Sheet-like heat dissipation member and thermally conductive composite

Abstract

Provided is a heat-dissipating member which has excellent adhesion to a heat-dissipating electronic component and a heat-dissipating component, has excellent thermal conductivity and insulating properties, and has excellent reliability. The heat-dissipating member is a sheet-like heat-dissipating member having a composition layer composed of a heat-softening heat-conducting composition containing: (A) 100 parts by mass of a silicone resin that is solid at 25 DEG C and has a unit selected from R1SiO3 / 2 units (in the formula, R1 represents a hydrogen atom, R2 represents a hydrogen atom, and R3 represents a hydrogen atom; and (B) 1200-3500 parts by mass of a thermally conductive filler comprising (B-1) 120-1750 parts by mass of an aluminum oxide having an average particle diameter of 0.1-70 [mu] m, and (B-2) 600-2880 parts by mass of an aluminum nitride having an average particle diameter of 0.1-70 [mu] m and a specific surface area of 4.0 m2 / g or less, where (B-1) / (B-2) = 1 / 9-1 / 1 in terms of mass ratio, and R1 represents a monovalent hydrocarbon group having 1-10 carbon atoms), and (B) a thermally conductive filler comprising (B-1) 120-1750 parts by mass of an aluminum oxide having an average particle diameter of 0.1-70 [mu] m, and (B-2) 600-2880 parts by mass of an aluminum nitride having an average particle diameter of 0.1-70 [mu] m.

Description

Technical Field

[0001] The present invention relates to a sheet-like heat dissipation member and a thermal conductivity composite body. Background Art

[0002] In recent years, in electronic devices and the like, in order to suppress the temperature rise of electronic components, a heat-softening material that is solid at room temperature and has good workability and that softens or melts by heat generated from electronic components has attracted increasing attention. This heat-softening material is a thermal conductivity member having the characteristics of both good operability of a low-hardness thermal conductivity sheet and low thermal resistance of a thermal conductivity grease.

[0003] In particular, as a material excellent in heat resistance, weather resistance, and flame retardant required as a heat dissipation material, silicone is known, and many heat-softening materials based on silicone have been proposed.

[0004] In Patent Document 1, a composition composed of a thermoplastic silicone resin, a waxy modified silicone resin, and a thermal conductivity filler is proposed. In Patent Document 2, a thermal conductivity sheet composed of an adhesive resin such as silicone gel, wax, and a thermal conductivity filler is proposed. In Patent Document 3, a heat-softening heat dissipation sheet composed of a polymer gel such as silicone, a modified silicone, a compound that becomes liquid when heated such as wax, and a thermal conductivity filler is proposed.

[0005] However, since these heat-softening heat dissipation sheets use organic substances such as wax and wax obtained by modifying silicone in addition to silicone, they have disadvantages of poor flame retardancy and heat resistance compared to using silicone alone.

[0006] Also, in applications requiring high heat dissipation in recent years, these heat-softening heat dissipation sheets cannot obtain sufficient effects due to lack of thermal conductivity.

[0007] Therefore, in Patent Document 4, a heat-softening heat dissipation material that does not contain organic substances such as wax and wax obtained by modifying silicone but contains a silicone resin as a matrix and limits the particle size of the thermal conductivity filler material is disclosed. However, since the thermal conductivity filler material uses conductive copper powder, it cannot be used in insulating applications, and there are also problems in stable manufacturing management because copper is easily oxidized.

[0008] On the other hand, as ceramic-based thermal conductivity filler materials that can ensure insulation, aluminum nitride, boron nitride, alumina, magnesia, silicon nitride, etc. can be exemplified.

[0009] In making a heat dissipation material highly thermally conductive, it is important how to highly fill a thermal conductivity filler material, and the filler material also preferably has a high thermal conductivity as much as possible.

[0010] In this view, the thermal conductivity of aluminum nitride monomer is 170 W / m·K, which is a high thermal conductivity, so high thermal conductivity can be expected.

[0011] However, aluminum nitride has poor filling property for silicone. Due to high filling, the fluidity of the silicone adhesive decreases during thermal softening. Therefore, it cannot follow the fine unevenness on the surface of electronic components and heat sinks, resulting in a large contact thermal resistance and a problem of reduced effective thermal conductivity.

[0012] In addition, aluminum nitride also has problems in terms of water resistance. That is, under high-humidity environmental conditions, while promoting its own hydrolysis reaction, it also promotes the cracking of silicone. Therefore, there is also a concern that pores are generated in the system, leading to a decrease in thermal conductivity.

[0013] On the other hand, alumina has good affinity for silicone. Even with high filling, it is easy to maintain the fluidity of the silicone adhesive and easy to reduce the contact thermal resistance. However, the thermal conductivity of alumina monomer is as poor as 20 W / m·K. Even if it is formulated in the thermally softening material, it is difficult to achieve high thermal conductivity.

[0014] Therefore, there is a need to develop a heat dissipation material that can achieve high thermal conductivity through high filling of fillers, and has good operability and insulation properties, and also has excellent reliability under high-temperature and high-humidity conditions.

[0015] Prior Art Documents

[0016] Patent Documents

[0017] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-327917

[0018] Patent Document 2: Japanese Patent Application Laid-Open No. 2001-291807

[0019] Patent Document 3: Japanese Patent Application Laid-Open No. 2002-234952

[0020] Patent Document 4: Japanese Patent Application Laid-Open No. 2007-059877 Summary of the Invention

[0021] Problems to be Solved by the Invention

[0022] Therefore, an object of the present invention is to provide a heat dissipation member that has good close contact with heat-generating electronic components and heat dissipation components, has good thermal conductivity and insulation properties, and excellent reliability.

