JP7719031B2 - Heat-resistant silicone composition, heat-resistant silicone sheet, and method for producing the same - Google Patents

Description

The present invention relates to a highly heat-resistant silicone composition, a heat-resistant silicone sheet, and a method for producing the same.

In recent years, the performance of semiconductors such as CPUs has improved dramatically, resulting in enormous increases in heat generation. Heat sinks are therefore attached to heat-generating electronic components, and thermally conductive silicone sheets are used to improve adhesion between the semiconductor and the heat sink. As devices become smaller, their performance improves, and they become more highly integrated, thermally conductive silicone sheets are required to be soft and have high thermal conductivity. Patent Document 1 proposes a silicone thermally conductive material containing a phthalocyanine compound. Patent Document 2 proposes a gel material containing a phthalocyanine compound with improved thermal stability. Patent Document 3 proposes a silicone resin with improved heat resistance due to the introduction of Si-O-Ce and Si-O-Ti bonds. Patent Document 4 proposes a thermally conductive material to which a discotic polycyclic aromatic compound with an organic functional group has been added.

Special table 2014-503680 publication Special Publication No. 2014-534292 Japanese Patent Application Laid-Open No. 2019-167473 Retable No. 2017-131007

However, while conventional thermally conductive silicone sheets have relatively high heat resistance, even higher heat resistance is required. Specifically, increasing the thermal conductivity of silicone sheets requires increasing the amount of filler or using highly thermally conductive fillers, which can cause the sheets to harden at high temperatures, and this problem needed to be improved. Similarly, heat resistance is also important in sealants, heat insulating agents, electromagnetic wave absorbers, and other applications.

To solve the above-mentioned problems of the prior art, the present invention provides a highly heat-resistant silicone composition using an organic heat resistance improver, a heat-resistant silicone sheet, and a method for producing the same.

The present invention provides a heat-resistant silicone composition comprising a silicone polymer and a heat resistance improver,
The heat resistance improver is a gardenia pigment, and the gardenia pigment is contained in an amount of 0.01 to 10 parts by mass per 100 parts by mass of the silicone polymer.

The heat-resistant silicone sheet of the present invention is characterized by being formed into a sheet by at least one molding method selected from sheet molding and press molding, and then cured.

The method for producing a heat-resistant silicone sheet of the present invention is characterized by mixing the silicone composition described above, molding it using at least one molding method selected from sheet molding and press molding, and then curing it.

The present invention provides a heat-resistant silicone composition containing a silicone polymer and a heat resistance improver, in which the heat resistance improver is gardenia pigment, thereby providing a highly heat-resistant silicone composition and silicone sheet. Specifically, it provides a heat-resistant silicone composition and heat-resistant silicone sheet that do not harden even at high temperatures, which is a major advantage for heat-generating parts, including semiconductors. Furthermore, gardenia pigment is known as an edible pigment, is highly safe, does not contain environmental pollutants, and does not pose a risk of curing inhibition.

FIG. 1 is a schematic cross-sectional view showing a method of using a thermally conductive sheet according to one embodiment of the present invention. 2A and 2B are explanatory diagrams showing a method for measuring the thermal conductivity of a sample in one embodiment of the present invention.

The present invention is a heat-resistant silicone composition containing a silicone polymer and a heat resistance improver. The heat resistance improver is a gardenia pigment. Gardenia pigments include gardenia red, gardenia yellow, gardenia blue, and gardenia green, all of which are commercially available as food additives. The mechanism by which heat resistance is improved by adding these pigment compounds is not clear, but it is thought that these pigment compounds absorb or suppress substances that cause thermal decomposition, such as thermal radicals generated at high temperatures.

Common pigments contain metals (copper, sulfur, cobalt, etc.), and many of them are subject to environmental regulations, and some of them contain metal ions that can adversely affect electronic components such as semiconductors. Sulfur also inhibits the curing of silicones and should be avoided.
In contrast, gardenia pigment is known as an edible pigment, does not pollute the environment, does not have any adverse effects on electronic components due to metal ions, and does not have the problem of inhibiting the curing of silicone.
Crocin, represented by the following chemical formula (Chemical Formula 1), is known as an example of gardenia pigment (yellow).

