Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K7/00—Constructional details common to different types of electric apparatus
  • H05K7/20—Modifications to facilitate cooling, ventilating, or heating
  • H05K7/2039—Modifications to facilitate cooling, ventilating, or heating characterised by the heat transfer by conduction from the heat generating element to a dissipating body
  • H05K7/20436—Inner thermal coupling elements in heat dissipating housings, e.g. protrusions or depressions integrally formed in the housing
  • H05K7/20445—Inner thermal coupling elements in heat dissipating housings, e.g. protrusions or depressions integrally formed in the housing the coupling element being an additional piece, e.g. thermal standoff
  • H05K7/20454—Inner thermal coupling elements in heat dissipating housings, e.g. protrusions or depressions integrally formed in the housing the coupling element being an additional piece, e.g. thermal standoff with a conformable or flexible structure compensating for irregularities, e.g. cushion bags, thermal paste
• • 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
  • H01L23/3737—Organic materials with or without a thermoconductive filler
• • 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
• • 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
  • H01L2924/095—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00 with a principal constituent of the material being a combination of two or more materials provided in the groups H01L2924/013 - H01L2924/0715
  • H01L2924/097—Glass-ceramics, e.g. devitrified glass
  • H01L2924/09701—Low temperature co-fired ceramic [LTCC]
• • 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
  • H01L2924/30—Technical effects
  • H01L2924/301—Electrical effects
  • H01L2924/3011—Impedance

Definitions

• the present invention relates to a new thermal product or form factor which combines the thermal and mechanical performance of a fully dispensable material with the ease of use of traditional gap filler pads.
• the invention relates to a thermal gel material encapsulated in a compliant polymeric dielectric package that can be conveniently utilized in an electronic application requiring thermal management.
• Circuit designs for modem electronic devices such as televisions, radios, computers, medical instruments, business machines, communications equipment, and the like have become increasingly complex. For example, integrated circuits have been manufactured for these and other devices which contain the equivalent of hundreds of thousands of transistors. Although the complexity of the designs has increased, the size of the devices has continued to shrink with improvements in the ability to manufacture smaller electronic components and to pack more of these components in an ever smaller area.
• thermal management has evolved to address the increased temperatures created within such electronic devices as a result of the increased processing speed and power of these devices.
• the new generation of electronic components squeeze more power into a smaller space; and hence the relative importance of thermal management within the overall product design continues to increase.
• TIM Thermal Interface Material
• New designs have been devised for thermal management to help dissipate the heat from electronic devices for further enhancing their performance.
• Other thermal management techniques utilize concepts such as a "cold plate”, or other heat sinks which can be easily mounted in the vicinity of the electronic components for heat dissipation.
• the heat sink may be a dedicated, thermally-conductive metal plate, or simply the chassis or circuit board of the device.
• a pad or other layer of a thermally-conductive, electrically-insulating material often is interposed between the heat sink and electronic component to fill in any surface irregularities and eliminate air pockets.
• materials such as silicone grease or wax filled with a thermally-conductive filler such as aluminum oxide.
• thermally-conductive filler such as aluminum oxide.
• Such materials usually are semi-liquid or solid at normal room temperature, but may liquefy or soften at elevated temperatures to flow and better conform to the irregularities of the interface surfaces.
• the greases and waxes of the aforementioned types generally are not self- supporting or otherwise form-stable at room temperature, and are considered to be messy to apply to the interface surface of the heat sink or electronic component. Consequently, these materials are typically provided in the form of a film, which often is preferred for ease of handling, a substrate, a web, or other carrier which introduces another interface layer in or between the surfaces in which additional air pockets may be formed. Moreover, the use of such materials typically involves hand application or lay-up by the electronics assembler which increases manufacturing costs.
• a cured, sheet-like material in place of the silicone grease or wax.
• Such materials may contain one or more thermally- conductive particulate fillers dispersed within a polymeric binder, and may be provided in the form of cured sheets, tapes, pads, or films.
