JP2016219738A - Heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-weight heat sink excellent in heat dissipation that radiates heat as infrared radiation from an external surface of a radiation fin by transmitting heat to every corner of the radiation fin after transmitting the heat with a heat pipe from a heat generating electronic component through a base plate.SOLUTION: In the heat sink including a base plate 1, a heat pipe 2, and a radiation fin 3, a graphite sheet formed by impregnating hole parts of a porous graphite sheet with silicone resin or a curable silicone rubber composition followed by curing is used as the radiation fin 3.SELECTED DRAWING: Figure 1

Description

  In the present invention, heat from an exothermic electronic component is transferred by a heat pipe through a base plate, and then the pores of a porous graphite sheet are impregnated with a silicone resin or cured with a curable silicone rubber composition. The present invention relates to a heat sink that is transmitted to all ends of a heat radiating fin made of a graphite sheet and radiates heat from the outer surface of the heat radiating fin as infrared rays and has excellent heat dissipation.

  LSI chips such as CPUs, driver ICs, and memories used in electronic devices such as personal computers will generate a large amount of heat with downsizing and high integration. Cause malfunction of the chip. Therefore, many heat radiating members have been proposed in order to suppress the temperature rise.

  However, as described above, although the power consumption is reduced due to the downsizing, thinning, and high performance of the device, the heat density of the heating element tends to increase. From the viewpoint of energy saving, the heat sink is also a natural energy source without power consumption. A cooling system is desired. However, the size and mass of the natural cooling type heat sink are regarded as problems. For example, weight reduction of a heat sink is calculated | required from the problem of a magnitude | size or mass, such as LED lighting assumed to suspend from a ceiling. For this reason, some reports have been made on reducing the weight of the heat sink.

  There is a method of changing the dimensions of a plurality of heat dissipating fins (Patent Document 1: Japanese Patent Laid-Open No. 2013-114413) or a method of forming slits or holes in a base plate (Patent Document 2: Japanese Patent Laid-Open No. 2013-135608). Proposed. However, sufficient heat dissipation characteristics may not be obtained by simply changing the shape of the fin and the shape of the base plate without changing the material.

In addition, a method of applying an alumite treatment or a radiation coating to the heat dissipating fin has been proposed (Patent Document 3: Japanese Patent Laid-Open No. 2014-41929). However, there are cases where sufficient heat dissipation characteristics cannot be obtained even with alumite treatment with improved radiation characteristics of the material or a method of applying a radiation paint.
In addition, the following literature is mentioned with the literature mentioned above as a prior art relevant to this invention.

JP 2013-114413 A JP 2013-135608 A JP 2014-41929 A JP 2014-192401 A

  The present invention has been made in view of the above circumstances. After heat from a heat-generating electronic component is transmitted through a base plate by a heat pipe, it is transmitted to the ends of the radiation fins, and infrared rays are transmitted from the outer surface of the radiation fins. An object of the present invention is to provide a heat sink that emits heat and is lightweight and excellent in heat dissipation.

  As a result of intensive studies to achieve the above object, the present inventor, as a radiating fin, impregnated with a silicone resin in a pore portion of a porous graphite sheet or impregnated with a curable silicone rubber composition and then cured. By using the sheet, the heat from the heat-generating electronic component is transmitted through the base plate by the heat pipe, and then is conducted well to the heat radiating fin, and the heat is radiated as infrared rays from the outer surface of the heat radiating fin. Thus, the present invention has been found to be a heat sink having excellent heat dissipation characteristics.

Accordingly, the present invention provides the following heat sink.
[1]
A heat sink comprising a base plate, a heat pipe, and a heat radiating fin, wherein the heat radiating fin is impregnated with a silicone resin in a pore portion of a porous graphite sheet or impregnated with a curable silicone rubber composition and then cured. A heat sink characterized by comprising a graphite sheet.
[2]
A curable silicone rubber composition impregnated in the pores of the porous graphite sheet is
(A) The following average composition formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
(In the formula, R ¹ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and a is a positive number of 1.8 to 2.2.)
An organopolysiloxane having two or more alkenyl groups bonded to a silicon atom represented by the formula:
(B) Organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule: moles of hydrogen atoms directly bonded to silicon atoms in component (b) relative to alkenyl groups in component (a) An amount such that the ratio is 0.5-5.0,
(C) Platinum group metal catalyst: 0.1 to 1,000 ppm with respect to the mass of component (a) in terms of mass of platinum group metal element, and (d) alkoxy group-containing organosilicon compound: 0.01 to 50 The heat sink according to [1], which is a curable silicone rubber composition containing parts by mass.
[3]
A curable silicone rubber composition to be impregnated into the pores of the porous graphite sheet,
(E) Oxide ceramics: The heat sink according to [2], which is a curable silicone rubber composition containing 2 to 200 parts by mass with respect to 100 parts by mass of the component (a).
[4]
A curable silicone rubber composition impregnated in the pores of the porous graphite sheet is
(F) The following average composition formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
(In the formula, R ¹ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and a is a positive number of 1.8 to 2.2.)
A curable silicone rubber containing 100 parts by mass of an organopolysiloxane having two or more alkenyl groups bonded to a silicon atom represented by the formula: and (g) an organic peroxide: 0.1 to 2 parts by mass The heat sink according to [1], which is a composition.
[5]
The heat sink according to [1], wherein the silicone resin impregnated in the pores of the porous graphite sheet is a thermosoftening silicone resin that is substantially solid at room temperature.
[6]
The thermosoftening silicone resin is composed of a bifunctional siloxane structural unit (D unit) and a trifunctional silsesquioxane structural unit (T unit), or a bifunctional siloxane structural unit (D unit) and a tetrafunctional structural unit ( The heat sink according to [5], wherein the heat sink contains Q units.
[7]
The heat sink according to any one of [1] to [5], wherein the porosity (volume%) of the porous graphite sheet is 30 to 80 vol%.
[8]
The heat sink according to any one of [1] to [6], wherein silicone grease is supplied to a gap existing in a connection portion between the base plate and the heat pipe.
[9]
The heat sink according to any one of [1] to [7], wherein silicone grease is supplied to a gap existing in a connection portion between the heat pipe and the heat radiating fin.

  The heat sink of the present invention is a lightweight heat sink with excellent heat dissipation, in which heat from the heat-generating electronic component is diffused to the base plate, the heat pipe, and the heat radiating fin and then radiated as infrared rays from the surface of the heat radiating fin.

It is the schematic of the heat sink which concerns on one Example of this invention.

