Showing papers on "Heat sink published in 2006"

Effect of nanofluid on the heat transport capability in an oscillating heat pipe

Abstract: By combining nanofluids with thermally excited oscillating motion in an oscillating heat pipe (OHP), we developed an ultrahigh-performance cooling device, called the nanofluid oscillating heat pipe. Experimental results show that when the OHP is charged with nanofluid, heat transport capability significantly increases. For example, at the input power of 80.0W, diamond nanofluid can reduce the temperature difference between the evaporator and the condenser from 40.9to24.3°C. This study will accelerate the development of a highly efficient cooling device for ultrahigh-heat-flux electronic systems.

Cracking and deposition behavior of supercritical hydrocarbon aviation fuels

Abstract: Trends in increasing aircraft speeds and engine efficiencies are increasing vehicle and engine heat loads. Especially at higher Mach numbers, fuel is an attractive heat sink. For many vehicle applications, utilization of this heat sink would increase fuel temperatures beyond critical values, typically 370–400°C (700–750°F). As temperatures increase beyond about 480°C (900°F), this heat addition can lead to thermal/catalytic cracking of the fuel, leading to an “endothermic” fuel. The principal barrier to the use of high temperature fuels is the deposition of carbonaceous material on heat exchanger passages, filters, fuel injectors, and other fuel system components. This paper will review progress in understanding and mitigating the thermal instability/deposition problem.

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

Abstract: 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.

Effect of the joule heating on the quantum efficiency and choice of thermal conditions for high-power blue InGaN/GaN LEDs

Abstract: The heat model of a light-emitting diode (LED) with an InGaN/GaN quantum well (QW) in the active region is considered. Effects of the temperature and drive current, as well as of the size and material of the heat sink on the light output and efficiency of blue LEDs are studied. It is shown that, for optimal heat removal, decreasing of the LED efficiency as current increases to 100 mA is related to the effect of electric field on the efficiency of carrier injection into the QW. As current further increases up to 400 mA, the decrease in efficiency is caused by Joule heating. It is shown that the working current of LEDs can be increased by a factor of 5–7 under optimal heat removal conditions. Recommendations are given on the cooling of LEDs in a manner dependent on their power.

Nanoscale Thermal Transport and Microrefrigerators on a Chip

Abstract: In this paper we review recent advances in nanoscale thermal and thermoelectric transport with an emphasis on the impact on integrated circuit (IC) thermal management. We will first review thermal conductivity of low-dimensional solids. Experimental results have shown that phonon surface and interface scattering can lower thermal conductivity of silicon thin films and nanowires in the sub-100-nm range by a factor of two to five. Carbon nanotubes are promising candidates as thermal vias and thermal interface materials due to their inherently high thermal conductivities of thousands of W/mK and high mechanical strength. We then concentrate on the fundamental interaction between heat and electricity, i.e., thermoelectric effects, and how nanostructures are used to modify this interaction. We will review recent experimental and theoretical results on superlattice and quantum dot thermoelectrics as well as solid-state thermionic thin-film devices with embedded metallic nanoparticles. Heat and current spreading in the three-dimensional electrode configuration, allow removal of high-power hot spots in IC chips. Several III-V and silicon heterostructure integrated thermionic (HIT) microcoolers have been fabricated and characterized. They have achieved cooling up to 7 degC at 100 degC ambient temperature with devices on the order of 50 mum in diameter. The cooling power density was also characterized using integrated thin-film heaters; values ranging from 100 to 680 W/cm2 were measured. Response time on the order of 20-40 ms has been demonstrated. Calculations show that with an improvement in material properties, hot spots tens of micrometers in diameter with heat fluxes in excess of 1000 W/cm2 could be cooled down by 20 degC-30 degC. Finally we will review some of the more exotic techniques such as thermotunneling and analyze their potential application to chip cooling

Thermal-hydraulic performance of MEMS-based pin fin heat sink

Abstract: An experimental study on heat transfer and pressure drop of de-ionized water over a hank of shrouded staggered micro pin fins 243 μm long with hydraulic diameter of 99.5 μm has been performed. Average heat transfer coefficients have been obtained for effective heat fluxes ranging from 3.8 to 167 W/cm 2 and Reynolds numbers from 14 to 112. The results were used to derive the Nusselt numbers, total thermal resistances, and friction factors. It has been found that for Reynolds numbers below ∼50 long tube correlations overpredicted the experimental Nusselt number, while at higher Reynolds numbers existing correlations predicted the results moderately well. Endwall effects, which diminish at high Reynolds numbers, and a delay in flow separation for compact pin fins were attributed to the obtained trend.

