Heat conduction sheet and method for manufacturing heat conduction sheet

Abstract

The present invention provides a heat-conducting sheet with excellent adhesion to the heating element and capable of suppressing excessive exudation of adhesive resin. The thermally conductive sheet 1 of the present invention comprises a cured composition of an adhesive resin 2, an anisotropic thermally conductive filler 3, and other thermally conductive fillers 4 besides the anisotropic thermally conductive filler 3, and satisfies the following conditions 1 and 2: [Condition 1]: The adhesion of the heat-conducting sheet 1 is above 80 gf; [Condition 2]: The amount of adhesive resin 2 exuded after a heat-conducting sheet 1 with a size of 25 mm × 25 mm and a thickness of 1 mm is compressed by 40% and left to stand at 125°C for 48 hours is less than 0.20 g.

Description

[Technical Field]

[0001] This technology relates to a heat-conducting sheet and a method for manufacturing the heat-conducting sheet. [Previous Technology]

[0002] With the further improvement of the performance of electronic devices, the density and mounting of semiconductor components are increasing. Along with this, it is important to dissipate the heat generated by the electronic components that constitute the electronic device more efficiently. For example, in semiconductor devices, in order to dissipate heat efficiently, heat-conducting sheets are mounted on heat sinks such as cooling fans and heat sinks. As heat-conducting sheets, those containing (dispersed) inorganic fillers or other filler materials in polysiloxane resin are widely used (see, for example, Patent Documents 1 and 2).

[0003] For heat dissipation components such as heat-conducting sheets, there is a need to further improve thermal conductivity. For example, research is being conducted to increase the filling rate of inorganic fillers incorporated into the matrix such as adhesive resin to achieve high thermal conductivity in the heat-conducting sheet. However, increasing the filling rate of inorganic fillers may compromise the flexibility of the heat-conducting sheet or cause the inorganic fillers to shed powder. Therefore, the improvement of the filling rate of inorganic fillers in heat-conducting sheets is limited.

[0004] Examples of inorganic fillers include alumina, aluminum nitride, and aluminum hydroxide. Furthermore, for the purpose of high thermal conductivity, boron nitride, graphite, or carbon fibers are sometimes filled into the matrix. This is because of the anisotropy of the thermal conductivity of these flake-like particles and carbon fibers. For example, carbon fibers are known to have a thermal conductivity of approximately 600–1200 W / m·K in the fiber direction. Boron nitride, as a flake-like particle, is known to have a thermal conductivity of approximately 110 W / m·K in the plane direction and approximately 2 W / m·K in the direction perpendicular to the plane direction. Thus, the thermal conductivity of carbon fibers or flake-like particles is known to be anisotropic. By aligning the fiber direction of carbon fibers or the surface direction of flake particles with the thickness direction of the heat-conducting sheet, which is the direction of heat transfer, i.e., aligning carbon fibers or flake particles along the thickness direction of the heat-conducting sheet, the thermal conductivity of the heat-conducting sheet can be dramatically improved.

[0005] Furthermore, from the perspective of the aesthetics of the periphery of electronic components using heat-conducting sheets in electronic machines, and the impact on the conductivity of electrical contacts, it is desirable to avoid the scattering of adhesive resin (e.g., polysiloxane) exudates (residues) constituting the heat-conducting sheet, or to prevent them from adhering to electrical contacts. Moreover, the exudation of adhesive resin in the heat-conducting sheet can be caused, for example, by deviations in the mixing ratio of addition-reactive polysiloxane. The exudation of adhesive resin also affects the adhesiveness of the heat-conducting sheet, and thus also affects the quality of the adhesion (temporary fixation) of the heat-conducting sheet to the adhered object (heat-generating element). The technologies described in Patent Documents 1 and 2 are insufficient to provide heat-conducting sheets with excellent adhesion to the heat-generating element and capable of suppressing excessive exudation of adhesive resin. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2012-201106 [Patent Document 2] International Publication No. 2019 / 026745 [Summary of the Invention]

[0007] [The problem the invention aims to solve]

[0008] This technology was proposed in view of the previous situation, providing a heat-conducting sheet with excellent adhesion to the heating element and capable of suppressing excessive exudation of adhesive resin. [Technical Means for Solving the Problem]

[0009] The heat-conducting sheet of this technology contains a hardened composition comprising an adhesive resin, an anisotropic thermally conductive filler, and other thermally conductive fillers besides the anisotropic thermally conductive filler, and satisfies the following conditions 1 and 2: [Condition 1]: The adhesive force of the heat-conducting sheet is 80 gf or more; [Condition 2]: The amount of adhesive resin exuded after the heat-conducting sheet with a size of 25 mm × 25 mm and a thickness of 1 mm is 0.20 g or less when it is compressed by 40% and left to stand at 125°C for 48 hours.

[0010] The manufacturing method of the thermally conductive sheet of this technology includes: Step A, which involves preparing a thermally conductive composition comprising an adhesive resin, an anisotropic thermally conductive filler, and thermally conductive fillers other than the anisotropic thermally conductive filler; Step B, which involves extruding the thermally conductive composition and then curing it to obtain a columnar hardened material; and Step C, which involves cutting the columnar hardened material into a specific thickness along a direction substantially perpendicular to the length direction of the column to obtain a thermally conductive sheet; and the thermally conductive sheet satisfies the following conditions 1 and 2: [Condition 1]: The adhesive strength of the thermally conductive sheet is 80 gf or more; [Condition 2]: The amount of adhesive resin exuded after a thermally conductive sheet with a size of 25 mm × 25 mm and a thickness of 1 mm, under a state of 40% compression and left to stand at 125°C for 48 hours, is 0.20 g or less. [Effects of the Invention]

[0011] This technology can provide a heat-conducting sheet with excellent adhesion to the heating element and the ability to suppress excessive exudation of adhesive resin.

Implementation Method

[0013] In this specification, the average particle size (D50) of anisotropic thermally conductive fillers and other thermally conductive fillers refers to the particle size at which the cumulative value of the cumulative curve of particle size values ​​obtained from the smallest particle size side of the particle size distribution reaches 50%, assuming the overall particle size distribution of the anisotropic thermally conductive fillers or other thermally conductive fillers is set to 100%. Furthermore, the particle size distribution in this specification is a value obtained based on volume. For example, a method for measuring particle size distribution can be described using a laser diffraction type particle size distribution measuring machine.

[0014] <Thermal Conductive Sheet> Figure 1 is a cross-sectional view showing an example of a thermal conductive sheet 1 of the present technology. The thermal conductive sheet 1 contains a cured composition comprising an adhesive resin 2, an anisotropic thermally conductive filler 3, and other thermally conductive fillers 4 besides the anisotropic thermally conductive filler 3. In the thermal conductive sheet 1, the anisotropic thermally conductive filler 3 and other thermally conductive fillers 4 are dispersed in the adhesive resin 2, and the anisotropic thermally conductive filler 3 is aligned along the thickness direction B of the thermal conductive sheet 1.

[0015] Here, the so-called anisotropic thermally conductive filler 3 is aligned along the thickness direction B of the thermally conductive sheet 1. For example, the ratio of anisotropic thermally conductive filler 3 with its long axis aligned along the thickness direction B of the thermally conductive sheet 1 is 50% or more, or it can be 55% or more, or it can be 60% or more, or it can be 65% or more, or it can be 70% or more, or it can be 80% or more, or it can be 90% or more, or it can be 95% or more, or it can be 99% or more.

[0016] The anisotropic thermally conductive packing 3 refers to a thermally conductive packing with an anisotropic shape. Examples of anisotropic thermally conductive packing 3 include thermally conductive packings having a long axis, a short axis, and a thickness (e.g., flake-shaped thermally conductive packing). A flake-shaped thermally conductive packing refers to a thermally conductive packing having a long axis, a short axis, and a thickness, with a high aspect ratio (long axis / thickness), and isotropic thermal conductivity in the direction encompassing the long axis. The short axis of the flake-shaped thermally conductive packing refers to the length of the shortest part of the flake-shaped thermally conductive packing, intersecting the direction through the midpoint of the long axis on the surface encompassing the long axis. The thickness of the flake-shaped thermally conductive packing refers to the average value obtained by measuring the thickness of the flake-shaped thermally conductive packing at 10 points on the surface encompassing the long axis. The aspect ratio of the anisotropic thermally conductive filler 3 is not particularly limited and can be appropriately selected according to the purpose. For example, the aspect ratio of the anisotropic thermally conductive filler 3 can be set in the range of 10 to 100, or in the range of 20 to 50, or in the range of 15 to 40. The major axis, minor axis and thickness of the anisotropic thermally conductive filler 3 can be measured using, for example, a microscope, a scanning electron microscope (SEM), or a particle size analyzer.

[0017] Other thermally conductive fillers 4 are thermally conductive fillers other than anisotropic thermally conductive fillers 3, that is, thermally conductive fillers whose shape is not anisotropic.

