Showing papers on "Heat sink published in 1996"

Attachment assembly for integrated circuits

Abstract: An integrated circuit package has a top die attach area and a bottom heat spreader thermally coupled to the die for conducting heat generated by the die through a thermal interface in the main circuit board to a heat sink or heat pipe mounted underneath the main circuit board. The preferred thermal interface is a thin, thermally conductive slug mounted through an opening formed in the main circuit board. The heat spreader spans the bottom surface of the integrated circuit package substantially parallel to the main circuit board and preferably extends substantially to the inner periphery of the pin arrangement which preferably, although not exclusively, is in a ball grid array. The opening formed in the main circuit board through which the thin, thermally conductive slug is fitted, is preferably substantially flush with the bottom surface of the main circuit board and juxtaposed against the heat spreader. A thermally conductive adhesive is preferably applied to the adjoining surfaces of the heat spreader and the slug.

Natural Convection as a Heat Engine: A Theory for CAPE

Abstract: On many planets there is a continuous heat supply to the surface and a continuous emission of infrared radiation to space by the atmosphere. Since the heat source is located at higher pressure than the heat sink, the system is capable of doing mechanical work. Atmospheric convection is a natural heat engine that might operate in this system. Based on the heat engine framework, a simple theory is presented for atmospheric convection that predicts the buoyancy, the vertical velocity, and the fractional area covered by either dry or moist convection in a state of statistical equilibrium. During one cycle of the convective heat engine, heat is taken from the surface layer (the hot source) and a portion of it is rejected to the free troposphere (the cold sink) from where it is radiated to space. The balance is transformed into mechanical work. The mechanical work is expended in the maintenance of the convective motions against mechanical dissipation. Ultimately, the energy dissipated by mechanical friction is transformed into heat. Then, a fraction of the dissipated energy is radiated to space while the remaining portion is recycled by the convecting air parcels. Increases in the fraction of energy dissipated at warmer temperature, at the expense of decreases in the fraction of energy dissipated at colder temperatures, lead to increases in the apparent efficiency of the convective heat engine. The volume integral of the work produced by the convective heat engine gives a measure of the statistical equilibrium amount of convective available potential energy (CAPE) that must be present in the planet's atmosphere so that the convective motions can be maintained against viscous dissipation. This integral is a fundamental global number qualifying the state of the planet in statistical equilibrium conditions. For the earth's present climate, the heat engine framework predicts a CAPE value of the order of 1000 J kg^−1 for the tropical atmosphere. This value is in agreement with observations. It also follows from our results that the total amount of CAPE present in a convecting atmosphere should increase with increases in the global surface temperature (or the atmosphere's opacity to infrared radiation).

System and method for thermal processing of a semiconductor substrate

Abstract: A semiconductor substrate processing system and method using a stable heating source with a large thermal mass relative to conventional lamp heated systems. The system dimensions and processing parameters are selected to provide a substantial heat flux to the wafer while minimizing heat loss to the surrounding environment (particularly from the edges of the heat source and wafer). The heat source provides a wafer temperature uniformity profile that has a low variance across temperature ranges at low pressures. A resistively heated block is substantially enclosed within an insulated vacuum cavity used to heat the wafer. A vacuum region is preferably provided between the heated block and the insulating material as well as between the insulating material and the chamber wall. Heat transfer across the vacuum regions is primarily achieved by radiation, while heat transfer through the insulating material is achieved by conduction. The wafer is placed on or near the heated block within the vacuum cavity for heating by conduction and radiation. The rate of heating may be controlled by varying pressure across a range of very low pressures.

Electrical Heating With Horizontal Wells, The Heat Transfer Problem

Abstract: It is desirable to introduce heat into the production system and reservoir of a horizontal well producing heavy oil. An increase in temperature around the wellbore can remove thermally alterable skin effects, increase the productive length of the well, improve pumping efficiency, and reduce the energy requirements to lift the oil to surface. One way to create the heat is to use electricity. The heat transfer problem consists of solving several concurrent mechanisms. The horizontal well is constructed from commercial grade carbon steel pipe which is an electrically conducting ferromagnetic material. Therefore the heat losses within the horizontal well liner are generated by both ohmic, I 2 R and hysteresis effects. Heat is also electrically produced in the reservoir adjacent to the horizontal well by ohmic losses. To further complicate the heat transfer problem, heat is produced from the reservoir with the fluids and conducted from the well by the action of thermal conduction. In summary, the heat transfer problem consists of distributed heat sources in regions where there is current flow, convection, and conduction. The objective of this paper is to present a semi-analytical model that can be used to calculate the temperature distribution along the length of a horizontal well that is being electrically heated. The analytical model can be used to determine a safe operating strategy based upon the resulting temperature distribution for a given operating current and fluid production rate. From the magnitude of the current, the size of the power supply system can be specified and the energy costs for electrically heating a horizontal well can be calculated. It is found that for a long horizontal well, heat transfer to the adjacent reservoir by conduction is more significant than heat transfer by convection and electrical heating. It is also found that the safe operating magnitude of the current in the horizontal well, determined by the allowable temperature rise, is limited by the cooling effect of produced fluids. Also, the energy costs to heat the well are relatively small in comparison to other operating costs.