Extended surface heat transfer

Abstract: • Increase the temperature difference (Ts-T) between the surface and the fluid. • Increase the convection coefficient h. This can be accomplished by increasing the fluid flow over the surface since h is a function of the flow velocity and the higher the velocity, the higher the h. Example: a cooling fan. • Increase the contact surface area A. Example: a heat sink with fins. Many times, when the first option is not in our control and the second option (i.e. increasing h) is already stretched to its limit, we are left with the only alternative of increasing the effective surface area by using fins or extended surfaces. Fins are protrusions from the base surface into the cooling fluid, so that the extra surface of the protrusions is also in contact with the fluid. Most of you have encountered cooling fins on air-cooled engines (motorcycles, portable generators, etc.), electronic equipment (CPUs), automobile radiators, air conditioning equipment (condensers) and elsewhere.

Lateral temperature equalizing system for large area surfaces during processing

Abstract: In many processes used in fabricating semiconductors the wafer is seated on the top surface of a pedestal and heated in a high energy process step, such as plasma etching. The pedestal, chuck or platen may be cooling but the wafer gradually heats until the process can no longer continue. Where large, e.g. 300 mm diameter, wafers are being processed the temperature level across the wafer is difficult to maintain substantially constant. In this system and method the lateral temperature distribution is equalized by a heat sink structure in a chamber immediately under the wafer support on top of the pedestal. A number of spatially distributed wicking posts extend downwardly from a layer of wicking material across the top of the chamber, into a pool of a vaporizable liquid. At hot spots, vaporized liquid is generated and transported to adjacent condensation posts extending up from the liquid. The system thus passively extracts heat to equalize temperatures while recirculating liquid and assuring adequate supply. The free volume above and within the liquid, and the short distances between posts, assure adequate heat transfer rates.

Thermal analysis of a 3D die-stacked high-performance microprocessor

Abstract: 3-dimensional integrated circuit (3D IC) technology places circuit blocks in the vertical dimension in addition to the conventional horizontal plane. Compared to conventional planar ICs, 3D ICs have shorter latencies as well as lower power consumption, due to shorter wires. The benefits of 3D ICs increase as we stack more die, due to successive reductions in wire lengths. However, as we stack more die, the power density increases due to increasing proximity of active (heat generating) devices, thus causing the temperatures to increase. Also, the topmost die on the 3D stack are located further from the heat sink and experience a longer heat dissipation path. Prior research has already identified thermal management as a critical issue in 3D technology. In this paper, we evaluate the thermal impact of building high-performance microprocessors in 3D. We estimate the temperatures of a planar IC based on the Alpha 21364 processor as well as 2-die and 4-die 3D implementations of the same. We show that, compared to the planar IC, the 2-die implementation and 4-die implementation increase the maximum temperature by 17 Kelvin and 33 Kelvin, respectively.

Heat dissipating LED signal lamp source structure

Abstract: A heat dissipating LED signal lamp emitting structure includes an isothermal board, a light emitting unit on the isothermal board, a heat conducting cylinder connected to the bottom of the isothermal board, a heat dissipating body around the periphery of the heat conducting cylinder and comprised of heat sinks, a circular cover body above the isothermal board for covering the isothermal board, a reflecting groove at the center of the cover body for passing through the light emitting unit, and a transparent lid on the cover body for covering the light emitting unit. With the heat dissipating effect of the heat dissipating body, the operating heat produced by the light emitting unit can be dissipated to the outside. The invention not only uses a single light emitting unit as a signal lamp emitting source, but also enhances the light emitting efficiency and the life expectancy of the light emitting unit.

