JP7395933B2 - Thermal conductive resin composition - Google Patents

Description

The present invention relates to a resin composition with excellent thermal conductivity, a thermally conductive adhesive using the same, and an electronic component.

In recent years, the heat generation density per unit volume has increased due to the miniaturization and high density of electronic components, and there is a demand for improvement in the thermal conductivity of thermally conductive adhesives for bonding each component. One way to improve the thermal conductivity of a thermally conductive adhesive is to fill it with a highly thermally conductive filler. For example, in Patent Document 1, high thermal conductivity of a cured product is achieved by blending a highly thermally conductive filler and controlling the particle size and shape of the filler.
However, when a large amount of thermally conductive filler is mixed into an epoxy compound monomer to improve thermal conductivity, the viscosity of the resin composition increases significantly, resulting in problems such as deterioration of workability and reduction of adhesive strength.

Therefore, since there is a limit to increasing the thermal conductivity by using a thermally conductive filler, there is a need to improve the thermal conductivity of the cured product by improving the thermal conductivity of the epoxy resin itself, which is the matrix.
For example, Patent Document 2 describes a method for improving thermal conductivity using a biphenol type epoxy resin and an epoxy resin containing various mesogen skeletons.

Japanese Patent Application Publication No. 2015-174906 Japanese Patent Application Publication No. 11-323162

However, in the method described in Patent Document 2, the viscosity of the monomer epoxy resin composition itself increases, so when adding a thermally conductive filler, it is necessary to add a solvent to lower the viscosity. there were. As a result, the adhesive has poor handling properties. Furthermore, the thermal conductivity and adhesiveness of the cured product were not sufficient, and further improvements were required.

The present invention was devised in view of the problems of the prior art, and provides a resin composition for forming an adhesive layer with excellent thermal conductivity, a thermally conductive cured product using the same, and an electronic component. It is.

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by the means shown below, and have arrived at the present invention. That is, the present invention consists of the following configuration.

It contains an epoxy compound (A), an amine curing agent (B), and a thermally conductive filler (C), the epoxy compound (A) is liquid, and the amine curing agent (B) has a fibrous shape. A resin composition characterized by:

The amine curing agent (B) preferably has a short axis of 1 μm to 200 μm and a long axis of 50 μm to 1000 μm. Moreover, it is preferable to have a benzoxazole skeleton.

The thermally conductive filler (C) is spherical and is made of alumina, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, silicon nitride, barium titanate, silicon carbide, carbon, diamond, silver, gold, copper, nickel and aluminum. It is preferable that it is at least one selected from the group consisting of:

It is preferable that the epoxy compound (A) contains a trifunctional or higher functional epoxy compound in an amount of 10% by weight or more based on the entire epoxy compound (A).

The content of the thermally conductive filler (C) is preferably 40% to 75% by volume based on the total volume of the resin composition, and the mass ratio of the epoxy compound (A) to the amine curing agent (B) is (A )/(B)=90/10 to 60/40.

A thermally conductive adhesive or an electronic component comprising the resin composition described above.

The resin composition of the present invention can form a cured product with high thermal conductivity while maintaining adhesiveness. Further, electronic components using the resin composition of the present invention also have excellent thermal conductivity.

<Epoxy compound (A)>
The epoxy compound (A) used in the present invention needs to be liquid at room temperature (25°C). It is preferably liquid even at 10°C or lower, and more preferably liquid even at 0°C or lower. Since the epoxy compound (A) is in a liquid state, the thermal conductivity of the resin composition can be improved. The lower limit is not particularly limited, and -20°C or higher is industrially sufficient.

