JP2012001638A - Heat-conductive sheet and process for producing heat-conductive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-conductive sheet excellent in heat conductivity, uniformity of thickness, and flexibility.SOLUTION: The heat-conductive sheet includes a silicone resin, a heat-conductive filler, and carbon fibers and the carbon fibers are oriented in the thickness direction, and the heat-conductive sheet contains the heat-conductive filler in the range of 40-55 vol.% and the carbon fibers in the range of 10-25 vol.%.

Description

  The present invention relates to a heat conductive sheet that promotes heat dissipation from a heat-generating electronic component and the like, and a method for manufacturing the heat conductive sheet.

  In recent electronic devices, heat generated in various electronic components has been effectively reduced by high-density mounting of semiconductor packages, high integration and high-speed of LSIs due to higher performance, smaller size and lighter weight. Measures to dissipate heat to the outside are a very important issue. Therefore, heat dissipation members such as heat sinks are attached to various electronic components of electrical equipment, such as heat-generating electronic components such as transistors and thyristors, through a sheet material having good thermal conductivity (hereinafter referred to as “thermal conductive sheet”). The measure of mounting is generally taken.

  In general, this type of heat conductive sheet is attached in a state of being in close contact with the heat generating electronic component or the like by flexibly following the unevenness of the mounted portion of the heat generating electronic component or the like serving as a heat generation source. Such a heat conductive sheet functions to reduce the contact thermal resistance between the heat-generating electronic component and the like and the heat radiating member, and efficiently conduct heat generated in the heat-generating electronic component and the like to the heat radiating member.

  The heat conductive sheet also serves as a protective material for preventing the deformation and damage of the heat radiating member and the heat generating electronic component when the heat radiating member is pressure-bonded to the heat generating electronic component. . Therefore, this heat conductive sheet is required not only to have high heat conductivity but also to be excellent in flexibility and shape followability. Furthermore, the heat conductive sheet is required to be formed thin in accordance with miniaturization of the heat generating electronic component and the electronic device casing. In response to such a demand, a heat conductive sheet in which carbon fiber having high heat conductivity is blended as a heat conductive material has also been proposed (see Patent Document 1).

  This type of heat conductive sheet is manufactured by forming a sheet base material in which a heat conductive material such as carbon fiber or aluminum oxide is blended in a polymer material such as silicone rubber and slicing it to a predetermined thickness. The Here, in the heat conductive sheet, since the slice thickness of the sheet greatly affects the thermal conductivity of each product, it is important to slice the thickness uniformly. In addition, since the heat conductive sheet exhibits high heat conduction characteristics because the carbon fiber is oriented in the thickness direction of the sheet, the carbon fiber is oriented in the thickness direction of the sheet in the slicing step. It is important to keep

  As a conventional method for slicing a silicone rubber block, the cutting edge angle and surface roughness of the cutting blade are regulated and moved linearly without rotation (Patent Document 2), or the relative relationship between the cutting blade and the rubber block. A method (Patent Document 3) has been proposed that defines a specific moving direction and blade angle.

  However, since the heat conductive sheet is required to have high flexibility and shape followability as described above, the sheet base material is easily deformed by the conventional slicing method, and it is difficult to slice into a thin and uniform thickness. there were. Further, in the conventional heat conductive sheet, the sliced surface is rubbed by the frictional resistance with the cutting blade, so that the orientation of the carbon fibers is disturbed and the heat conduction characteristics are deteriorated.

JP 2002-46137 A JP-A-9-225890 JP 2002-18782 A

  The present invention has been made in order to solve the above-described problems, and the object of the present invention is to provide a heat conductive sheet and a heat conductive sheet excellent in heat conduction characteristics, thickness uniformity, flexibility, and shape followability. It is to provide a manufacturing method.

  In order to solve the above-described problem, a thermally conductive sheet according to the present invention contains a silicone resin, a thermally conductive filler, and carbon fibers, and the carbon fibers are oriented in the thickness direction. In the sheet, the thermally conductive filler is contained in a range of 40 to 55% by volume, and the carbon fiber is contained in a range of 10 to 25% by volume.

