WO2022181206A1 - Heat-conducting sheet, heat-conducting sheet production method, and electronic device - Google Patents

Abstract

The present invention provides a heat-conducting sheet that exhibits excellent adhesion to an electronic component and with which offset from an attachment position can be suppressed.　A heat-conducting sheet 1 is a cured product of a composition including at least a polymer matrix component 2 and a fibrous heat-conductive filler 3. Under the following condition 1, offset in the length direction is 2.5mm or less based on a state in which the heat-conducting sheet 1 is held between copper plates 10. Condition 1: A heat cycle (test temperature transition time: within 3 min, maintained temperature time after reaching test temperature: 30 min) between -40°C and 100°C is performed for 672 hours in a state in which a heat-conducting sheet sample 11 cut into a 20mm×5mm strip is held between vertically disposed copper plates 10 with the length direction thereof aligning with the vertical direction and one length-direction side thereof coinciding with one side of the copper plates 10, and the thickness of said sample is compressed by 10%.

Description

THERMALLY CONDUCTIVE SHEET, METHOD FOR MANUFACTURING THERMALLY CONDUCTIVE SHEET, ELECTRONIC DEVICE

This technology relates to a thermally conductive sheet, a method for manufacturing a thermally conductive sheet, and an electronic device using the same. This application claims priority based on Japanese Patent Application No. 2021-028005 filed on February 24, 2021 in Japan, and this application is hereby incorporated by reference. Incorporated.

Conventionally, semiconductor devices installed in various electrical devices such as personal computers and other equipment generate heat when driven, and accumulation of the generated heat can adversely affect the operation of semiconductor devices and peripheral devices. , various cooling methods are used.

Cooling methods for devices with semiconductor elements include attaching a fan to the device to cool the air inside the device housing, attaching heat sinks such as heat sinks and heat sinks to the semiconductor device, and immersing the device in a fluorine-based inert liquid. There are known methods for When a heat sink is attached to a semiconductor element for cooling, a liquid or paste thermal conductive material such as thermal grease is provided between the semiconductor element and the heat sink in order to efficiently dissipate the heat of the semiconductor element.

JP 2012-023335 A JP 2015-029076 A JP 2015-029075 A

Here, electronic components such as the CPU of personal computers tend to increase their heat dissipation amount year by year as their speed and performance increase. On the contrary, however, the chip size of processors and the like has become equal to or smaller than conventional ones due to advances in fine silicon circuit technology, and the heat flux per unit area has increased. Therefore, in order to avoid problems caused by the temperature rise, it is required to efficiently dissipate and cool the electronic parts such as the CPU.

In addition, as electronic devices become slimmer (miniaturized), there are designs in which electronic components that generate heat, such as IC chips, are installed vertically instead of horizontally.

Here, when a liquid or paste heat-conducting material is used for an electronic component oriented in a substantially vertical direction, the heat-conducting material flows out from between the electronic component and the heat-dissipating member due to the thermal cycle of heat generation and cooling of the electronic component. A so-called pump-out phenomenon can occur. As a result, air enters between the electronic component and the heat radiating member, increasing the thermal resistance, which may adversely affect the driving of the electronic component and peripheral devices. In addition, if a curable liquid heat conductive agent is used, it will not be able to follow deformation such as warpage of the electronic component due to the pump-out phenomenon associated with the thermal cycle of the electronic component. Adverse effects on the drive and peripheral equipment may occur.

To address such problems, a thermally conductive sheet, which is formed by molding a thermally conductive resin composition into a sheet, is used. When a thermal conductive sheet is used in an electronic component with the surface direction facing the vertical direction, the electronic component must repeat heat generation and cooling in order for the thermal conductive sheet to maintain its heat dissipation characteristics as the electronic device continues to be used. In this way, it is necessary to prevent misalignment and falling from the predetermined sticking position. In addition, the thermally conductive sheet is required to have resilience to follow the deformation of the electronic parts due to repeated heat generation and cooling, and to maintain the adhesion between the electronic parts and the heat dissipating member.

Therefore, an object of the present technology is to provide a thermally conductive sheet that is excellent in adhesion to electronic components and capable of suppressing deviation from the sticking position, a method for manufacturing the thermally conductive sheet, and an electronic device using the same.

In order to solve the above-described problems, a thermally conductive sheet according to the present technology is a thermally conductive sheet that is a cured product of a composition containing at least a polymer matrix component and a fibrous thermally conductive filler, and is provided under the following conditions: In 1, the displacement in the length direction is 2.5 mm or less with respect to the state sandwiched by the copper plates.
Condition 1: A heat conductive sheet piece cut into a strip of 20 mm × 5 mm is placed vertically on a copper plate with the length direction facing the vertical direction and one side of the length direction aligned with one side of the copper plate. A heat cycle between -40°C and 100°C (test temperature transition time within 3 minutes, heat retention time after reaching the test temperature for 30 minutes) was performed for 672 hours in a state where the thickness was compressed by 10%.

Further, a method for producing a thermally conductive sheet according to the present technology includes steps of preparing a thermally conductive composition containing a polymer matrix component and a fibrous thermally conductive filler, and forming a molded block from the thermally conductive composition. and a step of slicing the molded block into sheets to obtain a thermally conductive sheet, thereby obtaining the thermally conductive sheet described above.

Further, an electronic device according to the present technology is an electronic device including the thermally conductive sheet described above, the thermally conductive sheet is sandwiched between an electronic component and a heat radiating member, and the thermally conductive sheet has a surface direction of It is used by being fixed in a substantially vertical direction.

According to the present technology, since the displacement in the length direction in a predetermined thermal cycle test is 2.5 mm or less, it is used for electronic components (heat generating components) that generate heat, such as semiconductor elements that are provided in a substantially vertical direction. Even if the heat-generating component repeats heat generation and cooling, the attachment position does not shift significantly, and the heat-generating component is able to adhere to deformations such as warping due to heat generation and cooling, preventing an increase in thermal resistance. , the heat dissipation properties of the heat conductive sheet can be maintained.

In addition, this makes it possible to install heat-generating components such as semiconductor elements in the vertical direction, increasing the degree of freedom in designing electronic equipment, and by installing the IC chip in the vertical direction, the installation width can be reduced. It becomes possible to respond to requests for miniaturization of electronic equipment, such as space saving.

FIG. 1 is a cross-sectional view showing an example of a heat conductive sheet. FIG. 2 is a diagram showing the configuration of a thermal cycle test according to the present technology, (A) is a cross-sectional view showing a state in which a piece of a thermal conductive sheet is sandwiched between copper plates, and (B) is a copper plate using a fastener. FIG. 3C is a front view showing an example of sandwiching the heat-conducting sheet pieces, and (C) is a front view showing a state in which one side of the heat-conducting sheet piece in the length direction is aligned with one side of the copper plate. FIG. 3 is a diagram showing the amount of deviation after a heat cycle test of a piece of thermally conductive sheet sandwiched between copper plates. FIG. 4 is a cross-sectional view showing an example of a semiconductor device to which a heat conductive sheet is applied.

