Graphite composites and electronic components

Abstract

To provide a graphite composite including a graphite sheet and a resin material capable of easily increasing the heat conduction from the heating element to the radiator when it is interposed between the heating element and the radiator.SOLUTION: A graphite composite 1 includes a graphite sheet having voids inside, and a resin material. The voids are partially occupied by at least a portion of the total resin material. The ratio of resin material to the total of graphite sheet and resin material is 5% by mass or more. The ratio of the porosity of graphite composite is more than 50% and less than 95% by volume.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a graphite composite and an electronic component, and more particularly to a graphite composite including a graphite sheet and a resin material, and an electronic component including the graphite composite. [Background technology]

[0002] Patent Document 1 discloses that a thermally conductive sheet is produced by impregnating and filling the pores of a graphite sheet with a thermosoftening silicone resin that is substantially solid at room temperature, which prevents the graphite components from peeling off from the thermally conductive sheet and prevents graphite powder from scattering, and also provides a slight tackiness on the surface, which improves mountability and also provides excellent heat dissipation properties. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-076678 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the inventor's research, the thermal conductivity of a graphite sheet can be increased by filling the voids in the graphite sheet with a resin material, but when a graphite sheet is actually interposed between a heat-generating body such as a semiconductor component and a heat dissipating body such as a heat sink, the graphite sheet may not be able to sufficiently increase the thermal conduction from the heat-generating body to the heat dissipating body.

[0005] An object of the present disclosure is to provide a graphite composite comprising a graphite sheet and a resin material, which, when interposed between a heat generating element and a heat dissipating element, is likely to increase thermal conduction from the heat generating element to the heat dissipating element, and an electronic component comprising this graphite composite. [Means for solving the problem]

[0006] A graphite composite according to one embodiment of the present disclosure includes a graphite sheet having voids therein and a resin material. The voids are partially occupied by at least a portion of the resin material. The proportion of the resin material to the total of the graphite sheet and the resin material is 5% by mass or more. The porosity of the graphite composite is 50% by volume or more and 95% by volume or less.

[0007] An electronic component according to one aspect of the present disclosure includes a heat generating element, a heat dissipating element, and the graphite complex interposed between the heat generating element and the heat dissipating element. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, it is possible to provide a graphite composite including a graphite sheet and a resin material, which, when interposed between a heat generating element and a heat dissipating element, easily increases thermal conduction from the heat generating element to the heat dissipating element, and an electronic component including this graphite composite. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of an electronic component according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present disclosure will be described below. Note that the following embodiment is merely one of various embodiments of the present disclosure. The following embodiment can be modified in various ways depending on the design as long as the object of the present disclosure can be achieved.

[0011] Graphite composite 1 according to this embodiment includes a graphite sheet having voids therein and a resin material. The voids are partially occupied by at least a portion of the resin material. The proportion of the resin material to the total of the graphite sheet and the resin material is 5% by mass or more. The porosity of graphite composite 1 is 50% by volume or more and 95% by volume or less.

[0012] According to this embodiment, the voids in the graphite are partially occupied by at least a portion of the entire resin material, and the proportion of the resin material relative to the total of the graphite sheet and the resin material is 5 mass % or more. This reduces the thermal resistance of the graphite composite 1 due to the resin material in the voids, thereby increasing the thermal conductivity of the graphite composite 1. Furthermore, since the porosity of the graphite composite 1 is 50 volume % or more and 95 volume % or less, the graphite composite 1 is easily deformed when a compressive pressure is applied to the graphite composite 1. Therefore, when the graphite composite 1 is interposed between two components, the graphite composite 1 is easily deformed to follow the shape of each component. This tends to increase the contact area between the graphite composite 1 and each component. This tends to facilitate heat conduction between the components via the graphite composite 1.

[0013] The graphite composite 1 according to the present disclosure will be described in more detail.

[0014] A graphite sheet is a carbonaceous sheet containing graphite, and is produced by heating an organic polymer sheet such as a polyimide sheet.

