Silicone resin composition

Abstract

This silicone resin composition contains a silicone resin, a hexagonal boron nitride filler, and a thermally conductive filler other than the hexagonal boron nitride filler. The hexagonal boron nitride filler has a volume-based median pore diameter, as measured by mercury intrusion porosimetry, of 0.5-4.0 μm. The thermally conductive filler has a D50 value of 0.01-0.8 μm. The packing ratio of the hexagonal boron nitride filler is 30 vol.% or more. The overall packing ratio of the hexagonal boron nitride filler and the thermally conductive filler is 50 vol.% or more.

Description

Silicone resin composition

[0001] The present invention relates to a silicone resin composition.

[0002] In recent years, with the increase in power density of semiconductor devices, materials used in such devices are required to have more advanced heat dissipation properties. One such material is a series of materials called thermal interface materials, the use of which is rapidly expanding. Thermal interface materials are materials used to reduce the thermal resistance of the path through which heat generated by semiconductor elements is released to a heat sink or housing, etc. Thermal interface materials include those used in a hardened or semi-hardened, non-fluid state, such as heat dissipation sheets, and those used in a fluid paste or liquid state, such as greases and gap fillers (see, for example, Patent Documents 1 to 3).

[0003] Generally, thermal interface materials are resin compositions in which thermally conductive fillers are dispersed. Silicone resins are widely used as the resins used in these resin compositions. Hexagonal boron nitride powder is known as one type of thermally conductive filler, and it has characteristics such as high thermal conductivity, low dielectric constant, and small specific gravity.

[0004] Patent Document 1 discloses a heat dissipation sheet containing a silicone resin and a thermally conductive filler. In the examples, the document specifically discloses a heat dissipation sheet containing a silicone resin and hexagonal boron nitride, with a filling rate of 65 to 85 mass % of the hexagonal boron nitride.

[0005] Patent Document 2 discloses a non-hardening grease containing a silicone resin (silicone oil) and a thermally conductive filler (thermally conductive particles). In the examples, specifically, a silicone grease having a filling rate of 27 mass % of boron nitride is disclosed.

[0006] Patent Document 3 discloses a gap filler containing a curable silicone resin (a diorganopolysiloxane having an alkenyl group bonded to a silicon atom and a diorganopolysiloxane having a hydrogen atom bonded to a silicon atom) and a thermally conductive filler. While boron nitride is exemplified as the thermally conductive filler, no examples using boron nitride are disclosed.

[0007] International Publication No. 2023 / 090240 International Publication No. 2022 / 158029 Japanese Patent Application Laid-Open No. 2023-168633

[0008] When manufacturing electronic components using a fluid paste or liquid thermal interface material (TIM), the TIM is typically dispensed from a syringe and applied to at least one of a heat-generating component and a cooling component, and then the other component is pressed against the applied surface to thinly crush the TIM. The thinner the film thickness, the lower the thermal resistance and the more effective the heat dissipation performance of the TIM. Therefore, resin compositions used in such applications are required to be easily crushable into a thin film.

[0009] Here, because hexagonal boron nitride has flat primary particles and few functional groups on the particle surface, incorporating a large amount of hexagonal boron nitride into a silicone resin tends to significantly increase the viscosity of the resin composition. In producing a heat-dissipating sheet such as that described in Patent Document 1, the silicone resin composition is diluted with a solvent, applied, and then the solvent is evaporated to form a sheet, so the silicone resin composition can be used even if it has a high viscosity. However, in the case of a paste or liquid TIM, if the resin composition has a high viscosity and poor syringe ejection properties, handling is impaired and it becomes difficult to easily crush it into a thin film, making it difficult to manufacture electronic components.

[0010] In recent years, the use of millimeter-wave electromagnetic waves, such as 5G and 6G, which enable high-speed, large-capacity communications, has been expanding. For circuit boards used in such applications, there is concern that high-dielectric-constant thermal interface materials may generate high-frequency noise. Therefore, it is believed that using a silicone resin composition containing hexagonal boron nitride, which has a low dielectric constant, as a filler would be effective.

[0011] However, as mentioned above, hexagonal boron nitride has low affinity with silicone resins due to the flat primary particles and the small number of functional groups on the particle surface, and if the amount of hexagonal boron nitride is increased to increase the thermal conductivity of the silicone resin composition, the fluidity of the silicone resin composition decreases, the syringe dischargeability decreases, handling becomes poor, and it becomes difficult to easily crush it thinly. In fact, in Patent Document 2, the example shows that the proportion of boron nitride is 27% by mass (about 25% by volume), which is said to have a viscosity that is excellent in workability, but in Comparative Example 2, where the proportion is 32% by mass (about 30% by volume), the viscosity becomes so significantly high that it is impossible to measure, and it is expected that the syringe dischargeability will also be poor.

[0012] The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a silicone resin composition that contains a silicone resin and a hexagonal boron nitride filler and that has high thermal conductivity and syringe dischargeability.

[0013] In order to solve the above problems, the present inventors have conducted extensive research and have found that by combining a specific hexagonal boron nitride filler with a thermally conductive filler other than the hexagonal boron nitride filler and having a specific particle size in a specific ratio, it is possible to improve the thermal conductivity and achieve high dischargeability compared to when the hexagonal boron nitride filler is used alone, which led to the completion of the present invention.

[0014] That is, the silicone resin composition of the present invention comprises a silicone resin, a hexagonal boron nitride filler, and a thermally conductive filler, wherein the hexagonal boron nitride filler has a volume-based median pore diameter of 0.5 to 4.0 μm as measured by mercury intrusion porosimetry, the thermally conductive filler has a D50 of 0.01 to 0.8 μm, the filling rate of the hexagonal boron nitride filler is 30% by volume or more, and the total filling rate of the hexagonal boron nitride filler and the thermally conductive filler is 50% by volume or more.

[0015] The D90 of the hexagonal boron nitride filler is preferably 250 μm or less. The volume ratio of the hexagonal boron nitride filler to the thermally conductive filler is preferably 2:1 to 10:1. The thermally conductive filler is preferably a silica filler. One aspect of the present invention is a cured product of the silicone resin composition. Another aspect of the present invention is the silicone resin composition filled in a syringe.

[0016] Furthermore, one embodiment of the present invention is an electronic component comprising a heat-generating member, a cooling member, and the silicone resin composition or a cured product thereof arranged so as to be in contact with the heat-generating member and the cooling member.

