JP6136952B2 - Thermally conductive composite silicone rubber sheet - Google Patents

Description

  The present invention relates to a thermally conductive composite silicone rubber sheet excellent in workability, reworkability, and heat dissipation characteristics, which is suitable as an insulating sheet for heat dissipation of heat-generating electronic components and the like.

  Heat-generating electronic components such as power transistors and thyristors used in various electronic devices, and integrated circuit elements such as IC, LSI, CPU, and MPU have characteristics that deteriorate due to the generation of heat, and also reduce the life of the elements. Therefore, in order to perform heat dissipation smoothly, arrangement in the electronic device is considered. In addition, specific components or the entire device can be forcibly air-cooled with cooling fins, or heat can be released to the cooling member, board, or housing via a heat dissipation sheet (hereinafter referred to as heat dissipation sheet) for integrated circuit elements. Consideration is also made.

  However, in recent years, as electronic devices typified by personal computers have been highly integrated and the heat generation amount of the heat generating components and integrated circuit elements in the devices has increased, these components and elements have been used in conventional forced air cooling systems and heat dissipation sheets. In some cases, cooling or heat dissipation is insufficient. In particular, in the case of a portable laptop or notebook personal computer, a cooling method other than the forced air cooling method is required. As for the heat dissipation sheet, glass reinforced epoxy resin or polyimide resin with poor thermal conductivity is used as the material of the printed circuit board on which the element is formed. Can't escape. Therefore, a heat sink such as a natural cooling type or forced cooling type heat sink or heat pipe is installed in the vicinity of the element, and the heat generated by the element is transmitted to the heat sink via a heat dissipation medium to dissipate heat. Yes.

  In order to improve the heat conduction between the element and the radiator, a heat conductive grease for heat radiation or a heat radiating sheet having a thickness of about 0.2 to 10.0 mm is used as the heat radiating medium of this system. As a heat conductive grease for heat dissipation, for example, a heat conductive silicone grease in which a heat conductive filler such as silica fiber, zinc oxide, aluminum nitride or the like is blended with silicone oil is known (Patent Document 1). Many problems have occurred, such as the risk of such problems, the deterioration of the assembly workability of electronic components, the generation of voids due to the thermal history, and the decrease in thermal conductivity. On the other hand, as a heat-dissipating sheet, a well-filled, high-hardness silicone rubber layer reinforced with a cloth-like reinforcing material such as glass cloth is well known (Patent Document 2). This type of heat-dissipating sheet has a high hardness of the rubber layer, and is responsible for heat conduction and also has a role of ensuring insulation, which is very useful. However, since the heat radiating sheet has almost no surface tack, it is very difficult to mount and fix it to the heating element.

  In order to improve the workability of mounting and fixing, a heat-dissipating sheet in which a pressure-sensitive adhesive layer is provided on one or both sides of a high-hardness heat-conductive silicone rubber sheet, and the pressure-sensitive adhesive layer surface is further protected by a releasable protective sheet such as release paper Although the pressure-sensitive adhesive used for this has no thermal conductivity, the composite product as a whole has a low thermal conductivity, and in many cases the desired heat dissipation performance could not be obtained. Furthermore, in the case of this composite heat radiating sheet, the adhesive strength of the adhesive layer is stronger than the desired adhesive strength. In some cases, the pressure-sensitive adhesive layer was destroyed. Furthermore, it was necessary to perform a release agent treatment on the protective sheet on the adhesive layer surface, which was a factor in increasing costs.

  Furthermore, a heat-dissipating sheet in which a low-hardness heat conductive silicone rubber layer is laminated on a high-hardness heat-conductive silicone rubber sheet reinforced with a reinforcing material as described above is also disclosed (Patent Document 3). However, in the case of this composite type heat radiation sheet, since the total thickness is less than 0.45 mm due to manufacturing problems, the low hardness silicone rubber layer itself has good high thermal conductivity. However, the composite product as a whole cannot be thinned, and the thermal resistance is increased. In the case of a conventional composite heat dissipation sheet, generally, a high-hardness sheet is mainly laminated to improve the workability of the low-hardness sheet, and is composed of a thick low-hardness layer and a thin high-hardness layer. It was. However, in this configuration, since the low hardness layer is compressively deformed by pressure, it may be difficult to ensure insulation by ensuring space.

  Furthermore, in the production of a conventional laminated type sheet, it is necessary to add an adhesion assistant or apply a primer in order to achieve strong adhesion and prevent delamination. However, these methods have the disadvantage that the manufacturing process is complicated and the cost is increased, and the obtained sheet has a change in physical properties due to the reaction with time.

Japanese Patent Publication No.57-36302 Japanese Unexamined Patent Publication No. 56-161140 Japanese Patent Laid-Open No. 06-155517

As described above, the heat-dissipating sheet having a high hardness is excellent in insulation reliability in addition to heat dissipation due to its strength, but is disadvantageous in mounting workability. Further, when an adhesive layer is provided to improve the mounting workability, there is a problem that heat dissipation and reworkability are lowered and the cost is increased. In addition, the low-hardness / high-hardness composite sheet is difficult to reduce in thickness due to its structure, and it is difficult to guarantee space and insulation under high pressure. In addition, the manufacturing process is complicated, and there is a drawback that the change with time cannot be suppressed.
Accordingly, an object of the present invention is to provide a heat-dissipating sheet that is excellent in thermal conductivity, strength, and insulation, and excellent in mounting workability, reworkability, and long-term stability by a low-cost and simple manufacturing process. .

