WO1996006321A1 - Dissipateur de chaleur - Google Patents

Dissipateur de chaleur Download PDF

Info

Publication number
WO1996006321A1
WO1996006321A1 PCT/US1995/010511 US9510511W WO9606321A1 WO 1996006321 A1 WO1996006321 A1 WO 1996006321A1 US 9510511 W US9510511 W US 9510511W WO 9606321 A1 WO9606321 A1 WO 9606321A1
Authority
WO
WIPO (PCT)
Prior art keywords
heat sink
binder
heat
thermoplastic
thermally conductive
Prior art date
Application number
PCT/US1995/010511
Other languages
English (en)
Inventor
Barbara Kiiskila Lograsso
Original Assignee
Iowa State University Research Foundation, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Iowa State University Research Foundation, Inc. filed Critical Iowa State University Research Foundation, Inc.
Priority to AU33306/95A priority Critical patent/AU3330695A/en
Publication of WO1996006321A1 publication Critical patent/WO1996006321A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
    • H01L23/373—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon
    • H01L23/3733—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon having a heterogeneous or anisotropic structure, e.g. powder or fibres in a matrix, wire mesh, porous structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Definitions

  • This invention relates generally to a heat sink and method of fabrication, and more particularly to an injection-molded thermally conductive heat sink and method of fabrication.
  • heat sinks fabricated from extruded aluminum, but aluminum heat sinks have certain physical design limits.
  • One limitation is the shape, which is limited to simple two-dimensional profile shapes that can be extruded. This reduces the potential for developing heat sinks having a reduced size or complex shapes which increase the convective and radiant cooling efficiency of the heat sink.
  • Another limitation is the rigidity of the heat sink which prevents the heat sink from conforming to the shape of the electrical components, printed circuit board and the like. Gaps or spaces may be introduced between the contacting surfaces of the components or printed circuit board and the attached heat sinks because of normal manufacturing tolerances, substantially inhibiting heat transfer between the surfaces. If the heat sink is attached to two or more components, the thermal efficiency of the heat sink may be greatly reduced as the gaps and spaces between contacting surfaces become more abundant. Flexible thermal pads or epoxies have been applied between the contacting surfaces to eliminate air spaces and improve heat transfer between the electronic component and the heat sink. However, the use of such pads or epoxies often introduces potentially damaging thermal stresses between the components and the heat sink as the heat sink, thermal pad or epoxy and electronic component have different coefficients of thermal expansion.
  • a new type of heat sink is constructed of filled polymer material that can be injection-molded into a variety of compact, complex shapes which are highly efficient for convective cooling with high velocity forced air.
  • the filled polymer material has only about two percent of the thermal conductivity of pure aluminum, these complex-shaped devices have a cooling capacity that is comparable to bulky aluminum heat sinks that cannot fit in a compact, forced convection environment. Because of the materials and processes used to fabricate the heat sinks, the filled polymer heat sinks are also substantially rigid.
  • a heat sink for transfer- ring heat away from an object.
  • the heat sink is molded in selected shape and comprises a flexible binder, such as a thermoplastic elastomer, and a plurality of thermally conductive particles mixed with the binder for transferring heat through the binder.
  • the proportion of thermally conductive particles in the mixture is between twenty and eighty percent by volume.
  • Figure 2 is a schematic view of a heat sink with four configured posts.
  • Figure 3 is an end view of another heat sink.
  • Figure 4 is a schematic flow chart showing the fabrication of a heat sink in accordance with the invention.
  • Figure 5 is a schematic end view showing the heat sink mounted to a plurality of electronic components on a printed circuit board.
  • Figure 6 is a schematic top plan view of another heat sink.
  • Figure 7 is a schematic end view of the heat sink of Figure 6 showing the two heat sources and a plurality of thermocouples applied to the heat sink.
  • the heat sink 11 includes posts 14 which have a corrugated or shaped configuration to increase the surface area for heat transfer by radiation and conduction to the surrounding area.
  • the thickness of the base 12 and the height of the posts 13 need not be uniform throughout the heat sink 11. Instead, the shape of the heat sink may be tailored to the specifications of a particular application.
  • the heat sink 11 is manufactured in accordance with the present invention by molding a mixture of a highly conductive powder and a flexible binder.
  • the highly conductive powder is preferably a metal having a low thermal resistance.
  • the metal powder may be produced using inert gas, air or water atomization processes using annular-slit nozzles, close-coupled nozzles or conventional free-fall nozzles; or the metal powder may be made by other processes such as electrolytic, grinding, chemical fiber processing, etc., that yield powders having the appropriate size for use in the fabrication of heat sinks. Copper, boron nitride, silver, aluminum, molybdenum, aluminum nitride, silicon carbide, silica, carbon, diamond powders and alloys of these materials are suitable for use.
