Thermally conductive compositions and electronic devices

Abstract

The objective is to provide a thermally conductive composition in which the increase in thermal resistance when exposed to high temperatures for a long period of time is suppressed, and an electronic device equipped with the thermally conductive composition. [Solution] A thermally conductive composition comprising organopolysiloxane A, thermally conductive filler B, and hydrophobic silica C.

Description

[Technical Field]

[0001] This invention relates to a thermally conductive composition and electronic equipment. [Background technology]

[0002] With the miniaturization and increased power output of heat-generating electronic components such as the CPU (Central Processing Unit) in personal computers, the amount of heat generated per unit area from these components has become extremely large. This amount of heat can reach about 20 times that of an iron. To prevent these heat-generating electronic components from failing over the long term, cooling of the heat-generating electronic components is necessary. Metal heat sinks and casings are used for cooling, but if the heat-generating electronic component and the heat sink are in direct contact, microscopic air may be present at the interface, which can hinder heat conduction. Therefore, to efficiently transfer heat, the heat-generating electronic component and the heat sink are sometimes placed with a thermally conductive material in between.

[0003] As a thermally conductive material, for example, a thermally conductive composition is used in which thermally conductive powder is added to a room-temperature curing liquid silicone rubber. Room-temperature curing liquid silicone rubber is mainly classified into one-component and two-component types, and the two-component type is further divided into condensation reaction type and addition reaction type. Thermally conductive compositions containing two-component liquid silicone rubber are used as a two-component curing composition set containing two compositions with different compositions.

[0004] For example, Patent Document 1 describes a thermally conductive polysiloxane composition containing one or more thermally conductive fillers selected from the group consisting of two or more thermally conductive fillers with different average particle sizes, alkoxysilyl group-containing compounds, and dimethylpolysiloxane, which has low viscosity, excellent workability, and high thermal conductivity. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2018 / 016566

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, when a polysiloxane composition as described in Patent Document 1 is mounted as a thermally conductive grease between a heat-generating electronic component and a heat sink, the thermal resistance may increase when exposed to high heat from the electronic component for a long time. In order to ensure the heat dissipation from the electronic component over a long period, it is necessary to suppress such an increase in thermal resistance.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a thermally conductive composition in which an increase in thermal resistance is suppressed even when exposed to high temperature for a long time, and an electronic device including the thermally conductive composition.

Means for Solving the Problems

[0008] The inventors of the present invention have intensively studied to achieve the above object. As a result, they have found that the above problems can be solved by the thermally conductive composition containing an organopolysiloxane A, a thermally conductive filler B, and a hydrophobic silica C, and have completed the present invention.

[0009] That is, the present invention is as follows. <1> An organopolysiloxane A, A thermally conductive filler B, A hydrophobic silica C, and a thermally conductive composition containing the same. Thermally conductive composition. <2> The thermally conductive composition according to <1>, wherein the Asker C hardness is 30 or less. The thermally conductive composition according to <1>. <3> The thermally conductive composition according to <1> or <2>, wherein the Asker C hardness after exposure at 150 ° C. for 1000 hours is 60 or less. The thermally conductive composition according to <1> or <2>. <4> The viscosity η1 under measurement conditions of 25℃ and a shear rate of 1 / s is 500 to 5000 Pa·s. <1> ~ <3> A thermally conductive composition according to any one of the following items. <5> The viscosity η10 under measurement conditions of 25℃ and a shear rate of 10 / s is 100~1000 Pa·s. <1> ~ <4> A thermally conductive composition according to any one of the following items. <6> The ratio of viscosity η1 at 25°C and a shear rate of 1 / s to viscosity η10 at 25°C and a shear rate of 1 / s (η1 / η10) is between 2 and 10. <1> ~ <5> A thermally conductive composition according to any one of the following items. <7> The content of the hydrophobic silica C is 0.01 to 10% by mass relative to the total mass of the thermally conductive filler B. <1> ~ <6> A thermally conductive composition according to any one of the following items. <8> The carbon content of the hydrophobic silica C is 0.1 to 10% by mass. <1> ~ <7> A thermally conductive composition according to any one of the following items. <9> The specific surface area of ​​the hydrophobic silica C measured by the BET method is 10 to 500 m². 2 / g <1> ~ <8> A thermally conductive composition according to any one of the following items. <10> The thermally conductive filler B includes at least one selected from the group consisting of boron nitride, aluminum nitride, aluminum oxide, silicon nitride, silicon oxide, zinc oxide, silica, aluminum hydroxide, magnesium oxide, and carbon nanotubes. <1> ~ <9> A thermally conductive composition according to any one of the following items. <11> The thermally conductive filler B is Thermally conductive filler B1 with an average particle size of 0.1 μm or more and less than 1.0 μm, Thermally conductive filler B2 with an average particle size of 1.0 μm or more and less than 30 μm, A thermally conductive filler B3 with an average particle size of 30 μm or more and 150 μm or less, is included. <1> ~ <10> A thermally conductive composition according to any one of the following items. <12> Electronic components and, <1> ~ <11> A heat sink comprising a thermally conductive composition according to any one of the above, The electronic component and the heat sink are in contact via the thermally conductive composition. electronic equipment. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a thermally conductive composition in which the increase in thermal resistance is suppressed even when exposed to high temperatures for a long period of time, and an electronic device equipped with the thermally conductive composition. [Modes for carrying out the invention]

[0011] The following describes in detail an embodiment of the present invention (hereinafter referred to as "this embodiment"), but the present invention is not limited thereto, and various modifications are possible without departing from its essence.

