JP2013086433A - Thermally conductive silicone composite sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermally conductive silicone composite sheet excellent in electrical insulation properties, thermal conductivity, strength, and durability.SOLUTION: The thermally conductive silicone composite sheet includes an intermediate layer (A) and a pair of outer layers (B) laminated on both surfaces of the intermediate layer (A), the intermediate layer (A) is formed of an electrically insulating and heat resistant thermally conductive synthetic resin film, and the pair of outer layers (B) are formed of a thermally conductive silicone resin composite having an adhesion property and heat softening property.

Description

The present invention relates to a thermally conductive silicone composite sheet suitable as a member interposed between a heat-generating electronic component and a heat-dissipating component such as a heat-dissipating fin, and in particular has good electrical insulation and thermal conductivity and strength. The present invention also relates to a heat conductive silicone composite sheet that is rich in flexibility and adhesiveness.

  Conventionally, an electrically insulating heat conductive material is used for a heat radiating member of a heat generating electronic / electrical component such as a power transistor, a MOS transistor, an FET, a thyristor, a rectifier, and a transformer. As such an electrically insulating heat conductive material, for example, a synthetic rubber such as silicone rubber blended with metal oxide powder such as beryllium oxide, aluminum oxide, aluminum hydroxide, magnesium oxide, zinc oxide ( Patent Document 1) and those obtained by blending boron nitride into silicone rubber and reinforcing it with a mesh-like insulating material (Patent Document 2).

Further, as one means for further improving the heat conductivity of the electrically insulating heat conductive material, it is conceivable to reduce the thickness as much as possible. However, if the thickness is too thin, there arises a problem that the strength, durability or electrical insulation of the heat dissipation member is impaired.

  In order to improve this problem, the intermediate layer uses a film having high heat resistance, electrical insulation and mechanical strength such as aromatic polyimide, polyamide, polyamideimide, polyethylene naphthalate, etc., and beryllium oxide, aluminum oxide, It has been proposed to provide a multilayer structure having a silicone rubber layer excellent in thermal conductivity and electrical characteristics blended with aluminum hydroxide or the like. Specifically, a polyimide (amide) film containing a predetermined amount of aluminum oxide or the like is used as an intermediate layer, and a pair of outer layers are formed on both sides of the intermediate layer as a pair of silicone rubber layers containing aluminum oxide or the like. A thermally conductive electrically insulating member having a composite body has been proposed (Patent Document 3).

  However, these thermally conductive electrical insulating members having a multilayer structure have unstable adhesiveness between the silicone rubber layer of the outer layer and the film such as aromatic polyimide of the intermediate layer. There is a drawback that peeling is likely to occur and durability is inferior.

  To improve this problem, a silicon compound having at least one functional group selected from the group consisting of an epoxy group, an alkoxy group, a vinyl group, and a hydrogen atom (Si-H) bonded to silicon There has been proposed a heat conductive silicone rubber composite sheet obtained by using a composition containing a system adhesiveness-imparting agent for the outer layer and curing the composition (Patent Document 4).

  However, in these heat conductive silicone rubber composite sheets, the contact heat resistance between the sheet, the heating element and the heat radiating body is high, the thickness of the heat conductive silicone rubber layer is large, and the heat conduction characteristics of the composite sheet as a whole are high. There was a drawback of being lowered.

  In the case of other known heat conductive silicone rubber composite sheets (Patent Documents 5 to 7), excellent interlayer adhesion and good heat conductivity cannot be satisfied at the same time. Moreover, since these known heat conductive silicone rubber composite sheets have no adhesiveness on the surface, they cannot be easily adhered to heat-generating electronic components or heat-dissipating members without an auxiliary agent. Therefore, in order to impart adhesiveness to these composite sheets, it is necessary to coat the surface with an adhesive, but there is a problem that the thermal conductivity is deteriorated by the coated adhesive.

JP 47-32400 A Japanese Utility Model Publication No. 54-184074 Japanese Patent Publication No. 2-24383 JP 2004-122664 A JP 2001-018330 A Japanese Patent Application Laid-Open No. 11-157011 Japanese Patent Laid-Open No. 10-237228

  Then, the objective of this invention is providing the heat conductive silicone composite sheet excellent in electrical insulation, heat conductivity, intensity | strength, and durability.

That is, the present invention provides a means for achieving this object.
Having an intermediate layer (A) and a pair of outer layers (B) laminated on both sides of the intermediate layer (A);
The intermediate layer (A) is composed of a heat conductive synthetic resin film that is electrically insulating and heat resistant,
The pair of outer layers is composed of a heat conductive silicone resin composition having adhesiveness and heat softening property.
A thermally conductive silicone composite sheet is provided.