Hereinafter, the heat sink of the present invention will be described in detail.
[heatsink]
As shown in FIG. 1, the heat sink of the present invention includes a base plate 1, a heat pipe 2 erected on the base plate 1, and a plurality of radiating fins 3 attached to the heat pipe 2. It will be. In this case, the silicone grease 4 is supplied to the gap existing in the connecting portion between the base plate 1 and the heat pipe 2 and the gap existing in the connecting portion between the heat pipe 2 and the heat radiating fin 3. .
The heat sink of the present invention, as a radiating fin, impregnates the pores (many micropores) of the porous graphite sheet with a silicone resin or impregnates a curable silicone rubber composition and cures the pores ( By using a graphite sheet in which a large number of micropores) are sealed with silicone resin or a cured silicone rubber, heat from the heat-generating electronic components is transmitted through the base plate via the heat pipe and then to the ends of the heat dissipation fins. This heat can be transmitted, and this heat can be radiated as infrared rays from the surface of the radiating fin.

[Base plate]
The base plate used for the heat sink of the present invention is not particularly limited, but is preferably a material having high thermal conductivity, preferably a copper plate, an aluminum plate, or a graphite sheet (porous graphite sheet), and more preferably a copper plate.

[heat pipe]
The heat pipe used for the heat sink of the present invention is not particularly limited, but a heat pipe in which pure water, alcohol or the like is sealed as hydraulic oil in a metal tubular container having high thermal conductivity is preferably used. The material of the tubular container is preferably copper or aluminum, and more preferably copper. Water is preferred as the hydraulic oil.

[Heat radiation fins]
Next, in the heat sink of the present invention, the heat radiating fins are obtained by impregnating the pores of the porous graphite sheet with a silicone resin or impregnating a curable silicone rubber composition and curing the heat radiating fins. A porous graphite sheet, a curable silicone rubber composition, and a silicone resin used in the present invention will be described.

[Porous graphite sheet]
Any porous graphite sheet can be used as long as it has porosity. In this case, it is preferable that the porosity (volume%) is 30 to 80 vol%, particularly 40 to 70 vol%. In addition, this porosity can be normally calculated | required by the gas displacement method, the submerged weighing method, etc.
As the porous graphite sheet, for example, one produced by a method such as pyrolyzing a polymer film to be graphitized can be used, and a commercially available product can be used. Examples of commercially available products include MACFOIL (manufactured by Japan Matex Co., Ltd .: trade name) and PGS graphite sheet (manufactured by Panasonic Corporation: trade name).

  The thickness of the porous graphite sheet is preferably in the range of 3 to 500 μm, more preferably in the range of 5 to 200 μm. If it is less than 3 μm, the strength may be insufficient, and it may be damaged because it is brittle. Those exceeding 500 μm are difficult to manufacture and are economically disadvantageous.

[Curable silicone rubber composition]
In the heat sink of the present invention, as the curable silicone rubber composition used to form the radiation fin, for example,
(A) The following average composition formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
(In the formula, R ¹ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and a is a positive number of 1.8 to 2.2.)
An organopolysiloxane having two or more alkenyl groups bonded to a silicon atom represented by the formula:
(B) Organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule: moles of hydrogen atoms directly bonded to silicon atoms in component (b) relative to alkenyl groups in component (a) An amount such that the ratio is 0.5-5.0,
(C) Platinum group metal catalyst: 0.1 to 1,000 ppm of component (a) in terms of mass of platinum group metal element, and (d) alkoxy group-containing organosilicon compound: 0.01 to 50 parts by mass In addition to the curable silicone rubber composition and the blending amounts of the components (a) to (d),
(E) Oxide ceramics: Preferable examples include curable silicone rubber compositions containing 2 to 200 parts by mass.

Below, each component of the said curable silicone rubber composition is demonstrated.
[(A) Organopolysiloxane having an alkenyl group]
The alkenyl group-containing organopolysiloxane as component (a) has the following average composition formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
Wherein R ¹ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and a is a positive value of 1.8 to 2.2, preferably 1.95 to 2.05. Number.)
An organopolysiloxane having 2 or more, preferably 2 to 100, more preferably about 2 to 50 alkenyl groups bonded to silicon atoms represented by general formula (II), and an addition reaction curing type curable silicone rubber It is the main agent (base polymer) in the composition. Normally, both ends of the molecular chain are blocked with a triorganosiloxy group (R ¹ ₃ SiO _1/2 (R ¹ is the same as above, the same shall apply hereinafter)), and the main chain portion is basically a diorganosiloxane unit (R ¹ ₂ SiO _2/2 ) is generally a linear structure, which may include a branched structure in a part of the molecular structure, or a cyclic structure. However, linear diorganopolysiloxane is preferable from the viewpoint of physical properties such as mechanical strength of the cured product.

In the above formula (1), R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, particularly 1 to 10 carbon atoms, which are the same or different from each other, and a function other than an alkenyl group bonded to a silicon atom. Examples of the group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, Alkyl groups such as dodecyl group, cycloalkyl groups such as cyclopentyl group, cyclohexyl group, cycloheptyl group, aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, biphenylyl group, benzyl group, phenylethyl group, phenylpropyl Groups, aralkyl groups such as methylbenzyl groups, and one of the hydrogen atoms to which the carbon atoms of these groups are bonded. Or a group in which all of them are substituted with a halogen atom such as fluorine, chlorine or bromine, a cyano group, for example, a chloromethyl group, a 2-bromoethyl group, a 3-chloropropyl group, a 3,3,3-trifluoropropyl group Chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group, etc., and typical ones having 1 to 10 carbon atoms. Particularly typical are those having 1 to 6 carbon atoms, preferably methyl, ethyl, propyl, chloromethyl, bromoethyl, 3,3,3-trifluoropropyl, cyanoethyl. And an unsubstituted or substituted alkyl group having 1 to 3 carbon atoms, and an unsubstituted or substituted phenyl group such as a phenyl group, a chlorophenyl group, and a fluorophenyl group. Moreover, all the functional groups other than the alkenyl group bonded to the silicon atom may be the same or different.

  Examples of the alkenyl group include those having about 2 to 8 carbon atoms such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group and cyclohexenyl group. And lower alkenyl groups such as an allyl group are preferable, and a vinyl group is particularly preferable. The alkenyl group may be bonded to the silicon atom at the end of the molecular chain, may be bonded to the silicon atom at the non-terminal end of the molecular chain (in the middle of the molecular chain), or both. It preferably contains at least alkenyl groups bonded to silicon atoms at both ends of the molecular chain.

  The viscosity of this organopolysiloxane at 25 ° C. is usually in the range of 10 to 100,000 mPa · s, particularly preferably in the range of 500 to 50,000 mPa · s. If the viscosity is too low, the storage stability of the resulting composition may deteriorate, and if it is too high, the extensibility of the obtained composition may deteriorate. In the present invention, the viscosity can be measured with a rotational viscometer (for example, BL type, BH type, BS type, cone plate type, rheometer, etc.). The above-mentioned viscosity usually corresponds to about 10 to 1,100, particularly about 50 to 800 in terms of number average polymerization degree in the case of linear organopolysiloxane.

