Showing papers on "Heat sink published in 2003"

Evolution of Microchannel Flow Passages-Thermohydraulic Performance and Fabrication Technology

Abstract: This paper provides a roadmap of development in the thermal and fabrication aspects of microchannels as applied in microelectronics and other high heat-flux cooling applications. Microchannels are defined as flow passages that have hydraulic diameters in the range of 10 to 200 micrometers. The impetus for microchannel research was provided by the pioneering work of Tuckerman and Pease [1] at Stanford University in the early eighties. Since that time, this technology has received considerable attention in microelectronics and other major application areas, such as fuel cell systems and advanced heat sink designs. After reviewing the advancement in heat transfer technology from a historical perspective, the advantages of using microchannels in high heat flux cooling applications is discussed, and research done on various aspects of microchannel heat exchanger performance is reviewed. Single-phase performance for liquids is still expected to be describable by conventional equations; however, the gas flow may...

Power surface mount light emitting die package

Abstract: A light emitting die package includes a substrate, a reflector plate, and a lens. The substrate has traces for connecting an external electrical power source to a light emitting diode (LED) at a mounting pad. The reflector plate is coupled to the substrate and substantially surrounds the mounting pad, and includes a reflective surface to direct light from the LED in a desired direction. The lens is free to move relative to the reflector plate and is capable of being raised or lowered by the encapsulant that wets and adheres to it and is placed at an optimal distance from the LED chip(s). Heat generated by the LED during operation is drawn away from the LED by both the substrate (acting as a bottom heat sink) and the reflector plate (acting as a top heat sink).

LED-based modular lamp

Abstract: A lamp (10) includes an optics module (12) and an electronics module (14, 60, 70). The optics module (10) includes a plurality of LEDs (16) arranged on a printed circuit board (18) and having a plurality of input leads, and a heat sink (22) having a conduit (40) for the input leads. The plurality of LEDs (16) thermally communicate with the heat sink (22). The electronics module (14, 60, 70) is adapted to power the plurality of LEDs (16) through the input leads. The electronics module (14, 60, 70) has a first end (52) adapted to rigidly connect with the heat sink (22), and a selected electrical connector (50, 62, 72) arranged on a second end for receiving electrical power. The electronics module (14, 60, 70) further houses circuitry (80) arranged therewithin for adapting the received electrical power (82) to drive the LEDs (16).

LED lamp heat sink

Abstract: An LED lamp includes an exterior shell that has the same form factor as a conventional incandescent light bulb, such as a PAR type bulb. The LED lamp includes an optical reflector that is disposed within the shell and that directs the light emitted from one or more LEDs. The optical reflector and shell define a space that is used to channel air to cool the device. The LED is mounted on a heat sink that is disposed within the shell. A fan moves air over the heat sink and through the spaced defined by the optical reflector and the shell. The shell includes one or more apertures that serve as air inlet or exhaust apertures. One or more apertures defined by the optical reflector and shell at the opening of the shell can also be used as air exhaust or inlet apertures.

Light energy delivery head

Abstract: A light energy delivery head is provided which, in one aspect, mounts laser diode bars or other light energy emitters in a heat sink block which is adapted to cool both the emitters and a surface of a medium with which the head is in contact and to which it is applying light energy. In another aspect, various retroreflection configurations are provided which optimize retroreflection of back-scattered light energy from the medium. The size of the aperture through which light energy is applied to the medium is also controlled so as to provide a desired amplification coefficient as a result of retroreflection.

Flexible interconnect structures for electrical devices and light sources incorporating the same

Abstract: A flexible interconnect structure (10) allows for rapid dissipation of heat generated from an electrical device that includes light-emitting elements (300), such as light-emitting diodes ('LEDs') and/or laser diodes. The flexible interconnect structure (10) comprises: (1) at least one flexible dielectric film (20) on which circuit traces (40) and, optionally, electrical circuit components (30, 32, 34, 36, 38) are formed and at least a portion of which is removed through its thickness; and (2) at least a heat sink (100) attached to one surface of the flexible dielectric film (20) opposite to the surface on which circuit traces (40) are formed. The flexible interconnect structure can include a plurality of such flexible dielectric films (20), each supporting circuit traces (40) and/or circuit components (30, 32, 34, 36, 38) and each being attached to another by an electrically insulating layer (70). Electrical devices or light sources having complex shapes are formed from such flexible interconnect structures and light-emitting elements (300) attached to the heat sinks (100) so to be in thermal contact therewith.