The present invention also provides:
The above-mentioned heat conductive silicone comprising, on both surfaces of an electrically insulating and heat-resistant synthetic resin film, a sheet made of a heat conductive silicone resin composition having adhesiveness and heat softening property, or room temperature pressure bonding or thermocompression bonding A method for producing a composite sheet is provided.

  In the heat conductive silicone composite sheet of the present invention, as described later, the thickness of the composite sheet is preferably 50 to 1,000 μm. The intermediate layer (A) is composed of a heat conductive film having a thermal conductivity of 0.3 W / m · K or more, including a synthetic resin and a heat conductive filler dispersed in the synthetic resin, and the outer layer The thermal conductivity of (B) is preferably 0.3 W / m · K or more. The synthetic resin is preferably an aromatic polyimide, polyamide, polyamideimide, polyester, fluorine polymer, or a combination of two or more thereof, and the thermally conductive filler dispersed in the synthetic resin is: It is preferably at least one selected from zinc oxide powder, aluminum oxide powder, magnesium oxide powder, aluminum hydroxide powder, boron nitride powder, aluminum nitride powder, silicon carbide powder, and diamond powder.

  Since the heat conductive silicone composite sheet of the present invention has a silicone layer having adhesiveness and heat softening properties as an outer layer, it has excellent adhesion to a heating element or a heat radiating body, and the outer layer has adhesion to an intermediate layer. Also excellent. As a result, the thermal conductivity is very good.

  Since the silicone composition layer itself used as the outer layer has adhesiveness, it is excellent in durability because it adheres firmly to the intermediate layer, particularly the synthetic resin film layer.

  When the intermediate layer is made of aromatic polyimide, polyamide, polyamideimide, polyester, fluoropolymer, or a combination of two or more of these, it is sufficient even if it is thin due to the reinforcing and insulating effect of this synthetic resin. Have high strength and flexibility.

Hereinafter, the present invention will be described in detail. In addition, the thermal conductivity of the synthetic resin film layer in this specification is a value measured at 25 ° C. by a laser flash method.

<Thermal conductive silicone composite sheet>
[(A) Intermediate layer]
As the intermediate layer of the composite sheet of the present invention, a synthetic resin film excellent in heat resistance, electrical insulation and thermal conductivity is used. If it is a synthetic resin film applicable to this condition, it will not specifically limit, All the well-known things can be used. The synthetic resin film is preferably flexible and has high mechanical strength.

  The synthetic resin film layer must have excellent thermal conductivity, and the thermal conductivity is usually preferably 0.3 W / m · K or more, more preferably 0.4 W / m · K or more. is there. Such a synthetic resin film having a high thermal conductivity is hereinafter referred to as a “thermal conductive synthetic resin film”. When the thermal conductivity is less than 0.3 W / m · K, the thermal conductivity is inferior to the thermal conductive silicone resin composition constituting the outer layer (B), and the thermal conductivity of the composite sheet of the present invention is insufficient. It is easy to become. In order to achieve the object of the present invention, the higher the thermal conductivity, the better. The upper limit is not limited at all, but in practice it may be about 10 W / m · K or less.

  The thickness of this heat conductive synthetic resin film layer is usually in the range of 5 to 40 μm, preferably 10 to 30 μm. If the thickness is too thick, the thermal conductivity of the composite sheet of the present invention is liable to be impaired. Conversely, if the thickness is too thin, the strength to be exhibited as an intermediate layer is insufficient, and the withstand voltage characteristics deteriorate, resulting in an electrical insulation performance. May become insufficient. Furthermore, the heat conductive synthetic resin film layer needs to be a film layer that does not have a hole that reduces the withstand voltage characteristic.

  The thermally conductive synthetic resin film layer having a thermal conductivity of 0.3 W / m · K or more used as the intermediate layer is typically a synthetic resin and a thermally conductive filler dispersed and blended in the synthetic resin. It is a layer which consists of a film containing these. Each of the synthetic resin and the thermally conductive filler can be used alone or in combination of two or more.

  Examples of synthetic resins include aromatic polyimides; polyamides; polyamideimides; polyesters such as polyethylene naphthalate; and fluoropolymers such as polytetrafluoroethylene (PTFE) and tetrafluoroethylene / perfluoroalkyl vinyl ether copolymers. Can do. In the case of using the fluorine-based polymer as the synthetic resin, it is preferable from the viewpoint of improving the adhesiveness that the surface of the obtained film is subjected to a chemical etching treatment using a metal Na / naphthalene-based treatment liquid.

