WO2022044723A1 - Thermally conductive composition and thermally conductive sheet using same - Google Patents

Abstract

Provided are: a thermally conductive composition from which a thermally conductive sheet having satisfactory thermal conductivity and flexibility can be formed; and a thermally conductive sheet produced using the thermally conductive composition. This thermally conductive composition comprises an organopolysiloxane, a thermally conductive filler, an alkoxy silane compound and a siloxane-modified acrylic resin, in which, when the content of the organopolysiloxane is defined as 100 parts by mass, the total content of the alkoxy silane compound and the siloxane-modified acrylic resin is 100 parts by mass or more. The thermally conductive sheet comprises a cured product of the thermally conductive composition.

Description

A heat conductive composition and a heat conductive sheet using the same

This technology relates to a heat conductive composition and a heat conductive sheet using the same. This application claims priority on the basis of Japanese Patent Application No. 2020-142900 filed on August 26, 2020 in Japan, and this application is referred to in this application. It will be used.

In recent years, with the increase in power density of semiconductor devices, the materials used for the devices are required to have higher heat dissipation characteristics. In order to realize such heat dissipation characteristics, a material called a thermal interface material, which relaxes the thermal resistance of the path through which heat generated from a semiconductor element is released to a heat sink, a housing, or the like, is in the form of a sheet, gel, or the like. It is used in various forms such as grease.

In general, examples of the thermal interface material include a composite material (heat conductive composition) in which a heat conductive filler is dispersed in an epoxy resin or a silicone resin. As the heat conductive filler, metal oxides and metal nitrides are often used. Further, silicone resin, which is an example of resin, is widely used from the viewpoint of heat resistance and flexibility.

In recent years, due to high-density mounting of semiconductor devices and the increase in heat generation, high thermal conductivity is required for thermal conductivity sheets. To solve this problem, for example, it is conceivable to increase the amount of the heat conductive filler added to the heat conductive composition.

However, if the amount of the heat conductive filler added to the heat conductive composition is increased, the flexibility of the obtained heat conductive sheet tends to decrease. When a heat conductive sheet having such reduced flexibility is sandwiched between a semiconductor element and a heat sink, for example, the stress applied to the semiconductor element having a relatively weak strength is large, and an unreasonable force is applied to the semiconductor element. become. Further, in the case of a semiconductor element mounted on a substrate, the stress applied to the substrate also increases, the stress on the substrate increases, and the substrate may bend. There is a concern that the semiconductor element mounted on the substrate may be peeled off due to such bending of the substrate.

In addition, the heat conductive sheet is usually sandwiched between the heat generating member and the heat radiating member by applying a load. However, if the heat generating member or the heat radiating member has a concave portion or a convex portion, the surface of the heat conductive sheet may not sufficiently contact the concave portion or the convex portion of the heat generating member or the heat radiating member. As described above, if a heat conductive sheet having poor followability (flexibility) to the contacting member is used, there is a concern that the heat conductivity of the heat conductive sheet may be lowered.

International Publication No. 2018/131486

This technique has been proposed in view of such conventional circumstances, and is a heat conductive composition capable of forming a heat conductive sheet having good heat conductivity and flexibility, and a heat conductive sheet using the same. The purpose is to provide.

As a result of diligent studies by the present inventor, a predetermined acrylic-silicone copolymer is contained in a heat conductive composition containing an organopolysiloxane, a heat conductive filler, and an alkoxysilane compound, and an alkoxy is obtained with respect to the organopolysiloxane. It has been found that the above-mentioned problems can be solved by setting the total content of the silane compound and the siloxane-modified acrylic resin to a predetermined value or more.

The thermally conductive composition according to the present technology contains an organopolysiloxane, a thermally conductive filler, an alkoxysilane compound, and a siloxane-modified acrylic resin, and the content of the organopolysiloxane is 100 parts by mass. , The total content of the alkoxysilane compound and the siloxane-modified acrylic resin is 100 parts by mass or more.

The heat conductive sheet according to the present technology is made of a cured product of the above heat conductive composition.

According to this technology, it is possible to provide a heat conductive sheet having good heat conductivity and flexibility.

FIG. 1 is a cross-sectional view showing an example of a heat conductive sheet. FIG. 2 is a cross-sectional view showing an example of a semiconductor device.

<Thermal conductive composition>
The thermally conductive composition according to the present technology contains an organopolysiloxane, a thermally conductive filler, an alkoxysilane compound, and a siloxane-modified acrylic resin. Further, in the heat conductive composition, when the content of organopolysiloxane is 100 parts by mass, the total content of the alkoxysilane compound and the siloxane-modified acrylic resin is 100 parts by mass or more, and 200 parts by mass or more. It may be 300 parts by mass or more, 400 parts by mass or more, 500 parts by mass or more, 600 parts by mass or more, or 700 parts by mass or more. It may be 800 parts by mass or more. Further, in the heat conductive composition, when the content of organopolysiloxane is 100 parts by mass, the upper limit of the total content of the alkoxysilane compound and the siloxane-modified acrylic resin is not particularly limited, and is, for example, 1000 parts by mass. It can be as follows. Hereinafter, each component will be described in detail.

<Organopolysiloxane>
The thermally conductive composition according to the present technology contains organopolysiloxane from the viewpoints of molding processability, weather resistance, adhesion to electronic components, followability, and the like. Organopolysiloxane refers to a polymer compound in which an organic group is added to a structure having a portion in which a silicon atom is bonded to another silicon atom via oxygen. Organopolysiloxane usually refers to an organic polymer having a siloxane bond as a main chain. Organopolysiloxane can be cured by applying thermal energy, light energy, or the like in the presence of a curing catalyst. The organopolysiloxane is classified according to the curing mechanism, and examples thereof include an addition polymerization curing type (addition reaction type), a polypolymerization curing type (condensation type), an ultraviolet curing type, and a peroxide fusing type. The organopolysiloxane may be used alone or in combination of two or more.