A thermally conductive sheet to which the present technology is applied, a method for manufacturing the thermally conductive sheet, and an electronic device using the same will be described in detail below with reference to the drawings. In addition, the present technology is not limited to the following embodiments, and various modifications are possible without departing from the gist of the present technology. Also, the drawings are schematic, and the ratio of each dimension may differ from the actual one. Specific dimensions and the like should be determined with reference to the following description. In addition, it goes without saying that there are portions with different dimensional relationships and ratios between the drawings.

FIG. 1 is a cross-sectional view showing an example of a heat conductive sheet according to the present technology. The heat conductive sheet 1 shown in FIG. 1 is a heat conductive sheet that is a cured product of a composition containing at least a polymer matrix component 2 and a fibrous heat conductive filler 3, and is a copper plate under the following condition 1. The displacement in the length direction is 2.5 mm or less on the basis of the sandwiched state.
Condition 1: A heat conductive sheet piece cut into a strip of 20 mm × 5 mm is placed vertically on a copper plate with the length direction facing the vertical direction and one side of the length direction aligned with one side of the copper plate. A heat cycle between -40°C and 100°C (test temperature transition time within 3 minutes, heat retention time after reaching the test temperature for 30 minutes) was performed for 672 hours in a state where the thickness was compressed by 10%.

The heat conductive sheet 1 to which the present technology is applied has a deviation of 2.5 mm or less in the length direction under condition 1, so even if the electronic component repeats heat generation and cooling, the deviation length will be Even if it protrudes from between the component and the heat radiating member, it has a recovery rate of 85% or more in the part sandwiched between the electronic component and the heat radiating member, and prevents displacement and falling from the predetermined sticking position. be able to. In addition, the thermally conductive sheet 1 follows even when the electronic parts are deformed due to repeated heat generation and cooling, and can continue to maintain adhesion to the electronic parts and the heat dissipating member, thereby suppressing an increase in thermal resistance. .

It should be noted that the measurement of the amount of displacement by the thermal cycle test is based on the state where the copper plate is sandwiched between the copper plates and protrudes from the side edge of the copper plate, and the amount of displacement in the protruding portion is measured. This is because it is necessary to examine resistance to thermal cycles (presence or absence of misalignment and adhesion) in a state of being sandwiched between an electronic component and a heat radiating member and compressed by 10%.

It should be noted that the thickness of the heat conductive sheet piece to be subjected to the thermal cycle test can be suitably used, for example, 1.0 mm or 2.0 mm.

　Figures 2 and 3 are diagrams showing a thermal cycle test according to Condition 1 according to the present technology. As shown in FIG. 2(A), under Condition 1, two copper plates 10 (3.0 mm×3.0 mm, thickness 2.0 mm) were cut into strips of 20 mm×5 mm to form a thermally conductive sheet piece. 11 is sandwiched. Further, as shown in FIG. 2(A), a spacer 12 is arranged between the two copper plates 10, 10 to define the distance between the copper plates so that the compression ratio of the heat conductive sheet pieces 11 is 10%. be done. As shown in FIG. 2B, for example, two copper plates 10, 10 can hold the heat conductive sheet pieces 11 in a sandwiched state using bolts provided at the corners of the two copper plates 10, 10. and a method of fastening with a fastener 13 such as a nut. Also, the side edges of the copper plates 10, 10 may be clamped with clips. From the viewpoint of preventing warping of the copper plate 10 in the thermal cycle test, it is preferable to provide the spacer 12 integrally with or near the outer edge of the copper plate 10 , for example, the fastener 13 .

In addition, as shown in FIG. 2(C), the heat-conducting sheet piece 11 is sandwiched with one side in the longitudinal direction aligned with one side 10a (lower piece) of the copper plate 10 . As a result, the heat-conducting sheet piece 11 protrudes slightly from one side of the copper plate 10, as shown in FIG. 2(A). As shown in FIG. 3, the sandwiched state between the copper plates 10 is used as a reference for measuring the amount of displacement, and the length by which the protruding tip portion is displaced vertically downward is defined as the displacement S (mm).

The heat-conducting sheet piece 11 sandwiched between the copper plates 10 is treated with the length direction of the heat-conducting sheet piece 11 in the vertical direction and the side 10a of the copper plate 10 where the heat-conducting sheet piece 11 protrudes vertically downward. A thermal cycle test is performed by placing the piece 11 of the heat conductive sheet so that the lower edge of the piece 11 does not touch the ground.

The thermally conductive sheet 1 shown in FIG. 1 is a thermally conductive sheet that is a cured product of a composition containing at least a polymer matrix component 2 (binder resin) and a fibrous thermally conductive filler 3. Moreover, the thermally conductive sheet 1 may further contain thermally conductive fillers 4 other than the fibrous thermally conductive fillers 3 .

Then, the heat conductive sheet 1 has a displacement of 2.5 mm or less in the length direction when the thermal cycle test is performed under the condition 1 described above. That is, the thermally conductive sheet 1 is sandwiched between a heat-generating electronic component and a heat radiating member, and even when the electronic component repeats heat generation and cooling, the deviation in the vertical direction remains at 2.5 mm or less. If the deviation in the thermal cycle test under Condition 1 exceeds 2.5 mm, it becomes difficult to maintain a recovery rate of 85% or more, and the electronic component repeats heat generation and cooling, resulting in position deviation from the predetermined attachment position. or fall can occur. In addition, when the electronic component is deformed by repeating heat generation and cooling, it cannot be followed, and there is a risk of an increase in thermal resistance due to reduced adhesion between the electronic component and the heat radiating member.

In the present technology, the recovery rate means that a disk-shaped heat conductive sheet with a thickness of 1 mm and a diameter of 29 mm is compressed to 0.7 mm (70% of the initial thickness) at room temperature, held for 24 hours, and after releasing the pressure, the recovery rate is 30%. It refers to the value obtained by dividing the thickness after minutes by the original thickness (1 mm) x 100 (%).

Further, the thermally conductive sheet according to the present technology is a thermally conductive sheet that is a cured product of a composition containing at least a polymer matrix component and a fibrous thermally conductive filler, and is sandwiched between copper plates under condition 2 below. A thermally conductive sheet having a lengthwise deviation of 2.5 mm or less based on the state where the sheets are placed may be used.
Condition 2: A heat conductive sheet piece cut into a strip of 20 mm × 5 mm is placed vertically on a copper plate with the length direction facing the vertical direction and one side of the length direction aligned with one side of the copper plate. A heat cycle between -55°C and 125°C (test temperature transition time within 3 minutes, heat retention time after reaching the test temperature for 30 minutes) was performed for 672 hours in a state where the thickness was compressed by 10%.