• Typical binder materials include silicones, urethanes, thermoplastic rubbers, and other elastomers, with typical fillers including aluminum oxide, magnesium oxide, zinc oxide, boron nitride, and aluminum nitride.
• Exemplary of the aforesaid interface materials are alumina or boron nitride-filled silicone or urethane elastomers.
• U.S. Patent No. 4,869,954 discloses a cured, form-stable, sheet-like, thermally-conductive material for transferring thermal energy.
• the material is formed of a urethane binder, a curing agent, and one or more thermally conductive fillers.
• the fillers which may include particles of aluminum oxide, aluminum nitride, boron nitride, magnesium oxide, or zinc oxide.
• Sheets, pads, and tapes of the above-described types have garnered general acceptance for use as interface materials in the conductive cooling of electronic component assemblies such as semiconductor chips, as described in more detail in U.S. Patent No. 5,359,768.
• fastening elements such as springs, clamps, and the like are required to apply enough force to conform these materials to the interface surfaces in order to attain enough surface for efficient thermal transfer. This represents a distinct disadvantage for deploying these materials in practical applications.
• Phase-change materials have recently been introduced which are self-supporting and form-stable at room temperature for ease of handling, but which liquefy or otherwise soften at temperatures within the operating temperature range of the electronic component to form a viscous, thixotropic phase which better conforms to the interface surfaces.
• phase-change materials which may be supplied as free-standing films, or as heated screens printed onto a substrate surface, advantageously function much like greases and waxes in conformably flowing within the operating temperature of the component under relatively low clamping pressures. Such materials are further described in U.S. Patent No. 6,054,198.
• the thermal interface material may be supplied in the form of a tape or sheet which includes an inner and outer release liner and an interlayer of a thermal compound.
• a thermal compound Unless the thermal compound is inherently tacky, one side of the compound layer may be coated with a thin layer of a pressure-sensitive adhesive (PSA) for application of the compound to the heat transfer surface of a heat sink.
• PSA pressure-sensitive adhesive
• the outer release liner and compound interlay er of the tape or sheet may be die cut to form a series of individual, pre-sized pads. Each pad thus may be removed from the inner release liner and bonded to the heat sink using the adhesive layer in a conventional "peel and stick" application which may be performed by the heat sink manufacturer.
• U.S. Patent No. 6,054,198 discloses a thermally-conductive interface for cooling a heat-generating electronic component having an associated thermal dissipation member such as a heat sink.
• the interface is formed as a self-supporting layer of a thermally- conductive material which is form-stable at normal room temperature in a first phase, and substantially conformable in a second phase to the interface surfaces of the electronic component and thermal dissipation member.
• the material has a transition temperature from the first phase to the second phase which is within the operating temperature range of the electronic component.
• U.S. Patent No. 7,208,192 discloses the application of a thermally and/or electrically conductive compound to fill a gap between a first and second surface.
• a supply of fluent, form-stable compound is provided as an admixture of a cured polymer gel component and a particulate filler component.
• the compound is dispensed from a nozzle under an applied pressure onto one of the surfaces which is contacted with the opposing surface to fill the gap there between.
• the invention is a thermal gel material encapsulated in a dielectric polymer, such as a polyimide, polyamide or other such material, formed into a package, a bag or similar enclosure that confers the benefits of a fully cured, dispensable gap filler material without the need for using or investing in expensive dispensing equipment. This allows the customer to use ultra-compliant materials for sensitive applications, while maintaining the ease of pick-and-place technology and a convenient product form factor.
• a dielectric polymer such as a polyimide, polyamide or other such material
• the invention is a conformable, thermally-conductive interface adapted to be positioned between two heat transfer surfaces to provide a thermal pathway there between, the interface comprising a thermally conductive polymeric gel encapsulated in a compliant package comprising a polymeric material.
• the thermally conductive polymeric gel comprises a silicone polymer containing a thermally conductive particulate filler, such as particles of boron nitride
• the polymeric packaging material is a dielectric polymer such as a polyimide or a polyamide.
