JP2011023670A - Anisotropic thermally-conductive element, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropic thermally-conductive element capable of efficiently conducting heat of a heat source in the thickness direction of the thermally-conductive element while keeping strength, and to provide a method of manufacturing the same. <P>SOLUTION: The anisotropic thermally-conductive element 1 for moving heat from a heat source H includes: a structure 3 with a graphene sheet 2 laminated thereon along a surface intersecting with a contact surface with the heat source H; and a support member 4 covering a circumferential part of the structure 3. The anisotropic thermally-conductive element is manufactured by: a covering step of covering the structure with the graphene sheet laminated thereon with the support member; a cutting step of cutting the structure along a surface intersecting with the lamination direction of the graphene sheet after the covering step; and a surface treatment step of executing a surface treatment to the cut surface after the cutting step. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an anisotropic heat conductive element and a method for manufacturing the same.

  A graphite sheet or a graphite film is used as an element for effectively moving heat generated from an electronic device or an electronic device to dissipate heat.

  Graphite sheets with a stack of graphene sheets with six-membered rings linked by covalent bonds, and each graphene sheet bonded with van der Waals forces, is a hot spot generated in electronic equipment and electronic devices that are heat sources. Widely used as a heat conduction element for reducing or efficiently transferring heat from a heat source to a radiator.

  When using a heat conduction element, it is necessary to install it in close contact with the heat source, but graphite is generally brittle in composition and easily collapses, so contact with the heat source and tightening force at the attachment part The graphite surface is usually coated with a resin such as aluminum or PET. However, if the thickness of the covering member is large, a sufficient heat conduction effect cannot be obtained. There was a problem.

  Therefore, Patent Document 1 proposes a heat conductor configured such that a metal is embedded in a part of graphite and a heat receiving portion from a heat source is in contact with the metal.

JP 2008-28283 A

  However, graphite is an anisotropic heat conduction element whose in-plane heat transfer coefficient is larger than the heat transfer coefficient in the thickness direction, and has excellent characteristics of transferring heat from the heat source in the surface direction, but in the thickness direction. It was difficult to transfer heat efficiently.

  Furthermore, when graphite is disposed between a heat source and a heat radiating element such as a heat radiating fin, a silicone-based or epoxy-based resin material is used as an adhesive for each bonding layer. The heat dissipation loss due to thermal resistance in the case was also a problem.

  An object of the present invention is to provide an anisotropic heat conductive element capable of efficiently conducting heat from a heat source in the thickness direction of the heat conductive element while maintaining strength, and a method for manufacturing the same.

  In order to achieve the above-described object, the anisotropic heat conductive element according to the present invention is characterized by an anisotropic heat conductive element that transfers heat from a heat source as described in claim 1 of the claims. In addition, the structure includes a structure in which graphene sheets are laminated along a surface intersecting with a contact surface with a heat source, and a support member that covers a peripheral portion of the structure.

  According to the above-described configuration, the structure is configured such that the graphene sheets are stacked along the plane intersecting the contact surface with the heat source, and thus high heat conduction in the plane on which the graphene sheets are stacked. Utilizing the rate, the heat of the heat source can be efficiently conducted in the thickness direction of the heat conducting element. Moreover, since the peripheral portion of the structure is covered with the support member, it is possible to avoid breakage due to mechanical stress with respect to contact with the heat source, tightening force at the mounting portion, or the like.

  As described in claim 2, the second characteristic configuration is that, in addition to the first characteristic configuration, a metal layer is formed on a contact surface with the heat source. And can be easily soldered.

  As described in claim 3, the third characteristic configuration is that, in addition to the first characteristic configuration, a ceramic layer is formed on the contact surface with the heat source, and is electrically insulated from the heat source and the like. It is possible to efficiently conduct heat while ensuring the above.

  The fourth feature configuration is that, in addition to any of the first to third feature configurations, the structure body is impregnated with resin as described in claim 4, and the structure body is made of resin. By impregnating, the mechanical strength of the structure can be further increased.

