Thermally conductive silicone composition and method for producing the same

Abstract

This thermally conductive silicone composition contains: (A) an organopolysiloxane having a kinematic viscosity of 10-10,000 mm2 / s; (B) an organopolysiloxane having a kinematic viscosity of 10-100,000 mm2 / s; (C) an aluminum nitride powder which has an oxygen content of 0.5 mass% or less, a BET specific surface area of 1.0 m2 / g or less, an average particle diameter of 3-40 μm, and a proportion of coarse particles having particle diameters of 44-105 μm in a volume-based laser diffraction type particle size distribution of 10.0 mass% or less relative to component (C) as a whole; and (D) an irregularly shaped zinc oxide powder at a quantity whereby the blending ratio of component (C) and component (D) is 5.0:5.0 to 9.5:0.5 in terms of mass ratio and the total amount of powders of components (C) and (D) is 70-85 vol% of the composition as a whole. The thermally conductive silicone composition maintains fluidity, exhibits good handleability, exhibits excellent heat dissipation performance, and exhibits excellent durability and reliability under conditions of high temperature and conditions of high temperature and high humidity.

Description

Technical Field

[0001] The present invention relates to a thermally conductive silicone composition having excellent insulation and thermal conductivity, and a method for producing the same.

Background Art

[0002] Many electronic components generate heat during use. Therefore, in order to properly function the electronic components, it is necessary to remove heat from the electronic components. In particular, integrated circuit elements such as CPUs used in personal computers have an increasing amount of heat generation due to the increase in the operating frequency, and heat countermeasures have become an important issue.

[0003] Many methods have been proposed as means for removing this heat. Particularly for electronic components with a large amount of heat generation, a method has been proposed in which a thermally conductive material such as thermally conductive grease or a thermally conductive sheet is interposed between the electronic component and a member such as a heat sink to release heat. However, it has not been satisfactory for heat dissipation at locations where the specification thickness varies greatly (see Patent Document 1 and Patent Document 2).

[0004] In addition, as such a thermally conductive material, a composition based on silicone oil and containing zinc oxide or alumina powder is known, but the heat resistance at 200 °C has been unsatisfactory (see Patent Document 3 and Patent Document 4).

[0005] Furthermore, to improve thermal conductivity, Patent Document 1 discloses a thermal conductive material using aluminum nitride powder, comprising a liquid organosilicon carrier, silica fibers, and at least one selected from dendritic zinc oxide, flaky aluminum nitride, and flaky boron nitride. Patent Document 5 discloses a silicone grease composition obtained by blending spherical hexagonal aluminum nitride powder of a certain particle size range with a specific organopolysiloxane. Patent Document 6 discloses a thermal conductive silicone grease combining fine-particle aluminum nitride powder and coarse-particle aluminum nitride powder. Patent Document 7 discloses a thermal conductive silicone grease combining aluminum nitride powder and zinc oxide powder. Patent Document 8 discloses a thermal conductive grease composition using aluminum nitride powder surface-treated with organosilane, but all of these were unsatisfactory in terms of durability and reliability.

[0006] Patent Document 9 discloses a thermally conductive polysiloxane composition using amorphous aluminum nitride particles with an average particle size of 30 to 150 μm. However, the proportion of coarse particles is not specified, and using multiple types of aluminum nitride with a wide particle size distribution results in poor packing, making it insufficient for achieving high thermal conductivity, and the post-heat resistance properties are also unsatisfactory.

[0007] The thermal conductivity of aluminum nitride is 70-270 W / (m·K), while the thermal conductivity of diamond is higher, at 900-2,000 W / (m·K). Patent document 10 discloses a thermally conductive silicone composition containing silicone resin, diamond, zinc oxide, and a dispersant, but its post-heat resistance properties were particularly unsatisfactory.

[0008] Furthermore, metals are materials with high thermal conductivity and can be used in areas of electronic components where insulation is not required. Patent document 11 discloses a thermally conductive grease composition obtained by mixing metallic aluminum powder with a base oil such as silicone oil, but it was unsatisfactory because it lacked insulating properties.

[0009] Recently, all thermally conductive materials and thermally conductive greases have become insufficient to handle the heat generated by integrated circuit elements such as CPUs.

[0010] As can be seen from Maxwell and Blagemann's theoretical formulas, the thermal conductivity of a material obtained by compounding a thermally conductive filler with silicone oil is almost independent of the thermal conductivity of the thermally conductive filler when the volume fraction of the thermally conductive filler is 0.6 or less. Only when the volume fraction exceeds 0.6 does the thermal conductivity of the thermally conductive filler begin to be affected. In other words, to increase the thermal conductivity of thermally conductive grease, it is important to first fill it with a high amount of thermally conductive filler, and to use a filler with high thermal conductivity. However, high filling reduces the fluidity of the thermally conductive grease, which worsens workability such as application (dispensing, screen printing), making it impractical for use. Furthermore, the reduced fluidity prevents it from following the fine irregularities on the surface of electronic components and heat sinks, resulting in increased contact thermal resistance.