[0023] Means for Solving the Problems

[0024] In order to solve the above problems, the present inventors repeatedly conducted intensive studies and as a result, found that the following sheet-like heat dissipation member and heat conductive composite can achieve the above object, thus completing the present invention.

[0025] That is, the present invention is an invention for providing the following sheet-like heat dissipation member and heat conductive composite.

[0026] <1> A sheet-like heat dissipation member having a composition layer composed of a heat-softening heat conductive composition, the heat-softening heat conductive composition containing:

[0027] (A) A silicone resin that is solid at 25°C: 100 parts by mass, the silicone resin having 20 mol% or more of siloxane units selected from R 1 SiO 3 / 2 units (in the formula, R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms) and SiO 4 / 2 units, and

[0028] (B) A heat conductive filler containing the following (B-1) and (B-2): 1200 to 3500 parts by mass,

[0029] (B-1) Alumina having an average particle diameter of 0.1 to 70 μm: 120 to 1750 parts by mass, and

[0030] (B-2) Aluminum nitride having an average particle diameter of 0.1 to 70 μm and a specific surface area of 4.0 m 2 / g or less: 600 to 2880 parts by mass,

[0031] wherein the mixing ratio of (B-1) and (B-2) is (B-1) / (B-2) = 1 / 9 to 1 / 1 by mass ratio.

[0032] <2> The sheet-like heat dissipation member according to <1>, wherein

[0033] the component (A) further has R 1 2SiO 2 / 2 units (in the formula, R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms).

[0034] <3> The sheet-like heat dissipation member according to <1> or <2>, wherein

[0035] the heat-softening heat conductive composition further includes:

[0036] (D) A linear organic polysiloxane having a viscosity of 0.1 to 100 Pa·s at 25°C, having one or more aryl groups with 6 to 12 carbon atoms in one molecule, and being 1 to 30 parts by mass relative to 100 parts by mass of the component (A).

[0037] <4> The sheet-like heat dissipation member according to any one of <1> to <3>, wherein

[0038] The component (B-1) is spherical alumina.

[0039] <5> The sheet-like heat dissipation member according to any one of <1> to <4>, wherein

[0040] The thermoplastic heat conductive composition further comprises:

[0041] (C) An alkylalkoxysilane represented by the following general formula (1), which is 1 to 20 parts by mass relative to 100 parts by mass of the component (A),

[0042] R 2 a R 3 b Si(OR 4 ) 4-a-b (1)

[0043] (In the formula (1), R 2 is an alkyl group having 6 to 15 carbon atoms, R 3 is a monovalent hydrocarbon group having 1 to 4 carbon atoms, R 4 is an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, and wherein, a + b is an integer of 1 to 3.).

[0044] <6> The sheet-like heat dissipation member according to any one of <1> to <5>, wherein

[0045] The thermal conductivity of the cured product of the thermoplastic heat conductive composition is 4.0 W / m·K or more.

[0046] <7> The sheet-like heat dissipation member according to any one of <1> to <6>, wherein

[0047] The thickness of the composition layer is 50 to 300 μm.

[0048] <8> The sheet-like heat dissipation member according to any one of <1> to <7>, wherein

[0049] The insulation breakdown voltage measured by the method described in JIS K6249:2003 is 1 kV or more.

[0050] <9> A heat conductive composite, wherein

[0051] It is formed by disposing the sheet-like heat dissipation member described in any one of <1> to <8> on both sides of a reinforcing layer (X) made of a thermoplastic resin.

[0052] <10>The thermally conductive composite according to <9>, wherein

[0053] The thermoplastic resin is any one of an aromatic polyimide resin, a polyamide resin, a polyamide-imide resin, a polyester resin, and a fluororesin.

[0054] <11>The thermally conductive composite according to <9> or <10>, wherein

[0055] The thickness of the reinforcing layer (X) is 2 to 20 μm.

[0056] It should be noted that in this specification, the so-called "room temperature" refers to the range of 15 to 30 °C, and the so-called "non-fluidity" means that when the substance is in a state where it is difficult to flow. Specifically, it means that after putting 50 g of the sample into a glass bottle with a volume of 100 ml and then horizontally standing it still, and then tilting the glass bottle by 45° and keeping it for 1 hour without deformation.

[0057] Effects of the Invention

[0058] The sheet-like heat dissipation member of the present invention is a sheet-like heat dissipation member having a composition layer composed of a silicone resin that is solid at 25 °C, specific aluminum nitride and aluminum oxide as thermally conductive filler materials, and an optimized blending ratio and filling amount thereof. Thus, the sheet-like heat dissipation member of the present invention has good thermal conductivity and insulation properties, good adhesion to heat-generating electronic components and heat dissipation components, and can achieve high heat dissipation. Further, its reliability is also excellent. Therefore, it can also be applied to in-vehicle uses that require high durability.

[0059] The sheet-like heat dissipation member of the present invention can also be used for, for example, heat dissipation of general power supplies, electronic devices, etc.; heat dissipation of integrated circuit elements such as LSIs and CPUs of electronic devices such as personal computers and DVD players; heat dissipation of IGBT modules, DC-DC converters, LED fog lights, etc. in in-vehicle uses. Detailed Embodiments

[0060] Hereinafter, the present invention will be described in detail.

[0061] [Component (A)]

[0062] (A) The component is a silicone resin and is the component that forms the matrix of the sheet-like heat dissipation member of the present invention. In addition, the (A) component is the element that causes heat release and softening of the sheet-like heat dissipation member of the present invention, and also functions as an adhesive to impart processability and operability to the thermally conductive filler of the (B) component.