  The organopolysiloxane having an alkenyl group as component (a) may be used alone or in combination of two or more having different viscosities.

[(B) Organohydrogenpolysiloxane]
The organohydrogenpolysiloxane as the component (b) has 2 or more, preferably 2 to 200, more preferably about 3 to 100, hydrogen atoms bonded to silicon atoms (that is, SiH groups) in one molecule. It is an organohydrogenpolysiloxane and is a component that acts as a crosslinking agent (curing agent) for the component (a). That is, in the presence of a platinum group metal catalyst which is component (c) described later, a hydrogen atom bonded to a silicon atom in component (b) is added to an alkenyl group in component (a) by a hydrosilylation reaction. Then, a crosslinked cured product (silicone rubber cured product) having a three-dimensional network structure having a crosslinked bond is generated.

  Examples of the organic group bonded to the silicon atom in the component (b) include an unsubstituted or substituted monovalent hydrocarbon group that does not have an aliphatic unsaturated bond. Specifically, unsubstituted or substituted, similar to those exemplified as the unsubstituted or substituted monovalent hydrocarbon group bonded to the silicon atom other than the aliphatic unsaturated group such as the alkenyl group described in the component (a) Among them, a methyl group is preferable from the viewpoint of ease of synthesis and economy.

  The structure of the organohydrogenpolysiloxane of component (b) in the present invention is not particularly limited, and may be any of linear, branched, cyclic and three-dimensional network structures, preferably linear. .

  The degree of polymerization of the organohydrogenpolysiloxane (or the number of silicon atoms) is usually preferably from 2 to 200, particularly from 2 to 100, and particularly from about 2 to 50. In the present invention, the degree of polymerization (or molecular weight) can be determined, for example, as the number average degree of polymerization (or number average molecular weight) in terms of polystyrene in gel permeation chromatography (GPC) analysis using toluene as a developing solvent.

Preferred examples of the organohydrogenpolysiloxane of component (b) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris (hydro Dimethyldimethylsiloxy) methylsilane, tris (hydrogendimethylsiloxy) phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, trimethylsiloxy group-blocked methylhydrogenpolysiloxane, molecular chain Trimethylsiloxy group-capped dimethylsiloxane / methylhydrogensiloxane copolymer, both ends of chain chain Trimethylsiloxy group-capped dimethylsiloxane / methylhydrogensiloxane / methylphenylsiloxy Copolymer, dimethylhydrogensiloxy group-blocked dimethylpolysiloxane at both ends of the molecular chain, dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer at both ends of the molecular chain, dimethylhydrogensiloxy group-blocked at both ends of the molecular chain Dimethylsiloxane / methylphenylsiloxane copolymer, dimethylhydrogensiloxy group-blocked methylphenylpolysiloxane with both molecular chains, (CH ₃ ) ₂ HSiO _1/2 units and (CH ₃ ) ₃ SiO _1/2 units and SiO _{4 / A} copolymer comprising ₂ units, a copolymer comprising (CH ₃ ) ₂ HSiO _1/2 units and SiO _4/2 units, (CH ₃ ) ₂ HSiO _1/2 units and SiO _4/2 units ( Examples thereof include copolymers composed of C ₆ H ₅ ) ₃ SiO _1/2 units.
The (b) component organohydrogenpolysiloxane may be used singly or in combination of two or more.

  The amount of component (b) is preferably such that the SiH group in component (b) is 0.5 to 5.0 moles per mole of alkenyl group in component (a). Is an amount of 0.8 to 4.0 mol. When the amount of SiH groups in the component (b) is less than 0.5 mol with respect to 1 mol of the alkenyl groups in the component (a), the composition does not cure or the strength of the cured product is insufficient, Problems such as being unable to be handled as a molded body or a composite body may occur. On the other hand, when an amount exceeding 5.0 mol is used, it may be difficult to combine with the porous graphite sheet.

[(C) Platinum group metal catalyst]
The platinum group metal catalyst of component (c) promotes the addition reaction between the alkenyl group in component (a) and the hydrogen atom bonded to the silicon atom in component (b), and the curable silicone rubber composition of the present invention. It is a catalyst component blended to convert the product into a crosslinked cured product (silicone rubber cured product) having a three-dimensional network structure.

The component (c) can be appropriately selected from known catalysts used in ordinary hydrosilylation addition reactions. Specific examples thereof include platinum group metals such as platinum (including platinum black), rhodium and palladium, H ₂ PtCl ₄ · xH ₂ O, H ₂ PtCl ₆ · xH ₂ O, NaHPtCl ₆ · xH ₂ O. , KHPtCl ₆ · xH ₂ O, Na ₂ PtCl ₆ · xH ₂ O, K ₂ PtCl ₄ · xH ₂ O, PtCl ₄ · xH ₂ O, PtCl ₂ , Na ₂ HPtCl ₄ · xH ₂ O (wherein x is an integer of 0 to 6, preferably 0 or 6.), etc.), etc.) Platinum chloride, chloroplatinic acid and chloroplatinate, alcohol-modified chloroplatinic acid, complex of chloroplatinic acid and olefin, platinum black , Platinum group metals such as palladium supported on alumina, silica, carbon, etc., rhodium-olefin complex, chlorotris (triphenylphosphine) rhodium (Wilkin) (Son catalyst), platinum chloride, chloroplatinic acid, a complex of chloroplatinate and a vinyl group-containing siloxane, and the like.
These platinum group metal catalysts may be used singly or in combination of two or more.

  The compounding amount of the platinum group metal catalyst of the component (c) may be an effective amount necessary for curing the composition, but is usually in terms of mass of the platinum group metal element with respect to the component (a), 0.1 to 1,000 ppm, preferably 0.5 to 500 ppm.

[(D) Alkoxy group-containing organosilicon compound]
The alkoxy group-containing organosilicon compound (d) serves as a surface treating agent for the purpose of wettability between the curable silicone rubber composition and the porous graphite sheet.

  The component (d) is preferably an organoxysilane compound or a linear diorganopolysiloxane having a molecular chain fragment end blocked with a triorganoxysilyl group. Particularly, the following (d-1) and (d- 2) Component is preferred.

(D-1): alkoxysilane compound represented by the following general formula (2) R ² _c R ³ _d Si (OR ⁴ ) _4-cd (2)
Wherein R ² is independently an alkyl group having 6 to 15 carbon atoms, R ³ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and R ⁴ is independently carbon atoms. 1 to 6 alkyl groups, c is an integer of 1 to 3, d is 0, 1 or 2, and c + d is an integer of 1 to 3.)