  In view of such circumstances, the inventor has conducted intensive research. As a result, the present inventors have included a thermally conductive filler, have a durometer A hardness of 60 to 100, and have a non-sticky surface. A thin heat-conductive silicone rubber layer containing a conductive rubber layer and a heat-conductive filler, having an Asker C hardness of 2 to 40, and having a slight surface adhesion, was sealed with a heat-conductive material. By laminating via a mesh reinforcement, a single-sided slightly-adhesive thermally conductive silicone rubber sheet with excellent workability, thermal conductivity, reworkability, insulation assurance, and long-term reliability can be obtained with a simple manufacturing process. The present invention has been found.

That is, the present invention
(X) High hardness / non-adhesive heat conductive rubber layer A heat conductive silicone rubber layer containing a heat conductive filler, having a durometer A hardness of 60 to 100, and having a non-sticky surface 0.05 to 0 .9mm
And (Y) low-hardness / slightly-adhesive heat conductive rubber layer, a heat-conductive silicone rubber layer containing a heat-conductive filler, having an Asker C hardness of 2 to 40, and having a slightly surface adhesiveness 0.01- 0.2mm
(Z) A mesh-like reinforcing material sealed with a heat conductive material 0.015-0.2 mm
Is a thermally conductive silicone rubber sheet laminated through the adhesive strength measured by a constant pressure penetration method using a solder paste adhesion tester (X) layer side: less than 10 gf, (Y) layer side: The present invention provides a thermally conductive composite silicone rubber sheet that is 10 to 100 gf.

  The thermally conductive composite silicone rubber sheet of the present invention has a mesh-like reinforcing material sealed with a thermally conductive material, and has a non-adhesive thermally conductive silicone rubber layer with high hardness and high strength, Excellent workability, insulation guarantee, and thermal conductivity. Furthermore, by laminating a thin, low-hardness, low-adhesion, heat-conductive silicone rubber layer, the thermal conductivity is improved by good contact without sacrificing workability and insulation assurance, resulting in fine adhesion. The sheet is provided with workability and reworkability. Further, by laminating the rubber layer via the mesh-like reinforcing material that is sealed, the contact area is remarkably increased and good adhesion is realized. Therefore, it is possible to prevent peeling without using an adhesion aid or primer, which is necessary for conventional laminated sheets, and as a result, it is possible to manufacture at low cost and in a simple process, and product characteristics are also improved. It will be stable over the long term.

The present invention will be described in detail below.
In the present invention, the thermally conductive silicone rubber layer is preferably a silicone rubber layer obtained by curing a composition containing (a) an organopolysiloxane, (b) a curing agent, and (c) a thermally conductive filler. .

(X) High hardness / non-adhesive thermally conductive rubber layer The high hardness / non-adhesive thermally conductive rubber layer of the present invention comprises (Xa) organopolysiloxane, (Xb) curing agent, and (Xc) thermally conductive filler. It is a silicone rubber layer which is obtained by curing a composition containing it, has a durometer A hardness of 60 to 100, and is non-sticky to the surface.

[(Xa) Organopolysiloxane]
The organopolysiloxane of component (Xa) has an average composition formula: R ¹ _a SiO _{(4-a) / 2} (wherein R ¹ is the same or different substituted or unsubstituted carbon atoms of 1 to 10, preferably 1, To a monovalent hydrocarbon group of 8 and a is a positive number of 1.90 to 2.05).
Examples of R ¹ include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, and octadecyl group; cyclopentyl group, cyclohexyl group Cycloalkyl groups such as phenyl groups, tolyl groups, xylyl groups, naphthyl groups, etc .; aralkyl groups such as benzyl groups, phenethyl groups, 3-phenylpropyl groups; 3,3,3-trifluoropropyl groups, 3 -Halogenated alkyl groups such as chloropropyl group; and alkenyl groups such as vinyl group, allyl group, butenyl group, pentenyl group and hexenyl group.

  As the organopolysiloxane of the component (Xa), generally, the main chain is composed of dimethylsiloxane units, or a part of the methyl groups in the main chain is vinyl group, phenyl group, 3, 3, 3 -Those substituted with a trifluoropropyl group or the like are preferable. Further, those having molecular chain ends blocked with a triorganosilyl group or a hydroxyl group are preferred, and examples of the triorganosilyl group include a trimethylsilyl group, a dimethylvinylsilyl group, and a trivinylsilyl group.

  Further, the degree of polymerization of the component (Xa) is preferably 20 to 12,000, and particularly preferably in the range of 50 to 10,000. The component (Xa) may be oily or gum-like, and may be selected according to a molding method or the like.

When the curing agent of the following component (Xb) is an addition reaction curing type containing an organohydrogenpolysiloxane and a platinum catalyst, the organopolysiloxane of the component (Xa) has a silicon atom-bonded alkenyl group in one molecule. 2 or more, preferably 3 or more. When the content of the silicon atom-bonded alkenyl group is less than the lower limit of the above range, the resulting composition will not be sufficiently cured. The alkenyl group bonded to the silicon atom is preferably a vinyl group. The alkenyl group may be at one or both of the molecular chain terminal and the side chain, and it is preferable that at least one alkenyl group is bonded to the silicon atom at the molecular chain terminal.
Specific examples in this case include, for example, a trimethylsiloxy group-capped dimethylsiloxane / methylvinylsiloxane copolymer at both ends of a molecular chain, a trimethylsiloxy group-capped methylvinylpolysiloxane at both ends of a molecular chain, and a trimethylsiloxy group-capped dimethyl at both molecular chains. Siloxane / methylvinylsiloxane / methylphenylsiloxane copolymer, dimethylpolysiloxane blocked with dimethylvinylsiloxy group at both ends of molecular chain, dimethylvinylsiloxy group-blocked methylvinylpolysiloxane with molecular chain at both ends, dimethylvinylsiloxy group-blocked dimethyl with molecular chain at both ends Siloxane / methylvinylsiloxane copolymer, dimethylvinylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer, both ends of molecular chain Alkoxy group-blocked dimethylpolysiloxane and the like. These can be used singly or in combination of two or more.

