JP7629728B2 - Thermally conductive sheet and manufacturing method thereof - Google Patents

Description

The present invention relates to a thermally conductive sheet and a method for manufacturing the same.

In order to efficiently release heat generated inside various devices and electronic equipment to the outside, a thermally conductive sheet may be placed between a heat generating body and a heat sink. In recent years, the temperature inside electronic equipment has risen due to the high density and miniaturization of electronic equipment, and as a result, sheets with higher heat resistance and thermal conductivity are required. Patent documents 1, 2 and 3 propose thermally conductive sheets that include a fluorine-containing elastomer having high heat resistance and a thermally conductive filler dispersed in the fluorine-containing elastomer.

JP 2004-140056 A JP 2014-61617 A JP 2015-67737 A

In general, it is preferable for a thermally conductive sheet to have high adhesion to the heat generating body and heat dissipating body and to be thin. In these cases, the heat flow rate between the heat generating body and heat dissipating body increases according to Fourier's law, and heat transferability also improves. However, it is difficult to mold a thermally conductive sheet that is uniformly thin and has a large area using the compositions described in Patent Documents 1, 2, and 3.

The present invention was made in consideration of the above problems, and aims to provide a thermally conductive sheet with a uniform thickness and a method for manufacturing the same.

According to the present invention, a thermally conductive sheet is provided that includes a resin sheet having voids, a fluorine-containing elastomer disposed at least inside the voids, and a thermally conductive material.

In the present invention, the fluorine-containing elastomer is held in the voids of the resin sheet and is integrated with the resin sheet. Therefore, despite containing the fluorine-containing elastomer, the obtained thermally conductive sheet has a uniform thickness. This enhances the adhesion between the thermally conductive sheet and the heating element and/or the heat dissipating element. As a result, the thermally conductive sheet according to the present invention exhibits excellent heat transfer in addition to thermal conductivity. Furthermore, a thin thermally conductive sheet can also be obtained.

Thermal conductivity refers to the phenomenon in which heat moves from a high temperature area to a low temperature area within an object. Thermal transfer refers to the phenomenon in which heat moves from a high temperature area to a low temperature area between two or more objects.

The thermally conductive material may include a particulate thermally conductive material. At least a portion of the particulate thermally conductive material may be supported on the resin sheet.

The resin sheet may contain a resin material with a heat resistance of 150°C or higher.

The resin sheet may be a fiber structure.

The thermally conductive material may include a fibrous carbon material.

The fluorine-containing elastomer may further be arranged to cover one of the main surfaces of the resin sheet, or may be arranged to cover both of the main surfaces.

The thickness of the thermally conductive sheet may be 0.05 mm or more and 1.0 mm or less.

The thermally conductive sheet is suitable for use in semiconductor manufacturing equipment.

The present invention also provides a method for producing a thermally conductive sheet, comprising the steps of preparing a resin sheet having voids, retaining a fluoroelastomer in the voids of the resin sheet, and press-molding the resin sheet retaining the fluoroelastomer, in which at least one of the resin sheet and the fluoroelastomer has a thermally conductive material.

In the present invention, a resin sheet having voids is used. Therefore, the fluorine-containing elastomer is held in the voids and integrated with the resin sheet. This results in a thermally conductive sheet with a uniform thickness.

In the step of preparing the resin sheet, a resin sheet carrying particulate thermally conductive material may be prepared.

The present invention provides a thermally conductive sheet with uniform thickness and a method for producing the same.

1 is a cross-sectional view showing a schematic diagram of a thermally conductive sheet according to one embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a thermally conductive sheet according to another embodiment of the present invention. 1 is an enlarged cross-sectional view showing a portion of a thermally conductive sheet according to one embodiment of the present invention. 1 is a flowchart showing a method for manufacturing a thermally conductive sheet according to an embodiment of the present invention.

Fluorine-containing elastomers have high heat resistance and are therefore suitable as materials for thermally conductive sheets. On the other hand, fluorine-containing elastomers have high melt viscosity and therefore do not spread easily even when molten. Therefore, it is difficult to mold fluorine-containing elastomers into sheets of uniform thickness. If the thickness of a thermally conductive sheet is not uniform, the adhesion between the thermally conductive sheet and the heating element and/or heat sink is likely to decrease, making it difficult to obtain excellent thermal conductivity.

Furthermore, the fluorine-containing elastomer is molded into a sheet and then vulcanized by heating. When cooled after heating, the sheet may shrink and deform (e.g., bend). The deformation of the sheet also reduces the adhesion between the sheet and the heating element and/or heat sink.

The heat flow rate Q, which is an index of heat transferability, is expressed by the following formula according to Fourier's law: The larger the heat flow rate Q, the better the heat transferability.
Q = k × A × ΔT / d
(In the formula, k is the thermal conductivity of the thermal conductive sheet (W/m·K), A is the contact area of the thermal conductive sheet (m ² ), ΔT is the temperature difference (K), and d is the thickness of the thermal conductive sheet (m).)

As can be seen from the above formula, heat transfer is greatly affected by the contact area between the thermally conductive sheet and the heat generating body and/or heat dissipating body, i.e., the adhesion between the two. The higher the adhesion of the thermally conductive sheet, the better the heat transfer. Furthermore, the smaller the thickness d of the thermally conductive sheet, the better the heat transfer.

In this embodiment, a resin sheet having voids is used together with the fluorine-containing elastomer. By disposing the fluorine-containing elastomer in the voids of the resin sheet, the fluorine-containing elastomer is integrated with the resin sheet. As a result, the thickness of the thermally conductive sheet becomes uniform. A thermally conductive sheet of uniform thickness has excellent adhesion to the heating element and/or heat dissipation element, and therefore has excellent thermal conductivity.

The standard deviation of the thickness at any five points of the thermally conductive sheet according to this embodiment can be, for example, 0.020 or less. The standard deviation is preferably 0.015 or less. The any five points are set to be spaced 3 cm or more apart from each other. The thickness of the thermally conductive sheet can be measured with a digital dial gauge (e.g., Digimatic Indicator, manufactured by Mitutoyo Corporation). The thickness of the resin sheet can also be measured in the same manner.

