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

In low-cost integrated circuit (IC) packaging, a thin layer of adhesive is often used to bond the die to a leadframe or substrate. Because of the poor thermal conductivity of the adhesive, a thick layer will result in elevated chip temperatures. However, due to the differential expansion between the silicon and metal, a thin layer will result in high shear stress, in the adhesive, and along the bonded surfaces. In this study, first order thermal and thermostructural analytical relations for shear stress are used to determine the appropriate thickness of the adhesive layer between a die and a leadframe paddle, as encountered in PDIP packages. Numerical simulation, with finite element (FE) models, is used to examine the assumptions underpinning the analytical relations and to verify the analytical results. Using a filled-epoxy with an adhesion strength of 25 MPa, adhesive layer thicknesses between 0.027 and 0.2 mm are found to be suitable for this application. Assuming equal loss of reliability, due to chip temperature increases and shear stress increases, an optimum die-bond thickness of 0.16 mm is found. The FE computations appear to support the assumption that elevated shear stress is the most likely cause of die-bond structural failure for this subject package. >

A shear based optimization of adhesive thickness for die bonding

Effect of a dimensionless length scale on the critical heat flux in saturated, pool boiling

Thermal performance of a polymer composite webbed-tube heat exchanger

Thermal transport mechanisms in nucleate pool boiling of highly-wetting liquids

Thermal interface materials (TIMs) are an important enabler for low thermal resistance and reliable electronics packaging for a wide array of applications. There is a trend towards bonded interface materials (BIMs) because of their potential for low thermal resistance (<;1 mm
 2
-K/W). However, due to coefficient of thermal expansion mismatches between various layers of a package, thermomechanical stresses are induced in BIMs and the package can be prone to failures and integrity risks. Deteriorated interfaces can result in high thermal resistance in the package and degradation and/or failure of the electronics. The Defense Advanced Research Projects Agency's (DARPA) Thermal Management Technologies (TMT) Program has addressed this challenge, supporting the development of mechanically compliant, low resistivity nano-thermal interface (NTI) materials. Prior development of these materials resulted in samples that met DARPA's initial thermal performance and synthesis metrics. In this present work, we describe the testing procedure and report the results of thermal performance and reliability characterization of an initial sample set of three different NTI-BIMs tested at the National Renewable Energy Laboratory.

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Avram Bar-Cohen

Papers

A shear based optimization of adhesive thickness for die bonding

Effect of a dimensionless length scale on the critical heat flux in saturated, pool boiling

Thermal performance of a polymer composite webbed-tube heat exchanger

Thermal transport mechanisms in nucleate pool boiling of highly-wetting liquids

Thermal performance and reliability characterization of bonded interface materials (BIMs)