Under condition 2, the temperature range of the thermal cycle is wider than under condition 1 described above. Since the displacement in the length direction under condition 2 is 2.5 mm or less, even when placed in a harsher environment than condition 1, it has a recovery rate of 85% or more, and can be removed from the predetermined attachment position. It is possible to prevent misalignment and falling, and even if electronic parts are deformed due to repeated heat generation and cooling, it will continue to maintain adhesion to electronic parts and heat dissipation materials, preventing increases in thermal resistance. can be suppressed.

In addition, the heat conductive sheet 1 has a length direction deviation of 2.5 mm or less based on the condition 1 or condition 2 sandwiched between the copper plates, so that the type OO durometer conforming to ASTM D 2240 is 20 or more. It preferably has a hardness of less than 60. If the hardness is 60 or more, the restoring force is insufficient under condition 1 or condition 2, which may cause displacement or fall from the predetermined sticking position. In addition, when the electronic component is deformed by repeating heat generation and cooling, it cannot be followed, and there is a possibility that the adhesion between the electronic component and the heat radiating member is impaired, resulting in an increase in thermal resistance.

In addition, from the viewpoint that the heat conductive sheet 1 has a lengthwise displacement of 2.5 mm or less based on the condition 1 or condition 2 sandwiched between the copper plates, the polymer matrix component is a two-liquid type It is preferable that the ratio of the main agent, which is an addition reaction type liquid silicone and contains a curing catalyst, and the curing agent, satisfies the following conditions.
Main agent: Curing agent = 35:65 to 70:30

If the main ingredient component is relatively smaller than the curing agent component than the above ratio, the uncured component of the silicone exudes less as described later, and the tackiness of the sheet surface becomes insufficient. It may cause misalignment or fall from the sticking position. If the main agent component is relatively larger than the curing agent component than the above ratio, the restoring force will be insufficient due to the decrease in the crosslinking density of the silicone, and the expansion and contraction of the copper plate cannot be followed under the above condition 1 or condition 2. It can cause misalignment and falling from the

In addition, the heat conductive sheet 1 has a compressive stress of 5.0 [psi] or more from the viewpoint that the displacement in the length direction is 2.5 mm or less with respect to the state sandwiched by the copper plates under the above condition 1 or condition 2. Preferably. The compressive stress is measured by cutting a 2.0 mm thick heat conductive sheet into 25 mm squares, compressing it by 30% with a Tensilon at a pressing speed of 20 mm/sec, holding it for 3 minutes, and measuring the compressive stress after 3 minutes. Measured value (psi).

In addition, the thermally conductive sheet 1 further contains at least one selected from aluminum compounds as a thermally conductive filler, and the content of the aluminum compound is preferably more than 39% by volume and less than 51% by volume. When the content of the aluminum compound is 39% by volume or less, the thermal conductivity decreases due to insufficient filling. Moreover, when the content of the aluminum compound is 51% by volume or more, it interferes with the filling of the fibrous thermally conductive filler.

The thickness of the heat conductive sheet 1 is not particularly limited, and can be appropriately selected according to the purpose. For example, the thickness of the heat conductive sheet 1 can be 0.05 mm or more, and can also be 0.1 mm or more. Moreover, the upper limit of the thickness of the heat conductive sheet 1 may be 5 mm or less, may be 4 mm or less, or may be 3 mm or less. From the standpoint of handleability, the heat conductive sheet 1 preferably has a thickness of 0.1 to 4 mm. The thickness of the thermally conductive sheet 1 can be determined, for example, by measuring the thickness of the thermally conductive sheet 1 at five arbitrary points and calculating the arithmetic average value thereof.

Specific examples of the constituent elements of the thermally conductive sheet 1 will be described below. The thermally conductive sheet 1 is, for example, a cured product of a composition containing at least a polymer matrix component (binder resin) 2 and a fibrous thermally conductive filler 3 .

<Polymer matrix component>
The polymeric matrix component 2 is for holding the fibrous thermally conductive fillers 3 and other thermally conductive fillers 4 within the thermally conductive sheet 1 . The polymer matrix component 2 is selected according to properties such as mechanical strength, heat resistance and electrical properties required for the heat conductive sheet 1 . The polymer matrix component 2 can be selected from thermoplastic resins, thermoplastic elastomers, and thermosetting resins.

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, Fluorinated polymers such as polyvinyl alcohol, polyvinyl acetal, polyvinylidene fluoride and polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer Polymer (ABS) resin, polyphenylene-ether copolymer (PPE) resin, modified PPE resin, aliphatic polyamides, aromatic polyamides, polyimide, polyamideimide, polymethacrylic acid, polymethacrylic acid such as polymethacrylic acid methyl ester acid esters, polyacrylic acids, polycarbonates, polyphenylene sulfides, polysulfones, polyethersulfones, polyethernitrile, polyetherketones, polyketones, liquid crystal polymers, silicone resins, ionomers and the like.

Thermoplastic elastomers include styrene-butadiene block copolymers or hydrogenated products thereof, styrene-isoprene block copolymers or hydrogenated products thereof, styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, and vinyl chloride-based thermoplastic elastomers. , polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and the like.

Thermosetting resins include crosslinked rubbers, epoxy resins, phenolic resins, polyimide resins, unsaturated polyester resins, diallyl phthalate resins, and the like. Specific examples of crosslinked rubber 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 silicone rubber.

As the polymer matrix component 2, for example, a silicone resin is preferable in consideration of the adhesion between the heat generating surface and the heat sink surface of the electronic component. As the silicone resin, for example, a two-component addition reaction type silicone resin composed of a silicone having an alkenyl group as a main component, a main agent containing a curing catalyst, and a curing agent having a hydrosilyl group (Si—H group). can be used. As the alkenyl group-containing silicone, for example, a vinyl group-containing polyorganosiloxane can be used. The curing catalyst is a catalyst for promoting the addition reaction between the alkenyl group in the alkenyl group-containing silicone and the hydrosilyl group in the hydrosilyl group-containing curing agent. As the curing catalyst, well-known catalysts used for hydrosilylation reaction can be used. For example, platinum group curing catalysts, such as platinum group metals such as platinum, rhodium and palladium, and platinum chloride can be used. As the curing agent having hydrosilyl groups, for example, polyorganosiloxane having hydrosilyl groups can be used. The polymer matrix component 2 may be used singly or in combination of two or more.

The content of the polymer matrix component 2 in the heat conductive sheet 1 is not particularly limited, and can be appropriately selected according to the purpose. For example, the content of the polymer matrix component 2 in the thermally conductive sheet 1 may be 20% by volume or more, may be 25% by volume or more, or may be 30% by volume, from the viewpoint of the flexibility of the thermally conductive sheet 1. It may be vol % or more, or 35 vol % or more. In addition, the content of the polymer matrix component 2 in the thermally conductive sheet 1 can be 70% by volume or less, and may be 60% by volume or less, from the viewpoint of the thermal conductivity of the thermally conductive sheet 1. It may be 50% by volume or less, 41% by volume or less, or 39% by volume or less. In addition, the content of the polymer matrix component 2 in the thermally conductive sheet 1 is preferably 20 to 50% by volume, for example, from the viewpoint of compressive stress and recovery rate of the thermally conductive sheet 1, 35% by volume or more, It is more preferable to make it 41 volume % or less.