Evolution of microchannel flow passages – Thermohydraulic performance and fabrication technology

Abstract: This paper provides a roadmap of development in the thermal and fabrication aspects of microchannels as applied in the microelectronics and other high heat-flux cooling applications. Microchannels are defined as flow passages that have hydraulic diameters in the range of 10 to 200 micrometers. The impetus for microchannel research was provided by the pioneering work of Tuckerman and Pease [1] at Stanford University in the early eighties. Since that time, this technology has received considerable attention in microelectronics and other major application areas, such as fuel cell systems and advanced heat sink designs. After reviewing the advancement in heat transfer technology from a historical perspective, advantages of using microchannels in high heat flux cooling applications is discussed, and research done on various aspects of microchannel heat exchanger performance is reviewed. Singlephase performance for liquids is expected to be still describable by the conventional equations; however the gas flow may be influenced by the rarefaction effects. Two-phase flow is another topic that is still under active research. The evolution of research into microchannel heat sinks has paralleled the advancements made in microfabrication technology. The earliest microchannels were built using anisotropic wet chemical etching techniques based on alkali solutions. While this method has been exploited successfully, it does impose certain restrictions on silicon wafer type and geometry. Recently, anisotropic dry etching processes have been developed that circumvent these restrictions. In addition, dry etching methods can be significantly faster and, from a manufacturing standpoint, create fewer contamination and waste treatment problems. Advances in fabrication technology will continue to fuel improvements in microchannel heat sink performance and cost for the foreseeable future. Some fabrication areas that may spur advances include new materials, high aspect ratio patterning techniques other than dry etching, active fluid flow elements, and micromolding NOMENCLATURE

Method and system for cooling electronics racks using pre-cooled air

Abstract: Augmenting air cooling of electronics systems using a cooling fluid to cool air entering the electronics system, and to remove a portion of the heat dissipated by the electronics. A cooled electronics system includes a frame, electronics drawers, fans or air moving devices, and an inlet heat exchanger. A cooling fluid such as chilled water is supplied to the inlet heat exchanger, to cool incoming air below ambient temperature. Fans cause ambient air to enter the system, flow through the inlet heat exchanger, through electronic devices, and exit the system. An optional exhaust heat exchanger further transfers heat dissipated by electronic devices to the cooling fluid. Heat exchangers are pivotally mounted, providing drawer access. Segmented heat exchangers provide access to individual drawers. Heat exchangers are integrated into cover assemblies. Airflow guides such as louvers are provided at inlets and outlets. Cover assemblies provide a degree of acoustic and electromagnetic shielding.

Reduced pumping power and wall temperature in microchannel heat sinks with fractal-like branching channel networks

Abstract: Comparisons are made of the maximum channel wall temperature along, and total pressure drop across, a heat sink with a fractal-like branching channel network with those in a heat sink having a straight channel array. The total channel lengths are identical between the heat sinks, as are the applied heat fluxes. The hydraulic diameter of the straight channel array is equal to that of the terminal branch of the branching channel network. The number of branches per level, number of branching levels, and channel dimensions in the fractal-like network remain fixed. Minor losses are neglected and both hydrodynamic and thermal boundary layers are assumed to reinitiate following each channel bifurcation in the branching flow network. With identical total convective surface areas for both configurations and maintaining a heat sink surface area equal to that of the convective surface area, the fractal-like channel network yielded a 60% lower pressure drop for the same total flow rate and a 30°C lower wall temperatu...

Thermal Spreading Resistance of Eccentric Heat Sources on Rectangular Flux Channels

Abstract: A general solution, based on the separation of variables method for thermal spreading resistances of eccentric heat sources on a rectangular flux channel is presented. Solutions are obtained for both isotropic and compound flux channels. The general solution can also be used to model any number of discrete heat sources on a compound or isotropic flux channel using superposition. Several special cases involving single and multiple heat sources are presented. @DOI: 10.1115/1.1568125#

Light emitting diode bulb having high heat dissipating efficiency

Abstract: A light emitting diode (LED) bulb includes a heat sink, a circuit layer having two opposite sides, multiple LEDs mounted on one side and an electrical insulating layer connected between the opposite side and the heat sink. Heat generated by the LEDs is conducted to the heat sink through the circuit layer and the electrical insulting layer and is dissipated quickly. Further, a fan can be mounted on the fins to dissipate heat from the heat sink more quickly. Therefore, the LED bulb has good heat dissipating efficiency.

Pluggable electronic module and receptacle with heat sink

Abstract: A receptacle assembly includes a guide frame having top, bottom and side walls joined to form an interior cavity configured to receive an electrical module. One of the top, bottom and side walls has an opening therethrough, and a heat sink is mounted over the opening. The heat sink has an engagement surface located proximate the interior cavity of the guide frame, and the engagement surface of the heat sink is configured to physically contact a module when installed in said interior cavity. The heat sink dissipates heat generated in the module and facilitates a data transmission rate of 10 Gbs through the assembly.