In particular, when the heat conductive composition is applied to a heat conductive sheet sandwiched between a heating element and a heat radiating member, organopoly is used from the viewpoint of adhesion between the heat generating surface and the heat sink surface of the electronic component. It is preferable to use an addition reaction type silicone resin (additional reaction type liquid silicone resin) as the siloxane. Examples of the addition reaction type silicone resin include (i) a main agent containing silicone having an alkenyl group as a main component, (ii) a main agent containing a curing catalyst, and (iii) a curing agent having a hydrosilyl group (Si—H group). Examples thereof include a two-component addition reaction type silicone resin comprising. (I) As the silicone having an alkenyl group, for example, an organopolysiloxane having a vinyl group can be used. The (ii) curing catalyst is a catalyst for promoting an addition reaction between (i) an alkenyl group in a silicone having an alkenyl group and (iii) a hydrosilyl group in a curing agent having a hydrosilyl group. (Ii) Examples of the curing catalyst include well-known catalysts as catalysts used in the hydrosilylation reaction, and for example, platinum group curing catalysts such as platinum group metals such as platinum, rhodium and palladium, platinum chloride and the like may be used. Can be done. (Iii) As the curing agent having a hydrosilyl group, for example, an organopolysiloxane having a hydrosilyl group can be used.

The organopolysiloxane component may contain a silicone resin containing a Si—OH group. The silicone resin containing a Si—OH group is a group consisting of M unit (R ₃ SiO _1/2 ), Q unit (SiO ₂ ), T unit (RSiO _3/2 ) and D unit (R ₂ SiO). Examples thereof include an organopolysiloxane composed of a copolymer having at least one unit (R represents a monovalent hydrocarbon group or a hydroxyl group) selected from the above. As the silicone resin containing a Si—OH group, an organopolysiloxane (MQ resin) made of a copolymer having M units and Q units is preferable.

As the addition reaction type silicone resin which is an example of organopolysiloxane, a desired commercially available product can be used in consideration of the hardness of the cured product obtained by curing the heat conductive composition. For example, CY52-276, CY52-272, EG-3100, EG-4000, EG-4100, 527 (above, manufactured by Toray Dow Corning), KE-1800T, KE-1031, KE-1051J (above, Shin-Etsu Chemical). (Made by Kogyo Co., Ltd.).

<Thermal conductive filler>
The heat conductive filler can be selected from known materials in view of the desired thermal conductivity and filling property, for example, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, aluminum, copper and silver. Examples thereof include metals such as, alumina, metal oxides such as magnesium oxide, metal nitrides such as aluminum nitride, boron nitride and silicon nitride, carbon nanotubes, metallic silicon and fiber fillers (glass fiber, carbon fiber). The heat conductive filler may be used alone or in combination of two or more.

The thermally conductive composition according to the present technology preferably contains, for example, an inorganic filler as a thermally conductive filler, more preferably a nitrogen compound, and heat, from the viewpoint of achieving good flame retardancy. It is more preferable to contain a nitrogen compound having a conductivity of 60 W / m · K or more. As such a nitrogen compound, aluminum nitride or boron nitride is preferable, and aluminum nitride is more preferable. Further, the heat conductive composition according to the present technology may contain at least one of aluminum nitride, metal hydroxide, metal oxide and carbon fiber as the heat conductive filler. Examples of the metal hydroxide and the metal oxide include aluminum hydroxide, alumina, aluminum nitride, magnesium oxide and the like. For example, as the heat conductive filler, only alumina, only aluminum nitride, or only carbon fibers may be used. In particular, the heat conductive composition according to the present technology preferably contains at least aluminum nitride as a heat conductive filler from the viewpoint of flame retardancy and heat conductivity, and contains aluminum nitride, alumina, and magnesium oxide. It is more preferable to use a mixture, and a mixture containing carbon fibers further may be used.

The content of the heat conductive filler in the heat conductive composition can be appropriately determined according to the desired thermal conductivity and the like, and the volume content in the heat conductive composition can be set to, for example, 80 to 90 volumes. Can be%. When the content of the heat conductive filler in the heat conductive composition is less than 80% by volume, it tends to be difficult to obtain sufficient thermal conductivity. Further, when the content of the heat conductive filler in the heat conductive composition exceeds 90% by volume, it tends to be difficult to fill the heat conductive filler. The content of the heat conductive filler in the heat conductive composition can be 83% by volume or more, 84% by volume or more, 85% by volume or more, and 83 to 85%. It can also be% by volume. When two or more kinds of thermally conductive fillers are used in combination, it is preferable that the total amount satisfies the above range of contents.

Further, when the heat conductive filler contains aluminum nitride, the content of aluminum nitride in the heat conductive filler can be 1 to 100% by volume.

<Alkoxysilane compound>
The thermally conductive composition contains an alkoxysilane compound. In the heat conductive composition, the alkoxysilane compound is hydrolyzed with, for example, the amount of water contained in the heat conductive filler, binds to the heat conductive filler, and contributes to the dispersion of the heat conductive filler. do. The alkoxysilane compound is a compound having a structure in which 1 to 3 of the four bonds of the silicon atom (Si) are bonded to an alkoxy group and the remaining bonds are bonded to an organic substituent.