  Moreover, the manufacturing method of the heat conductive sheet which concerns on this invention is the process of creating the mixed composition containing a silicone resin, a heat conductive filler, and carbon fiber, and forming the said mixed composition in column shape. , Orienting the carbon fibers in the columnar longitudinal direction, and slicing the columnar mixed composition in a direction perpendicular to the columnar longitudinal direction by a cutter provided with ultrasonic vibration in the slicing direction; It is what has.

  According to the heat conductive sheet which concerns on this invention, the heat conductive sheet excellent in the heat conductive characteristic and the compressibility can be obtained. Moreover, according to the manufacturing method of the heat conductive sheet which concerns on this invention, the heat conductive sheet excellent in heat conductive characteristics and compressibility can be manufactured by uniform thickness.

It is a table | surface which shows the compression rate according to the compounding ratio of a 1st silicone resin and a 2nd silicone resin. It is a table | surface which shows a combustion test and evaluation of the ease of extrusion of a sheet | seat base material. It is a graph which shows the relationship between the compounding quantity of the carbon fiber in a heat conductive sheet, and heat resistance. It is a table | surface which shows the compounding quantity of the material which comprises a heat conductive sheet. It is a perspective view which shows the process of manufacturing a heat conductive sheet by slicing a sheet | seat base material. It is an external view which shows a slicing apparatus. It is a graph which shows the relationship between the slicing method according to the presence or absence of ultrasonic vibration, and the thermal resistance value of a heat conductive sheet. It is a figure which shows the shape according to the slice speed | rate of an ultrasonic cutter, and the thickness of a heat conductive sheet. It is a table | surface which shows the characteristic of the heat conductive sheet according to the difference of the slice speed | rate of a sheet | seat base material, and the thickness of a heat conductive sheet. It is a table | surface which shows each characteristic of the heat conductive sheet sliced by changing the amplitude of the ultrasonic vibration provided to a cutter.

  Hereinafter, a thermal conductive sheet to which the present invention is applied and a method for manufacturing the thermal conductive sheet will be described in detail with reference to the drawings.

<Thermal conductive sheet>
The heat conductive sheet 1 to which the present invention is applied is disposed between a heat-generating electronic component such as an IC and a heat-dissipating component such as a heat sink, and transmits heat of the heat-generating electronic component to the heat sink side. By interposing this heat conductive sheet 1, heat can be efficiently transferred to the heat sink.

  The heat conductive sheet 1 is a sheet-like material in which pitch-based carbon fibers as a heat conductive material and spherical aluminum oxide (hereinafter simply referred to as alumina) as a heat conductive filler are blended in a silicone resin. By being oriented in the thickness direction of the sheet, heat is efficiently transferred in the thickness direction. The heat conductive sheet 1 is formed by forming a mixed composition in which silicone resin, carbon fiber and alumina are mixed into a columnar shape and orienting the carbon fiber in the longitudinal direction thereof to form a sheet base material 2. It is formed by slicing the material 2 into a sheet shape in a direction orthogonal to the longitudinal direction. In addition, the heat conductive sheet 1 is characterized in that carbon fiber is blended at 10 to 25% by volume and alumina is blended at 40 to 55% by volume.

  The silicone resin has physical properties excellent in flexibility, shape followability, heat resistance, and the like, and is configured by mixing a first silicone resin and a second silicone resin. The first silicone resin is a polyalkenylalkylsiloxane, and the second silicone resin is a polyalkylhydrogensiloxane that acts as a curing agent for the polyalkenylalkylsiloxane.

  In addition, commercially, the 1st silicone resin can be obtained in the state which mixed the platinum catalyst which acts as a catalyst of the said reaction. In addition, commercially, the second silicone resin can be obtained in a state where the above-mentioned polyalkenylalkylsiloxane and reaction modifier are mixed in addition to the polyalkylhydrogensiloxane.