[0063] As the (A) component, it is characterized in that it is a silicone resin that is solid at 25 °C and has 20 mol% or more of R selected from 1 SiO 3 / 2 units (in the formula, R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms.) and one or more siloxane units selected from SiO 4 / 2 units.

[0064] Among them, the above R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 6 carbon atoms. As specific examples of R 1 , alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, decyl, etc. can be cited; aryl groups such as phenyl, tolyl, xylyl, naphthyl, etc.; aralkyl groups such as benzyl, phenethyl, phenylpropyl, etc.; alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl group, octenyl, etc. It should be noted that the above R 1 can also be a group in which some or all of the hydrogen atoms present in these hydrocarbon groups are substituted with halogen atoms such as fluorine atoms. Among them, methyl, phenyl and vinyl are particularly preferred.

[0065] The silicone resin that is solid at 25 °C as the (A) component contains one or more siloxane units selected from R 1 SiO 3 / 2 units (hereinafter also referred to as T units) and SiO 4 / 2 units (hereinafter also referred to as Q units). For example, silicone resins composed of M units (R 1 3SiO 1 / 2 units) and T units; silicone resins composed of M units and Q units; and silicone resins composed of M units, T units and Q units can be cited.

[0066] The total proportion of T units and Q units in all siloxane units in the (A) component is 20 mol% or more, preferably 20-98 mol%, more preferably 30-96 mol%.

[0067] The silicone resin having T units in particular is preferably capable of improving toughness. Thereby, brittleness in the solid state under room temperature conditions can be improved and breakage during operation can be prevented, etc.

[0068] In addition, in order to enhance the toughness under room temperature conditions, the component (A) may also have D units (R 1 2SiO 2 / 2 units) as its constituent units. As an example of the silicone resin that also has D units, a silicone resin composed of T units and D units; a silicone resin composed of M units, T units, and D units; and a silicone resin composed of M units, Q units, and D units can be cited. Here, as the substituent (R 1 ) of the T unit, methyl and phenyl are preferred; as the substituent of the D unit, methyl, phenyl, and vinyl are preferred. In addition, in the silicone resin composed of M units, T units, and D units, the ratio (mole) of the T unit and the D unit is preferably T:D = 10:90 to 90:10, particularly preferably 20:80 to 80:20.

[0069] As a more specific example of the component (A), the following silicone resins can be cited.

[0070] D m T Φ p D Vi n

[0071] (where D represents a dimethylsiloxane unit (i.e., (CH3)2SiO 2 / 2 ), T Φ represents a phenylsiloxane unit (i.e., (C6H5)SiO 3 / 2 ), D Vi represents a methylvinylsiloxane unit (i.e., (CH3)(CH2=CH)SiO 2 / 2 ), (m + n) / p (molar ratio) = 0.25 to 4.0, (m + n) / m (molar ratio) = 1.0 to 4.0).

[0072] M L T Φ p

[0073] (where M represents a trimethylsiloxane unit (i.e., (CH3)3SiO 1 / 2 ), T Φ represents a phenylsiloxane unit (i.e., (C6H5)SiO 3 / 2 ), L / p (molar ratio) = 0.02 to 3.0).

[0074] M L D mT Φ p D Vi n

[0075] (wherein, M represents a trimethylsiloxane unit (i.e., (CH3)3SiO 1 / 2 ), D, T Φ and D Vi are as described above, (m + n) / p (molar ratio) = 0.25 to 4.0, (m + n) / m (molar ratio) = 1.0 to 4.0, L / (m + n) (molar ratio) = 0.001 to 0.1)

[0076] M L D m Q q D Vi n

[0077] (wherein, Q represents SiO 4 / 2 , M, D and D Vi are as described above, (m + n) / q (molar ratio) = 0.25 to 4.0, (m + n) / m (molar ratio) = 1.0 to 4.0, L / (m + n) (molar ratio) = 0.001 to 0.1)

[0078] If the component (A) has such a structure, the sheet-like heat dissipation member of the present invention is substantially solid at 25°C, and above a certain temperature, preferably above 40°C and below the maximum temperature reached due to the heat release of the exothermic electronic component. Specifically, in the temperature range of about 40 to 150°C, particularly about 40 to 120°C, it can be thermally softened, have a lower viscosity, or be melted and fluidized.

[0079] Here, the temperature of thermal softening, lower viscosity, or melting is the temperature of the heat dissipation member, and the organosilicon resin of the component (A) itself may also be a substance having a melting point lower than 40°C.

[0080] (A) The component can be used alone or in combination of two or more.

[0081] As described above, the silicone resin of component (A) can have a certain degree of viscosity reduction when heated and can be used as an adhesive for a thermally conductive filler. The weight average molecular weight of component (A) in terms of polystyrene converted according to GPC analysis is preferably 500 to 20,000, and particularly preferably 1,000 to 10,000. When the molecular weight is within this range, it is easy to keep the viscosity of the obtained composition within an appropriate range during thermal softening. Therefore, it is easy to prevent pump-out (generation of bubbles caused by separation of the filler and the silicone resin or outflow of the silicone resin) due to thermal cycling, and it is easy to maintain the close contact between the obtained heat dissipation member and the electronic component and the heat dissipation component. It should be noted that component (A) is suitable for imparting flexibility and adhesiveness to the sheet-like heat dissipation member of the present invention. As component (A), a polymer of a single molecular weight can be used, or two or more polymers having different molecular weights can be mixed and used.