Thermal state of the Taranaki Basin, New Zealand

Abstract: The Taranaki Basin is an active-margin basin that has been significantly affected by Miocene subduction tectonics along the Pacific-Australian plate boundary. We have analyzed its present-day thermal state using 354 bottom-hole temperatures (BHTs) from 115 wells distributed throughout the basin. The measured temperatures were corrected using an exact solution to Bullard's equation rather than the Horner approximation, thereby allowing for recovery dependence on well diameter and correction for some BHTs at early time after circulation had ceased. Thermal conductivity measurements were completed on 256 samples from eight wells, and matrix conductivities were determined for six end-member lithologies by inversion. Formation conductivities are based on the conductivity and relative proportion of each end-member component. Corrected BHTs, in situ thermal conductivity, and estimates of sediment heat production were combined to compute the present-day, steady state heat flow. The average heat flow is 60 mW m−2, but important geographic variations are present: heat flow on the Western Platform is remarkably consistent at 53–60 mW m−2, attesting to its relative stability since the Late Cretaceous; heat flow in the southern part of the basin is 65–70 mW m−2 due to as much as 3 km of late Miocene erosion; on the southern onshore and to the south of the peninsula, heat flow is 50 ± 3 mW m−2, possibly due to the heat sink effects of crustal thickening; heat flow is highest at 74 mW m−2 on the northern peninsula adjacent to the Taranaki volcanic zone, suggesting a causal relationship between Quaternary volcanism and high heat flow.

Flat type heat pipe

Abstract: A flat type heat pipe for mounting a heating power element, which is capable of forming an optionally shaped heat transferring path with high accuracy, which is of a thin type and to which fins are easily attached. The flat type heat pipe includes at least two aluminum plates substantially in parallel with each other and brazed to each other so as to form a heat transferring path therebetween. The flat type heat pipe also includes an operating liquid which fills the heat transferring path. Because the heat transferring path 25 is formed by means of press molding, punching, laser beam machining, or cutting various shapes of heat transferring paths can be formed finely and with high accuracy. The flexible flat type heat pipe can be made thin, which allows for a variety of uses. Grooves and wicks can be disposed in the heat transferring path, thereby improving the heat conductivity. Because the surface is flat, the fins can be easily attached thereto, thereby a satisfactory radiation effect can be obtained.

Thermoelectric cooling system

Abstract: A thermoelectric cooling system having an electric circuit including a direct current (“d.c.”) power source providing direct current through the electric circuit, a thermoelectric module having at least one heat sink and at least one heat source capable of being cooled to a predetermined temperature range, and a control assembly. The d.c. power source, the control assembly, and the thermoelectric module being connected to each other in series. The control assembly comprising a thermostat control switch mechanism and a resistive element connected to each other in parallel. The thermostat control switch having a sensor generally coupled to the heat source of the thermoelectric module, the thermostat control switch mechanism being open in the predetermined temperature range. The resistive element having a predetermined resistance sufficient for a level of voltage to be provided to the thermoelectric module, when the thermostat control switch mechanism is open, sufficient to substantially prevent reversal of the heat source and the heat sink. The thermoelectric cooling system being used in a process comprising placing an article of interest on the heat source, setting the thermostat to a desired predetermined temperature range, actuating the d.c. power source, and cooling the article of interest through conduction. Alternatively, the article may be placed below the heat source and cooled by convection.

Manifold microchannel heat sinks: isothermal analysis

Abstract: Numerical analyses of manifold microchannel (MMC) heat sinks were performed. The MMC differs from a traditional microchannel heat sink in that the flow length is greatly reduced to a small fraction of the total length of the heat sink. Alternating inlet and outlet channels guide the coolant to and from the microchannels. A silicon heat sink cooled by fluorocarbon liquid was studied. The repetitive nature of the manifold and microchannels results in many planes of symmetry. The thermal and fluid characteristics of a MMC assembly can modeled by a "unit cell" bounded by the centerlines of the manifold inlet and outlet channels and by those of the microchannels and heat sink walls. A general-purpose finite volume CFD code was used. Three-dimensional finite element models of single manifold microchannels were constructed and used to simulate fluid flow and heat transfer. Conjugate analyses suggested that an isothermal model would produce suitably accurate results. In addition to coolant flow rate, channel length, width and depth were varied. Regions of high heat transfer were found near the inlet. At higher inlet velocities, secondary maxims in heat transfer were seen at the base of the microchannel below the inlet, and at the top of the microchannel near the exit. The flow was found to accelerate to a greater extent than predicted by rectangular duct analysis.