[0015] A graphite sheet has multiple voids inside. In other words, the graphite sheet is porous. The porosity of the graphite sheet can be controlled, for example, by adjusting the heating conditions when heating an organic polymer sheet to produce graphite. A method for measuring the porosity of a graphite sheet will be explained in the Examples section below.

[0016] The porosity of the graphite sheet is preferably 80% by volume or more. In this case, it is easy to make the porosity of graphite composite 1 sufficiently large. The porosity of the graphite sheet is more preferably 85% by volume or more, and even more preferably 90% by volume or more. Furthermore, the porosity of the graphite sheet is preferably 98% by volume or less. In this case, it is easy to obtain good thermal conductivity of graphite composite 1. The porosity is more preferably 95% by volume or less.

[0017] The thickness of the graphite sheet is, for example, 20 μm or more and 400 μm or less, but is not limited to this.

[0018] The resin material may contain an appropriate organic polymer or silicone resin.

[0019] The resin material contains, for example, a cured product of a reactive curable compound, which contains, for example, at least one of an epoxy compound, an acrylic compound, and a silicone compound.

[0020] The resin material preferably contains a soft polymer, for example, a gel-like polymer, which makes graphite composite 1 more susceptible to deformation when a compressive pressure is applied to graphite composite 1, and also makes the resin material less susceptible to breakage even when graphite composite 1 is deformed.

[0021] When the reactive curable compound contains an epoxy compound, the epoxy compound may contain at least one selected from the group consisting of, for example, bisphenol A epoxy resins, bisphenol F epoxy resins, glycidylamine epoxy resins, cresol novolac epoxy resins, and naphthalene epoxy resins. When the reactive curable compound contains an epoxy compound, the reactive curable compound may further contain a curing agent. The curing agent may contain at least one selected from the group consisting of, for example, phenolic curing agents and dicyandiamide curing agents.

[0022] When the reactive curable compound contains a silicone compound, the silicone compound is, for example, a reactive curable liquid silicone rubber or silicone gel. The silicone compound may be a two-component or one-component type. The silicone compound contains, for example, a reactive organosilicon compound such as organopolysiloxane. When the reactive curable compound contains a silicone compound, the reactive curable compound may further contain a curing agent. The reactive curable compound may further contain a catalyst as needed. The curing agent contains, for example, at least one of organohydrogenpolysiloxane and organic peroxide. The catalyst is, for example, a platinum-based catalyst.

[0023] When the reactive curable compound contains an acrylic compound, the acrylic compound contains at least one selected from the group consisting of alkyl acrylates such as lauryl acrylate, phenoxydiethylene glycol acrylate, methoxypolyethylene glycol acrylate, and acrylic acid polymer esters.

[0024] The components contained in the reactive curable compound are not limited to those mentioned above.

[0025] An example of a method for producing the graphite composite 1 will be described. First, a graphite sheet and a reactive composition are prepared. The reactive composition contains only a reactive compound, or contains a solvent, an additive, and the like in addition to the reactive compound.

[0026] The graphite sheet is impregnated with the reactive composition. For example, the graphite sheet is coated with the reactive composition or immersed in the reactive composition. The reactive composition is then dried as needed, and the reactive compounds in the reactive composition are then reacted and cured. This produces a resin material, which is a cured product of the reactive composition, and a graphite composite 1 comprising the graphite sheet and the resin material is obtained.

[0027] As described above, the voids in the graphite sheet in graphite composite 1 are partially occupied by at least a portion of the entire resin material. That is, the multiple voids in the graphite include at least one of voids partially filled with resin material (voids having spaces inside that are not filled with resin material) and voids that are not filled with resin material at all. The multiple voids in the graphite may further include voids completely filled with resin material (voids that do not have spaces inside that are not filled with resin material).

[0028] The voids in the graphite in graphite composite 1 are partially occupied by at least a portion of the entire resin material, and thus graphite composite 1 has voids. For this reason, graphite composite 1 is prone to deformation when a compressive pressure is applied to graphite composite 1. A method for measuring the void ratio of a graphite sheet composite will be described in the Examples section below.