<Fibrous Thermally Conductive Filler>
A thermally conductive sheet 1 contains a fibrous thermally conductive filler 3 . The fibrous thermally conductive filler 3 has a long axis and a short axis, and the length of the long axis and the short axis are different, and the aspect ratio (average long axis length/average short axis length) exceeds 1. Including those that are in shape. The fibrous thermally conductive filler 3 may be used singly or in combination of two or more. The fibrous thermally conductive filler 3 can be appropriately selected depending on the intended purpose. For example, metal fiber, carbon fiber, etc. can be used, and carbon fiber is preferable.

Carbon fibers include, for example, pitch-based carbon fiber, PAN-based carbon fiber, carbon fiber obtained by graphitizing PBO fiber, arc discharge method, laser evaporation method, CVD method (chemical vapor deposition method), CCVD method (catalytic chemical vapor deposition method), growth method) or the like can be used. Among these, pitch-based carbon fibers are preferable from the viewpoint of thermal conductivity.

The average fiber length (average long axis length) of the fibrous thermally conductive filler 3 can be, for example, 50 to 250 μm, and may be 75 to 220 μm. In addition, the average fiber diameter (average minor axis length) of the fibrous thermally conductive filler 3 can be appropriately selected according to the purpose, and can be, for example, 4 to 20 μm, such as 5 to 14 μm. may The aspect ratio of the fibrous thermally conductive filler 3 can be appropriately selected according to the purpose. good. The average major axis length and average minor axis length of the fibrous thermally conductive filler 3 can be measured with, for example, a microscope or scanning electron microscope (SEM).

The surface of the carbon fiber may be covered with an insulating film depending on the purpose. Thus, insulation-coated carbon fibers can be used as the carbon fibers. The insulation-coated carbon fiber has a carbon fiber and an insulation coating on at least part of the surface of the carbon fiber, and may contain other components as necessary.

The insulating film is made of an electrically insulating material, such as silicon oxide or a hardened polymer material. The polymerizable material is, for example, a radical polymerizable material such as a polymerizable organic compound and a polymerizable resin. The radically polymerizable material can be appropriately selected according to the purpose as long as it is a material that undergoes radical polymerization using energy. Examples thereof include compounds having a radically polymerizable double bond. Examples of radically polymerizable double bonds include vinyl groups, acryloyl groups, and methacryloyl groups. The number of radically polymerizable double bonds in the compound having radically polymerizable double bonds is preferably two or more from the viewpoint of strength including heat resistance and solvent resistance. Examples of compounds having two or more radically polymerizable double bonds include divinylbenzene (DVB) and compounds having two or more (meth)acryloyl groups. The radically polymerizable material may be used singly or in combination of two or more. The molecular weight of the radically polymerizable material can be appropriately selected depending on the purpose, and can be in the range of 50-500, for example. When the insulating coating is formed of a cured product of a polymerizable material, the content of structural units derived from the polymerizable material in the insulating coating can be, for example, 50% by mass or more, and can be 90% by mass or more. can also

The average thickness of the insulating film can be appropriately selected depending on the purpose, and from the viewpoint of realizing high insulation, it can be 50 nm or more, may be 100 nm or more, or may be 200 nm or more. . The upper limit of the average thickness of the insulating coating can be, for example, 1000 nm or less, and may be 500 nm or less. The average thickness of the insulating coating can be determined, for example, by observation with a transmission electron microscope (TEM).

Examples of methods for coating carbon fibers with an insulating film include a sol-gel method, a liquid phase deposition method, a polysiloxane method, and a polymerizable material on at least a part of the surface of the carbon fiber described in JP-A-2018-98515. Examples include a method of forming an insulating film made of a cured product.

The content of the fibrous thermally conductive filler 3 in the thermally conductive sheet 1 can be, for example, 5% by volume or more, and should be 10% by volume or more, from the viewpoint of thermal conductivity of the thermally conductive sheet 1. It can be 14% by volume or more, it can be 20% by volume or more, or it can be 25% by volume or more. In addition, the content of the fibrous thermally conductive filler 3 in the thermally conductive sheet 1 can be, for example, 30% by volume or less, and 28% by volume or less, from the viewpoint of the moldability of the thermally conductive sheet 1. It can also be 25% by volume or less, or 23% by volume or less. The content of the fibrous thermally conductive filler 3 in the thermally conductive sheet 1 can be, for example, 5 to 50% by volume, preferably 14 to 23% by volume. When two or more types of fibrous thermally conductive fillers 3 are used in combination, it is preferable that the total amount thereof satisfies the content described above.

<Other Thermally Conductive Fillers>
Other thermally conductive fillers 4 are thermally conductive fillers other than the fibrous thermally conductive fillers 3 described above, and include, for example, inorganic fillers. Other shapes of the thermally conductive filler 4 include, for example, a spherical shape, a crushed shape, an ellipsoidal shape, a massive shape, a granular shape, and a flat shape. The shape of the other thermally conductive filler 4 is preferably crushed, spherical, ellipsoidal, or the like from the viewpoint of filling performance. A crushed form is preferable from the viewpoint of improving the recovery rate when a thermal cycle test is performed in . Other thermally conductive fillers 4 may be used singly or in combination of two or more.

Another thermally conductive filler 4 is, for example, an inorganic filler, and specifically, aluminum oxide (alumina, sapphire), aluminum nitride, aluminum hydroxide, aluminum, zinc oxide, etc. can be used. In particular, from the viewpoint of the restorability and thermal conductivity of the heat conductive sheet 1, it is preferable to use at least one of aluminum nitride and alumina. and a mode in which these are used in combination.

The average particle diameter (D50) of the alumina particles may be, for example, 0.1 to 10 μm, may be 0.1 to 8 μm, may be 0.1 to 7 μm, may be 0.1 to It may be 2 μm. The average particle size (D50) of the aluminum nitride particles may be, for example, 0.1 to 10 μm, may be 0.1 to 8 μm, may be 0.1 to 7 μm, may be 0.1 It may be ˜2 μm.

The average particle size of the other thermally conductive fillers 4 is the accumulation of the particle size values from the small particle size side of the particle size distribution when the entire particle size distribution of the other thermally conductive fillers 4 is taken as 100%. It means the particle diameter when the cumulative value is 50% when the curve is obtained. The particle size distribution (particle size distribution) is determined by volume. Examples of the method for measuring the particle size distribution include a method using a laser diffraction particle size distribution analyzer.