  The fifth feature configuration is that, in addition to any one of the first to fourth feature configurations, the structure is a highly oriented pyrolytic graphite, as described in claim 5. By using highly oriented pyrolytic graphite having higher thermal conductivity than graphite, the thermal conductivity efficiency can be dramatically increased.

  In the sixth feature configuration, as described in claim 6, in addition to the fifth feature configuration, the structure is a highly oriented pyrolytic graphite having a thermal conductivity of 1500 W / mK or more. It is in. As such highly oriented pyrolytic graphite, for example, trade name PYROID HT manufactured by MINTEQ International Inc. of the United States can be used.

  In addition to any one of the first to sixth feature configurations, the seventh feature configuration is that a mounting portion to a heat source is provided on the support member, as described in claim 7. By providing the attachment portion on the support member, the attachment can be made to the heat source without causing damage to the structure.

  The characteristic configuration of the electronic device according to the present invention is that an anisotropic heat conducting element having any one of the first to seventh characteristic configurations is incorporated as described in claim 8.

  The first characteristic configuration of the method for manufacturing an anisotropic heat conductive element according to the present invention is, as described in claim 9, a covering step of covering a structure on which a graphene sheet is laminated with a support member, and a covering step It is in the point including the cutting process cut | disconnected along the surface which cross | intersects the lamination direction of a graphene sheet later, and the surface treatment process which surface-treats to a cut surface after a cutting process.

  In the second characteristic configuration, as described in claim 10, in addition to the first characteristic configuration of the method for manufacturing an anisotropic thermal conduction element, the structure is impregnated with resin before the covering step. The structure further includes an impregnation step, and the structure can be further strengthened by impregnating the structure with resin in the impregnation step.

  In the second characteristic configuration, as described in claim 11, in addition to the first or second characteristic configuration of the method for manufacturing an anisotropic thermal conduction element, the covering step is performed in the stacking direction of the graphene sheets. A plurality of structures are superimposed on each other, and the plurality of superimposed structures are integrally covered with a support member, and the plurality of structures are superimposed along the stacking direction of the graphene sheets This makes it possible to manufacture an anisotropic heat conduction element having a large contact area with the heat generating portion.

  As described above, according to the present invention, an anisotropic heat conducting element capable of efficiently conducting heat from a heat source in the thickness direction of the heat conducting element while maintaining the strength and a method for manufacturing the same are provided. Can now.

Explanatory drawing of anisotropic heat conduction element by this invention Illustration of the structure of graphite Explanatory drawing which shows the heat conduction direction of the anisotropic heat conductive element by this invention Explanatory drawing of the manufacturing method of the anisotropic heat conductive element by this invention Explanatory drawing of the manufacturing method of the anisotropic heat conductive element by this invention The exploded perspective view which shows an example of the assembly method of the anisotropic heat conductive element by this invention Sectional drawing which shows an example of the assembly | attachment method of the anisotropic heat conductive element by this invention Explanatory drawing of the manufacturing method of the highly oriented pyrolytic graphite used for the anisotropic heat conductive element by this invention

  The anisotropic heat conducting device and the manufacturing method thereof according to the present invention will be described below.

  As shown in FIG. 1, an anisotropic heat conductive element 1 that transfers heat from a heat source H includes a structure 3 in which a graphene sheet 2 is laminated along a surface that intersects a contact surface with the heat source H, and a structure. 3 is provided.

  As shown in FIG. 2, the structure 3 includes a crystal structure in which graphene sheets 2 in which six-membered rings are connected by covalent bonds are stacked, and each graphene sheet 2 is bonded by van der Waals force, from 0.25 mm It has a thickness of 20 mm and a size of about 300 mm square.

  The structure 3 has a characteristic that the thermal conductivity in the plane of the graphene sheet 2, that is, in the XY plane, is larger than the thermal conductivity in the thickness direction, that is, the Z direction.