  When the first silicone resin and the second silicone resin are a mixture as described above, the blending ratio of the first silicone resin is relatively high by simply blending these two resins in equal amounts by weight ratio, The blending ratio of the second silicone resin as the curing agent can be lowered.

  As a result, the heat conductive sheet 1 is not excessively cured, and thereby a certain compression rate can be generated. Since the heat conductive sheet 1 is interposed between the heat-generating electronic component and the heat sink, it is necessary to have a predetermined compressibility in the thickness direction in order to bring them into close contact, and at least a compression of 3% or more is required. It is preferable to provide a compression ratio of preferably 6% or more, more preferably 10% or more.

  And as shown in FIG. 1, the heat conductive sheet 1 makes the compounding ratio of the 1st silicone resin and the 2nd silicone resin 55: 45-50: 50. Thereby, the heat conductive sheet 1 has a compression rate of 3% or more (3.82%) even when the initial thickness is sliced as thin as 0.5 mm. Further, the thermal conductive sheet 1 has a compression ratio of 10.49% at an initial thickness of 1.0 mm at 52:48, and 13.21 at an initial thickness of 1.0 mm between 55:45 and 52:48. %, Both have a compression rate of 10% or more.

  Thus, since the heat conductive sheet 1 has a compressibility of 3% or more in the thickness direction despite the orientation of the carbon fibers in the thickness direction, the heat conductive sheet 1 is excellent in flexibility and shape followability. The heat-generating electronic component and the heat sink can be more closely attached to dissipate heat efficiently.

  Pitch-based carbon fiber is made from pitch as a main raw material and graphitized by heat treatment at a high temperature exceeding 2000 to 3000 ° C. or 3000 ° C. after each processing step such as melt spinning, infusibilization, and carbonization. The raw material pitch is divided into an isotropic pitch that is optically disordered and exhibits no deflection, and an anisotropic pitch (mesophase pitch) in which the constituent molecules are arranged in a liquid crystal form and exhibits optical anisotropy. Carbon fiber manufactured from an isotropic pitch has better mechanical properties and higher electrical and thermal conductivity than carbon fiber manufactured from an isotropic pitch. Use this mesophase pitch graphitized carbon fiber. Is preferred.

  Alumina is smaller than carbon fiber and has a particle size that can sufficiently function as a heat conductive material, and is closely packed with carbon fiber. Thereby, the heat conductive sheet can obtain a sufficient heat conduction path. DAW03 (manufactured by Denki Kagaku Kogyo Co., Ltd.) can be used as the alumina.

<Combination ratio of alumina and carbon fiber>
The thermal conductive sheet 1 is composed of the first and second silicone resins, carbon during the evaluation in the combustion test and the production of the sheet base material 2 from which the thermal conductive sheet 1 is cut according to the blending ratio of the carbon fiber and the alumina. Evaluation of the ease of extrusion when extruding a mixed composition in which fibers and alumina are mixed into a prismatic shape from a syringe changes. The sheet base material 2 is formed into a prismatic shape again after passing through a slit provided in the syringe so that carbon fibers are oriented in the longitudinal direction.

  FIG. 2 shows the evaluation in the combustion test (UL94V) of the heat conductive sheet 1 when the blending ratio of the carbon fiber to 50 g of alumina is changed, and the evaluation of the ease of extrusion when the sheet base material 2 is extruded into a prismatic shape. Show. In addition, the heat conductive sheet 1 uses 5.4 g of a first silicone resin (mixture of polyalkenylalkylsiloxane and a platinum catalyst) as a silicone resin, and a second silicone resin (polyalkylhydrogensiloxane, polyalkenylalkylsiloxane). And 5.4 g of a mixture of reaction modifiers).

  As shown in FIG. 2, by blending 14 g or more of carbon fiber with 50 g of alumina, both the 1 mm thick and 2 mm thick thermal conductive sheets 1 obtained an evaluation equivalent to V0 in the combustion test (UL94V). . Moreover, according to the heat conductive sheet 1 having a thickness of 2 mm, an evaluation corresponding to V0 in a combustion test (UL94V) was obtained by blending 8 g or more of carbon fiber with 50 g of alumina. At this time, the volume ratio of 50 g of alumina in the heat conductive sheet 1 is 45.8 vol%, and the volume ratio of 8 g of carbon fibers is 13.3 vol%.

