Resin composition

Abstract

To obtain a silicone resin composition comprising a silicone resin and a hexagonal boron nitride filler, exhibiting high thermal conductivity and superior discharge performance from a syringe.SOLUTION: A silicone resin composition comprises a silicone resin, a hexagonal boron nitride filler, and a thermally conductive filler, wherein the hexagonal boron nitride filler has a pore volume-based median 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 ratio of the hexagonal boron nitride filler is 30 vol.% or more, and the total filling ratio of the hexagonal boron nitride filler and the thermally conductive filler is 50 vol.% or more.SELECTED DRAWING: None

Description

[Technical Field]

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

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

[0003] Thermal interface materials generally use 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 is characterized by 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 with a boron nitride filling rate of 27 mass % 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. Although boron nitride is exemplified as the thermally conductive filler, no examples using boron nitride are disclosed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] WO2023 / 090240 [Patent Document 2] WO2022 / 158029 [Patent Document 3] Japanese Patent Publication No. 2023-168633 Summary of the Invention [Problem to be solved by the invention]

[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 or a cooling component, and then the other component is pressed against the coated surface to thinly compress 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 compressible.

[0009] Here, because hexagonal boron nitride has flat primary particles and few functional groups on the particle surface, incorporating a large amount into a silicone resin tends to significantly increase the viscosity of the resin composition. When 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 itself can be used even if it has a high viscosity. However, in the case of a paste or liquid TIM, if the composition has a high viscosity and poor syringe dischargeability, handling is impaired and it becomes difficult to easily crush 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, high-capacity communications, has expanded. For circuit boards used in such applications, the high dielectric constant of thermal interface materials raises concerns about the generation of high-frequency noise. Therefore, the use of silicone resin compositions containing hexagonal boron nitride as a filler, which has a low dielectric constant, is considered effective. However, as mentioned above, hexagonal boron nitride has low affinity with silicone resins due to its flat primary particles and the lack of functional groups on the particle surface. Increasing the compounding amount to increase thermal conductivity reduces the fluidity of the silicone resin composition, impairing syringeability, making it difficult to handle and difficult to easily crush into a thin film. In fact, in Patent Document 2, the examples show a boron nitride content of 27% by mass (approximately 25% by volume) and demonstrating excellent workability and viscosity. However, in Comparative Example 2, where the boron nitride content was 32% by mass (approximately 30% by volume), the viscosity was so high that it was impossible to measure, and syringeability was also expected to be poor. 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. [Means for solving the problem]

[0011] In order to solve the above problems, the present inventors conducted extensive research and discovered 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.

[0012] Specifically, the present invention provides a silicone resin composition comprising 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 hexagonal boron nitride filler has a filling rate of 30% by volume or more, and the combined filling rate of the hexagonal boron nitride filler and the thermally conductive filler is 50% by volume or more. The hexagonal boron nitride filler preferably has a D90 of 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 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.

[0013] Furthermore, one embodiment of the present invention can be an electronic component comprising a heat-generating member, a cooling member, and the silicone composition or a cured product thereof arranged so as to be in contact with the heat-generating member and the cooling member.

[0014] Furthermore, as a method for manufacturing an electronic component having a heat-generating member and a cooling member, one embodiment of the present invention can include a method for manufacturing an electronic component, 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 or the cooling member, and then pressing the heat-generating member and the cooling member together with the silicone resin composition interposed therebetween. [Effects of the Invention]

[0015] According to the present invention, a silicone resin composition having high thermal conductivity due to a high loading of hexagonal boron nitride filler and high ejection properties can be obtained. By using this 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. DETAILED DESCRIPTION OF THE INVENTION

[0016] The resin composition of the present invention contains a silicone resin, a hexagonal boron nitride filler, and a thermally conductive filler. Each component will be described below.

[0017] <Silicone resin> The silicone resin is not particularly limited, and known silicone resins can be used without particular limitation. Examples of silicone resins include polyorganosiloxanes. Examples of the polyorganosiloxanes include polyorganosiloxanes having alkenyl groups, polyorganosiloxanes having hydrosilyl groups, and dialkylpolyorganosiloxanes. Multiple types of polyorganosiloxanes may be used in combination.