When the curing agent of the following component (Xb) is an organic peroxide, the organopolysiloxane of the component (Xa) is not particularly limited, but preferably has at least two alkenyl groups in one molecule.
Specific examples of this case include, for example, molecular chain both ends dimethylvinylsiloxy group-capped dimethylpolysiloxane, molecular chain both ends methylphenylvinylsiloxy group-capped dimethylpolysiloxane, molecular chain both ends dimethylvinylsiloxy group-capped dimethylsiloxane and methyl. Phenylsiloxane copolymer, dimethylvinylsiloxy group-blocked dimethylvinylsiloxy group at both ends of the molecular chain, trimethylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane copolymer at both ends of the molecular chain, dimethylvinylsiloxy at both ends of the molecular chain Blocked methyl (3,3,3-trifluoropropyl) polysiloxane, molecular chain both ends silanol-blocked dimethylsiloxane / methylvinylsiloxane copolymer, molecular chain both ends silanol-blocked dimethylsiloxane Examples thereof include methyl vinyl siloxane / methyl phenyl siloxane copolymer. These can be used singly or in combination of two or more.

[(Xb) curing agent]
When the component (Xb) is a hydrosilylation reaction curing agent, the curing agent is composed of an organohydrogenpolysiloxane having an average of two or more silicon-bonded hydrogen atoms in one molecule and a platinum-based catalyst. The organohydrogenpolysiloxane functions as a crosslinking agent that undergoes an addition reaction with the component (Xa) having an alkenyl group.
Specific examples of the organohydrogenpolysiloxane include, for example, molecular chain both ends trimethylsiloxy group-blocked methylhydrogenpolysiloxane, molecular chain both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, both molecular chains Terminal trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane / methylphenylsiloxane copolymer, molecular chain both ends dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, molecular chain both ends dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogen Siloxane copolymer, dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylphenylsiloxane copolymer, both ends of molecular chain dimethylhydro Enshirokishi groups at methylphenyl polysiloxane and the like. The component (Xb) can be used alone or in combination of two or more.

  In the composition constituting the outer layer of the composite sheet of this composition, the content of this organohydrogenpolysiloxane is usually silicon atoms in this component with respect to 1 mol of silicon atom-bonded alkenyl groups in component (Xa). The amount of bonded hydrogen atoms is usually 0.1 to 4.0 mol, preferably 0.3 to 2.0 mol. If the content of this component is too low, the resulting silicone rubber composition may not be sufficiently cured, while if it is too high, the resulting silicone rubber will be very hard and cause many cracks on the surface. May occur.

  The platinum-based catalyst used together with the organohydrogenpolysiloxane is a catalyst for accelerating the curing of the composition. For example, chloroplatinic acid, an alcohol solution of chloroplatinic acid, an olefin complex of platinum, an alkenylsiloxane complex of platinum, Examples include platinum carbonyl complexes. In the present composition, the content of the platinum-based catalyst is not particularly limited and may be an effective amount as a catalyst. However, the platinum metal in this component is in mass units with respect to the component (Xa), usually 0.01. It is the quantity which becomes -1,000 ppm, Preferably, it is the quantity which becomes 0.1-500 ppm. If the content of this component is too small, the resulting silicone rubber composition may not be cured sufficiently, while the curing rate of the resulting silicone rubber composition does not improve even when used in a large amount. It may be disadvantageous.

  When the curing agent for the component (Xb) is an organic peroxide, examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-bis (t-butyl). Peroxy) hexane, di-t-butyl peroxide, t-butyl perbenzoate and the like. These can be used singly or in combination of two or more. The amount of the organic peroxide added is preferably an amount that usually falls within the range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the organopolysiloxane as the component (Xa).

[(Xc) Thermally conductive filler]
As the thermally conductive filler of the component (Xc), inorganic powders such as aluminum oxide, zinc oxide, silicon oxide, silicon carbide, aluminum nitride, and boron nitride are preferably exemplified. Component (Xc) can be used alone or in combination of two or more.
The average particle diameter of this (Xc) component becomes like this. Preferably it is 50 micrometers or less, More preferably, it is 20 micrometers or less.

  Moreover, the compounding quantity of this (Xc) component is 100-100 mass parts normally with respect to 100 mass parts of (Xa) component, Especially the range of 200-1,600 mass parts is preferable. If the amount is too small, the thermal conductivity tends to be insufficient. On the other hand, if the amount is too large, uniform blending of the component (Xc) into the composition becomes difficult and the molding processability deteriorates. There is.

The rubber layer has a durometer A hardness of 60 to 100, more preferably 70 to 95. When the hardness is less than 60, the strength is lowered and it is difficult to guarantee the space. If the hardness is higher than 100, the rubber layer becomes brittle and may not be able to cope with bending and bending.
The thickness of the rubber layer is in the range of 0.05 to 0.9 mm. If it is less than 0.05 mm, the surface accuracy of the sheet may deteriorate. On the other hand, when the thickness is 0.9 mm or more, the heat conduction performance is lowered.