[0017] Furthermore, one embodiment of the present invention is a method for manufacturing an electronic component having a heat-generating member and a cooling member, which includes a step of discharging the silicone resin composition filled in the syringe from the syringe to apply it to at least one of the heat-generating member and the cooling member, and then pressing the heat-generating member and the cooling member together with the silicone resin composition interposed therebetween.

[0018] According to the present invention, a silicone resin composition having high thermal conductivity and excellent dischargeability due to a high loading of hexagonal boron nitride filler can be obtained. By using the silicone resin composition as a thermal interface material, it is possible to efficiently manufacture electronic components that require, for example, a low dielectric constant and high thermal conductivity.

[0019] The silicone resin composition of the present invention (hereinafter also referred to as "the composition") contains a silicone resin, a hexagonal boron nitride filler, and a thermally conductive filler. Each component will be described below.

[0020] <Silicone Resin> The silicone resin is not particularly limited, and known silicone resins can be used without any particular limitations. Examples of silicone resins include polyorganosiloxanes. Examples of the polyorganosiloxanes include polyorganosiloxanes having alkenyl groups, polyorganosiloxanes having hydrosilyl groups, and dialkylpolyorganosiloxanes. A plurality of types of polyorganosiloxanes may be used in combination.

[0021] The polyorganosiloxane having an alkenyl group may be, for example, a polyorganosiloxane having an average composition formula R ｘ ｅ R ｙ ｆ SiO ［４－（ｅ＋ｆ）］／２ The polyorganosiloxane may be used alone or in combination of two or more.

[0022] R ｘ is an alkenyl group. The alkenyl group is preferably a group having 2 to 8 carbon atoms, and examples thereof include a vinyl group, an allyl group, a 1-butenyl group, and a 1-hexenyl group, with a vinyl group being preferred. The number of alkenyl groups in one molecule of the polyorganosiloxane is preferably one or more, more preferably two or more. The alkenyl group may be bonded to a silicon atom at the molecular chain terminal, to a silicon atom in the middle of the molecular chain, or to both. From the viewpoints of the curing speed when curing the composition as described below and the physical properties of the resulting cured body, it is preferable that the alkenyl group be bonded to at least a silicon atom at the molecular chain terminal, particularly to silicon atoms at both molecular chain terminals.

[0023] R ｙ R is a substituted or unsubstituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond. ｙ The number of carbon atoms in R is preferably 1 to 12, more preferably 1 to 10. ｙExamples of the alkyl group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, hexyl, octyl, decyl, and dodecyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cyclobutyl; 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 have been substituted with halogen atoms such as chlorine, fluorine, and bromine, or with cyano groups or the like. Examples of the groups substituted with halogen atoms or cyano groups or the like include halogenated hydrocarbon groups such as chloromethyl, trifluoropropyl, chlorophenyl, bromophenyl, dibromophenyl, tetrachlorophenyl, fluorophenyl, and difluorophenyl groups, and cyanoalkyl groups such as α-cyanoethyl, β-cyanopropyl, and γ-cyanopropyl groups. Among these, R ｙ is preferably an alkyl group or an aryl group, more preferably a methyl group or a phenyl group.

[0024] e and f are positive numbers satisfying 0 < e < 3, 0 < f < 3, and 1 < e + f < 3, and may be appropriately adjusted so that the viscosity of the polyorganosiloxane is 0.01 to 10 Pa s, for example. e and f are preferably numbers satisfying 0.0005 ≦ e ≦ 1, 1.5 ≦ f < 2.4, and 1.5 < e + f < 2.5, and more preferably numbers satisfying 0.001 ≦ e ≦ 0.5, 1.8 ≦ f ≦ 2.1, and 1.8 < e + f ≦ 2.2.

[0025] The molecular structure of the polyorganosiloxane may be linear, branched, cyclic, or three-dimensional network, and the polyorganosiloxane may be a mixture thereof. The viscosity of the polyorganosiloxane at 23 ° C. is preferably 0.01 to 10 Pa s, from the viewpoint of being able to obtain a composition having the desired physical properties with good workability.

[0026] The polyorganosiloxane having a hydrosilyl group may be, for example, a polyorganosiloxane having an average composition formula R ｚ ｇ Hｈ SiO ［４－（ｇ＋ｈ）］／２ The polyorganosiloxane may be used alone or in combination of two or more.

[0027] R ｚ R is a substituted or unsubstituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond. ｚ Examples of R include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, hexyl, cyclohexyl, and octyl; aryl groups such as phenyl and tolyl; aralkyl groups such as benzyl and phenylethyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine, chlorine, and bromine, or with cyano groups. Examples of groups substituted with halogen atoms or cyano groups include chloromethyl, bromoethyl, trifluoropropyl, and cyanoethyl. ｚ Among these, from the viewpoints of ease of synthesis, cost, etc., is preferably an alkyl group, more preferably a methyl group.

[0028] g and h are numbers that satisfy 0.5≦g≦2, 0<h≦2, and 0.5<g+h≦3. For example, they may be appropriately adjusted so that the viscosity of the polyorganosiloxane is 0.01 to 10 Pa s. g and h are preferably numbers that satisfy 0.6≦g≦1.9, 0.01≦h≦1.0, and 0.6<g+h≦2.8.

[0029] The dialkyl polyorganosiloxane may be, for example, a dialkyl polyorganosiloxane represented by the average composition formula R ａ R ｂ Examples of the polyorganosiloxane include polyorganosiloxanes represented by SiO. One type of polyorganosiloxane may be used, or two or more types may be used.

[0030] R ａ and R ｂ are each independently a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bonds, and preferably have 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms. ａ and R ｂis, for example, the R ｙ or R ｚ The functional groups can be any of those exemplified above.

[0031] The dialkylpolyorganosiloxane may, for example, be a linear dimethylpolysiloxane represented by the following formula (1).