  Moreover, the heat conductive sheet 1 can maintain the ease of extruding favorably in the manufacturing process of the sheet base material 2 by blending 8 g and 10 g of carbon fiber to 50 g of alumina. That is, the sheet base material 2 can smoothly pass through the slit provided in the syringe and can maintain a prismatic shape.

  Similarly, the heat conductive sheet 1 can maintain the ease of extrusion in the manufacturing process of the sheet base material 2 also by blending 12 g and 14 g of carbon fiber with 50 g of alumina. That is, the sheet base material 2 can smoothly pass through the slit provided in the syringe and can maintain a prismatic shape. In addition, the hardness of this sheet | seat base material 2 is harder than what mixed the said carbon fibers 8g and 10g.

  Moreover, the heat conductive sheet 1 was slightly impaired in extrudability in the manufacturing process of the sheet base material 2 by blending 16 g of carbon fiber with 50 g of alumina. That is, since the sheet base material 2 is hard, there is a case where a part of the base material leaks from a jig for fixing the slit provided in the syringe. However, the base material that has passed through the slit can maintain a prismatic shape. At this time, the volume ratio of 50 g of alumina in the heat conductive sheet 1 is 40.4% by volume, and the volume ratio of 16 g of carbon fibers is 23.5% by volume.

  Furthermore, the heat conductive sheet 1 could not be extruded in the manufacturing process of the sheet base material 2 when 17 g of carbon fiber was blended. That is, since the sheet base material 2 is hard, there is a case where a part of the base material leaks from a jig for fixing the slit provided in the syringe. And the base materials which passed the slit were not couple | bonded, but prismatic shape was not able to be maintained.

  From the above, the blending amount of the carbon fiber with respect to 50 g of alumina is 14 g at a sheet thickness of 1 mm and 8 g to 16 g at a sheet thickness of 2 mm, particularly when high flame resistance equivalent to V0 is required in the combustion test UL94V. It turns out that it is preferable.

  Moreover, as shown in FIG. 3, the compounding quantity of carbon fiber and a thermal resistance value have a correlation. As shown in FIG. 3, the thermal resistance (K / W) decreases as the blending amount of the carbon fiber increases, but it can be seen that the thermal resistance value becomes stable at about 10 g or more. On the other hand, when 17 g or more of carbon fiber is blended, it becomes difficult to extrude the sheet base material 2 as described above. Therefore, the heat conductive sheet 1 may have a blending amount of carbon fiber of 10 g or more and 16 g or less. preferable. Here, in the heat conductive sheet 1 having a thickness of 1 mm, the blending amount of the carbon fibers is set to 14 g with respect to 50 g of alumina from the viewpoint of flame retardancy of the heat conductive sheet 1 and ease of extrusion of the sheet base material 2. However, at this blending amount, as shown in FIG. 3, the value of thermal resistance is low and stable.

  From the above, as an example, FIG. 4 shows the blending of the thermally conductive sheet 1 having a thickness of 1 mm manufactured with the optimum blending ratio (weight ratio). As shown in FIG. 4, 5.4 g (7.219 wt%) of a mixture of polyalkenylalkylsiloxane and platinum catalyst as the first silicone resin, and polyalkylhydrogensiloxane and polyalkenylalkylsiloxane as the second silicone resin. 5.4 g (7.219 wt%) of the mixture of the reaction modifier and 50 g (66.8449 wt%) of the trade name DAW03 as alumina and trade name R-A301 (manufactured by Teijin Ltd.) as the pitch-based carbon fiber. 14 g (18.7166% by weight) was used.