[0018] 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 Examples of the polyorganosiloxane include polyorganosiloxanes represented by the following formula: One type of polyorganosiloxane may be used, or two or more types may be used.

[0019] R xis 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 1 or more, more preferably 2 or more. The alkenyl group may be bonded to a silicon atom at the molecular chain terminal, a silicon atom in the molecular chain middle, or both. However, from the viewpoints of the curing speed when curing the present composition as described below and the physical properties of the resulting cured product, it is preferred 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.

[0020] 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, and more preferably 1 to 10. y Examples 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; groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as chlorine, fluorine, and bromine, or with a cyano group, such as halogenated hydrocarbon groups such as chloromethyl, trifluoropropyl, chlorophenyl, bromophenyl, dibromophenyl, tetrachlorophenyl, fluorophenyl, and difluorophenyl; and cyanoalkyl groups such as α-cyanoethyl, β-cyanopropyl, and γ-cyanopropyl. Among these, alkyl groups and aryl groups are preferred, and methyl and phenyl groups are more preferred.

[0021] e and f are positive numbers satisfying 0 < e < 3, 0 < f < 3, and 1 < e + f < 3. For example, the viscosity of the polyorganosiloxane may be appropriately adjusted to be 0.01 to 10 Pa·s. Preferably, 0.0005 ≦ e ≦ 1, 1.5 ≦ f < 2.4, and 1.5 < e + f < 2.5, and more preferably, the numbers satisfy 0.001 ≦ e ≦ 0.5, 1.8 ≦ f ≦ 2.1, and 1.8 < e + f ≦ 2.2.

[0022] The molecular structure of the polyorganosiloxane may be linear, branched, cyclic, or three-dimensional network, and the polyorganosiloxane may be a mixture of these. The viscosity of the polyorganosiloxane at 23°C is preferably 0.01 to 10 Pa·s from the viewpoint of obtaining a composition having desired physical properties with good workability.

[0023] Examples of the polyorganosiloxane having a hydrosilyl group include, for example, the polyorganosiloxane represented by the average composition formula R z g H h SiO [4-(g+h)] / 2 One kind of the polyorganosiloxane may be used, or two or more kinds may be used.

[0024] R z is a substituted or unsubstituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond. Examples of R z include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, hexyl group, cyclohexyl group, octyl group; aryl groups such as phenyl group, tolyl group; aralkyl groups such as benzyl group, phenylethyl group; groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine, chlorine, bromine or cyano group, for example, chloromethyl group, bromoethyl group, trifluoropropyl group, cyanoethyl group. Among these, an alkyl group is preferred, and a methyl group is more preferred from the viewpoints of ease of synthesis and cost.

[0025] g and h are numbers satisfying 0.5 ≦ g ≦ 2, 0 < h ≦ 2, and 0.5 < g + h ≦ 3. For example, the viscosity of the polyorganosiloxane may be appropriately adjusted to be 0.01 to 10 Pa·s. Preferably, they are numbers satisfying 0.6 ≦ g ≦ 1.9, 0.01 ≦ h ≦ 1.0, and 0.6 < g + h ≦ 2.8.

[0026] Examples of the dialkyl polyorganosiloxane include, for example, a polyorganosiloxane represented by the average compositional formula R a R b SiO. The polyorganosiloxane may be used alone or in combination of two or more.

[0027] R a and R b are each independently a substituted or unsubstituted monovalent hydrocarbon group不含脂肪族不飽和結合, and the number of carbon atoms is preferably 1 to 12, more preferably 1 to 10. R a and R b can be, for example, the functional groups exemplified for the above R y or R z .

[0028] Examples of the dialkyl polyorganosiloxane include, for example, a linear dimethylpolysiloxane represented by the following formula (1).