[0082] [Component (B)]

[0083] The thermally conductive filler for component (B) is characterized in that it contains alumina of component (B-1) having a specific average particle size and aluminum nitride of component (B-2) having a specific surface area of 4.0 m 2 / g or less in a specific mixing ratio.

[0084] The average particle size of the alumina of component (B-1) is 0.1 to 70 μm, preferably 0.5 to 60 μm, and more preferably 1.0 to 50 μm. When the average particle size is within this range, when component (B) is highly filled, it is easy to achieve the closest packing, which is beneficial for high thermal conductivity, and the workability of the molded product is also excellent.

[0085] It should be noted that in the present invention, the average particle size is the volume average particle size, which is the measured value measured by a Microtrac particle size distribution measuring device MT3300EX (Nikkiso Co., Ltd., Japan).

[0086] Examples of the shape of the alumina of component (B-1) include spherical, circular, and fragmented shapes, and spherical is particularly preferred. Here, the spherical shape means a form in which the aspect ratio in the particle shape is 1.5 or less.

[0087] With respect to 100 parts by mass of component (A), the blending amount of the alumina of component (B-1) is 120 to 1,750 parts by mass, preferably 300 to 1,600 parts by mass, and more preferably 400 to 1,500 parts by mass. Among them, the blending ratio with component (B-2) and the total blending amount of component (B) satisfy the ranges described later.

[0088] The average particle diameter of aluminum nitride as the (B-2) component is 0.1 to 70 μm, preferably 0.5 to 60 μm, and more preferably 1.0 to 50 μm. When the average particle diameter is within this range, during high filling of the (B) component, it is easy to achieve the closest packing, which is beneficial for high thermal conductivity, and the workability of the molded product is also excellent.

[0089] The specific surface area of aluminum nitride as the (B-2) component is 4.0 m 2 / g or less, preferably 3.5 m 2 / g or less, and more preferably 3.2 m 2 / g or less. When the specific surface area of aluminum nitride exceeds the above upper limit value, the composition becomes poor in ductility, and after becoming a molded product (sheet), when it is left for a long time under high temperature and high humidity conditions, it is likely to be affected by hydrolysis etc. and cause a decrease in thermal conductivity. It should be noted that in the present invention, the specific surface area is a value measured by the gas adsorption method, for example, measured by an automatic specific surface area measuring device of Shimadzu Corporation, Japan, etc.

[0090] Examples of the shape of aluminum nitride as the (B-2) component include spherical, fragmented, circular, etc.

[0091] With respect to 100 parts by mass of the (A) component, the blending amount of aluminum nitride as the (B-2) component is 600 to 2880 parts by mass, preferably 800 to 2600 parts by mass, and more preferably 1000 to 2400 parts by mass. Among them, the blending ratio with the (B-1) component and the total blending amount of the (B) component as a whole satisfy the ranges described later.

[0092] With respect to 100 parts by mass of the (A) component, the blending amount of the (B) component, that is, the total blending amount of the (B-1) component and the (B-2) component needs to be 1200 to 3500 parts by mass, preferably 1500 to 3000 parts by mass. When this blending amount is less than 1200 parts by mass, the thermal conductivity of the obtained composition may be poor, and the composition may become a composition with poor storage stability; when this blending amount exceeds 3500 parts by mass, the composition may be poor in ductility and become a molded product with weak strength.

[0093] In addition, the blending ratio of (B-1) and (B-2) is (B-1) / (B-2) = 1 / 9 to 1 / 1 in terms of mass ratio, preferably (B-1) / (B-2) = 1.5 / 8.5 to 1 / 1, and more preferably (B-1) / (B-2) = 1 / 4 to 1 / 1.

[0094] When the ratio of (B-1) / (B-2) is within this range, even when the (B) component is highly filled, the flexibility - followability of the heat dissipation member is not impaired, and the thermal conductivity of the molded product can be effectively improved.

[0095] It should be noted that the component (B) can also be subjected to various known surface treatments within the range that does not significantly impair the effects of the present invention such as heat conductivity. Specifically, for example, coupling agent treatments such as silane-based and titanate-based treatments, and plasma treatment can be cited.

[0096] In addition to the above essential components, the following components can also be used as needed in the present invention.

[0097] [Component (C)]

[0098] Component (C) is an alkylalkoxysilane represented by the following general formula (1). Component (C) is a wetting agent component, and it can be formulated as an optional component in the thermoplastic heat conductive composition. By treating the surface of the heat conductive filler of component (B) with component (C), it is beneficial to the wettability between component (B) and component (A). As a result, component (C) assists in the high filling of the heat conductive powder of component (B).

[0099] R 2 a R 3 b Si(OR 4 ) 4-a-b (1)

[0100] (In formula (1), R 2 is an alkyl group having 6 to 15 carbon atoms, R 3 is a monovalent hydrocarbon group having 1 to 4 carbon atoms, R 4 is an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, and among them, a + b is an integer of 1 to 3).

[0101] The above R 2 is an alkyl group having 6 to 15 carbon atoms. As specific examples thereof, hexyl, octyl, nonyl, decyl, dodecyl, tetradecyl, etc. can be cited. If the number of carbon atoms is less than 6, the wettability with the heat conductive filler (component (B)) is likely to become insufficient; if the number of carbon atoms is greater than 15, component (C) is likely to solidify under normal temperature conditions, so its operation is likely to become inconvenient, and the heat resistance and flame retardancy of the obtained composition are likely to be reduced.