[0011] To date, studies have been conducted to incorporate alkoxy-group-containing organopolysiloxanes into thermal conductive materials to significantly improve dispersibility by treating the surface of the thermal conductive filler, with the aim of achieving high filler capacity and obtaining thermally conductive materials with good fluidity (see Patent Documents 12 and 13). However, these treatment agents have the drawback of degrading under high temperature and high humidity conditions through hydrolysis, etc., which induces deterioration of the performance of the thermal conductive material. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 56-28264 [Patent Document 2] Japanese Patent Application Laid-Open No. 61-157587 [Patent Document 3] Special Publication No. 52-33272 [Patent Document 4] Special Publication No. 59-52195 [Patent Document 5] Japanese Patent Application Publication No. 2-153995 [Patent Document 6] Japanese Patent Application Publication No. 3-14873 [Patent Document 7] Japanese Patent Application Publication No. 10-110179 [Patent Document 8] Japanese Patent Publication No. 2000-63872 [Patent Document 9] Patent No. 6246986 [Patent Document 10] Japanese Patent Publication No. 2002-30217 [Patent Document 11] Japanese Patent Publication No. 2000-63873 [Patent Document 12] Japanese Patent Publication No. 2004-262972 [Patent Document 13] Japanese Patent Publication No. 2005-162975 [Overview of the project] [Problems that the invention aims to solve]

[0013] The present invention has been made in view of the above circumstances, and aims to provide a thermally conductive silicone composition and a method for producing the same, which maintains fluidity and is easy to handle even when a high concentration of thermally conductive filler is used to impart excellent insulating and thermal conductivity, and which also has excellent heat dissipation performance and excellent durability and reliability under high temperature and high temperature and high humidity conditions. [Means for solving the problem]

[0014] The present inventors have discovered that by using specific amounts of (C) aluminum nitride powder and (D) amorphous zinc oxide powder, a thermally conductive silicone composition can be obtained that has insulating properties and high thermal conductivity, maintains excellent fluidity, is easy to handle, conforms to fine irregularities, reduces contact thermal resistance, and has excellent heat dissipation performance. Furthermore, it has been found that it has excellent durability under high temperature and high temperature and high humidity conditions, improving reliability during mounting, and thus the present invention was made.

[0015] Therefore, the present invention provides the following inventions. 1. (A) The following general formula (1)

Chemical formula

[0016] According to the present invention, it is possible to provide a thermally conductive silicone composition and a method for producing the same, which have insulating properties and high thermal conductivity, maintain excellent fluidity, are easy to handle, have excellent heat dissipation performance, have excellent durability under high temperature and high temperature and high humidity conditions, and have improved reliability during mounting. [Modes for carrying out the invention]

[0017] The present invention will be described in detail below. In this invention, the amount expressed as "parts by mass" and viscosity are values ​​at 25°C. In some cases, "thermal conductive silicone composition" may simply be referred to as "composition". [(A) component] (A) Component is given by the following general formula (1) [ka] (In the formula, R 1 R is an unsubstituted or substituted monovalent hydrocarbon group, 2 (where a is an integer between 5 and 100, and b is an integer between 1 and 3.) It is expressed as such, and the kinematic viscosity at 25°C is 10 to 10,000 mm². 2 / s organopolysiloxane It is.

[0018] The above R 1R is independently an unsubstituted or substituted monovalent hydrocarbon group, such as linear alkyl groups, branched alkyl groups, cyclic alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups. Examples of linear alkyl groups include methyl, ethyl, propyl, hexyl, and octyl groups. Examples of branched alkyl groups include isopropyl, isobutyl, tert-butyl, and 2-ethylhexyl groups. Examples of cyclic alkyl groups include cyclopentyl and cyclohexyl groups. Examples of alkenyl groups include vinyl and allyl groups. Examples of aryl groups include phenyl and tolyl groups. Examples of aralkyl groups include 2-phenylethyl and 2-methyl-2-phenylethyl groups. Examples of halogenated alkyl groups include 3,3,3-trifluoropropyl, 2-(nonafluorobutyl)ethyl, and 2-(heptadecafluorooctyl)ethyl groups. Among these, R 1 A methyl group or a phenyl group is preferred.

[0019] The above R 2 R is independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group. Examples of alkyl groups include R 1 Examples of linear alkyl groups, branched alkyl groups, and cyclic alkyl groups are similar to those exemplified above. Examples of alkoxyalkyl groups include methoxyethyl group and methoxypropyl group. Examples of alkenyl groups include R 1 Examples similar to those given for the above can be cited. Examples of acyl groups include the acetyl group and the octanoyl group. 2 Alkyl groups are preferred, and methyl and ethyl groups are more preferred.

[0020] a is an integer between 5 and 100, preferably between 5 and 50, and more preferably between 5 and 30. b is an integer between 1 and 3, preferably 3.

[0021] The kinematic viscosity of component (A) obtained at 25°C using an Ostwald viscometer was 10 to 10,000 mm².2 / s, 10~5,000mm 2 / s is preferable. Kinematic viscosity is 10 mm 2 If the kinematic viscosity is less than / s, oil bleeding is more likely to occur from the resulting thermally conductive silicone composition. On the other hand, if the kinematic viscosity is 10,000 mm 2 If the rate exceeds / s, the resulting thermally conductive silicone composition tends to have poor fluidity.

