CN102150484A - Thermal Gel Pack - Google Patents

Abstract

A conformable, thermally-conductive gel pack is provided having a thermal gel encapsulated by a compliant packaging material formed from a dielectric polymer. The gel pack is adapted for emplacement between opposed heat transfer surfaces in an electronic device. One heat transfer surface can be part of a heat-generating component of the device, while the other heat transfer surface can be part of a heat sink or a circuit board.

Description

Thermal Gel Pack

Cross References to Related Applications

This application claims the benefit of US Provisional Application No. 61/100,297, filed September 26, 2008, the disclosure of which is incorporated herein by reference.

technical field

The present invention relates to a new thermal product or form factor, the combination of which fully distributes the thermal and mechanical properties of the material as easily as using traditional gap fill pads. In particular, the present invention relates to thermal gel materials encapsulated in compliant polymeric dielectric packages, which can be conveniently used in electronic applications requiring thermal management.

Background technique

The circuit design of modern electronic devices (eg, televisions, radios, computers, medical instruments, business machines, communication equipment, etc.) has become increasingly complex. For example, integrated circuits have been fabricated for these and other devices containing the equivalent of hundreds of thousands of transistors. Despite the increase in design complexity, the size of devices continues to shrink as the ability to manufacture smaller electronic components and pack more of them into smaller and smaller areas improves.

In recent years, electronic devices have become smaller and more densely packed. Designers and manufacturers are now faced with the challenge of dissipating the heat generated in such devices using various thermal management systems. Thermal management has been developed to address the increase in temperature within such electronic devices resulting from the increase in processing speed and power of such devices. New generations of electronic components pack more power into less space; and thus the relative importance of thermal management within overall product designs continues to increase.

An integral part of the thermal design process is selecting the ideal thermal interface material (“TIM”) for a specific product application. New designs have been devised for thermal management to help dissipate heat from electronic devices to further enhance their performance. Other thermal management techniques utilize concepts such as "cold plates" or other heat sinks that can be easily mounted near the electronic components for heat dissipation. The heat sink can be a dedicated thermally conductive metal plate or simply just the chassis or circuit board of the device.

To improve heat transfer efficiency through the interface, a pad or other layer of thermally conductive, electrically insulating material is often interposed between the heat sink and the electronic component to fill any surface irregularities and eliminate air pockets. Materials such as silicone greases or waxes filled with thermally conductive fillers such as aluminum oxide were initially employed for this purpose. Such materials are typically semi-liquid or solid at normal room temperature, but may liquefy or soften at elevated temperatures to flow and better conform to irregularities in interfacial surfaces.

Greases and waxes of the foregoing type are generally not self-supporting or otherwise form stable at room temperature and are considered problematic to apply to heat sinks or interface surfaces of electronic components. Thus, the material is usually provided in the form of a film (which is often preferred for ease of handling), a substrate, a web or other carrier which introduces additional air pockets in or between surfaces where additional air pockets can form. an interface layer. Furthermore, the use of such materials often involves manual handling or downtime by electronics assemblers, which increases manufacturing costs.

Alternatively, another approach is to replace the silicone grease or wax with a cured, flaky material. Such materials may contain one or more thermally conductive particulate fillers dispersed within a polymeric binder, and may be provided in cured sheet, tape, pad or film form. Typical binder materials include silicone, urethane, thermoplastic rubber, and other elastomers, with typical fillers including aluminum oxide, magnesium oxide, zinc oxide, boron nitride, and aluminum nitride.

Examples of the aforementioned interface materials are alumina or boron nitride filled silicone or urethane elastomers. Additionally, US Patent No. 4,869,954 discloses a solidified, form-stable, sheet-like, thermally conductive material for transferring thermal energy. The material is formed by a urethane binder, a curing agent and one or more thermally conductive fillers. The filler may comprise particles of aluminum oxide, aluminum nitride, boron nitride, magnesium oxide or zinc oxide.

Sheets, pads, and tapes of the type described above have gained general acceptance for use as interface materials in conductively cooled electronic component assemblies such as semiconductor chips, as described in more detail in US Patent No. 5,359,768. However, in certain applications, sufficient force from a fastening element (eg, spring, clamp, etc.) is required to keep the material conformal to the interface surface in order to obtain a sufficiently effective heat transfer surface. This represents a clear disadvantage in deploying the material in practical applications.

