Showing papers on "Heat sink published in 1995"

Optimum design and selection of heat sinks

Abstract: An analytical simulation model has been developed for predicting and optimizing the thermal performance of bidirectional fin heat sinks in a partially confined configuration. Sample calculations are carried out, and parametric plots are provided, illustrating the effect of various design parameters on the performance of a heat sink. It is observed that the actual convection flow velocity through fins is usually unknown to designers, yet, is one of the parameters that greatly affect the overall thermal performance of a heat sink. In this paper, a simple method of determining the fin flow velocity is presented, and the development of the overall thermal model is described. An overview of different types of heat sinks and associated design parameters is provided. Optimization of heat-sink designs and typical parametric behaviors are discussed based on the sample simulation results.

Large blood vessel cooling in heated tissues: a numerical study.

Abstract: Large blood vessels can produce steep temperature gradients in heated tissues leading to inadequate tissue temperatures during hyperthermia This paper utilizes a finite difference scheme to solve the basic equations of heat transfer and fluid flow to model blood vessel cooling Unlike previous formulations, heat transfer coefficients were not used to calculate heat transfer to large blood vessels Instead, the conservation form of the finite difference equations implicitly modelled this process Temperature profiles of heated tissues near thermally significant vessels were calculated Microvascular heat transfer was modelled either as an effective conductivity or a heat sink An increase in perfusion in both microvascular models results in a reduction of the cooling effects of large vessels For equivalent perfusion values, the effective conductivity model predicted more effective heating of the blood and adjacent tissue Furthermore, it was found that optimal vessel heating strategies depend on the microvascular heat transfer model adopted; localized deposition of heat near vessels could produce higher temperature profiles when microvascular heat transfer was modelled according to the bioheat transfer equation (BHTE) but not the effective thermal conductivity equation (ETCE) Reduction of the blood flow through thermally significant vessels was found to be the most effective way of reducing localized cooling

High performance forced air cooling scheme employing microchannel heat exchangers

Abstract: In this paper, a high performance forced air cooing scheme is theoretically and experimentally investigated which employs microchannel parallel plate-fin heat sinks and tubes to deliver the air to and optionally from the heat sink. The performance of the cooling system is modeled in terms of thermal resistance, pressure drop, and pumping power. Optimizations are performed and design trade-offs discussed. Tubes are observed to have a significant impact on optimum heat sink design as well as operating point. Sample heat sinks with lateral dimensions of 5/spl times/5 cm/sup 2/ and fin lengths of 1.5 and 2.5 cm were fabricated from copper and aluminum foils using a simple assembly process. Fin thicknesses and channel widths of the heat sinks are on the order of 200 and 500 /spl mu/m, respectively. Thermal resistances as low as 0.2 R/W are measured. Results of the present study are compared to prior works dealing with direct air cooling. The thermal performances achievable using the investigated cooling approach are superior to those attainable using open air cooled heat sinks as well as those employing silicon microcoolers.

Design and analysis of heat sinks

Abstract: Linear Transformations. Elements of the Linear Transformations. Singular Fins and Spines and Single Elements. Algorithms for Finned Array Assembly. Examples of Finned Array Analysis. Reciprocity and Node Analysis. A General Array Method. Convective Optimizations. Heat Transfer-Parallel Plate Heat Sinks. References. Appendices. Indexes.

Pad array semiconductor device having a heat sink with die receiving cavity

Abstract: A semiconductor device (10) provides heat dissipation while maintaining a low profile. The device includes a circuitized substrate (12) having an opening (20). Inserted into, or at least covering, the opening is a heat sink (22) having a base portion (24), sidewalls (26), and flanges (28). Flanges of the heat sink are attached or supported by a surface of the substrate. Together the base portion and sidewalls of the heat sink form a cavity for receiving a semiconductor die (13). The die is electrically coupled to conductive traces (14) formed on the substrate by wire bonds (19), and the traces are electrically coupled to solder balls (21) by conductive vias (18). In one embodiment, base portion (24) of heat sink (22) extends below substrate (12) to permit contact to a user substrate (34). While in another embodiment, a base portion (118) of a heat sink (116) is exposed on a top surface of a substrate (112) for coupling to another heat sink (124).