Liquid cooled heat sink for cooling electronic components

Abstract: A liquid cooled heat sink (100) for cooling heat generating components (112). The heat sink (100) has a base member (102) with open ended channels (104, 106) formed in at least one surface (118) thereof. The open ends (107) of the channels (104, 106) have a span (SU) less than a span (SL) across a lower portion of the channels (104, 106). A fluid conduit (114, 116) has an outer span (SL) greater than the span (SU) across the open ends (107) of the channels (104, 106) and a flattened surface (110) which is substantially coplanar with the surface (118) of the heat sink base member (102) having the channels (104, 106) therein.

Printed circuit board and heat sink arrangement

Abstract: Making a heat sink and printed circuit board assembly by providing a heat exchange element on the heat sink which lies in heat exchange contact with the heat sink and passes therethrough. After locating the board and heat sink in relative positions apart and with the heat exchange element aligned with an electronic component on the board, a settable thermally conductive compound is injected through a hole in the heat exchange element to bond it to the electrical component. The heat sink is detachable from the heat exchange element to expose the side of the board carrying the components so that maintenance or repair may be performed. Subsequently the heat sink is returned into its position in the assembly.

Thermoelectric cooling module and method for manufacturing the same

Abstract: A thermoelectric cooling module, in which an electronic device is cooled due to the Peltier effect of P-type and N-type thermoelectric semiconductor elements, comprising a heat radiating section which comprises a heat radiating electrode having a fin-shaped portion for heat radiation integrally formed, a heat absorbing section comprising heat absorbing electrode contacted with the electronic device, and a thermoelectric conversion section comprising the P-type and N-type thermoelectric semiconductor elements interposed between the heat radiating electrode and the heat absorbing electrode.

Miniaturized multi-chamber thermocycler

Abstract: A miniaturized multi-chamber thermocycler provides a thermocycler which is easy to handle, and permits the treatment of a great number of samples of small sample volumes at high temperature changing rates and at low heating powers. A sample receptacle body manufactured in micro-system technics provides a plurality of sample chambers which are embodied such that at least one of the sample chamber walls of the sample chamber which constitutes the sample chamber base is an efficient heat conductor and also of low mass. Said sample chambers are coupled to a coupling body, serving as heat sink, established via at least one poor heat conducting bridge which, with respect to its dimensioning and/or material selection is such that its specific heat conductance λ is smaller 5 W/K°·m. The sample chambers are provided with at least one heating element which is constructed to effect, in connection with a sample chamber wall serving as heat balancing layer which simultaneously can be the sample chamber base, a substantially homogeneous temperature distribution in a fluid insertable into the sample chambers.

Method for attaching heat sinks directly to chip carrier modules using flexible-epoxy

Abstract: An aluminum or copper heat sink is attached to a ceramic cap or exposed semiconductor chip using flexible-epoxy to provide improved thermal performance. The aluminum may be coated by anodizing or chromate conversion or the copper may be coated with nickel. Such structures are especilly useful for CQFP, CBGA, CCGA, CPGA, TBGA, PBGA, DCAM, MCM-L, single layer ceramic, and other chip carrier packages as well as for flip chip attachment to flexible or rigid organic circuit boards. These adhesive materials withstand thermal cycle tests of 0° to 100° C. for 1,500 cycles, -25° to 125° C. for 400 cycles, and -40° to 140° C. for 300 cycles; and withstand continuous exposure at 130° C. for 1000 hours without loss of strength. Flexible-epoxies have a modulus of elasticity below 100,000 psi and a glass transition temperature below 25° C., are much stronger than typical silicone adhesives, and do not contaminate the module or circuit board with silicone. The flexible epoxy may contain a material having a low coefficient of thermal expansion (CTE) in order to provide a CTE between that of the silicon die and the metal of the heat sink.