[0029] As described above, the porosity of the graphite composite 1 is 50% by volume or more and 95% by volume or less. When the porosity is 50% by volume or more, the graphite composite 1 is easily deformed. The porosity is more preferably 60% by volume or more, and even more preferably 70% by volume or more. Furthermore, when the porosity is 95% by volume or less, good thermal conductivity of the graphite composite 1 is easily obtained. The porosity is more preferably 90% by volume or less, and even more preferably 85% by volume or less.

[0030] As described above, the proportion of the resin material relative to the total weight of the graphite sheet and the resin material is 5% by mass or more. This proportion is more preferably 10% by mass or more, and even more preferably 40% by mass or more. In this case, the thermal conductivity of graphite composite 1 is likely to be further increased. It is also preferable that the proportion of the resin material relative to the total weight of the graphite sheet and the resin material is 85% by mass or less. In this case, the amount of resin material in the voids of the graphite sheet is unlikely to be excessively large, and therefore graphite composite 1 is more likely to deform when subjected to compressive pressure. This proportion is more preferably 75% by mass or less, and even more preferably 60% by mass or less. The amount of resin material is preferably adjusted so that the porosity of graphite composite 1 has a desired value.

[0031] The compression ratio of the graphite composite 1 when a pressure of 600 kPa is applied is preferably 70% or more. In this case, the graphite composite 1 is more likely to deform when a compressive pressure is applied to it. Therefore, heat transfer between components via the graphite composite 1 is more likely to be promoted. A compression ratio of 80% or more is more preferable. This compression ratio is, for example, 95% or less. The compression ratio is the percentage of the reduction in the thickness of the graphite composite 1 when a pressure of 600 kPa is applied in the thickness direction of the graphite composite 1, relative to the thickness of the graphite composite 1 when no pressure is applied. A method for measuring the compression ratio will be described in the Examples section below. In this case, the graphite composite 1 is more likely to deform when a compressive pressure is applied to it. Therefore, heat transfer between components via the graphite composite 1 is more likely to be promoted.

[0032] The voids in the graphite may be partially occupied by a portion of the entire resin material, and the surface of the graphite may be covered by another portion of the entire resin material. In this case, only a portion of the surface of the graphite may be covered with the resin material, or the entire surfaces of both sides of the graphite in the thickness direction may be covered with the resin material. In this case, when graphite composite 1 is interposed between two members, graphite composite 1 is more likely to adhere to each member, and gaps are less likely to occur between graphite composite 1 and each member. This makes it easier to promote heat conduction between the members via graphite composite 1.

[0033] The graphite composite 1 according to this embodiment is preferably used as a thermally conductive material (thermal interface material (TIM)). A thermally conductive material is a material that mediates the transfer of heat between two members by being interposed between the members. The above description of the graphite composite 1 is based mainly on the premise that the graphite composite 1 is used as a thermally conductive material. However, the use of the graphite composite 1 is not limited to only a thermally conductive material.

[0034] An electronic component 10 including a graphite composite 1 in the case where the graphite composite 1 is a thermally conductive material will be described with reference to FIG.

[0035] Electronic component 10 includes heat generating element 2, heat dissipating element 3, and graphite complex 1 according to the present embodiment. Graphite complex 1 is interposed between heat generating element 2 and heat dissipating element 3.

[0036] The heating element 2 is a member that generates heat, such as a semiconductor component. Examples of semiconductor components include, but are not limited to, a transistor, a CPU (central processing unit), an MPU (microprocessing unit), a driver IC, or a memory. The heating element 2 shown in FIG. 1 includes a heat spreader 22 and a chip portion 23 fixed on the heat spreader 22. The heat spreader 22 is a plate-shaped member made of metal or the like, and the chip portion 23 is, for example, a semiconductor package. The chip portion 23 is disposed on a portion of the heat spreader 22 excluding its outer edge, and a plurality of screw holes 21 that penetrate the heat spreader 22 are formed in the outer edge.