[0022] The amount of component (A) is 5 to 100 parts by mass, preferably 15 to 85 parts by mass, and more preferably 55 to 80 parts by mass, when the total amount of component (A) and component (B), described later, is 100 parts by mass. When the amount is within this range, the resulting thermally conductive silicone composition maintains good fluidity and workability, and it is easy to fill the composition with the thermally conductive fillers of components (C) and (D), described later. If the amount of component (A) is less than 5 parts by mass, it may not be possible to fill the thermally conductive silicone composition with the thermally conductive fillers of components (C) and (D).

[0023] (A) Suitable specific examples of component are listed below. Me is a methyl group (the same applies hereafter). [ka]

[0024] [(B) Component] Component (B) of the present invention has the following average composition formula (2): R 3 c SiO (4-c) / 2 (2) (In the formula, R 3 (These are independently unsubstituted or substituted monovalent hydrocarbon groups with 1 to 18 carbon atoms, where c is a number between 1.8 and 2.2.) The kinematic viscosity at 25°C, as shown by [formula], is 10 to 100,000 mm². 2It is an organopolysiloxane of / s. Component (B) is used as appropriate for the purpose of imparting properties such as viscosity modifiers and tackifiers to the thermally conductive silicone composition of the present invention, but is not limited thereto. Component (B) can be used alone or in combination of two or more types.

[0025] The above R 3 These are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms. R 3 Examples include alkyl groups such as methyl, ethyl, propyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl groups; and cyclopentyl and cyclohexyl groups. alkyl group Examples include alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl groups; and halogenated hydrocarbon groups such as 3,3,3-trifluoropropyl, 2-(perfluorobutyl)ethyl, 2-(perfluorooctyl)ethyl, and p-chlorophenyl groups, but methyl, phenyl, and alkyl groups having 6 to 18 carbon atoms are particularly preferred.

[0026] The above value c is a number between 1.8 and 2.2, and preferably between 1.9 and 2.1, from the viewpoint of the consistency required for the composition of the present invention as a thermally conductive silicone composition.

[0027] Furthermore, the kinematic viscosity of component (B) at 25°C is 10 to 100,000 mm². 2 / s, 10~10,000mm 2 A kinematic viscosity of 10 mm² is preferred. 2 If the kinematic viscosity is less than / s, liquid separation and oil bleeding are more likely to occur from the resulting thermally conductive silicone composition. On the other hand, if the kinematic viscosity is 100,000 mm² 2 When the fluidity exceeds 1 / s, the resulting thermally conductive silicone composition becomes less fluid, leading to problems with workability.

[0028] (B) Specific examples of component include, for example, [ka] These are some examples.

[0029] The amount of component (B) is in the range of 0 to 95 parts by mass when the total amount of components (A) and (B) is 100 parts by mass, meaning that the composition does not contain any component (B). The amount is preferably 15 to 85 parts by mass, and more preferably 20 to 45 parts by mass. When the amount is within this range, the composition is likely to maintain good fluidity and workability, and it is also easy to fill the composition with the thermally conductive fillers of components (C) and (D), which will be described later. If the amount of component (B) exceeds 95 parts by mass, it may not be possible to fill the composition with the thermally conductive fillers of components (C) and (D).

[0030] [(C) component] Component (C) of the present invention has an oxygen content of 0.5% by mass or less and a BET specific surface area of ​​1.0 m². 2 The aluminum nitride powder has a particle size of 3 to 40 μm, a particle size of 3 to 40 μm, and a volume-based laser diffraction particle size distribution in which the proportion of coarse particles of 44 to 105 μm is 10.0 mass% or less of the total (C) component. The (C) component can be used alone or in combination of two or more types.

[0031] The oxygen content of component (C) is 0.5% by mass or less, preferably 0.2% by mass or less. The lower limit is not particularly limited and may be 0.01% by mass or even 0% by mass. If the oxygen content of component (C), which is an indicator of the nitridation rate, exceeds 0.5% by mass, the crystallite size decreases, the chemical purity of component (C) deteriorates, and the thermal conductivity of the composition decreases, potentially leading to poor thermal properties after humidity resistance. The oxygen content of component (C) can be measured using an oxygen-nitrogen analyzer and analyzed by comparison with silicon nitride in standard samples. Examples of oxygen-nitrogen analyzers include: Horiba You can use the "EMGA-920" manufactured by the manufacturer, etc.

[0032] (C) The BET specific surface area (nitrogen gas adsorption method) of component C is preferably 1.0 m², from the viewpoint of increasing the thermal conductivity of the composition. 2It is less than or equal to / g, and 0.9 m 2 / g The following is more preferable. There is no particular limit on the lower limit of the BET specific surface area, but based on the upper limit of the average particle diameter defined in component (C) and the defined proportion of coarse particles, 0.05 m 2 It may also be expressed as / g. The BET specific surface area of ​​component (C) can be analyzed, for example, using Mountec's "Macsorb(registered trademark) HM Model-1201".

