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

The high power density of emerging electronic devices is driving the transition from remote cooling, which relies on con-duction and spreading, to embedded cooling, which extracts dissipated heat on-site. Two-phase microgap coolers employ the forced flow of dielectric fluids undergoing phase change in a heated channel within or between devices. Such coolers must work reliably in all orientations for a variety of applications (e.g., vehicle-based equipment), as well as in microgravity and high-g for other applications (e.g., spacecraft and aircraft). The lack of acceptable models and correlations for orientation- and gravity-independent operation has limited the use of two-phase coolers in such applications. Previous research has revealed that gravita-tional acceleration plays a diminishing role in establishing flow regimes and transport rates as the channel size shrinks, but there is considerable variation among the proposed microscale criteria and limited research on two-phase flows in low aspect ratio mi-crogap channels. Reliable criteria for achieving orientation- and gravity-independent flow boiling would enable emerging sys-tems to exploit this thermal management technique and streamline the technology development process. As a first step toward understanding the effect of gravity on two-phase microgap flow and transport, in the present effort the authors have studied the effect of evaporator orientation and mass flux on near-saturated flow boiling of HFE7100 in a 1.01 mm tall by 13.0 mm wide by 12.7 mm long microgap channel. Orientation-independence, defined as achieving similar critical heat fluxes, heat transfer coefficients, and flow regimes across evaporator orientations, was achieved for mass fluxes of 400 kg/m2-s and greater. The present results are compared to pub-lished criteria for achieving gravity-independence.

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Orientation Effects in Two-Phase Microgap Flow

Growing interest in germanium solid-state devices is raising concern over the effects of on-chip, micro-scaled, high flux hot spot on the reliability and performance of germanium chips. Current thermal management technology offers few choices for such on-chip hot spot remediation. However, the good thermo-electric properties of single crystal germanium support the development of a novel thermal management approach, relying on thermoelectric self-cooling by an electric current flowing in a thin planar layer on the back of the germanium chip. Use of metal-on-germanium fabrication techniques can yield a very low thermal contact resistance at the micro cooler/chip interface and the current flow can transfer the energy absorbed from a hot spot to the edge of the chip, thus substantially reducing the detrimental effect of thermoelectric heating on the temperature of the active circuitry. In this paper three-dimensional thermo-electric simulations are used to investigate the self-cooling of hot spots on a germanium chip for a wide range of input current, doping concentration, hot spot heat flux, micro cooler size, and germanium chip thickness. Results suggest that localized thermoelectric self-cooling on the germanium chip can significantly reduce the temperature rise resulting from micro-scaled high-flux hot spots.Copyright © 2010 by ASME

Thermoelectric Self-Cooling on Germanium Chip

Minimum mass polymer seawater heat exchanger for lng applications

Conventional techniques for characterization of thermoelectric performance require bringing measurement equipment into direct contact with the thermoelectric device, which is increasingly error prone as device size decreases. Therefore, the novel work presented here describes a non-contact technique, capable of accurately measuring the maximum ΔT and maximum heat pumping of mini to micro sized thin film thermoelectric coolers. The non-contact characterization method eliminates the measurement errors associated with using thermocouples and traditional heat flux sensors to test small samples and large heat fluxes. Using the non-contact approach, an infrared camera, rather than thermocouples, measures the temperature of the hot and cold sides of the device to determine the device ΔT and a laser is used to heat to the cold side of the thermoelectric module to characterize its heat pumping capacity. As a demonstration of the general applicability of the non-contact characterization technique, testing of a thin film thermoelectric module is presented and the results agree well with those published in the literature.

Non-contact method for characterization of small size thermoelectric modules

A three-year collaborative effort initiated by three institutions has resulted in a new paradigm for distance learning in rapidly evolving technology areas, such as electronics packaging. From the start, the team emphasized the use of multi-media technology for creating and disseminating internet delivered, re-configurable, shared modular educational materials. These modules could be used in a stand-alone fashion for re-training, or embedded in existing courses in various curricula. Using these modules, the first offering of a one semester graduate course on thermal design of electronic systems was made during Spring 1999. This included participants not only from the three original universities, but also from the industry and other universities. This course was taught once a week for three hours, live over the internet. In addition, course materials asynchronously available on the web included Power Point slides of the notes, streaming video, computational codes and virtual laboratory tours. During the second offering of this course during Spring 2000, a number of additional features have been implemented, including expanded participation and greater collaboration. This paper will concentrate on the lessons learned from teaching the second generation of this course. Ongoing efforts involving module standardization will also be described.

Avram Bar-Cohen

Papers

Orientation Effects in Two-Phase Microgap Flow

Thermoelectric Self-Cooling on Germanium Chip

Minimum mass polymer seawater heat exchanger for lng applications

Non-contact method for characterization of small size thermoelectric modules

Distance learning in thermal design of electronic systems - the IEEE/NSF project