  • the particles are selected with a size distribution in the range of 0.1 to 5000 microns with the preferred range being 25 to 50 microns.
  • the thermal conductivity of the heat sink will depend primarily on the thermal conductivity of the powder.
  • the preferred material chosen for this application is copper. Copper has extremely high thermal and electrical conductivity and is available economically in high purity ingots or bar stock.
  • the copper powder is formed of a melt of electronic grade copper (99.99% pure) atomized by a high pressure inert gas atomization process (HPGA) of the type described by Ayers and Anderson in U.S. Patent 4,619,845, the teaching of which is incorporated herein by reference.
  • HPGA high pressure inert gas atomization process
  • the electrical conductivity of HPGA copper powder pressed to full density was essentially equal to that of electronic grade copper, having a thermal conductivity of 226 BTU/ft/hr/degree F at 68 °F.
  • the thermal conductivity of heat sinks comprising a polymer filled with aluminum is 3.1 BTU/ft/hr/degree F at 68°F
  • the thermal conductivity of commercial purity aluminum alloy used for heat sinks is approximately 128 BTU/ft/hr/degree F at 68°F.
  • the commercial purity copper powder has a slightly reduced electrical conductivity relative to the HPGA copper, the conductivity of the commercial copper powder is far superior to aluminum powder.
  • the binder material is preferably a thermoplastic elastomer.
  • the flexibility of the heat sink 11 depends upon the stiffness of the binder material.
  • the binder material has a hardness in the range of Shore A10 to Shore D90 to provide the heat sink with sufficient flexibility.
  • Suitable thermoplastic elastomers include thermoplastic olefins, olefinic thermoplastic vulcanizate, styrene block copolymer, thermoplastic urethane copolyester, copolyamide and santoprene. Since these thermo- plastic elastomers are available in a several stiffness values, the flexibility of the heat sink may be tailored to meet the requirements of a particular application.
  • the binders may include a coupling agent such as glycerol, titanate, stearic acid, polyethylene glycol, humic acid, ethoxylated fatty acids and other known coupling agents to achieve higher loading of the powder particles in the binder.
  • a coupling agent such as glycerol, titanate, stearic acid, polyethylene glycol, humic acid, ethoxylated fatty acids and other known coupling agents to achieve higher loading of the powder particles in the binder.
  • the powder particles 16 are either screen-classified or air-classified so that they fall within the desired range of particle size.
  • the powder particles 16 and pellets of a thermoplastic elastomer binder 17 including a solvent 18 and a lubricant 19, if desired, are heated and mixed into a compound which is then heated and molded to the desired shape.
  • Coloring agents 20 may also be added to the mixture to increase the emissivity of the heat sink 11 or to color the heat sink to provide for example a visual indication of the thermal conductivity or the identify of the manufac ⁇ turer of the heat sink.
  • the binder and alloy powder are mixed in proportions selected to provide the desired thermal conductivity and flexibility for the heat sink.
  • the thermal conductivity is dependent upon the amount of powder in the mixture or volume loading of powder in the binder, with a high volume loading of powder offering increased thermal conductivity.
  • Blends of 20 to 80 volume percent copper have been found to be highly satisfactory. High volume loading of powder, for example 70-80%, may be achieved by using the fine spherical particles produced by HPGA process. Blends of different particle sizes can also be used to achieve optimum volume loading, whereby the smaller particles can fit in the interstices between the larger particles to provide a higher volume filling.
  • the powder particles 16 and binder 17 are preferably mixed as shown in Fig. 4, although it should be understood that other processes may be used to mix the binder and powder particles into a compound. As shown in Fig. 4, the powder particles 16, binder pellets 17 and any additives are mixed in the mixer 21 and then fed into a twin- screw extruder 22 which further mixes and extrudes the mixture.
  • the extruder prefer ⁇ ably heats the powder particles 16 and elastomer pellets 17 and uses moderate to high shear mixing to provide a homogeneous feedstock.
  • the extruder may include a plurality of heating zones in the range of 150° to 200°C, with the highest temperature located at the extrusion end.
  • the extruder may have four zones set at 150°C, 170°C, 190°C and 200°C. After the material is extruded, it is cooled and supplied to the granulator 23 where it is ground into compound pellets 24. To ensure complete mixing, the process of mixing-extrusion-granulation may be repeated several times.
  • the ground compound pellets 24 are then heated and molded to the desired shape.
  • the coloring agents may be added to the compound pellets 24 when heated.
  • the heat sink 11 may be formed by injection molding, extrusion, rotation molding, pressure molding, compression molding, etc. In the process shown in Fig. 4, for example, the compound pellets 24 are supplied to a reciprocating screw injection molder 26.