Since the fluorine-containing elastomer is integrated with the resin sheet, it is possible to obtain thermally conductive sheets of various thicknesses depending on the thickness of the resin sheet. For example, it is possible to obtain a thin thermally conductive sheet of 0.3 mm or less. According to Fourier's law, the thinner the thermally conductive sheet, the better the thermal transfer. Furthermore, it is possible to obtain a thermally conductive sheet with a large area. The larger the area of the thermally conductive sheet, the larger the contact area with the heating element and/or heat dissipation element can be. According to this embodiment, it is possible to obtain a thin, large, and more uniform thermally conductive sheet, for example, 500 mm square and about 0.1 mm thick.

The resin sheet also regulates the shape of the thermally conductive sheet. This prevents deformation of the thermally conductive sheet. In addition, the resin sheet makes it easier to prevent thermal expansion of the thermally conductive sheet. Furthermore, the resin sheet also improves the durability of the thermally conductive sheet.

[Thermal conductive sheet]
The thermally conductive sheet according to this embodiment includes a resin sheet having voids, a fluorine-containing elastomer disposed at least inside the voids, and a thermally conductive material.

The thermal conductivity of the thermally conductive sheet is not particularly limited and may be set appropriately depending on the application. The thermal conductivity of the thermally conductive sheet may be, for example, 0.15 W/m·K or more, preferably 0.20 W/m·K or more, and more preferably 0.25 W/m·K or more. The thermal conductivity of the thermally conductive sheet can be calculated by multiplying the thermal diffusivity, the specific heat, and the density. The thermal diffusivity of the thermally conductive sheet is measured, for example, by the laser flash method. The specific heat of the thermally conductive sheet is determined, for example, by differential scanning calorimetry (DSC). The density of the thermally conductive sheet is determined, for example, by the Archimedes method.

The temperature at which the mass of the thermally conductive sheet changes by 1%, measured according to JIS K 7120 Thermogravimetry (TG) method (hereinafter sometimes referred to as the heat resistance temperature in the TG method), is preferably 300°C or higher, and more preferably 400°C or higher. This makes it easier to prevent a decrease in thermal conductivity even when various devices equipped with the thermally conductive sheet are used continuously for long periods of time.

The thickness of the thermally conductive sheet is not particularly limited and is set appropriately depending on the application, etc. The thickness of the thermally conductive sheet may be, for example, 1.0 mm or less, or 0.5 mm or less. The thickness of the thermally conductive sheet may be, for example, 0.05 mm or more, or 0.1 mm or more. The thickness of the thermally conductive sheet is preferably 0.05 mm or more and 1.0 mm or less. The thickness of the thermally conductive sheet is the average value of the thicknesses at any five points on the sample. It is desirable that the any five points are spaced apart by 3 cm or more.

The size of the thermally conductive sheet is not particularly limited and is set appropriately depending on the application, etc. The short axis or diameter of the thermally conductive sheet may be 100 mm or more.

The lower the surface hardness of the thermally conductive sheet, the easier it is to improve the adhesion of the thermally conductive sheet. The higher the adhesion, the easier it is to improve the thermal transferability of the thermally conductive sheet. The Martens hardness of the surface of the thermally conductive sheet measured by the nanoindentation method in accordance with ISO 14577 is preferably 0.1 MPa or more and 20 MPa or less. The Martens hardness of the surface is measured by pressing an indenter into the surface of the thermally conductive sheet with a load of 10 mN.

The electrical conductivity of the thermally conductive sheet is not particularly limited and is appropriately set according to the application, etc. The electrical conductivity of the conductive thermally conductive sheet at 20°C may be, for example, 1.00 x ^10-6 S/m or more, preferably 1.00 x ^10-3 S/m or more, and more preferably 1.00 x ^10-1 S/m or more. When the electrical conductivity is less than 1.00 x ^10-4 S/m, it is measured according to JIS K 6911, and when the electrical conductivity is 1.00 x ^10-4 S/m or more, it is calculated from the electrical resistivity measured according to JIS K 7194.

The thermally conductive sheet may have voids. The voids in the thermally conductive sheet originate from the voids in the resin sheet and/or the pores in the fluorine-containing elastomer. However, from the viewpoint of sealing properties and thermal conductivity, it is desirable for the porosity of the thermally conductive sheet to be small.

Multiple thermally conductive sheets may be stacked and used as a thermally conductive sheet. The multiple thermally conductive sheets may have the same configuration or different configurations. For example, a conductive thermally conductive sheet and an insulating thermally conductive sheet may be stacked.

The thermally conductive sheet according to this embodiment has excellent thermal conductivity and heat resistance, and can therefore be used in various devices and electronic devices that can become hot. In particular, the thin and large thermally conductive sheet is suitable for semiconductor manufacturing equipment. Examples of semiconductor manufacturing equipment include dicers that separate substrates, wafer etching equipment, wafer cleaning equipment, and wafer drying equipment. Specifically, the thermally conductive sheet is suitably placed between a heat source and a heat sink, such as an electrostatic chuck that adsorbs and holds a substrate by electrostatic force.

(Resin sheet)
The resin sheet has a plurality of voids (pores). The plurality of voids may be continuous or may be independent of each other. It is preferable that the plurality of voids are continuous in order to easily retain the fluorine-containing elastomer.

One or more resin sheets are placed on the thermally conductive sheet. The multiple resin sheets may be of the same type or different types.

The porosity of the resin sheet is not particularly limited. In order that the thermally conductive sheet can retain a sufficient amount of fluorine-containing elastomer, the porosity of the resin sheet may be, for example, 30% or more, and preferably 40% or more. The porosity of the resin sheet may be, for example, 95% or less, and preferably 90% or less.

The porosity of the resin sheet can be calculated by the following formula.
Porosity (%)=100(%)×{1−mass of resin sheet G (g)/(apparent volume of resin sheet V (cm ³ )×density of material constituting resin sheet ρ (g/cm ³ ))}

The thickness of the resin sheet is not particularly limited and is set appropriately depending on the application, etc. The thickness of the resin sheet may be, for example, 1.0 mm or less, or 0.5 mm or less. From the viewpoint of strength, the thickness of the resin sheet is preferably 0.05 mm or more, and more preferably 0.1 mm or more.

Examples of resin sheets include porous bodies, foams, and fiber structures formed from materials containing resin. Porous bodies can be obtained by a phase separation method, a stretching method, an etching method, or the like. Among these, fiber structures are preferred because the porosity can be relatively easily controlled. In addition, various surface treatments (e.g., conductive treatment, antistatic treatment, etc.) can be easily applied to the fiber structures. Examples of fiber structures include nonwoven fabrics, woven fabrics, and knitted fabrics. Among these, nonwoven fabrics are preferred.