• the package comprises two layers of heat sealable polymeric material encapsulating the thermally conductive gel, with one layer optionally comprising a thermal tape layer.
• a conformable, thermally-conductive interface material is prepared by dispensing a thermally conductive polymeric gel onto a first layer of a dielectric polymer or a thermal tape. A second layer of dielectric polymer is place over the first layer, and heat sealed (or sealed with an adhesive) to the first layer to encapsulate the thermally conductive gel.
• the resulting gel packs can be manufactured as discrete items or using automated processing machinery, if desired, to dispense the gel pack in a roll on an assembly line.
• the amount of polymeric gel in the gel pack can be varied depending on customer requirements and can address a range of thickness requirements.
• the packaging material can additionally be slit or cut to allow for material displacement under load.
• the gel pack can be used in an electronic device where it can be disposed between a first heat transfer surface and a second heat transfer surface.
• the first heat transfer surface can be part of a component designed to absorb heat, such as a heat sink or a circuit board.
• the second heat transfer surface can be part of a heat generating source, such as an electronic component.
• the gel pack is place between the first and second surfaces and is displaced under low deflection forces allowing the material to conform to the joint surfaces, thereby providing excellent thermal conductivity using only a low closure pressure.
• FIG. 1 is a cross-sectional view of one embodiment of the invention showing a gel pack comprising a thermally conductive gel sandwiched between two layers of plastic sheet material heat sealed at the edge portions thereof to encapsulate the gel.
• FIG. 2 is a cross-sectional view of another embodiment of the invention showing a gel pack comprising a thermally conductive gel sandwiched between a layer of plastic sheet material and a thermal tape heat sealed at the edge portions thereof to encapsulate the gel.
• the invention provides a thermally conductive gel pack adapted to be positioned between two heat transfer surfaces of components used in electronic devices.
• the gel pack of the invention has improved heat transfer and handling characteristics for enhanced thermal management as compared to other products currently in use.
• thermal management refers to the capability of keeping temperature-sensitive elements in an electronic device within a prescribed operating temperature in order to avoid system failure or serious system performance degradation.
• EMI shielding includes, and is interchangeable with, electromagnetic compatibility (EMC), electrical conduction and/or grounding, corona shielding, radio frequency interference (RFI) shielding, and anti-static, i.e., electro-static discharge (ESD) protection.
• EMC electromagnetic compatibility
• RFID radio frequency interference
• ESD electro-static discharge
• a “conformable” product is one which displays sufficient flexibility to conform to the contours of the interface with minimal or low force deflection characteristics.
• thermally and/or electrically-conductive gel packs of the invention are principally described in connection with the usage of such gel packs within a thermal management assembly as a thermal interface material interposed between adjacent heat transfer surfaces.
• the heat transfer surfaces may be part of heat generating components, such as electronic components, or heat dissipation components, such as heat sinks or electronic circuit boards.
• present gel packs can have other uses which are fully intended to be within the scope of the present invention.
• a gel pack comprising a flexible, conformable plastic package, such as a bag or other container, having an interior compartment for containing a thermal conductive substance, such as a thermally conductive polymeric gel.
• the plastic is a conformable dielectric polymer, such as a polyamide or a polyimide.
• the package can be conveniently formed from two layers of plastic material by, for instance, dispensing the gel onto a first plastic layer, and placing a second plastic layer over the first layer to thereby encapsulate the gel within both layers of plastic.
• the plastic layers can then be heat sealed or glued at the outer edges where the layers overlap to form the gel pack.
• the resulting gel pack is fully conformable so as to be capable of filling gaps between adjoining surfaces of the circuitry components, circuit boards, and housings of electronic devices and electrical equipment, or between other adjoining surfaces such as may be found in building structures and the like.