Examples of the alkyl group represented by R ² in the general formula (2) include a hexyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, and a tetradecyl group. Thus, when the number of carbon atoms of the alkyl group represented by R ^{2 is} in the range of 6 to 15, particularly 8 to 12, the wettability with the porous graphite sheet is sufficiently improved and the handling workability is improved. Therefore, the low temperature characteristics of the composition are good.

Examples of the unsubstituted or substituted monovalent hydrocarbon group represented by R ³ include alkyl groups such as a methyl group, an ethyl group, a propyl group, a hexyl group, and an octyl group; a cyclopentyl group, a cyclohexyl group, and the like. Cycloalkyl group; alkenyl group such as vinyl group and allyl group; aryl group such as phenyl group and tolyl group; aralkyl group such as 2-phenylethyl group and 2-methyl-2-phenylethyl group; Examples thereof include halogenated hydrocarbon groups such as a trifluoropropyl group, 2- (nonafluorobutyl) ethyl group, 2- (heptadecafluorooctyl) ethyl group, and p-chlorophenyl group. In the present invention, among these, a methyl group and an ethyl group are particularly preferable.

Examples of the alkyl group represented by R ⁴ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. In the present invention, among these, a methyl group and an ethyl group are particularly preferable.

Preferable specific examples of the component (d-1) include the following.
C ₆ H ₁₃ Si (OCH ₃ ) ₃
C ₁₀ H ₂₁ Si (OCH ₃ ) ₃
C ₁₂ H ₂₅ Si (OCH ₃ ) ₃
C ₁₂ H ₂₅ Si (OC ₂ H ₅ ) ₃
C ₁₀ H ₂₁ Si (CH ₃ ) (OCH ₃ ) ₂
C ₁₀ H ₂₁ Si (C ₆ H ₅ ) (OCH ₃ ) ₂
C ₁₀ H ₂₁ Si (CH ₃ ) (OC ₂ H ₅ ) ₂
C ₁₀ H ₂₁ Si (CH═CH ₂ ) (OCH ₃ ) ₂
C ₁₀ H ₂₁ Si (CH ₂ CH ₂ CF ₃ ) (OCH ₃ ) ₂

  The component (d-1) may be used alone or in combination of two or more.

(D-2): linear dimethylpolysiloxane in which one molecular chain end represented by the following general formula (3) is blocked with a trialkoxysilyl group
(In the formula, R ⁵ is independently an alkyl group having 1 to 6 carbon atoms, and examples thereof are the same as the alkyl group represented by R ⁴ in the above formula (2). k is an integer of 5 to 100, preferably 10 to 50.)

Preferable specific examples of the component (d-2) include the following.

  In addition, (d-2) component may be used individually by 1 type, or may be used in combination of 2 or more type.

In the present invention, at least one selected from the group consisting of the component (d-1) and the component (d-2) can be selected and used. In this case, in the curable silicone rubber composition, the blending amount of all the components (d) is preferably 0.01 to 50 parts by mass, particularly 0.1 to 30 parts per 100 parts by mass of the component (a). It is preferable that it is a mass part.
Even if the blending amount of the component (d-1) exceeds the above blending amount, the wetter effect does not increase any more, which is uneconomical. Moreover, since this (d-1) component has volatility, when it is left to stand in an open system, the composition and the cured product after curing are gradually hardened. Moreover, when the compounding quantity of (d-2) component exceeds the said compounding quantity, there exists a tendency for the heat resistance and moisture resistance of the hardened | cured material obtained to fall.

[(E) Oxide ceramics]
To the curable silicone rubber composition of the present invention, an oxide ceramic as the component (e) may be added as an optional component for the purpose of improving thermal radiation. Examples of oxide ceramics include metal oxide powders such as aluminum oxide powder, zinc oxide powder, magnesium oxide powder, iron oxide powder, titanium oxide powder, zirconium oxide powder, and silicon dioxide powder.
These may be used alone or in combination of two or more.

The volume average particle diameter of the oxide ceramics, the value measured by Microtrac particle size distribution analyzer MT3300EX (trade name manufactured by Nikkiso Co., Ltd.) by a laser diffraction scattering method (Microtrac method) (usually, the cumulative weight average diameter D ₅₀ or The median diameter is preferably 0.01 to 10 μm, and more preferably 0.05 to 5 μm. If it is less than 0.01 μm, the handleability may be difficult. If it exceeds 10 μm, it may be difficult to develop sufficient heat radiation performance.

  (E) When mix | blending the oxide ceramics of a component, the compounding quantity is 2-200 mass parts normally with respect to 100 mass parts of alkenyl group containing organopolysiloxane of (a) component, Preferably it is 5-5. It is desirable that the amount is 100 parts by mass, more preferably about 10 to 70 parts by mass. In addition, it is preferable that the content rate of the oxide ceramics of (e) component is about 2-50 mass% with respect to the total mass of a curable silicone rubber composition, and it is about 5-20 mass%. More preferred. When the blending amount (or content ratio in the composition) of the oxide ceramic is too small, the improvement in thermal radiation of the radiation fins may be small, and when the blending amount (or content ratio in the composition) is too large. A uniform heat radiation fin may not be obtained.

[Curable silicone rubber composition]
Moreover, in the heat sink of the present invention, as another aspect of the curable silicone rubber composition used for forming the radiation fins, for example,
(F) Organopolysiloxane having two or more alkenyl groups in one molecule: 100 parts by mass and (g) Organic peroxide: 0.1 to 2 parts by mass Curing of organic peroxide curing type Mention may be made of silicone rubber compositions.

Below, each component of the said curable silicone rubber composition is demonstrated.
[(F) Organopolysiloxane having two or more alkenyl groups in one molecule]
Examples of the organopolysiloxane having two or more alkenyl groups in the molecule (f) are the same as the alkenyl group-containing organopolysiloxane of the component (a) described above.

[(G) Organic peroxide]
The curing reaction of the silicone rubber composition with the organic peroxide has an alkenyl group such as a vinyl group at one or both of the molecular chain terminal (one terminal or both terminals) and the molecular chain non-terminal (middle molecular chain). This is caused by radical polymerization of a linear organopolysiloxane in the presence of an organic peroxide. Examples of the organic peroxide as the component (g) include diacyl peroxide and dialkyl peroxide. Organic peroxides are vulnerable to light and heat, are unstable, and it is difficult to disperse solid organic peroxides in the composition, so they can be diluted in organic solvents or dispersed in silicone components. It is often used in the

  The compounding amount of the organic peroxide as the component (g) may be a so-called catalytic amount, and is usually about 0.1 to 2 parts by mass with respect to 100 parts by mass of the alkenyl group-containing organopolysiloxane as the component (f). preferable.