[0033] The average particle size of component (C) according to the laser diffraction particle size distribution (volume basis) is preferably 3 to 40 μm, and more preferably 4 to 40 μm. If the average particle size is less than 3 μm, the packing ability into the resin will be poor, and the viscosity may become significantly higher. On the other hand, if the average particle size exceeds 40 μm, it is preferable from the viewpoint of increasing the thermal conductivity of the composition, but oil separation may easily proceed over time. Furthermore, the proportion of coarse particles between 44 and 105 μm in the volume-based laser diffraction particle size distribution is 10.0 mass% or less of the total (C) component, and more preferably 8.0 mass% or less. If the proportion of coarse particles between 44 and 105 μm is 10.0 mass% or less of the total (C) component, the desired thermal resistance and high thermal conductivity can be achieved simultaneously. There is no particular lower limit for the proportion of coarse particles between 44 and 105 μm in the laser diffraction particle size distribution, but it can be around 0.01 mass%. On the other hand, if the proportion of coarse particles between 44 and 105 μm exceeds 10.0% of the total, the thickness may not be 44 to 105 μm, and the desired thermal resistance tends not to be achieved.

[0034] (C) Component is not particularly limited, but can be obtained by reduction nitriding, direct nitriding, etc., as long as it satisfies the requirements of the present invention. In particular, from the viewpoint of being able to more easily obtain a material with an oxygen content of 0.5% by mass or less, it is preferable to obtain it by direct nitriding. If obtained by direct nitriding, the chemical purity is improved, which further improves the thermal properties after moisture resistance.

[0035] The method for producing component (C) is not particularly limited and may be carried out according to known direct nitriding methods (including combustion synthesis methods). For example, one method is to nitride metallic aluminum powder alone in a nitrogen atmosphere of 0.2 to 3 MPa. If necessary, it may also be crushed, and the crushing method may be carried out according to known methods such as ball mills, jet mills, and crushers.

[0036] Furthermore, a method is proposed in which the (C) component obtained by direct nitriding is heat-treated at 1,600 to 2,000°C in a non-oxidizing atmosphere. This process eliminates the corners of angular, irregularly shaped particles, resulting in rounded particles, which is suitable for reducing the viscosity of the composition. However, if the temperature is below 1,600°C, the particles are less likely to become rounded, and if the temperature exceeds 2,000°C, the (C) components may sinter together, resulting in an average particle size that is not achieved as desired.

[0037] The shape of component (C) is not particularly limited, even if it is spherical, polyhedral, or irregular in shape, as long as it does not impair the present invention. In particular, a rounded shape is preferred because it lowers the initial viscosity of the composition, reduces viscosity change even after treatment at 200°C, and further improves heat resistance. In this invention, "rounded shape" refers to a shape with an aspect ratio of 2.0 or less.

[0038] [(D) component] Component (D) is an amorphous zinc oxide powder having an average particle size of 0.01 to less than 3.0 μm, and the proportion of coarse particles of 25 to 45 μm according to the sieve particle size is 0.2% by mass or less of the total component (D). It can be used alone or in combination of two or more components. Component (D) functions as a thermally conductive filler in the thermally conductive silicone composition of the present invention.

[0039] The average particle size of component (D) is 0.01 or more and less than 3.0 μm, preferably 0.01 to 2.0 μm. When the average particle size of component (D) is within this range, the bulk density of component (D) tends to be high and the specific surface area tends to be low, thus the thermally conductive silica of the present invention N groupThe compound (D) is easily packed into the finished product. However, if the average particle size is smaller than 0.01 μm, the packing into the resin will be poor, and the viscosity may become significantly higher. On the other hand, if the average particle size is too large, such as 3.0 μm or more, oil separation may easily occur.

[0040] Component (D) can achieve both the desired thermal resistance and high thermal conductivity if the proportion of coarse particles in the sieve particle size range of 25-45 μm is 0.2 mass% or less of the total. There is no particular lower limit on the proportion of coarse particles in the sieve particle size range of 25-45 μm, but it is usually sufficient to set it at around 0.01 mass%. On the other hand, if the proportion of coarse particles in the 25-45 μm range exceeds 0.2 mass% of the total, the thickness may not be 25-45 μm, and the desired thermal resistance tends not to be achieved.

[0041] The purity of component (D) is preferably 99.5% by mass or higher, and particularly preferably 99.8% by mass or higher from the viewpoint of impurities such as Pb and Cd.

[0042] While an irregular shape is preferred for component (D), it is not particularly limited to spherical, rounded, rod-shaped, needle-shaped, or disc-shaped components, as long as they do not impair the present invention.

[0043] The mixing ratio of component (C) to component (D) is 5.0:5.0 to 9.5:0.5 by mass ratio, with 6.0:4.0 to 9.0:1.0 being preferable. If the proportion of component (C) is less than 5.0, the filler tends to fill poorly. On the other hand, if the proportion of component (C) exceeds 9.5, the filler becomes difficult to pack densely, and the thermal conductivity tends to decrease.

[0044] The total content of components (C) and (D) in the composition of the present invention is 70 to 85% by volume, preferably 70 to 83% by volume. If this content is less than 70% by volume, the thermal conductivity of the silicone composition may be insufficient, and if it exceeds 85% by volume, it becomes difficult to fill with the thermally conductive fillers, which are components (C) and (D).