Examples of the alkoxy group contained in the alkoxysilane compound include a methoxy group, an ethoxy group, a protoxy group, a butoxy group, a pentoxy group, and a hexatoxy group. The alkoxysilane compound is preferably an alkoxysilane compound having a methoxy group or an ethoxy group from the viewpoint of availability. The number of alkoxy groups contained in the alkoxysilane compound is preferably two or more, and more preferably three (trialkoxysilane), from the viewpoint of further enhancing the affinity with the heat conductive filler as an inorganic substance. As a specific example of the alkoxysilane compound, at least one selected from a trimethoxysilane compound and a triethoxysilane compound is preferable.

The functional groups contained in the organic substituents of the alkoxysilane compound are, for example, an acryloyl group, an alkyl group, a carboxyl group, a vinyl group, a methacrylic group, an aromatic group, an amino group, an isocyanate group, an isocyanurate group, an epoxy group and a hydroxyl group. Examples include a group and a mercapto group. Here, when an addition reaction type organopolysiloxane containing a platinum catalyst is used as the precursor of the above-mentioned addition reaction type silicone resin, it is preferable that the alkoxysilane compound does not easily affect the curing reaction of the organopolysiloxane. .. For example, when an addition reaction type organopolysiloxane containing a platinum catalyst is used as the organopolysiloxane, the organic substituent of the alkoxysilane compound does not contain an amino group, an isocyanate group, an isocyanurate group, a hydroxyl group, or a mercapto group. Is preferable.

From the viewpoint of increasing the dispersibility of the thermally conductive filler and facilitating higher filling of the thermally conductive filler, an alkylalkoxysilane compound having an alkyl group bonded to a silicon atom, that is, an alkyl group-containing alkoxysilane compound. Is preferable. In the alkyl group-containing alkoxysilane compound, the number of carbon atoms of the alkyl group bonded to the silicon atom is preferably 4 or more, and may be 6 or more, 8 or more, or 10 or more. .. Further, from the viewpoint of suppressing the viscosity of the thermally conductive composition to be lower, the number of carbon atoms of the alkyl group bonded to the silicon atom in the alkyl group-containing alkoxysilane compound is preferably 16 or less, and may be 14 or less. , 12 or less. In the alkyl group-containing alkoxysilane compound, the alkyl group bonded to the silicon atom may be linear, branched, or cyclic.

The alkoxysilane compound may be used alone or in combination of two or more. Specific examples of the alkoxysilane compound include a vinyl group-containing alkoxysilane compound, an acryloyl group-containing alkoxysilane compound, a methacrylic group-containing alkoxysilane compound, an aromatic group-containing alkoxysilane compound, and an amino group-containing compound, in addition to the alkyl group-containing alkoxysilane compound. Examples thereof include an alkoxysilane compound, an isocyanate group-containing alkoxysilane compound, an isocyanurate group-containing alkoxysilane compound, an epoxy group-containing alkoxysilane compound, and a mercapto group-containing alkoxysilane compound.

Examples of the alkyl group-containing alkoxysilane compound include methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, and n-propyltri. Ethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, hexadecyltrimethoxy Examples include silane. Among the alkyl group-containing alkoxysilane compounds, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxy At least one selected from silane and hexadecyltrimethoxysilane is preferable, and at least one of n-decyltrimethoxysilane and hexadecyltrimethoxysilane is more preferable.

Examples of the vinyl group-containing alkoxysilane compound include vinyltrimethoxysilane and vinyltriethoxysilane.

Examples of the acryloyl group-containing alkoxysilane compound include 3-acryloyloxypropyltrimethoxysilane.

Examples of the methacryl group-containing alkoxysilane compound include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane.

Examples of the aromatic group-containing alkoxysilane compound include phenyltrimethoxysilane and phenyltriethoxysilane.

Examples of the amino group-containing alkoxysilane compound include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, and 3-aminopropyltri. Examples thereof include methoxysilane, 3-aminopropyltriethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

Examples of the isocyanate group-containing alkoxysilane compound include 3-isocyanatepropyltriethoxysilane. Examples of the isocyanurate group-containing alkoxysilane compound include tris- (trimethoxysilylpropyl) isocyanurate.

Examples of the epoxy group-containing alkoxysilane compound include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycid. Examples thereof include xipropyltriethoxysilane.

Examples of the mercapto group-containing alkoxysilane compound include 3-mercaptopropyltrimethoxysilane.

In particular, the thermally conductive composition according to the present technology preferably contains an arcosixylan compound having a melting point of −40 ° C. or higher and a boiling point of 100 ° C. or higher. When the boiling point of the alcoholicylan compound is 100 ° C. or higher, it is possible to more effectively suppress the vaporization of the alkoxysilane compound at room temperature, and as a result, the heat conductive sheet becomes too hard due to condensation or the like. It can be prevented more reliably. In the present specification, "normal temperature" means a range of 15 to 25 ° C. specified in JIS K0050: 2019 (general rule of chemical analysis method). Further, when the melting point of the alkoxysilane compound is −40 ° C. or higher, it is possible to more effectively suppress the hardening of the thermally conductive sheet at room temperature (for example, 1 to 30 ° C.) or lower, and the flexibility of the sheet is further improved. Can be done. The upper limit of the boiling point of the alcoholicylan compound is not particularly limited, and the higher the boiling point, the more preferable. Examples of alcoholicylan compounds having a melting point of −40 ° C. or higher and a boiling point of 100 ° C. or higher include decyltrimethoxysilane, hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane, n-dodecyltrimethoxysilane, and the like. Examples thereof include n-dodecyltriethoxysilane and hexyltrimethoxysilane. In the thermally conductive composition according to the present technology, it is preferable to use decyltrimethoxysilane and hexadecyltrimethoxysilane in combination.

