Heat dissipation sheet

Abstract

To provide a heat dissipation sheet capable of improving a heat dissipation effect by reducing warpage of an adherend and suppressing the occurrence of cracks, etc., increasing adhesion to the adherend, and reducing contact thermal resistance.SOLUTION: A heat dissipation sheet (1) interposed between a heating element and a heat radiating element includes a plurality of slits (2) opening on at least one side of the heat dissipation sheet (1), and a pair of mutually opposing side walls (3) of the slits (2) are separated from each other in at least a portion of the slit (2).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a heat dissipation sheet, and more particularly to a heat dissipation sheet interposed between a heat generating body and a heat radiator.

Background Art

[0002] In recent years, electric vehicles, hybrid vehicles, etc. that use an electric motor as a main drive source or an auxiliary drive source for running have been increasing. In an inverter that controls these, power modules such as insulated gate bipolar transistors (IGBTs) generate a large amount of heat. Therefore, such a heat generating body is used by being attached to a heat radiator such as a heat sink in order to release the heat generated during driving. In this case, in order to smoothly transfer heat from the heat generating body to the heat radiator, a heat dissipation sheet is sandwiched between the heat generating body and the heat radiator.

[0003] Regarding such a heat dissipation sheet, various methods for improving the heat conduction from the heat generating body to the heat radiator have been studied. Patent Document 1 discloses that in a power module including a base plate, a ceramic insulating substrate joined on the base plate, and a semiconductor element joined on the ceramic insulating substrate, and a heat dissipation component attached to the base plate side of the power module via a heat dissipation sheet, the flatness of the surface of the base plate on the side opposite to the ceramic insulating substrate is set to 20 μm or less.

[0004] Furthermore, when attaching a heat dissipation sheet, a gap tends to form between the heat dissipation sheet and the heat-generating element or heat sink that is attached to it, meaning that air is easily retained, which has the disadvantage of reducing heat conduction from the heat-generating element to the heat sink. Patent Document 2 discloses a sheet in which multiple first slits are arranged along the length direction of the sheet, communicating with both ends in the width direction of the sheet and connecting to at least one side surface in the thickness direction of the sheet. The slits in Patent Document 2 are slits with no cutting width, that is, when the sheet is not stretched in the direction of the slit width, both sides of the slit are in close contact, and it is said that by putting such slits in the sheet, it is possible to make it difficult for air to be retained between the adherend and the sheet when attaching the sheet to the adherend. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-067801 [Patent Document 2] Japanese Patent Publication No. 2019-156875 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, with the conventional heat dissipation sheets, when attached using screws, a significant difference in thickness occurs between areas of high and low compression, such as near the screws. This can cause the substrate inside the heat-generating element to warp, potentially leading to crack formation. Furthermore, the conventional heat dissipation sheets are still insufficient in terms of adhesion to the substrate, and there is a need for heat dissipation sheets that reduce contact thermal resistance and improve heat dissipation efficiency.

[0007] The object of this disclosure is to provide a heat dissipation sheet that can reduce warping of the adherend and suppress the occurrence of cracks, while improving adhesion to the adherend, reducing contact thermal resistance, and improving the heat dissipation effect. [Means for solving the problem]

[0008] A heat dissipation sheet according to one aspect of the present disclosure is a heat dissipation sheet interposed between a heat-generating element and a heat sink. The heat dissipation sheet has a plurality of slits opening on at least one surface of the heat dissipation sheet. In at least a portion of the slits, a pair of opposing side walls of the slits are spaced apart. [Effects of the Invention]

[0009] According to this disclosure, it is possible to reduce the warping of the adherend, suppress the occurrence of cracks, etc., while increasing adhesion to the adherend, reducing contact thermal resistance, and improving the heat dissipation effect. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1A is a schematic cross-sectional view showing an example of the heat dissipation sheet of this embodiment. Figure 1B is a schematic cross-sectional view showing another example of the same heat dissipation sheet. Figure 1C is a schematic cross-sectional view showing yet another example of the same heat dissipation sheet. [Figure 2] Figure 2A is a schematic plan view showing an example of the heat dissipation sheet of this embodiment, and Figure 2B is a schematic plan view showing another example of the same heat dissipation sheet. [Modes for carrying out the invention]

[0011] 1. Overview Hereinafter, a heat dissipation sheet 1 according to one embodiment of this disclosure will be described with reference to the drawings. Note that the following embodiment is only one of many embodiments of this disclosure. The following embodiment can be modified in various ways depending on the design, as long as the objectives of this disclosure are achieved.