[0045] In this invention, the average particle size of components (C) and (D) is determined by measuring the volume distribution of the particles using Microtrac (laser diffraction scattering method), multiplying the measured particle size by the relative particle amount (difference %), and dividing by the sum of the relative particle amounts (100%). Specifically, it can be measured on a volume basis using the Shimadzu Corporation "Laser Diffraction Particle Size Distribution Analyzer SALD-2300". For the evaluation sample, 5g of the thermal conductive powder to be measured was added to 50cc of pure water in a glass beaker, stirred with a spatula, and then dispersed in an ultrasonic cleaner for 10 minutes. The dispersed thermal conductive material powder solution was added drop by drop to the sampler section of the analyzer using a dropper, and the absorbance was allowed to stabilize until it could be measured. The measurement was performed when the absorbance stabilized. The laser diffraction particle size distribution analyzer calculates the particle size distribution from the data of the light intensity distribution of the diffracted / scattered light from the particles detected by the sensor. The average particle size is calculated by multiplying the measured particle size by the relative particle amount (difference %) and dividing by the sum of the relative particle amounts (100%). Note that the average particle size is the average diameter of the particles. Furthermore, the proportion of coarse particles between 44 and 105 μm in component (C) can be easily confirmed from the overall particle size distribution.

[0046] [(E) component] The composition of the present invention may further contain, as component (E), a volatile solvent that disperses or dissolves components (A) and (B). If the composition of the present invention further contains, in addition to components (A) and (B), component (F), as described later, it is preferable that the volatile solvent can also disperse or dissolve component (F). Component (E) may be any solvent as long as it can dissolve or disperse components (A) and (B), and optionally component (F). Component (E) may be used alone or in combination of two or more.

[0047] The thermal conductivity of a thermally conductive silicone composition is basically correlated with the filling rate of the thermally conductive filler; therefore, the more thermally conductive filler is added, the higher the thermal conductivity. However, naturally, increasing the amount of thermally conductive filler tends to increase the viscosity of the thermally conductive silicone composition itself, and the dilatancy of the composition when shear action is applied also tends to increase. In particular, in screen printing, when squeegeeing a thermally conductive silicone composition, if dilatancy is strongly expressed in the thermally conductive silicone composition, the fluidity of the thermally conductive silicone composition is temporarily strongly suppressed, which can prevent the thermally conductive silicone composition from passing through the screen mask and screen mesh, resulting in extremely poor coating performance. Thus, conventionally, it has been difficult to easily and uniformly apply a thin layer of a highly thermally conductive silicone composition with a high concentration of thermally conductive filler to a heat sink or the like using screen printing. The thermally conductive silicone composition of the present invention, even when containing thermally conductive fillers (C) and (D) at a high filling rate, tends to have a rapid decrease in viscosity and less dilatancy when it contains a volatile solvent (E), resulting in good coatability and easy application to heat sinks and the like by screen printing. After application, the contained (E) can be easily evaporated at room temperature or by actively heating. Therefore, the present invention makes it possible to easily and uniformly install a high thermally conductive silicone composition with a high filling rate of thermally conductive filler into heat sinks and the like in a thin layer by screen printing.

[0048] The boiling point of component (E) is preferably in the range of 80 to 260°C. When the boiling point is within this range, it is easier to prevent component (E) from rapidly volatilizing from the composition during the coating process, thereby suppressing an increase in the viscosity of the composition and ensuring sufficient coatability. Furthermore, since component (E) is less likely to remain in the composition after the coating process, the heat dissipation characteristics tend to improve.

[0049] Specific examples of component (E) include toluene, xylene, acetone, methyl ethyl ketone, cyclohexane, n-hexane, n-heptane, butanol, isopropanol (IPA), isoparaffinic solvents, etc. Among these, isoparaffinic solvents are preferred from the viewpoint of safety, health, and workability, and isoparaffinic solvents with a boiling point of 80 to 260°C are particularly preferred.

[0050] When component (E) is incorporated into the composition of the present invention, the amount is preferably 100 parts by mass or less, and more preferably 75 parts by mass or less, per 100 parts by mass of components (A) and (B). When the amount is within this range, it is easier to suppress the rapid settling of components (C) and (D), thereby improving the shelf life of the composition.

[0051] [(F) component] Component (F) is given by the following general formula (3): R 4 d R 5 e Si(OR 6 ) 4-d-e (3) (In the formula, R 4 R is an alkyl group having 9 to 15 carbon atoms, 5 R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, 6 (where d is an alkyl group having 1 to 6 carbon atoms, d is an integer from 1 to 3, e is an integer from 0 to 2, and d+e is an integer from 1 to 3.) This is an alkoxysilane represented by [formula].

[0052] Component (F) is both a wetter component and an additive that prevents deterioration of component (A) under high temperature and high humidity conditions. By treating the surface of the thermally conductive fillers of components (C) and (D) with component (F), the wettability of component (A) with components (C) and (D) can be further improved. As a result, component (F) assists in increasing the filler density of components (C) and (D). Furthermore, when used in combination with component (A), component (F) works to suppress contact between water vapor and component (A) under high temperature and high humidity conditions. As a result, component (F) prevents deterioration of the performance of the thermally conductive silicone composition of the present invention due to deterioration of component (A) caused by hydrolysis or other factors under high temperature and high humidity conditions. Component (F) can be used alone or in combination of two or more types.