[0102] The above R 3 is a monovalent hydrocarbon group having 1 to 4 carbon atoms, which can also be a saturated monovalent hydrocarbon group or an unsaturated monovalent hydrocarbon group. The hydrogen atoms in this hydrocarbon group can also be replaced by other atomic groups such as halogen atoms. As specific examples thereof, alkyl groups such as methyl, ethyl, propyl, and butyl; alkenyl groups such as vinyl, allyl, and isopropenyl; and halogenated alkyl groups such as 3,3,3-trifluoropropyl can be cited. Particularly preferably, they are methyl and ethyl.

[0103] The above-mentioned R 4 is an alkyl group having 1 to 6 carbon atoms. As specific examples thereof, methyl, ethyl, propyl, butyl, pentyl, hexyl, etc. can be cited, and methyl and ethyl are particularly preferred.

[0104] The above-mentioned a is an integer of 1 to 3, and particularly preferably 1. The above-mentioned b is an integer of 0 to 2. Among them, a + b is an integer of 1 to 3.

[0105] As specific examples of the component (C), the following alkylalkoxysilanes, etc. can be cited.

[0106] C6H 13 Si(OCH3)3

[0107] C 10 H 21 Si(OCH3)3

[0108] C 12 H 25 Si(OCH3)3

[0109] C 12 H 25 Si(OC2H5)3

[0110] C 10 H 21 Si(CH3)(OCH3)2

[0111] C 10 H 21 Si(C6H5)(OCH3)2

[0112] C 10 H 21 Si(CH3)(OC2H5)2

[0113] C 10 H 21 Si(CH=CH2)(OCH3)2

[0114] C 10 H 21 Si(CH2CH2CF3)(OCH3)2

[0115] With respect to 100 parts by mass of the organosilicon resin of the component (A), the blending amount of the component (C) is 1 to 20 parts by mass, more preferably 2 to 15 parts by mass. If the blending amount is within this range, the effect of blending the component (C) is such that while effectively filling the heat conductive filler, the workability of the sheet also becomes good.

[0116] [Component (D)]

[0117] The thermoplastic thermally conductive composition for the sheet-like heat dissipation member of the present invention, as the component (D) other than the components (A) to (C), is preferably a linear organopolysiloxane having a viscosity of 0.1 to 100 Pa·s at 25°C and having one or more aryl groups having 6 to 12 carbon atoms in one molecule.

[0118] As described in the component (A), it is known that the toughness of the resin can be improved by introducing the D unit into the (A) silicone resin. In addition, it has been found that even if the D unit is not introduced into the (A) silicone resin and a linear organopolysiloxane having the D unit is separately blended, the same effect can be obtained. Therefore, when toughness is to be imparted to the thermoplastic thermally conductive composition, it is preferable to blend a linear organopolysiloxane having one or more aryl groups having 6 to 12 carbon atoms in one molecule as the component (D). The component (D) is preferably oily or gum-like, and in the case of being oily, the viscosity is preferably 0.1 to 100 Pa·s. If it is within this range, the toughness can be improved and the brittleness can be improved.

[0119] With respect to 100 parts by mass of the silicone resin of the component (A), the blending amount of the component (D) is preferably 1 to 30 parts by mass, more preferably 2 to 15 parts by mass.

[0120] [Other additives]

[0121] In the thermoplastic thermally conductive composition for the sheet-like heat dissipation member of the present invention, within the range not impairing the object of the present invention, additives or filler materials that are usually used as optional components can be further added to the synthetic rubber. Specifically, silicone oil and fluorine-modified silicone surfactants can be added as mold release agents; carbon black, titanium dioxide, and iron oxide red can be added as colorants; platinum catalysts, metal oxides or metal hydroxides such as iron oxide, titanium oxide, and cerium oxide can be added as flame retardants; processing oils, reactive titanate catalysts, reactive aluminum catalysts, etc. can be added as processability improvers. Further, fine powder silica such as precipitated silica or calcined silica, thixotropy improvers, etc. can be arbitrarily added as anti-settling agents for the thermally conductive filler at high temperatures.

[0122] [Manufacturing method]

[0123] By using a rubber kneader such as a dough mixer (kneader), a gate mixer, or a planetary mixer to blend and knead the above-mentioned respective components, the thermoplastic thermally conductive composition for the sheet-like heat dissipation member of the present invention can be easily manufactured.

[0124] The sheet-like heat dissipation member of the present invention has a composition layer manufactured by forming a heat-softenable heat-conductive composition into a sheet. Here, the so-called sheet means that it is used in the meaning including a film shape and a strip shape. As a method of forming into a sheet, for example, a method of molding the above-mentioned kneaded composition by extrusion molding, calendering molding, roll rolling molding, pressing molding, etc., and a method of coating the composition dissolved in a solvent can be cited. It should be noted that the thickness of the composition layer of the sheet-like heat dissipation member thus manufactured is preferably 50 to 300 μm, more preferably 50 to 250 μm, and particularly preferably 50 to 200 μm. If the thickness is within this range, it is easy to maintain good operability and heat dissipation performance.

[0125] The sheet-like heat dissipation member of the present invention may further have a base material surface-treated with a release agent as a separator film (hereinafter, also referred to as a release-treated film). That is, the separator film may be laminated on both sides of the composition layer of the sheet-like heat dissipation member in contact with the release-treated surface of the base material. By having the separator film, the sheet-like heat dissipation member can be easily transported, standard-cut, etc. At this time, by changing the treatment amount and type of the release agent and the material of the film, the peel force of the two separator films laminated on both sides can also be increased or decreased.