The gardenia pigment is preferably contained in an amount of 0.00001 to 10 parts by mass per 100 parts by mass of silicone polymer, more preferably 0.0001 to 5 parts by mass, even more preferably 0.001 to 5 parts by mass, and particularly preferably 0.01 to 5 parts by mass. This range improves heat resistance. The heat resistance improver is preferably diluted in silicone oil and added. This allows for a uniform composition. Alternatively, it can be diluted in warm water. The gardenia pigment may also be used as a masterbatch with the silicone polymer. The silicone polymer may be a curable silicone polymer or a silicone polymer without reactive groups, or a combination of both.

The heat-resistant silicone composition is preferably in the form of a grease, putty, gel, or rubber. Because grease and putty compositions are liquid, they are preferably filled into a dispenser for use. The gel or rubber composition is preferably formed into a sheet by at least one molding method selected from sheet molding and press molding, and then cured. In press molding, each molded product may be press-molded into a different shape. Press molding is also called mold clamping molding.

The heat-resistant silicone composition of the present invention preferably contains at least one filler selected from inorganic fillers and organic fillers. The filler is preferably contained in an amount of 1 to 7,000 parts by mass, more preferably 10 to 6,000 parts by mass, and even more preferably 50 to 5,000 parts by mass, per 100 parts by mass of the heat-resistant silicone polymer.

The hardness and viscosity of the silicone composition are not particularly specified. In the case of heat-resistant silicone compositions containing non-reactive silicone oil or gum and a heat-resistant additive, the viscosity is 0.65 mPa·sec to 1,000,000 mPa/sec, more preferably 50 mPa·sec to 100,000 mPa/sec. When used as a filler-free cured silicone gel, a post-curing penetration of 20 or more is preferred, with 40 or more being more preferred to ensure sufficient penetration (softness) for the silicone gel. When used as a flexible sheet-shaped cured product containing a filler, an Asker C hardness of 70 or less after curing is preferred, with 50 or less being more preferred. An Asker C hardness of 70 or less ensures sufficient hardness (softness). Furthermore, when used as a sheet-shaped cured product, it is important that the sheet is flexible enough to maintain flexibility when sandwiched between components. In terms of flexibility, it is preferable that the sheet bends freely at an angle of 90° or more with little force, and it is particularly preferable that the sheet's flexibility does not decrease with thermal degradation. The degree of flexibility is preferably 30°, and more preferably 45°. Furthermore, when used as a molded silicone rubber material, it is preferable that it exhibits a rubber-like property, with a durometer A hardness of 20 to 90, and even more preferably 30 to 80. When curing and crosslinking a silicone polymer to obtain a silicone sheet-like cured product, the curing method is not limited. Examples include the addition reaction of alkenyl groups with SiH groups, the crosslinking of alkenyl groups or alkyl groups using peroxides, the condensation of silanol or alkoxy groups, and a combination of these crosslinking methods. Among these, the method of curing by the addition reaction of alkenyl groups with SiH groups using a catalyst such as platinum is preferred because it does not produce by-products, the reaction rate can be controlled, and the curing reaction proceeds smoothly deep into the molded product.

The heat-resistant silicone composition of the present invention is preferably molded into a sheet. When molded into a sheet, it is suitable for mounting on electronic components, etc. The thickness of the heat-resistant silicone sheet containing the thermally conductive filler is preferably in the range of 0.2 to 10 mm. Furthermore, the thermal conductivity of the thermally conductive sheet is preferably 0.8 W/m·K or higher, more preferably 1.0 W/m·K or higher. A thermal conductivity of 0.8 W/m·K or higher is suitable for conducting heat from a heat-generating component to a heat sink. Such a heat-resistant and thermally conductive silicone sheet is suitable for TIM (Thermal Interface Material) applications.