When the content of the organopolysiloxane in the heat conductive composition is 100 parts by mass, the content of the alkoxysilane compound can be, for example, 50 parts by mass or more, or 100 parts by mass or more. , 200 parts by mass or more, 300 parts by mass or more, 350 parts by mass or more, 400 parts by mass or more, 500 parts by mass or more. , 600 parts by mass or more can be used. Further, when the content of the organopolysiloxane in the heat conductive composition is 100 parts by mass, the upper limit of the content of the alkoxysilane compound can be, for example, 750 parts by mass or less, and 700 parts by mass or less. It can also be 650 parts by mass or less.

The content of the alkoxysilane compound in the heat conductive composition is not particularly limited, and may be, for example, 0.1 to 4.0 parts by mass with respect to 100 parts by mass of the heat conductive filler. , 0.2 to 2.0 parts by mass. When two or more kinds of alkoxysilane compounds are used in combination, it is preferable that the total amount satisfies the above range of contents.

When decyltrimethoxysilane and hexadecyltrimethoxysilane are used in combination as the alkoxysilane compound, the mass ratio of decyltrimethoxysilane to hexadecyltrimethoxysilane (decyltrimethoxysilane: hexadecyltrimethoxysilane) is , 100: 98 to 100: 201 are preferable.

<siloxane-modified acrylic resin>
The thermally conductive composition according to the present technology contains a siloxane-modified acrylic resin. The siloxane-modified acrylic resin is a (meth) acrylic acid ester having one or more polydimethylsiloxane structure (-(CH ₃ ) ₂ SiO) _n- ; n is an integer of 1 or more) and a (meth) acrylic acid alkyl ester. It is a copolymer with. The siloxane-modified acrylic resin is a component for softening the sheet obtained from the thermally conductive composition. The siloxane-modified acrylic resin can further improve the dispersibility of the thermally conductive filler in the thermally conductive composition as compared with, for example, silicone oil.

Examples of the (meth) acrylic acid ester having one or more polydimethylsiloxane structures include dimethicone methacrylate. Examples of the (meth) acrylic acid alkyl ester include methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylhexyl acrylate, tridecylic acrylate, and stearyl acrylate.

Specific examples of the siloxane-modified acrylic resin include stearyl-modified acrylate silicone (a copolymer of acrylate, stearyl acrylate and dimethicone methacrylate) and behenyl-modified acrylate silicone (a copolymer of acrylate, behenyl acrylate and dimethicone methacrylate). ), Ethylhexyl-modified acrylate silicone (a copolymer of acrylate, ethylhexyl acrylate and dimethicone methacrylate) and the like. The siloxane-modified acrylic resin may have a hydrophilic functional group such as a carboxy group, an epoxy group, a carbonyl group, a hydroxyl group, or an ether group.

In particular, the thermally conductive composition according to the present technology preferably contains a siloxane-modified acrylic resin having a melting point of 55 ° C. or lower, and may contain a siloxane-modified acrylic resin having a melting point in the range of 0 to 45 ° C. More preferred. When the melting point of the siloxane-modified acrylic resin is 55 ° C or lower, flexibility is exhibited in the actual use range, and it becomes easier to adhere to semiconductor chips such as ICs, CPUs (Central Processing Units), and APs (application processors). There are advantages. The lower limit of the melting point of the siloxane-modified acrylic resin is not particularly limited, but is preferably 25 ° C. or higher, for example. When the melting point of the siloxane-modified acrylic resin is 25 ° C or higher, the siloxane-modified acrylic resin becomes a solid at room temperature, and the siloxane-modified acrylic resin becomes a liquid by heating. It can be further improved.

Commercially available siloxane-modified acrylic resins include KP-541, KP-543, KP-545, KP-545L, KP-550, KP-561P, KP-562P, KP-574, and KP-578 (above, Shin-Etsu Silicone). (Manufactured by Toagosei Co., Ltd.), Cymac (registered trademark) US-350 (manufactured by Toagosei Co., Ltd.) and the like. Among these commercially available siloxane-modified acrylic resins, KP-561P and KP-562P are preferable, and KP-561P is more preferable, from the viewpoint of having a melting point of 55 ° C. or lower. The siloxane-modified acrylic resin may be used alone or in combination of two or more. Further, two or more kinds of siloxane-modified acrylic resins having a melting point of 55 ° C. or lower may be used in combination.

When the content of organopolysiloxane in the heat conductive composition is 100 parts by mass, the content of the siloxane-modified acrylic resin can be, for example, 50 parts by mass or more, or 100 parts by mass or more. It can be 200 parts by mass or more, 300 parts by mass or more, or 350 parts by mass or more. Further, when the content of the organopolysiloxane in the heat conductive composition is 100 parts by mass, the upper limit of the content of the siloxane-modified acrylic resin can be, for example, 500 parts by mass or less, and 450 parts by mass. It can be as follows, or it can be 400 parts by mass or less.

Further, the lower limit of the content of the siloxane-modified acrylic resin can be, for example, 0.1 part by mass or more with respect to 100 parts by mass of the heat conductive filler, or 0.3 part by mass or more. It may be 1 part by mass or more. Further, the upper limit of the content of the siloxane-modified acrylic resin can be, for example, 10 parts by mass or less, 7 parts by mass or less, or 5 parts by mass with respect to 100 parts by mass of the heat conductive filler. It may be less than 2 parts by mass, less than 2 parts by mass, or less than 1 part by mass. When two or more kinds of siloxane-modified acrylic resins are used in combination, it is preferable that the total amount satisfies the above range of contents.