[0126] As this separator film, it is preferable to use a non-dimethyl silicone-based polymer to perform a release treatment on paper or a PET film. As the non-dimethyl silicone-based polymer, non-reactive fluorine-containing silicone-based release agents in which fluorine substituents such as perfluoroalkyl groups and perfluoropolyether groups are bonded to the main chain (hereinafter, referred to as fluorine-modified silicone separator films) can be cited. The above-mentioned perfluoropolyether group can be represented by the following formulas (2) to (4).

[0127] [Chemical formula 1]

[0128]

[0129] C q F 2q+1 CH2OCH2CH2CH2- (4)

[0130] (p is a number from 1 to 5, and q is a number from 3 to 10)

[0131] As commercially available products of this non-reactive fluorine-containing silicone-based release agent, for example, X-70-201, X-70-258, X-41-3035, etc. manufactured by Shin-Etsu Chemical Co., Ltd. can be used. As a coating method on the base material, coating methods such as coating a liquid material on the base material using a bar coater, a knife coater, a beveled wheel coater, a spin coater, etc. and then heating and curing are cited, but are not limited to the above-mentioned methods.

[0132] [Thermal conductivity and viscosity]

[0133] The thermal conductivity of the composition layer of the sheet-like heat dissipation member of the present invention, that is, the thermal conductivity of the cured product of the thermosoftening thermal conductive composition, is preferably 4.0 W / m·K or more, more preferably 6.0 to 20.0 W / m·K. If the thermal conductivity is within this range, it is easy to maintain the high-level thermal conductivity between the electronic component and the heat dissipation component such as the radiator, and it is easy to fully exhibit the heat dissipation performance.

[0134] The thermal conductivity is the value calculated from the thermal resistance measured by the laser flash method and the thickness of the cured product.

[0135] Furthermore, for the thermosoftening thermal conductive composition used in the sheet-like heat dissipation member of the present invention, its viscosity at 80°C is preferably in the range of 0.5×10 2 ~1×10 5 Pa·s, more preferably in the range of 1.5×10 2 ~5×10 4 Pa·s. If the viscosity is within this range, it is difficult for the heat dissipation member to flow out between the electronic component and the heat dissipation component such as the radiator, and it is easy to reduce the gap between the electronic component and the heat dissipation component, and it is easy to fully exhibit the heat dissipation performance.

[0136] The viscosity at 80°C is the value measured by the dynamic viscoelasticity measuring device RDA3 (manufactured by TA Instruments Inc.).

[0137] [Manufacturing method of thermal conductive composite]

[0138] The sheet-like heat dissipation member of the present invention can form a thermal conductive composite with improved operability and insulation by laminating with an arbitrary reinforcing layer (X). As the reinforcing layer, a synthetic resin film layer with excellent heat resistance and electrical insulation, and at the same time soft and high mechanical strength is preferred, and it can also be appropriately selected and used from known base materials.

[0139] The synthetic resin film layer usually has a thickness of 2 to 20 μm, preferably in the range of 5 to 15 μm. If the synthetic resin film layer is too thick, it will hinder the thermal conductivity of the composite of the present invention. On the contrary, if the synthetic resin film layer is too thin, the strength that should be exerted as the reinforcing layer is insufficient, and there may be a case where the withstand voltage characteristics deteriorate and the electrical insulation performance becomes insufficient. Further, the synthetic resin film layer is preferably a film layer without holes that reduce the withstand voltage characteristics.

[0140] Examples of the synthetic resin include, for example, aromatic polyimide resins; polyamide resins; polyamideimide resins; polyester resins such as polyethylene naphthalate; and fluororesins such as polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers. When using the above fluororesin as the synthetic resin, from the viewpoint of improving adhesiveness, it is preferable to subject the surface of the used film to chemical etching treatment with a sodium / naphthalene-based treatment liquid.

[0141] In order not to reduce the mechanical strength due to thermal deformation, the synthetic resin film is particularly preferably a heat-resistant film having a melting point of 200°C or higher, preferably 250°C or higher. Examples of the synthetic resin film having a heat resistance with a melting point of 250°C or higher include, for example, Kapton (registered trademark) MT (trade name, manufactured by DU PONT-TORAY CO., LTD.), which is an aromatic polyimide-based film.

[0142] The manufacturing method of the heat-conductive composite of the present invention is a manufacturing method in which the sheet-like heat dissipation member is used as the outer layer and laminated on both sides of the reinforcing layer (X) by room-temperature press bonding or hot press bonding. There is no particular limitation on the lamination method, and it can be appropriately carried out according to the conventionally known manufacturing method of the composite.

[0143] In the case of room-temperature press bonding, for example, the sheet-like heat dissipation member previously formed on the above-mentioned separator film can be transferred to both sides of the reinforcing layer (X). In the case of hot press bonding, the pressing jig is heated to 40 to 80°C and similarly press-bonded and transferred. In addition to pressing and bonding, roll bonding or the like can also be used for bonding. In addition, the composite can also be manufactured by applying a diluted product obtained by diluting the composition of the heat dissipation member with a solvent to both sides of the reinforcing layer (X) and drying it.

[0144] The sheet-like heat dissipation member or the heat-conductive composite of the present invention is disposed between the heat-generating electronic component that can reach a temperature higher than room temperature due to operation and the heat dissipation component, is non-flowable under room-temperature conditions, and is fluidized by the heat released during the operation of the electronic component or by actively heating during the configuration of the electronic component, so that it can be filled substantially without gaps at the junction between the electronic component and the heat dissipation component.

[0145] Examples

[0146] Hereinafter, examples and comparative examples are shown to explain the present invention in more detail, but the present invention is not limited to the following examples.

[0147] The components (A) to (D) used in the following examples and comparative examples are as described below.