[0012] The heat dissipation sheet 1 is typically used as an interposed material between a heat-generating element and a heat sink. The heat dissipation sheet 1 is compressed by, for example, being sandwiched between the heat-generating element and the heat sink and tightened with screws or the like, thereby bringing it into close contact with the substrate and conducting the heat generated by the heat-generating element to the heat sink. However, with conventional heat dissipation sheets, it was difficult to improve the adhesion with the substrate and reduce the contact thermal resistance. Furthermore, with the aforementioned conventional heat dissipation sheets, when attached using screws, a large difference in the thickness of the heat dissipation sheet occurs in areas where the compression is high and areas where the compression is low, such as near the screws. This can cause the substrate inside the heat-generating element to warp, potentially leading to crack formation.

[0013] In response to this, the inventors have found that the compressibility of the heat dissipation sheet 1 can be increased by forming a plurality of slits 2 that open on at least one surface of the heat dissipation sheet 1, and by shaping the slits 2 so that a pair of opposing side walls 3 (one side wall 3A and the other side wall 3B) constituting the slits 2 are spaced apart, thereby solving the aforementioned problem, and have completed this disclosure.

[0014] The heat dissipation sheet 1 of this embodiment is a heat dissipation sheet interposed between a heat generating element and a heat sink. The heat dissipation sheet 1 has a plurality of slits 2 opening on at least one surface of the heat dissipation sheet 1, and is characterized in that at least a portion of the slits 2 has a pair of opposing side walls 3 (3A and 3B) of the slits 2 spaced apart.

[0015] The heat dissipation sheet 1 of this embodiment can reduce the warping of the adherend and suppress the occurrence of cracks, while increasing adhesion to the adherend and reducing contact thermal resistance, thereby improving the heat dissipation effect. The heat dissipation sheet 1 of this embodiment has a plurality of slits 2, and in at least a part of these slits 2, the pair of opposing side walls 3 (3A and 3B) of the slits 2 are spaced apart, that is, the slits 2 have width in at least a part, that is, there are gaps in the material of the heat dissipation sheet 1. When the heat dissipation sheet 1 is compressed, the material of the heat dissipation sheet 1 enters these gaps, which is thought to improve the compressibility of the heat dissipation sheet 1. The "width" of the slits 2 refers to the distance (length) between the pair of side walls 3 (3A and 3B) that constitute the slits 2. As a result, even when the heat dissipation sheet 1 is installed using screws or the like, the thickness does not differ significantly between the area near the screws and the other areas, which is thought to reduce the warping of the adherend and suppress the occurrence of cracks. Furthermore, the heat dissipation sheet 1 can improve adhesion to the adherend and reduce contact thermal resistance, and as a result, it is thought that the heat dissipation effect can be improved.

[0016] 2.Details <Heat dissipation sheet> The heat dissipation sheet 1 according to this embodiment has a plurality of slits 2. These slits 2 open to at least one surface of the heat dissipation sheet 1. Furthermore, these slits 2 have a pair of opposing side walls 3 (3A and 3B), and these side walls 3A and 3B are spaced apart. Thus, in this disclosure, "slit" means a narrow gap.

[0017] Each of the plurality of slits 2 may open only on one surface of the heat dissipation sheet 1, or may open on one or the other surface. Also, a part of the plurality of slits 2 may open on both surfaces of the heat dissipation sheet 1. If the slit 2 opens on both surfaces of the heat dissipation sheet 1, the heat dissipation effect of the heat dissipation sheet 1 can be further improved. When the slit 2 opens on both surfaces of the heat dissipation sheet 1, that is, when the slit 2 penetrates in the thickness direction of the heat dissipation sheet 1, this slit 2 is not formed across both ends of the surface of the heat dissipation sheet 1 in a plan view.

[0018] Figs. 1A to 1C are cross-sectional views of the heat dissipation sheet 1. The slit 2 of the heat dissipation sheet 1 in Fig. 1A opens on one surface (the upper surface of the heat dissipation sheet 1). In the heat dissipation sheet 1 of Fig. 1B, the slit 2 opening on one surface (the upper surface of the heat dissipation sheet 1) and the slit 2 opening on the other surface (the lower surface of the heat dissipation sheet 1) are mixed. The slit 2 of the heat dissipation sheet 1 in Fig. 1C opens on both surfaces (the upper surface and the lower surface of the heat dissipation sheet 1).