[0018] The heat-conducting sheet 1 satisfies the following conditions 1 and 2: [Condition 1]: The adhesive force of the heat-conducting sheet 1 is 80 gf or more. [Condition 2]: The amount of adhesive resin 2 exuded after the heat-conducting sheet 1 with a size of 25 mm × 25 mm and a thickness of 1 mm is 0.20 g or less when it is compressed by 40% and left to stand at 125°C for 48 hours.

[0019] Regarding condition 1, from the viewpoint of the adhesion between the heat-conducting sheet 1 and the heating element as the adhered object, the adhesive force of the heat-conducting sheet 1 is 80 gf or more, or 85 gf or more, or 88 gf or more, or 92 gf or more, or within the range of 80 to 92 gf. The method for measuring the adhesive force of the heat-conducting sheet 1 is the same as the method in the following embodiment.

[0020] Regarding condition 2, considering the usage conditions (environment) of the heat-conducting sheet 1, the amount of adhesive resin 2 exuded after the heat-conducting sheet 1 is compressed to 40% and left to stand at 125°C for 48 hours is 0.20 g or less, or 0.19 g or less, or 0.18 g or less, or 0.17 g or less, or 0.15 g or less. Furthermore, from the viewpoint of satisfying condition 1, the amount of adhesive resin 2 exuded after the heat-conducting sheet 1 is compressed to 40% and left to stand at 125°C for 48 hours is preferably a specific amount or more, which can be 0.15 g or more, or in the range of 0.15 to 0.20 g, or in the range of 0.15 to 0.19 g. The method for measuring the amount of adhesive resin 2 exuded in the heat-conducting sheet 1 is the same as the method in the following examples. For example, a 25 mm × 25 mm, 1 mm thick thermal conductive sheet 1 is compressed by 40% and left to stand at 125°C for 48 hours to measure the amount of adhesive resin 2 that has seeped out.

[0021] Thus, since the heat-conducting sheet 1 satisfies conditions 1 and 2 above, it has excellent adhesion to the heating element and can suppress excessive exudation of the adhesive resin 2. Furthermore, from the viewpoint of high thermal conductivity, the heat-conducting sheet 1 preferably satisfies the following condition 3 in addition to conditions 1 and 2 above: [Condition 3]: The overall thermal conductivity of the heat-conducting sheet 1 is 9.5 W / m·K or higher.

[0022] Regarding condition 3, the overall thermal conductivity of the heat-conducting sheet 1 is preferably 9.5 W / m·K or higher, or it may be 9.9 W / m·K or higher, or it may be 10.5 W / m·K or higher, or it may be 10.6 W / m·K or higher, or it may be 11.3 W / m·K or higher, or it may be 11.4 W / m·K or higher, or it may be 12.3 W / m·K or higher, or it may be 13.1 W / m·K or higher, or it may be in the range of 9.5 to 13.1 W / m·K, or it may be in the range of 9.9 to 13.1 W / m·K. The overall thermal conductivity of the heat-conducting sheet 1 can be measured by the method described in the following examples.

[0023] The effective thermal conductivity in the thickness direction B of the heat-conducting sheet 1 can be 7.5 W / m·K or higher, or 8.0 W / m·K or higher, or 8.3 W / m·K or higher, or 8.5 W / m·K or higher, or 9.1 W / m·K or higher, or 9.2 W / m·K or higher, or 9.3 W / m·K or higher, or 10.5 W / m·K or higher, or 11.1 W / m·K or higher, or in the range of 7.5 to 9.2 W / m·K, or in the range of 7.5 to 11.1 W / m·K. The effective thermal conductivity of the heat-conducting sheet 1 can be measured by the method described in the following examples.

[0024] The thickness of the heat-conducting sheet 1 is not particularly limited and can be appropriately selected according to the purpose. For example, the thickness of the heat-conducting sheet can be set to 0.05 mm or more, or 0.1 mm or more. Furthermore, the upper limit of the thickness of the heat-conducting sheet can be set to 5 mm or less, or 4 mm or less, or 3 mm or less. From the viewpoint of operability of the heat-conducting sheet 1, the thickness of the heat-conducting sheet 1 is preferably set to 0.1 to 4 mm. As for the thickness of the heat-conducting sheet 1, for example, the thickness B of the heat-conducting sheet 1 can be measured at any 5 locations and calculated from their arithmetic mean.

[0025] The thermal resistance value of the heat-conducting sheet 1, measured at 10% compression after being left to stand at 150°C for 1000 hours, is preferably less than 10% compared to the thermal resistance value measured at 10% compression immediately after manufacturing. This change can be less than 8.7%, less than 8.6%, less than 8.2%, less than 8.1%, less than 8.0%, less than 7.8%, less than 7.7%, less than 7.6%, less than 7.4%, less than 7.1%, less than 6.7%, or within the range of 6.7–10%, 6.7–8.7%, or 6.7–8.2%. Within this range, there is a tendency for the thermal resistance value to change less even after prolonged use. The rate of change of thermal resistance of the thermally conductive sheet 1 can be determined by the method described in the following embodiments.

[0026] The thermal resistance value of the heat-conducting sheet 1 measured at a compression ratio of 10% immediately after manufacture is, for example, 1.27℃・cm2 / W or less, or 1.19℃・cm2 / W or less, or 1.16℃・cm2 / W or less, or 1.05℃・cm2 / W or less, or 1.04℃・cm2 / W or less, or 0.92℃・cm2 / W or less, or 0.88℃・cm2 / W or less, or in the range of 0.88 to 1.27℃・cm2 / W.

[0027] The thermal resistance value of the heat-conducting sheet 1 measured after standing at 150°C for 1000 hours at a compression ratio of 10% may be, for example, 1.36°C·cm² / W or less, 1.27°C·cm² / W or less, 1.25°C·cm² / W or less, 1.14°C·cm² / W or less, 1.13°C·cm² / W or less, 1.12°C·cm² / W or less, 1.00°C·cm² / W or less, 0.95°C·cm² / W or less, or in the range of 0.95 to 1.36°C·cm² / W.

[0028] From the viewpoint of flexibility, the compression ratio of the heat-conducting sheet 1 after standing at 150°C for 1000 hours under a load of 3 kgf / cm² is preferably 20% or more, and may also be 21% or more, 22% or more, 23% or more, 25% or more, 26% or more, 28% or more, or in the range of 20-28%, or in the range of 21-28%. Thus, the heat-conducting sheet 1 can maintain good flexibility even after standing at 150°C for 1000 hours. The compression ratio of the heat-conducting sheet 1 under a load of 3 kgf / cm² can be determined by the method described in the following examples.

[0029] Regarding the hardness of the heat-conducting sheet 1, the initial Shore OO hardness (Shore OO type) immediately after manufacturing is preferably in the range of 20 to 90, or it can be in the range of 40 to 70, or it can be in the range of 55 to 60. Furthermore, the initial Shore OO hardness of the heat-conducting sheet 1 after standing at 150°C for 1000 hours is preferably in the range of 40 to 95, or it can be in the range of 65 to 90. By making the hardness of the heat-conducting sheet 1 within this range, the heat-conducting sheet 1 has better conformability to the adherend, and the adherend and the heat-conducting sheet are more likely to be in surface contact, thereby enabling more effective heat conduction. The hardness of the heat-conducting sheet 1 can be measured by the method described in the following examples.

[0030] Preferably, the heat-conducting sheet 1 has a high insulation breakdown voltage. For a thickness of 1 mm, the insulation breakdown voltage can be 7.0 kV or higher, or 7.5 kV or higher, or 8.1 kV or higher, or 8.4 kV or higher, or 8.5 kV or higher, or 8.6 kV or higher, or 8.7 kV or higher, or 9.0 kV or higher, or within the range of 8.1 to 9.0 kV. The insulation breakdown voltage of the heat-conducting sheet 1 can be determined by the method described in the following embodiments.

[0031] Hereinafter, specific examples of the constituent elements of the heat-conducting sheet 1 will be explained.

[0032] <Adhesive Resin> The adhesive resin 2 is used to hold the anisotropic thermally conductive filler 3 and other thermally conductive fillers 4 within the thermally conductive sheet 1. The adhesive resin 2 is selected based on the mechanical strength, heat resistance, electrical properties, and other characteristics required for the thermally conductive sheet 1. The adhesive resin 2 can be selected from thermoplastic resins, thermoplastic elastomers, and thermosetting resins.

[0033] Examples of thermoplastic resins include: polyethylene, polypropylene, ethylene-α-olefin copolymers such as ethylene-propylene copolymers, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymers, polyvinyl alcohol, polyvinyl acetal, polyvinylidene fluoride and polytetrafluoroethylene and other fluorinated polymers, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene- Acrylonitrile copolymers, acrylonitrile-butadiene-styrene copolymer (ABS) resins, polyphenylene ether copolymers (PPE) resins, modified PPE resins, aliphatic polyamines, aromatic polyamines, polyimides, polyamide-imides, polymethacrylic acid, polymethyl methacrylate and other polymethacrylates, polyacrylic acid, polycarbonate, polyphenylene sulfide, polyurethane, polyetherurethane, polyether nitrile, polyether ketone, polyketone, liquid crystal polymers, polysiloxane resins, ionomers, etc.