Vapor escape microchannel heat exchanger

Abstract: A vapor escape membrane for use in a heat exchanging device, including a heat pipe or heat sink that runs liquid into a cooling region positioned adjacent to the heat producing device, the vapor escape membrane comprising: a porous surface for removing vapor produced from the liquid in the cooling region, the membrane configured to confine the liquid only within the cooling region. The vapor escape membrane transfers vapor to a vapor region within the heat exchanging device, wherein the membrane is configured to prevent liquid in the cooling region from entering the vapor region. The membrane is configured to include a hydrophobic surface between the membrane and the cooling region, wherein the liquid in the cooling region does not flow through the porous surface. The vapor escape membrane includes a plurality of apertures for allowing vapor to transfer therethrough, each of the apertures having a predetermined dimension.

Evaporation Heat Transfer in Sintered Porous Media

Abstract: A two-dimensional model is presented to predict the overall heat transfer capability for a sintered wick structure. The model considers the absence of bulk fluid at the top surface of the wick, heat conduction resistance through the wick, capillary limitation, and the onset of nucleate boiling. The numerical results show that thin film evaporation occurring only at the top surface of a wick plays an important role in the enhancement of evaporating heat transfer and depends on the thin film evaporation, the particle size, the porosity, and the wick structure thickness. By decreasing the average particle radius, the evaporation heat transfer coefficient can be enhanced. Additionally, there exists an optimum characteristic thickness for maximum heat removal. The maximum superheat allowable for thin film evaporation at the top surface of a wick is presented to be a function of the particle radius, wick porosity, wick structure thickness, and effective thermal conductivity. In order to verify the theoretical analysis, an experimental system was established, and a comparison with the theoretical prediction conducted. Results of the investigation will assist in optimizing the heat transfer performance of sintered porous media in heat pipes and better understanding of thin film evaporation.

Least dissipation principle of heat transport potential capacity and its application in heat conduction optimization

Abstract: In the viewpoint of heat transfer, heat transport potential capacity and its dissipation are defined based on the essence of heat transport phenomenon Respectively, their physical meanings are the overall heat transfer capability and the dissipation rate of the heat transfer capacity Then the least dissipation principle of heat transport potential capacity is presented to enhance the heat conduction efficiency in the heat conduction optimization The principle is, for a conduction process with the constant integral of the thermal conductivity over the region, the optimal distribution of thermal conductivity, which corresponds to the highest heat conduction efficiency, is characterized by the least dissipation of heat transport potential capacity Finally the principle is applied to some cases in heat conduction optimization

Semiconductor package with heat sink

Abstract: A semiconductor package with a heat sink is provided in which at least one chip is mounted on the substrate and covered by a heat sink. The heat sink is formed with a plurality of grooves or holes at positions in contact with the substrate, allowing an adhesive material to be applied between the heat sink and the substrate and filled into the grooves or holes for attaching the heat sink onto the substrate. The adhesive material filled into the grooves or holes provides an anchoring effect for firmly positioning the heat sink on the substrate. Therefore, it is not necessary to form predetermined holes on the substrate for being coupled to fixing members such as bolts, and incorporation of the heat sink would not affect trace routability and arrangement of input/output connections such as solder balls on the substrate and would not lead to cracks of the chip.

Optimization study of stacked micro-channel heat sinks for micro-electronic cooling

Abstract: With smaller inlet flow velocity, a micro-channel stack requires less pumping power to remove a certain rate of heat than a single-layered micro-channel, because it provides a larger heat transfer area. A simple thermal resistance network model was developed to evaluate the overall thermal performance of a stacked micro-channel heat sink. Based on this simple model, in this study, a single objective minimization of overall thermal resistance is carried out using genetic algorithms. The aspect ratio, fin thickness and the ratio of channel width to fin thickness are the variables to be optimized, subject to constraints of maximum pressure drop (4 bar) and maximum volumetric flow rate (1000 ml/min). During the optimization, the overall dimensions, number of layers and pumping power (product of pressure drop and flow rate) are fixed. The study indicates that reduction in thermal resistance can be achieved by optimizing the channel configuration. The effects of number of layers in the stack, pumping power per unit area, and the channel length are also investigated.