A rational formulation of thermal circuit models for electrothermal simulation. I. Finite element method [power electronic systems]

Abstract: As the size of the semiconductor devices is getting smaller with advanced technology, self-heating effects in power semiconductor devices are becoming important. An electrothermal simulation of complete power electronic systems that include Si chips, thermal packages, and heat sinks is essential for an accurate analysis of the behavior of these systems. This paper presents a rational approach to construct thermal circuit networks equivalent to a discretization of the heat equation by the finite element method. Elemental thermal circuit networks are developed, which correspond to the linear and cubic Hermite elements in the 1-D case, to the triangular and rectangular elements in the 2-D case, and to the tetrahedral and cube elements in the 3-D case. These thermal circuit networks are to be connected to the electrical networks of power electronic systems to provide complete electrothermal models that can be conveniently used in any circuit simulator package. Verification examples are presented to demonstrate the accuracy of the proposed formulation.

Linear motor with improved cooling

Abstract: A linear motor has an epoxy core armature with dual cold plates attached to a top and a bottom of the epoxy core armature to effect cooling of the epoxy core armature. The use of dual cold plates with circulating cooling fluid reduces heat build up by providing paths of high thermal conductivity from any point in the epoxy core armature to the cold plates. Another embodiment of the invention employs ceramic heat sink plates laminated to sides of the epoxy core armature to increase the thermal conductivity and the resultant power dissipation capacity of the epoxy core armature without introducing magnetic or electrically conducting materials. Other embodiments of the invention utilize cold plates formed from extrusions of aluminum or ceramic materials. Still other embodiments have forced air cooling wherein a U-frame of the linear motor has longitudinal flexible seals and air is forced through the U-frame in which the epoxy core armature travel. Yet another embodiment has a U-frame with ducts formed therein through which air is force. Orifices connect the ducts to an interior of the U-frame through which the epoxy core armature travels.

A rational formulation of thermal circuit models for electrothermal simulation-Part I: Finite element method

Abstract: As the size of the semiconductor devices is getting smaller with advanced technology, self-heating effects in power semiconductor devices are becoming important. An electrother- mal simulation of complete power electronic systems that include Si chips, thermal packages, and heat sinks is essential for an accurate analysis of the behavior of these systems. This paper presents a rational approach to construct thermal circuit net- works equivalent to a discretization of the heat equation by the finite element method. Elemental thermal circuit networks are developed, which correspond to the linear and cubic Hermite elements in the 1-D case, to the triangular and rectangular elements in the 2-D case, and to the tetrahedral and cube elements in the 3-D case. These thermal circuit networks are to be connected to the electrical networks of power electronic systems to provide complete electrothermal models that can be conveniently used in any circuit simulator package. Verification examples are presented to demonstrate the accuracy of the proposed formulation.

Microchannel cooling using aviation fuels for airborne electronics

Abstract: Aviation fuel is used as the coolant for a microchannel heat sink for airborne electronics. The use of preexisting aviation fuel as a coolant medium eliminates the weight, size and expense of a separate liquid system dedicated solely to electronics cooling. The heat sink is comprised of a body of material having high thermal conductivity and in which are formed a set of parallel closed-ended microchannels on the order of 0.001 in. by 0.004 in. separated by a distance of 0.001 in.

Thermally enhanced ball grid array package

Abstract: A thermally enhanced ball grid array package for electronic components, with an electronic and a plurality of ceramic component carriers bonded to a metal heat sink, enhances thermal performance, reduces solder ball fatigue and reduces stresses between the ceramic component carriers and the heat sink. Bonding the ceramic component carriers to the heat sink reduces expansion induced stresses of the solder balls on the carriers. Plural ceramic component carriers, smaller than a single carrier would have to be for the same package, reduce stresses at the interfaces between the ceramic component carriers and the heat sink.

Ball grid array package with enhanced thermal and electrical characteristics and electronic device incorporating same

Abstract: A ball grid array (BGA) package incorporating a heat dissipating member which includes a thin die attach portion mounted between an integrated circuit chip (die) and a package substrate, a heat sink portion surrounding the die attach portion, and tie bars connected between the die attach portion and the heat sink portion. The die attach portion is thinner than the heat sink portion such that a recessed area is formed for receiving an integrated circuit die. Heat generated by a die mounted on the die attach portion is transmitted to the heat sink portion along the tie bars, thereby providing enhanced thermal characteristics. Inductive effects on signals passing between the integrated circuit die and a host printed circuit board are reduced by connecting the heat dissipating member to a ground potential. A Faraday cage is formed around the integrated circuit die by mounting a metal plate on the upper peripheral surface of the heat sink portion.