The epoxy compound (A) is not particularly limited as long as it is liquid at room temperature (25°C), and examples include bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, and tetramethylbisphenol F. Bisphenol-type epoxy compounds that are glycidylated bisphenols such as methylbisphenol AD, tetramethylbisphenol S, tetrabromobisphenol A, tetrachlorobisphenol A, and tetrafluorobisphenol A; biphenol, dihydroxynaphthalene, 9,9-bis(4-hydroxy) 1,1,1-tris(4-hydroxyphenyl)methane, 4,4-(1-(4-(1-(4-hydroxyphenyl)) - Epoxy compounds in which trisphenols such as -1-methylethyl)phenyl)ethylidene) bisphenol are glycidylated; Epoxy compounds in which tetrakisphenols such as 1,1,2,2,-tetrakis(4-hydroxyphenyl)ethane are glycidylated Compounds: Novolac-type epoxy compounds that are glycidylated novolacs such as phenol novolac, cresol novolac, bisphenol A novolak, brominated phenol novolak, and brominated bisphenol A novolac; polyhydric phenols such as catechol, resorcinol, hydroquinone, and benzenetriol. Glycidylated epoxy compounds; Aliphatic ether type epoxy compounds that are glycidylated polyhydric alcohols such as glycerin and polyethylene glycol; Ether ester type epoxy compounds that are glycidylated hydroxycarboxylic acids such as p-oxybenzoic acid and β-oxynaphthoic acid. Compounds: Ester-type epoxy compounds that are glycidylated polycarboxylic acids such as phthalic acid and terephthalic acid; Glycidylated products of amine compounds such as 4,4-diaminodiphenylmethane, metaxylylene diamine, and aminophenol; Amines such as triglycidyl isocyanurate Glycidyl type epoxy compounds such as type epoxy compounds; alicyclic epoxides such as 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, and the like. These can be used alone or in combination of two or more. Among these, epoxy compounds containing glycidylated bisphenol A, epoxy compounds containing glycidylated bisphenol F, aminophenol-type epoxy compounds, metaxylylene diamine-type epoxy compounds, or phenol have excellent adhesion and heat resistance of cured products. Novolac type epoxy compounds are preferred.

When the total amount of the epoxy compound (A) is 100% by mass, it is preferable that 10% by mass or more of a polyfunctional epoxy compound having three or more functionalities (having a trivalent epoxy group) is contained in one molecule. The content is more preferably 20% by mass or more, and still more preferably 30% by mass or more. By containing 10% by mass or more of a trifunctional or higher polyfunctional epoxy compound, the crosslinking density can be improved and the thermal conductivity can be further increased. As the trifunctional or higher polyfunctional epoxy compound, metaxylylene diamine type epoxy compounds and aminophenol type epoxy compounds are preferable. These polyfunctional epoxy compounds may be used alone or in combination of two or more.

<Amine curing agent (B)>
The amine curing agent (B) used in the present invention needs to be solid at room temperature (25° C.) and fibrous in shape. Fibrous includes needle-like or string-like shapes. By using the fibrous amine curing agent (B), it becomes possible to increase the thermal conductivity of the cured product of the resin composition of the present invention. It is preferably solid and fibrous even at 40°C or higher, more preferably solid and fibrous at 60°C or higher, and even more preferably solid and fibrous even at 80°C or higher.

The amine curing agent (B) reacts with the liquid epoxy compound (A) at room temperature to form a cured epoxy resin. At that time, by using the fibrous amine curing agent (B), the amine curing agent (B) is filled between the particles of the thermally conductive filler (C). During the subsequent curing reaction, the epoxy resin (A) is oriented in the direction of the fibers and hardens and grows, forming a heat conduction path between the thermally conductive fillers (C), resulting in the thermal conductivity of the entire cured product. is expected to be increased.

It is necessary that the amine curing agent (B) of the present invention has a fibrous shape. Fibrous means that the average value of the aspect ratio (the ratio of the length of the major axis to the minor axis of the amine curing agent (B)) is 4 or more. Preferably it is 6 or more, more preferably 8 or more. By setting the average value of the aspect ratio to 4 or more, the thermal conductivity of the cured product of the resin composition can be improved. Although the upper limit of the average value of the aspect ratio is not particularly limited, it is preferably 20 or less, more preferably 18 or less, and still more preferably 15 or less. In the present invention, the average value of the aspect ratio can be determined by randomly extracting 30 particles of the amine curing agent (B) and measuring the major axis and minor axis of each particle. Further, in the amine curing agent (B), those having an aspect ratio of 2 or less are preferably 10% by mass or less, more preferably 5% by mass when the entire amine curing agent (B) is 100% by mass. % or less, more preferably 1% by mass or less, particularly preferably 0% by mass. By setting the aspect ratio of 2 or less to 10% by mass or less, the cured product of the resin composition can exhibit excellent thermal conductivity.

The long axis of the fibrous amine curing agent (B) is preferably in the range of 50 μm to 1000 μm, more preferably 100 μm to 800 μm, and even more preferably 200 μm to 600 μm. If the major axis is less than 50 μm, the above-mentioned effect of improving thermal conductivity may not be sufficient, and if it exceeds 1000 μm, the fibrous amines will be oriented in the surface direction in the coating film, which will reduce the thermal conductivity in the thickness direction of the cured product. There is a risk that the rate may become insufficient.

The short axis of the fibrous amine curing agent (B) is preferably in the range of 1 μm to 200 μm, more preferably 3 μm to 100 μm, and still more preferably 5 μm to 80 μm. If the short axis is less than 1 μm, the above-mentioned effect of improving thermal conductivity may not be sufficient, and if it exceeds 100 μm, the filling property between the thermally conductive fillers will deteriorate, resulting in insufficient thermal conductivity of the cured product. There is a risk.