Shielded heat sensor for measuring temperature

Abstract: A sensor for measuring the temperature of a workpiece including a substrate, wafer, shield or other element in a semiconductor processing system. In the illustrated embodiment, the sensor has a heat shield to reflect away from the heat sensing element, heat from unwanted sources such as susceptors and heating cartridges which can adversely affect the accuracy of the measurement. In addition, the heat shield preferably has a small thermal mass for improved responsivity.

Chip carrier modules with heat sinks attached by 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.

Apparatus for cooling charge coupled device imaging systems

Abstract: Apparatus for cooling charge-coupled device (CCD) imaging systems. The apparatus comprises a thermoelectric cooler thermally coupled to the imaging system for transferring heat away from and cooling the imaging system portion of the imaging system. The thermoelectric cooler has a cold side and an opposing hot side, with the cold side thermally coupled to the imaging sensor to enable the transfer of heat from the sensor in response to a supply of power. A power supply is coupled to the cooler for supplying required power. The hot side of the cooler is thermally coupled to a heat pipe, which is composed of a heat-conducting material having a hollow portion containing a wicking material and a working fluid. A heat sink is thermally coupled to the heat pipe enabling heat dissipation. The working fluid cyclically evaporates into vapor and condenses into liquid to effect the heat transfer from the heat pipe to the heat sink.

Semiconductor device having a thermal dissipator and electromagnetic shielding

Abstract: An inexpensive packaged integrated circuit with improved heat dissipative capacity and electrical performance. In one embodiment, the packaged integrated circuit includes a semiconductor die, a plurality of electrically conductive package leads, a thermal induction plate and a plurality of electrically conductive bond wires. A surface of the thermal induction plate may remain exposed outside the package. The thermal induction plate reduces package lead inductance and provides shielding of electromagnetic radiation that can cause electromagnetic interference. Preferably, holes are formed through the thermal induction plate to enhance flow of the package material during formation of a package and provide interlocking of the package to the remainder of the integrated circuit. In another embodiment, the packaged integrated circuit further includes a heat sink having a surface exposed to the exterior of the package. The heat sink may also perform an electrical function such as, for instance, acting as a power or ground plane. One or more generally conductive layers can be added to either of the above embodiments. The generally conductive layer or layers may be used to provide ground planes, power planes and/or electrically conductive traces for signal routing or an interconnect ring. The generally conductive layer or layers enable uniform power and ground supplies to be provided to the circuitry formed on the die, reduce package lead inductance, provide decoupling capacitances that reduce switching noise and crosstalk, and allow increased flexibility in the placement of particular circuit components.

Investigation of Non-Darcian Forced Convection in an Asymmetrically Heated Sintered Porous Channel

Abstract: A study of non-Darcian forced convection in an asymmetric heating sintered porous channel is carried out to investigate the feasibility of using this channel as a heat sink for high-performance forced air cooling in microelectronics. A volume-averaging technique is applied to obtain the macroscopic equations with the non-Darcian effects of no-slip boundary, flow inertia, and thermal dispersion. Local non-thermal-equilibrium is assumed between the solid and the fluid phases. The analysis reveals that the particle Reynolds number significantly affects the solid-to-fluid heat transfer coefficients. A wall function is introduced to model the transverse thermal dispersion process for the wall effect on the lateral mixing of fluid. The local heat transfer coefficient at the inlet is modeled by a modified impinging jet result, and the noninsulated thermal condition is considered at exit. The numerical results are found to be in good agreement with the experimental results in the ranges of 32 ≤ Red ≤ 428 and q = 0.8 ~ 3.2 W/cm2 for Pr = 0.71.

Electronic devices with electromagnetic radiation interference shields and heat sinks

Abstract: An electronic device with an EMI shield surrounding an electronic component on a substrate. A heat sink extends through an opening in the shield from heat conductive contact with the component to a position outside the shield. The heat sink operates also in an EMI shield capacity. The shield is stressed to hold the heat sink positively in heat conducting contact with the components. The shield preferably has cutting teeth which cut into the heat sink as the latter is passed into the aperture. With the inserted part of the heat sink being cylindrical, rotation of the heat sink causes the teeth to move up the inserted part to stress the shield and urge the heat sink against the component.