[0029]

Chemical formula

[0030] (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, more preferably 0.02 to 5 Pa·s.) In addition, examples of the dimethylpolysiloxane include compounds in which one or more methyl groups in formula (1) are substituted with monovalent hydrocarbon groups other than methyl groups. However, the substituted compound has at least one -(Si(CH3)2-O)- structure. Examples of the substituent include the above R y or R z It should be noted that the text seems to have some parts that might be incomplete or unclear in terms of chemical expressions and language. The translation is done as accurately as possible based on the provided text. If there are any specific corrections or clarifications needed for the original text, it would be beneficial for a more precise translation.Examples of the functional groups include those exemplified in

[0031] 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 in a desired location before hardening, deformed into a desired shape, and then hardened, so that its properties can be effectively exerted.In this case, the resin composition of the present invention may previously contain both the polyorganosiloxane having alkenyl group and the polyorganosiloxane having hydrosilyl group.

[0032] When the silicone resin composition contains both the polyorganosiloxane having the alkenyl group and the polyorganosiloxane having the hydrosilyl group, the blending amount is preferably such that the number of hydrogen atoms bonded to the silicon atom of the polyorganosiloxane having the hydrosilyl group is 0.1 to 2.0, particularly 0.2 to 1.5, per alkenyl group bonded to the silicon atom of the polyorganosiloxane having the alkenyl group, from the viewpoint that it is easy to obtain physical properties suitable for a heat dissipation material after curing.

[0033] <Hydrosilylation catalyst> When the silicone resin composition contains both the polyorganosiloxane having an alkenyl group and the polyorganosiloxane having a hydrosilyl group, the silicone resin composition may contain a hydrosilylation catalyst used in the curing reaction. The hydrosilylation catalyst may be any known catalyst, and examples thereof include platinum group metals such as platinum, rhodium, ruthenium, and palladium, or compounds thereof. Examples of platinum group metal compounds include platinum dichloride, platinum dibromide, platinum tetrachloride, chloroplatinic acid, alcohol-modified chloroplatinic acid, Karsteds 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. The amount of the hydrosilylation catalyst may be any amount necessary for curing, and may be adjusted appropriately depending on the desired curing rate, etc., but typically, the amount in terms of platinum element is 0.0001 part by mass or more, preferably 0.001 part by mass or more, and 1 part by mass or less, preferably 0.1 part by mass or less, per 100 parts by mass of the total of the polyorganosiloxane having alkenyl groups and the polyorganosiloxane having hydrosilyl groups.

[0034] <Reaction inhibitor> When the silicone resin composition contains the hydrosilylation catalyst, the silicone resin composition may contain a reaction inhibitor to inhibit the curing reaction. This inhibits the curing reaction of the silicone resin composition before use, thereby improving storage stability. Furthermore, it inhibits a rapid curing reaction during use, thereby improving placement workability.

[0035] Examples of reaction inhibitors include acetylene alcohols, such as 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.

[0036] The content of the reaction inhibitor in the silicone resin composition is, for example, 0.05 parts by mass, 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.

[0037] <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 for both high dischargeability and high thermal conductivity. The reason for this is unclear, but the present inventors believe it to be as follows.

[0038] As described 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 thermal conductivity reduces the fluidity of the silicone resin composition and its syringe ejection properties. By setting the pore size of the hexagonal boron nitride filler to the above-mentioned lower limit or more and using it in combination with a thermally conductive filler (described below), the small particle size thermally conductive filler can penetrate 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 and the thermally conductive filler, which contribute to thermal conductivity, 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 paths will be limited, and the effect of improving thermal conductivity will be reduced.

[0039] The pore size of the hexagonal boron nitride filler is more preferably 1.0 to 3.0 μm.

[0040] The hexagonal boron nitride filler preferably has a D50 of 20 μm or more, more preferably 40 μm or more. This makes it easier to increase the thermal conductivity of the silicone resin 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 can be, for example, 80 μm or less.

[0041] The hexagonal boron nitride filler preferably has a D10 of 1 μm or more, more preferably 5 μm or more. This makes it easier to reduce the viscosity of the silicone resin composition. The upper limit of 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 can be, for example, 20 μm or less.