Method and apparatus for cooling a lightbulb

Abstract: A device has a plurality of light emitting diodes (LEDs), heat conducting structure that includes a heat pipe and that carries heat from the region of the LEDs to a further location spaced therefrom, and heat dissipating structure that accepts heat from the heat conducting structure at the further location and that discharges the heat externally of the device. In a different embodiment, a device has a radiation generator, a thermal spreader that receives heat emitted by the radiation generator, heat conducting structure that carries heat from the thermal spreader to a location spaced therefrom, and heat dissipating structure that accepts heat at the location from the heat conducting structure and that discharges the heat externally of the device.

Mounting arrangement for light emitting diodes

Abstract: A modular light emitting diode (LED) mounting configuration is provided including a light source module having a plurality of pre-packaged LEDs arranged in a serial array. The module includes a heat conductive body portion adapted to conduct heat generated by the LEDs to an adjacent heat sink. As a result, the LEDs are able to be operated with a higher current than normally allowed. Thus, brightness and performance of the LEDs is increased without decreasing the life expectancy of the LEDs. The LED modules can be used in a variety of illumination applications employing one or more modules.

System for heat treatment of semiconductor device

Abstract: Disclosed is a heat treatment system for semiconductor devices. The heat treatment system is used in a heat treatment process for semiconductor devices, such as a crystallization process for an amorphous silicon thin film or a dopant activation process for a poly-crystalline silicon thin film formed on a surface of a glass substrate of a flat display panel including a liquid crystal display (LCD) or an organic light emitting device (OLED). The heat treatment system transfers a semiconductor device after uniformly preheating the semiconductor device in order to prevent deformation of the semiconductor device during the heat treatment process, rapidly performs the heat treatment process under the high temperature condition by heating the semiconductor device using a lamp heater and induction heat derived from induced electromotive force, and unloads the semiconductor device after uniformly cooling the semiconductor device such that the semiconductor device is prevented from being deformed when the heat treatment process has been finished. The heat treatment system rapidly performs the heat treatment process while preventing deformation of the semiconductor device by gradually heating or cooling the semiconductor device.

On-Chip Thermal Management With Microchannel Heat Sinks and Integrated Micropumps

Abstract: Liquid-cooled microchannel heat sinks are regarded as being amongst the most effective solutions for handling high levels of heat dissipation in space-constrained electronics However, obstacles to their successful incorporation into products have included their high pumping requirements and the limits on available space which precludes the use of conventional pumps Moreover, the transport characteristics of microchannels can be different from macroscale channels because of different scaling of various forces affecting flow and heat transfer The inherent potential of microchannel heat sinks, coupled with the gaps in understanding of relevant transport phenomena and difficulties in implementation, have guided significant research efforts towards the investigation of flow and heat transfer in microchannels and the development of microscale pumping technologies and novel diagnostics In this paper, the potential and capabilities of microchannel heat sinks and micropumps are discussed Their working principle, the state of the art, and unresolved issues are reviewed Novel approaches for flow field measurement and for integrated micropumping are presented Future developments necessary for wider incorporation of microchannel heat sinks and integrated micropumps in practical cooling solutions are outlined

Advanced heat sinks and thermal spreaders

Abstract: A heat sink assembly for an electronic device or a heat generating device(s) is constructed from an ultra-thin graphite layer. The ultra-thin graphite layer exhibits thermal conductivity which is anisotropic in nature and is greater than 500 W/m° C. in at least one plane and comprises at least a graphene layer. The ultra-thin graphite layer is structurally supported by a layer comprising at least one of a metal, a polymeric resin, a ceramic, and a mixture thereof, which is disposed on at least one surface of the graphite layer.

Memory module assembly including a clip for mounting a heat sink thereon

Abstract: A memory module assembly includes a printed circuit board ( 10 ) having a heat-generating electronic component ( 14 ) thereon, and first and second heat-dissipation plates ( 20 ), ( 30 ) attached on opposite sides of the printed circuit board. The first heat-dissipation plate includes a first hook ( 24 ) extending from a side thereof and the first hook includes a resisting portion ( 242 ) extending from an end of the first heat-dissipation plate and a first engaging portion ( 244 ) extending from a free end of the resisting portion for resisting the printed circuit board and the second heat-dissipation plate. The second heat-dissipation plate defines a depressed portion ( 34 ) in a side thereof for engaging with the first hook. The other sides of the first and second heat-dissipation plates engage with each other to clamp the printed circuit board between the first and second heat-dissipation plates.