  In addition to the above-mentioned components (f) and (g), the above-described organic peroxide-curable curable silicone rubber composition can further contain the above-described components (d) and (e). In this case, it is preferable that the compounding quantity in the case of mix | blending (d) component is 0.01-50 mass parts with respect to 100 mass parts of (f) component, and it is 0.1-30 mass parts. More preferred. Moreover, it is preferable that the compounding quantity in the case of mix | blending (e) component is 2-200 mass parts with respect to 100 mass parts of (f) component, More preferably, it is 5-100 mass parts, More preferably, it is. It is about 10-70 mass parts.

[Preparation of curable silicone rubber composition]
In the curable silicone rubber composition, the above components are mixed uniformly at room temperature (25 ° C. ± 5 ° C.) for 0.5 to 5 hours, particularly about 1 to 3 hours using a mixer such as a planetary mixer. Can be prepared.

[Silicone resin impregnated in the pores of the porous graphite sheet]
In the heat sink of the present invention, the silicone resin impregnated in the pores of the porous graphite sheet of the radiating fin is, for example, substantially solid (that is, self-flowing) at room temperature (25 ° C. ± 5 ° C.) as described below. Non-liquid material) or a heat softening silicone resin blend in which a heat conductive filler is dispersed and contained.
Here, the heat softening property means heat softening, viscosity reduction or melting by heat (usually at 40 ° C. or higher), and heat softening, viscosity reduction or melting results in fluidization of the surface. It can have "thermosoftening properties".

[Heat-softening silicone resin]
The heat-softening silicone resin or heat-softening silicone resin blend in which the heat-conductive filler is used in the present invention is substantially solid at room temperature (25 ° C. ± 5 ° C.) (ie, self-flowing). Non-liquid substance), usually at 40 ° C. or higher and below the maximum temperature achieved by heat generation of the heat-generating component, that is, in the temperature range of 40 to 120 ° C., particularly 40 to 90 ° C. Or what is necessary is just to melt | dissolve and at least a contact surface with an exothermic electronic component fluidizes.

  In the present invention, in particular, the softening point (or melting point) of the thermosoftening silicone resin is preferably 40 to 120 ° C, more preferably 45 to 100 ° C. Below 40 ° C, if the ambient temperature is high, the fluidity of the molded product may be remarkably exhibited and handling may be difficult. If it exceeds 120 ° C, the heat softening temperature may be high and molding may be difficult. . The softening point is determined by a falling ball type measurement method (that is, the temperature at which the falling ball completely sinks into the resin when the temperature of the resin is raised in a falling ball viscometer is used). Can do.

The heat-softening silicone resin or the heat-softening silicone resin composition in which the heat-conductive filler that is applied to the heat dissipating fin of the present invention is dispersed is not particularly limited as long as the above conditions are satisfied. The thermal softening property mentioned above is an important factor for the composition of the silicone resin.
In particular, as a heat softening silicone resin, a combination with a porous graphite sheet (that is, a heat softening silicone resin blended with a heat softening silicone resin or a heat conductive filler dispersed in pores of the porous graphite sheet) For example, a trifunctional silsesquioxy represented by a branched structural unit R′SiO _3/2 is required to be substantially solid at room temperature. Contains a sun structural unit (hereinafter referred to as T unit) and / or a tetrafunctional structural unit represented by SiO ₂ (hereinafter referred to as Q unit) as a main component (for example, 40 mol% or more, particularly 50 mol% or more). it silicone resin (so-called silicone resin) which is a copolymer of three-dimensional network structure, difunctional siloxane preferably represented by the R _'2 SiO T units and / or Q units A silicone resin having a three-dimensional network structure, more preferably a copolymer containing a T unit and / or a Q unit and a D unit. A copolymer having a three-dimensional network structure blocked with a monofunctional siloxy structural unit represented by R ′ ₃ SiO _1/2 (hereinafter referred to as M unit) (that is, containing a T unit and / or a Q unit; Further examples include copolymers containing M units and D units).

  Here, R ′ is preferably a hydrogen atom or a monovalent hydrocarbon group having 1 to 8 carbon atoms which may contain the same or different carbonyl group other than an aryl group. Specific examples of R ′ include hydrogen atom; alkyl group such as methyl group, ethyl group, propyl group, butyl group, pentyl group and hexyl group; cycloalkyl group such as cyclopentyl group and cyclohexyl group; vinyl group, allyl group, Examples thereof include alkenyl groups such as propenyl group, isopropenyl group and butenyl group; acyl groups such as acryloyl group and methacryloyl group. From the viewpoint of easy availability of raw materials, particularly hydrogen atom, methyl group, ethyl group and vinyl group can be suitably used as R ′.

  As the heat-softening silicone resin used in the present invention, one or more of three-dimensional network-structured silicone resin copolymers containing the above-described branched structural units can be used. Furthermore, the main unit is composed of a repeating structure of D units with the D unit as a main component (usually 80 mol% or more, preferably 90 mol% or more), and the molecular chain ends are blocked with M units ( Or unblocked), substantially linear (or branched chain that may contain a small amount of T or Q units) organopolysiloxane (eg silicone oil or silicone raw rubber) , And may be used as a mixture with the three-dimensional network copolymer containing the branched structural unit.

Among these, as the heat-softening silicone resin used in the present invention, a silicone resin containing T unit and D unit (M unit is arbitrary), a silicone resin containing T unit and a rotational viscometer measured at 25 ° C. A silicone resin composition which is a combination of silicone oil or silicone raw rubber having a viscosity of 100 Pa · s or more is preferred. The silicone resin may be one whose ends are blocked with R ′ ₃ SiO _1/2 (M units).

  The composition of the thermosoftening silicone resin will be specifically described. The thermosoftening silicone resin usually has a three-dimensional network structure containing T units and / or Q units as a main component. Designing with only units, or with only M units and Q units is performed. However, it has excellent toughness when solid (a heat dissipating fin formed by impregnating and filling a thermosoftening silicone resin compound in which pores of a porous graphite sheet are dispersed with a heat softening silicone resin or a heat conductive filler. In particular, it is effective to introduce T unit, and it is preferable to use D unit in combination. Here, the substituent (R ′) of the T unit is preferably a methyl group or a phenyl group, and the substituent (R ′) of the D unit is preferably a methyl group, a phenyl group or a vinyl group. The composition ratio (molar ratio) of the T unit and the D unit is preferably 10:90 to 90:10, particularly 20:80 to 80:20.