[0012] 1. Thermally conductive composition The thermally conductive composition of this embodiment comprises organopolysiloxane A, thermally conductive filler B, and hydrophobic silica C. The thermally conductive composition may also optionally contain other components such as surfactants and silane coupling agents.

[0013] The inventors investigated the mechanism by which thermal resistance increases when exposed to high temperatures for a long period of time. As a result, it was found that silica added to impart thixotropy is a factor in the increase in thermal resistance. Specifically, when a portion of organopolysiloxane A bleeds due to prolonged exposure to high temperatures, the silica particles come into close proximity, and the hydrophilic groups on the surfaces of these adjacent silica particles aggregate through non-covalent bonds such as hydrogen bonds. It is presumed that this aggregation of silica reduces the homogeneity within the composition, leading to an increase in thermal resistance. However, the mechanism of thermal resistance increase in this embodiment is not limited to the above.

[0014] In contrast, in this embodiment, hydrophobic silica C is used instead of ordinary silica having hydrophilic groups. This makes it possible to impart thixotropy while suppressing the aggregation of silica particles by hydrogen bonding, etc., even when exposed to high temperatures for a long period of time, and further suppresses the increase in thermal resistance.

[0015] The following provides a detailed explanation of thermally conductive compositions.

[0016] 1.1. Organopolysiloxane A Organopolysiloxane A may be a one-component or two-component type. One-component organopolysiloxane A may be a non-reactive organopolysiloxane, while two-component organopolysiloxane A may be a reactive organopolysiloxane.

[0017] One-component organopolysiloxane A does not need to be mixed with other agents before use and can be used by directly applying the thermally conductive composition to the object.

[0018] Two-component organopolysiloxane A is used after mixing with another agent. Upon mixing, the two organopolysiloxanes react, undergoing addition reactions, condensation reactions, or peroxide curing reactions, resulting in hardening.

[0019] In the case of a two - component type, the heat - conductive composition of the present embodiment may be either of the two agents. For example, in the case of a two - component type of an agent containing vinyl - modified organopolysiloxane and an agent containing hydrosilyl - modified organopolysiloxane, at least one of the agents may be the heat - conductive composition of the present embodiment, and both may satisfy the constitution of the heat - conductive composition of the present embodiment. In other words, if at least one of the agents in the set of two - component type agents is the heat - conductive composition of the present embodiment, the present invention can be implemented.

[0020] Hereinafter, the one - component type organopolysiloxane A1 and the two - component type organopolysiloxane A2 will be described in detail.

[0021] 1.1.1. One - component type organopolysiloxane A1 The one - component type organopolysiloxane A1 is not particularly limited. For example, non - crosslinked silicones such as linear silicone, branched silicone, and cyclic silicone; and crosslinked silicones crosslinked three - dimensionally within the molecule can be mentioned. Among these, non - crosslinked silicones are preferable, and linear silicones are more preferable. By using such a one - component type organopolysiloxane A1, the viscosity tends to decrease and sagging is more suppressed.

[0022] Generally, silicone can be represented by monofunctional units (R 1 SiO 1 / 2 ), difunctional units (R 2 SiO 2 / 2 ), trifunctional units (R 3 SiO 3 / 2 ), and tetrafunctional units (SiO 4 / 2 ). For example, linear silicone can be expressed as having monofunctional units (R 1 SiO 1 / 2 ) constituting the ends and difunctional units (R 2 SiO 2 / 2 ) constituting the main chain (in the following formula, n3, n4 = 0), and cyclic silicone can be expressed as having difunctional units (RSiO 2 / 2It can be expressed as having (n1, n3, n4 = 0 in the formula below). In addition, branched silicones and three-dimensionally crosslinked silicones have three functional units (R) that constitute the branching point. 3 SiO 3 / 2 ) and / or tetrafunctional units (SiO 4 / 2 ) has, and furthermore, a single functional unit (R) that constitutes the end of the branched chain 1 SiO 1 / 2 ), the two functional units that make up the branched chain (R 2 SiO 2 / 2 It can be expressed as having ).

[0023] The compositional formula using such units can be expressed as follows. In the formula below, n1 to n4 represent the compositional ratio of each unit, and can be expressed in a ratio such that the sum of n1 to n4 is 1. Whether or not these units are present can be measured by known methods such as Si-NMR. 1 ~R 4 Each of these elements can independently represent any base. (R 1 SiO 1 / 2 ) n1 (R 2 SiO 2 / 2 ) n2 (R 3 SiO 3 / 2 ) n3 (SiO 4 / 2 ) n4

[0024] The one-component organopolysiloxane A1 is not particularly limited, but examples include non-curing silicones and curing silicones. The non-curing silicone resin is not particularly limited as long as it does not have the functional groups that contribute to curing that curing silicone resins have, or is not used in combination with a catalyst. The curing silicone is not particularly limited, but examples include a combination of two silicones having functional groups that react with each other. Such curing silicones are not particularly limited, but examples include addition-curing silicones, condensation-curing silicones, and peroxide-curing silicones.

[0025] Among these, organopolysiloxane A is preferably a non-curing silicone. This tends to improve handling.