[0034] Examples of thermoplastic elastomers include: styrene-butadiene block copolymers or their hydrides, styrene-isoprene block copolymers or their hydrides, 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.

[0035] Examples of thermosetting resins include: cross-linked rubber, epoxy resin, phenolic resin, polyimide resin, unsaturated polyester resin, diallyl phthalate resin, etc. Specific examples of cross-linked rubbers include: natural rubber, acrylic rubber, butadiene rubber, isoprene rubber, styrene-butadiene copolymer rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene-propylene copolymer rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, butyl rubber, halogenated butyl rubber, fluororubber, urethane rubber, and polysiloxane rubber.

[0036] As the adhesive resin 2, from the viewpoint of the adhesion between the heating surface of the heating element (e.g., electronic component) and the heat sink surface, a polysiloxane resin is preferred. As the polysiloxane resin, for example, a two-component addition-reaction type polysiloxane resin can be used, comprising a main agent containing a polysiloxane (polyorganosiloxane) having an alkenyl group as the main component and a curing catalyst, and a curing agent having a hydrosilyl group (Si-H group). As the polysiloxane having an alkenyl group, a polyorganosiloxane having at least two alkenyl groups in one molecule can be used. As an example, a polyorganosiloxane having a vinyl group can be used. The curing catalyst is a catalyst used to promote the addition reaction between the alkenyl group in the alkenyl polysiloxane and the hydrosilyl group in the hydrosilyl group curing agent. As a curing catalyst, examples of well-known catalysts used in hydrosilylation reactions include platinum group metal curing catalysts such as platinum, rhodium, palladium, and other platinum group metals, or platinum chloride. As a curing agent containing silyl groups, examples include polyorganosiloxanes (organohydrogenated polysiloxanes having at least two hydrogen atoms directly bonded to silicon atoms in one molecule).

[0037] In particular, from the viewpoint of excellent adhesion to the heating element and ability to suppress excessive exudation of the adhesive resin 2, the heat-conducting sheet 1 preferably uses an adhesive resin 2 that is an addition-reaction type polysiloxane comprising one molecule of an alkenyl polysiloxane and one molecule of an organohydrogenated polysiloxane having hydrogen atoms directly bonded to silicon atoms, and the mixing ratio of the polysiloxane to the organohydrogenated polysiloxane satisfies the following Formula 1. Formula 1: Moles of hydrogen atoms directly bonded to silicon atoms / Moles of alkenyl groups = 0.40 or more / 0.60 or less

[0038] In Formula 1, the mole number of hydrogen atoms directly bonded to silicon atoms refers to the mole number of hydrogen atoms directly bonded to silicon atoms in the organohydrogenated polysiloxane having hydrogen atoms directly bonded to silicon atoms. Also, in Formula 1, the mole number of alkenyl groups refers to the mole number of alkenyl groups in the organosiloxane having alkenyl groups. By making the mole ratio (hereinafter also referred to as "Si-H / alkenyl ratio") of the adhesive resin 2 expressed in Formula 1 0.40 or more, there is a tendency to suppress the exudation of the adhesive resin 2, making it easier for the heat-conducting sheet 1 to satisfy condition 2 above. Furthermore, by making the mole ratio of the adhesive resin 2 expressed in Formula 1 0.60 or less, there is a tendency to increase the adhesion of the heat-conducting sheet 1, making it easier to satisfy condition 1 above. The mole ratio of the adhesive resin 2 expressed in Formula 1 can also be in the range of 0.45 to 0.58.

[0039] The kinematic viscosity of alkenyl polyorganosiloxanes at 23°C can be in the range of 10 to 100,000 mm² / s, or in the range of 500 to 50,000 mm² / s. If the kinematic viscosity of the alkenyl polyorganosiloxane at 23°C is 10 mm² / s or higher, the resulting composition tends to have better storage stability. Furthermore, if the kinematic viscosity of the alkenyl polyorganosiloxane at 23°C is 100,000 mm² / s or lower, the resulting composition tends to have higher extensibility. Moreover, the kinematic viscosity of the alkenyl polyorganosiloxane refers to the value measured using an Ostwald viscometer. Alkenyl polyorganosiloxanes can be used alone, or in combination of two or more different viscosities (kinematic viscosities).

[0040] The content of adhesive resin 2 in the heat-conducting sheet 1 is not particularly limited and can be appropriately selected according to the purpose. For example, the content of adhesive resin 2 in the heat-conducting sheet 1 can be set to 30% by volume or more, or 32% by volume or more, or 34% by volume or more, or 36% by volume or more. Furthermore, the upper limit of the content of adhesive resin 2 in the heat-conducting sheet 1 can be set to 60% by volume or less, or 50% by volume or less, or 40% by volume or less, or 38% by volume or less, or 37% by volume or less. Especially from the perspective of satisfying conditions 1 and 2 above, the content of adhesive resin 2 in the heat-conducting sheet 1 can be set in the range of 30 to 38% by volume, or in the range of 32 to 36% by volume. Adhesive resin 2 can be used alone or in combination with two or more types.

[0041] In the heat-conducting sheet 1, especially relative to the total amount of adhesive resin 2, the content of addition-reactive polysiloxane resin with a molar ratio of 0.40 to 0.60 as expressed in Formula 1 is preferably 80% by volume or more, or 90% by volume or more, or 95% by volume or more, or 99% by volume or more, or substantially 100%.

[0042] <Anisotropic Thermal Conductivity Filler> The material of the anisotropic thermal conductivity filler 3 is not particularly limited. Examples include: boron nitride (BN), mica, alumina, aluminum nitride, silicon carbide, silicon dioxide, zinc oxide, molybdenum disulfide, etc. From the viewpoint of thermal conductivity, boron nitride is preferred. The anisotropic thermal conductivity filler 3 can be used alone or in combination with two or more types.

[0043] Figure 2 is a schematic perspective view of a hexagonal flake boron nitride 3A as an example of anisotropic thermally conductive filler 3. In Figure 2, a represents the long axis of the flake boron nitride 3A, b represents the thickness of the flake boron nitride 3A, and c represents the short axis of the flake boron nitride 3A. As anisotropic thermally conductive filler 3, from the viewpoint of thermal conductivity, it is preferable to use flake boron nitride 3A with a hexagonal crystal shape as shown in Figure 2. In this technology, by using flake thermally conductive filler (e.g., flake boron nitride 3A), which is less expensive than spherical thermally conductive fillers (e.g., spherical boron nitride), as anisotropic thermally conductive filler 3, a thermally conductive sheet 1 that combines low cost and excellent thermal properties (high thermal conductivity) can be obtained.

[0044] The average particle size of the anisotropic thermally conductive filler 3 can be appropriately selected according to the purpose. From the viewpoint of improving the thermal conductivity of the thermally conductive sheet 1, the average particle size of the anisotropic thermally conductive filler 3 in the thermally conductive sheet 1 is 15 μm or more, or 20 μm or more, or 25 μm or more, or 30 μm or more, or 35 μm or more, or 40 μm or more. Furthermore, from the viewpoint of improving the thermal conductivity of the thermally conductive sheet 1, the average particle size of the anisotropic thermally conductive filler 3 in the thermally conductive sheet 1 can be in the range of 30 to 60 μm, or 30 to 50 μm, or 35 to 55 μm, or 35 to 45 μm.

[0045] The content of the anisotropic thermally conductive filler 3 in the heat-conducting sheet 1 can be appropriately selected according to the purpose. From the perspective of condition 2 above, the content of the anisotropic thermally conductive filler 3 in the heat-conducting sheet 1 is preferably more than 20% by volume, and can also be more than 21% by volume, more than 23% by volume, more than 25% by volume, or more than 26% by volume. Furthermore, from the perspective of condition 1 above, the content of the anisotropic thermally conductive filler 3 in the heat-conducting sheet 1 is preferably less than 30% by volume, and can also be less than 28% by volume, or less than 27% by volume. Moreover, the content of the anisotropic thermally conductive filler 3 in the heat-conducting sheet 1 can be in the range of 23 to 27% by volume, or in the range of 23 to 25% by volume, or in the range of 25 to 27% by volume.

[0046] <Other Thermally Conductive Fillers> Other thermally conductive fillers 4 include spherical, powdered, and granular thermally conductive fillers. From the viewpoint of the thermal conductivity of the thermally conductive sheet 1, the material of the other thermally conductive filler 4 is preferably ceramic filler, and specific examples include: alumina (sapphire), aluminum nitride, aluminum hydroxide, zinc oxide, boron nitride, zirconium oxide, silicon carbide, etc. The other thermally conductive filler 4 can be a single type or two or more types (two or more thermally conductive fillers with different average particle sizes).

[0047] As other thermally conductive fillers 4, especially considering the thermal conductivity of the thermally conductive sheet 1 or the specific gravity of the thermally conductive sheet 1, it is preferable to include at least one of aluminum oxide, aluminum nitride, zinc oxide and aluminum hydroxide. Aluminum nitride and aluminum oxide can be used together, or aluminum nitride, aluminum oxide and zinc oxide can be used together.