Recently, phase-change materials have been introduced that are self-supporting and form-stable at room temperature for ease of handling, but liquefy or otherwise soften at temperatures within the operating temperature range of electronic components to form a viscous, thixotropic phase that Better conformality to interface surfaces. The phase change material, which may be supplied as a stand-alone film or as a heated screen printed on a substrate surface, advantageously exhibits conformal flow largely similar to Grease and wax come into play. Such materials are further described in US Patent No. 6,054,198.

For typical commercial applications, thermal interface materials can be supplied in tape or sheet form comprising inner and outer release liners and a thermal compound sandwich. Unless the thermal compound is inherently tacky, one side of the compound layer can be coated with a thin layer of pressure sensitive adhesive (PSA) to apply the compound to the heat transfer surface of the heat sink. To facilitate automated dispensing and application, the outer release liner and compound interlayer of the tape or sheet can be die cut to form a series of individual, pre-designed sized pads. Each pad can thus be removed from the inner release liner and bonded to the heat sink using an adhesive layer in a conventional "peel and stick" application, which can be performed by the heat sink manufacturer.

US Patent No. 6,054,198 discloses a thermally conductive interface for cooling heat generating electronic components with associated heat dissipating components such as heat sinks. The interface is formed as a self-supporting layer of thermally conductive material that is form stable in a first phase at normal room temperature and substantially conformal in a second phase to the interface surface of the electronic component and heat dissipating component. The material has a transition temperature from the first phase to the second phase that is within the operating temperature range of the electronic component.

US Patent No. 7,208,192 discloses applying a thermally and/or electrically conductive compound to fill the gap between the first and second surfaces. The supply of a smooth, form-stable compound is provided as a mixture of the cured polymer gel component and the particulate filler component. The compound is dispensed from a nozzle under applied pressure onto one of the surfaces in contact with the opposing surface to fill a gap therebetween.

The respective disclosures of each of the above-listed patents and patent applications are hereby incorporated by reference in their entirety.

Given the variety of materials and applications currently used in thermal management (as exemplified above), it is expected that continued improvements in thermal management materials and applications will be well received by electronic device manufacturers.

It is therefore an object of the present invention to provide improved thermal management materials that provide high heat transfer efficiency and heat dissipation, are fully conformal to specific applications and are easy to use and manufacture.

Contents of the invention

The present invention relates to thermal gelling materials encapsulated in a dielectric polymer (e.g., polyimide, polyamide, or other such material) that forms a package, pouch, or similar enclosure, so The package, pouch, or similar enclosure imparts the benefits of a fully cured, dispersible gap-fill material without the need to use or purchase expensive dispensing equipment. This allows customers to use ultra-compliant materials for sensitive applications while maintaining the ease of pick-and-place technology and a convenient product form factor.

In one embodiment, the invention is a conformal, thermally conductive interface adapted to be positioned between two heat transfer surfaces to provide a thermal path therebetween, the interface comprising a thermally conductive polymeric gel encapsulated in a compliant package , the compliant package includes a polymeric material. In one aspect, the thermally conductive polymeric gel includes a silicone polymer with a thermally conductive particulate filler (eg, particles of boron nitride) and the polymeric encapsulating material is a dielectric polymer, such as polyimide or polyamide. In one aspect, the package includes two layers of heat-sealable polymeric material encapsulating the thermally conductive gel, wherein optionally one layer includes a layer of thermal tape.

In another embodiment, a conformal thermally conductive interface material is prepared by dispensing a thermally conductive polymer gel onto a first dielectric polymer or thermal tape layer. A second dielectric polymer layer is placed 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 dispensed into rolls on an assembly line using automated handling machines, if desired. The amount of polymerized gel in the gel pack can vary depending on customer requirements and can meet a range of thickness requirements. Additionally the encapsulating material may be torn or slit to allow displacement of the material under load.

The gel pack may be used in an electronic device in which the gel pack may be disposed between a first heat transfer surface and a second heat transfer surface. The first heat transfer surface may be part of a component designed to absorb heat, such as a heat sink or a circuit board. The second heat transfer surface may be part of a heat generating source, such as an electronic component. In use, the gel pack is placed between the first and second surfaces and displaces under low deflection forces, allowing the material to conform to the adjoining surfaces, thereby providing excellent sealing using only low sealing pressures. thermal conductivity.

Description of drawings

Figure 1 is a cross-sectional view of one embodiment of the present invention showing a gel pack comprising a thermally conductive gel sandwiched between two layers of plastic sheet material heat sealed at their edge portions to encapsulate the gel.

Figure 2 is a cross-sectional view of another embodiment of the present invention showing a gel pack comprising thermally conductive gel sandwiched between layers of plastic sheet material and thermal tape at edge portions thereof Heat seal to encapsulate the gel.