[0026] Furthermore, while not particularly limited, one-component organopolysiloxane A1 can be dimethyl silicone, diphenyl silicone, or methylphenyl silicone. These silicones may also have organic groups introduced into their side chains and / or terminals. Such silicones are not particularly limited, but can be non-reactive silicones such as long-chain alkyl-modified silicones, polyether-modified silicones, aralkyl-modified silicones, fatty acid ester-modified silicones, or fatty acid amide-modified silicones; and reactive silicones such as amine-modified silicones, epoxy-modified silicones, mercapto-modified silicones, carboxyl-modified silicones, carbinol-modified silicones, or hydrogen-modified silicones.

[0027] Among these, dimethyl silicone, diphenyl silicone, methylphenyl silicone, and non-reactive silicone are preferred, with dimethyl silicone being more preferred. Using such a one-component organopolysiloxane A1 tends to reduce viscosity and further suppress dripping.

[0028] The viscosity of one-component organopolysiloxane A1 at 25°C is preferably 30 to 2000 mm². 2 / s, 50~1000mm 2 / s, 70~500mm 2 The viscosity is / s. Because the viscosity of organopolysiloxane A21 is within the above range, its handling as a one-component agent tends to improve.

[0029] The content of one-component organopolysiloxane A1 is preferably 70-100% by mass, 80-100% by mass, 90-99% by mass, or 95-99% by mass, relative to the total amount of the thermal conductive composition excluding thermal conductive filler B.

[0030] Even in a one-component type, a reactive organopolysiloxane may be included in addition to the non-reactive one-component organopolysiloxane A1. The content of such reactive organopolysiloxane is not particularly limited, but is preferably 0.1 to 5% by mass, 0.5 to 4% by mass, or 1 to 3% by mass, relative to the total amount of non-reactive organopolysiloxane and reactive organopolysiloxane.

[0031] For example, a high molecular weight reactive organopolysiloxane may be used as a flow modifier. The inclusion of a flow modifier tends to improve the uniformity of the thermally conductive composition, enhance the dispersibility of its components, and make the composition smoother. The reactive organopolysiloxane acting as a flow modifier only needs to improve the smoothness of the thermally conductive composition through its high molecular weight; it does not need to modify the flowability through its reactivity. In other words, a high molecular weight non-reactive organopolysiloxane A1 may be used to improve flowability.

[0032] Reactive organopolysiloxanes that can be used as fluidity modifiers are not particularly limited, but include amine-modified silicones, epoxy-modified silicones, mercapto-modified silicones, carboxyl-modified silicones, carbinol-modified silicones, hydrogen-modified silicones, vinyl-modified organopolysiloxanes, and hydrosilyl-modified organopolysiloxanes.

[0033] Here, the weight-average molecular weight of the reactive or non-reactive organopolysiloxane used as a fluid modifier is preferably 100,000 to 1,000,000, 200,000 to 900,000, 300,000 to 800,000, or 400,000 to 700,000.

[0034] Furthermore, the content of constituent units containing reactive groups such as vinyl groups, as exemplified below, in the fluidity modifier is preferably 0.5 mol% or less, 0.4 mol% or less, 0.3 mol% or less, 0.2 mol% or less, and 0.1 mol% or less, relative to 100 mol% of the polymer's constituent units.

[0035] 1.1.2. Two-component organopolysiloxane A2 The two-component organopolysiloxane A2 is not particularly limited, but examples include addition reaction type organopolysiloxanes, condensation reaction type organopolysiloxanes, and peroxide curing type organopolysiloxanes.

[0036] The addition reaction type two-component organopolysiloxane A2 is not particularly limited, but examples include a combination of a vinyl-modified organopolysiloxane and a hydrosilyl-modified organopolysiloxane. The addition reaction between the vinyl group of the vinyl-modified organopolysiloxane and the hydrosilyl group of the hydrosilyl-modified organopolysiloxane can be accelerated by an addition reaction catalyst.

[0037] The two-component organopolysiloxane A2 of the condensation reaction type is not particularly limited, but examples include combinations of organopolysiloxanes having silanol groups and / or hydrolyzable groups. In these organopolysiloxanes, silanol groups condense with each other, or a silanol group condenses with a hydrolyzable group. The hydrolyzable group is not particularly limited, but examples include alkoxy groups, acetoxy groups, oxime groups, aminooxy groups, and propenoxy groups.

[0038] The peroxide-curable two-component organopolysiloxane A2 is not particularly limited, but examples include combinations of organopolysiloxanes having unsaturated hydrocarbon groups such as vinyl groups. This reaction can be accelerated by alkyl organic peroxides or acyl organic peroxides.

[0039] In two-component organopolysiloxane A2, the reactive organopolysiloxane may be contained in separate agents, or the addition reaction catalyst or organic peroxide may be contained in a separate agent from the organopolysiloxane.

[0040] Of the above, vinyl-modified organopolysiloxane A21 (hereinafter also referred to simply as "organopolysiloxane A21") is an organopolysiloxane having at least one vinyl group. Organopolysiloxane A21 may have vinyl groups in its side chains and / or terminals. Such organopolysiloxane has a structural unit represented by the following formula (b1-1) or a terminal structure represented by the following formula (b1-2). Organopolysiloxane A21 may, for example, have at least one of the structural unit represented by the formula (b1-1) and the terminal structure represented by the formula (b1-2), and a structural unit represented by the formula (b1-3).

[0041] [ka]

[0042] Here, in formulas (b1-1), (b1-2), and (b1-3), R is any monovalent hydrocarbon group which may have substituents. That is, in organopolysiloxane A21, any monovalent hydrocarbon group which may have substituents is bonded to the side chains of the siloxane skeleton.