[0042] 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 silicone resin 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 can be, for example, 80 μm or more.

[0043] In the present invention, D10, D50 and D90 are particle sizes at 10%, 50% and 90% cumulative, respectively, in the volume-based particle size distribution measured by a laser diffraction scattering method.

[0044] The specific surface area of ​​the hexagonal boron nitride filler is not particularly limited, but is preferably 1.0 to 10 m 2 / g, and 2.0 to 9.0 m 2 / g, and more preferably 4.0 to 8.0m 2 / g is even more preferable. By having a specific surface area within this range, it becomes easy to improve the thermal conductivity of the silicone resin composition, and also to improve dispersibility in the silicone resin, making it easy to reduce the viscosity of the silicone resin composition and improve its operability. The specific surface area can be measured by the BET one-point method using nitrogen gas adsorption.

[0045] The hexagonal boron nitride filler may consist of independent single particles or agglomerated particles formed by the aggregation of several small primary particles. It may also consist 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 molded into a thin film such as a sheet, thereby facilitating the formation of a thermal conduction path in the thickness direction. Furthermore, the inclusion of agglomerated particles facilitates stable void formation and easy control of pore size, facilitating the production of the silicone resin composition of the present invention.

[0046] As the hexagonal boron nitride filler, any known filler with a pore diameter of 0.5 to 4.0 μm can be used without any particular limitation. The manufacturing method of the hexagonal boron nitride filler is also not particularly limited, and hexagonal boron nitride fillers manufactured by known methods can be used. Examples of methods for manufacturing hexagonal boron nitride include 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 and 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 after adjusting the particle size distribution using a sieve or classifier.

[0047] <Thermal 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.

[0048] As the thermally conductive filler, any filler other than hexagonal boron nitride filler with 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 obtaining a silicone resin composition for use in circuit boards for high-frequency applications by utilizing the low dielectric constant characteristic of hexagonal boron nitride filler, the use of silica with a low dielectric constant is particularly preferred. For example, from the viewpoint of obtaining a silicone resin composition with a low specific gravity by utilizing the characteristic of hexagonal boron nitride filler, which is a low specific gravity compared to other thermally conductive fillers, the use of silica with a low specific gravity is particularly preferred. For example, from the viewpoint of obtaining a silicone resin composition with high thermal conductivity, the use of alumina with excellent thermal conductivity is particularly preferred.

[0049] The D50 of the thermally conductive filler is preferably 0.05 to 0.5 μm, and more preferably 0.1 to 0.4 μm. 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, and more preferably 0.02 to 0.4. By setting S / P within this range, the thermally conductive filler can easily enter the voids in the hexagonal boron nitride filler.

[0050] The specific surface area of ​​the thermally conductive filler is not particularly limited, but is, for example, 1 to 100 m 2 / g, especially 5-60m 2 The shape of the thermally conductive filler is not particularly limited, but may be spherical from the viewpoint of improving the fluidity of the silicone resin composition.

[0051] The manufacturing method of the thermally conductive filler is not particularly limited, and those manufactured by known methods can be used. As an example, preferred spherical silica fillers include dry-process or wet-process synthetic silica, fused silica, etc., and specific examples of commercially available products include Silfil NSS-3N, Sunsil SS-01, Sunsil SS-04 (manufactured by Tokuyama Corporation), SO-C1, SO-C2 (manufactured by Admatechs Corporation), SFP-20M, UFP-30 (manufactured by Denka Co., Ltd.), etc.

[0052] 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.

[0053] <Other ingredients> The silicone resin composition of the present invention may contain other components than those described above, provided that the effects of the present invention are not impaired. Examples of such other components include curing accelerators, affinity agents, discoloration inhibitors, surfactants, dispersants, colorants, plasticizers, viscosity modifiers, and antibacterial agents.

[0054] Examples of the affinity agent include silane coupling agents, aluminate coupling agents, titanate coupling agents, zirconate coupling agents, etc. Among these, silane coupling agents are preferred from the viewpoint of compatibility with silicone, and alkyl silane coupling agents or polysiloxanes having an alkoxysilyl group at one end are particularly preferred.