The adhesive strength of this rubber layer is less than 10 gf, more preferably less than 5 gf, as measured by a constant pressure penetration method using a solder paste adhesive strength tester. If the adhesive strength is 10 gf or more, stickiness or sticking may occur during mounting, and mounting workability may deteriorate.
In order to reduce the adhesive strength of the rubber layer to less than 10 gf, the surface of the rubber layer is partially exposed by increasing the hardness of the rubber layer so as not to cause surface tack, and by containing a filler having a large particle size. For example, a dusting process may be performed.

(Y) Low Hardness / Slightly Adhesive Thermally Conductive Rubber Layer The low hardness / slightly adhesive thermally conductive rubber layer of the present invention comprises (Ya) an organopolysiloxane, (Yb) a curing agent, and (Yc) a thermally conductive filler. A silicone rubber layer having a Asker C hardness of 2 to 40 and a slightly sticky surface is obtained by curing the composition.

[(Ya) Organopolysiloxane]
The organopolysiloxane of the (Ya) component has an average composition formula: R ² _b SiO _{(4-b) / 2} (wherein R ² is the same or different substituted or unsubstituted C 1-10, preferably 1 To 8 monovalent hydrocarbon groups, and b is a positive number of 1.90 to 2.05).
Examples of R ² include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, octadecyl group; cyclopentyl group, cyclohexyl group Cycloalkyl groups such as phenyl groups, tolyl groups, xylyl groups, naphthyl groups and the like; aralkyl groups such as benzyl groups, phenethyl groups and 3-phenylpropyl groups; 3,3,3-trifluoropropyl groups, 3 -Halogenated alkyl groups such as chloropropyl group; alkenyl groups such as vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group and the like.

  As the organopolysiloxane of this (Ya) component, generally, the main chain is composed of dimethylsiloxane units, or a part of the methyl group of the main chain is vinyl group, phenyl group, 3, 3, 3 -Those substituted with a trifluoropropyl group or the like are preferable. Further, those having molecular chain ends blocked with a triorganosilyl group or a hydroxyl group are preferred, and examples of the triorganosilyl group include a trimethylsilyl group, a dimethylvinylsilyl group, and a trivinylsilyl group.

  Further, the degree of polymerization of the (Ya) component is preferably 10 to 1,500, and particularly preferably 20 to 1,000. When the degree of polymerization exceeds 1,500, the fluidity of the composition becomes poor. The (Ya) component is preferably oily.

  The organopolysiloxane of the (Ya) component is an organopolysiloxane having an average of 0.5 or more, preferably 2 or more, silicon atom-bonded alkenyl groups in one molecule. Since this alkenyl group becomes a cross-linking point at the time of curing, basically, the composition does not cure unless there is a molecule containing two or more alkenyl groups in one molecule. Therefore, the number of alkenyl groups referred to here is the average number of alkenyl groups when the (Ya) component is a mixture of molecules containing 0, 1, 2, or more alkenyl groups in one molecule. Yes, when the distribution of alkenyl groups between molecules of the (Ya) component is uniform, it is necessary that one molecule contains two or more alkenyl groups.

When the content of the silicon atom-bonded alkenyl group is less than the lower limit of the above range, the resulting composition will not be sufficiently cured. The alkenyl group bonded to the silicon atom is preferably a vinyl group. The alkenyl group may be at one or both of the molecular chain terminal and the side chain, and it is preferable that at least one alkenyl group is bonded to the silicon atom at the molecular chain terminal.
Specific examples of this case include a trimethylsiloxy group-capped dimethylsiloxane / methylvinylsiloxane copolymer at both ends of a molecular chain, a trimethylsiloxy group-capped methylvinylpolysiloxane at both ends of a molecular chain, a trimethylsiloxy group-capped dimethylsiloxane at both ends of a molecular chain, Methyl vinyl siloxane / methyl phenyl siloxane copolymer, molecular chain both ends dimethyl vinyl siloxy group blocked dimethyl polysiloxane, molecular chain both ends dimethyl vinyl siloxy group blocked methyl vinyl polysiloxane, molecular chain both ends dimethyl vinyl siloxy group blocked dimethyl siloxane Methyl vinyl siloxane copolymer, both ends of molecular chain dimethyl vinyl siloxy group blocked dimethyl siloxane / methyl vinyl siloxane / methyl phenyl siloxane copolymer, both ends of molecular chain trivinyl siloxy group Chain dimethyl polysiloxane and the like. These can be used singly or in combination of two or more.

[(Yb) curing agent]
(Yb) The curing agent is composed of an organohydrogenpolysiloxane having an average of two or more silicon-bonded hydrogen atoms in one molecule and a platinum-based catalyst. The organohydrogenpolysiloxane functions as a crosslinking agent that undergoes an addition reaction with the (Ya) component having an alkenyl group.
Specific examples of this organohydrogenpolysiloxane include molecular chain both ends trimethylsiloxy group-blocked methylhydrogenpolysiloxane, molecular chain both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, molecular chain both ends trimethyl. Siloxy group-blocked dimethylsiloxane / methylhydrogensiloxane / methylphenylsiloxane copolymer, both ends of molecular chain dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, both ends of molecular chain dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane Polymer, dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylphenylsiloxane copolymer, dimethylhydrogensiloxane at both ends of molecular chain Carboxymethyl groups at methylphenyl polysiloxane and the like. The component (Yb) can be used alone or in combination of two or more.
In the present composition, the content of the organohydrogenpolysiloxane is usually such that the silicon atom-bonded hydrogen atom in this component is usually 0.1% relative to 1 mol of the silicon atom-bonded alkenyl group in the (Ya) component. The amount is 1 to 2.0 mol, preferably 0.3 to 1.5 mol. If the content of this component is too low, the resulting silicone rubber composition may not be sufficiently cured, while if it is too high, the resulting silicone rubber will be very hard, causing numerous cracks on the surface, Problems such as loss of adhesiveness may occur.