On the application of the Kirchhoff transformation to the steady-state thermal analysis of semiconductor devices with temperature-dependent and piecewise inhomogeneous thermal conductivity

Abstract: The paper presents a discussion on the application of the Kirchhoff transformation to the thermal analysis of semiconductor devices with temperature-dependent and piecewise inhomogeneous thermal conductivity. The Kirchhoff transformation is shown to generally reduce the problem to the solution of the linear heat equation with nonlinear jump conditions on the apparent temperature across subdomains, unless the ratio of the thermal conductivities is temperature independent, in which case the apparent temperature is continuous. In many practical cases, the temperature dependence of the thermal conductivity can be approximated in all subdomains so as to enforce this condition; one and two-dimensional examples are discussed to show that in realistic configurations (devices with metal heat sinks, multilayered structures made of different semiconductors) the error thereby introduced is acceptably low.

Capillary pumped loop body heat exchanger

Abstract: A capillary pumped loop for transferring heat from one body part to another body part, the capillary pumped loop comprising a capillary evaporator for vaporizing a liquid refrigerant by absorbing heat from a warm body part, a condenser for turning a vaporized refrigerant into a liquid by transferring heat from the vaporized liquid to a cool body part, a first tube section connecting an output port of the capillary evaporator to an input of the condenser, and a second tube section connecting an output of the condenser to an input port of the capillary evaporator. A wick may be provided within the condenser. A pump may be provided between the second tube section and the input port of the capillary evaporator. Additionally, an esternal heat source or heat sink may be utilized.

Rotable and slideble heat pipe apparatus for reducing heat build up in electronic devices

Abstract: A rotatable and slidable heat pipe apparatus for transferring heat away from a microprocessor chip more rapidly than by heat sink surface area dissipation to the surrounding air alone, comprising a heat sink with an integral cylindrical passageway adapted to receive a first end of a heat pipe shaped like a crankshaft, and a heat spreader formed from a metal plate with a first end rolled up to define a cylindrical opening adapted to receive a second end of the heat pipe. The heat spreader is attached to an underside of a keyboard. Since the heat pipe is able to rotate within the cylindrical passageway and the cylindrical opening, the keyboard can be raised to an open position and lowered to a closed position quickly and simply without the risk of breaking or bending the heat pipe, and manufacturing position tolerances between the heat pipe apparatus components are increased resulting in a simplified manufacturing process. The heat pipe can also be slid in to and out of the cylindrical passageway or the cylindrical opening, thereby enabling computer manufacturers to incorporate the heat pipe into portable battery powered notebook-type computer systems designed to allow a user to remove, replace, or swap internal components by simply flipping open or removing the keyboard, and further enabling a user to perform maintenance work or repairs on the computer system without concern for damage to the heat pipe.

Cooling apparatus for electronic chips

Abstract: A circuit board mounted integrated circuit chip such as a processor is cooled by apparatus including a heat sink, a shroud and a fan. The heat sink includes a base placed on the top surface of the chip and fins extending up from the base. The shroud includes top and two opposed side walls closely enclosing the heat sink. The shroud is attached directly to the circuit board rather than to the heat sink or chip and can be used with chips and heat sinks that do not have special provision for attachment of the shroud. The fan moves cooling air through the shroud and between and around the heat sink fins. The fan is mounted to an end of the shroud and does not require clearance above the heat sink and shroud.

Temperature control system with thermal capacitor

Abstract: An improved thermoelectric temperature control system for selectively heating or cooling a temperature control fluid to be provided through an exit conduit to an external thermal load and returned to the system through an inlet conduit. The system having at least a first liquid heat exchanger, a thermoelectric module in thermal conductivity with the liquid heat exchanger, a heat sink in thermal conductivity with the thermoelectric module, a pump and connecting conduits to move the temperature control fluid from the inlet conduit through the pump and liquid heat exchanger to the exit conduit and power and control electronics to activate the pump and thermoelectric module. The improvement comprises a thermal capacitor connected for fluid communication with the external thermal load and the thermoelectric temperature control system to provide thermal wattage to the external thermal load via the temperature control fluid in addition to the thermal wattage provided to the external thermal load by the thermoelectric temperature control system during the real-time use of the thermoelectric temperature control system. An alternate embodiment includes a liquid-to-liquid heat exchanger system to improve the efficiency of the system.