[0032]

[0033] (In formula (1), i is an integer such that the viscosity of the compound represented by formula (1) at 23°C is 0.01 to 10 Pa·s. The viscosity is preferably 0.02 Pa·s or more and preferably 5 Pa·s or less.) The dimethylpolysiloxane also includes a compound in which one or more methyl groups in formula (1) are substituted with a monovalent hydrocarbon group other than a methyl group. However, the substituted compound must contain at least one -(Si(CH ３ ) ２ The substituent has the structure of R ｙ or R ｚ Examples of the functional groups include those exemplified in

[0034] By making the polyorganosiloxane having alkenyl group and the polyorganosiloxane having hydrosilyl group coexist in the presence of the hydrosilylation catalyst described below, it is possible to harden the silicone resin composition, and it can be placed at a desired location before hardening, and then hardened after being deformed into a desired shape, thereby effectively exerting its properties.In this case, this composition may previously contain both the polyorganosiloxane having alkenyl group and the polyorganosiloxane having hydrosilyl group.

[0035] When the present composition contains both the polyorganosiloxane having the alkenyl group and the polyorganosiloxane having the hydrosilyl group, the content thereof is, from the viewpoint that physical properties suitable for a heat dissipation material after curing are easily obtained, 0.1 to 2.0 hydrogen atoms bonded to silicon atoms of the polyorganosiloxane having the hydrosilyl group are preferably contained per alkenyl group bonded to silicon atoms of the polyorganosiloxane having the alkenyl group, particularly 0.2 to 1.5 hydrogen atoms.

[0036] The viscosity of the silicone resin can be measured, for example, by a rotational viscometer such as a rheometer.

[0037] <Hydrosilylation Catalyst> When the present composition contains both the polyorganosiloxane having an alkenyl group and the polyorganosiloxane having a hydrosilyl group, the present composition may contain a hydrosilylation catalyst used in the curing reaction.

[0038] The hydrosilylation catalyst may be any known catalyst without particular limitation, and examples thereof include platinum group metals such as platinum, rhodium, ruthenium, and palladium, as well as compounds thereof (compounds containing platinum group metals; hereinafter, also referred to as "platinum group metal compounds").

[0039] Examples of platinum group metal compounds include platinum dichloride, platinum dibromide, platinum tetrachloride, chloroplatinic acid, alcohol-modified chloroplatinic acid, Karsted's catalyst (a complex of platinum and vinylsiloxane), sodium chloroplatinate, potassium chloroplatinate, bisacetylacetonatoplatinum, tetrakis(triphenylphosphine)palladium, and chlorotris(triphenylphosphine)rhodium. These may be used alone or in combination of two or more.

[0040] The content of the hydrosilylation catalyst may be any amount necessary for curing, and may be adjusted appropriately depending on the desired curing rate, etc., but the amount of platinum element (platinum group metal) added is, for example, 0.0001 parts by mass or more, preferably 0.001 parts by mass or more, and for example, 1 part by mass or less, preferably 0.1 parts by mass or less, per 100 parts by mass of the total of the polyorganosiloxane having an alkenyl group and the polyorganosiloxane having a hydrosilyl group.

[0041] <Reaction Inhibitor> When the composition contains the hydrosilylation catalyst, the composition may contain a reaction inhibitor to inhibit the curing reaction. This inhibits the curing reaction before use of the composition, thereby improving storage stability. Furthermore, it inhibits a rapid curing reaction during use, thereby improving placement workability.

[0042] Examples of reaction inhibitors include acetylene alcohol, benzotriazole, triphenylphosphine, and diallyl maleate, with acetylene alcohol being preferred. Examples of acetylene alcohols include 1-ethynyl-1-cyclohexanol, 2-methyl-3-butyn-2-ol, bis[(1,1-dimethyl-2-propyn-1-yl)oxy]dimethylsilane, and tris[(1,1-dimethyl-2-propyn-1-yl)oxy]methylsilane. These may be used alone or in combination of two or more.

[0043] The content of the reaction inhibitor in the present composition is, for example, 0.05 parts by mass or more, preferably 0.1 parts by mass or more, and for example, 10 parts by mass or less, preferably 1 part by mass or less, relative to 100 parts by mass of the total of the polyorganosiloxane having an alkenyl group and the polyorganosiloxane having a hydrosilyl group.

[0044] <Hexagonal Boron Nitride Filler> The silicone resin composition of the present invention contains a hexagonal boron nitride filler having a pore volume-based median diameter (hereinafter sometimes simply referred to as "pore diameter") of 0.5 to 4.0 μm as measured by mercury intrusion porosimetry. This allows the composition to achieve both high dischargeability and high thermal conductivity. The reason for this is not clear, but the inventors believe it to be as follows.

[0045] As mentioned above, hexagonal boron nitride has a low affinity with silicone resins due to the flat primary particles and the small number of functional groups on the particle surface. Therefore, increasing the amount of hexagonal boron nitride filler to increase the thermal conductivity of the silicone resin composition reduces the fluidity of the silicone resin composition and the syringe ejection properties. By setting the pore size of the hexagonal boron nitride filler to the above-mentioned lower limit or more and using the hexagonal boron nitride filler in combination with a thermally conductive filler described below, the small particle size thermally conductive filler can penetrate into the voids of the hexagonal boron nitride filler, thereby reducing the amount of silicone resin that penetrates into the voids of the hexagonal boron nitride filler. As a result, the contact area between the silicone resin and the hexagonal boron nitride filler is reduced, reducing the adverse effect of the poor affinity between the hexagonal boron nitride filler and the silicone resin on the physical properties of the silicone resin composition, and thus preventing a decrease in the ejection properties of the silicone resin composition. As a result, it is possible to increase the total content of the hexagonal boron nitride filler, which contributes to thermal conductivity, and the thermally conductive filler while maintaining good ejection properties, and it is thought that this will enable both high syringe ejection properties and high thermal conductivity to be achieved. On the other hand, if the pore size of the hexagonal boron nitride filler exceeds the above upper limit, the secondary structure of the hexagonal boron nitride will be more likely to collapse, and even if the thermally conductive filler enters the voids, the formation of heat conduction paths will be limited, and the effect of improving thermal conductivity will be reduced.

[0046] The pore size of the hexagonal boron nitride filler is preferably 1.0 μm or more and preferably 3.0 μm or less.

[0047] The D50 of the hexagonal boron nitride filler is preferably 20 μm or more, more preferably 40 μm or more. This makes it easy to increase the thermal conductivity of the composition. The upper limit of the D50 of the hexagonal boron nitride filler is not particularly limited as long as it is smaller than the D90 of the hexagonal boron nitride filler described below, but is, for example, 80 μm or less.