  The platinum-based catalyst used together with the organohydrogenpolysiloxane is a catalyst for accelerating the curing of the composition. For example, chloroplatinic acid, an alcohol solution of chloroplatinic acid, an olefin complex of platinum, an alkenylsiloxane complex of platinum, Examples include platinum carbonyl complexes. In the present composition, the content of the platinum-based catalyst is not particularly limited and may be an effective amount as a catalyst, but the platinum metal in this component is in mass units relative to the (Ya) component, and is usually 0.01. It is the quantity which becomes -1,000 ppm, Preferably, it is the quantity which becomes 0.1-500 ppm. If the content of this component is too small, the resulting silicone rubber composition may not be cured sufficiently, while the curing rate of the resulting silicone rubber composition does not improve even when used in a large amount. It may be disadvantageous.

[(Yc) Thermally conductive filler]
As the thermally conductive filler of the component (Yc), inorganic powders such as aluminum oxide, zinc oxide, silicon oxide, silicon carbide, aluminum nitride, and boron nitride are preferably exemplified. The component (Yc) can be used alone or in combination of two or more.
The average particle diameter of the component (Yc) is preferably 30 μm or less, more preferably 15 μm or less. In the present specification, “average particle diameter” means a volume-based cumulative average diameter. This “average particle diameter” can be measured by, for example, a particle size analyzer (manufactured by Nikkiso Co., Ltd., trade name: Microtrack MT3300EX).

  Moreover, the compounding quantity of this (Yc) component is 100-1800 mass parts normally with respect to 100 mass parts of (Ya) component, Preferably it is the range of 200-1,600 mass parts. If the blending amount is too small, the thermal conductivity becomes insufficient. On the other hand, if the blending amount is too large, uniform blending of the component (Yc) into the composition becomes difficult and the molding processability deteriorates. Moreover, the adhesiveness may be lost.

  The hardness of the rubber layer is 2 to 40, more preferably 5 to 30 in terms of Asker C hardness. When the hardness is 2 or less, the adhesiveness is strong and the strength is weak, so that the rubber layer may be destroyed at the time of reworking, and the reworkability is lowered. When the hardness is higher than 40, the adhesiveness of the surface is remarkably lowered and workability is lowered.

  The thickness of the rubber layer is in the range of 0.01 to 0.2 mm. If it is less than 0.01 mm, the surface accuracy of the sheet may deteriorate. On the other hand, if the thickness exceeds 0.2 mm, it is difficult to guarantee space. Moreover, adhesiveness rises and rework property falls.

The adhesive strength of the rubber layer is 10 to 100 gf, more preferably 20 to 80 gf, as measured by a constant pressure penetration method using a solder paste adhesive strength tester. If the adhesive strength is less than 10 gf, the adhesive strength is insufficient, and it becomes difficult to attach the sheet to a desired mounting position. On the other hand, if it exceeds 100 gf, rework becomes difficult. Moreover, since a peeling process is required for the protective film, the cost may increase.
In order to set the adhesive strength of the rubber layer to 10 to 100 gf, the surface tack of the rubber layer can be controlled by adjusting the hardness of the rubber layer, or an extremely thin layer having an appropriate adhesive strength can be provided on the surface. That's fine.

  The thermal conductivity of the silicone rubber layer used for the (X) layer and the (Y) layer is 1.0 W / m-K or more, more preferably 1.2 W / m-K or more. When the thermal conductivity is less than 1.0 W / m-K, the thermal conductivity characteristics are insufficient.

(Z) Mesh-like reinforcing material sealed with a heat conductive material Examples of the mesh-like reinforcing material used here include glass cloth, ceramic cloth, or organic fiber cloth such as nylon and polyester. The sealing material is not particularly limited as long as it is a heat conductive material, but is preferably a heat conductive silicone rubber material, and in consideration of cost and adhesion, it is a high hardness / non-adhesive heat conductive rubber layer. More preferably, it is the same as the material used.
The thickness of the mesh reinforcing material is 0.015 to 0.2 mm, and more preferably 0.03 to 0.15 mm. When the thickness of the mesh reinforcing material is too thin, the strength of the laminated sheet is remarkably lowered. On the other hand, if it exceeds 0.2 mm, the thermal conductivity may be significantly reduced.

[Production of heat conductive composite silicone sheet]
The method for producing the heat conductive composite silicone sheet of the present invention is not particularly limited, but generally a coating method such as a press method or a coating method is effective.