[0043] Such monovalent hydrocarbon groups are not particularly limited, but include, for example, alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl, 2-phenylethyl, and 2-phenylpropyl groups; and groups having substituents on these groups. Examples of substituents on the above monovalent hydrocarbon groups include halogen atoms, particularly fluorine or chlorine atoms.

[0044] The number of vinyl groups per molecule of organopolysiloxane A21 is preferably 2.0 or more, 2.5 or more, or 3.0 or more. This allows for the formation of a network structure when reacted with organopolysiloxane A22, resulting in a cured product with superior mechanical strength.

[0045] Organopolysiloxane A21 preferably contains at least organopolysiloxane having vinyl groups at both ends. Using such organopolysiloxane tends to allow for adjustment of the crosslinking density of the resulting cured product. Similarly, organopolysiloxane A21 preferably contains at least polydimethylsiloxane having vinyl groups at both ends.

[0046] The viscosity of organopolysiloxane A21 at 25°C is preferably 30-1000 mPa·s, 60-700 mPa·s, or 70-500 mPa·s. Having a viscosity within this range tends to result in excellent handling characteristics.

[0047] The content of vinyl-modified organopolysiloxane A21 is preferably 50-99% by mass, 55-98% by mass, and 60-95% by mass, relative to the total amount of the thermal conductive composition excluding thermal conductive filler B.

[0048] Furthermore, hydrosilyl-modified organopolysiloxane A22 (hereinafter also referred to simply as "organopolysiloxane A22") is an organopolysiloxane having at least one hydrosilyl group. Organopolysiloxane A22 may have hydrosilyl groups in its side chains and / or terminals. Such organopolysiloxane has a structural unit represented by the following formula (e2-1) or a terminal structure represented by the following formula (e2-2). Organopolysiloxane A22 may, for example, have at least one of the structural unit represented by the formula (e2-1) and the terminal structure represented by the formula (e2-2), and a structural unit represented by the formula (e2-3). [ka]

[0049] Here, in formulas (e2-1), (e2-2), and (e2-3), R is any monovalent hydrocarbon group which may have substituents. That is, in organopolysiloxane A22, any monovalent hydrocarbon group which may have substituents is bonded to the side chains of the siloxane skeleton.

[0050] Examples of such monovalent hydrocarbon groups include the same monovalent hydrocarbon groups that vinyl-modified organopolysiloxane A21 may have.

[0051] The number of hydrosilyl groups per molecule of organopolysiloxane A22 is preferably 2.0 or more, 2.5 or more, or 3.0 or more. This allows for the formation of a network structure when reacted with organopolysiloxane A21, resulting in a cured product with superior mechanical strength.

[0052] The viscosity of organopolysiloxane A22 at 25°C is preferably 1 to 300 mPa·s, 2 to 200 mPa·s, and 3 to 100 mPa·s. Having a viscosity within this range tends to result in excellent handling properties.

[0053] The content of organopolysiloxane A22 is preferably 1 to 50% by mass, 2 to 45% by mass, and 5 to 40% by mass, relative to the total amount of the thermal conductive composition excluding thermal conductive filler B.

[0054] 1.2. Thermally conductive filler B The thermally conductive filler B is not particularly limited, but examples include boron nitride, aluminum nitride, aluminum oxide, silicon nitride, silicon oxide, zinc oxide, silica, aluminum hydroxide, magnesium oxide, metallic aluminum, diamond, carbon, indium, gallium, copper, silver, iron, nickel, gold, tin, and metallic silicon. Examples of carbon include graphite, fullerene, graphene, and carbon nanotubes. The thermally conductive filler B can be used individually or in any combination and ratio of two or more types.

[0055] Among these, it is preferable to include at least one selected from the group consisting of boron nitride, aluminum nitride, aluminum oxide, silicon nitride, silicon oxide, zinc oxide, silica, aluminum hydroxide, magnesium oxide, and carbon, more preferably aluminum nitride and / or aluminum oxide, and particularly preferably aluminum nitride and aluminum oxide. Using such a thermally conductive filler B tends to further improve thermal conductivity.

[0056] The average particle size of the thermally conductive filler B is preferably 0.1 μm to 150 μm, and more preferably 0.1 μm to 100 μm. Having the average particle size of the thermally conductive filler B within this range tends to improve the fluidity of the thermally conductive composition, as well as the dispersibility and packing properties of the thermally conductive filler B. In this specification, the average particle size refers to the D50 (median diameter).

[0057] Furthermore, the thermal conductive filler B may be a mixture of fillers with different average particle sizes. For example, one or more of the following may be used as the thermal conductive filler B: thermal conductive filler B1 with an average particle size of 0.1 μm or more and less than 1.0 μm, thermal conductive filler B2 with an average particle size of 1.0 μm or more and less than 30 μm, and thermal conductive filler B3 with an average particle size of 30 μm or more and 150 μm or less.

[0058] The content of thermal conductive filler B1 is preferably 0.1 to 40% by mass, 5.0 to 35% by mass, 15 to 30% by mass, or 20 to 25% by mass, relative to the total amount of thermal conductive filler components. When the content of thermal conductive filler B1 is within the above range, thermal conductivity is further improved, aggregation during heat cycling is further suppressed, and the increase in thermal resistance when exposed to high temperatures for a long period of time tends to be suppressed.

[0059] The content of thermal conductive filler B2 is preferably 10 to 50% by mass, 15 to 45% by mass, 20 to 40% by mass, or 25 to 35% by mass, relative to the total amount of thermal conductive filler B. When the content of thermal conductive filler B2 is within the above range, thermal conductivity is further improved, viscosity is further reduced, and hardness changes and bleeding tend to be further suppressed.