  Therefore, as shown in FIG. 3, by arranging the XY plane of the graphene sheet 2 constituting the structure 3 so as to intersect, preferably orthogonally intersect, the contact surface C with the heat source H, The anisotropic thermal conduction element 1 which can efficiently transfer heat in the thickness direction of the structure 3 by efficiently utilizing the high thermal conductivity can be configured.

  As shown in FIG. 4, such an anisotropic heat conductive element 1 includes a coating process in which a structure 3 on which a graphene sheet 2 is laminated is coated with a resin that is an example of a support member 4, and graphene after the coating process. It can manufacture by performing the cutting process cut | disconnected along the surface which cross | intersects the lamination direction of the sheet | seat 2, and the surface treatment process which surface-treats to a cut surface after a cutting process.

  In the coating step, the surface of the structure 3 is coated with the resin R so that the thickness is several mm to several tens mm. In the cutting step, after the resin is solidified, a cutting process is performed at a predetermined pitch set to several mm to several tens of mm along a plane P perpendicular to the XY plane using a diamond cutter or the like. As a result, the anisotropic heat conducting element 1 shown in FIG. 1 is obtained.

  As the resin used at this time, a thermosetting resin such as a phenol resin, a fluorine resin, an epoxy resin, a polyimide resin, or a silicone resin can be suitably selected, and the structure 3 is fixed at a predetermined position in the mold. And the surface of the structure 3 can be coat | covered with resin R by adding a hardening | curing agent to a thermosetting resin and performing heat processing. These are merely examples, and are appropriately selected in consideration of the heat-resistant temperature and the like.

  Moreover, as a thermoplastic resin, polycarbonate which is general-purpose engineering plastic, polyamide imide which is super engineering plastic, polyphenylene sulfide, polyether sulfone, polyphenylene ether, polysulfone, tetrafluoroethylene and the like can be used.

  Furthermore, a resin in which high heat resistance and dimensional stability are improved by combining the above-described thermosetting or thermoplastic resin with an inorganic filler or an organically modified filler can also be used. Furthermore, a resin or the like to which an amine or a silicone is added can be used to improve adhesion.

  Furthermore, an ultraviolet curable epoxy resin, an acrylic resin, a silicone resin, or the like can be used, and is particularly compatible with an epoxy resin having high adhesion in a high temperature environment.

In addition to the resin, a metal, ceramic, or the like can be used as the indicating member.
It is also possible to cover the periphery of the structure with a metal such as Al, Cu, Ni, or Au. Either a wet method such as plating or a dry method such as sputtering can be used. In addition, adhesion can be improved by using a metal such as Ti or Co, which is generally familiar with carbon, or an alloy containing the component as a base.

  It is also possible to cover the periphery of the structure with a ceramic such as alumina, zirconia, silicon carbide, boron nitride, or aluminum nitride. After the ceramic is made into a slurry and the periphery of the structure is coated, a method of performing hot pressing or the like, or a dry method such as sputtering can be used. In addition, as described above, the graphite surface is metallized, thereby imparting gradient functionality, and it is possible to reduce thermal stress and improve adhesion.

  If the impregnation step of impregnating the structure 3 with resin is further performed using a vacuum impregnation method or the like before the coating step, the mechanical strength of the structure can be further increased. The resin used at this time is the same as described above, but it is particularly preferable to use an epoxy resin or a phenol resin.

  In addition, when the thickness of the structure 3 shown in FIG. 2 is thin, the plurality of structures 3 are overlapped in advance along the stacking direction of the graphene sheets, and the plurality of overlapped structures 3 are integrated as a support member 4. By coating with, the anisotropic heat conductive element 1 having a large contact area with the heat generating part H can be manufactured.

  Subsequently, as shown in FIG. 5 (a), when a polishing process is performed in which the surface of the structure 3 after the cutting process is polished by the polishing apparatus 30, and the surface becomes smooth, as shown in FIG. 5 (b). In addition, a film forming process for forming the metal layer M on the surface is performed.

  In the film forming process, a titanium (Ti) layer 5 which becomes an active species is formed on the surface of the structure 3 and the support member 4, and a nickel (Ni) layer or a copper (Cu) layer 6 is formed thereon, and further a gold An (Au) layer 7 is formed. The thickness of each metal layer is preferably around 0.3 μm.