[0053] The above R 4 The C1 is an alkyl group having 9 to 15 carbon atoms, and specific examples include nonyl, decyl, dodecyl, tetradecyl, and pentadecyl groups, with decyl groups being particularly preferred. If the number of carbon atoms is less than 9, the wettability with the thermally conductive filler (components (C) and (D)) tends to be insufficient, and if it exceeds 15, component (F) tends to solidify at room temperature, making it inconvenient to handle, and the heat resistance and flame retardancy of the resulting composition tend to decrease.

[0054] The above R 5 The group is independently an unsubstituted or substituted saturated or unsaturated monovalent hydrocarbon group having 1 to 8 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, hexyl, and octyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl groups; and halogenated hydrocarbon groups such as 3,3,3-trifluoropropyl, 2-(nonafluorobutyl)ethyl, and p-chlorophenyl groups, with methyl, ethyl, and vinyl groups being particularly preferred.

[0055] The above R 6The group is independently an alkyl group having 1 to 6 carbon atoms, and specific examples include methyl, ethyl, propyl, butyl, pentyl, and hexyl groups, with methyl and ethyl groups being particularly preferred.

[0056] The above d is usually an integer between 1 and 3, but is particularly preferably 1. The above e is an integer between 0 and 2, where d + e is an integer between 1 and 3.

[0057] Specific examples of component (F) include the following: C 10 H 21 Si(OCH3)3, C 12 H 25 Si(OCH3)3, C 12 H 25 Si(OC2H5)3, C 10 H 21 Si(CH3)(OCH3)2, C 10 H 21 Si(C6H5)(OCH3)2, C 10 H 21 Si(CH3)(OC2H5)2, C 10 H 21 Si(CH=CH2)(OCH3)2, C 10 H 21 Si(CH2CH2CF3)(OCH3)2

[0058] The amount of component (F) is preferably 0.1 to 50 parts by mass, and more preferably 1 to 20 parts by mass, relative to 100 parts by mass of the total of components (A) and (B). When the amount is within this range, the wetter effect and high temperature and high humidity resistance effect tend to increase in proportion to the amount added, making it economical. On the other hand, since component (F) is somewhat volatile, if a thermally conductive silicone composition containing component (F) is left in an open system, component (F) may evaporate from the composition, causing it to gradually harden. However, when the amount added is within this range, this phenomenon is less likely to occur.

[0059] [Other additives] The composition of the present invention may further contain commonly used additives or fillers as optional components, to the extent that they do not impair the objectives of the present invention. Specifically, fluorine-modified silicone surfactants; carbon black, titanium dioxide, red iron oxide, etc. as colorants; platinum catalysts, metal oxides such as iron oxide, titanium dioxide, cerium oxide, or metal hydroxides may be added as flame retardants. Furthermore, fine silica powder such as settling silica or calcined silica, thixotropic enhancers, etc., may be added as anti-settling agents for the thermally conductive filler at high temperatures. When such optional components are incorporated, the amount can be 1% by mass or less of the thermally conductive silicone composition, and preferably 0.5% by mass or less.

[0060] [Manufacturing method] The composition of the present invention is prepared by mixing components (A) to (D), and any of the above optional components. Mixing equipment includes dough mixers (kneaders), gate mixers, and planetary mixers. It offers significantly improved thermal conductivity, good workability, durability, and reliability.

[0061] [Thermally conductive silicone composition] [Thermal conductivity] The composition of the present invention has a thermal conductivity of 4.0 to 9.2 W / m·K at 25°C in the hot disk method compliant with ISO 22007-2, and 5.0 to 9.2 W / m·K This is preferable. According to the composition of the present invention, such thermal conductivity can be obtained. For example, the thermal conductivity of the composition in the present invention can be measured using a product called "TPS 2500 S" manufactured by Kyoto Electronics Corporation.

[0062] [viscosity] Furthermore, the viscosity of the composition of the present invention at 25°C is preferably 5 to 800 Pa·s, and more preferably 5 to 500 Pa·s, when measured at 10 rpm using a spiral viscometer with rotor A. When the viscosity is within this range, the resulting composition tends to have good fluidity, which improves workability such as dispensability and screen printability, and makes it easier to apply the composition thinly to a substrate. After thermal degradation at 200°C for 100 hours, the viscosity at 25°C is preferably 1,000 Pa·s or less, more preferably 800 Pa·s or less, and even more preferably 400 Pa·s or less, when measured at 10 rpm using a spiral viscometer. It is preferable that the composition be in such a non-curing liquid state. For viscosity measurement, a spiral viscometer with rotor A at 10 rpm is used. As an apparatus, for example, a spiral viscometer with the product name "Type PC-10AA" manufactured by Malcolm Corporation can be used for measurement.

[0063] [Thermal resistance] The composition of the present invention, after being left for 96 hours in a 130°C / 85%RH atmosphere, has a thermal resistance of 15 mm at 25°C, as measured by the laser flash method. 2 • Preferably less than kW, and 12mm 2 • Preferably less than kW. When the thermal resistance is within this range, the composition of the present invention can efficiently dissipate the heat generated from a heat-generating element to a heat-dissipating component, even when applied to such a element. The thermal resistance can be measured by the laser flash method in accordance with ASTM E 1461.