  In addition, even if it is a silicone resin synthesize | combined only from the M unit and T unit normally used, or only the M unit and Q unit, this contains a T unit and consists of a repeating structure of D unit mainly (the terminal is M). Unit) High viscosity silicone oil (for example, viscosity at 25 ° C. measured by a rotational viscometer of 1,000 Pa · s or more) or a raw rubber-like silicone compound is mixed to heat soften the pores of the porous graphite sheet. Improves brittleness of heat dissipating fins impregnated and filled with heat-softening silicone resin compound dispersed with heat-conductive silicone resin or heat conductive filler, and pumping out in case of sudden temperature change (porous graphite Generation of voids due to separation of the sheet and base siloxane and outflow of base siloxane) can be prevented. Therefore, when a silicone resin having a three-dimensional network structure including T units and not including D units is used, a high-viscosity silicone oil or a silicone raw rubber compound mainly composed of D units may be added to the silicone resin. preferable.

  Therefore, when the silicone resin having a softening point or melting point higher than room temperature contains T units and does not contain D units, a high-viscosity silicone oil or silicone raw rubber mainly containing D units should be added for the above reasons. In this case, it becomes a material with excellent handleability. In this case, the addition amount of the high-viscosity silicone oil mainly composed of D units or the raw rubber-like silicone compound is 1 to 100 parts by mass with respect to 100 parts by mass of the silicone resin having a softening point or melting point higher than room temperature. In particular, the content is preferably 2 to 10 parts by mass. If the amount is less than 1 part by mass, the pumping-out phenomenon is likely to occur. If the amount exceeds 100 parts by mass, the thermal resistance may increase and the thermal radiation may be reduced. Moreover, you may stick a polymer film on both surfaces of a radiation fin for pumping out prevention. In this case, a preferable resin sheet includes a polyethylene terephthalate sheet, a polypropylene sheet, a polyimide sheet, and the like, and a polyethylene terephthalate sheet is more preferable.

As described above, it is desirable to use a silicone resin having a relatively low molecular weight in order to improve handleability. The molecular weight of the heat-softening silicone resin is desirably 500 to 10,000, particularly 1,000 to 6,000.
In addition, molecular weight can be normally calculated | required as a number average molecular weight etc. of polystyrene conversion by gel permeation chromatography analysis using toluene etc. as a developing solvent.

Specifically, as the thermosoftening silicone resin used in the present invention, for example, as shown below, a bifunctional siloxane structural unit (D unit) and a trifunctional silsesquioxane structural unit (T unit) have a specific composition. The silicone resin to contain can be mentioned.
D ¹ _m T _p D ² _n
(Where D ¹ is a dimethylsiloxane unit (ie (CH ₃ ) ₂ SiO), T is a phenylsilsesquioxane unit (ie (C ₆ H ₅ ) SiO _3/2 ), D ² is methylvinylsiloxane) Unit (ie, (CH ₃ ) (CH ₂ = CH) SiO), and (m + n) / p (molar ratio) = 0.25 to 4.0 related to the composition ratio, and (m + n) / m (molar) Ratio) = 1.0 to 4.0.)

Further, for example, a silicone resin containing a monofunctional siloxy structural unit (M unit), a bifunctional siloxane structural unit (D unit), and a trifunctional silsesquioxane structural unit (T unit) in a specific composition. Can do.
M _l D ¹ _m T _p D ² _n
(Where M is a trimethylsiloxane unit (ie, (CH ₃ ) ₃ SiO _1/2 ), D ¹ , T, and D ² are as described above, and (m + n) / p (molar ratio) related to the composition ratio. = 0.25 to 4.0, (m + n) / m (molar ratio) = 1.0 to 4.0, and l / (m + n) (molar ratio) = 0.001 to 0.1 .)

Further, for example, a silicone resin containing a monofunctional siloxy structural unit (M unit), a bifunctional siloxane structural unit (D unit) and a tetrafunctional structural unit (Q unit) represented by SiO _4/2 in a specific composition. Can be mentioned.
M _l D ¹ _m Q _q D ² _n
(Where Q represents SiO _4/2 , M, D ¹ , and D ² are as described above, and (m + n) / q (molar ratio) = 0.25 to 4.0 according to the composition ratio, (M + n) / m (molar ratio) = 1.0 to 4.0, and 1 / (m + n) (molar ratio) = 0.001 to 0.1.

  These can be used singly or in combination of two or more.

[Thermal conductive filler]
Further, in the present invention, a heat conductive filler is added to and dispersed in the heat softening silicone resin in such an amount that does not prevent impregnation of the pores of the porous graphite sheet. You may use as a thing.

  As the heat conductive filler, a known material generally used as a heat conductive filler for this kind of application can be used without particular limitation. For example, metals such as copper, silver, and aluminum: metal oxides such as alumina, silica, magnesium oxide, aluminum hydroxide, and zinc oxide: ceramics such as aluminum nitride, silicon nitride, silicon carbide, and boron nitride: artificial diamond, etc. be able to. Of these, alumina and silica that are relatively easily available and relatively inexpensive are preferable.

The average particle size of the heat conductive filler is preferably 0.5 to 100 μm, more preferably 1 to 50 μm, and particularly preferably 1 to 10 μm. If the average particle size is too large, the contact area with the silicone resin may be small and the pumping-out resistance may be poor, and if it is too small, it may be difficult to mix with the silicone resin. The average particle diameter can be determined, for example, as a cumulative mass average diameter (or median diameter, D ₅₀ ) in particle size distribution measurement by a laser light diffraction method.

  The blending amount of the heat conductive filler is an amount in a range not impeding the impregnation of the pores of the porous graphite sheet, specifically, 1 to 100 parts by mass of the thermosoftening silicone resin. It is preferable that it is 100 mass parts, especially 10-50 mass parts.

[Preparation of thermosoftening silicone resin compound]
The heat-softening silicone resin compound is prepared by mixing the heat-softening silicone resin and the heat-conductive filler with a temperature of 80 to 160 ° C., particularly 100 to 150 ° C., using a mixer such as a planetary mixer. It can be prepared by mixing for 1 hour, especially 1 to 3 hours.

[Production of radiating fins in which pores of porous graphite sheet are impregnated with curable silicone rubber composition and cured]
Next, after impregnating the curable silicone rubber composition into the pores of the porous graphite sheet, the composition is cured to produce a heat radiation fin in which the pores of the porous graphite sheet are filled with the cured silicone rubber. A method will be described.
A typical method for manufacturing a heat radiation fin in which pores of a porous graphite sheet are impregnated with a curable silicone rubber composition and then cured to fill the pores of the porous graphite sheet with a cured silicone rubber is as follows. However, the present invention is not limited to this.

  Specifically, an untreated porous graphite sheet having pores is supplied (installed) on a release-treated polymer film (base material), and a curable silicone rubber composition is applied from the surface of the graphite sheet. After applying a predetermined amount, another release-treated polymer film (base material) is arranged from the upper part of the graphite sheet, and the graphite sheet is separated into two release-treated polymer films (base materials). After the sandwiched state, the applied curable silicone rubber composition is filled into the pores of the porous graphite sheet using a heating press device, and at the same time, the curable silicone rubber is filled into the pores of the porous graphite sheet. The composition was cured, and the pores of the porous graphite sheet were filled with a cured product (silicone rubber) of the curable silicone rubber composition. To produce the fin.