Apparatus and method for converting thermal energy to mechanical energy

Abstract: A thermal energy storage and conversion system that captures thermal energy from solar collectors, stores thermal energy in a first heated medium, converts a portion of stored thermal energy to mechanical energy by utilization of a heat engine, converts a second portion of stored thermal energy to a thermal energy sink by utilization of a refrigeration device, and stores a portion of thermal energy sink for use later. While the sun is shining, energy is collected and stored in first heated medium. Both during day and night, a portion of stored energy in first heated storage medium is transferred to first refrigerant that vaporizes and provides mechanical energy to heat engine. A second portion of stored thermal energy in first heated medium is transferred, as needed, to second refrigerant which vaporizes and removes from second fluid medium a quantity of heat including second fluid medium's heat of fusion, thereby freezing the second medium. Solidified second medium then provides, during both day and night, a low temperature heat sink to help drive heat engine, a low temperature source of refrigeration for cooling an enclosed space, and an efficient, compact, and user friendly energy storage device.

Ducted opposing bonded fin heat sink blower multi-microprocessor cooling system

Abstract: A device and method for cooling an integrated circuit package - in particular, a microprocessor - within an enclosed computer system. The device comprises a blower (110), a first heat sink (130) attached to the microprocessor, and a first air duct (120) coupling the blower (110) to the first heat sink (130). The blower (110) has an air intake (135) from the exterior of the computer system. The blower (110) generates an air stream which flows through the first air duct (120) to the first heat sink (130) for cooling the first microprocessor (160). A second air duct (140) connected to the first heat sink (130) may be used to subsequently direct the air stream to a second heat sink (150) for cooling a second microprocessor (170). An efficient duct heat sink for use in this cooling system (100) can be easily constructed by attaching two extruded heat sinks.

Geothermal heat pump system

Abstract: A geothermal heating and/or cooling system includes one or more of a plurality of features that enhance the efficiency of the system Preferably, the system includes a subterranean heat exchanger having tubes disposed against a conductive sheet The system also preferably includes a reservoir vessel for holding a supply of heat transfer fluid in a liquid phase Also, the system preferably includes heat exchange means for exchanging heat between the heat transfer fluid and the outdoor air In addition, the system preferably has an automatically adjusting cooling expansion valve controlled by a sensor disposed to detect the pressure or temperature of heat transfer fluid exiting an indoor air handler in a cooling mode, the system also preferably has an automatically adjusting heating expansion valve controlled by a sensor that is preferably located so as to detect the temperature or pressure of heat transfer fluid flowing from the subterranean heat exchanger to a gas compressor The enhancements may be used individually or in various combinations

Heat sink and retainer for electronic integrated circuits

Abstract: A heat sink and retainer clip for use in conjunction with an electronic integrated circuit, such as a semiconductor device, to provide cooling of the device, the device being mounted on a rectangular socket with opposing sidewalls and at least two of the sidewalls having lugs projecting laterally outward. The heat sink has a flat plate and a plurality of fins projecting upward from the top surface, except over the central portion of the plate. The retainer clip is constructed of two pieces. One piece is an elongated strap having a bent portion that bears down on the heat sink to force it into a heat conducting relationship with the device and also includes an opening that is hooked on the one of the lugs. The strap lies in the central portion of the sink. The second piece is rotatably mounted on the end of the first piece and when forced down and rotated inward, an opening will hook on the other lug.

Ho:YAG laser pumped by 1.9-/spl mu/m diode lasers

Abstract: A 21-/spl mu/m Ho:YAG laser end pumped by 1.9-/spl mu/m diode lasers has generated nearly 0.7-W CW output power. Laser operation was maintained even with Ho:YAG heat sink temperatures in excess of 60/spl deg/C. >

Structure for attaching a lead frame to a heat spreader/heat slug structure

Abstract: A method and structure for attaching a lead frame to a heat sink are provided. In one embodiment, a layer of thermally conductive, electrically insulating epoxy is formed on a heat sink and the epoxy layer is fully cured. A thermoplastic adhesive layer is formed on the epoxy layer, and the heat sink is clamped to the lead frame such that the thermoplastic layer contacts the lead frame. The thermoplastic layer is heated to its melting point and then cooled, thereby joining the heat sink and the lead frame. In a variation, a partially cured B-stage epoxy layer is used to replace the thermoplastic layer. The B-stage epoxy layer is fully cured to connect the lead frame to the heat sink.