[0019] The average width of the plurality of slits 2 is preferably 0.01 mm or more and 0.5 mm or less. By setting the average width of the slit 2 within the above range, the heat dissipation effect of the heat dissipation sheet 1 can be further improved. This average width is more preferably 0.02 mm or more and 0.4 mm or less, and even more preferably 0.03 mm or more and 0.3 mm or less. The "average width" of the plurality of slits 2 means the arithmetic average value of the widths (mm) of the slits 2 over the entire heat dissipation sheet 1.

[0020] The average pitch of the plurality of slits 2 is preferably 0.1 mm or more and 5 mm or less. By setting the average pitch of the slit 2 within the above range, the heat dissipation effect of the heat dissipation sheet 1 can be further improved. This average pitch is more preferably 0.3 mm or more and 3 mm or less, and even more preferably 0.5 mm or more and 1 mm or less. The "average pitch" of the plurality of slits 2 means the arithmetic average value of the intervals (pitches: mm) between adjacent slits 2 over the entire heat dissipation sheet 1.

[0021] When the heat dissipation sheet 1 is pressurized at 100 kPa in the thickness direction, the compression ratio of the heat dissipation sheet 1 is preferably 5% or more and 50% or less. By setting the compression ratio of the heat dissipation sheet 1 within the above range, the heat dissipation effect of the heat dissipation sheet 1 can be further improved. This compression ratio is more preferably 10% or more and 45% or less, and even more preferably 20% or more and 40% or less. The "compression ratio (%) when pressurized at 100 kPa in the thickness direction" of the heat dissipation sheet means the compression ratio of the material forming the heat dissipation sheet. Assuming the thickness when not pressurized is T0 and the thickness when pressurized at 100 kPa is T1, it is the value of (T0 - T1) / T0 expressed as a percentage.

[0022] Examples of the cross-sectional shape of the slit 2 include a rectangular shape, a V-shaped shape, a U-shaped shape, etc. By setting the cross-sectional shape of the slit 2 to the above shape in which the side walls 3 are separated from each other throughout the slit 2, the heat dissipation sheet 1 can have higher compressibility, so that the heat dissipation effect can be further improved.

[0023] The ratio of the average depth of the plurality of slits 2 to the average thickness of the heat dissipation sheet 1 is preferably 10% or more and 80% or less. Assuming that the depth of the slit 2 opening on both surfaces of the heat dissipation sheet 1 is the same as the average thickness of the heat dissipation sheet 1. By setting the average depth of the plurality of slits 2 within the above range, the heat dissipation effect of the heat dissipation sheet 1 can be further improved. This average depth is more preferably 20% or more and 70% or less, and even more preferably 30% or more and 60% or less. The "average depth" of the plurality of slits 2 refers to the arithmetic mean value of the depths of the slits 2 over the entire heat dissipation sheet 1. The "average thickness" of the heat dissipation sheet 1 is the arithmetic mean value of the thicknesses measured at a plurality of points (for example, any 10 points) on the heat dissipation sheet 1.

[0024] In the heat dissipation sheet 1 of the present embodiment, when the heat dissipation sheet 1 is compressed in the thickness direction, it is preferable that at least a part of the opposing side walls 3 (3A and 3B) of the slit 2 come into contact with each other. The heat dissipation sheet 1 can exhibit a higher heat dissipation effect because the slit 2 has such physical properties.

[0025] The pressure applied to the heat dissipation sheet 1 in the thickness direction when the side walls 3 of the slits 2 come into contact with each other is, for example, 10 kPa or more and 1000 kPa or less, preferably 50 kPa or more and 500 kPa or less, and more preferably 100 kPa or more and 400 kPa or less.

[0026] In the heat dissipation sheet 1 of this embodiment, α, which is calculated by the following formula (1), is preferably 0.1 or more and 5 or less.

[0027] α = P × A × w / (v × 100) ... (1) P: Poisson's ratio of the heat dissipation sheet A: Compression ratio of the heat dissipation sheet when pressurized at 100kPa in the thickness direction (%) w: Average pitch of multiple slits (mm) v: Average width of multiple slits (mm)

[0028] The "Poisson's ratio" of the heat dissipation sheet, represented by P, refers to the Poisson's ratio of the material constituting the heat dissipation sheet 1. This value is measured by a strain gauge during a tensile test performed on a test piece made from this material.

[0029] The "compressibility" of the heat dissipation sheet represented by A refers to the compressibility of the material constituting heat dissipation sheet 1, and is a value measured by pressurizing a test piece made from this material at 100 kPa.