[0060] The content of thermal conductive filler B3 is preferably 30 to 60% by mass, 35 to 55% by mass, and may also be 40 to 50% by mass, relative to the total amount of thermal conductive filler B. When the content of thermal conductive filler B3 is within the above range, thermal conductivity tends to be further improved and viscosity tends to be further reduced.

[0061] The total content of thermally conductive filler B is preferably 2,500 to 4,500 parts by mass, 2,750 to 4,250 parts by mass, 3,000 to 4,000 parts by mass, or 3,250 to 3,750 parts by mass, per 100 parts by mass of non-reactive organopolysiloxane A. When the content of thermally conductive filler B is within the above range, the increase in thermal resistance when exposed to high temperatures for a long period during a heat cycle is suppressed, and thermal conductivity is further improved, viscosity is further reduced, and hardness changes and bleeding tend to be further suppressed.

[0062] Furthermore, each filler component may be surface-treated with a surface treatment agent by a known wet or dry treatment method. The surface treatment agent is not particularly limited, but examples include silane coupling agents, which will be described later, although the silane coupling agent may be provided separately regardless of this surface treatment.

[0063] 1.3. Hydrophobic Silica C Hydrophilic silica refers to silica that has hydrophilic groups such as Si-OH groups on its surface. In contrast, hydrophobic silica in this embodiment is silica that has been hydrophobized by grafting hydrophobic groups onto the Si-OH groups of hydrophilic silica. Therefore, silica that has not undergone any hydrophobic treatment is hydrophilic silica. There are no particular limitations on the hydrophobic treatment, but examples include a method of obtaining hydrophobic silica by reacting hydrophilic silica with methylchlorosilane or a silane coupling agent, a method of hydrophobizing hydrophilic silica with a high molecular weight organopolysiloxane, and a method of hydrophobizing hydrophilic silica with hexamethyldisilazane and an organopolysiloxane.

[0064] Examples of hydrophobic agents for hydrophobicization include silane coupling agents, silylation agents, silane coupling agents having alkyl fluoride, organic titanate coupling agents, aluminum coupling agents, silicone oil, and modified silicone oil. The hydrophobic silica C in this embodiment is not limited to hydrophobic silica obtained by the above-mentioned hydrophobic method or hydrophobic silica made hydrophobic by the above-mentioned hydrophobic agents, but can be any silica having hydrophobic functional groups. Hydrophobic silica C can be used alone or in any combination and ratio of two or more types.

[0065] Hydrophobic silica C is not particularly limited, but is preferably hydrophobic silica whose surface is modified with functional groups such as trimethylsilyl, dimethylsilyl, alkylsilyl, aminoalkylsilyl, methacrylatesilyl, or dimethylpolysiloxane, and more preferably hydrophobic silica modified with dimethylpolysiloxane. By using such hydrophobic silica C, the increase in thermal resistance when exposed to high temperatures for a long period of time tends to be suppressed. Furthermore, aggregation during heat cycling tends to be suppressed, and hardness changes and bleeding tend to be suppressed. In addition, thixotropy is improved, sagging is suppressed, viscosity is reduced, and coating workability tends to be improved.

[0066] The carbon content of hydrophobic silica C is not particularly limited, but is preferably 0.1 to 10% by mass, 1.0 to 9% by mass, 2.0 to 7.5% by mass, or 3.5 to 5.0% by mass. When the carbon content of hydrophobic silica C is within the above range, the increase in thermal resistance when exposed to high temperatures for a long period of time tends to be suppressed. Furthermore, aggregation during heat cycling tends to be suppressed, and hardness changes and bleeding tend to be suppressed. In addition, thixotropy is improved, sagging is suppressed, viscosity is reduced, and coating workability tends to be improved. Note that the carbon content is a value that quantitatively indicates the carbon chains added during the hydrophobic treatment, and may be measured using an NC quantity measuring device (Sumigraph NC-22F) manufactured by Sumika Analysis Center.

[0067] The specific surface area of ​​hydrophobic silica C obtained by the BET method is not particularly limited, but is preferably 10 to 500 m². 2 / g, 40-300m 2 It is / g, and ranges from 60 to 200m 2 It is / g, and is 80-120m 2 The value is / g. When the specific surface area of ​​hydrophobic silica C measured by the BET method is within the above range, the increase in thermal resistance when exposed to high temperatures for a long period of time tends to be further suppressed. In addition, aggregation during heat cycling tends to be further suppressed, and hardness changes and bleeding tend to be further suppressed. Furthermore, thixotropy is improved, sagging is further suppressed, viscosity is further reduced, and coating workability tends to be further improved. The specific surface area of ​​hydrophobic silica C measured by the BET method may also be measured in accordance with JIS Z8830.

[0068] The hydrophobic silica C content is not particularly limited, but is preferably 0.01 to 10% by mass, 0.01 to 1% by mass, 0.075 to 0.3% by mass, or 0.05 to 0.15% by mass relative to the total mass of the thermally conductive filler B. When the hydrophobic silica C content is within the above range, the increase in thermal resistance when exposed to high temperatures for a long period of time tends to be suppressed. Furthermore, aggregation during heat cycling tends to be suppressed, and hardness changes and bleeding tend to be suppressed. In addition, thixotropy is improved, sagging is suppressed, viscosity is reduced, and coating workability tends to be improved.