The mass per unit area of the fiber structure is not particularly limited. The mass per unit area of the fiber structure may be, for example, 20 g/m2 or ^more and 600 g/m2 ^or less. The thickness of the fibers constituting the fiber structure is not particularly limited. The diameter of the cross section along the circumferential direction of the fibers constituting the fiber structure may be, for example, 10 μm or more and 200 μm or less.

The resin sheet material contains a resin and, if necessary, various additives. The resin sheet material may further contain a thermally conductive material. The resin may be 50% by mass or more, 70% by mass or more, or 80% by mass or more of the resin sheet material.

From the viewpoint of heat resistance, the resin sheet preferably contains a resin material with a heat resistance temperature of 150°C or higher. Such resin materials are known as so-called super engineering plastics. The heat resistance temperature of the resin material is preferably 200°C or higher. The heat resistance temperature is a value measured, for example, in accordance with the UL746B standard. In the UL746B standard, the heat resistance temperature is the temperature at which the initial physical property values are reduced by half when exposed to the atmosphere at a constant temperature for 100,000 hours.

Examples of super engineering plastics include fluororesin, polyphenylene sulfide (PPS), polysulfone, polyethersulfone, amorphous polyarylate, polyetheretherketone, polyimide, polyetherimide and liquid crystal polymer. Among these, fluororesin is preferred because of its excellent heat resistance and radical resistance.

Fluorine resins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), perfluoroethylene-propene copolymer (FEP), polyvinylidene fluoride (PVDF), and ethylene-tetrafluoroethylene copolymer (ETFE). Of these, fully fluorinated perfluoro resins such as PTFE, PFA, and FEP are preferred. Perfluoro resins are particularly excellent in heat resistance. By using perfluoro resins, it is easy to obtain a thermally conductive sheet that can be used at high temperatures, for example, above 200°C, and even above 300°C.

(Fluorine-containing elastomer)
The fluorine-containing elastomer contributes to the heat resistance of the thermally conductive sheet. Regarding the heat resistance of the fluorine-containing elastomer, in a compression set test carried out in accordance with JIS K 6262, the temperature at which the compression set of the fluorine-containing elastomer reaches 80% (hereinafter, sometimes referred to as the heat resistance temperature in the compression set test) is preferably 250°C or higher, more preferably 280°C or higher. Regarding the heat resistance of the fluorine-containing elastomer, in a thermogravimetric measurement method (TG method) measured in accordance with JIS K 7120, the temperature at which the weight of the fluorine-containing elastomer changes by 1% (hereinafter, sometimes referred to as the heat resistance temperature in the TG method) is preferably 380°C or higher, more preferably 400°C or higher. This makes it possible to easily obtain a thermally conductive sheet that can be used even at high temperatures, for example, 200°C or higher, or even 300°C or higher.

The fluorine-containing elastomer is disposed at least inside the voids of the resin sheet. The fluorine-containing elastomer may be disposed so as to fill at least a portion of the voids, and may fill all of the voids.

The fluorine-containing elastomer may be disposed so as to cover at least a portion of at least one of the main surfaces of the resin sheet, in addition to being disposed inside the voids of the resin sheet. This makes the hardness of the main surface of the thermally conductive sheet equivalent to that of the flexible fluorine-containing elastomer and lower than the hardness of the interior of the thermally conductive sheet, which makes it easier to improve adhesion.

In particular, the fluorine-containing elastomer is preferably arranged so as to cover the entirety of one of the main surfaces of the resin sheet. In other words, it is preferable that an elastomer region that contains the fluorine-containing elastomer but does not contain the resin sheet is arranged on one of the main surfaces of the thermally conductive sheet. In this case, the resin sheet is not exposed from one of the main surfaces of the thermally conductive sheet.

In the above case, the resin sheet may be exposed from the other main surface of the thermally conductive sheet. Alternatively, the other main surface may be covered with a fluorine-containing elastomer to such an extent that the resin sheet is exposed from the other main surface of the thermally conductive sheet during use. This prevents the fluorine-containing elastomer from softening and adhering to the heating element and/or heat sink during use in a high-temperature environment. This improves the peelability of the thermally conductive sheet, making it possible to remove the thermally conductive sheet smoothly while suppressing the generation of residues. In particular, in the semiconductor field, it is important not to make semiconductor manufacturing equipment a source of contamination of semiconductors. Therefore, a thermally conductive sheet that is less likely to generate residues is suitable for use in semiconductor manufacturing equipment.

The elastomer regions may be disposed on both main surfaces of the thermally conductive sheet. In this case, the hardness of both main surfaces of the thermally conductive sheet becomes equivalent to that of the flexible fluorine-containing elastomer and is lower than the hardness of the interior of the thermally conductive sheet. This improves the adhesion between the thermally conductive sheet and both the heating element and the heat sink, and is expected to further improve thermal transfer.

The thickness of the elastomer region is not particularly limited, and may be such that the resin sheet is not exposed from the main surface side on which the elastomer region is disposed, or such that the resin sheet is not exposed from the other main surface side of the thermally conductive sheet during use. The thickness of the elastomer region may be, for example, about 1/20 to 3/4 of the total thickness of the thermally conductive sheet, and preferably 1/10 to 1/2. Specifically, the thickness of the elastomer region may be 10 μm to 200 μm, and preferably 20 μm to 150 μm. The thicknesses of the elastomer regions disposed on both main surfaces of the thermally conductive sheet may be the same or different.

When an area is formed on at least one of the main surfaces of the thermally conductive sheet, the area has a constant thickness of 10 μm or more, contains a fluorine-containing elastomer, but does not contain a resin sheet, the fluorine-containing elastomer may be considered to be arranged so as to cover at least one of the main surfaces of the resin sheet.

The thickness of the elastomer region is determined from a cross section of the thermally conductive sheet in the thickness direction. First, draw a straight line through any point on the cross section, along the thickness direction of the thermally conductive sheet. Of these straight lines, measure the length of the shortest line segment from the resin sheet to the main surface of the thermally conductive sheet. The length of this line segment is the thickness of the elastomer region.

The elastomer region preferably further contains a thermally conductive material, which further improves thermal conductivity.

In the thermally conductive sheet, the fluorine-containing elastomer may or may not be crosslinked. From the viewpoint of mechanical strength, it is preferable that the fluorine-containing elastomer is crosslinked in the thermally conductive sheet. The fluorine-containing elastomer may have internal pores.