[0030] P × (A / 100) × w corresponds to the length that is expected to increase horizontally when the region (width w) between adjacent slits 2 is pressurized at 100 kPa in the thickness direction. If this length is approximately the same as v (average width of the slits) (α is approximately 1), then the opposing side walls 3 (3A and 3B) of slit 2 are expected to be in contact with each other.

[0031] By setting the value of α within the above range, the heat dissipation effect of the heat dissipation sheet 1 can be further improved. If α exceeds 5, the average width may be too small relative to the average pitch, making it difficult to form the slits 2. If α is less than 0.1, the average width may be too large relative to the average pitch, and even if the heat dissipation sheet 1 is compressed during installation, the contact area between the heat dissipation sheet 1 and the adherend may be insufficient, reducing the heat dissipation effect of the heat dissipation sheet 1. The lower limit of α is more preferably 0.2 or higher, even more preferably 0.5 or higher, and particularly preferably 0.8 or higher. The upper limit of α is more preferably 4 or lower, even more preferably 3 or lower, and particularly preferably 2 or lower.

[0032] Figures 2A and 2B are plan views of the heat dissipation sheet 1. In Figure 2A, the heat dissipation sheet 1 has multiple slits 2 that are parallel to each other and extend in one direction. In Figure 2B, the heat dissipation sheet 1 has multiple slits 2 that form a grid, including those that are parallel to each other and extend in one direction, and those that extend in a direction perpendicular to this direction and are also parallel to each other.

[0033] The heat dissipation sheet 1 may include only a plurality of slits 2 that extend in one direction parallel to each other, as shown in the heat dissipation sheet 1 of Figure 2A, or it may include a first slit 2X and a second slit 2Y as the plurality of slits 2, with the first slit 2X and the second slit 2Y intersecting each other, as shown in the heat dissipation sheet 1 of Figure 2B. The heat dissipation effect of the heat dissipation sheet 1 can be further improved by including two types of slits 2 that are oriented in different directions.

[0034] The heat dissipation sheet 1 typically contains resin and filler. By forming the heat dissipation sheet 1 with a material containing filler, the heat dissipation effect can be further improved.

[0035] The resin is not particularly limited, and one or more types selected from, for example, thermoplastic resins, thermoplastic elastomers, thermosetting resins, and crosslinked rubbers can be used as appropriate depending on the required performance of the heat dissipation sheet 1.

[0036] Examples of thermoplastic resins include polyethylene, polypropylene, ethylene-α-olefin copolymers such as ethylene-propylene copolymer, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyacetal, polyvinylidene fluoride, fluororesins such as polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, ABS resin, polyphenylene ether (PPE) resin, modified PPE resin, aliphatic or aromatic polyamide, polyimide, polyamide-imide, poly(meth)acrylic acid, poly(meth)acrylic acid ester, polycarbonate, polyphenylene sulfide, polysulfone, polyethersulfone, polyethernitrile, polyetherketone, polyketone, liquid crystal polymer, silicone resin, and ionomer.

[0037] Examples of thermoplastic elastomers include styrene-butadiene block copolymers, styrene-isoprene block copolymers, hydrogenated polymers thereof, styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and polyamide-based thermoplastic elastomers.

[0038] Examples of thermosetting resins include epoxy resins, polyimides, bismaleimide resins, benzocyclobutene resins, phenolic resins, unsaturated polyesters, diallyl phthalate resins, silicone resins, polyurethanes, polyimide silicones, thermosetting polyphenylene ethers, and modified PPE resins.

[0039] Examples of crosslinked rubbers include natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene copolymer rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene-propylene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, butyl rubber, halogenated butyl rubber, fluororubber, urethane rubber, and silicone rubber.

[0040] Examples of fillers include graphite powders such as flaky graphite powder, earthy graphite powder, spherical graphite powder, and artificial graphite powder, as well as inorganic fillers such as spherical aluminum oxide. Among these, flaky graphite powder is preferred. In flaky graphite powder, the crystal planes of graphite are spread in the plane direction, and it has extremely high thermal conductivity in the isodirectional direction within that plane. The filler may include one or more types.

[0041] When the filler contains flake-shaped graphite powder, it is preferable that the flake-shaped graphite powder is oriented in the direction in which the slit 2 opens. By oriented the flake-shaped graphite powder in the direction in which the slit 2 opens, the heat conduction in the thickness direction of the heat dissipation sheet 1 can be increased, further improving the heat dissipation effect. In addition, by oriented the flake-shaped graphite powder in the direction in which the slit 2 opens, it becomes easier to form the slit 2 in a desired shape.