[0064] [Volume resistivity] The volume resistivity of the composition of the present invention is 10 9 Preferably Ω·cm or more, 10 10 A value of Ω·cm or greater is preferable. The upper limit is not particularly limited, but 10 16 The resistivity can be less than or equal to Ω·cm. Volume resistivity can be calculated in accordance with JIS K 6911. Details are provided in the examples.

[0065] [Uses of the composition] The thermally conductive silicone composition of the present invention is applied to heat-generating elements and heat sinks. Examples of heat-generating elements include general power supplies; electronic devices such as power transistors, power modules, thermistors, thermocouples, and temperature sensors; and heat-generating electronic components such as integrated circuit elements like LSIs and CPUs. Examples of heat sinks include heat dissipation components such as heat spreaders and heat sinks; and heat pipes and heat sink plates. Application can be carried out, for example, by screen printing. Screen printing can be carried out, for example, using a metal mask or screen mesh. By applying the composition of the present invention interposed between the heat-generating element and the heat sink, heat can be efficiently conducted from the heat-generating element to the heat sink, thereby effectively removing heat from the heat-generating element.

[0066] The thermally conductive silicone composition of the present invention possesses excellent thermal conductivity while maintaining insulating properties, and its excellent fluidity makes it easy to work with. Furthermore, it exhibits excellent adhesion to heat-generating electronic components and heat-dissipating components. By interposing the thermally conductive silicone composition of the present invention between heat-generating electronic components and heat-dissipating components, heat generated from the heat-generating electronic components can be efficiently dissipated to the heat-dissipating components. Moreover, the thermally conductive silicone composition of the present invention exhibits excellent durability under high temperature and high temperature and high humidity conditions. For example, when used for heat dissipation in general power supplies and electronic devices, or for heat dissipation of integrated circuit elements such as LSIs and CPUs used in electronic devices such as personal computers and digital video disc drives, it can provide extremely good reliability. The thermally conductive silicone composition of the present invention can significantly improve the stability and lifespan of heat-generating electronic components and electronic devices using them. [Examples]

[0067] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, unless otherwise specified, "%" in the composition indicates mass%, and ratios indicate mass ratios. The amounts of each component in the table are the amounts converted to pure content.

[0068] The components used in the composition of the present invention are as follows: (A) Organopolysiloxane having an alkoxy group bonded to a silicon atom A-1: The kinematic viscosity expressed by the following formula is 35 mm 2 / s organopolysiloxane [ka] (B) Organopolysiloxane B-1: The kinematic viscosity expressed by the following formula is 500 mm². 2 / s organopolysiloxane [ka] (C) Aluminum Nitride Powder

[0069] [Table 1]

[0070] The average particle diameters shown in Table 1 were calculated from the entire particle size distribution obtained by the laser diffraction particle size distribution method described above for the average particle diameters of components (C) and (D) in the present invention. The coarse particle content is the proportion of coarse particles between 44 and 105 μm to the entire particle size distribution obtained by the laser diffraction particle size distribution method. The rounded component (C) was obtained by heat-treating component (C) obtained by direct nitriding at 1,750°C in a non-oxidizing atmosphere.

[0071] (D) Zinc oxide powder (average particle size 0.27 μm, coarse particle content 0.0% in the fraction after sieving with a mesh size of 45 μm as specified in JIS Z 8801-1) The average particle size shown here was calculated from the entire particle size distribution obtained by laser diffraction particle size distribution. Similarly, the coarse particle content is based on sieve particle size, and the same applies to the proportion of coarse particles between 25 and 45 μm in the overall particle size distribution obtained by laser diffraction particle size distribution.

[0072] (E) A volatile solvent capable of dispersing or dissolving components A-1, B-1, and F-1 E-1: Isosol (registered trademark) 400 (trade name, isoparaffin solvent, boiling point: 210-254℃, manufactured by Nippon Petrochemical Co., Ltd.) (F) Alkoxysilane F-1: Alkoxysilane represented by the following formula C 10 H 21 Si(OCH3)3

[0073] [Examples, Comparative Examples] [Manufacturing method] The compositions of the examples and comparative examples were obtained by mixing components (A) to (F) as follows. Specifically, components (A) to (D) were weighed into a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) in the composition ratios (parts by mass) shown in Tables 2 and 3, and mixed under reduced pressure at 150°C for 1 hour at a pressure of 30 mmHg or less. After that, the resulting mixture was cooled and mixed to room temperature. When components (E) and (F) were added, they were added to the cooled mixture in the amounts shown in Tables 2 and 3 and mixed until homogeneous. The properties of the obtained compositions were measured by the following test methods. The results are shown in Tables 2 and 3.

[0074] [Viscosity measurement] The obtained composition was left in a constant temperature room at 25°C for 24 hours, and then the viscosity was measured using a viscometer (product name: Spiral Viscometer PC-10AA, manufactured by Malcolm Corporation) with an A-type rotor at a rotation speed of 10 rpm.

[0075] [Viscosity measurement after thermal degradation] The obtained composition was subjected to thermal degradation using a drying oven at 200°C for 100 hours, then left in a constant temperature room at 25°C for 24 hours, and measured in the same manner as above.