• Gels useful as the polymer gel component of the invention include gels based on silicones, i.e., polysiloxanes, such as polyorganosiloxane, as well as gels based on other polymers, which may be thermoplastic or thermosetting, such as polyurethanes, polyureas, fluoropolymers, chlorosulfonates, polybutadienes, butyls, neoprenes, nitrites, polyisoprenes, and buna-N, copolymers such as ethylene-propylene (EPR), styrene- isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), ethylene-propylene-diene monomer (EPDM), nitrile-butadiene (NBR), styrene-ethylene-butadiene (SEB), and styrene-butadiene (SBR), and blends thereof such as
• polymer gel or “polymeric gel” generally have their conventional meaning of a fluid-extended polymer system which may include a continuous polymeric phase or network, which may be chemically, e.g., ionically or covalently, or physically cross-linked, and an oil, such as a silicone or other oil, a plasticizer, unreacted monomer, or other fluid extender which swells or otherwise fills the interstices of the network.
• an oil such as a silicone or other oil, a plasticizer, unreacted monomer, or other fluid extender which swells or otherwise fills the interstices of the network.
• the cross-linking density of such network and the proportion of the extender can be controlled to tailor the modulus, i.e., softness, and other properties of the gel.
• polymer gel or "polymeric gel” should also be understood to encompass materials which alternatively may be classified broadly as pseudogels or gel- like having viscoelastic properties similar to gels, such as by having a "loose" cross- linking network formed by relatively long cross-link chains, but as, for example, lacking a fluid-extender.
• the polymer gel component is rendered thermally-conductive by loading the gel with a filler component which may comprise one or more thermally-conductive particulate fillers.
• the polymer gel component generally forms a binder into which the thermally-conductive filler is dispersed.
• the filler is included in proportion sufficient to provide the thermal conductivity desired for the intended application, and generally will be loaded in an amount of between about 20% and about 80% by total weight of the compound.
• the size and shape of the filler is not critical for the purposes of the present invention.
• the filler may be of any general shape, referred to broadly as "particulate,” including solid or hollow spherical or microspherical flake, platelet, irregular, or fibrous, such as chopped or milled fibers or whiskers, but preferably will be a powder to assure uniform dispersal and homogeneous mechanical and thermal properties.
• the particle size or distribution of the filler typically will range from between about 0.01 mil to about 10 mil (0.25 ⁇ m - 250 ⁇ m), which may be a diameter, imputed diameter, length, or other dimension of the particle, but may further vary depending upon the thickness of the gap to be filled.
• the filler may be electrically-nonconductive such that compound may be both dielectric or electrically-insulating and thermally-conductive. Alternatively, the filler may be electrically-conductive in applications where electrical isolation is not required.
• Suitable thermally-conductive fillers generally include oxide, nitride, carbide, diboride, graphite, and metal particles, and mixtures thereof, and more particularly boron nitride, titanium diboride, aluminum nitride, silicon carbide, graphite, metals such as silver, aluminum, and copper, metal oxides such as aluminum oxide, magnesium oxide, zinc oxide, beryllium oxide, and antimony oxide, and mixtures thereof.
• Such fillers characteristically exhibit a thermal conductivity of at least about 20 W/m-K.
• an aluminum oxide, i.e., alumina may be used, while for reasons of improved thermal conductivity a boron nitride would be preferred.
• the compound typically may exhibit a thermal conductivity, per ASTM D5470, of at least about 0.5 W/m-K, which may vary depending upon the thickness of the compound layer.
• the polymer gel component can be rendered electrically-conductive by loading with an electrically- conductive filler, which may be provided in addition to, i.e., a blend, or instead of a thermally-conductive filler. Also, depending upon the filler selected, such filler may function as both a thermally and an electrically-conductive filler.
• an electrically- conductive filler which may be provided in addition to, i.e., a blend, or instead of a thermally-conductive filler.
• such filler may function as both a thermally and an electrically-conductive filler.
• Suitable electrically-conductive fillers include: noble and non-noble metals such as nickel, copper, tin, aluminum, and nickel; noble metal-plated noble or non-noble metals such as silver-plated copper, nickel, aluminum, tin, or gold; non-noble metal- plated noble and non-noble metals such as nickel-plated copper or silver; and noble or non-noble metal plated non-metals such as silver or nickel-plated graphite, glass, ceramics, plastics, elastomers, or mica; and mixtures thereof.