The other thermally conductive filler 4 may be surface-treated. The surface treatment includes, for example, treating the other thermally conductive filler 4 with a coupling agent such as an alkoxysilane compound. The processing amount of the coupling agent can be, for example, in the range of 0.1 to 1.5% by volume with respect to the total amount of the other thermally conductive fillers 4 .

An alkoxysilane compound is a compound having a structure in which 1 to 3 of the 4 bonds of a silicon atom (Si) are bonded to alkoxy groups, and the remaining bonds are bonded to organic substituents. Examples of the alkoxy group that the alkoxysilane compound has include a methoxy group, an ethoxy group, and a butoxy group. Specific examples of alkoxysilane compounds include trimethoxysilane compounds and triethoxysilane compounds.

The content of the other thermally conductive filler 4 in the thermally conductive sheet 1 is not particularly limited, and can be appropriately selected according to the purpose. When the heat conductive sheet 1 contains at least one selected from aluminum compounds, the content of the aluminum compound is preferably more than 39% by volume and less than 51% by volume. The content of the aluminum compound in the thermally conductive sheet 1 is preferably 42 to 45% by volume, for example, from the viewpoint of improving the restorability of the thermally conductive sheet 1 . When two or more other thermally conductive fillers 4 are used in combination, the total amount preferably satisfies the content described above.

When the thermally conductive sheet 1 contains the fibrous thermally conductive filler 3 and the other thermally conductive filler 4, the fibrous thermally conductive filler 3 and the other thermally conductive filler 4 in the thermally conductive sheet 1 The total content may be 50% by volume or more, may be 55% by volume or more, or may be 59% by volume or more, from the viewpoint of the restorability and thermal conductivity of the heat conductive sheet 1. , 60% by volume or more. In addition, the total content of the fibrous thermally conductive filler 3 and other thermally conductive fillers 4 in the thermally conductive sheet 1 should be less than 77% by volume from the viewpoint of the restorability of the thermally conductive sheet 1. can be 67% by volume or less, 65% by volume or less, 64% by volume or less, 63% by volume or less, or 62% by volume or less may be 61% by volume or less. The total content of the fibrous thermally conductive filler 3 and the other thermally conductive filler 4 in the thermally conductive sheet 1 is preferably, for example, 59% by volume or more and 65% by volume or less.

The heat conductive sheet 1 may further contain components other than the components described above within a range that does not impair the effects of the present technology. Other components include, for example, dispersants, curing accelerators, retarders, tackifiers, plasticizers, flame retardants, antioxidants, stabilizers, colorants, and the like.

<Method for manufacturing heat conductive sheet>
A method for producing a thermally conductive sheet according to the present technology comprises a step of preparing a thermally conductive composition containing at least a polymer matrix component 2 and a fibrous thermally conductive filler 3 (hereinafter also referred to as step A); A step of forming a molded block from a conductive composition (hereinafter also referred to as step B), and a step of slicing the molded block into sheets to obtain a heat conductive sheet 1 (hereinafter also referred to as step C). have.

As described above, the thermally conductive sheet 1 obtained by this manufacturing method has a displacement of 2.5 mm or less when subjected to the thermal cycle test under the above condition 1 or condition 2, and has a good recovery rate. Therefore, when the thermally conductive sheet 1 is arranged between the heat generating component and the heat radiating member, even if a gap is created between the heat generating component and the heat radiating member, the heat conductive sheet 1 can be easily and quickly removed from the gap. can be followed. As a result, it is possible to suppress the displacement of the thermally conductive sheet 1 and the deterioration of the thermal resistance.

[Step A]
In step A, a thermally conductive composition comprising a polymeric matrix component 2 and fibrous thermally conductive fillers 3 is prepared. The thermally conductive composition may contain other thermally conductive fillers 4 as described above. The thermally conductive composition may be uniformly mixed with various additives and volatile solvents by known methods. When the polymer matrix component is a two-liquid addition reaction type liquid silicone and is composed of a main agent containing a curing catalyst and a curing agent, the ratio of the main agent to the curing agent preferably satisfies the following conditions. By satisfying this ratio, the heat conductive sheet 1 is imparted with tackiness due to the uncured component of the silicone flowing out on the sheet surface, and the desired restoring force is obtained by optimizing the crosslinking density of the silicone. In addition, under condition 1 or condition 2 above, it becomes easier to suppress displacement and fall from the predetermined sticking position.
Main agent: Curing agent = 35:65 to 70:30

In step B, a molded block is formed from the thermally conductive composition. Examples of methods for forming the molded block include an extrusion molding method and a mold molding method. The extrusion molding method and the mold molding method are not particularly limited, and various known extrusion molding methods and mold molding methods can be selected depending on the viscosity of the heat conductive composition and the properties required for the heat conductive sheet 1. can be adopted as appropriate. For example, in extrusion molding, when the thermally conductive composition is extruded through a die, or in mold molding, when the thermally conductive composition is pressed into a mold, the polymer matrix component 2 flows along the flow direction. , the long axis of the fibrous thermally conductive filler 3 is oriented.

The size and shape of the molded block can be determined according to the required size of the heat conductive sheet. For example, a rectangular parallelepiped having a cross-sectional length of 0.5 to 15 cm and a width of 0.5 to 15 cm can be used. The length of the rectangular parallelepiped may be determined as required. In the extrusion molding method, it is easy to form a columnar molded block made of a cured product of the thermally conductive composition, in which the long axis of the fibrous thermally conductive filler 3 is oriented in the extrusion direction.

The obtained molded block is preferably heat-cured. The curing temperature in thermosetting can be appropriately selected according to the purpose. For example, when the polymer matrix component 2 is a silicone resin, it can be in the range of 60°C to 120°C. Curing time in thermal curing can be, for example, in the range of 30 minutes to 10 hours.

<Process C>
In step C, the molded block is sliced into sheets to obtain thermally conductive sheets 1 in which the long axes of the fibrous thermally conductive fillers 3 are oriented in the thickness direction. The fibrous thermally conductive filler 3 is exposed on the surface (slice surface) of the sheet obtained by slicing. The slicing method is not particularly limited, and can be appropriately selected from among known slicing devices according to the size and mechanical strength of the compact block. Examples of the slicing device include an ultrasonic cutter and a planer. As for the slicing direction of the molded block, when the molding method is an extrusion molding method, the long axis of the fibrous thermally conductive filler 3 may be oriented in the extrusion direction. Preferably 120 degrees, more preferably 70-100 degrees, and even more preferably 90 degrees (perpendicular).

Thus, in the manufacturing method including the steps A, B, and C, the thermally conductive sheet 1 in which the fibrous thermally conductive filler 3 is dispersed in the polymer matrix component 2, and the fibrous thermally conductive It is possible to obtain a thermally conductive sheet 1 in which the elastic filler 3 is oriented in the thickness direction in a cross-sectional view.