  Here, the impregnation amount or the coating amount of the curable silicone rubber composition is curable silicone rubber with respect to the pore volume in the porous graphite sheet (that is, the product of the volume of the porous graphite sheet and the porosity). It is preferably about 50 to 200% by volume (vol%), particularly about 95 to 120% by volume (vol%) in terms of composition. If the impregnation amount or the coating amount is too small, the adhesion may be impaired, and if it is too large, a pumping out phenomenon may occur.

  The curing conditions are not particularly limited, and may be ordinary curing conditions that can generally cure an addition curing type or organic peroxide type silicone rubber composition. The heating conditions depend on the molar ratio of the composition ((g) SiH group / (f) alkenyl group) and the type of curing catalyst, but are preferably 80 to 150 ° C, more preferably 100 to 130 ° C. , Preferably about 1 minute to 1 hour, more preferably about 5 to 30 minutes. Moreover, in order to avoid generation | occurrence | production of a bubble, it is preferable that the pressure of a press machine is about 0.1-35 MPa, More preferably, it is about 0.5-5 MPa.

[Manufacture of heat dissipation fins in which pores of porous graphite sheet are impregnated with silicone resin]
Next, the manufacturing method of the radiation fin which filled the void | hole part of the porous graphite sheet with the silicone resin is demonstrated.
The typical manufacturing method of the heat radiation fins in which the pores of the porous graphite sheet are filled with silicone resin is as follows. The above heat softening silicone resin or thermally conductive filler is dispersed in the porous graphite sheet. If it is the method of heating, after arrange | positioning the thermosoftening silicone resin compound, it is not limited to this.

Examples of manufacturing methods include the following methods.
(1) Heat the porous graphite sheet. (2) Dispose a heat-softening silicone resin compound in which a heat-softening silicone resin or a heat-conductive filler is dispersed in the heated porous graphite sheet. Impregnation with silicone resin in pores of porous graphite sheet

  In addition, as another manufacturing method, specifically, using a coating device, an untreated porous graphite sheet having pores is supplied (installed) on a polymer film (base material) subjected to a release treatment, After applying a heat-softening silicone resin that has been softened by heating or a heat-softening silicone resin compound in which a heat-conductive filler is dispersed, heat dissipation fins that are filled with silicone resin in the pores of the porous graphite sheet To manufacture. At this time, pressure may be applied so that the heat softening silicone resin blend in which the heat softening silicone resin or the heat conductive filler is dispersed is favorably impregnated in the internal voids of the porous graphite sheet.

  Here, the impregnation amount or the coating amount of the heat softening silicone resin or the heat softening silicone resin compound in which the heat conductive filler is dispersed is determined by the pore volume in the porous graphite sheet (that is, the porous graphite sheet). The product of volume and porosity) is preferably about 50 to 200% by volume (vol%), particularly about 95 to 120% by volume (vol%) in terms of thermosoftening silicone resin compound. If the impregnation amount or the coating amount is too small, the adhesion may be impaired, and if it is too large, a pumping out phenomenon may occur.

  The molding conditions are not particularly limited as long as the pores of the porous graphite sheet can be impregnated with the silicone resin. The condition for heating and softening the thermosoftening silicone resin is preferably 50 to 200 ° C., more preferably 60 to 180 ° C. in order to avoid generation of bubbles.

[Production of heat sink]
Although it does not specifically limit as manufacture of a heat sink, For example, a heat pipe is welded with metals, such as the melt | dissolved solder and silver solder, to the base plate. At this time, since voids may occur, it is preferable to fill with silicone grease. Preferred silicone greases are G-750, G-751, and X-23-7783D (both manufactured by Shin-Etsu Chemical Co., Ltd.), and more preferably X-23-7783D.
Thereafter, a heat radiating fin is disposed at the tip of the heat pipe opposite to the base plate. In this case, since voids may be generated, it is preferable to fill with silicone grease.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In addition, a viscosity shows the value in 25 degreeC by a rotational viscometer.

[Examples 1-6, Comparative Examples 1-4]
First, the components used in the curable silicone rubber composition for impregnating the pores of the porous graphite sheet of the radiating fin used in the heat sink of the present invention after curing are as follows.

<Curable silicone rubber composition>
(A) Component:
Organopolysiloxane represented by the following formula
(In the formula, X is a vinyl group, and b is a number giving the following viscosity.)
(A-1) Viscosity: 600 mPa · s

(B) Component:
Organohydrogenpolysiloxane (B-1) represented by the following formula

(C) Component:
5% by mass chloroplatinic acid-toluene solution (C-1)

(D) Component:
An alkoxy group-containing organosilicon compound represented by the following formula; decyltrimethoxysilane (D-1)
C ₁₀ H ₂₁ Si (OCH ₃ ) ₃

(E) Component (oxide ceramics):
Aluminum oxide powder having an average particle diameter of 5 μm and aluminum oxide (Al ₂ O ₃ -1) having the following average particle diameter

(F) Component:
Organopolysiloxane (F-1) represented by the following formula
(In the formula, X is a vinyl group.)

(G) Component:
Benzoyl peroxide (G-1)

The heat softening silicone resin impregnated in the pores of the porous graphite sheet of the radiating fin used in the heat sink of the present invention is as follows.
<Silicone resin impregnated in the pores of the porous graphite sheet>
(H) Component:
Siloxane resin (H-1) represented by the following composition formula
D ¹ ₂₅ T ₅₅ D ² ₂₀
[Wherein D ¹ is a dimethylsiloxane unit (ie, (CH ₃ ) ₂ SiO _2/2 ), T is a phenylsilsesquioxane unit (ie (C ₆ H ₅ ) SiO _3/2 ), and D ² is It represents a methylvinylsiloxane unit (that is, (CH ₃ ) (CH ₂ ═CH) SiO _2/2 ). ]
(Number average molecular weight: about 2,000, softening point: 48 ° C.)