The amount of fluorine-containing elastomer is not particularly limited. The proportion of fluorine-containing elastomer in the thermally conductive sheet may be 20% by mass or more, and preferably 40% by mass or more. The proportion of fluorine-containing elastomer may be 80% by mass or less, and preferably 60% by mass or less.

The fluorine-containing elastomer is not particularly limited. Examples of the fluorine-containing elastomer include the fluorine-containing elastomers described in Japanese Patent No. 6463474.

The fluorine-containing elastomer may be a partially fluorinated elastomer or a perfluoroelastomer. Among them, perfluoroelastomers are preferred from the viewpoint of heat resistance. The perfluoroelastomer may further contain a cyano group (-CN).

Examples of partially fluorinated elastomers include vinylidene fluoride (VdF)-based fluororubber, tetrafluoroethylene (TFE)/propylene (Pr)-based fluororubber, tetrafluoroethylene (TFE)/propylene/vinylidene fluoride (VdF)-based fluororubber, ethylene/hexafluoropropylene (HFP)-based fluororubber, ethylene/hexafluoropropylene (HFP)/vinylidene fluoride (VdF)-based fluororubber, and ethylene/hexafluoropropylene (HFP)/tetrafluoroethylene (TFE)-based fluororubber.

An example of a perfluoroelastomer is a perfluoroelastomer that contains tetrafluoroethylene (TFE) as a raw material monomer.

(Thermal Conductive Materials)
The thermally conductive material provides thermal conductivity to the thermally conductive sheet. The thermal conductivity of the thermally conductive material is not particularly limited. The thermal conductivity of the thermally conductive material may be such that the thermal conductivity of the thermally conductive sheet is, for example, 0.15 W/m·K or more. In terms of heat dissipation, the thermal conductivity of the thermally conductive material is preferably 10 W/m·K or more, more preferably 50 W/m·K or more.

The content of the thermally conductive material is not particularly limited. From the viewpoint of thermal conductivity, the total amount of the thermally conductive material may be 0.1 mass% or more of the thermally conductive sheet, and preferably 1 mass% or more. From the viewpoint of adhesion, the total amount of the thermally conductive material may be 50 mass% or less of the thermally conductive sheet, and preferably 30 mass% or less.

The form of the thermally conductive material is not particularly limited. For example, the thermally conductive material may be a coating that at least partially (preferably entirely) covers the surface of the resin sheet, or may be particulate. In particular, it is preferable that the thermally conductive material contains a particulate thermally conductive material (hereinafter referred to as a thermally conductive filler) in that the increase in hardness of the thermally conductive sheet is easily suppressed.

The thermally conductive filler may be supported on a resin sheet. Since the resin sheet is the skeleton of the thermally conductive sheet, supporting the thermally conductive filler on it makes it easier to form a heat transfer path with a small amount of filler. As mentioned above, it is important not to make the semiconductor manufacturing equipment a source of contamination of the semiconductors. Therefore, a thermally conductive sheet that uses a reduced amount of thermally conductive material is suitable for use in semiconductor manufacturing equipment. The thermally conductive filler may be dispersed in a fluorine-containing elastomer. In this case, a large amount of thermally conductive filler can be dispersed, making it easier to improve thermal conductivity.

The manner in which the thermally conductive filler is supported on the resin sheet is not particularly limited. The thermally conductive material may be added externally or internally to the resin sheet. More specifically, the thermally conductive filler may be attached to the surface of the material (typically a resin material) forming the resin sheet, or the thermally conductive filler may be contained inside the material forming the resin sheet, or both. By adding the thermally conductive filler to the material forming the resin sheet and then forming it into a resin sheet, the thermally conductive filler can be contained inside the material. In particular, it is preferable that the thermally conductive filler is attached to the surface of the material forming the resin sheet. This makes it easier for the thermal conductivity and electrical conductivity of the thermally conductive sheet to be high.

The thermally conductive filler may be supported on the resin sheet and dispersed in the fluorine-containing elastomer. In this case, the thermal conductivity can be improved while suppressing the total amount of thermally conductive filler.

The material of the thermally conductive filler is not particularly limited. Examples of materials for the thermally conductive filler include metals, ceramics, and carbon materials. The thermally conductive filler is appropriately selected depending on the application, etc. When both thermal conductivity and electrical conductivity are required, for example, a thermally conductive filler made of a metal and/or an electrically conductive carbon material is selected. When both thermal conductivity and electrical insulation are required, for example, a thermally conductive filler made of a ceramic is selected.

Examples of metals include silver, copper, aluminum, nickel, iron, and alloys thereof. Examples of ceramics include oxides, carbides, nitrides, and borides of metal elements, semimetal elements, and nonmetal elements. Specific examples of ceramics include crystalline silica, silicon carbide, boron nitride, silicon nitride, aluminum nitride, aluminum oxide, magnesium oxide, zinc oxide, titanium carbide, and titanium oxide. Examples of conductive carbon materials include carbon fiber, carbon nanotube, carbon nanofiber, carbon nanocoil, carbon nanotwist, carbon nanohorn, fullerene, graphene, diamond, graphite, and carbon black. Thermally conductive fillers are used alone or in combination of two or more types.

The individual shapes of the thermally conductive fillers are not particularly limited, so long as they are "particulate" as a whole. In the present invention, "particulate" refers to an aggregate of multiple solids (interpreted as "particles"), and the individual particles may be in contact with each other or separated from each other.

The thermally conductive filler may be, for example, spherical, fibrous, or scaly. Among these, fibrous thermally conductive fillers are preferred. A small amount of fibrous thermally conductive filler also easily improves thermal conductivity. A small amount of thermally conductive filler makes it easier to prevent the filler from falling off the thermally conductive sheet. For this reason, fibrous thermally conductive fillers are particularly suitable for semiconductor manufacturing equipment. Spherical thermally conductive fillers are preferred because they are easily dispersed in the fluorine-containing elastomer. Spherical thermally conductive fillers have an aspect ratio of 1 or more and less than 2. Fibrous or scaly thermally conductive fillers have an aspect ratio of, for example, 2 or more, preferably 30 or more.