[0037] The heat dissipator 3 is a member to which heat generated by the heat generating element 2 is transferred. Heat can be dissipated from the heat dissipator 3. The heat dissipator 3 is, for example, a heat sink. The heat dissipator 3 shown in FIG. 1 is a plate-shaped heat sink, but the heat dissipator 3 may further include heat dissipation fins. The heat dissipator 3 has a plurality of screw holes 31 formed at positions corresponding to the plurality of screw holes 21 in the heat generating element 2 described above.

[0038] Furthermore, a plurality of screw holes 11 penetrating the graphite complex 1 are formed in the outer edge of the graphite complex 1 at positions corresponding to the plurality of screw holes 21 in the heating element 2 described above.

[0039] In this embodiment, the graphite composite 1 is in direct contact with both the heat generating element 2 and the heat dissipating element 3. Specifically, in this embodiment, the heat generating element 2, the graphite composite 1, and the heat dissipating element 3 are laminated such that the heat spreader 22 of the heat generating element 2 and the heat dissipating element 3 face each other and the graphite composite 1 is interposed between the heat generating element 2 and the heat dissipating element 3. This promotes heat transfer between the heat generating element 2 and the graphite composite 1, and between the heat dissipating element 3 and the graphite composite 1.

[0040] Of screw hole 21 in heating element 2, screw hole 11 in graphite composite 1, and screw hole 31 in heat dissipation element 3, at least screw hole 31 in heat dissipation element 3 has an internal thread formed on its inner surface. Each of screw hole 21 in heating element 2 and screw hole 11 in graphite composite 1 may or may not have an internal thread formed thereon.

[0041] Pressure is applied to the graphite composite 1 from the heating element 2 and the heat dissipation element 3. Specifically, in this embodiment, the screw hole 21 of the heating element 2, the screw hole 11 of the graphite composite 1, and the screw hole 31 of the heat dissipation element 3 are aligned. In this state, the screw 4 is passed through the screw holes 21, 11, and 31 in this order from the screw hole 21 of the heating element 2, and then the screw 4 is tightened. As a result, the heating element 2, the graphite composite 1, and the heat dissipation element 3 are fixed to each other, and the aforementioned pressure is applied to the graphite composite 1.

[0042] In this embodiment, when such pressure is applied to graphite composite 1, graphite composite 1 is likely to deform so as to reduce its thickness. At this time, even if the shapes of the surface of heat generating element 2 that contacts graphite composite 1 and the surface of heat dissipating element 3 that contacts graphite composite 1 do not match the shape of the surface of graphite composite 1, graphite composite 1 is likely to deform to follow the respective shapes of heat generating element 2 and heat dissipating element 3. Therefore, graphite composite 1 is likely to come into close contact with each of heat generating element 2 and heat dissipating element 3, which tends to promote heat conduction from heat generating element 2 to heat dissipating element 3 via graphite composite 1.

[0043] In this embodiment, the above-described pressure is applied to graphite composite 1 by using screws 4, but the method of applying pressure to graphite composite 1 is not limited to this. For example, pressure can be applied to graphite composite 1 interposed between heating element 2 and heat sink 3 by using a clamp to apply a load to heating element 2 and heat sink 3 in a direction that brings them closer to each other. [Example]

[0044] 1. Preparation of Thermally Conductive Materials The thermally conductive materials of each example and comparative example were prepared by the following method. A graphite sheet having the porosity and thickness shown in Table 1 and a two-component silicone gel (WACKER SilGel 612, manufactured by Wacker Asahi Kasei Silicones Co., Ltd.), which is a reactive curing compound, were prepared. The graphite sheet was impregnated with the silicone gel and left at 25°C for 24 hours to prepare a graphite composite, which is a thermally conductive material. The surface of the graphite composite was covered with a resin material, and the voids in the graphite composite were partially occupied by the resin material. However, in comparative example 1, the graphite sheet was used as the thermally conductive material as is.

[0045] The porosity of the graphite sheet was determined by the following method. A 30 mm square sheet was cut out from the graphite sheet and its weight was measured. The thickness of this sheet was also measured at five random points using a micrometer, and the volume of the sheet was calculated from the average value. The graphite sheet density ρ was calculated by dividing the sheet weight by the sheet volume. The graphite sheet porosity ε was calculated from this graphite sheet density ρ and the true specific gravity of graphite, 2.2, using the formula ε = 1 - (ρ / 2.2).