  As the thermally conductive filler dispersed and blended in the synthetic resin, for example, metal powder, metal oxide powder, ceramic powder and the like are used. Specifically, aluminum powder, copper powder, silver powder, nickel powder, gold powder, zinc oxide powder, aluminum oxide powder, magnesium oxide powder, aluminum hydroxide powder, boron nitride powder, aluminum nitride powder, silicon carbide powder, diamond Although heat conductive inorganic powders, such as powder, are mentioned, it is not limited to this, What kind of thing may be used if it has heat conductivity and insulation. These fillers can be used alone or in combination of two or more. The blending amount of the thermally conductive filler is adjusted so as to obtain a desired thermal conductivity, and is usually in the range of 200 to 1500 parts by mass per 100 parts by mass of the synthetic resin.

  In addition, a heat conductive synthetic resin film layer having a thermal conductivity of 0.3 W / m · K or more improves the crystallinity of the synthetic resin without adding a heat conductive filler to the synthetic resin, and conducts heat. It may be a synthetic resin film with improved properties. Furthermore, the above-mentioned thermally conductive filler may be dispersed in a synthetic resin with increased crystallinity.

  If the melting point of the synthetic resin film layer is 200 ° C. or higher, preferably 250 ° C. or higher, the synthetic resin film layer is excellent in heat resistance and is less likely to cause deterioration in mechanical strength and thermal deformation.

  Examples of suitable commercial products of the synthetic resin film layer include, for example, Kapton (registered trademark) MT type (trade name) which is an aromatic polyimide-based film as a heat conductive film having a heat resistance having a melting point of 250 ° C. or higher. And Toray DuPont Co., Ltd.).

[(B) Outer layer]
The heat conductive silicone composite sheet of the present invention comprises an outer layer laminated on both sides of the intermediate layer, and a layer made of a heat conductive silicone resin composition having adhesiveness and heat softening properties (hereinafter referred to as “heat softening heat”). A conductive silicone resin layer). That is, a first thermosoftening thermally conductive silicone resin layer laminated on one surface of the intermediate layer (A) and a second thermosoftening thermally conductive silicone resin layer laminated on the other surface. Have.

  The heat conductive silicone resin composition which comprises this outer layer (B) contains the silicone resin which has heat softening property, and a heat conductive filler, and has adhesiveness and heat softening property.

  Here, “thermosoftening property” means that an object that is solid at room temperature is heated and fluidized.

  Since the outer layer (B) has adhesiveness, the outer layer (B) is excellent in adhesiveness with the intermediate layer (A) and brings about a good bonding state between both layers. Moreover, in order to have both adhesiveness and heat softening property, the heat conductive silicone composite sheet of this invention shows and maintains favorable adhesiveness with the heat generating body and heat radiating member which contact in use. That is, the heat softening heat conductive silicone resin layer, which is the outer layer, is softened by heat from the solid state due to the heat generated by the operation of the electronic component, that is, it is fluidized, so that there is no gap between the heating element and the heat radiating member. Close contact with. Thereby, good heat conduction performance is achieved between the heating element and the heat radiating member. In this case, the degree of fluidization can be from a high viscosity state to a low viscosity state depending on the temperature. The entire outer layer does not need to be fluidized to a uniform viscosity, and it is necessary to fluidize sufficiently so as not to leave a gap at the contact portion with the heating element or the heat radiating member.

-Thermally conductive silicone resin composition-
The heat conductive silicone resin composition constituting the outer layer typically includes a silicone resin having heat softening properties and adhesiveness, and a heat conductive filler dispersed therein using the resin as a matrix. It contains.

·Silicone resin:
The silicone resin used as a matrix in the composition is also heat softening, and in particular, the viscosity at 70 ° C. is 400 Pa.s. It is s or less and has adhesiveness. Here, the viscosity is measured with a rotational viscometer. The silicone resin is superior in terms of reliability and pumping-out resistance as compared with other phase transition materials or heat softening materials such as paraffin wax, α-olefin, and fluorine resin. The thermally conductive silicone composite sheet of the present invention fluidizes at a required temperature and enters the gap between the heating element and the heat radiating member. At that time, a representative electronic component that requires the most precise flow behavior is a CPU of a personal computer. As a practical index, the inventors of the present invention have a personal computer CPU in which the silicone resin has a viscosity of 400 Pa. s or less, preferably 100 Pa.s. It has been found that when it is s or less, the heat conductive silicone resin composition is imparted with good heat softening properties, that is, expected flow behavior. If this condition is satisfied, it has been found that the required heat softening property and flow behavior can be sufficiently obtained in other applications such as electronic parts for automobiles. Therefore, heat softening property is an important property of the present composition, and it contains the silicone resin and the heat conductive filler, and further contains a crosslinking agent and / or a catalyst to improve curability, particularly thermosetting. The composition which has does not correspond to the thermosoftening composition used for this invention.