The average length of the fibrous thermally conductive filler is not particularly limited. The length of the fibrous thermally conductive filler may be, for example, 1 μm or more and 1000 μm or less, preferably 5 μm or more and 600 μm or less, and more preferably 50 μm or more and 600 μm or less. The diameter of the fibrous thermally conductive filler is not particularly limited. The diameter of the cross section along the circumferential direction of the fibrous thermally conductive filler may be, for example, 2 nm or more and 150 nm or less, and preferably 5 nm or more and 80 nm or less. The length and diameter of the fibrous thermally conductive filler are the average values of 20 samples measured by a scanning electron microscope (SEM or FE-SEM) or a transmission electron microscope (TEM).

As the fibrous thermally conductive filler, a fibrous carbon material is preferred. Examples of fibrous carbon materials include carbon fiber, carbon nanotube, carbon nanofiber, carbon nanocoil, carbon nanotwist, and carbon nanohorn.

Among these, carbon nanotubes (CNTs) are preferred. CNTs may be single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs) or multi-walled carbon nanotubes (MWNTs).

CNTs can be produced by conventional manufacturing methods. Examples of manufacturing methods include gas phase growth methods such as catalytic hydrogen reduction of carbon dioxide, arc discharge, laser evaporation, and CVD; gas phase flow methods; the HiPco method, in which carbon monoxide is reacted with an iron catalyst at high temperature and pressure to grow CNTs in the gas phase; and the oil furnace method.

The average particle size of the spherical thermally conductive filler is not particularly limited. The average particle size of the spherical thermally conductive filler may be, for example, 10 nm or more and 1000 nm or less, and preferably 20 nm or more and 300 nm or less. The average particle size is the 50% average particle size (D50) in the volume-based particle size distribution measured using a laser diffraction/scattering particle size distribution measuring device.

Carbon black is preferred as a spherical thermally conductive filler. Examples of carbon black include furnace black, acetylene black, and ketjen black.

The amount of thermally conductive filler supported on the resin sheet may be 0.01% by mass or more of the resin sheet, preferably 0.5% by mass or more, and more preferably 1% by mass or more. The amount of thermally conductive filler supported on the resin sheet may be 50% by mass or less of the resin sheet, preferably 30% by mass or less, and more preferably 10% by mass or less.

The amount of the thermally conductive filler dispersed in the fluorine-containing elastomer may be, for example, 1 part by mass or more, preferably 2 parts by mass or more, and more preferably 10 parts by mass or more, per 100 parts by mass of the fluorine-containing elastomer. The amount of the thermally conductive filler dispersed in the fluorine-containing elastomer may be 150 parts by mass or less, preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the fluorine-containing elastomer.

Figure 1 is a cross-sectional view showing a thermally conductive sheet according to one embodiment. Figure 2 is a cross-sectional view showing a thermally conductive sheet according to another embodiment. Figure 3 is a cross-sectional view showing an enlarged portion of a thermally conductive sheet according to one embodiment.

The thermally conductive sheets 10A and 10B each include a resin sheet 11 having voids, a fluorine-containing elastomer 12 disposed inside the voids, and a thermally conductive material (thermally conductive filler in the illustrated embodiment) 13. The resin sheet 11 is a nonwoven fabric composed of a plurality of fibers 111. The thermally conductive material (thermally conductive filler) 13 includes carbon nanotubes 131 and carbon black 132. The carbon nanotubes 131 are supported by the fibers 111. The carbon black 132 is dispersed in the fluorine-containing elastomer 12.

An elastomer region 10a is disposed on one of the main surfaces 10X of the thermally conductive sheet 10A in FIG. 1. The elastomer region 10a includes a fluorine-containing elastomer 12 disposed to cover the main surface 10X of the resin sheet 11, but does not include the resin sheet 11. The elastomer region 10a may include a thermally conductive material. The thickness tx of the elastomer region 10a is, for example, about 1/5 of the thickness of the entire thermally conductive sheet.

The thermally conductive sheet 10B in FIG. 2 has the same configuration as the thermally conductive sheet 10A, except that elastomer regions 10a are arranged on both main surfaces 10X and 10Y. The thicknesses tx and ty of each elastomer region 10a are, for example, approximately 1/6 of the thickness of the entire thermally conductive sheet. The thicknesses tx and ty may be approximately the same or different.

[Method of manufacturing thermally conductive sheet]
The thermally conductive sheet according to this embodiment is manufactured, for example, by a method including a step of preparing a resin sheet having voids (preparation step), a step of retaining a fluorine-containing elastomer in the voids of the resin sheet (retention step), and a step of press-molding the resin sheet retaining the fluorine-containing elastomer (pressing step).

In the preparation step, a resin sheet carrying a thermally conductive filler may be prepared. In the holding step, a fluorine-containing elastomer in which a thermally conductive filler is dispersed may be used.

An example of a method for manufacturing a thermally conductive sheet is described below. Figure 4 is a flowchart showing the method for manufacturing a thermally conductive sheet according to this embodiment.

(1) Preparation process (S11)
A resin sheet having voids is prepared. The details of the resin sheet are as described above.

To improve the adhesion between the resin sheet and the thermally conductive filler and/or the fluorine-containing elastomer, the resin sheet may be subjected to a silane coupling treatment or a plasma treatment. A thermally conductive material may be added to the inside of the resin sheet.

The method for supporting the thermally conductive filler on the resin sheet is not particularly limited, and can be achieved, for example, by coating the resin sheet with a dispersion liquid in which the thermally conductive filler is dispersed, or by immersing the resin sheet in a dispersion liquid in which the thermally conductive filler is dispersed. Immersion in the dispersion liquid may be performed multiple times. Coating of the dispersion liquid may be performed on one side of the resin sheet, or may be performed on both sides. The resin sheet is then dried. The drying method is not particularly limited, and may be heat drying, vacuum drying, or the like.

The following describes the loading process in detail, taking as an example a method for loading carbon nanotubes onto the surface of a resin sheet, but the loading process according to this embodiment is not limited to this.

First, carbon nanotubes are dispersed in a solvent to prepare a carbon nanotube dispersion liquid. The solvent is not particularly limited. Examples of the solvent include water; alcohol-based solvents such as ethanol, n-butyl alcohol, isopropyl alcohol, and ethylene glycol; ester-based solvents such as ethyl acetate; ether-based solvents such as diethyl ether and dimethyl ether; ketone-based solvents such as methyl ethyl ketone, acetone, diethyl ketone, methyl propyl ketone, and cyclohexanone; aliphatic hydrocarbon-based solvents such as hexane and heptane; aromatic hydrocarbon-based solvents such as toluene and benzene; and chlorinated hydrocarbon-based solvents such as dichloromethane, chloroform, and chlorobenzene. These may be used alone or in combination of two or more. Among these, ketone-based solvents are preferred.