[0046] 2. Volume ratio of resin material in the voids to the voids in the graphite sheet In each of the graphite composites according to Examples 1 to 6 and Comparative Examples 2 and 3, the volume ratio of the resin material in the voids of the graphite sheet to the voids was measured by the following method. First, the density ρ' of the graphite composite was calculated in the same manner as in the case of the density ρ of the graphite sheet. 3 The weight W' of the resin material contained in the graphite composite was calculated using the formula W' = (ρ' - ρ) × 1. Next, the specific gravity of the resin was assumed to be 1.0, and the weight of 1 cm 3 The volume V' of the resin material contained therein was calculated using the formula V' = W' / 1.0. In addition, from the porosity ε of the graphite sheet, the volume of 1 cm of the graphite sheet was calculated. 3The volume V'' of the voids in the graphite sheet was calculated using the formula V'' = ε × 1. From this result, the volume ratio A of the resin material in the voids to the voids in the graphite sheet was calculated using the formula A = V' / V'' = (ρ' - ρ) / ε.

[0047] 3. Mass ratio of resin material to the total of graphite sheet and resin material In each of the graphite composites according to Examples 1 to 6 and Comparative Examples 2 and 3, the mass ratio B of the resin material to the total of the graphite sheet and the resin material was calculated based on the mass ratio B of 1 cm of the graphite composite. 3 It was calculated using the formula B=W' / (ρ'×1)=(ρ'-ρ) / ρ' from the weight W' of the resin material contained therein, the density ρ of the graphite sheet, and the density ρ' of the graphite composite.

[0048] 4.Porosity of graphite composites The porosity ε' of each of the graphite composites according to Examples 1 to 6 and Comparative Examples 2 and 3 was measured by measuring the porosity ε' of 1 cm of the graphite sheet. 3 Volume V'' of voids in 1 cm of graphite composite 3 It was calculated using the formula ε'=V''-V'=ε-(ρ'-ρ) where V' is the volume of the resin material contained, ε is the porosity of the graphite sheet, ρ is the density of the graphite sheet, and ρ' is the density of the graphite composite.

[0049] 5. Compression ratio The compressibility of each of the thermally conductive materials (graphite composites or graphite sheets) according to Examples 1 to 6 and Comparative Examples 1 to 3 was measured in accordance with ASTM D5470 when a compressive pressure of 600 kPa was applied in the thickness direction. The compressibility was calculated using the formula (1-T2 / T1) x 100 (%), where T1 is the initial thickness of the thermally conductive material and T2 is the thickness of the thermally conductive material when a compressive pressure of 600 kPa was applied.

[0050] 6.Thermal resistance The thermal resistance in the thickness direction of each of the thermally conductive materials (graphite complexes or graphite sheets) according to Examples 1 to 6 and Comparative Examples 1 to 3 was measured in accordance with ASTM D5470.

[0051] [Table 1]

[0052] As is clear from the above-described embodiments and examples, a graphite composite (1) according to one aspect of the present disclosure includes a graphite sheet having voids therein and a resin material. The voids are partially occupied by at least a portion of the resin material. The proportion of the resin material to the total of the graphite sheet and the resin material is 5% by mass or more. The porosity of the graphite composite (1) is 50% by volume or more and 95% by volume or less.

[0053] According to the first aspect, the resin material in the voids of the graphite sheet reduces the thermal resistance of the graphite composite (1), and the graphite composite (1) is easily deformed when a compressive pressure is applied to the graphite composite (1). Therefore, when the graphite composite (1) is interposed between two members, the thermal conduction between the members is likely to be increased.

[0054] In a second aspect of the present disclosure, in the first aspect, the porosity of the graphite sheet is 80% by volume or more.

[0055] According to the second embodiment, the graphite composite (1) is more likely to deform when a compressive pressure is applied to the graphite composite (1).