  The silicone resin has adhesiveness and a viscosity at 70 ° C. of 400 Pa.s. The type is not particularly limited as long as it is s or less. Specific examples include silicone resins having a molecular composition represented by the following formulas (1) to (3).

Formula (1):
^{_{D m T φ p D Vi n}} (1)
(Where D is a dimethylsiloxane unit (ie, (CH ₃ ) ₂ SiO), T ^φ is a phenylsiloxane unit (ie, (C ₆ H ₅ ) SiO _3/2 ), and D ^Vi is a methylvinylsiloxane unit ( That is, (CH ₃ ) (CH ₂ = CH) SiO) is represented, and ((m + n) / p (molar ratio) = 0.25 to 4.0, (m + n) / m (molar ratio) = 1.0 to 4.0.)
Moreover, for example, a silicone resin having a specific composition of a monofunctional structural unit (M unit), a bifunctional structural unit (D unit), and a trifunctional structural unit (T unit) can be given.

Formula (2):
^{_{M L D m T φ p D}} Vi n (2)
(Where M represents a trimethylsiloxane unit (ie, (CH ₃ ) ₃ SiO _1/2 ), D, T ^φ and D ^Vi are as described above, and (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.
Furthermore, for example, a silicone resin having a specific composition of a monofunctional structural unit (M unit), a bifunctional structural unit (D unit), and a tetrafunctional structural unit (Q unit) can be given.

Formula (3):
^{_{M L D m Q q D Vi}} n (3)
(Q represents SiO _4/2 , M, D and D ^Vi are as described above, and (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.)

・ Thermal conductive filler:
As the thermally conductive filler dispersed in the silicone resin, any known filler that has been conventionally used as a thermally conductive filler can be used. For example, metal powder, metal oxide powder, ceramic powder, etc. are used. Specifically, aluminum powder, copper powder, silver powder, nickel powder, gold powder, aluminum oxide powder, aluminum hydroxide powder, silicon oxide powder, zinc oxide powder, magnesium oxide powder, iron oxide powder, titanium oxide powder, oxidation Examples thereof include zirconium powder, aluminum nitride powder, boron nitride powder, silicon nitride powder, diamond powder, carbon powder, fullerene powder, and carbon graphite powder.

  As these heat conductive fillers, those having an average particle diameter of 0.1 to 100 μm, preferably 0.5 to 50 μm can be used. When it is less than 0.1 μm, the viscosity when the heat conductive silicone composite sheet of the present invention is pressure-bonded to the heating element or the heat dissipation member is increased, and a gap is generated between the composite sheet and the heating element or the heat dissipation member, It becomes so large that it cannot be ignored, which increases the thermal resistance and makes it difficult to develop sufficient heat conduction performance. When the thickness exceeds 100 μm, the viscosity at the time of pressure bonding of the thermosoftening heat conductive sheet is lowered, but the thickness of each outer layer cannot be reduced to 100 μm or less, and the heat resistance is also increased, so that sufficient heat conduction is achieved. It may be difficult to develop performance. Accordingly, the average particle size is preferably in the range of 0.1 to 100 μm, and more preferably 0.5 to 50 μm for achieving both fluidity and thermal conductivity. Here, the average particle diameter is a volume average particle diameter, and is a value measured by a Microtrac particle size distribution measuring device MT3300EX (manufactured by Nikkiso Co., Ltd.).

  These heat conductive fillers may be used alone or in combination of two or more. Two or more kinds of particles having different average particle diameters can be used.

  The content rate of the heat conductive filler in this silicone resin composition can be 60-97 mass%, for example, Preferably it can be 75-95 mass%. When the content of the heat conductive filler is small, the heat conductivity of the outer layer may be lowered, and when the content is large, a uniform thermosoftening heat conductive sheet layer may not be obtained.

・ Other ingredients:
An arbitrary component can be added to said silicone resin composition in the range which does not impair the objective of this invention as needed. Hereinafter, such optional components will be described.

.. (c) Surface treatment agent:
Hydrophobic treatment of the heat conductive filler during preparation of the above heat conductive silicone composition improves the wettability between the filler and the silicone resin component, and the heat conductive filler is heat softened silicone resin component. A surface treatment agent (wetter) can be blended for the purpose of uniformly dispersing in the matrix. As this surface treating agent (c), an alkoxysilane compound represented by the following general formula (4) is particularly desirable.