Interwoven manifolds for pressure drop reduction in microchannel heat exchangers

Abstract: A microchannel heat exchanger coupled to a heat source and configured for cooling the heat source comprising a first set of fingers for providing fluid at a first temperature to a heat exchange region, wherein fluid in the heat exchange region flows toward a second set of fingers and exits the heat exchanger at a second temperature, wherein each finger is spaced apart from an adjacent finger by an appropriate dimension to minimize pressure drop in the heat exchanger and arranged in parallel. The microchannel heat exchanger includes an interface layer having the heat exchange region. Preferably, a manifold layer includes the first set of fingers and the second set of fingers configured within to cool hot spots in the heat source. Alternatively, the interface layer includes the first set and second set of fingers configured along the heat exchange region.

Low voltage drop and high thermal performance ball grid array package

Abstract: An apparatus and method for a low voltage drop and thermally enhanced integrated circuit (IC) package are described. A substantially planar substrate having a plurality of contact pads on a first surface is electrically connected through the substrate to a plurality of solder ball pads on a second surface of the substrate. An IC die having a first surface is mounted to the first surface of the substrate. The IC die has a plurality of I/O pads electrically connected to the plurality of contact pads on the first surface of the substrate. A heat sink assembly is coupled to a second surface of the IC die and to a first contact pad on the first surface of the substrate to provide a thermal path from the IC die to the first surface of the substrate. The heat sink assembly can also provide an electrical path from the IC die to the first surface of the substrate. The heat sink assembly may have one or two heat sink elements to provide thermal and/or electrical connectivity between the IC die and the substrate.

Thermal management system and method for electronics system

Abstract: A thermal energy management system is provided having a heat spreading device that is operatively engaged with at least one semiconductor chip and a thermal bus operatively engaged with the heat spreading device so as to transport thermal energy from the heat spreading device to a heat sink. The heat spreading device includes a heat pipe and the thermal bus includes a loop thermosyphon. A second thermal bus may be operatively engaged with the first thermal bus so as to transport thermal energy from the first thermal bus to a heat sink. The second thermal bus may also include a loop thermosyphon. A method of managing thermal energy in an electronic system is also provided that includes spreading thermal energy generated by one or more devices over a surface that is relatively larger than the devices, thermally coupling an evaporator portion of a loop thermosyphon to the surface, and thermally coupling a condensing portion of the loop thermosyphon to a thermal energy sink, e.g., a second loop thermosyphon, convection fin, or cold plate.

Thermal measurments of electronic devices during operation

Abstract: A system and method for measuring thermal distributions of an electronic device during operation is disclosed. The system includes an electronic device, a heat sink adjacent to the electronic device and an electrical-insulating layer disposed on the electronic device so as to separate the electronic device and the heat sink. The system further includes a plurality of thermal sensors located on the electrical-insulating layer, each of the plurality of thermal sensors in a different location. The plurality of thermal sensors is located within one or more thin film circuit layers disposed adjacent to the electrical insulating layer. The system further includes a module for receiving thermal information from the plurality of thermal sensors during operation of the electronic device. The system further includes a processor coupled to the module for generating a thermal distribution of the electronic device based on the thermal information received from the plurality of thermal sensors.

Method and apparatus for achieving temperature uniformity and hot spot cooling in a heat producing device

Abstract: A method of controlling temperature of a heat source in contact with a heat exchanging surface of a heat exchanger, wherein the heat exchanging surface is substantially aligned along a plane. The method comprises channeling a first temperature fluid to the heat exchanging surface, wherein the first temperature fluid undergoes thermal exchange with the heat source along the heat exchanging surface. The method comprises channeling a second temperature fluid from the heat exchange surface, wherein fluid is channeled to minimize temperature differences along the heat source. The temperature differences are minimized by optimizing and controlling the fluidic and thermal resistances in the heat exchanger. The resistances to the fluid are influenced by size, volume and surface area of heat transferring features, multiple pumps, fixed and variable valves and flow impedance elements in the fluid path, pressure and flow rate control of the fluid, and other factors.

Light emitting diode, light emitting device using the same, and fabrication processes therefor

Abstract: Disclosed is a LED which can be mounted at high density on a large area display. Having a hole for heat sink in the ceramic substrate, the LED is superior in heat sink property. In order to fabricate the light emitting device, first, a secondary ceramic sheet is stacked on the ceramic substrate, followed by forming electrodes in a predetermined pattern on the secondary ceramic sheet around the hole for heat sink. On the ceramic substrate, an upper ceramic sheet with an opening is stacked to form a stacked ceramic substrate in such a way that a part of the electrodes are exposed through the opening. After co-firing the stacked ceramic substrate, a light emitting diode chip is mounted on the secondary ceramic sheet at a position corresponding to the hole for heat sink. Then, the electrodes are electrically connected with the LED chip, and the LED chip is sealed with insulating resin. A light emitting device using the LED and a fabrication method therefor are also disclosed.