[0056] In a third aspect of the present disclosure, in the first or second aspect, the proportion of the resin material to the total of the graphite sheet and the resin material is 85 mass % or less.

[0057] According to the third aspect, the amount of resin material in the voids of the graphite sheet is unlikely to be excessively large, and therefore, when a compressive pressure is applied to graphite composite (1), graphite composite (1) is more likely to deform.

[0058] In a fourth aspect of the present disclosure, in any one of the first to third aspects, the graphite composite (1) has a compressibility of 70% or more when a pressure of 600 kPa is applied in a thickness direction of the graphite composite (1).

[0059] According to the fourth embodiment, the graphite composite (1) is more easily deformed when a compressive pressure is applied to the graphite composite (1).

[0060] In a fifth aspect of the present disclosure, in any one of the first to fourth aspects, the resin material contains a gel-like polymer.

[0061] According to the fifth aspect, when a compressive pressure is applied to the graphite composite (1), the graphite composite (1) is more easily deformed and less likely to break.

[0062] In a sixth aspect of the present disclosure, in any one of the first to fifth aspects, the graphite composite (1) is a thermally conductive material.

[0063] According to the sixth aspect, when the graphite composite (1) is interposed between two members, the thermal conduction between the members is likely to be increased.

[0064] An electronic component (10) according to a seventh aspect of the present disclosure includes a heat generating element (2), a heat dissipating element (3), and the graphite composite (1) according to any one of the first to sixth aspects interposed between the heat generating element (2) and the heat dissipating element (3).

[0065] According to the seventh aspect, the heat generated by the heat generating element (2) is easily and efficiently transferred to the heat radiating element (3) via the graphite composite (1).

[0066] In an eighth embodiment of the present disclosure, the graphite composite (1) in the seventh embodiment is in direct contact with each of the heat generating element (2) and the heat dissipating element (3).

[0067] In the eighth embodiment, the heat generated by the heating element (2) is more likely to be transmitted efficiently to the heat sink (3) via the graphite composite (1).

[0068] In a ninth aspect of the present disclosure, in the seventh or eighth aspect, pressure is applied to the graphite composite (1) from a heat generating element (2) and a heat dissipating element (3).

[0069] In the ninth embodiment, the heat generated by the heating element (2) is more likely to be transmitted efficiently to the heat sink (3) via the graphite composite (1).

[0070] In a tenth aspect of the present disclosure, in any one of the seventh to ninth aspects, the heat generating element (2) is a semiconductor component, and the heat dissipating element (3) is a heat sink.

[0071] In the tenth aspect, the heat generated by the semiconductor component is more likely to be transferred more efficiently to the heat sink via the graphite composite (1). [Explanation of symbols]

[0072] 1. Graphite composite 2 heating elements 3 Heat sink 10. Electronic Components

Claims

1. A graphite composite including a graphite sheet having voids therein and a resin material, the void is partially occupied by at least a portion of the resin material; a ratio of the resin material to the total of the graphite sheet and the resin material is 5 mass% or more; the porosity of the graphite composite is 50% by volume or more and 95% by volume or less; a compressibility of the graphite composite when a pressure of 600 kPa is applied in a thickness direction of the graphite composite is 70% or more; Graphite composite.

2. The porosity of the graphite sheet is 80% by volume or more. The graphite composite of claim 1 .

3. a ratio of the resin material to the total of the graphite sheet and the resin material is 85 mass% or less; The graphite composite according to claim 1 or 2.

4. The resin material contains a gel-like polymer. The graphite composite according to any one of claims 1 to 3.

5. A thermally conductive material.

5. The graphite composite according to claim 1.

6. A heat generating element, a heat dissipating element, and a graphite composite according to any one of claims 1 to 5 interposed between the heat generating element and the heat dissipating element. Electronic components.

7. The graphite composite is in direct contact with each of the heating element and the heat sink. The electronic component according to claim 6.

8. The graphite composite is subjected to pressure from the heating element and the heat dissipation element. The electronic component according to claim 6 or 7.

9. The heat generating element is a semiconductor component, and the heat dissipating element is a heat sink. The electronic component according to any one of claims 6 to 8.

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