[0042] In addition to the resin and filler, the heat dissipation sheet 1 may contain additives such as plasticizers, dispersants, coupling agents, adhesives, flame retardants, antioxidants, curing retarders, catalysts, and colorants.

[0043] The shape of the heat dissipation sheet 1 is not particularly limited and can be a square, a rectangle or other polygon, a circle, etc. The dimensions of the heat dissipation sheet 1 in plan view are preferably such that the length of one side is 1 mm or more and 30 cm or less in the case of a quadrilateral, and 5 mm or more and 10 cm or less.

[0044] <Manufacturing method for heat dissipation sheets> Next, a method for manufacturing the heat dissipation sheet according to this embodiment will be described. First, the material for forming the heat dissipation sheet 1 is prepared. This preparation involves mixing, for example, a resin with a filler containing flaky graphite powder to prepare a mixed composition.

[0045] Next, the prepared mixed composition is formed into a sheet. This molding can be done, for example, by die molding. If the mixed composition contains flake-shaped graphite powder or the like, it is preferable to orient the flake-shaped graphite powder or the like in the direction in which the slit 2 opens. This orientation can be achieved in the molding process by, for example, (i) a magnetic field orientation method in which the mixed composition is placed in a magnetic field to orient the flake-shaped graphite powder or the like along the magnetic field, and then the resin is cured; or (ii) a laminated slicing method in which a preliminary sheet is produced by applying shear force to the mixed composition to make a thin plate-like sheet, multiple sheets of this sheet are laminated and cured to produce a laminated block, and the laminated block is cut to obtain a sheet.

[0046] Next, the heat dissipation sheet 1 can be manufactured by forming slits 2 in the obtained sheet. Methods for forming these slits 2 include, for example, removing the material in the area that will become the slit 2 using a cutting tool, or eliminating the material in the area that will become the slit 2 using a laser.

[0047] (summary) As is clear from the embodiments described above, the heat dissipation sheet (1) of the first embodiment is a heat dissipation sheet (1) interposed between a heat generating element and a heat sink. The heat dissipation sheet (1) has a plurality of slits (2) opening on at least one surface of the heat dissipation sheet (1). At least a portion of the slits (2) are spaced apart from each other by a pair of opposing side walls (3) of the slits (2).

[0048] According to the first embodiment, the heat dissipation sheet (1) can improve the heat dissipation effect by reducing the warping of the adherend and suppressing the occurrence of cracks, while also increasing adhesion to the adherend and reducing contact thermal resistance.

[0049] In the second embodiment of the heat dissipation sheet (1), when the heat dissipation sheet (1) is compressed in the thickness direction, the opposing side walls (3) of the slit (2) come into contact with each other.

[0050] According to the second embodiment, the heat dissipation sheet (1) can exhibit a higher heat dissipation effect because the slit (2) has such physical properties.

[0051] In the third embodiment of the heat dissipation sheet (1), in the first or second embodiment, α, which is calculated by the following formula (1), is 0.1 or more and 5 or less. α = P × A × w / (v × 100) ... (1) P: Poisson's ratio of the heat dissipation sheet A: Compression ratio of the heat dissipation sheet when pressurized at 100kPa in the thickness direction (%) w: Average pitch of multiple slits (mm) v: Average width of multiple slits (mm)

[0052] According to the third embodiment, the heat dissipation effect of the heat dissipation sheet (1) can be further improved.

[0053] In the fourth embodiment of the heat dissipation sheet (1), in any one of the first to third embodiments, the compressibility of the heat dissipation sheet (1) when it is pressurized at 100 kPa in the thickness direction is 5% or more and 50% or less.

[0054] According to the fourth embodiment, the heat dissipation effect of the heat dissipation sheet (1) can be further improved.

[0055] In the fifth embodiment of the heat dissipation sheet (1), in any one of the first to fourth embodiments, the average width of the multiple slits (2) is 0.01 mm or more and 0.5 mm or less.

[0056] According to the fifth embodiment, the heat dissipation effect of the heat dissipation sheet (1) can be further improved.

[0057] In the heat dissipation sheet (1) of the sixth embodiment, in any one of the first to fifth embodiments, the ratio of the average depth of the multiple slits (2) to the average thickness of the heat dissipation sheet (1) is 10% or more and 80% or less.

[0058] According to the sixth embodiment, the heat dissipation effect of the heat dissipation sheet (1) can be further improved.