[0048] From the perspective of the specific gravity of the heat-conducting sheet 1, the average particle size of aluminum nitride can be less than 30 μm, or 0.1–10 μm, or 0.5–5 μm, or 1–3 μm, or 1–2 μm. From the perspective of the specific gravity of the heat-conducting sheet 1, the average particle size of alumina can be 0.1–10 μm, or 0.1–8 μm, or 0.1–7 μm, or 0.1–3 μm. From the perspective of the specific gravity of the heat-conducting sheet 1, the average particle size of zinc oxide can be, for example, 0.01–5 μm, or 0.03–3 μm, or 0.05–2 μm.

[0049] The content of other thermally conductive fillers 4 in the heat-conducting sheet 1 can be appropriately selected according to the purpose. The content of other thermally conductive fillers 4 in the heat-conducting sheet 1 can be set to 10% by volume or more, or 15% by volume or more, or 20% by volume or more, or 25% by volume or more, or 30% by volume or more, or 35% by volume or more. Furthermore, the upper limit of the content of other thermally conductive fillers 4 in the heat-conducting sheet 1 can be set to 50% by volume or less, or 45% by volume or less. Furthermore, the content of other thermally conductive fillers 4 in the heat-conducting sheet 1 can be in the range of 30% to 50% by volume, or 35% to 45% by volume.

[0050] In the case where, for example, aluminum nitride particles, alumina particles, and zinc oxide particles are used as other thermally conductive fillers 4, the content of aluminum nitride particles in the thermally conductive sheet 1 is preferably set to 10-25% by volume (more preferably 17-23% by volume), the content of alumina particles is preferably set to 10-25% by volume (more preferably 17-23% by volume), and the content of zinc oxide particles is preferably set to 0.1-5% by volume (more preferably 0.5-3% by volume).

[0051] From the viewpoint of satisfying conditions 1 and 2 above, the total content of anisotropic thermally conductive filler 3 and other thermally conductive fillers 4 in the heat-conducting sheet 1 is preferably more than 61% by volume, or more than 64% by volume, or more than 66% by volume. Furthermore, from the viewpoint of satisfying conditions 1 and 2 above, the total content of anisotropic thermally conductive filler 3 and other thermally conductive fillers 4 in the heat-conducting sheet 1 is preferably set to 68% by volume or less, or less than 67% by volume, or less than 66% by volume, or less than 65% by volume. From the viewpoint of making the heat-conducting sheet 1 satisfy conditions 1 and 2 above, the total content of anisotropic thermally conductive filler 3 and other thermally conductive fillers 4 in the heat-conducting sheet 1 can be set in the range of 64 to 68% by volume, or in the range of 64 to 66% by volume.

[0052] The thermally conductive sheet 1 may also contain other components besides those mentioned above, to the extent that the effects of this technology are not compromised. Examples of other components include: coupling agents, dispersants, curing accelerators, retardants, adhesion promoters, plasticizers, flame retardants, antioxidants, stabilizers, colorants, solvents, etc. For example, from the viewpoint of further improving the dispersibility of the anisotropic thermally conductive filler 3 and other thermally conductive fillers 4, the thermally conductive sheet 1 may use anisotropic thermally conductive filler 3 treated with a coupling agent and / or other thermally conductive fillers 4 treated with a coupling agent.

[0053] <Manufacturing Method of Heat-Conducting Sheet> The manufacturing method of heat-conducting sheet 1 includes the following steps A, B and C.

[0054] <Step A> In Step A, a thermally conductive composition comprising the adhesive resin 2, the anisotropic thermally conductive filler 3, and the other thermally conductive fillers 4 is prepared by dispersing the anisotropic thermally conductive filler 3 and the other thermally conductive fillers 4 in the adhesive resin 2. The thermally conductive composition can be prepared by uniformly mixing the adhesive resin 2, the anisotropic thermally conductive filler 3, the other thermally conductive fillers 4, and other components as needed, using a known method.

[0055] <Step B> In Step B, the thermally conductive composition prepared in Step A is extruded and then hardened to obtain a columnar hardened product (molded block). There are no particular limitations on the extrusion molding method; it can be appropriately selected from various known extrusion molding methods depending on the viscosity of the thermally conductive composition or the required properties of the thermally conductive sheet 1. In the extrusion molding method, when the thermally conductive composition is extruded from the die, the binder resin 2 in the thermally conductive composition flows, and the anisotropic thermally conductive filler 3 aligns along its flow direction.

[0056] The size and shape of the columnar hardened material obtained in step B can be determined according to the required size of the heat-conducting sheet 1. For example, a cuboid with a longitudinal dimension of 0.5 to 15 cm and a transverse dimension of 0.5 to 15 cm can be used. The length of the cuboid can be determined as needed.

[0057] <Step C> In Step C, the columnar hardened material obtained in Step B is cut to a specific thickness relative to the length direction of the column to obtain a heat-conducting sheet 1. The anisotropic thermally conductive filler 3 is exposed on the surface (cut surface) of the heat-conducting sheet 1 obtained in Step C. There are no particular limitations on the cutting method, and it can be appropriately selected from known slicing devices according to the size and mechanical strength of the columnar hardened material. Regarding the cutting direction of the columnar hardened material, when the forming method is extrusion molding, the anisotropic thermally conductive filler 3 may be aligned along the extrusion direction. Therefore, it is preferable to have a direction of 60 to 120 degrees relative to the extrusion direction, more preferably 70 to 100 degrees, and even more preferably 90 degrees (approximately perpendicular). Apart from the above, there are no particular limitations on the cutting direction of the columnar hardened material, and it can be appropriately selected according to the intended use of the heat-conducting sheet 1.

[0058] Thus, in the method for manufacturing a heat-conducting sheet including steps A, B and C, a heat-conducting sheet 1 that satisfies conditions 1 and 2 above can be obtained.

[0059] The manufacturing method of the heat-conducting sheet 1 is not limited to the above example. For example, a step D of pressing the cut surface may be included after step C. By including the pressing step D, the surface of the heat-conducting sheet 1 obtained in step C can be made smoother, further improving the adhesion to other components. As a pressing method, a pressing device including a flat plate and a pressure head with a flat surface can be used. Alternatively, a pinch roller can be used for pressing. The pressure during pressing can be set to, for example, 0.1 to 100 MPa. In order to further improve the pressing effect and shorten the pressing time, it is preferable to pressurize at a temperature above the glass transition temperature (Tg) of the adhesive resin 2. For example, the pressing temperature can be set to 0 to 180°C, or it can be in the temperature range of room temperature (e.g., 25°C) to 100°C, or it can be 30 to 100°C.

[0060] <Electronic Machine> The heat-conducting sheet 1 is disposed, for example, between a heating element and a heat sink, thereby creating an electronic machine (thermal device) with a structure that releases heat generated by the heating element to the heat sink and is disposed between them. The electronic machine has at least a heating element, a heat sink, and the heat-conducting sheet 1, and may further have other components as needed. Thus, in the electronic machine using the heat-conducting sheet 1, the heat-conducting sheet 1 is sandwiched between the heating element and the heat sink, thereby achieving high thermal conductivity, and the heat-conducting sheet 1 has excellent adhesion to the heating element, which can suppress the excessive exudation of adhesive resin 2 from the heat-conducting sheet 1.

[0061] There are no particular limitations on what constitutes a heat-generating element. Examples include: integrated circuit components such as CPU (Central Processing Unit), GPU (Graphics Processing Unit), DRAM (Dynamic Random Access Memory), and flash memory; transistors; resistors; and other electronic components that generate heat in a circuit. Furthermore, heat-generating elements also include components in communication equipment that receive optical signals, such as optical transceivers.

[0062] There are no particular limitations on the heat sink. Examples include heat sinks or heat spreaders combined with integrated circuit components, transistors, optical transceiver housings, etc. Examples of materials for heat sinks or heat spreaders include copper and aluminum. Besides heat sinks or heat spreaders, any heat sink that conducts heat generated from a heat source and releases it to the outside is acceptable. Examples include heat sinks, coolers, chip mounts, printed circuit boards, cooling fans, Peltier elements, heat pipes, vapor chambers, metal covers, and housings. Heat pipes are hollow structures, such as cylindrical, substantially cylindrical, or flat cylindrical shapes.

[0063] FIG3 is a cross-sectional view showing an example of a semiconductor device using a heat-conducting sheet. For example, as shown in FIG3, a heat-conducting sheet 1 is installed in a semiconductor device 50 built into various electronic devices, sandwiched between a heat-generating element and a heat sink. The semiconductor device 50 shown in FIG3 includes an electronic component 51, a heat spreader 52, and a heat-conducting sheet 1, which is sandwiched between the heat spreader 52 and the electronic component 51. By sandwiching the heat-conducting sheet 1 between the heat spreader 52 and the heat sink 53, it together with the heat spreader 52 constitutes a heat dissipation component for dissipating heat from the electronic component 51. The installation position of the heat-conducting sheet 1 is not limited to between the heat spreader 52 and the electronic component 51, or between the heat spreader 52 and the heat sink 53, and can be appropriately selected according to the configuration of the electronic device or semiconductor device. The heat spreader 52 is, for example, formed into a square plate shape, having a main surface 52a facing the electronic component 51, and a sidewall 52b erected along the outer periphery of the main surface 52a. A heat dissipation plate 52 has a heat conduction sheet 1 disposed on the main surface 52a surrounded by the side wall 52b, and a heat sink 53 disposed on the other side 52c opposite to the main surface 52a, separated by the heat conduction sheet 1.