The method for manufacturing the thermally conductive sheet 1 is not limited to the example described above, and for example, after the process C, it may further include a process D for pressing the sliced surface. In the manufacturing method having such a step D, the surface of the thermally conductive sheet 1 obtained in the step C is made smoother, and the adhesion with other members can be further improved. As a method of pressing, a pair of pressing devices comprising a flat plate and a press head having a flat surface can be used. Alternatively, the surface of the heat conductive sheet 1 may be pressed with pinch rolls.

The pressure during pressing may be, for example, in the range of 0.1 to 100 MPa, may be in the range of 0.1 to 1 MPa, or may be in the range of 0.1 to 0.5 MPa. The pressing time can be appropriately selected according to the pressure during pressing, the sheet area, etc., and can be, for example, in the range of 10 seconds to 5 minutes, and may be in the range of 30 seconds to 3 minutes. .

In order to further enhance the effect of pressing and shorten the pressing time, pressing may be performed at a temperature equal to or higher than the glass transition temperature (Tg) of the polymer matrix component constituting the molded sheet. As one mode, pressing may be performed while heating using a press head with a built-in heater. The pressing temperature may range, for example, from 0 to 180°C, may range from room temperature (eg, 25°C) to 100°C, or may range from 30 to 100°C.

<Electronic equipment>
The thermal conductive sheet 1 is, for example, an electronic device (thermal device) having a structure arranged between a heat-generating component and a heat-radiating member so that heat generated by the heat-generating component can escape to the heat-radiating member. can be The electronic device has at least a heat-generating component, a heat-dissipating member, and a heat-conducting sheet 1, and may further have other members as necessary.

Heat-generating components are not particularly limited, and include, for example, CPU, GPU (Graphics Processing Unit), DRAM (Dynamic Random Access Memory), integrated circuit elements such as flash memory, transistors, resistors, and other electronic components that generate heat in electric circuits. etc. Heat-generating components also include components that receive optical signals, such as optical transceivers in communication equipment.

The heat dissipation member is not particularly limited, and examples include those used in combination with integrated circuit elements, transistors, optical transceiver housings, such as heat sinks and heat spreaders. Materials for the heat sink and heat spreader include, for example, copper and aluminum. As the heat dissipating member, in addition to the heat spreader and the heat sink, any member may be used as long as it conducts the heat generated from the heat source and dissipates it to the outside. Heat pipes, vapor chambers, metal covers, housings, and the like. A heat pipe is, for example, a cylindrical, substantially cylindrical, or flat cylindrical hollow structure.

FIG. 4 is a cross-sectional view showing an example of a semiconductor device to which a heat conductive sheet is applied. For example, as shown in FIG. 4, the heat conductive sheet 1 is mounted on a semiconductor device 50 built in various electronic devices, and sandwiched between a heat generating component and a heat radiating member. A semiconductor device 50 shown in FIG. 4 includes an electronic component 51 , a heat spreader 52 , and a heat conductive sheet 1 . By sandwiching the heat conductive sheet 1 between the heat spreader 52 and the heat sink 53 , together with the heat spreader 52 , a heat dissipation member for dissipating the heat of the electronic component 51 is configured. The mounting location of the heat conductive 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, but can be appropriately selected according to the configuration of the electronic device or semiconductor device. The heat spreader 52 is formed, for example, in the shape of a square plate, and has a main surface 52a facing the electronic component 51 and side walls 52b erected along the outer circumference of the main surface 52a. The heat spreader 52 is provided with the heat conductive sheet 1 on the principal surface 52a surrounded by the side walls 52b, and is provided with the heat sink 53 via the heat conductive sheet 1 on the other surface 52c opposite to the principal surface 52a.

Here, the heat conductive sheet 1 to which the present technology is applied can be used by being fixed so that the surface direction is substantially vertical. As electronic devices such as semiconductor devices 50 have become slimmer (miniaturized) in recent years, there are designs in which electronic components 51 that generate heat such as IC chips are installed vertically instead of horizontally. . Since the heat conductive sheet 1 has a lengthwise deviation of 2.5 mm or less in the heat cycle test under the above condition 1 or condition 2, it is used for an electronic component 51 such as a semiconductor element provided in a substantially vertical direction, Even if the electronic component 51 repeats heat generation and cooling, the sticking position does not deviate greatly, and the heat-generating component 51 is closely followed by deformation such as warping due to heat generation and cooling, preventing an increase in thermal resistance. It is possible to maintain the heat dissipation properties of the heat conductive sheet.

Therefore, the semiconductor device 50 can be installed with the electronic component 51 such as a semiconductor element facing the vertical direction. It becomes possible to respond to requests for miniaturization of electronic equipment, such as by achieving space saving in width.

Examples of the present technology will be described below. The present technology is not limited to these examples. In Examples and Comparative Examples, heat conductive sheet samples were formed by changing the amount of silicone resin, the amount of heat conductive filler, and the hardness (type OO durometer hardness according to ASTM D 2240) of the heat conductive resin composition, For each heat conductive sheet sample, the sheet surface tackiness [gf], thermal resistance [°C·cm ² /W], compressibility, compressive stress [psi], and recovery rate [%] were measured and evaluated. Further, according to the conditions 1 and 2, each thermally conductive sheet sample was sandwiched between copper plates and placed vertically, subjected to a thermal cycle test, and displacement of the sheets was observed.

[Thermal resistance and compressibility]
Thermal resistance was evaluated by measuring the thermal resistance [° C.·cm ² /W] of a 2.0 mm thick thermal conductive sheet sample with a load of 0.7 kgf/cm ² according to ASTM-D5470. Compressibility was calculated from the thickness at the time of thermal resistance measurement.

[Bulk thermal conductivity]
For bulk thermal conductivity, the thermal resistance of each thermal conductive sheet is measured by a method in accordance with ASTM-D5470, the horizontal axis is the thickness (mm) of the thermal conductive sheet at the time of measurement, and the vertical axis is the thermal resistance of the thermal conductive sheet ( °C·cm ² /W) was plotted, and the bulk thermal conductivity (W/m·K) of the thermal conductive sheet was calculated from the slope of the plot.

[Type OO hardness]
The hardness of the durometer type OO is measured in accordance with ASTM-D2240 by stacking 5 thermally conductive sheets with a thickness of 2 mm to a thickness of 10 mm, and measuring 5 points on one side and 10 points on both sides in total. .

[Tackiness]
The tackiness (gf) was measured using a Malcom tackiness tester (TK-1S) under the conditions of a load of 50 gf, a pressing time of 0.2 seconds, and a speed of 10 mm/sec.