[0148] (A) Silicone resin

[0149] (A-1) D25 T Φ 55 D Vi 20 (Weight-average molecular weight: 3300 in terms of polystyrene, solid at 25°C, softening point: 40 - 50°C)

[0150] Among them, D represents a dimethylsiloxane unit (i.e., (CH3)2SiO 2 / 2 ) and T Φ represents a phenylsiloxane unit (i.e., (C6H5)SiO 3 / 2 ), and D Vi represents a methylvinylsiloxane unit (i.e., (CH3)(CH2=CH)SiO 2 / 2 ).

[0151] (A-2) M2T Φ 50 (Weight-average molecular weight: 3100 in terms of polystyrene, solid at 25°C, softening point: 40 - 50°C)

[0152] Among them, M represents a trimethylsiloxane unit (i.e., (CH3)3SiO 1 / 2 ), and T Φ represents a phenylsiloxane unit (i.e., (C6H5)SiO 3 / 2 ).

[0153] (A-3) M2D 20 Q 40 D Vi 20 (Weight-average molecular weight: 3700 in terms of polystyrene, solid at 25°C, softening point: 40 - 50°C)

[0154] Among them, M represents a trimethylsiloxane unit (i.e., (CH3)3SiO 1 / 2 ), D represents a dimethylsiloxane unit (i.e., (CH3)2SiO 2 / 2 ), Q represents SiO 4 / 2 , and D Vi represents a methylvinylsiloxane unit (i.e., (CH3)(CH2=CH)SiO 2 / 2 ).

[0155] (B) Thermal conductivity filler

[0156] (B-1-1) Spherical alumina with an average particle size of 2 μm

[0157] (B-1-2) Spherical alumina with an average particle size of 50 μm

[0158] (B-2-1) Fragmented aluminum nitride with an average particle size of 2 μm (specific surface area: 3.2 m 2 / g)

[0159] (B-2-2) Fragmented aluminum nitride with an average particle size of 30 μm (specific surface area: 2.0 m 2 / g)

[0160] (B-2-3) Fragmented aluminum nitride with an average particle size of 0.5 μm (specific surface area: 5.6 m 2 / g, for comparative example)

[0161] (C) Alkylalkoxysilane (wetting agent component)

[0162] Alkylalkoxysilane represented by the following formula

[0163] C 10 H 21 Si(OCH3)3

[0164] (D) Other additives: silicone oil

[0165] Linear silicone oil containing phenyl with a viscosity of 0.4 Pa·s at 25°C (trade name: KF-54, manufactured by Shin-Etsu Chemical Co., Ltd., Japan)

[0166] An even composition was obtained by charging the above components (A), (B), (C), and (D) into a planetary mixer in the blending amounts described in Table 1 or Table 2 below and mixing for 60 minutes.

[0167] [Manufacture of sheet]

[0168] A toluene solution obtained by adding an appropriate amount of toluene to the composition obtained above was coated on a fluorine-modified silicone release film (a PET substrate surface-treated with a release agent X-41-3035 (manufactured by Shin-Etsu Chemical Co., Ltd., Japan), hereinafter referred to as the release film), heated to 80°C to volatilize toluene, and a composition layer with a thickness of 200 μm was formed on the release film. Further, by overlapping another release film on the composition layer in a manner of contacting the release agent-treated surface for protection, a sheet having a composition layer between two release films was obtained. It should be noted that the thickness of 200 μm is only the thickness of the composition layer and does not include the thickness of the release film.

[0169] [Lamination with reinforcing layer (manufacture of composite)]

[0170] Similar to the production of the above-mentioned sheet, a toluene solution of the composition was coated on a separator film and heated to 80 °C to volatilize the toluene, thereby producing a sheet having a composition layer with a thickness of 100 μm formed on the separator film. Two sheets were produced for each of the examples and comparative examples, and the two sheets were respectively arranged on both sides of an aromatic polyimide film (thickness: 5 μm) in contact with the composition layer, and a composite was formed by pressing at 70 °C.

[0171] The thickness of the composition layer in the composite is shown in Table 1. The size of the composite is 200×300 mm.

[0172] [Evaluation method]

[0173] (1) Operability: The operability of the heat dissipation component (aluminum radiator) was evaluated based on whether the desired adhesion could be obtained when pasting the sheet or composite.

[0174] After peeling off the separator film on one side and attaching the composition layer of the sheet or composite to the aluminum radiator, when peeling off the separator film on the other side, the evaluation was made based on whether the attached sheet or composite shifted from the aluminum radiator or was fixed without breaking.

[0175] Those that could be fixed without shifting or breaking were evaluated as ○; those with shifting or breaking were evaluated as × and recorded in the table.

[0176] (2) Thermal conductivity: The sheet or composite with the separator films peeled off on both sides was sandwiched between aluminum plates, pressed at 50 psi, and then heated and cured in a dryer at 150 °C for 1 hour. The thermal resistance of the obtained cured product was measured by the laser flash method. The thermal conductivity was calculated from the relationship between the thickness and thermal resistance of the cured product.

[0177] (3) Reliability (thermal conductivity after high temperature and high humidity): The test samples used for the above thermal conductivity measurement were aged for 500 hours under high temperature and high humidity conditions of 85 °C / 85% Rh, and then the thermal resistance was measured again by the laser flash method to calculate the thermal conductivity.

[0178] (4) Dielectric breakdown voltage: Based on the method described in JIS K6249:2003, the dielectric breakdown voltage of the sheet or composite with the separator films peeled off on both sides was measured.

[0179] The above evaluation results are recorded in Tables 1 - 2.