As the type of fibrous amine curing agent (B), general diamine compounds for curing epoxy can be used as long as they are solid at room temperature (25° C.) and satisfy the above-mentioned fibrous shape. For example, p-xylylene diamine, 1,5-diaminonaphthalene, m-phenylene diamine, p-phenylene diamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenyl ether, 1 , 1-bis(4-aminophenyl)cyclohexane, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodicyclohexane, dicyandiamide 5-amino-2-(p-aminophenyl)benzoxazole, 6-amino- 2-(p-aminophenyl)benzoxazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzoxazole, 2,2'-p-phenylenebis (5-aminobenzoxazole), 2,2'-p-phenylenebis(6-aminobenzoxazole), 1-(5-aminobenzoxazolo)-4-(6-aminobenzoxazolo)benzene, 2, 6-(4,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d: 4,5-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,4' -diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:5,4-d'] Examples include bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, and among these, those having a fibrous particle shape. It is preferable to select one or more of them as appropriate. Among these, from the viewpoint of thermal conductivity and particle shape of the cured product, diamine compounds having a benzoxazole skeleton are preferred, and among them, 5-amino-2-(p-aminophenyl)benzoxazole or 6-amino-2 -(m-aminophenyl)benzoxazole is preferably used.

Further, the amine curing agent (B) is preferably a compound that does not dissolve in the liquid epoxy compound (A) from the viewpoint of the above-mentioned thermal conductivity improving effect and storage stability of the resin composition. The solubility of the epoxy compound (A) of the amine curing agent (B) at room temperature (25°C) is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably It is 0.1% by mass or less.

The mixing ratio of the epoxy compound (A) and the amine curing agent (B) is usually expressed as the amine equivalent (amine equivalent/epoxy equivalent) of the amine curing agent (B) per 1 equivalent of epoxy group of the epoxy compound (A). A range of 0.2 to 1.2 equivalents is preferred from the viewpoint of physical properties of the cured product of the resin composition. More preferably it is 0.4 or more, and still more preferably 0.6 or more. Further, it is preferably 1.0 or less, more preferably 0.8 or less.

The mass ratio of the epoxy compound (A) to the amine curing agent (B) is preferably (A)/(B) = 90/10 to 60/40, more preferably 85/15 to 65/35. , more preferably 80/20 to 70/30. By setting it within the above range, the cured product of the resin composition exhibits excellent thermal conductivity.

<Thermal conductive filler (C)>
The thermally conductive filler (C) is not limited as long as it has thermal conductivity. For example, conductive inorganic fillers such as alumina, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, silicon nitride, barium titanate, silicon carbide, carbon, diamond, silver, gold, copper, nickel, aluminum, etc. It can be used or two or more types can be used in combination. Among these, it is preferable to use electrically insulating inorganic fillers. By using an electrically insulating inorganic filler, for example, when used inside an electronic device, it is possible to promote heat dissipation and prevent short circuits between components. Specific examples include aluminum nitride, alumina, barium titanate, boron nitride, silicon carbide, zinc oxide, and the like. Among these, aluminum nitride, boron nitride, or alumina is preferred.

The shape of the thermally conductive filler (C) can be either regular or irregular. Examples of the shape include a polygon, a cube, an ellipse, a sphere, a needle, a plate, a scale, or a mixture or aggregate thereof. Among these, it is preferable to use spherical ones. By using the spherical thermally conductive filler (C), the filling property with the fibrous amine curing agent (B) becomes good, and the effect of improving thermal conductivity is most exhibited. The aspect ratio of the thermally conductive filler (C) is preferably 1.5 or less, more preferably 1.3 or less, and still more preferably 1.1 or less.

The average particle diameter of the thermally conductive filler (C) is not particularly limited, but is preferably 1 μm to 100 μm, more preferably 2 μm to 80 μm, even more preferably 3 μm to 60 μm, and even more preferably 5 μm to 50 μm. It is particularly preferable that there be. If the average particle diameter is less than 1 μm, the viscosity of the resin composition may become high and workability may deteriorate, and there is a risk that thermal conductivity may deteriorate. When the average particle diameter exceeds 100 μm, the minimum coating thickness of the resin composition increases, which may lead to a worsening of the heat resistance of the coating film.