[0069] Examples of commercially available hydrophobic silica C products include the following: "AEROSIL R972", "AEROSIL R974", "AEROSIL R9200", "AEROSIL R976", "AEROSIL RX200", "AEROSIL R8200", "AEROSIL R202", "AEROSIL RY200S", "AEROSIL RY200", "AEROSIL RY200L", and "AEROSIL RY300" (all manufactured by Evonik, AEROSIL is a registered trademark).

[0070] 1.4. Other ingredients Other components may include surfactants, silane coupling agents, and addition reaction agents, as needed. Examples include catalysts.

[0071] 1.4.1. Surfactants The thermally conductive composition may contain a surfactant to improve the dispersibility of the thermally conductive filler. The surfactant is not particularly limited, but examples include cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants. These surfactants may be used individually or in combination of two or more.

[0072] 1.4.2. Silane coupling agents The thermally conductive composition may further contain a silane coupling agent. The inclusion of a silane coupling agent tends to further reduce viscosity, suppress hardness changes and bleeding. In addition, it also tends to further suppress dripping.

[0073] Silane coupling agents are not particularly limited, but examples include epoxysilanes such as γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; aminosilanes such as aminopropyltriethoxysilane, ureidopropyltriethoxysilane, and N-phenylaminopropyltrimethoxysilane; and hydrophobic silane compounds such as phenyltrimethoxysilane, methyltrimethoxysilane, octadecyltrimethoxysilane, and n-decyltrimethoxysilane.

[0074] Among these, hydrophobic silane compounds are more preferred. Using such silane coupling agents tends to further reduce viscosity and suppress changes in hardness. In addition, dripping also tends to be further suppressed.

[0075] The silane coupling agent content is preferably 0.1 to 5% by mass, and may be 0.2 to 2% by mass, relative to the total amount of thermally conductive filler. When the silane coupling agent content is within the above range, viscosity tends to decrease further, and hardness changes and bleeding tend to be further suppressed.

[0076] 1.4.3 Addition Reaction Catalysts The addition catalyst is not particularly limited as long as it catalyzes the addition reaction between vinyl-modified organopolysiloxane A21 and hydrosilyl-modified organopolysiloxane A22. Examples of addition catalysts include platinum compound catalysts, rhodium compound catalysts, and palladium compound catalysts. Among these, platinum compound catalysts are preferred. By using such an addition catalyst, the curing rate of the addition reaction tends to be within a suitable range.

[0077] The platinum compound catalyst is not particularly limited, but examples include elemental platinum, platinum compounds, and platinum-supported inorganic powders. The platinum compound is not particularly limited, but examples include chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordination compounds. The platinum-supported inorganic powder is not particularly limited, but examples include platinum-supported aluminum oxide powder, platinum-supported silica powder, and platinum-supported carbon powder.

[0078] The addition reaction catalyst may be used alone or in combination of two or more types. Furthermore, when preparing the thermally conductive composition, the addition reaction catalyst may be incorporated alone or pre-mixed with other components, such as vinyl-modified organopolysiloxane A21 or other organopolysiloxanes.

[0079] The content of the addition reaction catalyst is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, and even more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the total content of vinyl-modified organopolysiloxane A21 and hydrosilyl-modified organopolysiloxane A22. Having the content of the addition reaction catalyst within the above range tends to allow the curing rate of the addition reaction to be within a suitable range.

[0080] 1.5. Asker C hardness The Asker C hardness of the thermally conductive composition of this embodiment is not particularly limited, but is preferably 30 or less, 15 or less, 10 or less, 5 or less, 1 or less, or 0. An Asker C hardness of 30 or less tends to result in a thermally conductive composition with excellent handling properties. The Asker C hardness can be measured using an Asker C type tester (product name: Asker Rubber Hardness Tester Type C, manufactured by Polymer Instruments Co., Ltd.) at a test temperature of 25°C using a spring hardness test in accordance with SRIS0101.

[0081] The Asker C hardness of the thermally conductive composition of this embodiment after exposure to 150°C for 1000 hours is not particularly limited, but is preferably 60 or less, 50 or less, 40 or less, or 35 or less. The lower limit of the Asker C hardness after exposure to 150°C for 1000 hours is not particularly limited and may be 0. An Asker C hardness of 60 or less after exposure to 150°C for 1000 hours tends to further suppress the increase in thermal resistance when exposed to high temperatures for a long period of time.

[0082] 1.6.Viscosity The viscosity η1 of the thermal conductive composition of this embodiment under measurement conditions of 25°C and a shear rate of 1 / s is not particularly limited, but is preferably 500 to 5000 Pa·s, 1000 to 3000 Pa·s, 1500 to 2500 Pa·s, or 1800 to 2300 Pa·s. When the viscosity η1 is within the above range, handling and coating workability tend to be further improved.

[0083] The viscosity η10 of the thermal conductive composition of this embodiment under measurement conditions of 25°C and a shear rate of 10 / s is not particularly limited, but is preferably 100-1000 Pa·s, 200-800 Pa·s, 300-700 Pa·s, or 400-600 Pa·s. When the viscosity η10 is within the above range, handling and coating workability tend to be further improved.

[0084] The ratio (η1 / η10) of the viscosity η10 of the thermal conductive composition of this embodiment at 25°C and a shear rate of 1 / s to the viscosity η1 at 25°C and a shear rate of 10 / s is not particularly limited, but is preferably 2 to 10, 2 to 8, 3 to 6, or 3 to 5. When η1 / η10 is within the above range, coating workability tends to be further improved while suppressing dripping.