[0064] The above describes embodiments of the thermally conductive sheet and the method for manufacturing the thermally conductive sheet of the present technology. Various configurations other than those described above may also be adopted. Examples of embodiments are appended below. (Appendix 1) A thermally conductive sheet comprising a hardened composition of a composition including an adhesive resin, an anisotropic thermally conductive filler, and other thermally conductive fillers other than the anisotropic thermally conductive filler, and satisfying the following conditions 1 and 2: [Condition 1]: The adhesive force of the thermally conductive sheet is 80 gf or more; [Condition 2]: The amount of exudation of the adhesive resin of the thermally conductive sheet with a size of 25 mm × 25 mm and a thickness of 1 mm after being compressed by 40% and left to stand at 125°C for 48 hours is 0.20 g or less. (Note 2) In the heat-conducting sheet described in Note 1, the adhesive resin is an addition-reactive polysiloxane, which comprises one molecule of an organosiloxane having an alkenyl group and one molecule of an organohydrogenated polysiloxane having hydrogen atoms directly bonded to silicon atoms. The mixing ratio of the organosiloxane to the organohydrogenated polysiloxane satisfies the following Formula 1: Formula 1: Moles of hydrogen atoms directly bonded to silicon atoms / Moles of alkenyl groups = 0.40 to 0.60. (Note 3) In the heat-conducting sheet described in Note 1 or 2, the content of the adhesive resin is 30% to 38% by volume. (Note 4) In the heat-conducting sheet described in any one of Notes 1 to 3, the content of the anisotropic thermally conductive filler is 22% to 29% by volume. (Note 5) The heat-conducting sheet described in any of Notes 1 to 4, wherein the anisotropic thermally conductive filler is boron nitride, and the other thermally conductive filler is at least one of alumina, aluminum nitride, zinc oxide, and aluminum hydroxide. (Note 6) The heat-conducting sheet described in any of Notes 1 to 5, wherein the anisotropic thermally conductive filler is flake-shaped boron nitride, and the flake-shaped boron nitride is oriented along the thickness direction of the heat-conducting sheet. (Note 7) The heat-conducting sheet described in any of Notes 1 to 6 further satisfies the following condition 3: [Condition 3]: The overall thermal conductivity of the heat-conducting sheet is 9.5 W / m·K or higher. (Note 8) For any of the heat-conducting sheets described in Notes 1 to 7, the change rate of the thermal resistance value measured at 10% compression after standing at 150°C for 1000 hours is less than that measured at 10% compression immediately after manufacturing. (Note 9) For any of the heat-conducting sheets described in Notes 1 to 8, the compression rate measured at 3 kgf / cm² after standing at 150°C for 1000 hours is 20% or more.(Appendix 10) A method for manufacturing a thermally conductive sheet, comprising: Step A, which involves preparing a thermally conductive composition comprising an adhesive resin, an anisotropic thermally conductive filler, and a thermally conductive filler other than the anisotropic thermally conductive filler; Step B, which involves extruding the thermally conductive composition and then curing it to obtain a columnar hardened material; and Step C, which involves cutting the columnar hardened material into a specific thickness along a direction substantially perpendicular to the length direction of the column to obtain a thermally conductive sheet; and the thermally conductive sheet satisfies the following conditions 1 and 2: [Condition 1]: The adhesive strength of the thermally conductive sheet is 80 gf or more; [Condition 2]: The amount of exudation of the adhesive resin of the thermally conductive sheet with a size of 25 mm × 25 mm and a thickness of 1 mm, after being compressed by 40% and left to stand at 125°C for 48 hours, is 0.20 g or less. (Note 11) In the method for manufacturing the heat-conducting sheet as described in Note 10, the adhesive resin is an addition-reactive polysiloxane, which comprises a molecule of an organosiloxane having an alkenyl group and a molecule of an organohydrogenated polysiloxane having hydrogen atoms directly bonded to silicon atoms. The mixing ratio of the organosiloxane to the organohydrogenated polysiloxane satisfies the following Formula 1: Formula 1: The molar number of hydrogen atoms directly bonded to silicon atoms / the molar number of alkenyl groups = 0.40 or more and 0.60 or less. (Note 12) In the method for manufacturing the heat-conducting sheet as described in Note 10 or 11, the following condition 3 is further satisfied: [Condition 3]: The overall thermal conductivity of the heat-conducting sheet is 9.5 W / m·K or more. (Note 13) An electronic machine comprising: a heating element, a heat sink, and a heat-conducting sheet as described in any one of Notes 1 to 9 sandwiched between the heating element and the heat sink. [Example].

[0065] Hereinafter, embodiments of the present technology will be described. However, the present technology is not limited to these embodiments.

[0066] <Example 1> A thermally conductive composition was prepared by uniformly mixing 32% by volume of polysiloxane resin (Si-H / olefin ratio of Formula 1) with a ratio of 0.45, 27% by volume of hexagonal flake boron nitride (D50 of 40 μm, aspect ratio of 20-50), 20% by volume of aluminum nitride (D50 of 1.2 μm), 20% by volume of spherical alumina particles (D50 of 2 μm), and 1% by volume of zinc oxide particles (D50 of 0.1 μm). The thermally conductive composition was extruded into a mold (opening: 50 mm × 50 mm) with a cuboid internal space and heated in an oven at 60°C for 4 hours to form a columnar hardened product (molded block). Furthermore, a release polyethylene terephthalate film was pre-attached to the inner surface of the mold with the release treatment surface as the inside. The obtained columnar hardened material is cut (sliced) into 1 mm thick sheets using a slicer in a direction approximately orthogonal to the length of the column, thereby obtaining a thermally conductive sheet with flake-like boron nitride aligned along the thickness direction of the sheet.

[0067] <Example 2> In Example 2, a thermally conductive composition was prepared by uniformly mixing 32% by volume of polysiloxane resin with a Si-H / olefin ratio of 0.58 (represented by Formula 1), 27% by volume of flake boron nitride (D50 of 40 μm, aspect ratio of 20-50) with a hexagonal crystal shape, 20% by volume of aluminum nitride (D50 of 1.2 μm), 20% by volume of spherical alumina particles (D50 of 2 μm), and 1% by volume of zinc oxide particles (D50 of 0.1 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0068] <Example 3> In Example 3, a thermally conductive composition was prepared by uniformly mixing 34 vol% of polysiloxane resin with a Si-H / olefin ratio of 0.45 (represented by Formula 1), 25 vol% of hexagonal flake boron nitride (D50 of 40 μm, aspect ratio of 15-40), 20 vol% of aluminum nitride (D50 of 1.2 μm), 20 vol% of spherical alumina particles (D50 of 2 μm), and 1 vol% of zinc oxide particles (D50 of 0.1 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0069] <Example 4> In Example 4, a thermally conductive composition was prepared by uniformly mixing 36 vol% of polysiloxane resin with a Si-H / olefin ratio of 0.45 (represented by Formula 1), 23 vol% of hexagonal flake boron nitride (D50 of 40 μm, aspect ratio of 15-40), 20 vol% of aluminum nitride (D50 of 1.2 μm), 20 vol% of spherical alumina particles (D50 of 2 μm), and 1 vol% of zinc oxide particles (D50 of 0.1 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0070] <Example 5> In Example 5, a thermally conductive composition was prepared by using hexagonal flake boron nitride (D50 of 50 μm and aspect ratio of 25-60) instead of hexagonal flake boron nitride (D50 of 40 μm and aspect ratio of 20-50). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0071] <Example 6> In Example 6, a thermally conductive composition was prepared by using hexagonal flake boron nitride (D50 of 50 μm and aspect ratio of 25-60) instead of hexagonal flake boron nitride (D50 of 40 μm and aspect ratio of 20-50). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 2.

[0072] <Example 7> In Example 7, a thermally conductive composition was prepared by using hexagonal flake boron nitride (D50 of 50 μm and aspect ratio of 20 to 50) instead of hexagonal flake boron nitride (D50 of 40 μm and aspect ratio of 15 to 40). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 3.

[0073] <Example 8> In Example 8, a thermally conductive composition was prepared by using hexagonal flake boron nitride (D50 of 50 μm and aspect ratio of 20 to 50) instead of hexagonal flake boron nitride (D50 of 40 μm and aspect ratio of 15 to 40). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 4.

