Review on thermal energy storage with phase change: materials, heat transfer analysis and applications

Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics, solar blind UV photodetectors, solar cells, and sensors with capabilities beyond existing technologies due to its large bandgap. It is usually reported that there are five different polymorphs of Ga2O3, namely, the monoclinic (β-Ga2O3), rhombohedral (α), defective spinel (γ), cubic (δ), or orthorhombic (e) structures. Of these, the β-polymorph is the stable form under normal conditions and has been the most widely studied and utilized. Since melt growth techniques can be used to grow bulk crystals of β-GaO3, the cost of producing larger area, uniform substrates is potentially lower compared to the vapor growth techniques used to manufacture bulk crystals of GaN and SiC. The performance of technologically important high voltage rectifiers and enhancement-mode Metal-Oxide Field Effect Transistors benefit from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. However, the absence of clear demonstrations of p-type doping in Ga2O3, which may be a fundamental issue resulting from the band structure, makes it very difficult to simultaneously achieve low turn-on voltages and ultra-high breakdown. The purpose of this review is to summarize recent advances in the growth, processing, and device performance of the most widely studied polymorph, β-Ga2O3. The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed. Areas where continued development is needed to fully exploit the properties of Ga2O3 are identified.

A review of Ga2O3 materials, processing, and devices

International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and ∼500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The comme...

Low loss dielectric materials for LTCC applications: a review

Rapid increases in the power ratings and continuing miniaturization of power electronic devices have pushed chip heat fluxes well beyond the range of conventional thermal management techniques. The heat flux of power electronic devices for hybrid electric vehicles is currently at the level of 100-200 W/cm2 and is projected to increase to 500 W/cm2 in next generation vehicles. Such high heat fluxes lead to higher and less uniform insulated gate bipolar transistor (IGBT) chip temperature and significantly degrade the device performance and system reliability. Maintaining the maximum temperature below a specified limit, while isothermalizing the surface temperature of the chip, has become a critical issue for thermal management of power electronics. In this paper, a hybrid solid- and liquid-cooling system design, which combines cold plate liquid cooling and TE solid-state cooling, is proposed for thermal management of a 10 × 10 mm IGBT chip. The liquid-cooling cold plate is used for global cooling of the entire IGBT module while the embedded thin-film TE cooler (TEC) is employed for isothermalization of the individual IGBT chip. A detailed package-level 3-D thermal model is developed to explore the potential application of this cooling concept, with the primary attention focused on isothermalization and temperature reduction of IGBT chip associated with variations in TEC sizes, TE materials, applied current on TEC, cooling system designs, working fluid temperature, cold plate cooling capacity, and IGBT chip heat flux. The results demonstrate that the hybrid solid and liquid cooling is a very promising thermal management solution that can eliminate more than 90% of the temperature nonuniformity on the IGBT chip.

Hybrid Solid- and Liquid-Cooling Solution for Isothermalization of Insulated Gate Bipolar Transistor Power Electronic Devices

Driven by shrinking feature sizes, microprocessor “hot-spots” — with their associated high heat flux and sharp temperature gradients — have emerged as the primary “driver” for on-chip thermal management of today’s IC technology. Solid state thermoelectric micro-coolers offer great promise for reducing the severity of on-chip “hot-spots”, but the theoretical cooling potential of these devices, fabricated on the back of the silicon die in an IC package, has yet to be determined. The results of a three-dimensional electro-thermal finite-element modeling study of such a micro-cooler are presented. Attention is focused on the hot-spot temperature reductions associated with variations in micro-cooler geometry, chip thickness, and chip doping concentration, along with the parasitic Joule heating effects from the electrical contact resistance and current flow through the silicon. The modeling results help to define the optimum solid-state cooling configuration and reveal that, for the conditions examined, nearly 80% of the hot-spot temperature rise of 2.5°C can be removed from a 70μm × 70μm, 680W/cm2 hot-spot on a 50μm thick silicon die with a single micro-cooler.Copyright © 2005 by ASME

Thermoelectric Micro-Cooler for Hot-Spot Thermal Management

The lifetime of an actively-cooled light emitting diode (LED)-based luminaire is dependent not only on the junction temperature of LEDs, but also on the reliability of active cooling devices. We propose a novel hierarchical model to assess the lifetime of an actively cooled LED-based luminaire that can provide light output equivalent to a 100 W incandescent lamp. After design considerations for LED-based luminaires with active cooling are discussed, the proposed model is described using component-level sub-physics-of-failure models. The model is implemented to predict the lifetime of a LED-based recessed downlight with synthetic jet cooling. The effects of the time-dependent performance degradation mechanisms of the active cooling device on the lifetime of the luminaire are also discussed.

Hierarchical Life Prediction Model for Actively Cooled LED-Based Luminaire

This keynote lecture will open with a brief review of the primary two-phase flow regimes and their impact on thermal transport phenomena in tubes and channels The Taitel and Dukler flow regime mapping methodology will then be described and applied to the two-phase flow of refrigerants and dielectric liquids in microgap channels The effects of channel diameter, as well as alternative transition criteria, on the prevailing flow regimes in microgaps will be explored along with available criteria for microchannel behavior Available microgap data will then be shown to reflect the dominance of annular flow and to display a characteristic heat transfer coefficient curve in such configurations It is found that the heat transfer coefficients in the low-quality annular flow segment of this locus can be predicted by available, microtube correlations, but that the moderate-quality transition to the axially-decreasing segment occurs at substantially

Modeling and Prediction of Two-Phase Refrigerant Flow Regimes and Heat Transfer Characteristics in Microgap Channels

An experimental study of pool boiling was conducted using cylindrical heater surfaces of platinum, silicon, silicon dioxide, and aluminum oxide. They were immersed in FC-72 and R-113, saturated at 1-a.t.m. pressure. The effects of fluid and surface material on boiling incipience and on the nucleate boiling curve was investigated. A probabilistic representation was used to present the incipience wall superheat values, which scattered widely for ostensibly identical runs. The difference in incipience wall superheat values between those with FC-72 and R-113 was significant, but the surface material effect on boiling incipience was small. The surface material effect was more pronounced in the nucleate boiling regime than on the incipience process. >

Avram Bar-Cohen

Papers

Hybrid Solid- and Liquid-Cooling Solution for Isothermalization of Insulated Gate Bipolar Transistor Power Electronic Devices

Thermoelectric Micro-Cooler for Hot-Spot Thermal Management

Hierarchical Life Prediction Model for Actively Cooled LED-Based Luminaire

Modeling and Prediction of Two-Phase Refrigerant Flow Regimes and Heat Transfer Characteristics in Microgap Channels

Boiling incipience and nucleate boiling heat transfer of highly-wetting dielectric fluids from electronic materials