<Slicing device>
Next, the configuration of the slicing apparatus 10 that slices the sheet base material 2 into individual heat conductive sheets 1 in order to obtain the heat conductive sheet 1 having the composition shown in FIG. 4 will be described. As shown in FIG. 5, the slicing apparatus 10 can form the thermally conductive sheet 1 while maintaining the orientation of the carbon fibers by slicing the sheet base material 2 with an ultrasonic cutter. Therefore, according to the slicing device 10, it is possible to obtain the heat conductive sheet 1 having good heat conduction characteristics in which the orientation of the carbon fibers is maintained in the thickness direction.

  Here, the sheet base material 2 is formed by first and second silicone resins, alumina, and carbon fibers being put into a mixer, mixed, and then extruded from a syringe provided in the mixer into a prismatic shape having a predetermined size. Is done. At this time, as for the sheet | seat base material 2, a carbon fiber is orientated to a longitudinal direction by passing the slit provided in the syringe. After the sheet base material 2 is extruded into a prism shape, it is put into an oven together with the mold and thermally cured to complete.

  As shown in FIG. 6, the slicing device 10 includes a work table 11 on which a prismatic sheet base material is placed, and an ultrasonic cutter 12 that slices the sheet base material 2 on the work table 11 while applying ultrasonic vibration. With.

  The work table 11 is provided with a silicone rubber 21 on a metal moving table 20. The moving table 20 can be moved in a predetermined direction by the moving mechanism 22 and sequentially feeds the sheet base material 2 to the lower part of the ultrasonic cutter 12. The silicone rubber 21 has a thickness sufficient to receive the cutting edge of the ultrasonic cutter 12. When the sheet base material 2 is placed on the silicone rubber 21, the work table 11 is moved in a predetermined direction in accordance with the slicing operation of the ultrasonic cutter 12, and the sheet base material 2 is sequentially removed from the ultrasonic cutter 12. Send to the bottom of 12.

  The ultrasonic cutter 12 includes a knife 30 for slicing the sheet base material 2, an ultrasonic oscillation mechanism 31 that applies ultrasonic vibration to the knife 30, and a lifting mechanism 32 that moves the knife 30 up and down. The knife 30 has its cutting edge directed toward the work table 11 and is moved up and down by an elevating mechanism 32 to slice the sheet base material 2 placed on the work table 11. The size and material of the knife 30 are determined according to the size and composition of the sheet base material 2 and are made of steel having a width of 40 mm, a thickness of 1.5 mm, and a blade edge angle of 10 °, for example.

  The ultrasonic oscillation mechanism 31 applies ultrasonic vibration to the knife 30 in the slice direction of the sheet base material 2. For example, the ultrasonic oscillation mechanism 31 has a transmission frequency of 20.5 kHz and amplitudes of three stages of 50 μm, 60 μm, and 70 μm. It is possible to adjust to.

  Such a slicing apparatus 10 can maintain the orientation of the carbon fibers of the thermally conductive sheet 1 in the thickness direction by slicing the sheet base material 2 while applying ultrasonic vibration to the ultrasonic cutter 12. it can.

  FIG. 7 shows the thermal resistance values (K / W) of the thermally conductive sheet sliced without applying ultrasonic vibration and the thermally conductive sheet 1 sliced while applying ultrasonic vibration by the slicing apparatus 10. Show. As shown in FIG. 7, the thermal conductive sheet 1 sliced while applying ultrasonic vibration by the slicing apparatus 10 is compared with the thermal resistance (K /) as compared to the thermal conductive sheet sliced without applying ultrasonic vibration. It can be seen that W) is kept low.

  This is because the slicing apparatus 10 imparts ultrasonic vibration in the slicing direction to the ultrasonic cutter 12, and therefore, the carbon fiber having low interface thermal resistance and oriented in the thickness direction of the heat conductive sheet 1. This is because it is difficult to be laid down by the knife 30. On the other hand, in the thermally conductive sheet sliced without applying ultrasonic vibration, the orientation of the carbon fiber as the thermally conductive material is disturbed by the frictional resistance of the knife, and the exposure to the cut surface is reduced. Resistance will rise. Therefore, according to the slicing apparatus 10, the heat conductive sheet 1 excellent in heat conduction characteristics can be obtained.