General formula (4):
R ¹ _a R ² _b Si (OR ³ ) _4-ab (4)
[Wherein, R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, and R ³ is independently a carbon atom. An alkyl group of 1 to 6, a is an integer of 1 to 3, b is an integer of 0 to 2, and a + b is an integer of 1 to 3; ]

Examples of the alkyl group represented by R ¹ in the general formula (4) 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 ¹ is in the range of 6 to 15, the wettability of the thermally conductive filler is sufficiently improved and the handling workability is improved.

Examples of the unsubstituted or substituted monovalent hydrocarbon group represented by R ² 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 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 ³ include alkyl groups such as 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 alkoxysilane compound represented by the general formula (4) 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

  The said surface treating agent (c) may be used individually by 1 type, or may be used in combination of 2 or more type. The compounding amount of the surface treatment agent (c) is preferably 0.01 to 40 parts by mass, particularly 0.1 to 30 parts by mass with respect to 100 parts by mass of the thermosoftening silicone resin (a). preferable. Even if this blending amount is exceeded, the wetter effect does not increase any more, which is uneconomical. Further, since this component is volatile, the molded product gradually hardens when left in an open system, so it is preferable to keep the amount to the minimum necessary amount.

.. (d) Organopolysiloxane:
To the thermally conductive silicone resin composition, an organopolysiloxane having a kinematic viscosity at 23 ° C. of 10 to 100,000 mm ² / s represented by the following general formula (5) is further added as component (d). be able to. This component is appropriately used for the purpose of imparting properties such as a viscosity modifier of the composition.

General formula (5):
_{^{R 4 - (SiR 4 2 O}} ) c SiR 4 2 -R 4 ··· (5)
[Wherein, R ⁴ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms and not containing a reactive functional group such as an aliphatic unsaturated bond. Yes, c is an integer from 5 to 2,000. c is a number that gives the above kinematic viscosity, but is typically preferably an integer of 5 to 2,000, particularly preferably an integer of 10 to 1,000. ]

Examples of R ⁴ include alkyl groups such as a methyl group, an ethyl group, a propyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, and an octadecyl group; and a cyclohexyl group such as a cyclopentyl group and a cyclohexyl group. Group; aryl group such as phenyl group and tolyl group; aralkyl group such as 2-phenylethyl group and 2-methyl-2-phenylethyl group; 3,3,3-trifluoropropyl group, 2- (perfluorobutyl) Examples thereof include halogenated hydrocarbon groups such as an ethyl group, 2- (perfluorooctyl) ethyl group, and p-chlorophenyl group. In the present invention, a methyl group, a phenyl group, and an alkyl group having 6 to 18 carbon atoms are particularly preferable.

Organopolysiloxane of component (d) is preferably a kinematic viscosity at 25 ° C. is 10~100,000mm ² / s, it is particularly preferably 100~10,000mm ² / s. When the said kinematic viscosity is lower than 10 mm < ² > / s, the hardened | cured material obtained from the composition of this invention will generate | occur | produce an oil bleed easily. When the said kinematic viscosity is larger than 100,000 mm < ² > / s, the fluidity | liquidity of the heat conductive composition of this invention will become poor easily.

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

  When the organopolysiloxane of component (d) is added to the composition of the present invention, the amount added is not particularly limited as long as the desired effect can be obtained. Generally, it is 0.1-100 mass parts with respect to 100 mass parts of silicone resins (a), More preferably, it is 1-50 mass parts. When the amount of component (d) is within this range, the fluidity of the heat-softening thermally conductive silicone composition before molding becomes good and not only the workability is kept good, but also the heat conductive filling. The work of filling the material becomes easy.

・ Other optional ingredients:
Other optional components include, for example, fluorine-modified silicone surfactants; carbon black, titanium dioxide, bengara, etc. as colorants; metal oxides such as platinum compounds, iron oxide, titanium oxide, cerium oxide as flame retardants, A metal hydroxide or the like may be added. Further, fine powder silica such as precipitated silica and calcined silica, thixotropic improver, and the like can be appropriately added for the purpose of preventing or reinforcing the heat conductive filler.

  The thermally conductive silicone resin composition having the composition described above usually has a thermal conductivity of 0.3 W / m · K or more, preferably 1.0 W / m · K or more, and usually 20 W / m · K. It is as follows.

  The thickness of the outer layer is preferably in the range of 30 to 300 μm, more preferably in the range of 60 to 200 μm. If the outer layer is too thin, adhesion to the intermediate layer (A), the heating element and the heat radiating member becomes weak, and peeling may occur. Moreover, when too thick, the heat conductive characteristic of a heat conductive silicone composite sheet may deteriorate.