[0059] In the seventh embodiment of the heat dissipation sheet (1), in any one of the first to sixth embodiments, the average pitch of the multiple slits (2) is 0.1 mm or more and 5 mm or less.

[0060] According to the seventh embodiment, the heat dissipation effect of the heat dissipation sheet (1) can be further improved.

[0061] In the eighth embodiment of the heat dissipation sheet (1), in any one of the first to seventh embodiments, some of the plurality of slits (2) open on both sides of the heat dissipation sheet (1).

[0062] According to the eighth aspect, if the slit (2) is open on both sides of the heat dissipation sheet (1), the heat dissipation effect of the heat dissipation sheet (1) can be further improved.

[0063] In the heat dissipation sheet (1) of the ninth embodiment, in any one of the first to eighth embodiments, the cross-sectional shape of the slit (2) is rectangular, V-shaped, or U-shaped.

[0064] According to the ninth aspect, by making the cross-sectional shape of the slit (2) such that the side walls (3) are spaced apart throughout the entire slit (2), the heat dissipation sheet (1) can be made more compressible, and thus the heat dissipation effect can be further improved.

[0065] In the heat dissipation sheet (1) of the tenth embodiment, in any one of the first to ninth embodiments, the plurality of slits (2) include a first slit (2X) and a second slit (2Y), and the first slit (2X) and the second slit (2Y) intersect each other.

[0066] According to the tenth embodiment, the heat dissipation effect can be further improved by including two types of slits (2) that are oriented in different directions.

[0067] In the eleventh embodiment of the heat dissipation sheet (1), in any one embodiment from the first to the tenth, the heat dissipation sheet (1) includes a resin and a filler.

[0068] According to the eleventh embodiment, the heat dissipation sheet (1) can be made of a material containing a filler, thereby further improving the heat dissipation effect.

[0069] In the twelfth embodiment, the heat dissipation sheet (1) contains, in the eleventh embodiment, flake-shaped graphite powder as a filler, and the flake-shaped graphite powder is oriented in the direction in which the slit (2) opens.

[0070] According to the twelfth embodiment, the flake-shaped graphite powder is oriented in the direction of the opening of the slit (2), which increases the heat conduction in the thickness direction of the heat dissipation sheet (1) and further improves the heat dissipation effect. In addition, the orientation of the flake-shaped graphite powder in the direction of the opening makes it easier to form the slit (2) in a desired shape. [Explanation of Symbols]

[0071] 1. Heat dissipation sheet 2 slits 2X First Slit 2Y Second Slit 3 side wall 3A One side wall 3B The other side wall

Claims

1. A heat dissipation sheet interposed between a heat-generating element and a heat sink, The heat dissipation sheet has a plurality of slits that open to at least one side, In at least a portion of the slit, the pair of opposing side walls of the slit are spaced apart. When the heat dissipation sheet is compressed in the thickness direction, the opposing side walls of the slits come into contact with each other. The heat dissipation sheet comprises resin and filler, The filler comprises flaky graphite powder, The aforementioned flake-like graphite powder is oriented in the direction in which the slit opens. A heat dissipation sheet in which α, calculated by the following formula (1), is between 0.1 and 5. α=P×A×w / (v×100)...(1) P: Poisson's ratio of the heat dissipation sheet A: Compression ratio (%) of the heat dissipation sheet when pressurized at 100 kPa in the thickness direction. w: Average pitch of multiple slits (mm) v: Average width of multiple slits (mm)

2. The heat dissipation sheet according to claim 1, wherein the compression ratio of the heat dissipation sheet when it is pressurized at 100 kPa in the thickness direction is 5% or more and 50% or less.

3. The heat dissipation sheet according to claim 1, wherein the average width of the plurality of slits is 0.01 mm or more and 0.5 mm or less.

4. The heat dissipation sheet according to claim 1, wherein the ratio of the average depth of the plurality of slits to the average thickness of the heat dissipation sheet is 10% or more and 80% or less.

5. The heat dissipation sheet according to claim 1, wherein the average pitch of the plurality of slits is 0.1 mm or more and 5 mm or less.

6. The heat dissipation sheet according to claim 1, wherein some of the plurality of slits open on both surfaces of the heat dissipation sheet.

7. The heat dissipation sheet according to claim 1, wherein the cross-sectional shape of the slit is rectangular, V-shaped, or U-shaped.

8. The plurality of slits include a first slit and a second slit, The heat dissipation sheet according to claim 1, wherein the first slit and the second slit intersect each other.

Images