An example of a heat-resistant silicone composition is described below. Regarding heat-resistant silicone compositions in oil or gum form, they comprise the following components (E) and (H), with 0.001 to 10 parts by mass of component (E) per 100 parts by mass of component (H). Furthermore, gel or rubber-like heat-resistant silicone compositions or heat-resistant silicone sheets preferably contain components (A) to (C) and (E), and optional components (F), (G), and (H), which are mixed, molded into a sheet, and cured. Furthermore, heat-resistant and thermally conductive silicone sheets preferably contain the following components (A) to (E), and optional components (F), (G), and (H), which are mixed, molded into a sheet, and cured.
(A) base polymer component: an organopolysiloxane containing, on average, one or more silicon atoms bonded to an alkenyl group per molecule; (B) crosslinking component: an organopolysiloxane containing, on average, one or more silicon atoms bonded to a hydrogen atom per molecule, in an amount of 0.01 to 3 moles per mole of silicon-bonded alkenyl groups in Component A; (C) catalyst component: a platinum group metal catalyst in an amount of 0.01 to 1,000 ppm, in metal atom weight units, relative to Component A; (D) inorganic or organic filler: 1 to 7,000 parts by mass per 100 parts by mass of the addition-curable silicone polymer component (Component A + Component B); (E) heat resistance improver: 0.001 to 10 parts by mass per 100 parts by mass of the addition-curable silicone polymer component (Component A + Component B); and (F) silane coupling agent: an additional 0.1 to 10 parts by mass may be added per 100 parts by mass of the addition-curable silicone polymer component (Component A + Component B).
(G) Inorganic particle pigment: 0.5 to 10 parts by mass may be added to 100 parts by mass of the addition-curing silicone polymer component (Component A + Component B).
(H) Organopolysiloxane having no addition curing reactive groups: This may be added in an amount of 0.5 to 50 parts by weight per 100 parts by weight of the addition curing silicone polymer (Component A + Component B).

Each component will be described below.
(1) Base polymer component (component A)
The base polymer component is an organopolysiloxane containing one or more silicon-bonded alkenyl groups per molecule, and an organopolysiloxane containing two alkenyl groups is the main component (base polymer component) in the heat-resistant silicone composition and heat-resistant silicone sheet of the present invention. This organopolysiloxane contains two or more silicon-bonded alkenyl groups per molecule, such as vinyl or allyl groups, having 2 to 8 carbon atoms, preferably 2 to 6 carbon atoms. From the standpoint of workability and curability, a viscosity of 10 to 100,000 mPa·s at 25°C, and particularly 100 to 10,000 mPa·s, is desirable.

An example of the base polymer is an organopolysiloxane represented by the following chemical formula (Chemical Formula 2), which contains an average of one or more alkenyl groups per molecule, bonded to silicon atoms at both ends of the molecular chain. The other substituents are linear or branched organopolysiloxanes capped with alkyl or phenyl groups. From the perspective of workability and curability, a viscosity of 10 to 100,000 mPa·s at 25°C is desirable. This organopolysiloxane may contain a branched structure (trifunctional siloxane unit) in the molecular chain, or may have alkenyl groups in the side chains.
In the formula, R ^{1 '} s are the same or different unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, R ² is an alkenyl group, and k is 0 or a positive integer. Here, the unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond for ^R1 preferably has, for example, 1 to 10 carbon atoms, and particularly preferably 1 to 6 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine, bromine, or chlorine, or with a cyano group, such as a halogen-substituted alkyl group such as a chloromethyl group, a chloropropyl group, a bromoethyl group, or a trifluoropropyl group; and a cyanoethyl group. The alkenyl group for ^R2 preferably has 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms, and specific examples include vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, and cyclohexenyl groups, with vinyl being preferred. In the above chemical formula (Chemical Formula 2), k is generally 0 or a positive integer satisfying 0≦k≦10000, preferably 5≦k≦2000, and more preferably 10≦k≦1200.
The organopolysiloxane of component A may be an organopolysiloxane having three or more, typically 3 to 30, and preferably 3 to 20, alkenyl groups, such as vinyl or allyl groups, bonded to silicon atoms having 2 to 8, particularly 2 to 6, carbon atoms per molecule. The molecular structure may be linear, cyclic, branched, or three-dimensional network. A preferred organopolysiloxane is one having a main chain consisting of repeating diorganosiloxane units, both molecular chain terminals capped with triorganosiloxy groups, and a viscosity at 25°C of 10 to 100,000 mPa s, particularly 100 to 10,000 mPa s.

