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

Adhesives used in electronic applications are subject to high cyclic shear stresses resulting from differential thermal expansion of the bonded materials. In this study, an attempt has been made to experimentally determine the dependence of the fatigue life of two packaging epoxy adhesives on: temperature, peak cycling stress as a fraction of adhesion strength, and cyclic frequency. Both epoxies were used to bond surfaces of aluminum and silicon. Tensile lap-shear specimens were used.

Parametric dependence of fatigue of electronic adhesives

An integrated measurement technique is proposed to measure the effective chemical shrinkage and the modulus of polymeric materials simultaneously, as a function of time, during polymerization (evolution history). The method is based on a fiber Bragg grating (FBG) sensor. A polymer is cured around a glass FBG and the Bragg wavelength (BW) shift is continuously documented while polymerization progresses at the curing temperature. Based on the theoretical relationship between the BW shift and the stress field in the FBG, the measured BW shift is used to determine the evolving effective chemical shrinkage and the modulus. The results can be employed to predict curing-induced residual stresses in geometrically-complex packaged assemblies. The proposed method is implemented on a high temperature curing epoxy.

Simultaneous measurements of effective chemical shrinkage and modulus evolution during polymerization

Finite element simulation of strain/stress fields in delaminated plastic IC packages

The successful design of plastic integrated circuit packages for high performance VLSI chips is a crucial element in the development of costeffective packaging technology. Unfortunately, however, most common plastic encapsulating and die-bonding materials provide relatively low thermal conductivities and large thermal expansion coefficients, as well as low mechanical strengths and a limited operating temperature range. These material properties combine to produce a large number of thermally induced package failure modes. Thus, insightful material selection and detailed design, based on extensive thermal modeling/analysis, must be performed to achieve acceptable levels of component reliability. p]This paper begins with a discussion of the temporal development of the temperature fields inside a plastic IC package and continues with the presentation of transient and steady-state, first-order analytical models for: the chip temperature, the temperature and gradient across the die bond, and the half-thickness encapsulant temperature. The values obtained for a typical PDIP package are discussed and compared to the results of a finite-element analysis of this package. The insights obtained from these analyses are used to develop material Figures-of-Merit that can be used in the selection of die-bond and encapsulant materials for plastic IC packages.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400522520

Thermal Modeling of Plastic Ic Packages

As thermal management techniques for 3D chip stacks and other high power density electronic packages continue to evolve, interest in the thermal pathways across substrates containing a multitude of conductive vias has increased. To facilitate the use of numerical models that can reduce computational costs and time in the thermal analysis of through-layer via (TXV) structures, much research to date has focused on defining effective anisotropic thermal properties for a pseudo-homogeneous TXV medium using isothermal boundary conditions. While such an approach eliminates the need to model heat flow through individual vias, the resulting properties can be shown to depend on the specific boundary conditions applied to a unit TXV cell. More specifically, effective properties based on isothermal boundary conditions fail to capture the local “micro-spreading” resistance associated with more realistic heat flux distributions and local hot spots on the surface of these substrates.This work assesses how the thermal spreading resistance present in arrays of vias in interposers, substrates, and other package components can be properly incorporated into the modeling of these arrays. We present the conditions under which spreading resistance plays a major role in determining the thermal characteristics of a via array and propose methods by which designers can both account for the effects of spreading resistance and mitigate its contribution to the overall thermal behavior of such substrate-via systems. Finite element modeling of TXV unit cells is performed using commercial simulation software (ANSYS).Compactly stated, micro-spreading contributes to the total resistance RT = R1d + (fu + fl)Rsp,max, where 0≤ f ≤ 1 are adjustment factors that depend on the conditions at the upper and lower surfaces of the via array layer and Rsp,max occurs under worst-case conditions.Copyright © 2015 by ASME

Avram Bar-Cohen

Papers

Parametric dependence of fatigue of electronic adhesives

Simultaneous measurements of effective chemical shrinkage and modulus evolution during polymerization

Finite element simulation of strain/stress fields in delaminated plastic IC packages

Thermal Modeling of Plastic Ic Packages

Modeling Thermal Spreading Resistance in Via Arrays