  • the injector 26 may also have a plurality of heating zones, where the temperature at the injection end 27 of the injector is 200°C. The heated mixture is injected into a molding cavity 28. The cavity is then opened, and the shaped heat sink 11 is allowed to cool.
  • the conductivity of the heat sink is dependent upon the particle volume loading, particle conductivity and polymer conductivity.
  • the thermal conductivity increases as the volume fraction of powder particles increases.
  • Spherical powder particles are more easily molded than irregular particles at the higher volume fractions of loading; however, this does not preclude the use of irregular particles such as carbon fibers in molding applications.
  • Non-spherical particles with a rough surface have a lower packing density and coordination number than spherical particles due to both physical constraints and particle interaction.
  • the increased surface roughness results in interlocking of particles and greater difficulty for particles trying to slide past one another. For example, molding of the irregular copper powder with binder was difficult because of the loss of fluidity, whereas the mixture of binder with the fine spherical copper powder was still very fluid at 60 volume percent.
  • the flexible heat sink 11 may be used to cool several different components 35 on a printed circuit board 36.
  • the flexible heat sink 11 conforms to the shape of the components 35, accommodating variations in manufacturing tolerances and eliminating the need for thermal pads, epoxies and the like between the heat sink and the components.
  • the heat sink 11 may be mounted directly to the components 35 by adhesive or other known mounting means. Because the heat sink 11 is flexible, the heat sink may be compressed against the components 35 to ensure that the entire surface of the component 35 contacts the heat sink 11. Instead of being mounted to the compo- nents 35, the heat sink may also be secured to the printed circuit board 36 in contact with the components 35 as is known in the art.
  • a portion of the heat sink may also conform to and be positioned in contact with the external housing of the electronic package for transferring heat away from the components 35 by conduction as well as convection.
  • the flexibility of the heat sink also reduces the effects of vibrations and force of impact on the components 35 and the printed circuit board 36.
  • the thermal conductivity of the heat sink 11 is equal to or greater than the combination of a thermal pad and metal heat sink. Thermal stresses induced by the thermal expansion of the components are also substan- tially reduced as the heat sink may be compressed by the expanding component. Thus, the performance of the heat sink 11 is not affected by the heat sink and electronic components 35 having different coefficients of thermal expansion.
  • Example 1 particles of HPGA copper powder having a size in the range of 45 to 106 micrometers were blended with a binder of Advanced Elastomer Systems santoprene 80.
  • the mixture included 896 grams of HPGA copper powder and 97 grams of the santoprene binder, providing a volume percent loading of 52% volume copper to 48% volume binder.
  • the copper and binder particles were mixed in twin screw extruder having four zones set at 180°C, 180°C, 190°C and 200°C, respectively.
  • the extruded compound was ground into pellets approximately 1/4 inch long.
  • the copper/ binder pellets were fed into an injection molder having four zones set at 180°C, 200°C, 210°C and 210°C and molded into a heat sink 11 having the shape shown in Figure 6.
  • Example 2 In a second example, a powder particle/binder mixture consisting of PK120 Carbon Fiber particles (AMOCO) and the Advanced Elastomer Systems santoprene 80 was prepared. The mixture included 200.0 grams of carbon particles and 108.8 grams of the santoprene binder to obtain a mixture having 45% volume carbon and 55% volume santoprene. The particles and the binder were mixed and compounded in a twin screw extruder having four zones set at 180°C, 180°C, 190°C and 200°C, respec ⁇ tively, and the compound was ground into 1/4 inch pellets.
  • AMOCO PK120 Carbon Fiber particles
  • santoprene 80 was prepared. The mixture included 200.0 grams of carbon particles and 108.8 grams of the santoprene binder to obtain a mixture having 45% volume carbon and 55% volume santoprene.
  • the particles and the binder were mixed and compounded in a twin screw extruder having four zones set at 180°C
  • thermocouples TC1-TC8 were used to measure the temperature of the heat sink 11 at several different positions. The measured temperatures for the copper/santoprene heat sink and the carbon/santoprene heat sink are provided in the following table:
  • a flexible heat sink which can be molded into desired shapes from a highly thermal conductive material comprising metal particles dispersed in a thermoplastic elastomer binder.
  • the flexible heat sink maximizes surface contact between the heat sink and electronic components and minimizes the adverse effects of any differences in the thermal coefficients of expansion of the heat sink and the component.
  • the efficiency of a thermal management system incorporating the flexible heat sink of the present invention is thereby increased.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Thermal Sciences (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)