  As a film formation method, any one of a dry method such as a sputtering method and a vapor deposition method and a wet method such as a plating method can be used.

  Since the graphite constituting the structure 3 and the heat source H cannot be directly soldered, the metal layer M is formed in the film forming process, and the heat source H is soldered through the metal layer M. By soldering through the metal layer M, the heat source H can be firmly bonded. In this case, since the film thickness of the metal layer M is around 1 μm, the thermal conductivity is not impaired so much.

  In addition, when it is necessary to conduct heat in a state electrically insulated from the heat source H, a ceramic such as alumina, silicon carbide, boron nitride, or aluminum nitride is sprayed on the surface of the structure 3 after the polishing process. By performing the thermal spraying process, an insulating film made of a ceramic layer can be easily formed.

  By performing surface treatment using a plasma method, a laser method, or the like before the thermal spraying process and activating the surface of the structure 3, the adhesion performance of the ceramic in the thermal spraying process can be improved.

  It is also possible to form a metal layer M and a ceramic layer on both the front and back surfaces of the structure 3 and the support member 4 depending on the application. From the viewpoint of heat resistance of the support member 4, a ceramic layer only on the surface of the structure 3 may be formed.

  That is, the surface treatment process according to the present invention is performed by any one or combination of polishing process, film forming process, and spraying process.

  Furthermore, as shown in FIG. 5C, the support member 4 covering the periphery of the structure 3 is formed with screws or bolt holes 4a as attachment portions to the heat source H, heat sink, etc. The body 3 can be easily and firmly attached to the heat source H or the like without causing damage to the body 3.

  In addition, it is also possible to apply an adhesive to the contact surface between the structure 3 and the heat source H and bond them.

  FIG. 6 and FIG. 7 show an example of a configuration in the case where the heat generated by the heat source H is radiated using the anisotropic heat conductive element 1 manufactured as described above.

  This is an example in which heat is conducted in the thickness direction from the heat source H bonded and fixed on the ceramic substrate 10 through the anisotropic heat conducting element 1 and is radiated by the heat sink 11 disposed on the back surface of the anisotropic heat conducting element 1. . The anisotropic heat conducting element 1 is sandwiched between the ceramic substrate 10 and the heat sink 11 (radiating fin) and fixed with screws 12 and nuts 13 through screw holes 10a, 4a, 11a formed in the ceramic substrate 10 and ceramics 10 respectively. The substrate 10 and the anisotropic heat conductive element 1, and the anisotropic heat conductive element 1 and the heat sink 11 are firmly fixed in close contact with each other.

  In FIG. 7, reference numeral 8 is a solder layer, and reference numeral 9 is a metal layer formed on the ceramic substrate 10.

  As the structure 3 used for such an anisotropic heat conducting element 1, highly oriented pyrolytic graphite is preferably selected. By using highly oriented pyrolytic graphite having higher thermal conductivity than ordinary graphite, the thermal conductivity efficiency can be dramatically increased. In particular, it is preferable to use highly oriented pyrolytic graphite having a thermal conductivity of 1500 W / mK or more. For example, the trade name PYROID HT manufactured by MINTEQ International Inc. in the United States can be used.

  Generally, there are two types of thermal conductivity: free electron and lattice vibration. Diamond's high thermal conductivity (1000 to 2000 W / mK) is via lattice vibration, and graphite thermal conductivity is It is generally anisotropic and is generally less than half that of diamond due to both free electrons and lattice vibrations.