Modular liquid skin heat exchanger

Abstract: A liquid coolant heat exchange system for use in semimonocoque aircraft includes an arcuate planar heat sink fixed along a radius of curvature R 1 by forming members, a flexible arcuate planar spreader plate having a radius R 2 , such that R 1 >R 2 , a heat exchange tube for transferring heat from the liquid coolant to the heat sink and means for attaching the spreader plate to the forming members to hold the spreader plate in contact with the heat sink.

Interleaved-fin thermal connector

Abstract: In order to provide a thermal coupling between a heat source and a heat sink, an interleaved-fin connector is provided. The connector comprises first and second substrates. The first substrate includes a first surface. A plurality of first channels are etched on the first surface to form a plurality of first fins and a first base. The first base can be thermally engaged with the heat source. The second substrate includes a second surface having a plurality of second channels etched therein. The second channels form a plurality of second fins and a second base. The second base can be thermally engaged with the heat sink. The first and second fins providing a thermally conductive path from the heat source to the heat sink when interleaved with each other.

Thermal interface for a heat sink of a plurality of integrated circuits mounted on a substrate

Abstract: A referencing scheme provides a thermal interface between a heat sink and chips within a MultiChip Module (MCM). The referencing scheme comprises a heat sink with a support ring that penetrates a trough formed within a substrate of the MCM. A thermal transfer medium positioned between the heat sink and the chips forms a thermal interface having a low thermal resistance. This cools the chips and ensures reliable operation of the MCM. The trough is filled with a curable adhesive, securing the heat sink to the substrate of the MCM.

Inverse Determination of Boundary Conditions and Sources in Steady Heat Conduction With Heat Generation

Abstract: A Boundary Element Method (BEM) implementation for the solution of inverse or ill-posed two-dimensional Poisson problems of steady heat conduction with heat sources and sinks is proposed. The procedure is noniterative and cost effective, involving only a simple modification to any existing BEM algorithm. Thermal boundary conditions can be prescribed on only part of the boundary of the solid object while the heat sources can be partially or entirely unknown. Overspecified boundary conditions or internal temperature measurements are required in order to compensate for the unknown conditions. The weighted residual statement, inherent in the BEM formulation, replaces the more common iterative least-squares (L2) approach, which is typically used in this type of ill-posed problem. An ill-conditioned matrix results from the BEM formulation, which must be properly inverted to obtain the solution to the ill-posed steady heat conduction problem. A singular value decomposition (SVD) matrix solver was found to be more effective than Tikhonov regularization for inverting the matrix. Accurate results have been obtained for several steady two-dimensional heat conduction problems with arbitrary distributions of heat sources where the analytic solutions were available.

Thermosyphon-powered jet-impingement cooling device

Abstract: A thermosyphon-powered jet-impingement cooling device delivering superior thermal energy dissipation for compact heat sources such as electronic devices. Thermal energy from a heat source travels through the heat source/heat spreader plate interface to the heat spreader plate and heat spreader plate extended surface. Thermal energy is transferred by convection to a single or two-phase coolant media. The heated and/or boiling, less dense coolant begins to expand and rise. The rising coolant or vapor approaches a cold plate and velocity slows due to the greater cross-sectional flow area. The coolant heat energy is released by convection or condensation to the heat dissipation/fluid interface surface, and is then conducted through the cold plate, across the cold plate/heat dissipating device thermal interface, and then to the heat dissipating device. As the cooled media contracts and/or condenses to form droplets, the coolant or droplets begin to fall. As heated or boiling coolant continues to rise, the falling coolant or droplets are both pushed from the high pressure (heated) annulus and pulled from the low pressure (cooled) center through an impingement jet orifice. The coolant impinges against a concave heat/fluid interface surface. The impinging jet of coolant media of the present invention greatly reduces the thermal boundary layer at the point of impingement.

Semiconductor device and semiconductor module

Abstract: It is an object to downsize a device while maintaining a high breakdown voltage. An external terminal (7) protrudes to the outside from the side wall of a sealing resin (2) and a heat sink (1) is exposed in the bottom of the sealing resin (2). A step surface (21) retracted from the exposed surface of the heat sink (1) is formed in the part of the sealing resin (2) surrounding the periphery of the heat sink (1). When using this semiconductor device, the exposed surface of the heat sink (1) is brought into surface contact with the flat surface (41a) of the radiation fin (41) and an insulation sheet (31) is interposed between the step surface (21) and the flat surface (41a), and which is pressed therebetween. The insulation sheet (31) is disposed to cover the region facing the external terminal (7) in the flat surface (41a). Accordingly, it is possible to set the height of the external terminal (7) from the exposed surface of the heat sink (1) lower than the spatial distance determined on the basis of the rated voltage while keeping the breakdown voltage between the external terminal (7) and the radiation fin (41) as the rated voltage.