Furthermore, the porous graphite sheet of the radiation fin used for the heat sink of this invention is as follows.
Porous graphite sheet:
Graphite sheet MACFOIL (manufactured by Japan Matex Co., Ltd., porosity (volume%): about 45 vol%, thickness 130 μm) (I-1)

The silicone grease that fills the gap between the base plate and the heat pipe and the gap between the heat pipe and the radiation fin used in the heat sink of the present invention is as follows.
X-23-7783D (manufactured by Shin-Etsu Chemical Co., Ltd.) (J-1)

The base plate used for the heat sink of the present invention is as follows.
Copper plate (purity 99.9%; 40 mm x 40 mm x 2 mmt)

The heat pipe used for the heat sink of the present invention is as follows.
Copper heat pipe (hydraulic oil; water, φ8mm x L80mm)

<Preparation of radiating fins>
(When using a curable silicone rubber composition)
The above components were uniformly mixed in the blending amounts shown in Table 1 to prepare a curable silicone rubber composition.
A porous graphite sheet is supplied (arranged) on the release-treated polymer film, a curable silicone rubber composition is applied, and then another release-treated polymer film is placed from the top of the graphite sheet. After the graphite sheet was sandwiched between two release-treated polymer films, the porous graphite sheet was emptied by heating at 120 ° C. for 10 minutes at a pressure of 3 MPa using a heating press. A radiating fin was prepared by filling and curing the curable silicone rubber composition in the pores, and filling the pores of the porous graphite sheet with the cured product (silicone rubber) of the curable silicone rubber composition. In addition, the thickness of the radiation fin after filling was 130 μm.

(When using silicone resin)
A porous graphite sheet is supplied onto the polymer film that has been subjected to mold release treatment, and a liquid thermosoftening silicone resin that has been heated to improve workability is applied onto the porous graphite sheet using a knife coater, and then the coating speed is increased. After passing through a heating furnace at 2 m / min and heating conditions of 100 ° C., another release-treated polymer film was placed from the top of the graphite sheet, and the graphite sheet was sandwiched between two release-treated polymer films. After being in a dry state, thermocompression bonding was performed by a heat treatment at 120 ° C. for 10 minutes at a pressure of 3 MPa using a heat press apparatus, and the pores of the porous graphite sheet were impregnated and filled with a thermosoftening silicone resin. A radiation fin was prepared. In addition, the thickness of the radiation fin after filling was 130 μm.

<Preparation of heat sink>
As shown in FIG. 1, the heat pipe 2 is welded to the base plate 1 with molten solder, and the generated gap is filled with the silicone grease 4, and then the end of the heat pipe 2 opposite to the base plate 1 is cut. Eight radiating fins 3 (60 mm × 60 mm) were arranged. In this case, the generated gap was filled with silicone grease 4 to prepare a heat sink.

[Evaluation method]
The obtained heat fins and heat sinks were tested and measured for the following characteristics, and the evaluation results are shown in Tables 1 and 2.
[mass]
The mass of the entire heat sink was measured.
[Heat radiation fin workability]
The evaluation was made based on whether or not the heat radiation fin was damaged during cutting with a cutter knife in the tearing direction.
Evaluation A: No damage Evaluation B: Damaged [Heat dissipation]
A heat sink is arranged on an aluminum heating element (heat transfer surface 15 mm square x height 100 mm) equipped with a thermocouple, supplied power 10 W, and heated for 60 minutes so that the temperature becomes substantially constant. The temperature of was measured. The measurement environment was 25 ° C. ± 2 ° C. and humidity 50% ± 5%.

*: Molar ratio of SiH groups in the organohydrogenpolysiloxane to alkenyl groups in the alkenyl group-containing organopolysiloxane **: curable silicone rubber composition comprising the components (a) to (g), and the component (h) The thermosoftening silicone resin was applied and impregnated in an amount of 100% by volume (vol%) with respect to the pore volume in the porous graphite sheet.

As is apparent from Table 1, each example is a heat sink that is lightweight and excellent in heat dissipation.
Further, as is clear from Table 2, when the radiating fin is composed of only a porous graphite sheet as in Comparative Example 1, or when the radiating fin is composed of an aluminum foil as in Comparative Example 2. The workability of the radiating fin is poor, and the heat radiating performance is poor.
Furthermore, when the heat sink is not an radiating fin, a heat pipe, a base plate, or silicone grease, but only an aluminum heat sink, the result is inferior in heat dissipation. To obtain the same heat dissipation characteristics as in Example 1, Comparative Example 4 As described above, the mass of the entire aluminum heat sink is required to be 135 g, which is inferior in light weight.

1 Base plate 2 Heat pipe 3 Radiating fin 4 Silicone grease

Claims (9)

  A heat sink comprising a base plate, a heat pipe, and a heat radiating fin, wherein the heat radiating fin is impregnated with a silicone resin in a pore portion of a porous graphite sheet or impregnated with a curable silicone rubber composition and then cured. A heat sink characterized by comprising a graphite sheet. A curable silicone rubber composition impregnated in the pores of the porous graphite sheet is
(A) The following average composition formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
(In the formula, R ¹ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and a is a positive number of 1.8 to 2.2.)
An organopolysiloxane having two or more alkenyl groups bonded to a silicon atom represented by the formula:
(B) Organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule: moles of hydrogen atoms directly bonded to silicon atoms in component (b) relative to alkenyl groups in component (a) An amount such that the ratio is 0.5-5.0,
(C) Platinum group metal catalyst: 0.1 to 1,000 ppm with respect to the mass of component (a) in terms of mass of platinum group metal element, and (d) alkoxy group-containing organosilicon compound: 0.01 to 50 The heat sink according to claim 1, which is a curable silicone rubber composition containing parts by mass. A curable silicone rubber composition to be impregnated into the pores of the porous graphite sheet,
(E) Oxide ceramics: The heat sink according to claim 2, which is a curable silicone rubber composition containing 2 to 200 parts by mass with respect to 100 parts by mass of the component (a). A curable silicone rubber composition impregnated in the pores of the porous graphite sheet is
(F) The following average composition formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
(In the formula, R ¹ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and a is a positive number of 1.8 to 2.2.)
A curable silicone rubber containing 100 parts by mass of an organopolysiloxane having two or more alkenyl groups bonded to a silicon atom represented by the formula: and (g) an organic peroxide: 0.1 to 2 parts by mass The heat sink according to claim 1, which is a composition.   2. The heat sink according to claim 1, wherein the silicone resin impregnated in the pores of the porous graphite sheet is a thermosoftening silicone resin that is substantially solid at room temperature.   The thermosoftening silicone resin is composed of a bifunctional siloxane structural unit (D unit) and a trifunctional silsesquioxane structural unit (T unit), or a bifunctional siloxane structural unit (D unit) and a tetrafunctional structural unit ( The heat sink according to claim 5, wherein the heat sink contains Q units.   The heat sink according to any one of claims 1 to 5, wherein the porosity (volume%) of the porous graphite sheet is 30 to 80 vol%.   The heat sink according to any one of claims 1 to 6, wherein silicone grease is supplied to a gap existing in a connection portion between the base plate and the heat pipe.   The heat sink according to any one of claims 1 to 7, wherein silicone grease is supplied to a gap portion present at a connection portion between the heat pipe and the radiation fin.