<Uniformity depending on slice speed and slice thickness>
Next, the relationship between the slicing speed of the sheet base material 2 by the slicing apparatus 10 and the thickness of the thermally conductive sheet 1 to be sliced was examined. The prism base sheet base material 2 having a side of 20 mm is formed at the blending ratio shown in the above-described embodiment, and the thickness of the sheet base material 2 is varied from 0.05 mm to 0.50 mm every 0.05 mm. The sheet 1 was formed by changing the slice speed of the ultrasonic cutter 12 to 5 mm, 10 mm, 50 mm, and 100 mm per second and slicing, and the appearance of each thermally conductive sheet 1 was observed. The ultrasonic vibration applied to the ultrasonic cutter 12 had a transmission frequency of 20.5 kHz and an amplitude of 60 μm.

  The observation results are shown in FIG. As shown in FIG. 8, when the thickness was 0.15 mm or less, deformation occurred regardless of the slice speed. On the other hand, at a thickness of 0.20 mm or more, no deformation was observed in the heat conductive sheet 1 even when the slicing speed was increased. That is, according to the slicing apparatus 10, the sheet base material 2 having the blending ratio shown in FIG. 4 can be uniformly sliced with a thickness of 0.20 mm or more.

<Thermal conductivity and compressibility depending on slice speed and slice thickness>
Next, the relationship between the slicing speed of the sheet base material 2 by the slicing apparatus 10, the thermal conductivity, and the compressibility in the thickness direction was examined. Thermal conductivity of thicknesses 0.20 mm, 0.25 mm, 0.30 mm, 0.50 mm that were not deformed in the examination of the slice speed and sheet thickness, and slice speeds of 5 mm, 10 mm, 50 mm, and 100 mm per second. The sheet 1 was measured for thermal conductivity and compression rate. The measurement results are shown in FIG.

  As shown in FIG. 9, among the thermal conductive sheets 1, the thermal conductive sheet 1 excluding the sample having a sheet thickness of 0.50 mm has an ultrasonic cutter 12 speed of 5 mm, 10 mm, or 50 mm per second. Even when sliced at a speed of 1, it has good heat conduction characteristics and has a compression rate of 10% or more, and is excellent in flexibility and shape followability. Moreover, even when the speed of the ultrasonic cutter 12 is sliced at 100 mm per second, the thermally conductive sheet 1 having sheet thicknesses of 0.25 mm and 0.20 mm has good thermal conductivity characteristics and is 10% or more. It has a compression ratio and is excellent in flexibility and shape followability.

  On the other hand, the heat conductive sheet 1 having a sheet thickness of 0.30 mm is excellent in heat conduction characteristics when the speed of the ultrasonic cutter 12 is sliced at 100 mm per second, but has a compression rate of 3.72%. fell.

  In addition, the thermally conductive sheet 1 having a sheet thickness of 0.50 mm has good thermal conductivity characteristics when the speed of the ultrasonic cutter 12 is sliced at any of 5 mm, 10 mm, and 50 mm per second. It has a compression ratio of 5% or more, and has good flexibility and shape followability. On the other hand, the heat conductive sheet 1 having a sheet thickness of 0.50 mm has good heat conduction characteristics when the speed of the ultrasonic cutter 12 is sliced at 100 mm per second, but has a compression rate of 2.18%. And lower than 3%, the flexibility and shape followability are lowered.

<Amplitude and compression ratio>
FIG. 10 shows the characteristics of the thermally conductive sheet 1 sliced by changing the amplitude of ultrasonic vibration applied to the ultrasonic cutter 12 in three stages of 50 μm, 60 μm, and 70 μm. The heat conductive sheet 1 was formed at the blending ratio shown in FIG. 4, and the measurement load was 1 kgf / cm ² . As shown in FIG. 10, when the amplitude is 70 μm, the heat conductive sheet 1 has a compression rate of 2.18%, which is lower than 3% as in the conventional case, and is inferior in flexibility and shape followability. On the other hand, when the amplitude is 50 μm and 60 μm, the heat conductive sheet 1 has a compression rate of 3% or more, and has good flexibility and shape following ability.