  PCS-TC-10, PCS-TC-11, and PCS-TC-20 (trade names, all manufactured by Shin-Etsu Chemical Co., Ltd.) can be used as the outer layer. ).

  The two outer layers, that is, the first thermosoftening thermally conductive silicone resin layer and the second thermosoftening thermally conductive silicone resin layer may have the same or different compositions. Good.

<Method for producing thermally conductive silicone composite sheet>
Next, the manufacturing method of the heat conductive silicone composite sheet which concerns on this invention is demonstrated.

  The method for producing a heat conductive silicone composite sheet of the present invention is a sheet comprising a heat conductive silicone resin composition having the above-mentioned adhesiveness and heat softening properties on both surfaces of an electrically insulating and heat resistant film (hereinafter referred to as “ It is possible to manufacture by thermally bonding a thermoconductive silicone resin sheet)) at room temperature or thermocompression bonding.

  The electrically insulating and heat resistant film (hereinafter referred to as the intermediate layer film) and the heat conductive silicone resin composition having adhesiveness and heat softening properties are as described above.

  In the case of room temperature pressure bonding, for example, the surface of the thermally conductive silicone resin sheet in which the release-treated polymer film is adhered to both sides of the interlayer film is not adhered to the polymer film. The heat conductive silicone resin sheet may be transferred to the intermediate layer film by pasting it on each of the two surfaces and then peeling the polymer film. In the case of thermocompression bonding, the press jig is heated to a temperature equal to or higher than the heat softening temperature (for example, 80 to 120 ° C.), and is similarly transferred by pressure bonding. For the pressure bonding, roll pressure bonding or the like can be used in addition to press pressure bonding.

  However, the method for producing the heat conductive silicone composite sheet of the present invention is not limited to the method described above, and for example, the above-described heat conductive silicone composition having adhesiveness and heat softening property is dissolved and dispersed in a solvent. It is also possible to manufacture a heat conductive silicone composite sheet by applying and drying on both surfaces of the intermediate layer film.

  The heat conductive silicone composite sheet of the present invention can facilitate handling such as transportation and standard cut by sticking a release treatment film as a protective separator film on both sides thereof. Thus, the thermally conductive silicone composite sheet with the separator film attached to both sides is peeled off the separator film on one side to expose the composite sheet surface, and is attached to the heat-generating electronic component or the heat dissipation member, and then the other side. The separator film on the surface is peeled off, and the exposed surface is attached to another heat radiating member or electronic member. By such a treatment, the sheet can be easily disposed at a desired position even though it is a thin sheet, and excellent heat conduction characteristics can be exhibited.

  In addition, by making the composition of the heat conductive silicone resin composition different from the composition for the first outer layer and the composition for the second outer layer, the adhesion of the two surfaces of the heat conductive silicone composite sheet is improved. It is possible to have different genders. If it does in this way, at the time of rework, adhesion, or exfoliation, it is also possible to exfoliate only the weak adhesion side, maintaining adhesion in the strong adhesion side. In this case, since the stress applied to the adherend is reduced on the weak adhesive side, breakage can be prevented.

  The thicknesses of the first and second outer layers in the thermally conductive silicone composite sheet of the present invention are each preferably 10 to 500 μm, and particularly preferably 20 to 250 μm. The total thickness of the composite sheet is preferably 50 to 1,000 μm, more preferably 70 to 500 μm. If the thickness is too thin, the handling is poor and the tackiness is reduced. On the other hand, the desired thermal conductivity cannot be obtained because the thickness is too large.

Examples of the present invention and comparative examples will be shown below to explain the present invention more specifically, but the present invention is not limited to these.

The materials used in the following examples and comparative examples are shown below. In addition, regarding the outer layer (B), the viscosity of the silicone resin was measured using a HAAKE RotoVisco 1 (Rotovisco) rotary viscometer. Specifically, a flat disk (diameter 20mm) on the lower side of two disks arranged horizontally above and below the vertical central axis and an upper cone disk (diameter 20mm, cone angle 2 degrees, The sample silicone resin was sandwiched between the trunk (0.1 mm), the flat disk was fixed, and the cone-shaped disk was rotated at a rotational speed of 10 s ^-1 around the central axis as a rotation axis. .