[Sheet misalignment]
Sheet misalignment evaluation is performed by placing a heat conductive sheet sample cut to 20 x 5 mm in outer size on the central lower side of a 3 cm square copper plate (C1100P), and aligning one side (short side) in the length direction with the lower side of the copper plate. After being placed, it was sandwiched so that the compression ratio was 10%. The length direction of the heat conductive sheet sample was vertical, and the lower side of the copper plate was placed vertically downward. After that, the thermal cycle test according to condition 1 (-40 ° C ⇔ 100 ° C: test temperature transition time within 3 minutes, heat retention time after reaching test temperature 30 minutes, total test time 672 hours) and thermal cycle test according to condition 2 (- 55°C ⇔ 125°C: test temperature transition time within 3 minutes, heat retention time after reaching test temperature 30 minutes, total test time 672 hours), and measure the amount of sheet extrusion after 672 hours. The displacement distance (mm) was calculated by subtracting the initial amount of protrusion from the amount of protrusion after 672 hours. Each thermal cycle test was performed with an air tank tester.

[Compressive stress]
A heat conductive sheet sample with a thickness of 2.0 mm was cut into a 25 mm square, and the compressive stress was measured with a Tensilon. The pressing speed was set to 20 mm/sec, and 30% compression was maintained for 3 minutes to obtain the compressive stress (psi) after 3 minutes.

[Restoration rate]
A heat conductive sheet sample with a thickness of 1.0 mm is cut into a disk shape with a diameter of 29 mm, compressed to 0.7 mm (70% of the initial thickness) at room temperature, held for 24 hours, and after 30 minutes after the pressure is released The restoration rate (=tn/t0×100[%]) was calculated by dividing the thickness tn by the original thickness to (1 mm).

[Example 1]
In Example 1, as shown in Table 1, 42% by volume of alumina particles with an average particle diameter of 2 μm coupled with a silane coupling agent were added to a two-liquid addition reaction type liquid silicone, and fibrous thermally conductive filler was A silicone composition was prepared by mixing 23% by volume of pitch-based carbon fibers having an average fiber length of 150 μm. The total amount of thermally conductive filler in Example 1 is 65% by volume. In addition, the two-liquid addition reaction type liquid silicone resin is mainly composed of organopolysiloxane, and 35% by volume is used together with additives. The composition ratio of the main agent and the curing agent (main agent:curing agent=58:42) was adjusted so that the hardness would be 50 at . The resulting silicone composition was extruded into a hollow quadrangular prism-shaped mold (50 mm x 50 mm) to form a 50 mm square silicone molding. The silicone molded product was heated in an oven at 100° C. for 6 hours to obtain a cured silicone product. The cured silicone material was cut with a slicer to obtain heat conductive sheets with a thickness of 1.0 mm and 2.0 mm.

[Example 2]
In Example 2, as shown in Table 1, 45% by volume of alumina particles with an average particle size of 2 μm coupled with a silane coupling agent were added to a two-liquid addition reaction type liquid silicone, and fibrous thermally conductive filler was A silicone composition was prepared by mixing 14% by volume of pitch-based carbon fibers having an average fiber length of 150 μm. The total amount of thermally conductive filler in Example 2 is 59% by volume. In addition, the two-liquid addition reaction type liquid silicone resin uses 41% by volume of organopolysiloxane as the main component together with additives, and the completed heat conductive sheet is ASTM D 2240 compliant type OO durometer The composition ratio of the main agent and the curing agent (main agent:curing agent=59:41) was adjusted so that the hardness would be 30 at . The resulting silicone composition was extruded into a hollow quadrangular prism-shaped mold (50 mm x 50 mm) to form a 50 mm square silicone molding. The silicone molded product was heated in an oven at 100° C. for 6 hours to obtain a cured silicone product. The cured silicone material was cut with a slicer to obtain heat conductive sheets with a thickness of 1.0 mm and 2.0 mm.

[Example 3]
In Example 3, as shown in Table 1, 22% by volume of alumina particles with an average particle size of 2 μm and aluminum nitride with an average particle size of 1.5 μm, which were subjected to coupling treatment with a silane coupling agent, were added to a two-liquid addition reaction type liquid silicone. A silicone composition was prepared by mixing 23% by volume of particles and 20% by volume of pitch-based carbon fiber having an average fiber length of 150 μm as a fibrous thermally conductive filler. The total amount of thermally conductive filler in Example 3 is 65% by volume. In addition, the two-liquid addition reaction type liquid silicone resin is mainly composed of organopolysiloxane, and 35% by volume is used together with additives. The composition ratio of the main agent and the curing agent (main agent:curing agent=57:43) was adjusted so that the hardness would be 50 at . The resulting silicone composition was extruded into a hollow quadrangular prism-shaped mold (50 mm x 50 mm) to form a 50 mm square silicone molding. The silicone molded product was heated in an oven at 100° C. for 6 hours to obtain a cured silicone product. The cured silicone material was cut with a slicer to obtain heat conductive sheets with a thickness of 1.0 mm and 2.0 mm.

[Comparative Example 1]
In Comparative Example 1, as shown in Table 1, 51% by volume of alumina particles with an average particle size of 2 μm coupled with a silane coupling agent were added to a two-liquid addition reaction type liquid silicone, and fibrous thermally conductive filler was A silicone composition was prepared by mixing 12% by volume of pitch-based carbon fibers having an average fiber length of 150 μm. The total amount of thermally conductive filler in Comparative Example 1 is 63% by volume. In addition, the two-liquid addition reaction type liquid silicone resin uses 37% by volume of organopolysiloxane as the main component together with additives, and the completed heat conductive sheet is ASTM D 2240 compliant type OO durometer The composition ratio of the main agent and the curing agent (main agent:curing agent=53:47) was adjusted so that the hardness would be 45 at . The resulting silicone composition was extruded into a hollow quadrangular prism-shaped mold (50 mm x 50 mm) to form a 50 mm square silicone molding. The silicone molded product was heated in an oven at 100° C. for 6 hours to obtain a cured silicone product. The cured silicone material was cut with a slicer to obtain heat conductive sheets with a thickness of 1.0 mm and 2.0 mm.

[Comparative Example 2]
In Comparative Example 2, as shown in Table 1, 21% by volume of alumina particles with an average particle size of 2 μm and aluminum nitride with an average particle size of 1.5 μm, which were subjected to coupling treatment with a silane coupling agent, were added to a two-liquid addition reaction type liquid silicone. A silicone composition was prepared by mixing 23% by volume of particles and 23% by volume of pitch-based carbon fiber having an average fiber length of 150 μm as a fibrous thermally conductive filler. The total amount of thermally conductive filler in Comparative Example 2 is 67% by volume. In addition, the two-liquid addition reaction type liquid silicone resin is mainly composed of organopolysiloxane, and 33% by volume is used together with additives. The composition ratio of the main agent and the curing agent (main agent:curing agent=59:41) was adjusted so that the hardness would be 30 at . The resulting silicone composition was extruded into a hollow quadrangular prism-shaped mold (50 mm x 50 mm) to form a 50 mm square silicone molding. The silicone molded product was heated in an oven at 100° C. for 6 hours to obtain a cured silicone product. The cured silicone material was cut with a slicer to obtain heat conductive sheets with a thickness of 1.0 mm and 2.0 mm.