<Antioxidant>
The thermally conductive resin composition according to the present technology may further contain an antioxidant in addition to the above-mentioned components from the viewpoint of further enhancing the effect of the present technology. As the antioxidant, for example, a hindered phenolic antioxidant may be used, or a hindered phenolic antioxidant and a thiol-based antioxidant may be used in combination. The hindered phenolic antioxidant, for example, captures radicals (peroxy radicals) and effectively contributes to the suppression of oxidative deterioration of organopolysiloxane (addition reaction type silicone resin). For example, a thiol-based antioxidant effectively contributes by decomposing hydrooxide radicals and suppressing oxidative deterioration of organopolysiloxane (addition reaction type silicone resin).

<Hindered phenolic antioxidant>
Examples of the hindered phenolic antioxidant include those having a structure represented by the following formula 1 as a hindered phenol skeleton. The hindered phenolic antioxidant preferably has one or more skeletons represented by the following formula 1, and may have two or more skeletons represented by the following formula 1.

(Equation 1)

In formula 1, when R ¹ and R ² represent a t-butyl group and R ³ represents a hydrogen atom (hindered type), R ¹ represents a methyl group, R ² represents a t-butyl group, and R When ³ represents a hydrogen atom (semi-hindered type), R ¹ represents a hydrogen atom, R ² represents a t-butyl group, and R ³ represents a methyl group (less hindered type). From the viewpoint of long-term thermal stability in a high temperature environment, a semi-hindered type or a hindered type is preferable. Further, the hindered phenolic antioxidant has three or more skeletons represented by the above formula 1 in one molecule, and the three or more skeletons represented by the formula 1 are hydrocarbon groups or. , It is preferable that the structure is linked by a group consisting of a hydrocarbon group and a combination of —O— and —CO—. The hydrocarbon group may be linear, branched or cyclic. The number of carbon atoms of the hydrocarbon group can be, for example, 3 to 8. The molecular weight of the hindered phenolic antioxidant can be, for example, 300 to 850, or 500 to 800.

The hindered phenolic antioxidant may have an ester bond in its structure. Examples of such phenolic antioxidants include stearyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and tetrakis [3- (3', 5'-di-t-butyl-). 4'-Hydroxyphenyl) propionic acid] pentaerythritol, 2,2'-dimethyl-2,2'-(2,4,8,10-tetraoxaspiro [5.5] undecane-3,9-diyl) dipropane -1,1'-Diyl-bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propanoate] and the like can be mentioned. Further, as the hindered phenol-based antioxidant, those having no ester bond in its structure, for example, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane and the like, etc. Can also be used.

Commercially available phenolic antioxidants include Adekastab AO-30, Adekastab AO-50, Adekastab AO-60, Adekastab AO-80 (above, manufactured by ADEKA), Irganox 1010, Irganox 1035, Irganox 1076, Ilganox 1135 (above, manufactured by BASF) and the like can be mentioned. The phenolic antioxidant may be used alone or in combination of two or more.

The lower limit of the content of the phenolic antioxidant can be, for example, 0.1 part by mass or more, or 0.5 part by mass or more with respect to 100 parts by mass of the organopolysiloxane. Further, the upper limit of the content of the phenolic antioxidant may be, for example, 10 parts by mass or less with respect to 100 parts by mass of the organopolysiloxane, and may be 5 parts by mass or less. When two or more kinds of phenolic antioxidants are used in combination, it is preferable that the total amount satisfies the above range of contents.

<Thiol-based antioxidant>
Examples of the thiol-based antioxidant include a type having a thioether skeleton and a type having a hindered phenol skeleton. For example, examples of the thiol-based antioxidant include ditridecyl 3,3'-thiobispropionic acid, tetrakis [3- (dodecylthio) propionic acid] pentaerythritol, and 4,6-bis (octylthiomethyl) -o-cresol. Can be mentioned.

Commercially available thiol-based antioxidants include ADEKA STAB AO-412S, ADEKA STAB AO-503, ADEKA STAB AO-26 (above, manufactured by ADEKA), Sumilyzer TP-D (manufactured by Sumitomo Chemical), and Irganox1520L (manufactured by BASF Japan). ) And so on. Among these thiol-based antioxidants, tetrakis [3- (dodecylthio) propionic acid] pentaerythritol (commercially available: Adecastab AO-412S, Sumitomo Chemical Co., Ltd.), Irganox 1520L is preferable. The thiol-based antioxidant may be used alone or in combination of two or more.

The content of the thiol-based antioxidant in the heat conductive composition may be about the same as that of the phenol-based antioxidant, or may be higher than that of the phenol-based antioxidant. For example, the lower limit of the content of the thiol-based antioxidant can be, for example, 0.1 part by mass or more with respect to 100 parts by mass of the organopolysiloxane. Further, the upper limit of the content of the thiol-based antioxidant may be, for example, 20 parts by mass or less, or 10 parts by mass or less, with respect to 100 parts by mass of the organopolysiloxane. When two or more kinds of thiol-based antioxidants are used in combination, it is preferable that the total amount satisfies the above range of contents.

As described above, the thermally conductive composition according to the present technology contains an organopolysiloxane, a thermally conductive filler, an alkoxysilane compound, and a siloxane-modified acrylic resin. By using these components in combination, the synergistic effect can improve the thermal conductivity and flexibility when the thermally conductive composition is made into a thermally conductive sheet. Further, the heat conductive composition according to the present technology has heat conductivity and flexibility when formed into a sheet even if the heat conductive filler contains 80 to 90% by volume of the heat conductive filler. Can be good.

The thermally conductive composition according to the present technology may further contain components other than the above-mentioned components as long as the effects of the present technology are not impaired. For example, the thermally conductive composition may further contain a heavy metal inactivating agent for the purpose of improving the deterioration resistance of the thermally conductive sheet. Examples of the heavy metal deactivating agent include the ADEKA STAB ZS series (such as ADEKA STAB ZS-90) manufactured by ADEKA.