[0048] The D10 of the hexagonal boron nitride filler is preferably 1 μm or more, more preferably 5 μm or more. This makes it easy to reduce the viscosity of the composition. The upper limit of the D10 of the hexagonal boron nitride filler is not particularly limited as long as it is smaller than the D50 of the hexagonal boron nitride filler, but it is, for example, 20 μm or less.

[0049] The D90 of the hexagonal boron nitride filler is preferably 250 μm or less, more preferably 150 μm or less, and even more preferably 135 μm or less. This makes it easy to crush the composition into a thin film. There is no particular lower limit for the D90 of the hexagonal boron nitride filler, as long as it is greater than the D50 of the hexagonal boron nitride filler, but it is, for example, 80 μm or more.

[0050] In the present invention, D10, D50 and D90 are particle sizes at cumulative 10%, cumulative 50% and cumulative 90%, respectively, in the volume-based particle size distribution measured by a laser diffraction scattering method.

[0051] The specific surface area of ​​the hexagonal boron nitride filler is not particularly limited, but is preferably 1.0 to 10 m ２ The specific surface area is more preferably 2.0 m ２ / g or more, more preferably 4.0m ２ / g or more, more preferably 9.0m ２ / g or less, more preferably 8.0m ２ / g or less. When the specific surface area is within the above range, it becomes easy to improve the thermal conductivity of the composition, and the dispersibility of the hexagonal boron nitride filler in the silicone resin becomes good, making it easy to reduce the viscosity of the composition and improve its operability. The specific surface area can be measured by the BET single-point method using nitrogen gas adsorption.

[0052] The hexagonal boron nitride filler may be composed of independent single particles or agglomerated particles formed by the aggregation of several small primary particles. It may also be composed of a mixture of single particles and agglomerated particles. Primary particles of hexagonal boron nitride are plate-shaped (flat) and have high in-plane thermal conductivity but relatively low thermal conductivity in the thickness direction. Therefore, it is preferable to contain agglomerated particles to reduce the orientation of thermal conductivity when formed into a thin film such as a sheet, thereby facilitating the formation of a thermal conduction path in the thickness direction. Furthermore, when agglomerated particles are contained, voids are formed stably, making it easier to control the pore size, and thus facilitating the production of the composition.

[0053] As the hexagonal boron nitride filler, any known filler can be used without particular limitation as long as the pore diameter is 0.5 to 4.0 μm. The method for producing the hexagonal boron nitride filler is also not particularly limited, and hexagonal boron nitride fillers produced by known methods can be used. Methods for producing hexagonal boron nitride include, for example, the melamine method, in which a mixed powder of boron oxide and a nitrogen-containing organic compound is heated and synthesized; the direct nitridation method, in which boron carbide is heated and synthesized in a nitrogen atmosphere; the reduction nitridation method, in which a mixed powder of an oxygen-containing boron compound, carbon, and an oxygen-containing calcium compound is heated and synthesized in a nitrogen atmosphere; and the gas phase synthesis method. Examples of the melamine method include the method disclosed in JP 2022-185586 A, and examples of the reduction nitridation method include the methods disclosed in JP 2022-185585 A or JP 2022-133951 A. It is also possible to use hexagonal boron nitride powder obtained by a known manufacturing method or commercially available hexagonal boron nitride powder by adjusting the particle size distribution using a sieve or classifier.

[0054] <Thermally Conductive Filler> The silicone resin composition of the present invention contains a thermally conductive filler having a D50 of 0.01 to 0.8 μm.

[0055] As the thermally conductive filler, any filler other than hexagonal boron nitride filler having high thermal conductivity can be used without particular limitation, and for example, metal oxides can be used. Examples of metal oxides include silica, alumina, titania, zirconia, and composite oxides thereof, and can be selected depending on the purpose. For example, from the viewpoint of utilizing the characteristic of hexagonal boron nitride filler, i.e., low dielectric constant, to obtain the present composition for use in circuit boards, which are high-frequency applications, it is particularly preferable to use silica, which has a low dielectric constant. For example, from the viewpoint of utilizing the characteristic of hexagonal boron nitride filler, i.e., low specific gravity compared to other thermally conductive fillers, to obtain the present composition having a low specific gravity, it is particularly preferable to use silica, which has a low specific gravity. For example, from the viewpoint of obtaining the present composition having high thermal conductivity, it is particularly preferable to use alumina, which has excellent thermal conductivity.

[0056] The D50 of the thermally conductive filler is preferably 0.05 μm or more, more preferably 0.1 μm or more, and preferably 0.5 μm or less, more preferably 0.4 μm or less. The ratio S / P of the D50 (S) of the thermally conductive filler to the pore size (P) of the hexagonal boron nitride filler is preferably 0.01 to 0.5. The ratio S / P is more preferably 0.02 or more, and more preferably 0.4 or less. By setting the ratio S / P within the above range, the thermally conductive filler can easily penetrate into the voids of the hexagonal boron nitride filler.

[0057] The specific surface area of ​​the thermally conductive filler is not particularly limited, but is, for example, 1 to 100 m ２ The specific surface area is preferably 5 m ２ / g or more, preferably 60m ２ The shape of the thermally conductive filler is not particularly limited, but may be spherical from the viewpoint of increasing the fluidity of the present composition.

[0058] The manufacturing method of the thermally conductive filler is not particularly limited, and those manufactured by known methods can be used. Preferred examples of spherical silica fillers include dry-process and wet-process synthetic silica, and fused silica. Commercially available products include Silfil NSS-3N, Sunseal SS-01, and Sunseal SS-04 (manufactured by Tokuyama Corporation), SO-C1 and SO-C2 (manufactured by Admatechs Corporation), and SFP-20M and UFP-30 (manufactured by Denka Co., Ltd.).

[0059] The thermally conductive filler may be a filler that has been surface-treated with a surface treatment agent. Examples of the surface treatment agent include known treatment agents such as silane compounds, aluminate coupling agents, and titanate coupling agents, and are not particularly limited. Known methods can be used for the surface treatment without any particular limitation.

[0060] <Other Components> The present composition may contain other components in addition to the silicone resin, hydrosilylation catalyst, reaction inhibitor, hexagonal boron nitride filler, and thermally conductive filler, as long as the effects of the present invention are not impaired. Examples of such other components include a curing accelerator, an affinity agent, a discoloration inhibitor, a surfactant, a dispersant, a colorant, a plasticizer, a viscosity modifier, and an antibacterial agent.