<Preparation of coating composition>
First, the organopolysiloxane and the thermally conductive filler are kneaded using a kneader, Banbury mixer, planetary mixer, Shinagawa mixer, or the like while being heated to a temperature of about 100 ° C. or higher as necessary. . In this kneading process, reinforcing silica such as fumed silica and precipitated silica; silicone oil, silicone wetter, etc .; platinum, titanium oxide, benzotriazole, etc. A flame retardant etc. may be added and mixed.
The homogeneous mixture obtained in the kneading step is cooled to room temperature, filtered through a strainer, etc., and then a required amount of curing agent is added to the mixture using a two-roll, Shinagawa mixer, etc. Knead. In this re-kneading step, acetylene compound-based addition reaction control agents such as 1-ethynyl-1-cyclohexanol, colorants such as organic pigments and inorganic pigments, and heat resistance improvers such as iron oxide and cerium oxide, if desired. In addition, an internal additive release agent or the like may be added and mixed.
The composition obtained in this re-kneading step may be directly used for the next step as a coating material, but if necessary, a solvent such as toluene is further added to a stirrer such as a planetary mixer or a kneader. It can be used as a coating material.

<Creating a closed mesh reinforcement>
The coating material obtained by the above process is applied to the mesh reinforcement. Sequentially, using a coating device such as a knife coater or kiss coater equipped with a drying furnace, a heating furnace and a winding device, after continuously applying to the mesh reinforcement, the solvent etc. is dried and evaporated, and the addition reaction curing type In the case of the above, it is heated to about 80 to 200 ° C., preferably about 100 to 150 ° C., and in the case of a peroxide curable type, it is heated to about 100 to 200 ° C., preferably about 110 to 180 ° C. A reticulated reinforcement is obtained.

<Composite>
A coating material to be a high-hardness, non-adhesive heat conductive rubber layer is applied to one side of the mesh-like reinforcing material obtained by the above process. Sequentially, using a coating device such as a knife coater or kiss coater equipped with a drying furnace, heating furnace and take-up device, it is applied to one side of the continuous mesh reinforcement, and then the solvent is dried and evaporated. In the case of an addition reaction curable type, it is heated to 80 to 200 ° C., preferably about 100 to 150 ° C., and in the case of a peroxide curable type, it is heated to 100 to 200 ° C., preferably about 110 to 180 ° C. And laminate.

  Further, a coating material that becomes a low hardness / low adhesion heat conductive rubber layer is applied to the other surface. Sequentially, using a coating device such as a knife coater or kiss coater equipped with a drying furnace, heating furnace and take-up device, it is applied to one side of the continuous mesh reinforcement, and then the solvent is dried and evaporated. The thermally conductive composite silicone rubber sheet of the present invention can be obtained by crosslinking and curing at 80 to 200 ° C., preferably about 100 to 150 ° C.

  When the obtained heat conductive composite silicone rubber sheet is continuously formed, the sheet is preferably wound and stored in a roll shape. In that case, it is desirable that the surface of the low-hardness / slightly adherent thermally conductive rubber layer is covered with a protective sheet. Without the protective sheet, the workability when the sheet is unwound from the roll shape deteriorates, and problems such as adhesion of foreign matter and dust to the low hardness, low adhesion heat conductive rubber layer may occur. .

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to the following Example.

  First, the following components for forming the heat conductive composite silicone sheet of the present invention were prepared.

<X layer: composition for high hardness / non-adhesive thermally conductive rubber layer>
Coating material X1:
(X1a) 100 parts by mass of dimethylpolysiloxane sealed at both ends with dimethylvinylsiloxy groups having an average degree of polymerization of 8,000, and (X1c) 750 masses of amorphous aluminum oxide powder having an average particle size of 4 μm as a thermally conductive filler Parts were kneaded at room temperature for 40 minutes with a Banbury mixer, then filtered with a 100 mesh strainer, and then, using two rolls, (X1b) di (2-methylbenzoyl) peroxide 1. 9 parts by mass and 0.4 part by mass of KE-color R20 (trade name: manufactured by Shin-Etsu Chemical Co., Ltd.) as a colorant were added and blended, and further kneaded to prepare a mixture.
Next, 100 parts by mass of the mixture obtained above was dissolved in 47 parts by mass of toluene to prepare a coating material X1a.

Coating material X2:
(X2a) 100 parts by mass of dimethylpolysiloxane sealed at both ends with dimethylvinylsiloxy groups having a viscosity of 600 mm ² / s at 25 ° C., (X2c1) 750 masses of aluminum oxide powder having an average particle size of 4 μm as a thermally conductive filler Part and (X2c2) 250 parts of boron nitride powder having an average particle size of 9 μm were kneaded at room temperature for 20 minutes with a planetary mixer and filtered with a 100 mesh strainer, and then (X2b1) chloroplatinic acid A vinyl siloxane complex (platinum metal content: 1% by mass) of 0.35 parts by mass is uniformly blended, and then 0.06 parts by mass of 1-ethynyl-1-cyclohexanol is added as an addition reaction control agent. Further, (X2b2) 1.5 parts by mass of methyl hydrogen polysiloxane represented by the following structural formula was uniformly mixed to produce silica The rubber composition was prepared.

  Next, 100 parts by mass of the mixture obtained above was dissolved in 20 parts by mass of toluene to prepare a coating material.

Coating material X3:
(X3a) 100 parts by mass of dimethylpolysiloxane sealed at both ends with dimethylvinylsiloxy groups having a viscosity of 600 mm ² / s at 25 ° C., (X3c) 750 masses of aluminum oxide powder having an average particle size of 4 μm as a heat conductive filler Parts were kneaded at room temperature for 20 minutes with a planetary mixer, filtered and finished with a 100 mesh strainer, and then (X3b1) a vinylsiloxane complex of chloroplatinic acid (platinum metal content: 1% by mass). 35 parts by mass is uniformly blended, then 0.06 parts by mass of 1-ethynyl-1-cyclohexanol is added and blended as an addition reaction control agent, and (X3b2) methyl hydrogen poly represented by the following structural formula A silicone rubber composition was prepared by uniformly mixing 3.0 parts by mass of siloxane.