The thermally conductive composition according to the present technology can be obtained, for example, by kneading each of the above-mentioned components using a kneader (planetary kneader, ball mill, Henschel mixer, etc.). When, for example, a two-component addition reaction type silicone resin is used as the organopolysiloxane, the required amount of the heat conductive filler is not mixed at once with the main agent, the curing agent and the heat conductive filler. The main agent and the curing agent may be divided and mixed separately, and the component containing the main agent and the component containing the curing agent may be mixed at the time of use.

<Thermal conductive sheet>
FIG. 1 is a cross-sectional view showing an example of a heat conductive sheet. The heat conductive sheet 1 is made of a cured product of the above-mentioned heat conductive composition. For example, the heat conductive sheet 1 is desired to have a heat conductive composition on a release film 11 formed of, for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), polyolefin, polymethylpentene, glassin paper, or the like. It is obtained by curing the organopolysiloxane, which is a binder resin, by applying it to the thickness of the above and heating it. The thickness of the heat conductive sheet 1 (thickness of the sheet body excluding the release film 11) can be appropriately selected depending on the intended purpose, and can be, for example, 0.05 to 5 mm.

By using the above-mentioned thermal conductive composition, the thermal conductive sheet 1 can have a thermal conductivity of 3.5 W / m · K or more, and can also have a thermal conductivity of 4.0 W / m · K or more. , 4.5 W / m · K or more, 5.0 W / m · K or more, 6.0 W / m · K or more, 7.0 W / m · K or more It can be more than 7.5 W / m · K or more. The upper limit of the thermal conductivity of the thermal conductivity sheet 1 is not particularly limited, but can be, for example, 12.0 W / m · K or less, 11.0 W / m · K or less, and 9 It can also be set to 0.0 W / m · K or less. The method for measuring the thermal conductivity is the same as in the examples described later.

Further, since the heat conductive sheet 1 itself is softened by heat, for example, the degree of adhesion to a heat generating element or a heat radiator can be increased and the thermal resistance value (contact thermal resistance value) can be lowered. For example, the thermal resistance sheet 1 can have a thermal resistance value of 1.0 ° C. cm ² / W or less, 0.9 ° C. cm ² / W or less, and 0.7 ° C. ·. It can be cm ² / W or less, 0.5 ° C. cm ² / W or less, 0.3 ° C. cm ² / W or less, 0.2 ° C. cm ² or less. It can also be less than / W. The lower limit of the thermal resistance value of the heat conductive sheet 1 is not particularly limited, but may be, for example, 0.01 ° C. cm ² / W or more. The method for measuring the thermal resistance value is the same as in the examples described later.

Further, the thermal conductivity sheet 1 can have a thermal conductivity retention rate of 70% or more, which is 75% or more, as shown by the following formula 2 when aged at 200 ° C. for 24 hours, for example. It can be 80% or more, or 90% or more.
Equation 2: (Thermal conductivity of the heat conductive sheet after the aging treatment / The thermal conductivity of the heat conductive sheet before the aging treatment) × 100

Further, since the heat conductive sheet 1 uses the above-mentioned heat conductive composition, it has good flexibility. For example, the compressibility (heat conductivity) when pressure is applied at 45 ° C. and a load of 1 kgf / cm ² . The ratio of the amount of change from the initial thickness of the sheet) divided by the initial thickness of the heat conductive sheet, that is, the compressibility represented by the following formula 3 can be 60% or more, and can be 70% or more. It can be 80% or more. The upper limit of the compression rate is not particularly limited, but can be, for example, 90% or less.
Equation 3: Compressibility (%) = ((Initial thickness of heat conductive sheet-Initial compression thickness of heat conductive sheet) / Initial thickness of heat conductive sheet) × 100

As described above, since the heat conductive sheet 1 is made of the above-mentioned heat conductive composition, due to the synergistic effect of the organopolysiloxane, the heat conductive filler, the alkoxysilane compound, and the siloxane modified acrylic resin, It has good thermal conductivity and flexibility, and in particular, even those made of a thermally conductive composition containing 80 to 90% by volume of a thermally conductive filler have good thermal conductivity and flexibility. Further, since the heat conductive sheet 1 has a small repulsion against compression and the sheet itself is softened by heat, it has good adhesion to, for example, a heat generating element or a heat radiating body. That is, the heat conductive sheet 1 has high followability to the heat generating element and the radiator.

As described above, since the heat conductive sheet 1 has good heat conductivity and flexibility, it can be applied to a heat dissipation structure in which the heat conductive sheet 1 is sandwiched between a heating element and a heat radiation member. Examples of the heating element include integrated circuit elements such as CPUs, GPUs (Graphics Processing Units), DRAMs (Dynamic Random Access Memory), flash memories, transistors, resistors, and other electronic components that generate heat in electric circuits. The heating element also includes a component that receives an optical signal such as an optical transceiver in a communication device. The heat radiating member may be a member that conducts heat generated from a heating element and dissipates it to the outside. For example, a heat sink, a heat spreader, or the like, which is used in combination with an integrated circuit element, a transistor, an optical transceiver housing, or the like. Can be mentioned. Further, examples of the heat radiating member include a radiator, a cooler, a die pad, a printed circuit board, a cooling fan, a Pelche element, a heat pipe, a metal cover, a housing, and the like.