[0061] Examples of the compatibility agent include silane coupling agents, aluminate coupling agents, titanate coupling agents, and zirconate coupling agents. Among these, silane coupling agents are preferred from the viewpoint of compatibility with silicone resins, and alkyl silane coupling agents or polysiloxanes having an alkoxysilyl group at one end are particularly preferred.

[0062] Examples of alkyl-based silane coupling agents include hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, and dodecyltriethoxysilane.

[0063] The polysiloxane having an alkoxysilyl group at one end is preferably a compound represented by the following formula (2).

[0064]

[0065] In the above formula, R １ is, for example, a hydrocarbon group, preferably a hydrocarbon group having 1 to 10 carbon atoms. These hydrocarbon groups may be substituted with a halogen atom or the like. Specific examples of the hydrocarbon group include R ｚ Examples of the hydrocarbon group include the same groups as those exemplified in the group 1. The hydrocarbon group is preferably an alkyl group, more preferably a methyl group or an ethyl group. １ may be the same or different from each other.

[0066] R ２ is, for example, a hydrocarbon group, preferably a hydrocarbon group having 1 to 20 carbon atoms. These hydrocarbon groups may be substituted with a halogen atom or the like. Specific examples of the hydrocarbon group include R ｚ Examples of the hydrocarbon group include the same groups as those exemplified in 1. The hydrocarbon group is preferably an alkyl group, more preferably an n-butyl group or a methyl group.

[0067] R ３ is an alkoxysilyl group, and examples of the alkoxysilyl group include trialkoxysilyl groups such as trimethoxysilyl group, triethoxysilyl group, triisopropoxysilyl group, and triphenoxysilyl group; dimethoxysilyl groups such as dimethoxymethylsilyl group and diethoxymethylsilyl group; and monoalkoxysilyl groups such as methoxydimethylsilyl group and ethoxydimethylsilyl group. The alkoxysilyl group is preferably a trialkoxysilyl group, and more preferably a trimethoxysilyl group or a triethoxysilyl group.

[0068] For example, k is an integer of 0 or more and 100 or less. k is preferably 10 or more and preferably 50 or less.

[0069] For example, j is an integer of 0 or more and 10 or less. j is preferably 1 or more and 8 or less, and more preferably 5 or less.

[0070] When the present composition contains a compatibility agent, the content of the compatibility agent in the present composition is, for example, 0.1 vol.% or more, preferably 0.3 vol.% or more, and for example, 25 vol.% or less, preferably 20 vol.% or less, relative to the total amount of the present composition.

[0071] <Silicone Resin Composition> The silicone resin composition of the present invention contains a silicone resin, a hexagonal boron nitride filler, and a thermally conductive filler (a thermally conductive filler other than hexagonal boron nitride filler). The filling rate of the hexagonal boron nitride filler is 30% by volume or more, and the total filling rate of the hexagonal boron nitride filler and the thermally conductive filler (hereinafter sometimes simply referred to as "filler filling rate") is 50% by volume or more. This allows the thermal conductivity of the composition to be increased. The filling rate of the hexagonal boron nitride filler in the present invention refers to the content ratio of the hexagonal boron nitride filler relative to the total amount of the composition. Furthermore, the total filling rate of the hexagonal boron nitride filler and the thermally conductive filler refers to the total content ratio of the hexagonal boron nitride filler and the thermally conductive filler relative to the total amount of the composition.

[0072] The filling rate of the hexagonal boron nitride filler is preferably 35% by volume or more, and although there is no particular upper limit, it is preferably 50% by volume or less, more preferably 45% by volume or less, in order to facilitate good dischargeability.

[0073] The filler filling rate is preferably 52% by volume or more, more preferably 54% by volume or more. A higher filler filling rate is preferable because it can increase the thermal conductivity of the composition, but in terms of a balance with dischargeability, the filler filling rate is preferably 65% ​​by volume or less, more preferably 60% by volume or less.

[0074] The volume ratio of the hexagonal boron nitride filler to the thermally conductive filler (hexagonal boron nitride filler:thermally conductive filler) is preferably 2:1 to 10:1, more preferably 2:1 to 5:1, and even more preferably 2:1 to 4:1, which makes it easy to balance the thermal conductivity and dischargeability of the composition.

[0075] In the silicone resin composition of the present invention, in order to take advantage of the low dielectric constant characteristics of the hexagonal boron nitride filler, it is preferable to reduce the content of additives that increase the dielectric constant. For example, since surfactants increase the dielectric constant, their content is preferably 4% by mass or less, more preferably 1% by mass or less, based on the total composition. It is even more preferable that the composition does not contain any surfactants. In particular, anionic surfactants having an anionic functional group and cationic surfactants having a cationic functional group tend to increase the dielectric constant due to their functional groups, so their content is preferably 4% by mass or less, more preferably 1% by mass or less, based on the total composition. It is even more preferable that the composition does not contain any anionic surfactants or cationic surfactants.

[0076] When the silicone resin composition of the present invention is filled into a discharge container having an inner diameter of a tip discharge portion of 2 mm and discharged at a discharge pressure of 0.62 MPa, the discharge rate is preferably 10 g / min or more. This provides high dischargeability and good handleability, and also enables easy thin and uniform crushing during the production of electronic components, thereby improving the production efficiency of electronic components. The discharge rate is more preferably 20.0 g / min or more. If the discharge rate is too high, it may be difficult to control the discharge rate during production, so the discharge rate is preferably 500 g / min or less, more preferably 400 g / min or less. The discharge rate is measured by filling the composition into a syringe having an inner diameter of a tip discharge portion of 2 mm and discharging it at 25°C at a discharge pressure of 0.62 MPa.

[0077] The thickness of the silicone resin composition of the present invention (hereinafter sometimes referred to as "BLT") measured after sandwiching 0.02 mL between two 10 mm x 10 mm silicon chips and applying a force of 50 N for 60 seconds is preferably 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less. This allows the composition to be easily formed into a thin film (thinning is possible), thereby reducing thermal resistance. Therefore, when used as a heat dissipation component, it imparts high heat dissipation performance and enables efficient cooling of heat-generating parts of electronic components. Although there is no particular lower limit for the BLT, attempts to thin the silicone resin composition may limit the fillers that can be used, making it difficult to achieve both high thermal conductivity and high dischargeability. Therefore, the BLT is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more.