[0074] <Example 9> In Example 9, a thermally conductive composition was prepared by uniformly mixing 33% by volume of polysiloxane resin with a Si-H / olefin ratio of 0.45 (represented by Formula 1), 27% by volume of flake boron nitride (D50 of 40 μm, aspect ratio of 15-40) with a hexagonal crystal shape, 20% by volume of aluminum nitride (D50 of 1.2 μm), and 20% by volume of spherical alumina particles (D50 of 2 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0075] <Example 10> In Example 10, a thermally conductive composition was prepared by uniformly mixing 33% by volume of polysiloxane resin with a Si-H / olefin ratio of 0.45 (represented by Formula 1), 27% by volume of flake boron nitride (D50 of 40 μm, aspect ratio of 15-40) with a hexagonal crystal shape, 30% by volume of aluminum nitride (D50 of 1.2 μm), and 10% by volume of spherical alumina particles (D50 of 2 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0076] <Comparative Example 1> In Comparative Example 1, a thermally conductive composition was prepared by uniformly mixing 32% by volume of polysiloxane resin with a Si-H / olefin ratio of 0.33 (represented by Formula 1), 27% by volume of flake boron nitride (D50 of 40 μm and aspect ratio of 10-30) with a hexagonal crystal shape, 20% by volume of aluminum nitride (D50 of 1.2 μm), 20% by volume of spherical alumina particles (D50 of 2 μm), and 1% by volume of zinc oxide particles (D50 of 0.1 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0077] <Comparative Example 2> In Comparative Example 2, a thermally conductive composition was prepared by uniformly mixing 32% by volume of polysiloxane resin with a Si-H / olefin ratio of 0.84 (represented by Formula 1), 27% by volume of flake boron nitride (D50 of 40 μm, aspect ratio of 10-30) with a hexagonal crystal shape, 20% by volume of aluminum nitride (D50 of 1.2 μm), 20% by volume of spherical alumina particles (D50 of 2 μm), and 1% by volume of zinc oxide particles (D50 of 0.1 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0078] <Comparative Example 3> In Comparative Example 3, a thermally conductive composition was prepared by uniformly mixing 29 vol% of polysiloxane resin with a Si-H / olefin ratio of 0.45 (represented by Formula 1), 30 vol% of hexagonal flake boron nitride (D50 of 40 μm, aspect ratio of 10-30), 20 vol% of aluminum nitride (D50 of 1.2 μm), 20 vol% of spherical alumina particles (D50 of 2 μm), and 1 vol% of zinc oxide particles (D50 of 0.1 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0079] <Comparative Example 4> In Comparative Example 4, a thermally conductive composition was prepared by uniformly mixing 39 vol% of polysiloxane resin with a Si-H / olefin ratio of 0.45 (represented by Formula 1), 20 vol% of hexagonal flake boron nitride (D50 of 40 μm, aspect ratio of 10-30), 20 vol% of aluminum nitride (D50 of 1.2 μm), 20 vol% of spherical alumina particles (D50 of 2 μm), and 1 vol% of zinc oxide particles (D50 of 0.1 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0080] <Comparative Example 5> In Comparative Example 5, a thermally conductive composition was prepared by uniformly mixing 39 vol% of polysiloxane resin with a Si-H / olefin ratio of 0.45 (represented by Formula 1), 20 vol% of hexagonal flake boron nitride (D50 of 40 μm, aspect ratio of 10-30), 10 vol% of aluminum nitride (D50 of 1.2 μm), 30 vol% of spherical alumina particles (D50 of 2 μm), and 1 vol% of zinc oxide particles (D50 of 0.1 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0081] <Comparative Example 6> In Comparative Example 6, a thermally conductive composition was prepared by uniformly mixing 39 vol% of polysiloxane resin with a Si-H / olefin ratio of 0.45 (represented by Formula 1), 20 vol% of hexagonal flake boron nitride (D50 of 40 μm, aspect ratio of 10-30), 30 vol% of aluminum nitride (D50 of 1.2 μm), 10 vol% of spherical alumina particles (D50 of 2 μm), and 1 vol% of zinc oxide particles (D50 of 0.1 μm). Otherwise, a thermally conductive sheet was obtained by the same method as in Example 1.

[0082] <Comparative Example 7> In Comparative Example 7, a thermally conductive composition was prepared by using hexagonal flake boron nitride (D50 of 50 μm and aspect ratio of 15 to 40) instead of hexagonal flake boron nitride (D50 of 40 μm and aspect ratio of 10 to 30). Otherwise, a thermally conductive sheet was obtained by the same method as in Comparative Example 1.

[0083] <Comparative Example 8> In Comparative Example 8, a thermally conductive composition was prepared by using hexagonal flake boron nitride (D50 of 50 μm and aspect ratio of 15 to 40) instead of hexagonal flake boron nitride (D50 of 40 μm and aspect ratio of 10 to 30). Otherwise, a thermally conductive sheet was obtained by the same method as in Comparative Example 2.

[0084] <Comparative Example 9> In Comparative Example 9, a thermally conductive composition was prepared by using hexagonal flake boron nitride (D50 of 50 μm and aspect ratio of 15 to 40) instead of hexagonal flake boron nitride (D50 of 40 μm and aspect ratio of 10 to 30). Otherwise, a thermally conductive sheet was obtained by the same method as in Comparative Example 3.

[0085] <Comparative Example 10> In Comparative Example 10, a thermally conductive composition was prepared by using hexagonal flake boron nitride (D50 of 50 μm and aspect ratio of 15 to 40) instead of hexagonal flake boron nitride (D50 of 40 μm and aspect ratio of 10 to 30). Otherwise, a thermally conductive sheet was obtained by the same method as in Comparative Example 4.

[0086] <Comparative Example 11> In Comparative Example 11, a thermally conductive composition was prepared by using hexagonal flake boron nitride (D50 of 50 μm and aspect ratio of 15 to 40) instead of hexagonal flake boron nitride (D50 of 40 μm and aspect ratio of 10 to 30). Otherwise, a thermally conductive sheet was obtained by the same method as in Comparative Example 5.

[0087] <Comparative Example 12> In Comparative Example 12, a thermally conductive composition was prepared by using hexagonal flake boron nitride (D50 of 50 μm and aspect ratio of 15 to 40) instead of hexagonal flake boron nitride (D50 of 40 μm and aspect ratio of 10 to 30). Otherwise, a thermally conductive sheet was obtained by the same method as in Comparative Example 6.

[0088] <Oil Leakage> Figure 4(A) is a cross-sectional view showing the state in which the heat-conducting sheet 1 is held by the compression clamps (upper clamp 61 and lower clamp 62), and Figure 4(B) is a top view showing the state in which the heat-conducting sheet 1 is placed on the lower clamp 62. Figure 5(A) is a top view showing the state in which the heat-conducting sheet 1 is held by the compression clamps (upper clamp 61 and lower clamp 62), and Figure 5(B) is a side view showing the state in which the heat-conducting sheet 1 is held by the compression clamps (upper clamp 61 and lower clamp 62).

[0089] The heat-conducting sheets obtained in the various embodiments and comparative examples were processed into heat-conducting sheets 10 with a size of 25 mm × 25 mm, and wire mesh 60 with a size of 40 mm × 75 mm (product name: PET wire mesh sheet, model: TN180, manufactured by Sanbote Company) were processed, and their respective weights were measured. The weight (g) of the heat-conducting sheets 10 (25 mm × 25 mm × 1 mm thick) prepared in the various embodiments and comparative examples is shown in Tables 1 and 2. An upper clamp 61 and a lower clamp 62 were prepared, and three sheets of filter paper 63 (model: qualitative filter paper NO.101, diameter 90 mm) were stacked and placed on the lower clamp 62. Two sheets of wire mesh 60 were stacked on the filter paper 63, and the heat-conducting sheet 10 and the spacer 64 were placed on the wire mesh 60. The interval between the heat-conducting sheet 10 and the spacer 64 was set to about 1 cm as shown in Figure 4(B). Two pieces of wire mesh 65 are stacked on top of the heat-conducting sheet 10 and the spacer 64. Three pieces of filter paper 66 are stacked on top of the wire mesh 65. An upper clamp 61 is placed on top of the filter paper 66, and the nuts 67 at four points of the upper clamp 61 are tightened evenly until the heat-conducting sheet 10 is compressed by 40%. The heat-conducting sheet 10, compressed by 40%, clamped between the upper clamp 61 and the lower clamp 62, is placed in an oven heated to 125°C. After 48 hours in the oven, the heat-conducting sheet 10 clamped between the upper clamp 61 and the lower clamp 62 is removed and placed at room temperature until cooled. The nuts 67 at four points of the upper clamp 61 are loosened, and the heat-conducting sheet 10 and the wire meshes 60 and 65 (a total of four pieces) are weighed as a whole in this state. The amount (g) of polysiloxane resin (adhesive resin) exuded from the heat-conducting sheet 10 was determined from the measured weight. The results are shown in Tables 1 and 2.

[0090] <Overall Thermal Conductivity> Regarding the overall thermal conductivity, the thermal resistance of each thermally conductive sheet was measured according to the method of ASTM-D5470. The horizontal axis was set to the thickness (mm) of the thermally conductive sheet at the time of measurement, and the vertical axis was set to the thermal resistance (°C・cm² / W). A curve was plotted, and the overall thermal conductivity (W / m・K) of the thermally conductive sheet was calculated from the slope of the curve. Regarding the thermal resistance of the thermally conductive sheet, three types of thermally conductive sheets with the same composition but different thicknesses as those in the examples and comparative examples were prepared, and the thermal resistance of each thickness was measured. The results are shown in Tables 1 and 2.