<Intermediate layer (A)>
(A-1): manufactured by Toray DuPont Co., Ltd., with a thermal conductivity of 0.08 W / m · K and a thickness of 25 μm
Aromatic polyimide film (trade name: Kapton 100H)
(A-2): manufactured by Toray DuPont Co., Ltd., with a thermal conductivity of 0.42 W / m · K and a thickness of 25 μm
Thermally conductive aromatic polyimide film (trade name: Kapton 100MT)

<Outer layer (B)>
(B-1):
(A) Resin having heat softening property: A silicone resin having the following characteristics.
・ Formula: M _0.25 D ₂₅ D ^Vi ₂₀ T ^φ ₅₅
・ Viscosity at 70 ° C .: 50 Pa. s
(B) Thermally conductive filler: alumina + zinc oxide (containing about 1120 parts by mass of thermally conductive filler with respect to 100 parts by mass of silicone resin),
Thickness 200μm
Thermal conductivity as a composition: 3.8 W / m-K

(B-2):
(A) Resin having heat softening property: A silicone resin having the following characteristics.
・ Formula: M _0.25 D ₂₅ D ^Vi ₂₀ T ^φ ₅₅
・ Viscosity at 70 ° C .: 50 Pa. s
(B) Thermally conductive filler: Aluminum + zinc oxide (containing about 760 parts by mass of thermally conductive filler with respect to 100 parts by mass of silicone resin),
60 μm thickness
Thermal conductivity as a composition: 4.2 W / m-K

(B-3): F-9460PC
(Product name, Sumitomo 3M Limited, acrylic double-sided adhesive tape)
50 μm thickness
(B-4): G747
(Product name, manufactured by Shin-Etsu Chemical Co., Ltd., thermally conductive grease)

≪Manufacture of heat conductive silicone composite sheet≫
In each example and each comparative example, as shown in Table 1, the intermediate layer (A) and the outer layer 1 laminated on one side of the intermediate layer (A) and the outer layer 2 laminated on the other side were combined. A heat conductive silicone composite sheet was prepared by roll pressure bonding.

≪Evaluation≫
The following characteristics were evaluated about the heat conductive silicone composite sheet obtained in each case. The obtained results are shown in Table 1.

・ Sheet thickness:
It measured using the micrometer (The product made from Mitutoyo Corporation, model; M820-25VA).

・ Thickness and thermal resistance after thermocompression bonding:
The obtained heat conductive silicone composite sheet was placed on the entire surface of a disk-shaped plate (purity: 99.9%, diameter: about 12.7 mm, thickness: about 1.0 mm) made of aluminum, and another was placed thereon. The same disk-shaped plate was stacked, and the obtained structure was sandwiched by clips at two positions on both ends on the diametrically opposite side, and a pressure of about 175.5 kPa (1.80 kgf / cm ² ) was applied. A layered specimen was obtained.

The thickness of the obtained test specimen was measured, and the thickness of the thermally conductive silicone composite sheet after thermocompression bonding was calculated by subtracting the thickness of the aluminum plate. A micrometer (manufactured by Mitutoyo Corporation, model: M820-25VA) was used to measure the thickness of the test piece. The thermal resistance (cm ² · K / W) after thermocompression bonding of the thermally conductive silicone composite was measured with a thermal resistance measuring instrument (manufactured by Netch, Xenon Flash Analyzer; LFA447 NanoFlash) using the test piece.

-Pumping out property The obtained heat conductive silicone composite sheet was pinched | interposed between the plates which consist of two sheets of aluminum, and the test body was produced. The test specimen was loaded with a compression load of 410 kPa, placed in an oven, placed at 0 ° C. for 30 minutes, and then placed at 125 ° C. for 30 minutes for 500 cycles. Then, the test body was observed visually and the presence or absence of the outflow of the intermediate | middle layer from between two aluminum plates was investigated.

・ Strength A force was applied by hand in the direction of tearing, and the strength was judged and evaluated according to the following criteria.

Evaluation A: Hard to tear Evaluation B: Easy tearing

（注）比較例４及び５では、シートの両面もしくは片面に粘着性が無く、アルミプレートと接着できなかったために、熱圧着後の熱抵抗を測定することができなかった。

(Note) In Comparative Examples 4 and 5, the both sides or one side of the sheet was not sticky and could not be bonded to the aluminum plate, so the thermal resistance after thermocompression bonding could not be measured.

  As is apparent from Table 1, each example has a low thermal resistance, excellent heat dissipation performance, and excellent pumping-out resistance and strength.