[0078] The thermal conductivity of the silicone resin composition of the present invention or its cured product, measured by the hot disk method, is preferably 3.0 W / m K or more, more preferably 3.5 W / m K or more. This provides high heat dissipation performance when used as a heat dissipation component, making it possible to efficiently cool heat-generating parts of electronic components. There is no particular upper limit to the thermal conductivity of this composition or its cured product, and the higher the better, but it may be, for example, 10.0 W / m K or less.

[0079] The Type E hardness of the cured product of the silicone resin composition of the present invention is preferably 20 or more and 90 or less. The Type E hardness of the cured product is more preferably 30 or more and more preferably 80 or less. When the hardness is within the above range, the flexibility of the cured product becomes appropriate, the ability to conform to the heat-generating parts of electronic components increases, and heat dissipation performance can be more efficiently exhibited.

[0080] The dielectric constant of the cured product of the silicone resin composition of the present invention, measured at 10 GHz, is preferably 4.5 or less, more preferably 4.0 or less. This makes it easier to suppress the generation of high-frequency noise. There is no particular lower limit for the dielectric constant, and the lower the better, but it may be, for example, 3.0 or more.

[0081] The dielectric breakdown strength of the cured product of the silicone resin composition of the present invention is preferably 20 kV / mm or more, more preferably 25 kV / mm or more. This makes it easier to prevent dielectric breakdown even when electronic components are used at high voltages. There is no particular upper limit to the dielectric breakdown strength of the cured product, and the higher the better, but it may be, for example, 50 kV / mm or less.

[0082] <Method for Producing Silicone Resin Composition> The silicone resin composition of the present invention can be produced by mixing a silicone resin, a hexagonal boron nitride filler, the thermally conductive filler, and, if necessary, the other components. The mixing method is not limited and can be carried out using a general mixer. Examples of such mixers include kneaders such as planetary mixers and trimixes, roll mixers such as three-roll mixers, crushers, and planetary mixers. Mixing may also be carried out using a mortar or the like.

[0083] <Form of Silicone Resin Composition> The silicone resin composition of the present invention is, for example, in the form of a paste or liquid having fluidity. The composition may be of a one-component type or a two-component type.

[0084] When the present composition is a one-component type and contains the polyorganosiloxane having alkenyl groups, the polyorganosiloxane having hydrosilyl groups, and the hydrosilylation catalyst, the curing reaction may proceed too quickly. In this case, the reaction inhibitor may be added to delay the curing reaction at storage temperatures or working temperatures to improve storage stability and workability, while the curing reaction may be allowed to proceed by heating at the desired timing.

[0085] When the composition is a two-component type, the first and second components are stored separately and mixed immediately before use. In this case, even if the first and second components alone do not meet the requirements of the composition, if the mixture meets the requirements of the composition after mixing, the mixture can be considered the composition. The content of each component in the silicone resin composition (mixture) after mixing the first and second components can be calculated from the respective compositions of the first and second components and the amounts of the first and second components mixed. The physical properties of the hexagonal boron nitride filler and the thermally conductive filler after mixing the first and second components, such as D10, D50, D90, and pore size, can be calculated from the physical properties of the first and second components and the amounts of the first and second components mixed.

[0086] The physical properties of this composition can be evaluated after mixing the silicone resin, hexagonal boron nitride filler, and the thermally conductive filler. In the case of a two-component composition, the physical properties of the silicone resin composition (mixture) are evaluated after mixing the first and second components. However, since it may be difficult to evaluate the discharge amount after mixing, the discharge amounts of the first and second components are evaluated separately. If both the discharge amounts of the first and second components are within the above-mentioned ranges for this composition, it can be said that the discharge amount of the mixture of the first and second components is also within the above-mentioned ranges.

[0087] Furthermore, if the first agent or the second agent alone satisfies the requirements of the present composition, each agent that satisfies the requirements can also be said to be the present composition.

[0088] When the present composition contains the alkenyl-containing polyorganosiloxane, the hydrosilyl-containing polyorganosiloxane, and the hydrosilylation catalyst as silicone resins, to form a two-component composition, it is preferable that the alkenyl-containing polyorganosiloxane, the hydrosilyl-containing polyorganosiloxane, and the hydrosilylation catalyst do not coexist before mixing. Therefore, for example, the first and second agents are configured as a first agent containing the alkenyl-containing polyorganosiloxane but not containing the hydrosilyl-containing polyorganosiloxane, and a second agent containing the hydrosilyl-containing polyorganosiloxane but not containing the alkenyl-containing polyorganosiloxane. In this case, the hydrosilylation catalyst may be blended into either the first agent or the second agent, or both. Alternatively, the first agent and the second agent may be a first agent containing a polyorganosiloxane having an alkenyl group and a hydrosilylation catalyst but not containing a polyorganosiloxane having a hydrosilyl group, and a second agent containing a polyorganosiloxane having an alkenyl group and a polyorganosiloxane having a hydrosilyl group but not containing a hydrosilylation catalyst.

[0089] The composition is preferably filled in a container such as a syringe, tube, or cup. For example, filling the composition in a syringe facilitates the application of the composition to a heat-generating or cooling portion during the manufacture of electronic components. While the syringe into which the composition is filled is not particularly limited, from the viewpoint of ease of application, a syringe with an inner diameter of the tip discharge portion of 0.1 to 5.0 mm, particularly 1.0 to 3.0 mm, is preferred. A separate nozzle may be attached to the tip of the syringe. When the composition is a two-component type, two syringes may be filled with the first and second components, respectively, and these may be arranged in a twin series and extruded simultaneously. In this case, a nozzle capable of mixing pastes may be attached to the tip of the syringe, and the two components may be mixed while the first and second components are extruded.

[0090] <Uses of Silicone Resin Composition> The uses of the silicone resin composition of the present invention are not particularly limited, but suitable uses include paste or liquid thermal interface materials, particularly thermal greases and gap fillers used in the manufacture of electronic components. Using this composition as a thermal interface material can produce electronic components comprising a heat-generating component, a cooling component, and the composition or a cured product thereof arranged in contact with the heat-generating component and the cooling component. The electronic components can be manufactured, for example, by a manufacturing method including the steps of discharging the composition from a syringe and applying it to at least one of the heat-generating component and the cooling component, and then pressing the heat-generating component and the cooling component together via the composition. In these applications, the composition can be easily discharged from a syringe and easily crushed into a thin film, allowing for efficient manufacture of electronic components. Furthermore, the high thermal conductivity of the composition or a cured product thereof facilitates efficient cooling of the heat-generating components of electronic components.