Abstract

L'invention concerne un dissipateur de chaleur (11) pour dissiper la chaleur d'un objet (35). Le dissipateur de chaleur (11) est constitué d'un liant flexible et d'une pluralité de particules conductrices de chaleur dispersées dans le liant, pour transférer la chaleur d'un objet (35), à travers le liant.
PCT/US1995/010511 1994-08-22 1995-08-18 Dissipateur de chaleur WO1996006321A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU33306/95A AU3330695A (en) 1994-08-22 1995-08-18 Heat sink

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US29398294A 1994-08-22 1994-08-22
US08/293,982 1994-08-22

Publications (1)

Publication Number Publication Date
WO1996006321A1 true WO1996006321A1 (fr) 1996-02-29

Family

ID=23131387

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1995/010511 WO1996006321A1 (fr) 1994-08-22 1995-08-18 Dissipateur de chaleur

Country Status (2)

Country Link
AU (1) AU3330695A (fr)
WO (1) WO1996006321A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6919504B2 (en) 2002-12-19 2005-07-19 3M Innovative Properties Company Flexible heat sink
US7108055B2 (en) * 2002-03-29 2006-09-19 Advanced Energy Technology Inc. Optimized heat sink using high thermal conducting base and low thermal conducting fins
USD903610S1 (en) 2019-08-28 2020-12-01 Carbice Corporation Flexible heat sink
USD904322S1 (en) 2019-08-28 2020-12-08 Carbice Corporation Flexible heat sink
US10859330B1 (en) 2019-08-28 2020-12-08 Carbice Corporation Flexible and conformable polymer-based heat sinks and methods of making and using thereof
USD906269S1 (en) 2019-08-28 2020-12-29 Carbice Corporation Flexible heat sink
WO2024217904A1 (fr) * 2023-04-18 2024-10-24 Kerafol Holding Gmbh Matériau de moulage par injection thermoconducteur

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3564109A (en) * 1967-08-24 1971-02-16 Siemens Ag Semiconductor device with housing
US3694182A (en) * 1971-04-20 1972-09-26 Ford Motor Co Glass tempering die construction
DE2511010A1 (de) * 1975-03-13 1976-09-23 Bosch Gmbh Robert Elektrisches bauelement mit kuehlkoerper
US4654754A (en) * 1982-11-02 1987-03-31 Fairchild Weston Systems, Inc. Thermal link
US4838347A (en) * 1987-07-02 1989-06-13 American Telephone And Telegraph Company At&T Bell Laboratories Thermal conductor assembly
US4869954A (en) * 1987-09-10 1989-09-26 Chomerics, Inc. Thermally conductive materials
US5285108A (en) * 1991-06-21 1994-02-08 Compaq Computer Corporation Cooling system for integrated circuits

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3564109A (en) * 1967-08-24 1971-02-16 Siemens Ag Semiconductor device with housing
US3694182A (en) * 1971-04-20 1972-09-26 Ford Motor Co Glass tempering die construction
DE2511010A1 (de) * 1975-03-13 1976-09-23 Bosch Gmbh Robert Elektrisches bauelement mit kuehlkoerper
US4654754A (en) * 1982-11-02 1987-03-31 Fairchild Weston Systems, Inc. Thermal link
US4838347A (en) * 1987-07-02 1989-06-13 American Telephone And Telegraph Company At&T Bell Laboratories Thermal conductor assembly
US4869954A (en) * 1987-09-10 1989-09-26 Chomerics, Inc. Thermally conductive materials
US5285108A (en) * 1991-06-21 1994-02-08 Compaq Computer Corporation Cooling system for integrated circuits

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7108055B2 (en) * 2002-03-29 2006-09-19 Advanced Energy Technology Inc. Optimized heat sink using high thermal conducting base and low thermal conducting fins
US6919504B2 (en) 2002-12-19 2005-07-19 3M Innovative Properties Company Flexible heat sink
CN100360627C (zh) * 2002-12-19 2008-01-09 3M创新有限公司 柔性散热片
US7399919B2 (en) 2002-12-19 2008-07-15 3M Innovative Properties Company Flexible heat sink
KR101065911B1 (ko) * 2002-12-19 2011-09-19 쓰리엠 이노베이티브 프로퍼티즈 컴파니 가요성 열 싱크
USD903610S1 (en) 2019-08-28 2020-12-01 Carbice Corporation Flexible heat sink
USD904322S1 (en) 2019-08-28 2020-12-08 Carbice Corporation Flexible heat sink
US10859330B1 (en) 2019-08-28 2020-12-08 Carbice Corporation Flexible and conformable polymer-based heat sinks and methods of making and using thereof
USD906269S1 (en) 2019-08-28 2020-12-29 Carbice Corporation Flexible heat sink
WO2024217904A1 (fr) * 2023-04-18 2024-10-24 Kerafol Holding Gmbh Matériau de moulage par injection thermoconducteur

Also Published As

Publication number Publication date
AU3330695A (en) 1996-03-14

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