<Others>
In addition, the sheet | seat base material 2 is not limited to prismatic shape, It can form in the column shape which has various cross-sectional shapes according to the shape of the heat conductive sheet 1, such as a column shape. Further, although spherical alumina is used as the thermally conductive filler, in the present invention, any one of spherical aluminum nitride, zinc oxide, silicone powder, metal powder, or a mixture thereof can be used.

DESCRIPTION OF SYMBOLS 1 Thermal conductive sheet, 2 sheet | seat base material, 10 slicing apparatus, 11 Work table, 12 Ultrasonic cutter, 20 Moving stand, 21 Silicone rubber, 30 Knife, 31 Ultrasonic oscillation mechanism, 32 Lifting mechanism

DESCRIPTION OF SYMBOLS 1 Thermal conductive sheet | seat, 2 sheet | seat base material, 10 Slice apparatus, 11 Work table, 12 Ultrasonic cutter, 20 Moving stand, 21 Silicone rubber, 22 Moving mechanism, 30 Knife, 31 Ultrasonic oscillation mechanism, 32 Lifting mechanism

Claims (14)

In a thermally conductive sheet containing a silicone resin, a thermally conductive filler, and carbon fibers, the carbon fibers are oriented in the thickness direction,
The thermally conductive filler is contained in the range of 40 to 55% by volume,
The heat conductive sheet in which the said carbon fiber is contained in 10-25 volume%. The thermally conductive filler is contained in an amount of 40.4 to 45.8% by volume,
The heat conductive sheet according to claim 1, wherein the carbon fiber is contained in an amount of 13.3 to 23.5% by volume.   The heat conductive sheet according to claim 2, wherein 10 g or more of the carbon fiber is blended with respect to 50 g of the heat conductive filler.   The heat conductive sheet according to claim 3, wherein the carbon fiber is blended in an amount of 16 g or less with respect to 50 g of the heat conductive filler.   In the silicone resin, the first alkenylalkylsiloxane, which is a first silicone resin, and the polyalkylhydrogensiloxane, which is a second silicone resin, are hard-reacted with a platinum catalyst so that the compression rate becomes 3%. The heat conductive sheet according to any one of claims 1 to 4, wherein the silicone resin is blended in a larger amount than the second silicone resin.   The heat according to any one of claims 1 to 5, wherein the thermally conductive filler is any one of aluminum oxide, aluminum nitride, zinc oxide, silicon powder, metal powder, or a mixture of two or more thereof. Conductive sheet. Creating a mixed composition comprising a silicone resin, a thermally conductive filler, and carbon fibers;
Forming the mixed composition into a columnar shape, and orienting the carbon fibers in the columnar longitudinal direction;
A method for producing a thermally conductive sheet, comprising: slicing the columnar mixed composition in a direction perpendicular to the columnar longitudinal direction with a cutter provided with ultrasonic vibration in a slicing direction.   The method of manufacturing a thermally conductive sheet according to claim 7, wherein the ultrasonic vibration has a transmission frequency of 20.5 kHz and an amplitude of 60 µm.   The manufacturing method of the heat conductive sheet of Claim 8 which slices the thickness of the said heat conductive sheet into 0.20 mm or more.   The method for producing a thermally conductive sheet according to claim 9, wherein the slicing speed of the cutter is 100 mm or less per second and the thickness of the thermally conductive sheet 1 is sliced to 0.30 mm or less.   The method for producing a thermally conductive sheet according to claim 9, wherein the cutter has a slicing speed of 50 mm or less per second.   The method for manufacturing a thermally conductive sheet according to claim 10, wherein the slicing speed of the cutter is 50 mm or less per second.   The manufacturing method of the heat conductive sheet of Claim 10 which slices the thickness of the said heat conductive sheet 1 to 0.25 mm or less.   The thermal conductivity according to any one of claims 7 to 13, wherein the thermal conductive sheet according to any one of claims 1 to 6 is formed by slicing the mixed composition. Sheet manufacturing method.

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