Showing papers by "Avram Bar-Cohen published in 2013"

Two-Phase Liquid Cooling for Thermal Management of IGBT Power Electronic Module

Abstract: Recent trends including rapid increases in the power ratings and continued miniaturization of semiconductor devices have pushed the heat dissipation of power electronics well beyond the range of conventional thermal management solutions, making control of device temperature a critical issue in the thermal packaging of power electronics. Although evaporative cooling is capable of removing very high heat fluxes, two-phase cold plates have received little attention for cooling power electronics modules. In this work, device-level analytical modeling and system-level thermal simulation are used to examine and compare single-phase and two-phase cold plates for a specified inverter module, consisting of 12 pairs of silicon insulated gate bipolar transistor (IGBT) devices and diodes. For the conditions studied, an R134a-cooled, two-phase cold plate is found to substantially reduce the maximum IGBT temperature and spatial temperature variation, as well as reduce the pumping power and flow rate, in comparison to a conventional single-phase water-cooled cold plate. These results suggest that two-phase cold plates can be used to substantially improve the performance, reliability, and conversion efficiency of power electronics systems.

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

Abstract: 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.

Co-design of micro-fluidic heat sink and thermal through-silicon-vias for cooling of three-dimensional integrated circuit

Abstract: Three-dimensional integrated circuits (3D-ICs) bring about new challenges to chip thermal management because of their high heat densities. Micro-channel-based liquid cooling and thermal through-silicon-vias (TSVs) have been adopted to alleviate the thermal issues in 3D-ICs. Thermal TSV enables higher interlayer thermal conductivity thereby achieving a more uniform thermal profile. Although somewhat effective in reducing temperatures, they are limited by the nature of the heat sink. On the other hand, micro-channel-based liquid cooling is significantly capable of addressing 3D-IC cooling needs, but consumes a lot of extra power for pumping coolant through channels. This study proposes a hybrid 3D-IC cooling scheme which combines micro-channel liquid cooling and thermal TSV with one acting as heat removal agent, whereas the other enabling beneficial heat conduction paths to the micro-channel structures. The experimental results show that the proposed hybrid cooling scheme provides much better cooling capability than using only thermal TSVs, although consuming 56% less cooling power compared with pure micro-channel cooling.

Modified Model for Improved Flow Regime Prediction in Internally-Grooved Tubes

Abstract: The absence of phenomenological insights and accurate flow regime models makes it difficult to predict the improved effectiveness of internally-grooved tubes for two-phase heat transfer. A re-interpretation of available data and flow regime maps is used to suggest that performance improvement is a result of early transition to Annular flow. A modified flow regime map, with a newly-developed Stratified-Wavy to Annular transition criteria for internally-grooved tubes, is shown to increase regime prediction accuracy by 27% relative to the traditional, smooth tube flow regime prediction.Copyright © 2013 by ASME