[0091] <Effective Thermal Conductivity> The effective thermal conductivity (W / m・K) of the thermally conductive sheet was measured using a thermal resistance measuring device according to ASTM-D5470, with a load of 0.3 to 3 kgf / cm2 applied to a 1 mm thick thermally conductive sheet. The highest value of thermal conductivity was selected. The results are shown in Tables 1 and 2.

[0092] <Adhesion> The obtained thermally conductive sheet was sandwiched between peeled PET films and subjected to a pressure treatment of 0.5 MPa for 30 seconds. Subsequently, the PET film was peeled off from the thermally conductive sheet, and the thermally conductive sheet was sandwiched between another peeled PET film and left for 7 days. After 7 days, the peeled PET film was removed from the thermally conductive sheet, and immediately (within 3 minutes) an adhesion tester (manufactured by MALCOM) was used to determine the adhesion (gf) of the surface of the thermally conductive sheet when a 5.1 mm diameter probe was pressed into the thermally conductive sheet at 2 mm / s for 50 μm and pulled out at 10 mm / s. The results are shown in Tables 1 and 2.

[0093] <Fixed to Aluminum Plate> Figure 6 is a diagram illustrating the evaluation method for whether the heat-conducting sheet slips when it is placed on an aluminum plate and offset by 90°. As shown in Figure 6(A), after the heat-conducting sheet 20 is placed on a horizontally placed aluminum plate 70, as shown in Figure 6(B), the aluminum plate 70 is tilted at 90° while holding the heat-conducting sheet 20, and the slippage of the heat-conducting sheet 20 is evaluated. The results are shown in Tables 1 and 2. In Tables 1 and 2, ○ indicates that the heat-conducting sheet 20 did not slip (OK). Also, in Tables 1 and 2, × indicates that the heat-conducting sheet 20 slipped (NG).

[0094] <Change in Thermal Resistance> The change in thermal resistance (°C・cm² / W) of the thermally conductive sheet was determined as follows: First, the thermal resistance of the thermally conductive sheet after manufacturing was measured when it was compressed by 10% relative to its initial thickness (initial thermal resistance at 10% compression: first thermal resistance). After the thermally conductive sheet was left to stand at 150°C for 1000 hours, the thermal resistance was measured when it was compressed by 10% relative to the thickness after standing at 150°C for 1000 hours (thermal resistance at 150°C × 1000 hours after 10% compression: second thermal resistance). Based on these first and second thermal resistance values, the rate of change (%) of the thermal resistance of the thermally conductive sheet before and after standing at 150°C for 1000 hours with 10% compression was determined. The results are shown in Tables 1 and 2.

[0095] <Compression Ratio under a Load of 3 kgf / cm2> After the obtained thermally conductive sheet was left to stand at 150°C for 1000 hours, a load of 3 kgf / cm2 was applied, and the compression ratio (%) of the thermally conductive sheet was measured. The results are shown in Tables 1 and 2.

[0096] <Shore Hardness Variation> The Shore Type OO hardness of the thermally conductive sheet was determined according to the ASTM-D2240 test method. Specifically, the Shore hardness (initial Shore hardness) of 10 sheets of 1 mm thick thermally conductive sheet immediately after manufacturing was measured, as well as the Shore hardness of 10 sheets of 1 mm thick thermally conductive sheet after being left to stand at 150°C for 1000 hours was measured. The Shore hardness of the thermally conductive sheet was the average of the results obtained from 5 measurements on each side, for a total of 10 measurements on both sides. The results are shown in Tables 1 and 2.

[0097] <Insulation Breakdown Voltage> The insulation breakdown voltage of the heat-conducting sheet was measured using an ultra-high voltage withstand voltage tester (manufactured by the Institute of Measurement Technology, 7473) at a sheet thickness of 1 mm, a voltage ramp rate of 0.05 kV / s, and room temperature. The voltage at which insulation breakdown occurs was taken as the insulation breakdown voltage (kV). The results are shown in Tables 1 and 2.

[0098] [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Si-H / Alkenyl Ratio (mol ratio) 0.45 0.58 0.45 0.45 0.45 0.58 0.45 0.45 0.45 0.45 Polysiloxane [Vol%] 32 32 34 36 32 32 34 36 33 33 Alumina (D50 = 2 μm) [Vol%] 20 20 20 20 20 20 20 20 20 10 Aluminum nitride (D50 = 1.2 μm) [Vol%] 20 20 20 20 20 20 20 20 20 30 Zinc oxide (D50 = 0.1 μm) [Vol%] 1 1 1 1 1 1 1 1 - - Boron nitride (D50 = 40 μm) [Vol%] 27 27 25 twenty three - - - - 27 27 Boron nitride (D50 = 50 μm) [Vol%] - - - - 27 27 25 twenty three - - Total packing volume [Vol%] 68 68 66 64 68 68 66 64 67 67 Weight [g] of heat-conducting sheet (25 mm × 25 mm × 1 mm thickness) 1.47 1.47 1.46 1.45 1.47 1.47 1.46 1.45 1.47 1.45 Oil seepage rate [g] 0.17 0.15 0.18 0.19 0.16 0.14 0.18 0.18 0.16 0.17 Overall thermal conductivity [W / m・K] 11.3 11.4 10.5 9.9 12.3 13.1 11.3 10.6 11.3 11.4 Effective thermal conductivity [W / m·K] 1 mm thickness 9.1 9.2 8.3 7.5 10.5 11.1 9.2 8.5 9.2 9.3 Adhesive force [gf] 85 80 88 92 84 80 88 90 87 83 Aluminum plate adhesion test ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Initial thermal resistance at 10% compression [℃・cm 2 / W] 1.05 1.05 1.19 1.27 0.92 0.88 1.04 1.16 1.05 1.05 Thermal resistance value after 10% compression at 150℃ for 1000 hours [℃・cm 2 / W] 1.13 1.13 1.27 1.36 1.00 0.95 1.12 1.25 1.13 1.14 Rate of change of thermal resistance at 10% compression [%) (After 150℃×1000H) 7.6 7.6 6.7 7.1 8.7 8.0 7.7 7.8 7.6 8.6 Load 3 kgf / cm 2 Compression rate [%] (After 150℃×1000H) twenty three twenty two 25 28 twenty one twenty three 26 28 twenty three twenty one Initial Shore hardness (Shore OO) 53 55 51 48 57 52 51 49 53 58 Shore hardness after 150℃×1000H (Shore OO) 74 77 71 68 80 75 70 69 75 81 Insulation failure voltage [kV / mm] 8.5 8.5 8.6 9.0 8.1 8.1 8.4 8.7 8.5 8.5

[0099] [Table 2] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Comparative Example 11 Comparative Example 12 Si-H / Alkenyl Ratio (mol ratio) 0.33 0.84 0.45 0.45 0.45 0.45 0.33 0.84 0.45 0.45 0.45 0.45 Polysiloxane [Vol%] 32 32 29 39 39 39 32 32 29 39 39 39 Alumina (D50 = 2 μm) [Vol%] 20 20 20 20 30 10 20 20 20 20 30 10 Aluminum nitride (D50 = 1.2 μm) [Vol%] 20 20 20 20 10 30 20 20 20 20 10 30 Zinc oxide (D50 = 0.1 μm) [Vol%] 1 1 1 1 1 1 1 1 1 1 1 1 Boron nitride (D50 = 40 μm) [Vol%] 27 27 30 20 20 20 - - - - - - Boron nitride (D50 = 50 μm) [Vol%] - - - - - - 27 27 30 20 20 20 Total packing volume [Vol%] 68 68 71 61 61 61 68 68 71 61 61 61 Weight [g] of heat-conducting sheet (25 mm × 25 mm × 1 mm thickness) 1.47 1.47 1.49 1.44 1.46 1.42 1.47 1.47 1.49 1.44 1.46 1.42 Oil seepage rate [g] 0.25 0.16 0.15 0.55 0.54 0.56 0.24 0.17 0.15 0.55 0.55 0.57 Overall thermal conductivity [W / m・K] 10.5 11.1 10.7 7.7 7.2 7.8 11.1 11.6 11.5 7.8 7.4 7.9 Effective thermal conductivity [W / m·K] 1 mm thickness 8.5 9.2 8.9 6.1 5.7 6.5 9.1 9.7 9.4 6.4 6.1 6.8 Adhesive force [gf] 102 76 60 98 95 96 99 74 58 97 95 93 Aluminum plate adhesion test ○ × × ○ ○ ○ ○ × × ○ ○ ○ Initial thermal resistance at 10% compression [℃・cm 2 / W] 1.07 1.03 1.12 1.37 1.41 1.35 0.95 0.87 1.04 1.27 1.28 1.25 Thermal resistance value after 10% compression at 150℃ for 1000 hours [℃・cm 2 / W] 1.15 1.10 1.25 1.48 1.51 1.46 1.03 0.94 1.19 1.43 1.45 1.42 Rate of change of thermal resistance at 10% compression [%) (After 150℃×1000H) 7.5 6.8 11.6 8.0 7.1 8.1 8.4 8.0 14.4 12.6 13.3 13.6 Load 3 kgf / cm 2 Compression rate [%] (After 150℃×1000H) 25 18 15 32 33 30 twenty two 19 14 31 32 31 Initial Shore hardness (Shore OO) 49 61 69 44 44 47 55 63 71 46 46 47 Shore hardness after 150℃×1000H (Shore OO) 70 83 89 65 65 68 78 85 92 67 67 68 Insulation failure voltage [kV / mm] 8.4 8.4 7.5 9.3 9.3 9.3 8.1 8.1 6.9 9.0 9.0 9.0

[0100] It is known that the heat-conducting sheets obtained in Examples 1 to 10 contain a hardened composition comprising an adhesive resin, anisotropic thermally conductive filler, and other thermally conductive fillers, and satisfy conditions 1 and 2 above, exhibiting excellent adhesion to the heating element and suppressing excessive exudation of the adhesive resin. Furthermore, it is known that the heat-conducting sheets obtained in Examples 1 to 10 satisfy condition 3 above, exhibiting good thermal conductivity.