Those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, to help improve understanding of embodiments of the invention, the dimensions of some of the elements in the figures may be exaggerated relative to other elements. Certain terminology may be employed in the following description for convenience and not for any purpose of limitation.

Detailed ways

The present invention provides a thermally conductive gel pack suitable for positioning between two heat transfer surfaces of a component used in an electronic device. The gel packs of the present invention have improved heat transfer and handling characteristics for enhanced thermal management compared to other products currently in use.

As used herein, the term "thermal management" refers to the ability to maintain temperature sensitive components in an electronic device within a specified operating temperature to avoid system failure or severe system performance degradation.

The term "EMI shielding" includes and is interchangeable with the following: electromagnetic compatibility (EMC), conductive and/or grounding, corona shielding, radio frequency interference (RFI) shielding, and antistatic (i.e., electrostatic discharge ( ESD) protection).

A "conformal" product is one that exhibits sufficient flexibility to conform to the contours of the interface with minimal or low force deflection characteristics.

As described herein, thermally and/or electrically conductive gel packs of the present invention are primarily described in connection with the use of such gel packs as thermal interface materials interposed between adjacent heat transfer surfaces within thermal management assemblies. The heat transfer surface may be part of a heat generating component, such as an electronic component, or a heat dissipating component, such as a heat sink or an electronic circuit board. However, those skilled in the art will readily appreciate that the gel packs of the present invention may have other uses that are well intended to be within the scope of the present invention.

Thus, according to the present invention there is provided a gel pack comprising a flexible, conformal plastic enclosure (eg a bag or other container) having an internal compartment for containing a thermally conductive substance (eg thermally conductive polymeric gel). Preferably, the plastic is a conformal dielectric polymer such as polyamide or polyimide.

The encapsulation may conveniently be formed from two layers of plastic material by, for example, dispensing a gel onto a first plastic layer and placing a second plastic layer over said first layer to thereby encapsulate the gel Inside the two plastic layers. The plastic layers can then be heat sealed or glued at their overlapping outer edges to form a gel pack. The resulting gel pack is fully conformal to be able to fill between adjoining surfaces of circuit components, circuit boards, and housings of electronic devices and electrical equipment, or between other adjoining surfaces such as those found in building structures, etc. Clearance.

Gels useful as the polymer gel component of the present invention include silicone-based gels, i.e. polysiloxanes such as polyorganosiloxanes as well as other polymer-based gels which may be thermoplastic or thermosetting) such as polyurethane, polyurea, fluoropolymer, chlorosulfonate, polybutadiene, butyl synthetic rubber, neoprene, nitrite, polyisoprene and nitrile rubber (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 ethylene or Propylene - EPDM, EPR or NBR. Suitable thermal gels include THERM-A-GAP ^™ gel products, which are highly conformal, pre-cured, one-part compounds requiring only relatively little compressive force.

As used herein, the term "polymer gel" or "polymeric gel" generally has the conventional meaning of a fluid-extended polymer system, which may comprise a continuous polymeric phase or network (which may be chemically (e.g., ionic) or covalently) or physically cross-linked) and oils (such as silicone or other oils), plasticizers, non-reactive monomers, or other agents that swell the web or otherwise fill the interstices of the web Fluid extender. The crosslink density of such networks and the proportion of extenders can be controlled to tune the modulus (ie, softness) and other properties of the gel. The term "polymer gel" or "polymeric gel" should also be understood to encompass, for example, having a "loose" cross-linked network formed of relatively long cross-linked chains, which can alternatively be broadly classified as having properties similar to Gels are pseudogel or gel-like in their viscoelastic properties but are classified, for example, as materials lacking fluid-extending agents.

According to one aspect of the invention, the polymer gel component is made thermally conductive by loading the polymer gel component with a filler component, which may include one or more thermally conductive particulate fillers. In this regard, the polymer gel component typically forms a binder in which the thermally conductive filler is dispersed. The filler is included in a proportion sufficient to provide the desired thermal conductivity for a given application and will typically be loaded in an amount of between about 20% and about 80% by total weight of the composite. For the purposes of the present invention, the size and shape of the filler is not critical. In this regard, fillers may be of any general shape (broadly referred to as "particulates"), including solid or hollow spherical or microspherical flakes, platelets, irregular shapes, or fibrous (such as chopped or ground fibers or whiskers solids), but preferably will be a powder to ensure uniform dispersion and uniform mechanical and thermal properties. The particle size or distribution of the filler will typically range from about 0.01 mils to about 10 mils (0.25 microns to 250 microns), which may be diameter, accrued diameter, length, or other dimensions of the particles, but may be It further depends on the thickness of the gap to be filled. If desired, the filler can be non-conductive so that the composite can be both dielectric or electrically insulating and thermally conductive. Alternatively, in applications where electrical isolation is not required, the filler can be conductive.