[0180] [Table 1]

[0181]

[0182] [Table 2]

[0183] Comparative Example 1 2 3 4 5 A-1 100 100 100 100 100 B-1-1 90 400 1000 220 B-1-2 90 400 500 220 B-2-1 360 1200 250 800 B-2-2 360 2000 250 1400 B-2-3 1760 C 8 13 10 10 13 D 7 7 7 7 7 Reinforcing layer None None None None None Total of Component B 900 4000 2000 2200 2200 (B-1) / (B-2) 1 / 4 1 / 4 3 / 1 0 / 1 1 / 4 Thickness of composition layer (μm) 200 200 200 200 200 (1) Workability ○ × ○ ○ ○ (2) Thermal conductivity (W / m·K) 3.9 ND 4.8 8.0 7.5 (3) Thermal conductivity after high-temperature and high-heat durability (W / m·K) 4.5 ND 4.8 7.8 5.1 (4) Dielectric breakdown voltage (kV) 3.9 ND 3.6 3.2 2.7

[0184] Regarding Examples 1 to 12, the moldings (sheets or composites) have excellent workability (adhesion to the heat dissipation member), exhibit good thermal conductivity and dielectric breakdown voltage as heat dissipation members, and there is no significant change in the thermal conductivity after high temperature and high humidity compared to the initial value of the thermal conductivity. They are heat dissipation members with excellent reliability.

[0185] On the other hand, in Comparative Example 1, since the total amount of the heat-conductive filler as the (B) component is less than 1200 parts by mass relative to 100 parts by mass of the (A) component, the molding (sheet) could not obtain the desired thermal conductivity.

[0186] In Comparative Example 2, since the total amount of the heat-conductive filler as the (B) component is more than 3500 parts by mass relative to 100 parts by mass of the (A) component, the molding (sheet) becomes brittle, is difficult to operate, and it is impossible to evaluate the measurement items other than workability.

[0187] In Comparative Example 3, since the ratio of the (B-1) component / (B-2) component as the (B) component exceeds the range of 1 / 1, the thermal conductivity of the molding (sheet) decreases.

[0188] In Comparative Example 4, since the (B-1) component is not contained and the ratio of the (B-1) component / (B-2) component of the (B) component is less than the range of 1 / 9, compared with Example 1, the heat conductivity cannot be effectively improved, resulting in a decrease in the thermal conductivity of the molding (sheet).

[0189] In Comparative Example 5, since aluminum nitride with a specific surface area exceeding 4.0 m 2 / g is used, when the molding is subjected to long-term aging treatment under high temperature and high humidity conditions, a decrease in thermal conductivity and a decrease in reliability can be seen.

Claims

1. A sheet-like heat dissipation member having a composition layer composed of a heat-softening thermally conductive composition, the heat-softening thermally conductive composition containing: (A) Silicone resin that is solid at 25 °C: 100 parts by mass, the silicone resin having 20 mol% or more of one or more siloxane units selected from R 1 SiO 3 / 2 units and SiO 4 / 2 units, wherein R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, and (B) A thermally conductive filler containing the following (B-1) and (B-2): 1200 to 3500 parts by mass, (B-1) Alumina having an average particle diameter of 0.1 to 70 μm: 120 to 1750 parts by mass, and (B-2) Aluminum nitride with an average particle size of 0.1 to 70 μm and a specific surface area of 4.0 m 2 / g or less: 600 to 2880 parts by mass, wherein the blending ratio of (B-1) to (B-2) is (B-1) / (B-2) = 1 / 9 to 1 / 1 by mass ratio.

2. The sheet-like heat dissipation member according to claim 1, wherein, The component (A) also has R 1 2SiO 2 / 2 units, where R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms.

3. The sheet-like heat dissipation member according to claim 1 or claim 2, wherein, the heat-softening thermally conductive composition further includes: (D) A linear organopolysiloxane having a viscosity of 0.1 to 100 Pa·s at 25°C, having one or more aryl groups having 6 to 12 carbon atoms in one molecule, and being 1 to 30 parts by mass relative to 100 parts by mass of the component (A).

4. The sheet-like heat dissipation member according to claim 1, wherein, the component (B-1) is spherical alumina.

5. The sheet-like heat dissipation member according to claim 1, wherein, the heat-softening thermally conductive composition further includes: (C) An alkylalkoxysilane represented by the following general formula (1), which is 1 to 20 parts by mass relative to 100 parts by mass of the component (A), R 2 a R 3 b Si(OR 4 ) 4-a-b (1) In formula (1), R 2 is an alkyl group having 6 to 15 carbon atoms, R 3 is a monovalent hydrocarbon group having 1 to 4 carbon atoms, R 4 is an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, wherein a + b is an integer of 1 to 3.

6. The sheet-like heat dissipation member according to claim 1, wherein, the thermal conductivity of the cured product of the heat-softening thermally conductive composition is 4.0 W / m·K or more.

7. The sheet-like heat dissipation member according to claim 1, wherein, the thickness of the composition layer is 50 to 300 μm.

8. The sheet-like heat dissipation member according to claim 1, wherein, the insulation breakdown voltage measured by the method described in JIS K6249:2003 is 1 kV or more.

9. A thermally conductive composite, wherein, it is formed by disposing the sheet-like heat dissipation member according to claim 1 on both sides of a reinforcing layer X made of a thermoplastic resin.

10. The thermally conductive composite according to claim 9, wherein, the thermoplastic resin is any one of an aromatic polyimide resin, a polyamide resin, a polyamideimide resin, a polyester resin, and a fluororesin.

11. The thermally conductive composite according to claim 9 or claim 10, wherein, the thickness of the reinforcing layer X is 2 to 20 μm.

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