[0055] Examples of alkyl-based silane coupling agents include hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, and dodecyltriethoxysilane.

[0056] The polysiloxane having an alkoxysilyl group at one end is preferably a compound represented by the following formula (2).

[0057] [ka]

[0058] 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. Specifically, R z Examples of the groups include the same groups as those exemplified in the group 1. Preferably, an alkyl group is used, and more preferably, a methyl group or an ethyl group is used. 1 may be the same or different from each other.

[0059] 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. Specifically, R z Examples of the alkyl group include the same groups as those exemplified in 1. Preferably, an alkyl group is used, and more preferably, an n-butyl group or a methyl group is used.

[0060] R 3 is an alkoxysilyl group, and examples thereof 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. Preferably, a trialkoxysilyl group is used, and more preferably, a trimethoxysilyl group or a triethoxysilyl group is used.

[0061] For example, k is an integer of 0 or more and 100 or less, preferably 10 or more and 50 or less.

[0062] For example, j is an integer of 0 or more and 10 or less, preferably 1 or more, and preferably 8 or less, and more preferably 5 or less.

[0063] The content of the affinity agent in the silicone resin 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 silicone resin composition.

[0064] <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, wherein 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 silicone resin 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 silicone resin 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 silicone resin composition.

[0065] The filling rate of the hexagonal boron nitride filler is preferably 35% by volume or more, and although there is no particular upper limit, in order to facilitate good dischargeability, it is preferably 50% by volume or less, and more preferably 45% by volume or less.

[0066] The filler filling rate is preferably 52% by volume or more, and more preferably 54% by volume or more. The higher the filler filling rate, the higher the thermal conductivity, which is preferable, but in terms of a balance with dischargeability, the filler filling rate is preferably 65% ​​by volume or less, and more preferably 60% by volume or less.

[0067] The volume ratio of the hexagonal boron nitride filler to the thermally conductive filler is preferably 2:1 to 5:1, and more preferably 2:1 to 4:1, which makes it easy to balance the thermal conductivity and dischargeability of the silicone resin composition.

[0068] In order to take advantage of the low dielectric constant of the hexagonal boron nitride filler, it is preferable to reduce the amount of additives that increase the dielectric constant in the silicone resin composition of the present invention. For example, because surfactants increase the dielectric constant, their content is preferably 4% by mass or less, more preferably 1% by mass or less, and even more preferably zero, relative to the total resin composition. 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, and even more preferably zero, relative to the total resin composition.

[0069] The silicone resin composition of the present invention preferably has a discharge rate of 10 g / min or more when filled into a discharge container having an inner diameter of a tip discharge end of 2 mm and discharged at a discharge pressure of 0.62 MPa. This provides high dischargeability and easy handling, 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 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 it is preferably 500 g / min or less, and more preferably 400 g / min or less. The discharge rate is measured by filling the resin composition into a syringe having an inner diameter of a tip discharge end of 2 mm and discharging it at 25°C at a discharge pressure of 0.62 MPa.

[0070] The thickness (hereinafter sometimes referred to as "BLT") of the silicone resin composition of the present invention, measured after 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, is preferably 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less. This allows the silicone resin 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. While 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, a BLT of 10 μm or more is preferred, more preferably 20 μm or more, and particularly preferably 30 μm or more is particularly preferred.

[0071] The silicone resin composition or cured product thereof of the present invention preferably has a thermal conductivity of 3.0 W / m K or more, and preferably 3.5 W / m K or more, as measured by the hot disk method. This provides high heat dissipation performance when used as a heat dissipation component, enabling efficient cooling of heat-generating parts of electronic components. There is no particular upper limit to the thermal conductivity of the silicone resin composition or cured product thereof; the higher the better, but it may be, for example, 10.0 W / m K or less.