[0076] [Thermal conductivity measurement] Two samples of the obtained composition were prepared, each wrapped in kitchen plastic wrap to prevent bubbles from entering. The thermal conductivity of the composition at 25°C was measured by placing these samples between the sensors of a thermal conductivity meter (product name: TPS-2500S) manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0077] [Preparation of test specimens for measuring thickness and thermal resistance] A test specimen was prepared by sandwiching a 75 μm thick composition between two circular aluminum plates, each with a diameter of 12.6 mm and a thickness of 1 mm, and applying a pressure of 0.15 MPa at 25°C for 60 minutes.

[0078] [Thickness measurement] The thickness of the test specimen was measured using a micrometer (manufactured by Mitutoyo Corporation), and the thickness of the composition was calculated by subtracting the thickness of two aluminum plates that had been measured in advance.

[0079] [Measurement of thermal resistance] Using the above test specimens, the thermal resistance of the composition (unit: mm) was determined. 2 The thermal resistance (K / W) was measured at 25°C using a laser flash-based thermal resistance analyzer (Netch Corporation, xenon flash analyzer; LFA447 NanoFlash).

[0080] [Measurement of thermal resistance after being left in high temperature and high humidity conditions] Thermal resistance measurement rear The above test specimens were left in a 130°C / 85%RH atmosphere for 96 hours, and then the thermal resistance of the composition was measured again (unit: mm). 2 The thermal resistance (K / W) was measured at 25°C using the thermal resistance meter described above.

[0081] [Measurement of volume resistivity] Based on JIS K 6911, a test specimen was prepared with a sample thickness of 1.0 mm for measurement using the double-ring electrode method. 500 V was applied between the electrodes, and the volume resistivity was measured after 1 minute.

[0082] [Table 2]

[0083] [Table 3]

Claims

1. (A) General formula (1) 【Chemistry 1】 (In the formula, R 1 R is independently an unsubstituted or substituted monovalent hydrocarbon group. 2 (where a is independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, a is an integer from 5 to 100, and b is an integer from 1 to 3.) It is expressed as such, and the kinematic viscosity at 25°C is 10 to 10,000 mm². 2 / s organopolysiloxane: 5 to 100 parts by mass, (B) The following average empirical formula (2): R 3 c SiO (4-c) / 2 (2) (In the formula, R 3 (Each is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, where c is a number between 1.8 and 2.2.) It is expressed as such, and the kinematic viscosity at 25°C is 10 to 100,000 mm². 2 / s organopolysiloxane: 0 to 95 parts by mass (however, the total amount of component (A) and component (B) is 100 parts by mass). (C) having an oxygen content of 0.5% by mass or less, a BET specific surface area of 1.0 m 2 / g or less, an average particle diameter of 3 to 40 μm, and a proportion of coarse particles of 44 to 105 μm in the volume-based laser diffraction particle size distribution of 10.0% by mass or less of the entire component (C), aluminum nitride powder, (D) Irregularly shaped zinc oxide powder having an average particle size of 0.01 or more and less than 3.0 μm, and the proportion of coarse particles of 25 to 45 μm according to sieving particle size is 0.2% by mass or less of the total (D) component: The mixing ratio of component (C) and component (D) is 5.0:5.0 to 9.5:0.5 by mass ratio, and the total amount of powder of (C) and (D) is 70 to 85% by volume of the total composition. A thermally conductive silicone composition containing, This thermally conductive silicone composition has a thermal conductivity of 4.0 to 9.2 W / m·K in the hot disk method according to ISO 22007-2, a viscosity at 25°C of 5 to 800 Pa·s when measured at a rotation speed of 10 rpm using a spiral viscometer with rotor A, and a thermal resistance at 25°C measured by the laser flash method after being left for 96 hours in a 130°C / 85% RH atmosphere of 15 mm²·K / W or less.

2. The thermally conductive silicone composition according to claim 1, wherein the shape of component (C) is rounded aluminum nitride powder.

3. Furthermore, the thermally conductive silicone composition according to claim 1 contains a volatile solvent for dispersing or dissolving components (E), (A), and (B): 100 parts by mass or less per 100 parts by mass of the total amount of components (A) and (B).

4. Furthermore, (F) General formula (3) R 4 d R 5 e Si(OR 6 ) 4-d-e (3) (In the formula, R 4 R is an alkyl group having 9 to 15 carbon atoms, 5 R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, 6 (where d is an alkyl group having 1 to 6 carbon atoms, d is an integer from 1 to 3, and e is an integer from 0 to 2, where d + e is an integer from 1 to 3.) Alkoxysilane represented by: 0.1 to 50 parts by mass, The thermally conductive silicone composition according to claim 1, wherein components (C) and (D) are surface-treated.

5. The thermally conductive silicone composition according to claim 1, wherein, after thermal degradation at 200°C for 100 hours, the viscosity at 25°C is 1,000 Pa·s or less when measured by a spiral viscometer at a rotation speed of 10 rpm.

6. Volume resistivity is 10 9 A thermally conductive silicone composition according to claim 1, wherein the thermal conductivity is Ω·cm or greater.

7. A method for producing the thermally conductive silicone composition according to any one of claims 1 to 6, comprising the step of mixing the above components (A) to (D).

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