[0091] When a silicone resin composition is used by curing, such as in a gap filler, the silicone resin composition typically contains a polyorganosiloxane having an alkenyl group, a polyorganosiloxane having a hydrosilyl group, and a hydrosilylation catalyst. To prevent hardening during storage, the composition may be stored in two separate liquids, as described above, or may be stored as a single liquid at low or room temperature and heated to harden before use. This allows for the production of electronic components comprising a heat-generating component, a cooling component, and a cured product of the composition arranged in contact with the heat-generating component and the cooling component. Such electronic components can be manufactured by discharging the composition from a syringe and applying it to at least one of the heat-generating component and the cooling component, then pressing the heat-generating component and the cooling component together via the composition, followed by curing the composition by heating or other means.

[0092] EXAMPLES The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0093] [Measurement Methods] Various physical properties in the examples and comparative examples were measured by the following methods.

[0094] (1) D10, D50, and D90 20 g of ethanol was added to a 50 mL screw cap vial as a dispersion medium, and 1 g of hexagonal boron nitride powder was dispersed in the ethanol to prepare a measurement sample. The particle size distribution of this sample was measured on a volume basis using a laser diffraction / scattering particle size distribution analyzer (MT3000, manufactured by Nikkiso Co., Ltd.). The D10, D50, and D90 were determined from the obtained particle size distribution.

[0095] (2) Pore diameter The pore diameter of the hexagonal boron nitride filler was measured by mercury intrusion porosimetry using an Autopore IV9520 manufactured by Micromeritics Corp. The volume-based median diameter was calculated from the cumulative pore distribution obtained by determining the pore distribution from 0.0036 μm to 200 μm, with pore diameter on the horizontal axis and cumulative pore volume on the vertical axis.

[0096] (3) Syringe Discharge Amount The silicone resin composition was filled into a syringe "PSY-30F" manufactured by Musashi Engineering Co., Ltd. (the inner diameter of the syringe body for storing the sample was 22 mm, and the inner diameter of the tip portion for discharging the sample was 2 mm), and then the syringe was left to stand for 6 hours in a thermostatic chamber at 25°C. Thereafter, while still kept in the thermostatic chamber at 25°C, the resin composition was discharged from the syringe for 10 seconds using a dispenser ML-5000XII manufactured by Musashi Engineering Co., Ltd. at a discharge pressure of 0.62 MPa, and the amount of the resin composition discharged was converted into the discharge amount per minute.

[0097] (4) Thermal Conductivity The silicone resin composition was filled into a 30 mm × 50 mm × 6 mm mold and cured by heating at 120°C for 1 hour using a constant temperature dryer. After cooling, the mold was removed to obtain a 6 mm thick sheet. The obtained sheet was divided into two equal parts, and the thermal conductivity was measured using a hot disc thermophysical property measuring device (TPS500, manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0098] (5) BLT Measurement of BLT was performed by sandwiching 0.02 mL of the silicone resin composition between two 10 mm x 10 mm silicon chips and applying a force of 50 N for 60 seconds. Specifically, the silicone resin composition was measured onto a silicon chip, and another silicon chip was placed on top of it, sandwiching the silicone resin composition between the two silicon chips. A sample was obtained by crushing with a force of 50 N for 60 seconds using a push-pull gauge (manufactured by Imada Co., Ltd., SVH-1000N). The thickness of the sample was then measured using a micrometer (manufactured by Mitutoyo Corporation, high-precision digimatic micrometer MDH-25MB). The thickness of the silicone resin composition alone was calculated by subtracting the thickness of the silicon chip, which had been measured previously, from the thickness of the obtained sample, and this was designated as the BLT.

[0099] (6) Type E Hardness The silicone resin composition was filled into a mold measuring 30 mm x 50 mm x 6 mm and cured by heating at 120°C for 1 hour using a constant temperature dryer. After cooling, the mold was removed to obtain a sheet with a thickness of 6 mm. The hardness (Type E) was measured using a Type E durometer (GS-754G, manufactured by Teclock) in accordance with JIS K 6253.

[0100] (7) Relative Dielectric Constant The silicone resin composition was filled into a 100 mm × 100 mm × 0.5 mm mold and cured at 10 MPa and 120°C using a small heat press (H300-05, manufactured by AS ONE). After demolding, a 50 mm × 50 mm × 0.5 mm sheet was cut out from the cured sheet, and the relative dielectric constant in the 10 GHz band was measured using a dielectric property measuring device (Steamline P9377B network analyzer manufactured by Keysight, TER-10H TE mode cavity resonator manufactured by Keycom).

[0101] (8) Dielectric Breakdown Strength The silicone resin composition was filled into a 100 mm × 100 mm × 0.5 mm mold and cured at 10 MPa and 120°C using a small heat press (H300-05, manufactured by AS ONE Co., Ltd.). After demolding, the cured sheet (100 mm × 100 mm × 0.5 mm) was sandwiched between a lower electrode (cylindrical, φ=25 mm) and an upper electrode (spherical, φ=20 mm) in insulating oil. An AC voltage that increased uniformly at a rate of 1 kV / sec was applied using a withstand voltage tester (YPAD-0225, manufactured by Kyonan Electric Co., Ltd.) to measure the dielectric breakdown voltage (kV). The value obtained by dividing by the thickness of the test piece was taken as the dielectric breakdown strength (kV / mm).

[0102] [Materials Used] The following materials were used. The physical properties of each filler are shown in Table 1.