• noble and non-noble metals such as nickel, copper, tin, aluminum, and nickel
• noble metal-plated noble or non-noble metals such as silver-plated copper, nickel, aluminum, tin, or gold
• non-noble metal- plated noble and non-noble metals such as nickel-plated copper or silver
• noble or non-noble metal plated non-metals such as silver or nickel-plated graphite, glass,
• the filler again may be broadly classified as "particulate" in form, although the particular shape of such form is not considered critical to the present invention, and may include any shape that is conventionally involved in the manufacture or formulation of conductive materials of the type herein involved including hollow or solid microspheres, elastomeric balloons, flakes, platelets, fibers, rods, irregularly-shaped particles, or a mixture thereof.
• the particle size of the filler is not considered critical, and may be or a narrow or broad distribution or range, but in general will be from about 0.250 ⁇ m to about 250 ⁇ m.
• the thermal gel is packaged in a plastic film by encapsulating the gel in a dielectric polymer.
• dielectric polymers include various thermoplastic polymers, such as polyimides (e.g. Kapton®), polyamides, and copolymers and blends thereof. These thermoplastic polymers can be formed into films and heat sealed at the edge portions, thereby enclosing the thermal gel in a sealed bag or pouch.
• the thermal gel is deposited on a first layer of polymer film, and a second layer of polymer film is placed over and heat sealed to the first film layer.
• both the first and second layers are dielectric polymer film layers, preferably formed from the same polymer.
• one of the layers, typically the bottom layer is a thermal tape. Suitable thermal tapes include the THERMATTACH® thermally conductive attachment tapes, which are based on a polyimide carrier and have excellent dielectric strength.
• Multiple gel packs can be advantageously and efficiently manufactured in an automated assembly process on an assembly line, thereby allowing the packs to be produced in rolls and individually cut prior to use.
• the gel packs are adapted to be used with electronic equipment by emplacement intermediate a first heat transfer surface and a second heat transfer surface to provide a thermal pathway there between.
• One heat transfer surface can be a component designed to absorb heat, such as a heat sink or an electronic circuit board.
• the other (opposed) heat transfer surface can be a heat generating source, such as a heat generating electronic component.
• the opposed heat transfer surfaces preferably have a thermal impedance of less than about 1 °C-in 2 /W (6 0 C-Cm 2 AV)-
• Typical electronic equipment within the scope of the present invention include, by way of example, automotive electronic components and systems, telecom base stations, and consumer electronics, such as computer monitors and plasma TVs.
• FIGS. 1 and 2 show two embodiments of the thermal gel packs according to the present invention.
• thermal gel 1 is shown encapsulated by an upper layer 2 and a lower layer 3 of a dielectric polymer film. The edges of the upper and lower layers of film are heat sealed to enclose the gel.
• FIG. 2 is similar to FIG. 1 and shows thermal gel 4 encapsulated by an upper film layer of dielectric polymer 5 and a lower layer of a thermal tape 6.
• the thermal gel packs of the invention can be prepared individually, or can be part of a number of such packs prepared in an automated manufacturing process.

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

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• 2009
  • 2009-09-24 EP EP09792939A patent/EP2329702A1/en not_active Withdrawn
  • 2009-09-24 KR KR1020117005512A patent/KR20110076875A/ko not_active Application Discontinuation
  • 2009-09-24 US US13/058,356 patent/US20110308781A1/en not_active Abandoned
  • 2009-09-24 CN CN2009801355709A patent/CN102150484A/zh active Pending
  • 2009-09-24 JP JP2011529219A patent/JP2012503890A/ja active Pending
  • 2009-09-24 WO PCT/US2009/058188 patent/WO2010036784A1/en active Application Filing
  • 2009-09-25 TW TW098132540A patent/TWI457425B/zh active

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