heat dissipation material having low CTE combined with high TC. Carbon fibres reinforced copper matrix offers a good compromise between thermo mechanical properties (i.e. CTE) and medium TC. In order to increase surface TC, pure Copper can be added on the top surface and/or on the bottom one of the composite heat sink playing the role of heat spreader for hot spots linked with the Si components. The fabrication technique of these materials is based on powder metallurgy technique. The thermal properties of adaptive materials, TC and CTE, have been measured for different Copper thicknesses and architectures ([C/Cu], [Cu – C/Cu] and [Cu – C/Cu – Cu]). Simulation of the TC and CTE have been performed and compared to the experimental results.
Authors: Y. Baik, Robin A.L. Drew
Authors: Eric Casenove, Loic Pujol, Alexis Vossier, Arnaud Perona, Vincent Goetz, Alain Dollet
Abstract: Experiments and simulations were carried out to assess a passive device for cooling photovoltaic cells under concentrated sunlight. The cooling device was made of a Graphite- Phase Change Material (PCM) composite inserted in an aluminum enclosure. The PCM considered in this work was selected among several commercially available materials. Experimental plots of material temperature versus time were recorded for various incident solar powers and compared to 3D-thermal simulation predictions. Theoretical cell temperature profiles obtained using the PCM-based device were compared to those obtained without PCM, that is, using bulk (PCM-free) aluminum heat sink. The interest of using PCM cooling systems in CPV applications was finally discussed.
Authors: Fernand D.S. Marquis
Abstract: Owing to their exceptional stiffness, strength, thermal and electrical conductivity, carbon nanotubes have the potential for the development of nano composites materials for a wide variety of applications. In order to achieve the full potential of carbon nanotubes for structural, thermal and electrical multifunctional applications, both single wall carbon nanotubes (SWNTs), double wall nanotubes (DWNTs) and multi wall nanotubes (MWNTs) need to be developed into fully integrated carbon nanotube composites. Full integration of nanotubes requires their development beyond conventional composites so that the level of the non-nanotube material is designed to integrate fully with the amount of nanotubes and where the nanotubes are part of the matrix rather than a differing component, as in the case of conventional composites. In order to advance the development of multifunctional materials from nanotubes, this research is focused on the simultaneous control of structural properties, thermal and electrical conductivity of fully integrated carbon nanotube composites. These are hybrid material systems designed to surpass the limits of rule of mixtures engineering and composite design. The goals are to implement designs to fully mimic the properties of carbon nanotubes on larger scales for enhanced thermal and electrical management in addition to controlled strength and toughness. These new approaches involve, functionalization, dispersion, stabilization, alignment, polymerization and reaction bonding, in order to achieve full integration. Typical examples of polymeric and ceramic matrices, as well as other material systems are presented and discussed.
Authors: Hendrik Weidmueller, Thomas Weissgaerber, Thomas Hutsch, R. Huenert, T. Schmitt, K. Mauthner, J. Schulz-Harder
Abstract: Electronic packaging involves interconnecting, powering, protecting, and cooling of semiconductor circuits for the use in a variety of microelectronic applications. For microelectronic circuits, the main type of failure is thermal fatigue, owing to the different thermal expansion coefficients of semiconductor chips and packaging materials. Therefore, the search for matched coefficients of thermal expansion (CTE) of packaging materials in combination with a high thermal conductivity is the main task for developments of heat sink materials electronics, and good mechanical properties are also required. The aim of this work is to develop copper matrix composites reinforced with carbon nanofibers. The advantages of carbon nanofibers, especially the good thermal conductivity, are utlized to obtain a composite material having a thermal conductivity higher than 400W/mK. The main challenge is to obtain a homogeneous dispersion of carbon nanofibers in copper. In this paper, a technology for obtaining a homogeneous mixture of copper and nanofibers will be presented and the microstructure and properties of consolidated samples will be discussed. In order to improve the bonding strength between copper and nanofibers, different alloying elements were added. The microstructure and the properties will be presented and the influence of interface modification will be discussed.
Authors: Ludger Weber, Reza Tavangar
Abstract: Diamond-based metal matrix composites have been made based on pure Al and eutectic Ag-3Si alloy by gas pressure infiltration into diamond powder beds with the aim to maximize thermal conductivity and to explore the range of coefficient of thermal expansion (CTE) that can be covered. The resulting composites covered roughly the range between 60 and 75 vol-% of diamond content. For the Al-based composites a maximum thermal conductivity at room temperature of 7.6 W/cmK is found while for the Ag-3Si based composites an unprecedented value of 9.7 W/cmK was achieved. The CTE at room temperature varied as a function of the diamond volume fraction between 3.3 and 7.0 ppm/K and 3.1 and 5.7 ppm/K for the Al-based and the Ag-3Si-based composites, respectively. The CTE was further found to vary quite significantly with temperature for the Al-based composites while the variation with temperature was less pronounced for the Ag-3Si-based composites. The results are compared with prediction by analytical modeling using the differential effective medium scheme for thermal conductivity and the Schapery bounds for the CTE. For the thermal conductivity good agreement is found while for the CTE a transition of the experimental data from Schapery’s upper to Schapery’s lower bound is observed as volume fraction increases. While the thermophysical properties are quite satisfactory, there is a trade-off to be made in these materials between high thermal conductivity and low CTE on the one side and surface quality and machinability on the other.
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