However, PYROID HT has a density of 2.22 g / cc, a tensile strength of 28900 kPa (a direction), an elastic modulus of 50 GPa (a direction), a flexural modulus of 33200 MPa (a direction), and a thermal expansion integer of 0.6 × 10 ⁻⁶ / ° C. (A direction), 25 × 10 ⁻⁶ / ° C. (c direction), thermal conductivity 1700 W / mK (a direction), 7 W / mK (c direction), electrical resistivity 5.0 × 10 ⁻⁴ Ωcm (a direction) ), 0.6 Ωcm (c direction), oxidation start temperature 650 ° C. (a direction), permeability 10 ⁻⁶ mmHg, and thermal conductivity in the a direction is used as a general heat diffusion material. It is a material with extremely high thermal conductivity that exhibits a value about 4 times that of copper (Cu) and about 6 times that of aluminum nitride (AlN) or beryllium oxide (BeO). In addition, a direction shows the surface direction of a graphene sheet, and c direction shows a lamination direction.

  Since the density is close to the theoretical density of 2.3 g / cc of graphite and the elastic modulus is 50 GPa (a direction), it is easy to break when subjected to stress such as mechanical vibration, and processing is not easy. As described above, because it is supported by the support member 4 that covers the peripheral portion of the structure 3, mechanical stress at the time of processing, mechanical stress at the time of mounting to a heat source, mechanical vibration after mounting, The desired heat conduction performance can be maintained without breaking.

  As shown in FIG. 8, PYROID HT is manufactured by a CVD method. In the chamber 20 evacuated by the pump 21, the hydrocarbon gas supplied from the cylinder 22 as the raw material gas is thermally decomposed by being heated to 2000 ° C. or more by the heater 23, and the precipitated fine carbon nuclei C Are deposited and laminated in layers while crystallizing on the substrate 24.

  By managing the deposition and lamination time, a plate-like structure having a thickness of about 0.25 mm to 20 mm and a size of about 300 mm square can be obtained.

  The anisotropic heat conducting element 1 described above can be suitably used to dissipate heat generated by a heat source H such as an electronic device such as a semiconductor integrated circuit, a power semiconductor, or a semiconductor laser. An electronic device incorporating the anisotropic heat conducting element 1 can be utilized in many fields.

  In particular, when used in automobiles and the like that have been remarkably digitized in recent years, it can be sufficiently applied to applications requiring vibration resistance.

  The configuration example, specific size, material, and processing method of the anisotropic heat conductive element 1 described above are merely examples, and it is needless to say that modifications and design can be made as appropriate within the scope of the effects of the present invention. Absent.

1: Anisotropic heat conduction element 2: Graphene sheet 3: Structure 4: Support member 4a: Mounting portion H: Heat source

Claims (11)

An anisotropic heat conducting element that transfers heat from a heat source,
An anisotropic heat conduction element comprising: a structure in which graphene sheets are laminated along a surface intersecting with a contact surface with a heat source; and a support member that covers a peripheral portion of the structure.   The anisotropic heat conducting element according to claim 1, wherein a metal layer is formed on a contact surface with the heat source.   The anisotropic heat conductive element according to claim 1, wherein a ceramic layer is formed on a contact surface with the heat source.   The anisotropic thermal conduction element according to claim 1, wherein the structure is impregnated with a resin.   The anisotropic heat conducting element according to claim 1, wherein the structure is highly oriented pyrolytic graphite.   The anisotropic thermal conduction element according to claim 5, wherein the structure is highly oriented pyrolytic graphite having a thermal conductivity of 1500 W / mK or more.   The anisotropic heat conduction element according to claim 1, wherein a mounting portion to a heat source is provided on the support member.   An electronic device in which the anisotropic heat conducting element according to claim 1 is incorporated.   A covering step of covering the structure on which the graphene sheets are laminated with a support member, a cutting step of cutting along the plane intersecting the stacking direction of the graphene sheets after the covering step, and a surface treatment on the cut surface after the cutting step And a method of manufacturing an anisotropic heat conducting element including a surface treatment step.   The method for manufacturing an anisotropic thermal conduction element according to claim 9, further comprising an impregnation step of impregnating the structure with a resin before the covering step.   11. The anisotropic structure according to claim 9, wherein the covering step is configured to superimpose a plurality of structures along a stacking direction of the graphene sheets, and to cover the plurality of superposed structures integrally with a support member. Manufacturing method of heat conductive element.

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