The amount of the thermally conductive filler (C) added is not particularly limited, but is preferably 40% to 75% by volume, more preferably 45% to 70% by volume based on the total volume of the resin composition. , more preferably 55% to 65% by volume. If the amount of the thermally conductive filler (C) added is less than 40% by volume, the thermal conductivity of the filler may not be achieved, and if it exceeds 75% by volume, the viscosity of the resin composition may increase and workability may deteriorate. , the adhesive strength may deteriorate.

<Resin composition>
The resin composition of the present invention is a resin composition containing at least a liquid epoxy compound (A), a fibrous amine curing agent (B), and a thermally conductive filler (C). In the present invention, if necessary, an epoxide-reactive diluent or a low boiling point organic solvent may be added to an extent that does not reduce thermal conductivity, reactivity, heat resistance, toughness, storage stability, etc. Examples of reactive diluents include phenyl glycidyl ether, butyl glycidyl ether, alkyl glycidyl ether, alkyl diglycidyl ether, alkylene glycol glycidyl ether, alkylene glycol diglycidyl ether, styrene oxide, octylene oxide, and mixtures thereof. It will be done. Examples of organic solvents include methanol, ethanol, propanol, butanol, toluene, xylene, Solvesso®, Isopar®, ethyl acetate, butyl acetate, methyl ethyl ketone, cyclohexanone, cyclohexanol, isophorone, methyl cellosolve. , ethyl cellosolve, butyl cellosolve, butyl cellosolve acetate, ethyl carbitol, ethyl carbitol acetate, ethylene glycol monoacetate, dimethyl formamide, γ-butyl lactone, n-methyl pyrrolidone, and the like. However, it is preferable not to include an organic solvent, since the addition of an organic solvent may deteriorate the adhesiveness and thermal conductivity of the cured product due to the formation of voids, and may adversely affect the working environment due to volatilization of the organic solvent. Preferably, when the entire resin composition is 100% by mass, it is preferably 50% by mass or less, more preferably 20% by mass or less, still more preferably 5% by mass or less, and 0% by mass. There is no problem.

In addition, silane coupling agents, titanate coupling agents, antioxidants such as hindered phenols and phosphorus, mold release agents such as higher fatty acids and waxes, flame retardant agents such as halogens and phosphorus compounds, and antifoaming agents. Additives such as agents and colorants can also be used as necessary.

When the resin composition of the present invention is heated, the fibrous amine cured product (B) and the epoxy compound (A) react to form an adhesive layer as an epoxy cured resin. That is, by heating and curing the resin composition of the present invention, a thermally conductive adhesive having excellent thermal conductivity and adhesiveness can be obtained. The heating temperature depends on the types of the epoxy compound (A) and the amine curing agent (B), but is usually in the range of 80°C to 250°C, preferably in the range of 100°C to 200°C, and more preferably in the range of 100°C to 200°C. is in the range of 120°C to 160°C. Further, the reaction (curing) time can be set as appropriate, and is usually 0.1 to 6 hours, preferably 0.5 to 5 hours, and more preferably about 1 to 3 hours.

The resin composition of the present invention will be specifically shown in Examples below, but the present invention is not limited thereto. In Examples and Comparative Examples, parts simply refer to parts by mass.

(Example 1)
20 parts by mass of epoxy compound 1, 5 parts by mass of fibrous amine 1, 70 parts by mass of thermally conductive filler 1, and 30 parts by mass of thermally conductive filler 2 are placed in a flask, and the resin is formed by stirring and mixing thoroughly. Product 1 was produced. The thermal conductivity of the thermoset resin composition 1 obtained was measured. The results are shown in Table 1.

(Examples 2 to 12, Comparative Examples 1 to 4)
Each part by mass of each component listed in Tables 1 and 2 was blended, and resin compositions 2 to 16 were prepared by sufficiently stirring and mixing in the same manner as in Example 1. The thermal conductivity of the thermoset resin compositions 2 to 16 obtained was measured. The results are shown in Tables 1 and 2.

<Shape measurement of amine curing agent (C)>
Thirty particles of amine curing agent (C) were randomly extracted. Next, the major axis and minor axis of the 30 extracted particles were measured using a digital microscope VHX-2000 manufactured by Keyence Corporation, and the average value was calculated.

<Preparation of thermoset>
The resin compositions obtained in the Examples and Comparative Examples were put into a mold set at 150°C and hot press molded at 150°C for 2 hours to obtain thermoset test pieces.

<Measurement of thermal conductivity>
Thermal diffusivity, specific heat, and density at 25°C were measured for each thermoset test piece of the resin composition obtained in the Examples and Comparative Examples, and the thermal conductivity was calculated from the following formula.
(Formula): Thermal conductivity λ (W/mK) = α・Cp・d
α: Thermal diffusivity (m ² /s), Cp: Specific heat (J/(kg・K), d: Density (kg/m 3)
The thermal diffusivity α was measured by the xenon flash method using a xenon flash analyzer LFA467Hyperflash manufactured by NETZSCH. The density d was measured by the Archimedes method. Further, the specific heat Cp was measured by the DSC method using DSC7020 manufactured by Hitachi High-Tech Science.