The amount of the solvent is not particularly limited. In order to make it easier to uniformly disperse the carbon nanotubes in the solvent, the amount of the solvent is preferably 20,000 parts by mass or more and 1,000,000 parts by mass or less, more preferably 30,000 parts by mass or more and 300,000 parts by mass or less, and particularly preferably 50,000 parts by mass or more and 200,000 parts by mass or less, per 100 parts by mass of the carbon nanotubes.

A dispersant may be added to the carbon nanotube dispersion. The dispersant is not particularly limited. Examples of dispersants include acrylic dispersants, synthetic polymers such as polyvinylpyrrolidone and polyaniline sulfonic acid, DNA, peptides, and organic amine compounds. These are used alone or in combination of two or more. The amount of dispersant added is appropriately set depending on the type and amount of carbon nanotubes, solvent, and dispersant. The amount of dispersant added is, for example, preferably 100 parts by mass or more and 6,000 parts by mass or less, more preferably 200 parts by mass or more and 3,000 parts by mass or less, and particularly preferably 300 parts by mass or more and 1,000 parts by mass or less, relative to 100 parts by mass of carbon nanotubes.

Next, the resin sheet is immersed in the carbon nanotube dispersion liquid. The resin sheet is then dried, so that the carbon nanotubes are supported on the resin sheet. There are no particular limitations on the drying conditions, and they are set appropriately depending on the type and amount of carbon nanotubes and solvent.

(2) Holding step (S12)
The fluorine-containing elastomer is held in the voids of the resin sheet. This integrates the resin sheet and the fluorine-containing elastomer. All of the voids in the resin sheet may be filled with the fluorine-containing elastomer, or only a part of the voids in the resin sheet may be filled with the fluorine-containing elastomer.

(2a) Preparation of elastomer composition First, an elastomer composition containing a fluorine-containing elastomer is prepared. The elastomer composition is prepared, for example, by mixing a fluorine-containing elastomer, a crosslinking agent, other additives, and a solvent. The elastomer composition may be prepared by sequentially adding components such as a fluorine-containing elastomer to a solvent and mixing them, or by mixing components other than the solvent and then mixing the resulting mixture with the solvent. The elastomer composition may also be prepared by mixing a commercially available compound containing a fluorine-containing elastomer, a crosslinking agent, and other additives with a solvent. The mixing is performed, for example, using a known kneader, kneading roll, or mixer. In the elastomer composition, the fluorine-containing elastomer may be dissolved, dispersed, or suspended in the solvent.

The solvent is not particularly limited, and is appropriately selected depending on the type of fluorine-containing elastomer and the properties of the elastomer composition. Examples of the solvent include aliphatic, aromatic, alcohol, ester, ether, and halogen-based organic solvents. These may be used alone or in combination of two or more. The amount of solvent added is not particularly limited, and is appropriately set depending on the method of retention, the properties and viscosity of the elastomer composition, etc.

The viscosity of the elastomer composition is not particularly limited and is set appropriately depending on the method of holding, the thickness of the resin sheet, etc. The viscosity of the elastomer composition measured with a B-type viscometer at 20°C may be, for example, 50 mPa·s or more and about 50,000 mPa·s.

The crosslinking agent is not particularly limited and is appropriately selected depending on the composition of the fluorine-containing elastomer. Examples of crosslinking agents include polyamine compounds such as hexamethylenediamine carbamate and N,N'-dicinnamylidene-1,6-hexamethylenediamine, polyhydroxy compounds such as 2,2-bis(4-hydroxyphenyl)propane and 2,2-bis(4-hydroxyphenyl)perfluoropropane, and organic peroxides such as 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane and 2,5-dimethylhexane-2,5-dihydroperoxide.

The amount of the crosslinking agent is not particularly limited. For example, the amount of the crosslinking agent may be 0.01 parts by mass or more and 10 parts by mass or less, and preferably 0.1 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the fluorine-containing elastomer.

The elastomer composition may contain a crosslinking accelerator as necessary. The crosslinking accelerator is not particularly limited. Examples of the crosslinking accelerator include onium compounds. Examples of the onium compounds include ammonium compounds such as quaternary ammonium salts, phosphonium compounds such as quaternary phosphonium salts, oxonium compounds, sulfonium compounds, cyclic amines, and monofunctional amine compounds.

The amount of the crosslinking accelerator is not particularly limited. For example, the amount of the crosslinking accelerator may be 0.01 parts by mass or more and 8 parts by mass or less, and preferably 0.02 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the fluorine-containing elastomer.

The elastomer composition may contain a crosslinking aid as necessary. The crosslinking aid is not particularly limited. Examples of the crosslinking aid include triallyl cyanurate, trimethallyl isocyanurate, triallyl isocyanurate (TAIC), triacrylformal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalate amide, triallyl phosphate, bismaleimide, fluorinated triallyl isocyanurate (1,3,5-tris(2,3,3-trifluoro-2-propenyl)-1,3,5-trimethylsilyl) and tetramethylsilyl. triazine-2,4,6-trione), tris(diallylamine)-S-triazine, triallyl phosphite, N,N-diallylacrylamide, 1,6-divinyldodecafluorohexane, hexaallyl phosphoramide, N,N,N',N'-tetraallylphthalamide, N,N,N',N'-tetraallylmalonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane, tri(5-norbornene-2-methylene) cyanurate, and triallyl phosphite. Among these, TAIC is preferred because of its excellent crosslinkability and physical properties as a heat dissipation material.

The amount of the crosslinking aid is not particularly limited. For example, the amount of the crosslinking aid may be 0.01 parts by mass or more and 10 parts by mass or less, and preferably 0.1 parts by mass or more and 5.0 parts by mass or less, per 100 parts by mass of the fluorine-containing elastomer.

If necessary, the elastomer composition may contain additives that are typically blended into fluorine-containing elastomer compositions, such as additives other than thermally conductive fillers (e.g., barium sulfate), processing aids (e.g., wax), plasticizers, colorants, stabilizers, adhesive aids, release agents, conductivity-imparting agents, surface anti-tack agents, flexibility-imparting agents, heat resistance improvers, and flame retardants.