LED-based luminaire

Abstract: An LED-based luminaire includes a driver configured to convert line voltage into a desired power configuration. Elongate fasteners attach one or more LED-based lighting modules to a mount member and also to energized poles of the power driver. The fasteners communicate electrical energy from the power driver to the lighting module. In one embodiment, the mount member functions as a heat sink, and it includes a bumpy surface coating having a texture with sufficient feature heights to enhance heat transfer between the heat sink and the surrounding environment.

Ultrasound transducer assembly having improved thermal management

Abstract: An improved thermal management of an ultrasound transducer assembly is provided. The ultrasound transducer assembly includes an ultrasound transducer operable to transmit ultrasound energy along a propagation path; and a self-contained cooling system thermally coupling the ultrasound transducer to at least one heat sink. The self- contained cooling system includes at least one heat transfer member. The self-contained cooling system defines a heat flow from the ultrasound transducer assembly to the heat sink via the at least one heat transfer member. The propagation path of the ultrasound energy is opposite in direction to the heat flow path. The heat transfer process is augmented by the addition of a thermoelectric cooler positioned in thermal communication with the ultrasound transducer assembly. The self-contained cooling system provides for minimum thermal resistance, while the thermoelectric cooler maintains the heat flow in a positive direction and maintains positive thermal gradients thus enhancing the heat flow to the heat sink.

Flash Heating in Atomic Layer Deposition

Abstract: System and methods for flash heating of materials deposited using atomic layer deposition techniques are disclosed. By flash heating the surface of the deposited material after each or every few deposition cycles, contaminants such as un-reacted precursors and byproducts can be released from the deposited material. A higher quality material is deposited by reducing the incorporation of impurities. A flash heating source is capable of quickly raising the temperature of the surface of a deposited material without substantially raising the temperature of the bulk of the substrate on which the material is being deposited. Because the temperature of the bulk of the substrate is not significantly raised, the bulk acts like a heat sink to aid in cooling the surface after flash heating. In this manner, processing times are not significantly increased in order to allow the surface temperature to reach a suitably low temperature for deposition.

Hot spot cooling using embedded thermoelectric coolers

Abstract: Localized areas of high heat flux on microprocessors produce hot spots that limit their reliability and performance. With increasingly dense circuits and the integration of high power processors with low power memory, non-uniform thermal profiles will become more dramatic and difficult to manage. Chip scale thermal solutions designed to keep hot spots below a critical temperature unnecessarily overcool the rest of the CPU and add to heat-sink load. Localized hot spot cooling solutions, even active systems that contribute some additional heat, can do a better job controlling hot spot temperatures when efficiently integrated with a heat spreader. Embedded thermoelectric cooling (eTEC) is a promising approach to reduce the temperature of highly localized, high heat flux hot spots generated by today's advanced processors

Geometric optimization of a micro heat sink with liquid flow

Abstract: Over the course of the past decade, a number of investigations have been conducted to better understand the fluid flow and heat transfer in microchannel heat sinks, particularly as it pertains to applications involving the thermal control of electronic devices. In the current investigation, a detailed numerical simulation of the heat transfer occurring in silicon-based microchannel heat sinks has been conducted in order to optimize the geometric structure using a simplified, three-dimensional (3-D) conjugate heat transfer model [two-dimensional (2-D) fluid flow and 3-D heat transfer]. The micro heat sink modeled in this investigation consists of a 10 mm long silicon substrate with rectangular microchannels fabricated with different geometries. The rectangular microchannels had widths ranging from 20 /spl mu/m to 220 /spl mu/m and a depth ranging from 100 /spl mu/m to 400 /spl mu/m. The effect of the microchannel geometry on the temperature distribution in the microchannel heat sink is presented and discussed assuming a constant pumping power. The model was validated by comparing the predicted results with previously published experimental results and theoretical analyses, and indicated that both the physical geometry of the microchannel and the thermophysical properties of the substrate are important parameters in the design and optimization of these microchannel heat sinks. For the silicon-water micro heat sink, the optimal configuration for rectangular channel heat sinks occurred when the number of channels approached 120 channels per centimeter.