[0085] 1.7.Usage The thermally conductive composition of this embodiment can be suitably used as a thermally conductive heat dissipation material such as a thermally conductive grease or a thermally conductive sheet obtained by curing the composition.

[0086] 2.Cured product The cured product of this embodiment is a cured product of the thermally conductive composition described above. More specifically, the cured product (crosslinked cured product) is obtained by a reaction of a two-component organopolysiloxane with an addition reaction, a condensation reaction, or a peroxide.

[0087] Mixing equipment such as roll mills, kneaders, Banbury mixers, and line mixers can be used to mix the thermally conductive compositions. More specifically, methods such as kneading using a universal mixer, hybrid mixer, Trimix (manufactured by Inoue Seisakusho), or static mixer can be used. The doctor blade method is preferred for molding, but depending on the viscosity of the resin, extrusion, pressing, calendering roll, etc., may also be used. The reaction conditions for the addition reaction are not particularly limited, but are usually carried out at room temperature (e.g., 25°C) to 150°C for 0.1 to 24 hours.

[0088] 3.Electronic equipment The electronic device of this embodiment comprises an electronic component, a heat sink, and the thermally conductive composition, wherein the electronic component and the heat sink are in contact via the thermally conductive composition. In this electronic device, the electronic component and the heat sink are thermally bonded via the thermally conductive composition.

[0089] Here, the electronic components are not particularly limited, but examples include motors, battery packs, circuit boards used in automotive power supply systems, power transistors, microprocessors, and other heat-generating electronic components. Among these, electronic components used in automotive power supply systems are preferred. Furthermore, the heat sink is not particularly limited as long as it is a component configured for the purpose of heat dissipation or heat absorption.

[0090] The method for bonding electronic components and a heat sink via a thermally conductive composition is not particularly limited. For example, an electronic device may be obtained by bonding electronic components and a heat sink using a thermally conductive composition. [Examples]

[0091] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples. Unless otherwise specified, each operation was carried out at room temperature (25°C).

[0092] 1. Preparation of thermally conductive compositions (Example 1) A thermally conductive composition was prepared by mixing organopolysiloxane A, thermally conductive filler B, and hydrophobic silica C according to the composition shown in Table 1. In Table 1, the composition of each component is shown so that the total amount of organopolysiloxane A is 100 parts by weight.

[0093] (Comparative Example 1) A thermally conductive composition was prepared in the same manner as in Example 1, with the composition shown in Table 1, except that hydrophilic silica was used instead of hydrophobic silica C.

[0094] 1.1. Raw materials (Organopolysiloxane A) Aa: Organopolysiloxane, manufactured by Shin-Etsu Silicone Co., Ltd., KF-96-100CS, viscosity 100 mmHg 2 / s Ab: Organopolysiloxane, Momentive, SRH-32, weight-average molecular weight 500,000, content of constituent units including vinyl groups: 0.1 mol% (Thermal conductive filler B) Ba: Aluminum nitride: Manufactured by Toyo Aluminum Co., Ltd., TFZ-S100P, average particle size: 100 μm Bb: Aluminum oxide: Manufactured by Denka Co., Ltd., DAW45s, average particle size: 46 μm Bc: Aluminum oxide: Manufactured by Denka Co., Ltd., DAW05, average particle size: 6.4 μm Bd: Aluminum oxide: Sumitomo Chemical Co., Ltd., AA05, average particle size: 0.6 μm Be: Aluminum oxide: Manufactured by Denka Co., Ltd., ASFP40, average particle size: 0.4 μm (silica) Hydrophobic silica C: AEROSIL R202, manufactured by Evonik, carbon content: 3.5-5.0% by mass, specific surface area: 80-120 m² 2 / g Hydrophilic silica: AEROSIL 200, manufactured by Evonik, specific surface area: 175-225 m² 2 / g

[0095] The average particle size of each filler component was measured using a Shimadzu Corporation "SALD-20 Laser Diffraction Particle Size Distribution Analyzer". For the evaluation sample, 5g of each filler component to be measured was added to 50mL of pure water in a glass beaker, stirred with a spatula, and then dispersed in an ultrasonic cleaner for 10 minutes. The dispersed solution of each filler component was then added drop by drop to the sampler section of the analyzer using a dropper, and measurements were taken once the absorbance stabilized. The average particle size was measured using D50 (median diameter).

[0096] The carbon content of hydrophobic silica C, and the specific surface area of ​​hydrophobic silica C and hydrophilic silica are shown as catalog values. The carbon content may also be measured using a Sumika Analysis Center NC quantity analyzer (Sumigraph NC-22F), and the specific surface area by the BET method may be measured using a particle size distribution / particle shape analyzer (Microtrac-Bel, product name: SYNC) in accordance with JIS Z 8830.

[0097] 1.2. Asker C hardness For each thermally conductive composition obtained as described above, the Asker C hardness at 25°C was measured using an Asker C-type tester (product name: Asker Rubber Hardness Tester Type C, manufactured by Polymer Instruments Co., Ltd.) (indicated as "0h" in the table). The measurement results are shown in Table 1. In addition, the Asker C hardness after exposure testing in the mounting thermal resistance test described later was also measured (indicated as "300h" and "500h" in Table 1). Note that each thermally conductive composition was cooled to 25°C after the exposure test before the Asker C hardness was measured.