Next, 100 parts by mass of the mixture obtained above was dissolved in 20 parts by mass of toluene to prepare a coating material.

<Y layer: composition for low hardness / low adhesion heat conductive rubber layer>
Coating material Y1:
(Y1a1) 65 parts by mass of dimethylpolysiloxane having both ends sealed with dimethylvinylsiloxy groups having a viscosity of 600 mm ² / s at 25 ° C., (Y1a2) dimethylvinylsiloxy groups having a viscosity of 30,000 mm ² / s at 25 ° C. 35 parts by weight of dimethylpolysiloxane sealed at both ends with (Y1c1) 300 parts by weight of an amorphous aluminum oxide powder having an average particle diameter of 6 μm as a heat conductive filler, and (Y1c2) an amorphous form having an average particle diameter of 1.5 μm 300 parts by weight of aluminum oxide powder and, as a wetter, 12 parts by weight of a dimethylpolysiloxane having one end-terminated trimethoxysilyl group blocked by the following structural formula were kneaded at room temperature for 20 minutes with a planetary mixer, and a 100 mesh strainer. And filtered through.

  Thereafter, (Y1b1) 0.6 parts by mass of a vinyl siloxane complex of chloroplatinic acid (platinum metal content: 1% by mass) was uniformly blended, and then 1-ethynyl-1-cyclohexanol as an addition reaction control agent. 2 parts by mass, and as an internally added mold release agent that promotes release from the separator, 3 parts by mass of KF-54, a phenyl-modified silicone oil manufactured by Shin-Etsu Chemical Co., Ltd. is added, and (Y1b2) is represented by the following structural formula A silicone rubber composition was prepared by uniformly mixing 9.5 parts by mass of methyl hydrogen polysiloxane.

  Next, 100 parts by mass of the mixture obtained above was dissolved in 25 parts by mass of toluene to prepare a coating material.

Coating material Y2:
(Y2a) 100 parts by mass of dimethylpolysiloxane sealed at both ends with a dimethylvinylsiloxy group having a viscosity of 600 mm ² / s at 25 ° C., (Y2c1) spherical aluminum oxide powder 1000 having an average particle size of 10 μm as a thermally conductive filler And (Y2c2) 650 parts by mass of amorphous aluminum oxide powder having an average particle size of 1.5 μm, and 35 parts by mass of a dimethylpolysiloxane having one terminal trimethoxysilyl group-blocked dimethylpolysiloxane represented by the following structural formula as a wetter The mixture was kneaded at room temperature for 20 minutes with a Lee mixer and filtered with a 100 mesh strainer.

  Thereafter, (Y2b1) 0.6 parts by mass of a vinylsiloxane complex of chloroplatinic acid (platinum metal content: 1% by mass) was uniformly blended, and then 1-ethynyl-1-cyclohexanol as an addition reaction control agent 3 parts by mass, and 5 parts by mass of KF-54, a phenyl-modified silicone oil manufactured by Shin-Etsu Chemical Co., Ltd. as an internal release agent that promotes release from the separator, and (Y2b2) is represented by the following structural formula A silicone rubber composition was prepared by uniformly mixing 11.0 parts by mass of methyl hydrogen polysiloxane.

  Next, 100 parts by mass of the mixture obtained above was dissolved in 25 parts by mass of toluene to prepare a coating material.

Coating material Y3:
A silicone rubber composition was prepared in the same manner as the coating material Y2, except that the amount of methyl hydrogen polysiloxane added to the coating material Y2 was changed to 10.3 parts by mass.
Next, 100 parts by mass of the mixture obtained above was dissolved in 25 parts by mass of toluene to prepare a coating material.

Coating material Y4:
A silicone rubber composition was prepared in the same manner as the coating material Y2, except that the amount of methyl hydrogen polysiloxane added to the coating material Y2 was changed to 10.0 parts by mass.
Next, 100 parts by mass of the mixture obtained above was dissolved in 25 parts by mass of toluene to prepare a coating material.

Coating material Y5:
A silicone rubber composition was prepared in the same manner as the coating material Y2, except that the amount of methyl hydrogen polysiloxane added to the coating material Y2 was changed to 16.0 parts by mass.
Next, 100 parts by mass of the mixture obtained above was dissolved in 25 parts by mass of toluene to prepare a coating material.

<Sealing mesh reinforcement>
After the dip coating of the coating liquid X1 on the glass cloth of IPC specification 1080, the sealing glass cloth formed into a thickness of 0.08 mm by processing under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. Formed.

<Example 1>
After coating the coating liquid X1 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.15 mm. . Further, the other side of the sealing glass cloth is comma-coated with the coating liquid Y1, and then processed under the conditions of a drying temperature of 80 ° C. and a curing temperature of 150 ° C. to form a composite sheet having a thickness of 0.2 mm. Got.

<Example 2>
After coating the coating liquid X2 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.4 mm. . Further, the other side of the sealing glass cloth is comma-coated with the coating liquid Y1, and then processed under the conditions of a drying temperature of 80 ° C. and a curing temperature of 150 ° C., and is formed to a thickness of 0.45 mm. Got.

<Example 3>
After coating the coating liquid X1 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.15 mm. . Further, the other side of the sealing glass cloth is comma-coated with the coating liquid Y2, and then processed under the conditions of a drying temperature of 80 ° C. and a curing temperature of 150 ° C., and formed into a thickness of 0.2 mm. Got.