Thermally enhanced chip carrier package

Abstract: A thermally enhanced chip carrier package with a built-in heat sink for semi-conductor integrated circuit chips. A circuit substrate is formed of a suitable thermoplastic such as PPS or LCP with a center opening and a metal attachment ring for attaching a heat sink to either the top or bottom thereof with solder. A casing is further formed on the substrate outwardly of the aperture and the heat sink mounted thereacross, the casing being comprised of the suitable thermoplastic and being chemically fused to a portion of the circuit substrate to create a moisture seal therebetween. An encapsulant for filling the cavity within the casing and a lid may also be utilized to further secure and seal the chip mounted to the heat sink secured therein.

High performance spiral heat sink

Abstract: A thermally conductive heat sink unit In the present invention, a thermally conductive heat sink has a first surface A plurality of arc-shaped cooling fins are formed in the first surface The arc-shaped cooling fins extend radially outward from a central region of the first surface A second surface of the thermally conductive heat sink is adapted to thermally contact a heat generating device By contacting the heat generating device, heat generated by the device is dissipated through the arc-shaped cooling fins of the first surface In one embodiment of the present invention, a recessed region is formed into the first surface of the thermally conductive heat sink The recessed region is formed above the central region and the region peripherally surrounding the central region such that the recessed region extends into a portion of the arc-shaped cooling fins In such an embodiment, a fan is embedded within the recessed region of the thermally conductive heat sink The fan impinges the arc-shaped cooling fins and the central region with a stream of coolant to aid in the dissipation of heat from the thermally conductive heat sink In one embodiment, the arc-shaped cooling fins are arranged to insure optimal heat transfer via the stream of coolant impinging and flowing by the arc-shaped cooling fins

Device to monitor and control the temperature of electronic chips to enhance reliability

Abstract: Device to monitor and control the temperature of electronic chips to enhance reliability including a thermal electric cooling device in which the cold side is thermally secured to the chip and the hot side is attached to a heat sink. A thermocouple is sandwiched between the TEC device and the chip and a feedback control circuit is connected between the thermocouple and the voltage source which applies a potential to the TEC device to maintain the chip at the desired substantially constant temperature.

Transparent substrate vertical cavity surface emitting lasers fabricated by semiconductor wafer bonding

Abstract: A method for fabricating transparent substrate vertical cavity surface emitting lasers ("VCSEL"s) using wafer bonding is described. The VCSELs have their active layers located much more closely to a heat sink than is possible in known absorbing substrate VCSELs. The improved heat transport from the active layer to the heat sink permits higher current operation with increased light output as a result of the lower thermal impedance of the system. Alternatively, the same light output can be obtained from the wafer bonded VCSEL at lower drive currents. Additional embodiments use wafer bonding to improve current crowding, current and/or optical confinement in a VCSEL and to integrate additional optoelectronic devices with the VCSEL.

Apparatus for encapsulating electronic packages

Abstract: A printed wiring board with either a pin grid array, a ball grid array, a land grid array, etc. of electrical contacts is prepared with a heat sink attached in the usual manner. A passage is provided either in the printed wiring board or in the heat sink so that during the transfer molding process, fluid molding compound passes latitudinally under the heat sink into a cavity below the heat sink. The mold is provided with a biased plug that exerts pressure on the heat sink or printed wiring board to prevent molding compound from covering the heat sink. The biased plug also accommodates variations in the thickness of the printed wiring board.

Method for directly joining a chip to a heat sink

Abstract: The present invention relates generally to a new apparatus and method for directly joining a chip to a heat sink. More particularly, the invention encompasses an apparatus and a method that uses a double-sided, pressure-sensitive, thermally-conductive adhesive tape to directly join a chip or similar such device to a heat sink.