Suitable thermally conductive fillers generally include oxides, nitrides, carbides, diborides, graphite, and metallic particles and mixtures thereof, and more specifically, 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. For economic reasons, aluminum oxide (ie alumina) could be used, while for reasons of improved thermal conductivity, boron nitride would be preferred. After loading with a thermally conductive filler, the composite can typically exhibit a thermal conductivity according to ASTM D5470 of at least about 0.5 W/m-K, which can vary depending on the thickness of the composite layer.

According to another aspect of the invention, the polymer gel component can be rendered conductive by loading it with a conductive filler, which can be provided in addition (i.e., a blend) or instead of a thermally conductive filler. fillers. Furthermore, depending on the filler chosen, such fillers can act as both thermally and electrically conductive fillers. The use of conductive material provides the gel with EMI shielding properties.

Suitable conductive fillers include: precious and non-precious metals such as nickel, copper, tin, aluminum and nickel; precious metals plated with precious metals or non-precious metals such as copper, nickel, aluminum, tin or gold plated with silver; Precious and non-precious metals of precious metals, such as copper or silver coated with nickel; and non-metals coated with precious or non-precious metals, such as graphite, glass, ceramics, plastics, elastomers or mica coated with silver or nickel; mixtures thereof . Broadly, the fillers may likewise be classified in form as "particulates", but the particular shape of such form is not considered critical to the invention, and may comprise conductive materials of the type conventionally referred to herein Any shape involved in the manufacture or formulation of , including hollow or solid microspheres, elastomeric spheres, flakes, platelets, fibers, rods, irregularly shaped particles, or mixtures thereof. Similarly, the particle size of the filler is not considered critical, and it may be narrow or broad in distribution or range, but will generally be from about 0.250 microns to about 250 microns.

)、聚酰胺及其共聚物和掺合物。所述热塑性聚合物可形成为膜且在边缘部分处热密封，借此将热凝胶包封在密封袋或小包中。实际中，将热凝胶沉积在第一聚合物膜层上，且将第二聚合物膜层放在所述第一膜层上并热密封到所述第一膜层。在一个实施例中，第一及第二层两者均为介电聚合物膜层，优选地由相同聚合物形成。在另一实施例中，所述层中的一者(通常为底层)为热胶带。适合的热胶带包含THERMATTACH

导热附着胶带，其是基于聚酰亚胺载体且具有极好的介电强度。Thermal gels are encapsulated in plastic films by encapsulating the gels in a dielectric polymer. Exemplary dielectric polymers include various thermoplastic polymers, such as polyimides (e.g., Kapton

), polyamides and their copolymers and blends. The thermoplastic polymer may be formed into a film and heat sealed at edge portions, thereby enclosing the thermal gel in a sealed bag or packet. In practice, a thermal gel is deposited on a first polymer film layer, and a second polymer film layer is placed on and heat sealed to said first film layer. In one embodiment, both the first and second layers are dielectric polymer film layers, preferably formed from the same polymer. In another embodiment, one of the layers (typically the bottom layer) is thermal tape. Suitable thermal tapes include THERMATTACH

Thermally conductive adhesive tape based on a polyimide carrier with excellent dielectric strength.

Multiple gel packs can be advantageously and efficiently manufactured in an automated assembly process on one assembly line, thereby allowing the packs to be produced in rolls and individually slit prior to use.

The gel pack is adapted for use in an electronic device by being placed between the first heat transfer surface and the second heat transfer surface to provide a thermal path therebetween. A heat transfer surface can be a component designed to absorb heat, such as a heat sink or an electronic circuit board. The other (opposite) heat transfer surface may be a heat generating source, such as a heat generating electronic component. The opposing heat transfer surfaces preferably have a thermal resistance of less than about 1°C-in ² /W (6°C-cm ² /W).

By way of example, typical electronic equipment within the scope of the present invention includes automotive electronic components and systems, telecommunications base stations, and consumer electronics such as computer monitors and plasma televisions.