The fluorine-containing elastomer in which the thermally conductive filler is dispersed can be obtained, for example, by adding and mixing the thermally conductive filler together with components such as the fluorine-containing elastomer when preparing the elastomer composition.

(2b) Applying the elastomer composition to the resin sheet Next, the elastomer composition is applied to the resin sheet. The application method is not particularly limited, and the elastomer composition may be coated on the resin sheet or the resin sheet may be immersed in the elastomer composition. According to the coating method, an elastomer region is easily formed on the surface of the resin sheet.

The coating of the elastomer composition may be performed on one side or both sides of the resin sheet. The immersion method is not particularly limited, and a vacuum impregnation method performed under vacuum or a vacuum pressure impregnation method performed while applying pressure under vacuum may be used.

Then, the resin sheet is dried. This retains the fluorine-containing elastomer in the voids of the resin sheet. The drying method is not particularly limited, and may be heat drying, vacuum drying, etc.

(3) Pressing process (S13)
The resin sheet holding the fluorine-containing elastomer is press-molded to obtain a thermally conductive sheet having a desired thickness.

Normally, when a sheet is formed by press molding using only a fluorine-containing elastomer, the thickness tends to vary. This makes it difficult to make the sheet thinner. The variation in thickness of sheets formed from fluorine-containing elastomer becomes more pronounced the larger and thinner the sheet is.

By using a resin sheet, the fluorine-containing elastomer can be molded into a sheet of uniform thickness by press molding. In particular, thin and even large sheets can be obtained.

In the pressing step, the fluorine-containing elastomer may be crosslinked. The conditions of the pressing step are not particularly limited and may be set appropriately taking into consideration the crosslinking conditions of the fluorine-containing elastomer. The fluorine-containing elastomer is crosslinked, for example, by heating at a temperature of 150°C or higher and 300°C or lower for 1 minute or longer and 24 hours or shorter. After the pressing step, a step of crosslinking the fluorine-containing elastomer may be carried out.

The obtained thermally conductive sheet is cut, drilled, etc. as necessary, and then mounted on various devices and electronic devices. According to the manufacturing method of this embodiment, a uniform, thin, and large-area thermally conductive sheet can be obtained, resulting in a high yield and being applicable to a variety of uses. The thermally conductive sheet is particularly suitable for use in semiconductor manufacturing equipment.

The present invention will be described in more detail with reference to the following examples, but is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified. The number of mixed parts is the mass of the solid content.

[Example 1]
(i) Preparation of Resin Sheet A PTFE nonwoven fabric (R-250 manufactured by Tomoegawa Paper Co., Ltd., porosity 65%, mass per unit area 190 g/m ² , fiber diameter 35.2 μm, thickness 0.25 mm) was prepared.

(ii) Preparation of elastomer composition A mixture was obtained containing 100 parts of a fluorine-containing elastomer (TFE/perfluoro(methyl vinyl ether)/cyano group-containing monomer=59.4/40.1/0.5 (molar ratio), heat resistance temperature in compression set test of 300° C., heat resistance temperature in TG method of 420° C., manufactured by Daikin Industries, Ltd.), 0.8 parts of a crosslinking agent (4,4′-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis[N1-phenyl-1,2-benzenediamine]), and 23 parts of a thermally conductive filler (carbon black, manufactured by Cancarb Thermax N990, D50: 280 nm). An organic solvent (FC770, manufactured by 3M) was mixed with this mixture to prepare an elastomer composition having a concentration of 4% by mass (viscosity 150 mPa·s).

(iii) Retention process of elastomer composition on resin sheet The above-mentioned elastomer composition was applied to one surface of a PTFE nonwoven fabric using a film applicator. After that, it was dried at 80°C for 12 hours to retain the elastomer composition in the voids on one surface side of the PTFE nonwoven fabric. Then, in the same manner as above, the elastomer composition was retained in the voids on the other surface side of the PTFE nonwoven fabric.

(iv) Press molding The PTFE nonwoven fabric holding the elastomer composition was placed in a 200 mm x 200 mm mold and press molded for 30 minutes at a load of 45 kgf/cm ² and a temperature of 180° C. In this way, a thermally conductive sheet A1 was obtained. An evaluation sample a1 of 100 mm x 100 mm was cut out from the thermally conductive sheet A1.

The proportion of fluorine-containing elastomer in thermally conductive sheet A1 was 49.4% by mass. The total amount of thermally conductive material was 11.4% by mass of thermally conductive sheet A1. Elastomer regions (each 53 to 59 μm thick) were formed on both sides of thermally conductive sheet A1. The heat resistance temperature of thermally conductive sheet A1 in the TG method was 420°C.

[Example 2]
A thermally conductive sheet A2 and an evaluation sample a2 (100 mm x 100 mm) thereof were obtained in the same manner as in Example 1, except that in the elastomer composition retaining step (iii) of Example 1, the elastomer composition was applied only to one surface of the PTFE nonwoven fabric.

The proportion of fluorine-containing elastomer in the obtained thermally conductive sheet A2 was 45.7% by mass. The total amount of thermally conductive material was 10.5% by mass of the thermally conductive sheet A2. An elastomer region (thickness 110 μm) was formed on one side of the thermally conductive sheet A2. The heat resistance temperature of the thermally conductive sheet A2 in the TG method was 420°C.

[Example 3]
A thermally conductive sheet A3 and an evaluation sample a3 (100 mm x 100 mm) thereof were obtained in the same manner as in Example 2, except that a PTFE nonwoven fabric carrying CNTs was used instead of the PTFE nonwoven fabric of Example 2. The heat resistance temperature of the thermally conductive sheet A3 in the TG method was 420°C.

The resin sheet was obtained by immersing the PTFE nonwoven fabric used in Example 2 in a dispersion containing CNTs (carbon nanotubes, Taiyo Nippon Sanso Corporation, CNT powder grade DL, diameter of cross section along the circumferential direction 5 nm to 20 nm, length 150 μm to 600 μm) and then drying. The amount of CNTs supported was 1.1% by mass of the PTFE nonwoven fabric before support.

The proportion of fluorine-containing elastomer in thermally conductive sheet A3 was 48.3% by mass. The total amount of thermally conductive material was 11.1% by mass of thermally conductive sheet A3. An elastomer region (thickness 98 μm) was formed on one side of thermally conductive sheet A3.