The alkenyl group may be bonded to any part of the molecule. For example, it may be bonded to a silicon atom at the molecular chain terminal or a non-terminal (mid-chain) location. Among these, a linear organopolysiloxane having one to three alkenyl groups on each of the silicon atoms at both molecular chain terminals, as represented by the following chemical formula (Chemical Formula 3): (However, if the total number of alkenyl groups bonded to the terminal silicon atoms is less than three, then the linear organopolysiloxane has at least one alkenyl group bonded to a non-terminal (mid-chain) silicon atom (for example, as a substituent in a diorganosiloxane unit). As mentioned above, from the viewpoints of workability and curability, a linear organopolysiloxane having a viscosity of 10 to 100,000 mPa·s at 25°C is desirable. This linear organopolysiloxane may also contain a small amount of branched structures (trifunctional siloxane units) in the molecular chain.

In the formula, ^R3 's are the same or different and are unsubstituted or substituted monovalent hydrocarbon groups, at least one of which is an alkenyl group, ^R4 's are the same or different and are unsubstituted or substituted monovalent hydrocarbon groups that do not have an aliphatic unsaturated bond, ^R5 is an alkenyl group, and l and m are 0 or positive integers. Here, the monovalent hydrocarbon group for ^R3 is preferably one having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl; and groups in which some or all of the hydrogen atoms have been substituted with halogen atoms such as fluorine, bromine, or chlorine, or with cyano groups, such as halogen-substituted alkyl groups such as chloromethyl, chloropropyl, bromoethyl, and trifluoropropyl, and cyanoethyl groups.
The monovalent hydrocarbon group for ^R4 is preferably one having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms, and includes the same examples as those for ^R1 above, except that alkenyl groups are not included. The alkenyl group for ^R5 is preferably one having 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms, and specific examples include the same as those for ^R2 in the above chemical formula (Chemical Formula 2), with a vinyl group being preferred.

L and m are generally 0 or positive integers that satisfy 0 < l + m ≦ 10000, preferably 5 ≦ l + m ≦ 2000, more preferably 10 ≦ l + m ≦ 1200, and are integers that satisfy 0 < l/(l + m) ≦ 0.2, preferably 0.0011 ≦ l/(l + m) ≦ 0.1.

(2) Crosslinking component (B component)
The organohydrogenpolysiloxane of component B of the present invention acts as a crosslinking agent, forming a cured product through an addition reaction (hydrosilylation) between the SiH groups in this component and the alkenyl groups in component A. Any organohydrogenpolysiloxane may be used as long as it has two or more hydrogen atoms bonded to silicon atoms (i.e., SiH groups) per molecule. The molecular structure of this organohydrogenpolysiloxane may be linear, cyclic, branched, or a three-dimensional network structure, but those with a number of silicon atoms per molecule (i.e., degree of polymerization) of 2 to 1000, and particularly 2 to 300, can be used.

The position of the silicon atom to which the hydrogen atom is bonded is not particularly limited, and it may be at the end of the molecular chain or in a side chain. In addition, examples of organic groups bonded to silicon atoms other than hydrogen atoms include unsubstituted or substituted monovalent hydrocarbon groups that do not have an aliphatic unsaturated bond, similar to ^R1 in the above chemical formula (Chemical Formula 2).

An example of the organohydrogenpolysiloxane of component B is represented by the following chemical formula (Chemical Formula 4).

In the above formula, ^R6s are the same or different and are each an alkyl group, a phenyl group, an epoxy group, an acryloyl group, a methacryloyl group, an alkoxy group, or a hydrogen atom, and at least one R6 is a hydrogen atom. L is an integer of 0 to 1,000, particularly an integer of 0 to 300, and M is an integer of 1 to 200.

(3) Catalyst component (C component)
The catalyst component of Component C is a component that accelerates the curing of the present composition. Catalysts used in hydrosilylation reactions can be used as Component C. Examples include platinum black, chloroplatinic acid, chloroplatinic acid, reaction products of chloroplatinic acid with monohydric alcohols, complexes of chloroplatinic acid with olefins or vinylsiloxanes, platinum-based catalysts such as platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts. The amount of Component C to be added is sufficient to achieve curing, and can be adjusted appropriately depending on the desired curing rate, etc. It is preferable to add 0.01 to 1,000 ppm by weight of metal atoms to Component A.