Referring now to the figures, Figures 1 and 2 show two embodiments of thermal gel packs according to the present invention. In FIG. 1 , a thermogel 1 is shown encapsulated by an upper layer 2 and a lower layer 3 of a dielectric polymer film. Heat seal the edges of the upper and lower film layers to encapsulate the gel. FIG. 2 is similar to FIG. 1 and shows thermal gel 4 encapsulated by an upper dielectric polymer film layer 5 and a lower layer 6 of thermal tape. The thermal gel packs of the present invention may be prepared individually or may be part of a plurality of such packs prepared in an automated manufacturing process.

It is intended that changes may be made to the present invention without departing from the concepts herein set forth, and it is intended that all matter contained in the foregoing description shall be interpreted as illustrative rather than in a limiting sense. All references cited herein, including any priority documents, are hereby expressly incorporated by reference in their entirety.

Claims (26)

1. conformal thermally conductive gel bag, it is suitable for being positioned first heat transfer surface and opposed second heat transfer surface is middle so that hot path to be provided betwixt, described gel pack comprises the heat conduction polymeric gel that is encapsulated in the biddability encapsulation, and described biddability encapsulation comprises polymeric material layer.

2. gel pack according to claim 1, one in wherein said first or second heat transfer surface is positioned on the hot generation source.

3. gel pack according to claim 2, wherein:

Described hot generation source is an electronic building brick; And

Another person in described first or second heat transfer surface is positioned on the dissipation of heat parts.

4. gel pack according to claim 3, wherein said dissipation of heat parts are fin or circuit board.

5. gel pack according to claim 1, wherein said gel comprises silicone polymer.

6. gel pack according to claim 1, the wherein said gel-filled conductive particles filler that has.

7. gel pack according to claim 6, wherein said particulate filler is selected from the group that is made up of following: boron nitride, titanium diboride, aluminium nitride, carborundum, graphite, metal, metal oxide and composition thereof.

8. gel pack according to claim 6, wherein said through the gel filled described filler that comprises between about by weight 20% to 80%.

9. gel pack according to claim 6, wherein said filler has the thermal conductivity at least about 20W/m-K.

10. gel pack according to claim 6, described through the gel filled thermal conductivity that has at least about 0.5W/m-K.

11. gel pack according to claim 1, its median surface have less than about 1 ℃-in ²(6 ℃-cm of/W ²/ W) thermal impedance.

12. gel pack according to claim 1, the described polymeric material that wherein forms the described layer of described encapsulation is a dielectric.

13. gel pack according to claim 1, the described polymeric material that wherein forms the described layer of described encapsulation is selected from the group that is made up of following: polyimides, polyamide and copolymer thereof and admixture.

14. a heat management sub-assembly, it comprises:

First heat transfer surface;

Second heat transfer surface, itself and described first heat transfer surface are opposed; And

Conformal thermally conductive gel bag, its be placed in described first with described second heat transfer surface in the middle of so that thermally conductive pathways to be provided betwixt, described gel pack comprises the heat conduction polymeric gel that is encapsulated in the biddability encapsulation, and described biddability encapsulation comprises at least one polymeric material layer.

15. sub-assembly according to claim 14, one in wherein said first or second heat transfer surface is positioned on the hot generation source.

16. sub-assembly according to claim 15, wherein:

Described hot generation source is an electronic building brick; And

Another person in described first or second heat transfer surface is positioned on the dissipation of heat parts.

17. sub-assembly according to claim 16, wherein said dissipation of heat parts are fin or circuit board.

18. sub-assembly according to claim 14, wherein said gel comprises silicone polymer.

19. sub-assembly according to claim 14, the wherein said gel-filled conductive particles filler that has.

20. sub-assembly according to claim 19, wherein said particulate filler is selected from the group that is made up of following: boron nitride, titanium diboride, aluminium nitride, carborundum, graphite, metal, metal oxide and composition thereof.

21. sub-assembly according to claim 19 is wherein said through the gel filled described filler that comprises between about by weight 20% to about 80%.

22. sub-assembly according to claim 19, wherein said filler has the thermal conductivity at least about 20W/m-K.

23. sub-assembly according to claim 19 is described through the gel filled thermal conductivity that has at least about 0.5W/m-K.

24. sub-assembly according to claim 14, its median surface have less than about 1 ℃-in ²(6 ℃-cm of/W ²/ W) thermal impedance.

25. sub-assembly according to claim 14, the described polymeric material that wherein forms the described layer of described encapsulation is a dielectric.

26. sub-assembly according to claim 14, the described polymeric material that wherein forms the described layer of described encapsulation is selected from the group that is made up of following: polyimides, polyamide and copolymer thereof and admixture.

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