FIG. 2 is a cross-sectional view showing an example of a semiconductor device. In actual use, for example, the heat conductive sheet 1 from which the release film 11 has been peeled off can be mounted inside an electronic component such as a semiconductor device or various electronic devices. As shown in FIG. 2, for example, the heat conductive sheet 1 is mounted on a semiconductor device 50 built in various electronic devices and is sandwiched between a heating element and a heat radiating member. That is, the electronic device includes a heating element, a heat radiating member, and a heat conductive sheet 1 arranged between the heating element and the heat radiating member. The semiconductor device 50 shown in FIG. 2 has at least an electronic component 51, a heat spreader 52, and a heat conductive sheet 1, and the heat conductive sheet 1 is sandwiched between the heat spreader 52 and the electronic component 51. By using the heat conductive sheet 1, the semiconductor device 50 has high heat dissipation. Further, the heat conductive sheet 1 is sandwiched between the heat spreader 52 and the heat sink 53 to form a heat radiating member that dissipates heat of the electronic component 51 together with the heat spreader 52. The mounting location of the heat conductive sheet 1 is not limited to between the heat spreader 52 and the electronic component 51 and between the heat spreader 52 and the heat sink 53, and can be appropriately selected depending on the configuration of the electronic device or the semiconductor device.

This technology can also be applied to articles equipped with the heat dissipation structure described above. Articles having such a heat dissipation structure include, for example, ECUs used for controlling electrical components such as personal computers, server devices, mobile phones, radio base stations, engines of transportation machines such as automobiles, power transmission systems, steering systems, and air conditioners. (Electronic Control Unit) can be mentioned.

Hereinafter, examples of this technology will be described. In this example, a thermally conductive composition composed of the raw materials shown in Table 1 was obtained. The dispersibility of this thermally conductive composition was evaluated. In addition, each evaluation shown in Table 1 was performed on the heat conductive sheet obtained from the heat conductive composition. The present technology is not limited to the following examples.

<Preparation of thermally conductive composition>
The raw materials used in this example are as follows.

Silicone resin A (Product name: CY52-276A, manufactured by Toray Dow Corning)
Silicone resin B (Product name: CY52-276B, manufactured by Toray Dow Corning)
Graft copolymer composed of acrylic polymer and dimethylpolysiloxane (product name: KP-561P, melting point 25-35 ° C, manufactured by Shinetsu Silicone Co., Ltd.)
Graft copolymer composed of acrylic polymer and dimethylpolysiloxane (product name: KP-578, melting point 55 ° C or less, manufactured by Shin-Etsu Silicone Co., Ltd.)
Polyglycerin-modified silicone surfactant with branched silicone chains (Product name: KF-6106, manufactured by Shinetsu Silicone Co., Ltd.)
Alkoxytrialkoxysilane: Hexadecyltrimethoxysilane (Product name: Dynasylan 9116 (melting point 1 ° C, boiling point 155 ° C), manufactured by Evonik Japan)
Alkoxytrialkoxysilane: decyltrimethoxysilane (product name: Z-6210 (melting point -37 ° C, boiling point 115 ° C), manufactured by Toray Dow Corning)
Phenolic antioxidant (Product name: AO-80, manufactured by ADEKA)
Heavy metal deactivating agent (ZS-90, manufactured by ADEKA Corporation)
Mixture of Aluminum Nitride, Alumina (Spherical Alumina) and Magnesium Oxide Mixage of Aluminum Nitride and Alumina (Spherical Alumina)

<Examples 1 to 5, Comparative Examples 1 and 2>
As the heat conductive filler, a mixture of aluminum nitride and alumina or a mixture of aluminum nitride, alumina and magnesium oxide was used. In the case of Examples 1 and 3 using the mixture of aluminum nitride and alumina, the mixing amount is about 10640 parts by mass of aluminum nitride and about 1880 parts by mass of alumina with respect to 100 parts by mass of the silicone resin, one by one for the silicone resin. It was stirred each time it was added. In the case of Examples 2, 4 and 5 using a mixture of aluminum nitride, alumina and magnesium oxide, the mixing amount was about 4220 parts by mass of aluminum nitride and about 2800 parts by mass of alumina with respect to 100 parts by mass of the silicone resin. The amount of magnesium oxide was about 4980 parts by mass, and the mixture was stirred each time it was added to the silicone resin one by one. Further, in the case of Comparative Examples 1 and 2 using a mixture of aluminum nitride, alumina and magnesium oxide, the total mixing amount of aluminum nitride, alumina and magnesium oxide is about 8000 parts by mass (aluminum nitride) with respect to 100 parts by mass of the silicone resin. : Alumina: Magnesium oxide = 1.5: 1: 1.78), and the mixture was stirred each time it was added to the silicone resin one by one. A planetary stirrer was used for stirring, and the rotation speed was set to 1200 rpm. Next, using a bar coater, the heat conductive composition was applied onto a release film (material: PET, thickness 125 μm) so as to have a thickness of 2 mm or 1.5 mm, and then a cover film (material) to which a release agent was applied. : PET, thickness 50 μm) was covered and heated at 80 ° C. for 6 hours to obtain a heat conductive sheet.

[Dispersity]
The heat conductive filler was added one by one to the heat conductive composition in which the components excluding the heat conductive filler were mixed, and the mixture was stirred. A commercially available rotation / revolution stirrer (rotational vacuum stirring defoaming mixer (device name: V-mini 300, manufactured by EME) was used for stirring, and the rotation speed was set to 1200 rpm. The time required for the conductive filler to disperse was visually evaluated. The results are shown in Table 1.
A: Within 2 minutes B: Over 2 minutes, within 4 minutes C: Over 4 minutes, within 6 minutes D: Over 6 minutes, within 10 minutes E: Over 10 minutes Stirring does not allow mixing at all.

[Initial thermal conductivity]
Using a thermal resistance measuring device compliant with ASTM-D5470, the initial thermal conductivity (W / m · K) in the thickness direction of the heat conductive sheet was measured by applying a load of 1 kgf / cm ² . The sheet temperature at the time of measurement was 45 ° C. The results are shown in Table 1.