Dielectric liquid cooling of immersed components

Abstract: Please click here for information on Set 2: Thermal Packaging ToolsThermal and mechanical packaging — the enabling technologies for the physical implementation of electronic systems -- are responsible for much of the progress in miniaturization, reliability, and functional density achieved by electronic, microelectronic, and nanoelectronic products during the past 50 years. The inherent inefficiency of electronic devices and their sensitivity to heat have placed thermal packaging on the critical path of nearly every product development effort in traditional, as well as emerging, electronic product categories.Successful thermal packaging is the key differentiator in electronic products, as diverse as supercomputers and cell phones, and continues to be of pivotal importance in the refinement of traditional products and in the development of products for new applications. The Encyclopedia of Thermal Packaging, compiled in multi-volume sets (Set 1: Thermal Packaging Techniques, Set 2: Thermal Packaging Tools, Set 3: Thermal Packaging Applications, and Set 4: Thermal Packaging Configurations) will provide a comprehensive, one-stop treatment of the techniques, tools, applications, and configurations of electronic thermal packaging. Each of the author-written sets presents the accumulated wisdom and shared perspectives of a few luminaries in the thermal management of electronics.Set 1: Thermal Packaging TechniquesThe first set of the Encyclopedia, Thermal Packaging Techniques, focuses on the technology “building blocks” used to assemble a complete thermal management system and provide detailed descriptions of the underlying phenomena, modeling equations, and correlations, as well as guidance for achieving the optimal designs of individual “building blocks” and their insertion in the overall thermal solution. Specific volumes deal with microchannel coolers, cold plates, immersion cooling modules, thermoelectric microcoolers, and cooling devices for solid state lighting systems, as well as techniques and procedures for the experimental characterization of thermal management components. These “building blocks” are the essential elements in the creation of a complete, cost-effective thermal management system.The four sets in the Encyclopedia of Thermal Packaging will provide the novice and student with a complete reference for a quick ascent on the thermal packaging "learning curve," the practitioner with a validated set of techniques and tools to face every challenge, and researchers with a clear definition of the state-of-the-art and emerging needs to guide their future efforts. This encyclopedia will, thus, be of great interest to packaging engineers, electronic product development engineers, and product managers, as well as to researchers in thermal management of electronic and photonic components and systems, and most beneficial to undergraduate and graduate students studying mechanical, electrical, and electronic engineering. Foreword(s)Foreword (English) (85 KB)Foreword (Japanese) (342 KB)

Flow Regime Transition in Inner Grooved Minichannel Cold Plates for Cooling Hybrid Electric Power Electronics

Abstract: : Forced flow of fluids undergoing phase change in traditional single-phase cold plates is an effective way to manage waste heat removal of vehicle power electronics. Such cold plates come in a variety of standard styles, ranging from circular-tubed cold plates and flat-tube cold plates, to more exotic designs such as louvered and offset fin cold plates. The mechanisms of heat transfer in a two-phase system are different than single-phase, and as such, improvement can be made by custom designing cold plates for two-phase operation. Past research has focused on surface modifications that enhance nucleate boiling, convective vaporization, or both during two-phase operation. The method that has gained the most attention is the use of inner grooved tubes for performance improvement in refrigeration applications. Despite the popularity of inner grooved tubes, the flow mechanisms that deliver performance enhancement are not fully understood. The absence of phenomenological insights and physical models makes it difficult to transition inner grooved tube technology from conventional refrigeration equipment to cold plates. Therefore, understanding the physical mechanisms underpinning two-phase performance enhancement in inner grooved tubes is at the heart of this report.

Anticipatory Thermoelectric Cooling of a Transient Germanium Hotspot

Abstract: On-chip kW-level hotspots have become a significant factor in the thermal design of modern electronic packages Thermoelectric cooling has been shown to be capable of suppressing such hotspots, but it is not yet clear how to best deploy embedded thermoelectric microcoolers for notional hot spot scenarios This paper will present the results of recent work on thermoelectric “self cooling” of transient hotspots A 3-D multi-physics numerical model is used to simulate the spatial and temporal temperature variations associated with a dynamic hotspot on a germanium substrate, for which the hotspot heat flux varies over time The temporal interaction between the hotspot and the thermoelectric microcooler for specified hotspot duty cycle, hotspot heat flux profile, and thermoelectric cooler current profile will be examined Due to the spatial separation between the cooler and the hotspot, the results suggest that anticipatory cooling, with a prescribed current profile, is a critical factor in the efficient removal of a transient hotspotCopyright © 2013 by ASME

Advances in GaN technology and design for active arrays

Abstract: Gallium Nitride HEMT technology has reached the maturity where it is reliably being deployed for both military and commercial applications But, because of its extreme ruggedness, reliable high temperature operation, and high operational RF power density, GaN based amplifiers can offer both new capability and challenges for Phased Array Systems This work will present the basics of GaN technology, amplifier design methodologies and tradeoffs, and comparisons to traditional GaAs technology for use in phased array T/R modules