[Comparative Example 3]
In Comparative Example 3, as shown in Table 1, 22% by volume of alumina particles with an average particle size of 2 μm and aluminum nitride with an average particle size of 1.5 μm, which were subjected to coupling treatment with a silane coupling agent, were added to a two-liquid addition reaction type liquid silicone. A silicone composition was prepared by mixing 23% by volume of particles and 20% by volume of pitch-based carbon fiber having an average fiber length of 150 μm as a fibrous thermally conductive filler. The total amount of thermally conductive filler in Comparative Example 3 is 65% by volume. In addition, the two-liquid addition reaction type liquid silicone resin is mainly composed of organopolysiloxane, and 35% by volume is used together with additives. The composition ratio of the main agent and the curing agent (main agent:curing agent=50:50) was adjusted so that the hardness would be 60 at . The resulting silicone composition was extruded into a hollow quadrangular prism-shaped mold (50 mm x 50 mm) to form a 50 mm square silicone molding. The silicone molded product was heated in an oven at 100° C. for 6 hours to obtain a cured silicone product. The cured silicone material was cut with a slicer to obtain heat conductive sheets with a thickness of 1.0 mm and 2.0 mm.

Next, the thermally conductive sheets according to Examples 1 to 3 and Comparative Examples 1 to 3 were sandwiched between release-treated PET films and pressed under the conditions of 87 ° C., 0.5 MPa, and 3 minutes, thereby heat conduction. A sheet sample was obtained. For each heat conductive sheet sample, the sheet surface tackiness [gf], thermal resistance [°C·cm ² /W], compressibility, compressive stress [psi], and recovery rate [%] were measured and evaluated. In addition, according to the above conditions 1 and 2, each heat conductive sheet sample was sandwiched between copper plates and placed vertically, put into a thermal cycle test, and the amount of deviation of the sheet was measured and evaluated (○: good, ×: not good). .

As shown in Table 1, in the thermally conductive sheet samples according to Examples 1 to 3, even after undergoing the thermal cycle test under conditions 1 and 2, the deviation of the sheet was 2.5 mm or less, indicating that the attachment position deviated significantly. In addition, it has a compressive stress of 5.0 or more and a recovery rate of 85% or more. In other words, even when it is attached to a heat-generating component that repeats heat generation and cooling, the attachment position does not shift, and it follows deformation such as warping due to heat generation and cooling of the heat-generating component and adheres to it, preventing an increase in thermal resistance. It can be seen that this can be prevented and the heat dissipation properties of the heat conductive sheet can be maintained.

On the other hand, in the heat conductive sheet samples according to Comparative Examples 1 to 3, sheet misalignment exceeding 2.5 mm was observed in the thermal cycle test under conditions 1 and 2. Therefore, the sticking position shifts, and the compressive stress and the recovery rate deteriorate. When the adhesive is stuck to a heat-generating part that repeats heat generation and cooling, the sticking position shifts, and the heat-generating part deforms such as warping due to heat generation and cooling. , and there is a risk of causing an increase in thermal resistance.

It should be noted that, as shown in Table 1 [Comparative Example 2], misalignment of the heat conductive sheet occurs even if there is tack. In other words, there is no correlation between the presence or absence of tack in the heat conductive sheet and the misalignment of the heat conductive sheet. I understand.

This is thought to be due to the different coefficients of thermal expansion between the heat conductive sheet and the copper plate. That is, a thermally conductive sheet having a low compressive stress cannot follow expansion and contraction against a thermal shock, and even if there is a tack force, the thermally conductive sheet is separated from the copper plate, resulting in deviation of the thermally conductive sheet. A thermally conductive sheet with a large compressive stress can maintain adhesion to a copper plate due to contraction and expansion at the time of thermal shock.

1 thermally conductive sheet 2 polymer matrix component 3 fibrous thermally conductive filler 4 other thermally conductive filler 10 copper plate 11 thermally conductive sheet piece 12 spacer

Claims (9)

1. A thermally conductive sheet that is a cured product of a composition containing at least a polymer matrix component and a fibrous thermally conductive filler, and has a lengthwise shift of 2 with respect to the state sandwiched between copper plates under the following condition 1: A thermally conductive sheet that is 5 mm or less.
   Condition 1: A heat conductive sheet piece cut into a strip of 20 mm × 5 mm is placed vertically on a copper plate with the length direction facing the vertical direction and one side of the length direction aligned with one side of the copper plate. A heat cycle between -40°C and 100°C (test temperature transition time within 3 minutes, heat retention time after reaching the test temperature for 30 minutes) was performed for 672 hours in a state where the thickness was compressed by 10%.
2. A thermally conductive sheet that is a cured product of a composition containing at least a polymer matrix component and a fibrous thermally conductive filler, and has a lengthwise deviation of 2 based on the state sandwiched between copper plates under condition 2 below. A thermally conductive sheet that is 5 mm or less.
   Condition 2: A heat conductive sheet piece cut into a strip of 20 mm × 5 mm is placed vertically on a copper plate with the length direction facing the vertical direction and one side of the length direction aligned with one side of the copper plate. A heat cycle between -55°C and 125°C (test temperature transition time within 3 minutes, heat retention time after reaching the test temperature for 30 minutes) was performed for 672 hours in a state where the thickness was compressed by 10%.
3. The thermally conductive sheet according to claim 1 or 2, having a hardness of 20 or more and less than 60 in type OO durometer conforming to ASTM D 2240.
4. The heat conductive sheet according to any one of claims 1 to 3, wherein the polymer matrix component is a two-liquid addition reaction type liquid silicone.
5. The heat conductive sheet according to any one of claims 1 to 4, wherein the sheet is compressed to 70% of its initial thickness, held at room temperature for 24 hours, and then released, and has a recovery rate of 85% or more after 30 minutes.
6. The heat conductive sheet according to any one of claims 1 to 5, which has a compressive stress of 5.0 psi or more.
7. 7. The method according to any one of claims 1 to 6, further comprising at least one selected from aluminum compounds as a thermally conductive filler, wherein the content of the aluminum compound is more than 39% by volume and less than 51% by volume. thermal conductive sheet
8. preparing a thermally conductive composition comprising a polymeric matrix component and a fibrous thermally conductive filler;
   forming a molded block from the thermally conductive composition;
   and obtaining a heat conductive sheet by slicing the molded block into a sheet,
   A method for producing a thermally conductive sheet, wherein the thermally conductive sheet is the thermally conductive sheet according to any one of claims 1 to 7.
9. An electronic device comprising the heat conductive sheet according to any one of claims 1 to 7, wherein the heat conductive sheet is sandwiched between an electronic component and a heat dissipation member,
   An electronic device, wherein the heat conductive sheet is fixed so that the surface direction thereof is substantially vertical.
   

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