[0101] It is known that the thermal resistance value of the heat-conducting sheets obtained in Examples 1 to 10, after being left to stand at 150°C for 1000 hours, measured at a compression ratio of 10%, is less than 10% compared to the thermal resistance value measured immediately after manufacturing at a compression ratio of 10%. Furthermore, it is known that the compression ratio of the heat-conducting sheets obtained in Examples 1 to 10, after being left to stand at 150°C for 1000 hours, measured under a load of 3 kgf / cm², is 20% or more.

[0102] It can be seen that the heat-conducting sheets obtained in Comparative Examples 1, 4 to 7, and 10 to 12 do not meet the above condition 2 and cannot suppress excessive exudation of adhesive resin.

[0103] It can be seen that the heat-conducting sheets obtained in Comparative Examples 2, 3, 8 and 9 do not meet the above condition 1 and have poor fixation on the aluminum plate.

[0104] It can be seen that the thermal resistance values ​​of the heat-conducting sheets obtained in Comparative Examples 3, 9 to 12, after being left to stand at 150°C for 1000 hours and measured at a compression ratio of 10%, do not show a change of less than 10% compared to the thermal resistance values ​​measured immediately after manufacturing at a compression ratio of 10%. Furthermore, it can be seen that the compression ratios of the heat-conducting sheets obtained in Comparative Examples 2, 3, 8, and 9, after being left to stand at 150°C for 1000 hours and measured under a load of 3 kgf / cm², do not reach 20%. [Simplified Explanation of the Diagram]

[0012] Figure 1 is a cross-sectional view showing an example of a heat-conducting sheet. Figure 2 is a perspective view showing, in a schematic manner, a hexagonal flake boron nitride as an example of an anisotropic heat-conducting filler. Figure 3 is a cross-sectional view showing an example of a semiconductor device using a heat-conducting sheet. Figure 4(A) is a cross-sectional view showing the heat-conducting sheet held in place by a compression clamp, and Figure 4(B) is a top view showing the heat-conducting sheet placed on a lower clamp. Figure 5(A) is a top view showing the heat-conducting sheet held in place by a compression clamp, and Figure 5(B) is a side view showing the heat-conducting sheet held in place by a compression clamp. Figures 6(A) and (B) are diagrams illustrating an evaluation method for whether a heat-conducting sheet slips when it is placed on an aluminum plate and rotated 90°.

Claims

1. A heat-conducting sheet comprising a cured composition of an adhesive resin, an anisotropic thermally conductive filler, and other thermally conductive fillers besides the anisotropic thermally conductive filler, and satisfying the following conditions 1 and 2: [Condition 1]: The adhesive strength of the heat-conducting sheet is 80 gf or more and 92 gf or less; [Condition 2]: The amount of exudation of the adhesive resin after the heat-conducting sheet with a size of 25 mm × 25 mm and a thickness of 1 mm is 0.20 g or less after being compressed by 40% and left to stand at 125°C for 48 hours; wherein the adhesive resin is an addition-reactive polysiloxane, and the addition-reactive polysiloxane comprises a molecule of an organosiloxane having an alkenyl group and a molecule of an organohydrogenated polysiloxane having hydrogen atoms directly bonded to silicon atoms. The mixing ratio of the above-mentioned polyorganosiloxane and the above-mentioned organic hydrogenated polysiloxane satisfies the following Formula 1: Formula 1: the molar number of hydrogen atoms directly bonded to silicon atoms / the molar number of alkenyl groups = 0.40 to 0.60; the content of the above-mentioned adhesive resin is 30% to 38% by volume; the above-mentioned method for measuring adhesion involves sandwiching the obtained thermally conductive sheet between peeled PET films, applying pressure at 0.5 MPa for 30 seconds, then peeling the PET film off the thermally conductive sheet, and sandwiching the thermally conductive sheet again between another peeled PET film, and leaving it for 7 days; after leaving it for 7 days, immediately (within 3 minutes) after peeling the peeled PET film off the thermally conductive sheet, using an adhesion measuring machine, the adhesion (gf) on the surface of the thermally conductive sheet is determined when a 5.1 mm diameter probe is pressed into the thermally conductive sheet at 2 mm / s for 50 μm and pulled out at 10 mm / s.

2. The heat-conducting sheet as requested in item 1, wherein the content of the above-mentioned anisotropic heat-conducting filler is more than 22% by volume and less than 29% by volume.

3. The heat-conducting sheet as claimed in claim 1 or 2, wherein the anisotropic heat-conducting filler is boron nitride, and the other heat-conducting filler is at least one of aluminum oxide, aluminum nitride, zinc oxide, and aluminum hydroxide.

4. The heat-conducting sheet as claimed in claim 1 or 2, wherein the anisotropic heat-conducting filler is flake-shaped boron nitride, and the flake-shaped boron nitride is oriented along the thickness direction of the heat-conducting sheet.

5. The heat-conducting sheet of request item 1 or 2 further satisfies the following condition 3: [Condition 3]: The overall thermal conductivity of the heat-conducting sheet is 9.5 W / m・K or higher.

6. For the thermally conductive sheet as requested in item 1 or 2, the change rate of the thermal resistance value measured at 10% compression after standing at 150°C for 1000 hours is less than 10% compared to the thermal resistance value measured at 10% compression immediately after manufacturing.

7. For the heat-conducting sheet of request item 1 or 2, the compression ratio measured after standing at 150°C for 1000 hours under a load of 3 kgf / cm2 is 20% or more.

8. A method for manufacturing a heat-conducting sheet, comprising: Step A involves preparing a thermally conductive composition comprising an adhesive resin, an anisotropic thermally conductive filler, and a thermally conductive filler other than the aforementioned anisotropic thermally conductive filler; Step B involves extruding the aforementioned thermally conductive composition and then curing it to obtain a columnar hardened material; and Step C involves cutting the aforementioned columnar hardened material into a specific thickness along a direction substantially perpendicular to the length of the column to obtain a thermally conductive sheet; and the aforementioned thermally conductive sheet satisfies the following conditions 1 and 2: [Condition 1]: The adhesive strength of the aforementioned thermally conductive sheet is 80 gf or more and 92 gf or less; [Condition 2]: The amount of exudation of the aforementioned adhesive resin after the aforementioned thermally conductive sheet with a size of 25 mm × 25 mm and a thickness of 1 mm, under a state of 40% compression and standing at 125°C for 48 hours, is 0.20 g or less; The aforementioned adhesive resin is an addition-reactive polysiloxane resin. The aforementioned addition-reaction type polysiloxane comprises one molecule of an organosiloxane having an alkenyl group and one molecule of an organohydrogenated polysiloxane having hydrogen atoms directly bonded to silicon atoms. The mixing ratio of the aforementioned organosiloxane to the aforementioned organohydrogenated polysiloxane satisfies the following Formula 1: Formula 1: Moles of hydrogen atoms directly bonded to silicon atoms / Moles of alkenyl groups = 0.40 to 0.60; The content of the aforementioned adhesive resin is 30% to 38% by volume; The aforementioned method for measuring adhesion involves sandwiching the obtained thermally conductive sheet between peeled PET films, at a 0.5... After applying pressure of MPa for 30 seconds, the PET film is peeled off from the heat-conducting sheet. The heat-conducting sheet is then sandwiched between another peeled PET film and left for 7 days. After 7 days, the PET film is peeled off from the heat-conducting sheet. Immediately (within 3 minutes), an adhesion tester is used to determine the adhesion (gf) on the surface of the heat-conducting sheet when a 5.1 mm diameter probe is pressed into the heat-conducting sheet at 2 mm / s for 50 μm and pulled out at 10 mm / s.

9. The method for manufacturing the heat-conducting sheet as claimed in claim 8 further satisfies the following condition 3: [Condition 3]: The overall thermal conductivity of the heat-conducting sheet is 9.5 W / m・K or higher.

10. An electronic machine comprising: a heating element, a heat sink, and a heat-conducting sheet as claimed in claim 1 or 2 sandwiched between the heating element and the heat sink.

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