(4) Inorganic or organic filler (component D)
The inorganic filler is preferably at least one inorganic filler selected from thermally conductive inorganic fillers, electromagnetic wave absorbing inorganic fillers, inorganic fillers for improving heat insulation, and inorganic fillers for improving strength. Thermally conductive inorganic fillers include alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, silicon carbide, silica, etc. These may be added alone or in combination. The electromagnetic wave absorbing inorganic filler includes soft magnetic metal powder or oxide magnetic powder (ferrite powder). Soft magnetic metal powders include Fe-Si alloys, Fe-Al alloys, Fe-Si-Al alloys (Sendust), Fe-Si-Cr alloys, Fe-Ni alloys (Permalloy), Fe-Ni-Co alloys (Mumetal), Fe-Ni-Mo alloys (Supermalloy), Fe-Co alloys, Fe-Si-Al-Cr alloys, and Fe-Si-B alloys. Examples of ferrite powders include spinel ferrites such as Mn-Zn ferrite, Mn-Mg-Zn ferrite, Mg-Cu-Zn ferrite, Ni-Zn ferrite, Ni-Cu-Zn ferrite, and Cu-Zn ferrite, and hexagonal ferrites such as W-type, Y-type, Z-type, and M-type, but it is preferable to use carbonyl iron powder. All of these are magnetic powders.

Examples of inorganic fillers that improve insulation include glass balloons, silica balloons, shirasu balloons, carbon balloons, alumina balloons, and zirconia balloons, with glass balloons being preferred. All of these improve the insulating effect. Organic fillers that improve insulation can also be used in place of or in combination with the inorganic fillers that improve insulation. Examples of organic fillers that improve insulation include phenol balloons, acrylonitrile balloons, and vinylidene chloride balloons.

Examples of strength-enhancing fillers include silica, glass fiber, carbon fiber, cellulose nanofiber, graphite, and graphene, with silica being preferred. All of these fillers improve the strength of the silicone composition or cured sheet.
In this specification, inorganic fillers are also referred to as inorganic particles.

In the case of a thermally conductive filler, it is preferable to add 1 to 7,000 parts by mass, preferably 100 to 4,000 parts by mass, per 100 parts by mass of the addition-curing silicone polymer component (Component A + Component B). This allows the heat-resistant thermally conductive composition and heat-resistant thermally conductive sheet to have a thermal conductivity of 0.8 W/m·K or higher. The thermally conductive filler is preferably at least one selected from alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, silicon carbide, and silica. Various shapes, such as spherical, scaly, and polyhedral, can be used. The specific surface area of the thermally conductive filler is preferably in the range of 0.06 to 15 m ² /g. The specific surface area is the BET specific surface area, and is measured in accordance with JIS R1626. When using an average particle size, a range of 0.1 to 100 μm is preferable. The particle size is measured by measuring the D50 (median diameter) of the cumulative particle size distribution on a volume basis using a laser diffraction/light scattering method. An example of the measuring device is the LA-950S2 laser diffraction/scattering particle distribution measuring device manufactured by Horiba, Ltd.

Inorganic fillers may be used in combination with at least two particles with different average particle sizes. This allows particles with smaller diameters to be embedded between larger particles, resulting in a nearly close-packed state, which improves properties such as thermal conductivity, insulation, electromagnetic wave absorption, and material strength.

The inorganic filler may be surface-treated in part or in whole with a silane coupling agent. The silane coupling agent may be pre-mixed with the inorganic filler and heat-treated (pretreatment method), or it may be added when mixing the base polymer, curing catalyst, and inorganic particles (integral blend method). In the case of the pretreatment method and integral blend method, it is preferable to add 0.01 to 10 parts by mass of silane coupling agent per 100 parts by mass of inorganic filler. Surface treatment makes it easier to fill the base polymer and also prevents the curing catalyst from being adsorbed onto the inorganic filler, preventing curing inhibition. This is useful for storage stability.

The silane coupling agent is preferably a silane compound represented by the formula R _a Si(OR') _4-a (R is an unsubstituted or substituted organic group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1), or a partial hydrolyzate thereof. Examples of the alkoxysilane compound (hereinafter simply referred to as "silane") include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane. These silane compounds can be used alone or in combination. As the surface treatment agent, alkoxysilane and one-terminated silanol siloxane or one-terminated trimethoxysilyl polysiloxane may be used in combination. The surface treatment here includes not only covalent bonding but also adsorption.