[0072] The silicone resin composition of the present invention preferably has a Type E hardness of a cured product of from 20 to 90, more preferably from 30 to 80. When the hardness is within this range, the cured product has appropriate flexibility, improves its ability to conform to heat-generating parts of electronic components, and can exhibit heat dissipation performance more efficiently.

[0073] The silicone resin composition of the present invention preferably has a dielectric constant of 4.5 or less, more preferably 4.0 or less, measured at 10 GHz after curing. 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.

[0074] The silicone resin composition of the present invention preferably has a dielectric breakdown strength of 20 kV / mm or more, more preferably 25 kV / mm or more, after curing. 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; the higher the better, but it may be, for example, 50 kV / mm or less.

[0075] <Method of manufacturing silicone resin composition> The silicone resin composition of the present invention can be produced by mixing a silicone resin, a hexagonal boron nitride filler, a thermally conductive filler, and, if necessary, other components. The mixing method is not particularly 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 in a mortar or the like.

[0076] <Form of Silicone Resin Composition> The silicone resin composition of the present invention is in the form of a paste or liquid having flowability. The silicone resin composition of the present invention may be either a one-component type or a two-component type.

[0077] When the silicone resin composition is a one-component type and contains the polyorganosiloxane having an alkenyl group, the polyorganosiloxane having a hydrosilyl group, and the hydrosilylation catalyst, the curing reaction may proceed 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.

[0078] In the case of a two-component silicone resin composition, 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 satisfy the requirements of the present invention, the silicone resin composition of the present invention is still present if they satisfy the requirements of the present claims after mixing. The amounts of each component in the silicone resin composition after mixing can be calculated from the respective compositions of the first and second components and the mixed amounts of the first and second components. The physical properties of the hexagonal boron nitride filler and thermally conductive filler after mixing, such as D10, D50, D90, and pore size, can be calculated from the physical properties of the first and second components and the mixed amounts of the first and second components. The physical properties of the silicone resin composition can be evaluated after mixing. In the case of a two-component silicone resin composition, the physical properties of the silicone resin composition are evaluated after mixing. However, since it is difficult to evaluate the discharge rate after mixing, the first and second components are evaluated separately, and if both satisfy the requirements of the present invention, the silicone resin composition is present.

[0079] In the case of a two-component type, if either the first part or the second part alone satisfies the requirements of the present invention, then each of them is also a silicone resin composition of the present invention.

[0080] When the silicone resin composition contains the polyorganosiloxane having an alkenyl group, the polyorganosiloxane having a hydrosilyl group, and the hydrosilylation catalyst as the silicone resin, to make it a two-component type, it is preferable that the polyorganosiloxane having an alkenyl group, the polyorganosiloxane having a hydrosilyl group, and the hydrosilylation catalyst do not coexist before mixing. Therefore, for example, a first agent contains the polyorganosiloxane having an alkenyl group but does not contain the polyorganosiloxane having a hydrosilyl group, and a second agent contains the polyorganosiloxane having a hydrosilyl group but does not contain the polyorganosiloxane having an alkenyl group. In this case, the hydrosilylation catalyst may be blended into either the first agent or the second agent, or may be blended into both. Alternatively, a first agent may be used that contains a polyorganosiloxane having an alkenyl group and a hydrosilylation catalyst but does not contain a polyorganosiloxane having a hydrosilyl group, and a second agent that contains a polyorganosiloxane having an alkenyl group and a polyorganosiloxane having a hydrosilyl group but does not contain a hydrosilylation catalyst.

[0081] The silicone resin composition of the present invention is preferably filled in a container such as a syringe, tube, or cup. For example, filling a syringe facilitates the application of the silicone resin composition to a heat-generating or cooling portion during the manufacture of electronic components. The syringe into which the silicone resin composition of the present invention is filled is not particularly limited, but from the viewpoint of easy application, a syringe having an inner diameter of the tip discharge part 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 silicone resin composition of the present invention is a two-component type, the composition may be filled into two syringes, which 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 silicone resin composition is being extruded.