[0103] <Hexagonal boron nitride filler> A1: Hexagonal boron nitride filler obtained in the same manner as in Example 1 of JP 2022-133951 A A2: DF-20 (manufactured by Tokuyama Corporation) A3: S03 (manufactured by Tokuyama Corporation)

[0104] <Thermal conductive filler> B1: Silica filler obtained in the same manner as in Example 3 of JP 2008-019157 A B2: Silfil NSS-3N (silica filler: manufactured by Tokuyama Corporation) B3: Silica filler obtained in the same manner as in Example 9 of WO 2020 / 175160 B4: Sunsil SS-10 (silica filler: manufactured by Tokuyama Corporation)

[0105]

[0106] <Silicone Resin> C1: Polyorganosiloxane having an alkenyl group represented by the following general formula (3) (viscosity at 23°C: 0.1 Pa s)

[0107]

[0108] C2: Polyorganosiloxane having a hydrosilyl group represented by the following general formula (4) (viscosity at 23 ° C: 0.06 Pa s)

[0109]

[0110] C3: Polyorganosiloxane having a hydrosilyl group represented by the following general formula (5) (viscosity at 23 ° C: 0.04 Pa s)

[0111]

[0112] <Hydrosilylation catalyst> Platinum (0)-1,3-divinyltetramethyldisiloxane complex (platinum content 20% by mass) (manufactured by Tokyo Chemical Industry Co., Ltd.) <Reaction inhibitor> 1-ethynyl-1-cyclohexanol (manufactured by Tokyo Chemical Industry Co., Ltd.) <Affinity agent> Silaplane FM-0815J (manufactured by JNC Corporation)

[0113] Example 1: The total amount of silicone resins C1 to C3, hydrosilylation catalyst, and reaction inhibitor was measured to be 36 parts by volume, 38 parts by volume of boron nitride filler A1, 17 parts by volume of silica filler B2, and 9 parts by volume of affinity agent. These were then kneaded under reduced pressure in a planetary centrifugal mixer (Thinky Corporation: ARV-310P) to prepare a paste-like silicone resin composition. The resulting resin composition was evaluated for its discharge rate, thermal conductivity, BLT, hardness (Type E), relative dielectric constant, and dielectric breakdown strength. Hereinafter, silicone resins C1 to C3, hydrosilylation catalyst, and reaction inhibitor are also referred to as "silicone resin, etc." Silicone resins C1 to C3 were blended in a mass ratio of C1:C2:C3 = 56:39:3. 0.4 parts by mass of the reaction inhibitor was blended per 100 parts by mass of the total silicone resin. The hydrosilylation catalyst was blended in an amount of 0.04 parts by mass per 100 parts by mass of the total amount of silicone resin. The evaluation results of the resulting resin composition are shown in Table 2.

[0114] Examples 2 to 4, Comparative Examples 1 to 7 Silicone resin compositions were obtained and evaluated in the same manner as in Example 1, except that the formulation of the silicone resin composition was changed as shown in Table 2. The evaluation results of the obtained silicone resin compositions are shown in Table 2. In Comparative Examples 2, 4, and 6, the mixture did not become a paste, and the physical properties of the silicone resin compositions could not be evaluated.

[0115]

[0116] In Examples 1 to 3, a hexagonal boron nitride filler A1 having a pore size of 0.5 to 4.0 μm and a silica filler having a D50 of 0.01 to 0.8 μm were used, and the filler loading rate was set to 50% by volume or more, thereby enabling the production of a silicone resin composition that exhibited a high thermal conductivity of 3.0 W / m K or more and a high syringe dischargeability of 10 g / min or more.

[0117] On the other hand, in Comparative Example 1, a silicone resin composition was prepared that did not contain a silica filler with a D50 of 0.01 to 0.8 μm, but the thermal conductivity was low. Furthermore, in Comparative Example 2, the amount of A1 was increased compared to Comparative Example 1 in an attempt to improve thermal conductivity, but the mixture did not become paste-like, making it impossible to evaluate syringe dischargeability, and even if an evaluation were attempted, the syringe dischargeability would be extremely poor. From this, it can be said that it is difficult to obtain a silicone resin composition with high thermal conductivity and syringe dischargeability using only hexagonal boron nitride filler.

[0118] In Comparative Example 3, silica filler with a D50 of 0.01 to 0.8 μm was included, but the amount blended was small, so although the syringe dischargeability of the resulting silicone composition was good, the thermal conductivity showed a low value.

[0119] In Comparative Example 4, in which the D50 of the silica filler was greater than 0.8 μm, the mixture did not become a paste, and even if evaluated, the syringe dischargeability was extremely poor. It is presumed that the effect of the present invention was not obtained because it was difficult for the silica filler to enter the voids in the hexagonal boron nitride filler.

[0120] Similar results were obtained in Example 4 and Comparative Examples 5 and 6, in which A2 was used as the hexagonal boron nitride filler.

[0121] Furthermore, comparing Example 1 and Comparative Example 7, which differ only in the type of hexagonal boron nitride filler, Example 1, which used A1 with a pore size of 0.5 to 4.0 μm, yielded a silicone resin composition with high thermal conductivity and syringe ejection properties, whereas Comparative Example 7, which used A3 with a pore size of more than 4.0 μm, did not yield high thermal conductivity. It is presumed that the secondary structure of hexagonal boron nitride is prone to collapse, limiting the formation of heat conduction paths and reducing the effect of improving thermal conductivity.

Claims

1. A silicone resin composition comprising a silicone resin, a hexagonal boron nitride filler, and a thermally conductive filler other than the hexagonal boron nitride filler, wherein the hexagonal boron nitride filler has a volume-based median pore diameter of 0.5 to 4.0 μm as measured by mercury intrusion porosimetry, the thermally conductive filler has a D50 of 0.01 to 0.8 μm, the hexagonal boron nitride filler has a filling rate of 30% by volume or more, and the total filling rate of the hexagonal boron nitride filler and the thermally conductive filler is 50% by volume or more.

2. The silicone resin composition according to claim 1, wherein the hexagonal boron nitride filler has a D90 of 250 μm or less.

3. The silicone resin composition according to claim 1, wherein the volume ratio of said hexagonal boron nitride filler to said thermally conductive filler is 2:1 to 10:

1.

4. The silicone resin composition according to claim 1, wherein the thermally conductive filler is a silica filler.

5. A cured product of the silicone resin composition according to any one of claims 1 to 4.

6. The silicone resin composition according to any one of claims 1 to 4, which is filled in a syringe.

7. An electronic component comprising a heat-generating member, a cooling member, and the silicone resin composition or its cured product according to any one of claims 1 to 4, arranged so as to be in contact with the heat-generating member and the cooling member.

8. A method for manufacturing an electronic component having a heat-generating member and a cooling member, comprising the steps of: discharging the silicone resin composition according to claim 6 from a syringe and applying it to at least one of the heat-generating member and the cooling member; and then pressing the heat-generating member and the cooling member together via the silicone resin composition.

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