(5) Heat resistance improver (component E)
Component E may be added as a powder or may be used in the form of a masterbatch with a polymer. The polymer used in the masterbatch is preferably a silicone polymer, and may be a curable silicone polymer, a silicone polymer without reactive groups, or a combination of both.

(6) Other Additives Components other than those described above can be blended into the composition of the present invention as needed. For example, heat resistance improvers such as red iron oxide and titanium oxide, flame retardant assistants, and cure retarders may be added. Organic or inorganic particle pigments may be added for coloring or toning purposes. Alkoxy group-containing silicones may be added as materials for filler surface treatment, etc. Organopolysiloxanes without addition cure reactive groups may also be added. From the standpoint of workability, a viscosity at 25°C of 10 to 100,000 mPa·s, and particularly 100 to 10,000 mPa·s, is desirable.

The method for producing the heat-resistant silicone sheet of the present invention involves mixing the aforementioned components (A) to (C), (E), and, if necessary, optional components to form a composition, which is then molded into a sheet and cured. The sheet is preferably molded by sandwiching the entire composition between polyethylene terephthalate (PET) films, rolling it into a sheet, and curing it at 80 to 150°C for 10 to 120 minutes.

The following description will be made with reference to the drawings. In the following drawings, the same reference numerals indicate the same parts. Figure 1 is a schematic cross-sectional view of a heat dissipation structure 10 incorporating a thermally conductive sheet according to one embodiment of the present invention. Thermally conductive sheet 11b dissipates heat generated by electronic components 13, such as semiconductor devices. It is fixed to the main surface 12a of heat spreader 12 facing the electronic components 13 and is sandwiched between the electronic components 13 and heat spreader 12. Thermally conductive sheet 11a is sandwiched between heat spreader 12 and heat sink 15. Thermally conductive sheets 11a and 11b, together with heat spreader 12, constitute a heat dissipation member that dissipates heat from the electronic components 13. Heat spreader 12 is formed, for example, in the shape of a rectangular plate and has a main surface 12a facing the electronic components 13 and a sidewall 12b extending along the outer periphery of main surface 12a. The heat spreader 12 has a thermally conductive sheet 11b on its main surface 12a, surrounded by side walls 12b, and a heat sink 15 on its other surface 12c, opposite the main surface 12a, via the thermally conductive sheet 11a. The electronic component 13 is, for example, a semiconductor element such as a BGA, and is mounted on a wiring board 14.

The present invention will be described below using examples, but is not limited to these examples. Various parameters were measured by the following methods.
<Thermal conductivity>
The thermal conductivity of the thermally conductive silicone sheet was measured using a hot disk (compliant with ISO 22007-2). As shown in Figure 1A, this thermal conductivity measuring device 1 sandwiches a polyimide film sensor 2 between two samples 3a and 3b, applies a constant power to the sensor 2, and generates a constant amount of heat, analyzing the thermal characteristics from the temperature rise of the sensor 2. The sensor 2 has a 7 mm diameter tip 4 and, as shown in Figure 1B, has a double spiral electrode structure with an applied current electrode 5 and a resistance electrode (temperature measurement electrode) 6 located at the bottom. The thermal conductivity is calculated using the following equation (Equation 1):
<Hardness>
The Asker C hardness was measured using a rubber hardness tester specified in JIS K 7312.

Example 1
1. Raw Material Component (1) Base Polymer: A two-component addition-cure silicone polymer was used that becomes a silicone gel after curing. One component (Component A) contains the base polymer component (Component A) and a platinum group metal catalyst (Component C), while the other component (Component B) contains the base polymer component (Component A) and a crosslinker component (Component B), an organohydrogenpolysiloxane.
(2) Heat Resistance Improver Gardenia pigment (red) manufactured by Kyoritsu Foods Co., Ltd. was used in an amount of 2 g per 100 g of the base polymer.
(3) Thermally conductive filler As the thermally conductive filler, 600 g of spherical alumina having an average particle size of 35 μm was added to 100 g of the base polymer.
2. Mixing and Molding of Cured Product The base polymer, thermally conductive filler, and heat resistance improver were mixed uniformly to form a compound (composition).
This compound (composition) was sandwiched between polyester (PET) films and passed through rolls to form a sheet, which was then heated at 100°C for 30 minutes to obtain a cured silicone sheet with a thickness of 2 mm.
The curability was evaluated as follows:
A: The shape is maintained and the PET film can be peeled off cleanly.
B: Viscosity increases, but shape is not maintained.
C: The viscosity does not change from the compound composition.
(4) Measurement of Hardness Five of the 2 mm thick cured sheets were stacked and placed in an oven heated to 220° C. The hardness was measured using an Asker C hardness tester before and after 100 hours in the oven.