[0082] <Applications of resin composition> While the uses of the silicone resin composition of the present invention are not particularly limited, suitable applications include paste or liquid thermal interface materials, particularly thermal greases and gap fillers used in the manufacture of electronic components. Using the silicone resin composition of the present invention as a thermal interface material allows for the production of electronic components comprising a heat-generating component, a cooling component, and a silicone resin composition or a cured product thereof arranged in contact with the heat-generating component and the cooling component. The electronic component can be manufactured, for example, by a manufacturing method including the steps of discharging the silicone resin composition of the present invention from a syringe and applying it to at least one of the heat-generating component or the cooling component, and then pressing the heat-generating component and the cooling component together via the silicone resin composition. In these applications, the silicone resin composition can be easily discharged from a syringe and easily crushed into a thin film, allowing for efficient production of electronic components. Furthermore, the high thermal conductivity of the silicone resin composition or its cured product facilitates efficient cooling of the heat-generating components of electronic components.

[0083] When a silicone resin composition such as a gap filler is cured and used, the silicone resin composition generally contains a polyorganosiloxane having an alkenyl group, a polyorganosiloxane having a hydrosilyl group, and a hydrosilylation catalyst. In this case, 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 temperature or room temperature and heated to harden before use. In this case, an electronic component can be obtained that includes a heat-generating component, a cooling component, and a cured silicone resin composition arranged in contact with the heat-generating component and the cooling component. Such an electronic component can be manufactured by discharging the silicone resin composition of the present invention from a syringe and applying it to at least one of the heat-generating component or the cooling component, then pressing the heat-generating component and the cooling component together via the silicone resin composition, followed by curing the silicone resin composition by heating or the like. [Example]

[0084] 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.

[0085] [Measurement method] Various physical properties in the examples and comparative examples were measured by the following methods.

[0086] (1) D10, D50, 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 calculated from the obtained particle size distribution.

[0087] (2) Pore diameter The pore size of the boron nitride filler was measured by mercury intrusion porosimetry using an Autopore IV9520 manufactured by Micromeritics. The pore size distribution from 0.0036 μm to 200 μm was determined, and the volume-based median diameter was calculated from the cumulative pore size distribution plotted with pore diameter on the horizontal axis and cumulative pore volume on the vertical axis.

[0088] (3) Syringe discharge volume The silicone resin composition was filled into a Musashi Engineering syringe "PSY-30F" (the syringe had an inner diameter of 22 mm at the barrel where the sample was stored and an inner diameter of 2 mm at the tip from which the sample was dispensed) and then allowed 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 dispensed from the syringe for 10 seconds at a discharge pressure of 0.62 Pa using a Musashi Engineering dispenser ML-5000XII, and the amount of resin composition dispensed was converted into the amount dispensed per minute.

[0089] (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 resulting 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.).

[0090] (5) BLT The silicone resin composition (0.02 ml) was sandwiched between two 10 mm x 10 mm silicon chips and subjected to 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. The sample was then crushed with a force of 50 N for 60 seconds using a push-pull gauge (Imada, SVH-1000N) to obtain a sample. The thickness of the sample was then measured using a micrometer (Mitutoyo, high-precision digimatic micrometer MDH-25MB). The thickness of the silicon chips, which had been measured previously, was then subtracted from the thickness of the obtained sample to calculate the thickness of the silicone resin composition alone, which was designated as the BLT.

[0091] (6) Type E hardness 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 demolded to obtain a 6 mm thick sheet. The hardness (Type E) was measured using a Type E durometer (manufactured by Teclock, GS-754G) in accordance with JIS K 6253.

[0092] (7) Dielectric constant The silicone resin composition was filled into a 100 mm × 100 mm × 0.5 mm mold and cured using a small heat press (H300-05, manufactured by AS ONE) at 10 MPa and 120°C. After demolding, a 50 mm × 50 mm × 0.5 mm sheet was cut out from the cured sheet, and the relative permittivity 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).