[Comparative Example 1]
A thermally conductive sheet B1 and its evaluation sample b1 (100 mm x 100 mm) were obtained in the same manner as in Example 1, except that no resin sheet was used. However, during press molding (4), the fluorine-containing elastomer could not spread to the corners of the 200 mm x 200 mm mold. The size of the obtained thermally conductive sheet B1 was about 170 mm x 180 mm. The heat resistance temperature of the thermally conductive sheet B1 in the TG method was 420 ° C.

[evaluation]
The following evaluations were carried out on the evaluation samples a1 to a3 and b1 obtained in Examples 1 to 3 and Comparative Example 1. The results are shown in Table 1.

(a) Thickness Measurement The thickness of the evaluation sample was measured at five points. The measurement points were five points near the four corners (points a to d in a clockwise direction) and the center (point e), each of which was spaced 3 cm or more apart. The average and standard deviation of the measurements were calculated.

(b) Measurement of adhesion to other members A test piece of 50 mm x 50 mm was cut out from the evaluation sample. This test piece was compressed with a SUS304 plate and heated at 250 ° C for 16 hours. After cooling to room temperature, the thermal conductive sheet and the SUS304 plate were peeled off. The force required for peeling was measured using a universal testing machine (HIT-L, manufactured by Japan Measurement Systems Co., Ltd.).

(c) Measurement of Thermal Conductivity The thermal conductivity was calculated by multiplying the thermal diffusivity of the evaluation sample by the specific heat of the evaluation sample obtained by the DSC method and the density of the evaluation sample obtained by the Archimedes method. The thermal diffusivity was measured under the following conditions using a laser flash method.

(Thermal Diffusivity)
Measuring equipment: ULVAC-RIKO TC-7000
Thermal diffusivity determination method: Half-time method Measurement temperature: Room temperature 25°C

(d) Measurement of Electrical Conductivity When the electrical conductivity was less than 1.00×10 ⁻⁴ S/m, the electrical resistivity of the evaluation sample was measured in accordance with JIS K 6911, and when the electrical conductivity was 1.00×10 ⁻⁴ S/m or more, the electrical resistivity was measured in accordance with JIS K 7194. The electrical conductivity was calculated from the electrical resistivity.

(e) Measurement of Hardness The Martens hardness of both surfaces of the evaluation sample was measured by a nanoindentation method in accordance with ISO 14577. Specifically, an indenter was pressed into both surfaces of the evaluation sample with a load of 10 mN. The Martens hardness was obtained from the pressing depth.

The thermally conductive sheets A1, A2, and A3 of Examples 1 to 3 are thin and uniform in thickness. On the other hand, in Comparative Example 1, no resin sheet was used, so the thermally conductive sheet B1 obtained was thick overall and had a large variation in thickness.

The thermally conductive sheets A1, A2, and A3 having the resin sheets of Examples 1 to 3 had a smaller adhesive strength to other members than the thermally conductive sheet B1 of Comparative Example 1. In particular, the adhesive strength of the thermally conductive sheets A2 and A3 having an elastomer region on only one side of Examples 2 and 3 was small. In other words, the thermally conductive sheets A1, A2, and A3 have excellent peelability, so the thermally conductive sheets can be removed smoothly while suppressing the generation of residue.

The thermally conductive sheet A3 of Example 3 had the highest thermal conductivity and electrical conductivity because it had a large total amount of thermally conductive filler and the thermally conductive filler was supported on the resin sheet.

The thermally conductive sheets A1, A2, and A3 of Examples 1 to 3 all have a low Martens hardness on the surface having the elastomer region. Therefore, the thermally conductive sheet has a high degree of adhesion to the heating element and/or heat sink, and further improvement in thermal conductivity can be expected.

The thermally conductive sheet of the present invention has high thermal conductivity and high heat resistance, making it particularly suitable for use in semiconductor manufacturing equipment.

10A, 10B Thermally conductive sheet 10X, 10Y Main surface 10a Elastomer region 11 Resin sheet (nonwoven fabric)
111 Fiber 12 Fluorine-containing elastomer 13 Thermally conductive material (thermally conductive filler)
131 Carbon nanotubes
132 Carbon Black

Claims (12)

A resin sheet having voids;
a fluorine-containing elastomer disposed at least inside the void;
a thermally conductive material;
the fluorine-containing elastomer is further disposed so as to cover at least a portion of at least one main surface of the resin sheet,
A thermally conductive sheet having a thickness of 0.05 mm or more and 0.5 mm or less. the thermally conductive material comprises a particulate thermally conductive material;
The thermally conductive sheet according to claim 1 , wherein at least a portion of the particulate thermally conductive material is supported on the resin sheet. The thermally conductive sheet according to claim 1 or 2, wherein the resin sheet contains a resin material having a heat resistance temperature of 150°C or higher. The thermally conductive sheet according to any one of claims 1 to 3, wherein the resin sheet is a fiber structure. The thermally conductive sheet according to any one of claims 1 to 4, wherein the thermally conductive material includes a fibrous carbon material. The thermally conductive sheet according to any one of claims 1 to 5, wherein the fluorine-containing elastomer is further arranged to cover one of the main surfaces of the resin sheet. The thermally conductive sheet according to any one of claims 1 to 5, wherein the fluorine-containing elastomer is further arranged to cover both main surfaces of the resin sheet. The thermally conductive sheet according to any one of claims 1 to 7, wherein the standard deviation of the thickness at any five points on the thermally conductive sheet is 0.020 or less. The thermally conductive sheet according to any one of claims 1 to 8, wherein the resin sheet is formed from a resin material containing a fluororesin. The thermally conductive sheet according to any one of claims 1 to 9, which is used in semiconductor manufacturing equipment. Providing a resin sheet having voids;
retaining a fluorine-containing elastomer in the voids of the resin sheet;
and a step of press-molding the resin sheet holding the fluorine-containing elastomer to obtain a thermally conductive sheet,
At least one of the resin sheet and the fluorine-containing elastomer has a thermally conductive material,
the fluorine-containing elastomer is disposed so as to cover inside voids of the resin sheet and at least a part of at least one of the main surfaces of the resin sheet,
The method for producing a thermally conductive sheet, wherein the thermally conductive sheet has a thickness of 0.05 mm or more and 0.5 mm or less. The method for manufacturing a thermally conductive sheet according to claim 11, wherein in the step of preparing the resin sheet, the resin sheet carrying the particulate thermally conductive material is prepared.

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