Example 2
The same procedure as in Example 1 was carried out except that gardenia pigment (yellow) manufactured by Kyoritsu Foods Co., Ltd. was used.

Example 3
The same procedure as in Example 1 was carried out except that gardenia pigment (blue) manufactured by Kyoritsu Foods Co., Ltd. was used.

Example 4
The same procedure as in Example 1 was carried out except that gardenia pigment (green) manufactured by Kyoritsu Foods Co., Ltd. was used.

(Comparative Example 1)
The same procedure as in Example 1 was carried out except that gardenia pigment was not added.
The above conditions and results are summarized in Tables 1 and 2.

As is clear from Tables 1 and 2, in Examples 1 to 4, the hardness changed little after 100 hours of the 220° C. heat resistance test, and it was confirmed that the heat resistance was high.
In contrast, Comparative Example 1, which did not contain a heat-resistant additive, showed a large change in hardness and low heat resistance, which was not preferable.

The heat-resistant silicone composition and heat-resistant silicone sheet of the present invention are suitable for placement between heat-generating parts of electrical and electronic components and heat sinks. In particular, the use of a heat resistance improver that does not contain metal atoms to create a heat-resistant silicone composition and heat-resistant silicone sheet that does not harden even at high temperatures offers significant advantages for electronic and electrical components.

1 Thermal conductivity measuring device 2 Sensors 3a, 3b Sample 4 Sensor tip 5 Applied current electrode 6 Resistance value electrode (temperature measurement electrode)
10 Heat dissipation structure 11a, 11b Thermally conductive sheet 12 Heat spreader 12b Heat spreader side wall 13 Electronic component 14 Wiring board 15 Heat sink

Claims (10)

A heat-resistant silicone composition comprising a silicone polymer and a heat resistance improver,
the heat resistance improver is a gardenia pigment,
The heat-resistant silicone composition contains the gardenia pigment in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the silicone polymer. The heat-resistant silicone composition according to claim 1, wherein the gardenia pigment is diluted in silicone oil and added. 2. The heat-resistant silicone composition according to claim 1, wherein the heat-resistant silicone composition is in at least one state selected from the group consisting of grease, putty, gel , and rubber. 2. The heat-resistant silicone composition according to claim 1, further comprising at least one filler selected from the group consisting of inorganic fillers and organic fillers. The heat-resistant silicone composition according to claim 4, wherein the filler is contained in an amount of 1 to 7,000 parts by mass per 100 parts by mass of the silicone polymer. 5. The heat-resistant silicone composition according to claim 4, wherein the filler is at least one inorganic particle selected from the group consisting of alumina , zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, silicon carbide, and silica. The heat-resistant silicone composition according to claim 4, wherein the filler is an inorganic filler, and at least a portion of the filler has been surface-treated with a silane compound represented by the formula R _a Si(OR') _3-a (R is an unsubstituted or substituted organic group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1), or a silane coupling agent that is a partial hydrolyzate thereof. The heat-resistant silicone composition according to claim 7, wherein the silane coupling agent is added in an amount of 0.01 to 10 parts by mass per 100 parts by mass of the inorganic filler. A heat-resistant silicone sheet obtained by forming the heat-resistant silicone composition according to any one of claims 1 to 8 into a sheet by at least one molding method selected from the group consisting of sheet molding and press molding, and then curing the composition. A method for producing the heat-resistant silicone sheet described in claim 9, comprising mixing the silicone composition described in any one of claims 1 to 8, molding the mixture using at least one molding method selected from sheet molding and press molding, and curing the mixture.