Thermal characterization of Al2O3 and ZnO reinforced silicone rubber as thermal pads for heat dissipation purposes

Increasing microprocessor performance has historically been accompanied by increasing power and increasing on-chip power density, both of which present a cooling challenge. In this paper, the historical evolution of power is traced and the impact of power and power density on thermal solution designs is summarized. Industrial and academic researchers have correspondingly increased their focus on elucidating the problem and developing innovative solutions in devices, circuits, architectures, packaging and system level heatsinking. Examples of some of the current packaging and system thermal solutions are provided to illustrate the strategies used in their design. This is followed by a brief discussion of some of the future trends in demand and solution strategies that are being developed by academic and industrial researchers to meet these demands. Potential opportunities and limitations with these strategies are reviewed

Cooling a Microprocessor Chip

A Review on efficient thermal management of air- and liquid-cooled data centers: From chip to the cooling system

The past few decades have seen an escalation of power densities in electronic devices, and in particular in microprocessor chips. Together with the continuing trend of reduction in device dimensions this has led to dramatic increase in the thermal issues within electronic circuits. Thermal management is therefore becoming increasingly more critical and fundamental to ensuring that electronic devices operate within their specification. Although a thermal management system may make use of all modes of heat transfer to maintain temperatures within their appropriate limits and to ensure optimum performance and reliability, conductive heat transfer is typically used to spread the heat out from its point of generation and into the extended surface area of a heatsink. To minimise the contact resistance, thermal interface materials (TIMs) are introduced to the joint to fill the air gaps and are an essential part of an assembly when solid surfaces are attached together. This paper will first review the conventional interface materials and then goes on to present a comprehensive review of the emerging state-of-the-art research in the use of carbon nanotube based materials. The paper will also outline the advantages and disadvantages of each TIM category and the factors that need to be considered when selecting an interface material.

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Thermal Interface Materials - A Review of the State of the Art

A memory circuit system and method are provided in the context of various embodiments. In one embodiment, an interface circuit remains in communication with a plurality of memory circuits and a system. The interface circuit is operable to interface the memory circuits and the system for performing various functionality (e.g. power management, simulation/emulation, etc.).

Configurable memory circuit system and method

Current desktop computers typically use fan-heat sinks for cooling the CPU, referred to as active heat sinks. This work seeks to determine the heat rejection limits for such fan-heat sinks, within specific fan and heat sink space limits. A fixed volume, 80 /spl times/ 60 /spl times/ 50 mm is chosen as the limiting dimensions, which includes the fan volume. The present work addresses plane fin heat sinks, on which a typical 60 mm fan is mounted. Both duct flow and impinging flow are considered. Analytically based models are used to predict the optimum geometry (minimum convection resistance) for plane fins with duct and impinging flow configurations. Also assessed are the effects of increased fan speed (up to 25%) and heat sink base size (33% increase) on air-cooling limits in duct and impinging flow. Tests on fan-heat sinks are done to validate the predictions. Optimization is also done for an enhanced (offset-strip) fin geometry in duct flow. The plane fin is found to outperform the enhanced geometry.

Heat rejection limits of air cooled plane fin heat sinks for computer cooling

In some embodiments, a system includes a circuit board, a first chip, and a second chip stacked on the first chip. The first chip is coupled between the circuit board and the second chip, and the first chip includes circuitry to repeats commands the first chip receives to the second chip. Other embodiments are described.

Chip stack with a higher power chip on the outside of the stack

Current desktop computers typically use fan-heat sinks for cooling the CPU, referred to as active heat sinks. This work seeks to determine the heat rejection limits for such fan-heat sinks, within specific fan and heat sink space limits. A fixed volume, 80/spl times/60/spl times/50 mm is chosen as the limiting dimensions, which includes the fan volume. The present work addresses plane fin heat sinks, on which a typical 60 mm fan is mounted. Both duct flow and impinging flow are considered. Analytically based models are used to predict the optimum geometry (minimum convection resistance) for plane fins with duct and impinging flow configurations. Also assessed are the effects of increased fan speed (up to 25%) and heat sink base size (33% increase) on air-cooling limits in duct and impinging flow. Tests on heat sinks are done to validate the predictions. Optimization is also done for an enhanced (offset-strip) fin geometry in duct flow. The plane fin is found to out perform the enhanced geometry.

This manuscript describes a systematic and rational design of an experimental apparatus based on ASTM D-5470 standard for thermal interface resistance measurement of high performance thermal interface materials (TIM). The apparatus is intended to provide measurement of TIM thermal resistance as low as 0.065 K-cm/sup 2//W within 10% experimental uncertainty. The key points addressed are: 1) Apparatus design to obtain accurate measurement of TIM surface temperatures and heat flux, 2) Effects of surface flatness and roughness, and 3) Importance of and methods for surface cleaning. Design criteria are presented for choosing temperature sensors, their installation method, meter-bar material and thickness. The temperature sensors in the meter-bars should be located a sufficient distance from the heaters to ensure uniform heat flux in the thermal sensor region. Cooling plate design specifications, and a method for applying interface pressure are described. Experimental data are presented on a new TIM having 0.058 K-cm/sup 2//W interface resistance with 138 kPa contact pressure, which is lower than commercially available thermal grease and phase change materials.

Apparatus for accurate measurement of interface resistance of high performance thermal interface materials

Plane fin heat sinks, on which a small fan is mounted, are typically used for cooling the CPU in computers. The two most common air-flow configurations are parallel (or duct) flow and impinging flow. A number of analytic, numerical, and semi-empirical models have been published to predict heat sink performance. Most models assume uniform airflow (duct or impinging) at the heat sink inlet. The present work reviews some of the recent and representative models for the two flow configurations. A simple model based on developing laminar flow in rectangular channels is proposed. Experiments were conducted to measure hydraulic and thermal performance of two representative plane fin aluminum heat sinks, one for each flow configuration. The test data are compared with the proposed model for parallel flow and a selected model for impinging flow. A comparison of the proposed duct flow model predictions shows good agreement with the pressure drop and heat transfer data. Similarly good validation of the impinging flow model is established.

M. Saini

Papers

Heat rejection limits of air cooled plane fin heat sinks for computer cooling

Chip stack with a higher power chip on the outside of the stack

Heat rejection limits of air cooled plane fin heat sinks for computer cooling

Apparatus for accurate measurement of interface resistance of high performance thermal interface materials

Validation of models for air cooled plane fin heat sinks used in computer cooling