  On the other hand, in Comparative Example 1 using only the heat conductive silicone resin sheet, the strength was inferior and it was possible to tear easily. In Comparative Example 2 using the acrylic double-sided pressure-sensitive adhesive tape, the thermal resistance was remarkably increased due to the low thermal conductivity. In Comparative Example 3 in which heat-dissipating grease was used for the outer layer, the outflow of grease was observed after the heat cycle. When only the electrical insulating film used for the intermediate layer (A) is used (Comparative Example 4), or in the case of a two-layer structure (Comparative Example 5), since there is no adhesiveness on one or both sides, Adhesion was not obtained, and heat resistance measurement could not be performed.

  The thermally conductive silicone composite sheet of the present invention is useful as an electrically insulating thermally conductive member interposed between a heat generating electronic / electrical component and a heat radiating component.

Claims (12)

Having an intermediate layer (A) and a pair of outer layers (B) laminated on both sides of the intermediate layer (A);
The intermediate layer (A) is composed of a heat conductive synthetic resin film that is electrically insulating and heat resistant,
A pair of outer layers (B) is a heat conductive silicone composite sheet which consists of a heat conductive silicone resin composition which has adhesiveness and heat softening property.   The thermally conductive silicone resin composition has (a) a viscosity at 70 ° C. of 400 Pa.s. The thermally conductive silicone composite sheet according to claim 1, comprising a silicone resin having an adhesiveness of s or less and (b) a thermally conductive filler. The thermally conductive silicone composite sheet according to claim 2, wherein the silicone resin (a) comprises a silicone resin having a molecular composition represented by any of the following formulas (1) to (3).
Formula (1):
^{_{D m T φ p D Vi n}} (1)
(Where D is a dimethylsiloxane unit (ie, (CH ₃ ) ₂ SiO), T ^φ is a phenylsiloxane unit (ie, (C ₆ H ₅ ) SiO _3/2 ), and D ^Vi is a methylvinylsiloxane unit ( That is, (CH ₃ ) (CH ₂ = CH) SiO) is represented, and ((m + n) / p (molar ratio) = 0.25 to 4.0, (m + n) / m (molar ratio) = 1.0 to 4.0.)
Formula (2):
^{_{M L D m T φ p D}} Vi n (2)
(Where M represents a trimethylsiloxane unit (ie, (CH ₃ ) ₃ SiO _1/2 ), D, T ^φ and D ^Vi are as described above, and (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.
Formula (3):
^{_{M L D m Q q D Vi}} n (3)
(Q represents SiO _4/2 , M, D and D ^Vi are as described above, and (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.)   The thermally conductive silicone composite sheet according to claim 2 or 3, wherein the thermally conductive filler (b) is a metal powder, a metal oxide powder, a ceramic powder, or a combination thereof.   The thermally conductive filler (b) is aluminum powder, copper powder, silver powder, nickel powder, gold powder, aluminum oxide powder, aluminum hydroxide powder, silicon oxide powder, zinc oxide powder, magnesium oxide powder, iron oxide powder. 5. Titanium oxide powder, zirconium oxide powder, aluminum nitride powder, boron nitride powder, silicon nitride powder, diamond powder, carbon powder, fullerene powder, carbon graphite powder, or a combination of two or more thereof. A thermally conductive silicone composite sheet according to claim 1.   The thermally conductive silicone composite sheet according to any one of claims 2 to 5, wherein the thermally conductive filler (b) has an average particle size of 0.1 to 100 µm.   The heat conductive silicone composite sheet of any one of Claims 1-6 whose whole thickness is 50-1,000 micrometers.   The intermediate layer (A) includes (α) synthetic resin and (β) thermally conductive powder dispersed in the synthetic resin, and has a thermal conductivity of 0.3 W / m · K or more. Item 8. The thermally conductive silicone composite sheet according to any one of Items 1 to 7.   The thermally conductive silicone composite sheet according to claim 8, wherein the synthetic resin (α) is aromatic polyimide, polyamide, polyamideimide, polyester, fluorine-based polymer, or a combination of two or more thereof.   The thermally conductive powder (β) is at least one selected from zinc oxide powder, aluminum oxide powder, magnesium oxide powder, aluminum hydroxide powder, boron nitride powder, aluminum nitride powder, silicon carbide powder, and diamond powder. The thermally conductive silicone composite sheet according to claim 8 or 9, wherein   2. A sheet comprising a heat conductive silicone resin composition having adhesiveness and heat softening properties is bonded to both surfaces of an electrically insulating and heat resistant heat conductive synthetic resin film by room temperature pressure bonding or thermocompression bonding. The manufacturing method of the heat conductive silicone composite sheet of description.   The thermally conductive synthetic resin film includes (α) a synthetic resin and (β) a thermally conductive powder dispersed in the synthetic resin, and has a thermal conductivity of 0.3 W / m · K or more. The manufacturing method according to claim 11.