[0098] 1.3.Viscosity The viscosity of each thermally conductive composition obtained as described above was measured using a rotary rheometer "HANKE MARS III" (manufactured by Thermo Fisher Scientific) with a 35 mm diameter parallel plate, a gap of 0.5 mm, a temperature of 25°C, and a shear rate of 1 / s or 10 / s. The measurement results are shown in Table 1. The viscosity under the measurement condition of a shear rate of 1 / s is denoted as "viscosity η1," and the viscosity under the measurement condition of a shear rate of 10 / s is denoted as "viscosity η10."

[0099] 2. Evaluation 2.1. Thermal Resistance The mounted thermal resistance is measured on a measuring device with each thermal conductive composition at 800 mm². 2 The measurements were performed according to ASTM D5470, except that the values ​​were measured after molding the material to dimensions of 20mm x 40mm and a thickness of 1mm, and exposing it to a 150°C environment for a predetermined time. The exposure times at 150°C were set to 0, 300, 500, and 1000 hours, and the mounted thermal resistance was measured for each.

[0100] 2.2. Pump Out Pump-out tests were performed on each of the thermally conductive compositions obtained as described above using the following method. First, the thermally conductive composition was applied to an aluminum plate, and then sandwiched between glass plates so that the thermally conductive composition formed a circle with a diameter of 20 mm. Next, a thermal shock test was performed on the thermally conductive composition from -40°C to 150°C to evaluate its pump-out properties. Specifically, one cycle consisted of holding the composition in a -40°C environment for 30 minutes, raising the temperature from -40°C to 150°C, holding it in a 150°C environment for 30 minutes, and then lowering the temperature from 150°C to -40°C. This cycle was repeated 1000 times. The temperature rise and fall from -40°C to 150°C and from 150°C to -40°C were kept within 5 minutes. The diameter of the thermally conductive composition was measured before the thermal shock test and after the thermal shock test was performed for a predetermined time (500h, 1000h), and the difference is shown in Table 1.

[0101] [Table 1]

[0102] A comparison between Example 1 and Comparative Example 1 showed that the inclusion of organopolysiloxane A, thermally conductive filler B, and hydrophobic silica C suppressed the increase in thermal resistance when exposed to high temperatures for a long period of time, and also suppressed pump-out due to heat cycling. Furthermore, the viscosity values ​​(η1, η10, η1 / η10) of Example 1 and Comparative Example 1 showed that Example 1 had superior handling and coating workability.

[0103] Furthermore, thermally conductive compositions were prepared using 3450 parts by mass of only the thermally conductive fillers Ba, Bb, Bc, Bd, or Be in the compositions of Example 1 and Comparative Example 1, and their thermal resistances were compared. As a result, the initial thermal resistance was higher than that of Example 1 due to differences in aspects such as the packing properties of the thermally conductive filler B. However, the rate of increase in thermal resistance when maintained at high temperatures for a long period of time was lower for the thermally conductive composition containing hydrophobic silica C than for the thermally conductive composition without hydrophilic silica, and in this respect, the results were the same as those of Example 1 and Comparative Example 1. In addition, non-reactive organopolysiloxane A and thermally conductive filler B were stored individually at 150°C for a long period of time, but no significant changes were observed in their respective physical properties.

[0104] From the above, it was found that the increase in thermal resistance is due to hydrophilic silica, and that hydrophobic silica C contributes to suppressing the increase in thermal resistance. [Industrial applicability]

[0105] The thermally conductive composition of the present invention has industrial applicability as a thermally conductive composition used in which a heating element and a metal housing are thermally bonded.

Claims

1. Organopolysiloxane A and Thermally conductive filler B and, containing hydrophobic silica C, Thermally conductive composition.

2. The Asker C hardness is 30 or less. The thermally conductive composition according to claim 1.

3. The Asker C hardness after exposure to 150°C for 1000 hours is 60 or less. The thermally conductive composition according to claim 1.

4. The viscosity η1 under measurement conditions of 25°C and a shear rate of 1 / s is 500 to 5000 Pa·s. The thermally conductive composition according to claim 1.

5. The viscosity η10 under measurement conditions of 25°C and a shear rate of 10 / s is 100 to 1000 Pa·s. The thermally conductive composition according to claim 1.

6. The ratio of viscosity η1 at 25°C and a shear rate of 1 / s to viscosity η10 at 25°C and a shear rate of 1 / s (η1 / η10) is between 2 and 10. The thermally conductive composition according to claim 1.

7. The content of the hydrophobic silica C is 0.01 to 10% by mass relative to the total mass of the thermally conductive filler B. The thermally conductive composition according to claim 1.

8. The carbon content of the hydrophobic silica C is 0.1 to 10% by mass. The thermally conductive composition according to claim 1.

9. The specific surface area of ​​the hydrophobic silica C measured by the BET method is 10 to 500 m². 2 / g is The thermally conductive composition according to claim 1.

10. The thermally conductive filler B includes at least one selected from the group consisting of boron nitride, aluminum nitride, aluminum oxide, silicon nitride, silicon oxide, zinc oxide, silica, aluminum hydroxide, magnesium oxide, and carbon. The thermally conductive composition according to claim 1.

11. The aforementioned thermally conductive filler B is Thermally conductive filler B1 with an average particle size of 0.1 μm or more and less than 1.0 μm, Thermally conductive filler B2 with an average particle size of 1.0 μm or more and less than 30 μm, A thermally conductive filler B3 with an average particle size of 30 μm or more and 150 μm or less, The thermally conductive composition according to claim 1.

12. The invention comprises an electronic component, a thermally conductive composition according to any one of claims 1 to 11, and a heat sink. The electronic component and the heat sink are in contact via the thermally conductive composition. electronic equipment.

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