[Compression rate]
For the compressibility (initial compressibility), the heat conductive sheet prepared in each example and comparative example is cut into a predetermined size (20 mmφ × thickness 2000 μm), and the average temperature of the heat conductive sheet becomes 45 ° C. A load of 1 kgf / cm ² was applied, and the thickness after stabilization (initial compression thickness [μm]) was measured, and the compressibility (%) was determined according to the above formula 3. The results are shown in Table 1.

[Thermal resistance value]
Using a thermal resistance measuring device compliant with ASTM-D5470, the thermal resistance value (° C. cm ² / W) of the heat conductive sheet was measured by applying a load of 1 kgf / cm ² . Practically, the thermal resistance value is preferably 1.0 (° C. cm ² / W) or less. The results are shown in Table 1.

[Handling (room temperature)]
At room temperature (25 ° C.), the handleability was evaluated as "OK" when the heat conductive sheet could be easily peeled off from the release film, and the handleability was evaluated as "NG" when the heat conductive sheet could not be peeled off. The results are shown in Table 1.

[Softness]
Observe the maximum stress when a 25.4 mm square, 1.5 mm thick heat conductive sheet is compressed by 70% at a compression rate of 25.4 mm / min, and the residual stress of the sheet when the compressed state is held for 10 minutes. When the maximum stress was 300 psi or less and the residual stress was 50 psi or less, it was evaluated as OK, and when it was not, it was evaluated as NG. The results are shown in Table 1.

[Heat stability]
Is the shape of the heat conductive sheet maintained and the oil bleeding is minimal when the heat conductive sheet is cut to a thickness of 2 mm and 30 mm × 30 mm and aged at 200 ° C for 24 hours (super accelerated test)? Please evaluate (heat stability). When there is no shape change and the oil bleed is within 1 mm, the heat resistance stability is evaluated as "○", and when the shape is slightly deformed but the oil bleed is within 1 mm, the heat resistance stability is evaluated as "△" and the shape is The heat stability was evaluated as "x" when it was significantly deformed or when it did not correspond to "○" or "Δ". Practically, it is preferable that the evaluation of heat resistance stability is "〇" or "Δ". The results are shown in Table 1.

In Examples 1 to 5, when the organopolysiloxane, the heat conductive filler, the alkoxysilane compound, and the siloxane-modified acrylic resin are contained, and the content of the organopolysiloxane is 100 parts by mass, the alkoxysilane compound is used. Since the heat conductive composition having a total content of 100 parts by mass or more of the siloxane-modified acrylic resin was used, it was found that a heat conductive sheet having good initial thermal conductivity and softness (flexibility) could be obtained. ..

On the other hand, in Comparative Example 1, since the heat conductive composition containing no alkoxysilane compound was used, it was found that the dispersibility of the heat conductive composition was not good and it was difficult to obtain a heat conductive sheet.

In Comparative Example 2, it was found that the softening property was not good because the heat conductive composition containing no siloxane-modified acrylic resin was used.

1 Thermal conductive sheet, 11 release film, 50 semiconductor device, 51 electronic components, 52 heat spreader, 53 heat sink

Claims (13)

1. Organopolysiloxane and
   Thermally conductive filler and
   Alkoxysilane compound and
   Contains siloxane-modified acrylic resin,
   A thermally conductive composition in which the total content of the alkoxysilane compound and the siloxane-modified acrylic resin is 100 parts by mass or more, where the content of the organopolysiloxane is 100 parts by mass.
2. The thermally conductive composition according to claim 1, wherein the alkoxysilane compound contains an alcoholicylan compound having a melting point of −40 ° C. or higher and a boiling point of 100 ° C. or higher.
3. The thermally conductive composition according to claim 1 or 2, wherein the siloxane-modified acrylic resin has a melting point of 55 ° C. or lower.
4. The heat conductive composition according to claim 1 or 2, wherein the siloxane-modified acrylic resin is solid at room temperature.
5. The heat conductive composition according to any one of claims 1 to 4, which contains 80 to 90% by volume of the heat conductive filler.
6. The thermally conductive composition according to any one of claims 1 to 5, wherein the alkoxysilane compound contains at least one of decyltrimethoxysilane and hexadecyltrimethoxysilane.
7. The thermal conductivity according to claim 6, wherein the mass ratio of the decyltrimethoxysilane to the hexadecyltrimethoxysilane (decyltrimethoxysilane: hexadecyltrimethoxysilane) is in the range of 100: 98 to 100: 201. Composition.
8. The thermally conductive composition according to any one of claims 1 to 7, wherein the organopolysiloxane is an addition reaction type organopolysiloxane.
9. One of claims 1 to 8, wherein the organopolysiloxane is a two-component addition reaction type silicone resin comprising an organopolysiloxane having a vinyl group, a curing agent having a hydrosilyl group, and a curing catalyst. The thermally conductive composition according to the section.
10. A heat conductive sheet made of a cured product of the heat conductive composition according to any one of claims 1 to 9.
11. The heat conductive sheet according to claim 10, which has a thermal conductivity of 6.0 W / m · K or more.
12. The heat conductive sheet according to claim 10 or 11, wherein the compressibility represented by the following formula 3 is 60% or more when a pressure is applied at 45 ° C. and a load of 1 kgf / cm ² .
    Equation 3: Compressibility (%) = ((Initial thickness of the heat conductive sheet-Initial compression thickness of the heat conductive sheet) / Initial thickness of the heat conductive sheet) × 100
13. With a heating element,
    With heat dissipation member,
    A heat conductive sheet arranged between the heating element and the heat radiating member is provided.
    The heat conductive sheet is an electronic device made of a cured product of the heat conductive composition according to any one of claims 1 to 9.
    

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