[0093] (8) Dielectric breakdown strength The silicone resin composition was filled into a 100mm x 100mm x 0.5mm mold and cured at 10MPa and 120°C using a small heat press (H300-05, manufactured by AS ONE Co., Ltd.). After demolding, the cured sheet (100mm x 100mm x 0.5mm) was sandwiched between a lower electrode (cylindrical, φ=25mm) and an upper electrode (spherical, φ=20mm) in insulating oil. A voltage tester (YPAD-0225, manufactured by Kyonan Electric Co., Ltd.) was used to apply a uniformly increasing AC voltage at a rate of 1kV / sec to measure the breakdown voltage (kV). The value obtained by dividing this value by the thickness of the test piece was used as the breakdown strength (kV / mm).

[0094] [Raw materials used] The following raw materials were used: The physical properties of each filler are shown in Table 1.

[0095] <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 (Tokuyama Corporation) A3:S03 (Tokuyama Corporation) <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 WO2020 / 175160 B4: Sunseal SS-10 (silica filler: manufactured by Tokuyama Corporation)

[0096] [Table 1]

[0097] <Silicone resin> C1: Polyorganosiloxane having an alkenyl group represented by the following general formula (3) (viscosity at 23°C: 0.1 Pa s)

[0098] [ka]

[0099] C2: Polyorganosiloxane having a hydrosilyl group represented by the following general formula (4) (viscosity at 23°C: 0.06 Pa s)

[0100] [ka]

[0101] C3: Polyorganosiloxane having a hydrosilyl group represented by the following general formula (5) (viscosity at 23°C: 0.04 Pa s)

[0102] [ka]

[0103] <Hydrosilylation catalyst> Platinum(0)-1,3-divinyltetramethyldisiloxane complex (platinum content 20% by mass) (Tokyo Chemical Industry Co., Ltd.) <Reaction inhibitor> 1-Ethynyl-1-cyclohexanol (Tokyo Chemical Industry Co., Ltd.) <Affinity agent> Silaplane FM-0815J (manufactured by JNC Corporation)

[0104] Example 1 The total amount of silicone resins C1 to C3, hydrosilylation catalyst, and reaction inhibitor (silicone resin, etc.) was measured out to be 36 parts by volume, boron nitride filler A1 was 38 parts by volume, silica filler B2 was 17 parts by volume, and affinity agent was 9 parts by volume. These were then kneaded under reduced pressure in a planetary centrifugal mixer (Thinky Corporation: ARV-310P) to produce a paste-like silicone resin composition, and the resulting resin composition was evaluated for its discharge rate, thermal conductivity, BLT, hardness (Type E), dielectric constant, and dielectric breakdown strength. The silicone resins C1 to C3 were blended in a mass ratio of C1:C2:C3 = 56:39:3. The reaction inhibitor was blended in an amount of 0.4 parts by mass 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 silicone resin. The evaluation results of the obtained resin composition are shown in Table 2.

[0105] (Examples 2 to 8, 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.

[0106] [Table 2]

[0107] In Examples 1 to 3, a hexagonal boron nitride filler A1 with a pore size of 0.5 to 4.0 μm and a silica filler with a D50 of 0.01 to 0.8 μm were used, and the filler loading 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.

[0108] 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 evaluated, the syringe dischargeability was 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.

[0109] Comparative Example 3 contained a silica filler with a D50 of 0.01 to 0.8 μm, but the amount blended was small, so the resulting silicone composition had good syringe dischargeability but showed a low thermal conductivity.

[0110] 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.

[0111] Similar results were obtained in Example 4 and Comparative Examples 5 and 6, in which A2 was used as the hexagonal boron nitride filler.

[0112] 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. This is presumably because the secondary structure of hexagonal boron nitride is prone to collapse, limiting the formation of thermal paths and reducing the effect of improving thermal conductivity.

Claims

1. 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, the total filling rate of the hexagonal boron nitride filler and the thermally conductive filler is 50% by volume or more; Silicone resin composition.

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

3. 2. The silicone resin composition according to claim 1, wherein the volume ratio of the hexagonal boron nitride filler to the 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 composition or a cured product thereof according to any one of claims 1 to 4, which is placed in contact with the heat-generating member and the cooling member.

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

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