<Example 4>
After coating the coating liquid X2 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.4 mm. . Further, the other surface of the sealing glass cloth is comma-coated with the coating liquid Y2, and then processed under the conditions of a drying temperature of 80 ° C. and a curing temperature of 150 ° C., and formed into a thickness of 0.45 mm. Got.

<Example 5>
After coating the coating liquid X2 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.4 mm. . Further, the other side of the sealing glass cloth is comma-coated with the coating liquid Y3, and then processed under the conditions of a drying temperature: 80 ° C. and a curing temperature: 150 ° C., and is formed into a thickness of 0.55 mm. Got.

<Example 6>
After coating the coating liquid X3 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.4 mm. . Further, the other surface of the sealing glass cloth is comma-coated with the coating liquid Y2, and then processed under the conditions of a drying temperature of 80 ° C. and a curing temperature of 150 ° C., and formed into a thickness of 0.45 mm. Got.

<Comparative Example 1>
After coating the coating liquid X1 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.15 mm. . Furthermore, the other side of the sealing glass cloth was comma-coated with KR-3700, a silicone adhesive made by Shin-Etsu Chemical Co., Ltd., and then treated under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a thickness. A composite sheet molded to 0.17 mm was obtained.

<Comparative example 2>
After coating the coating liquid X1 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.15 mm. . Further, the other side of the sealing glass cloth is comma-coated with the coating liquid X2, and then processed under the conditions of a drying temperature of 80 ° C. and a curing temperature of 150 ° C., and is formed into a thickness of 0.2 mm. Got.

<Comparative Example 3>
After coating the coating liquid X1 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.15 mm. . Further, the other surface of the sealing glass cloth is comma-coated with the coating liquid Y1, and then processed under the conditions of a drying temperature of 80 ° C. and a curing temperature of 150 ° C., and formed into a thickness of 0.155 mm. Got.

<Comparative example 4>
After coating the coating liquid X2 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.4 mm. . Further, the other surface of the sealing glass cloth is comma-coated with the coating liquid Y4, and then processed under the conditions of a drying temperature of 80 ° C. and a curing temperature of 150 ° C., and is formed to a thickness of 0.55 mm. Got.

<Comparative Example 5>
After coating the coating liquid Y5 on one side of the sealing glass cloth, it was processed under the conditions of drying temperature: 80 ° C. and curing temperature: 150 ° C. to obtain a composite sheet molded to a thickness of 0.4 mm. . Further, the other surface of the sealing glass cloth is comma-coated with the coating liquid Y2, and then processed under the conditions of a drying temperature of 80 ° C. and a curing temperature of 150 ° C., and formed into a thickness of 0.45 mm. Got.

[Evaluation methods of various characteristics]
About each composite sheet produced in the said Examples 1-6 and Comparative Examples 1-5, the various characteristics were measured with the following method. The measurement results are shown in Tables 1 and 2.

[General characteristics]
-Hardness of X layer and Y layer:
A sample for hardness measurement was separately prepared using the composition of each layer and measured in accordance with JIS K 6249 (measurement temperature 25 ° C.).

-Adhesive strength of X layer and Y layer:
Each layer of the composite sheet was measured by a constant pressure penetration method using a solder paste adhesion tester “TK-1” manufactured by Malcolm Corporation.

(Thermal characteristics)
-Thermal conductivity of X layer and Y layer:
The composition constituting each layer was press-molded so as to have a thickness of 6 mm using a mold, and this was measured as a measurement sample by a hot disk method according to ISO 22007-2.

・ Thermal resistance (cm ² -K / W)
The thermal resistance of the composite sheet under 50 psi pressure at 100 ° C. was measured according to ASTM D 5470.

[Workability / Reworkability]
The composite sheet was pressed against an aluminum plate that had a low hardness and slightly sticky side vertically, and the position of the sheet was confirmed. Also, it was confirmed that the composite sheet could be easily peeled off from the aluminum plate without breakage.

  From the above results, the products of the present invention can both hold and rework the sheet, and the pasting work is easy, whereas the comparative example cannot hold or rework the sheet or is pasted. It turns out that there is difficulty in work.

Claims (4)

(X) High hardness / non-adhesive heat conductive rubber layer A heat conductive silicone rubber layer containing a heat conductive filler, having a durometer A hardness of 60 to 100, and having a non-sticky surface 0.05 to 0 .9mm
And (Y) low-hardness / slightly adherent thermally conductive rubber layer containing a thermally conductive filler, Asker C hardness of 2-40, and thermally conductive silicone rubber layer 0.05- 0.15 mm
(Z) A mesh-like reinforcing material sealed with a heat conductive material 0.015-0.2 mm
Is a thermally conductive silicone rubber sheet laminated through the adhesive strength measured by a constant pressure penetration method using a solder paste adhesion tester (X) layer side: less than 10 gf, (Y) layer side: A thermally conductive composite silicone rubber sheet that is 10 to 100 gf.   The thermally conductive silicone rubber layer is a silicone rubber layer obtained by curing a composition containing (a) an organopolysiloxane, (b) a curing agent, and (c) a thermally conductive filler. The heat conductive composite silicone rubber sheet according to claim 1.   The thermal conductivity of the silicone rubber layer used for the (X) layer and the (Y) layer is 1.0 W / mK or more, The thermally conductive composite silicone rubber according to claim 1 or 2 Sheet. 4. The thermally conductive composite silicone rubber sheet according to claim 1, wherein only the surface of the (Y) layer is covered with a protective sheet and wound in a roll shape.