<Measurement of adhesive strength>
Shear adhesive strength was measured according to JIS-K6850 (1990). A resin composition was applied to 12.5 mm of one side of a 25 mm x 100 mm x 1.6 mm aluminum piece, another aluminum piece of the same type was attached, and the test piece was cured by heating at 150°C for 2 hours (aluminum A piece/resin composition/aluminum piece) was prepared. This was pulled parallel to the adhesive surface at a pulling speed of 10 mm/min, and the adhesive strength was determined by dividing the maximum load at breakage by the adhesive area.

The details of the raw materials in the table are as follows.
<Epoxy compound (A)>
Epoxy compound 1: jER (registered trademark) 828 (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation), difunctional epoxy compound, liquid at room temperature (25°C) Epoxy compound 2: iER (registered trademark) 630 (aminophenol type epoxy Resin, manufactured by Mitsubishi Chemical Corporation), trifunctional epoxy compound, liquid at room temperature (25° C.) Epoxy compound 3: jER (registered trademark) 152 (phenol novolak type epoxy resin, manufactured by Mitsubishi Chemical Corporation). A mixture containing a trifunctional or higher functional epoxy compound, liquid at room temperature (25°C) <Amine curing agent (B)>
Fibrous amine 1: 5-amino-2-(p-aminophenyl)benzoxazole, major axis 468 μm, minor axis 34 μm, average aspect ratio 13.8
Fibrous amine 2: 5-amino-2-(p-aminophenyl)benzoxazole, major axis 193 μm, minor axis 32 μm, average aspect ratio 6.0
Fibrous amine 3: 5-amino-2-(p-aminophenyl)benzoxazole, major axis 58 μm, minor axis 11 μm, average aspect ratio 5.3
Fibrous amine 4: 6-amino-2-(m-aminophenyl)benzoxazole, major axis 201 μm, minor axis 20 μm, average aspect ratio 10.1
Fibrous amine 5: m-phenylenediamine, major axis 107 μm, minor axis 18 μm, average aspect ratio 5.9
Non-fibrous amine 1: dicyandiamide, major axis 8 μm, minor axis 6 μm, average aspect ratio 1.3
Non-fibrous amine 2: m-phenylenediamine, major axis 52 μm, minor axis 44 μm, average aspect ratio 1.2
Non-fibrous amine 3: 5-amino-2-(p-aminophenyl)benzoxazole, major axis 24 μm, minor axis 21 μm, average aspect ratio 1.1
<Thermal conductive filler (C)>
Filler 1: DAW-45 (spherical alumina, manufactured by Denka)
Filler 2: DAW-05 (spherical alumina, manufactured by Denka)
Filler 3: AO-509 (spherical alumina, manufactured by Admatex)
Filler 4: SP-3 (scaly boron nitride, manufactured by Denka)

As can be seen from the results shown in Tables 1 and 2, the cured products of Examples 1 to 12 using a fibrous amine curing agent are different from the cured products of Comparative Examples 1 to 4 using a non-fibrous amine curing agent. It exhibited both superior thermal conductivity and adhesive strength compared to the previous one.

Since the resin composition of the present invention contains an epoxy compound (A), a fiber-shaped amine curing agent (B), and a thermally conductive filler (C), it exhibits excellent adhesiveness and thermal conductivity. Therefore, it is suitable for use in electronic components.

Claims (10)

Contains an epoxy compound (A), an amine curing agent (B), and a thermally conductive filler (C) , does not contain an organic solvent , the epoxy compound (A) is liquid, and the amine curing agent (B) is A thermally conductive resin composition having a fibrous shape and an average aspect ratio of 4 or more, wherein the amine curing agent (B) is a compound that does not dissolve in the epoxy compound (A) . The thermally conductive resin composition according to claim 1, wherein the amine curing agent (B) has a short axis of 1 μm to 200 μm and a long axis of 50 μm to 1000 μm. The thermally conductive resin composition according to claim 1 or 2, wherein the thermally conductive filler (C) is spherical. Thermal conductive filler (C) is selected from the group consisting of alumina, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, silicon nitride, barium titanate, silicon carbide, carbon, diamond, silver, gold, copper, nickel and aluminum. The thermally conductive resin composition according to any one of claims 1 to 3, wherein the thermally conductive resin composition is at least one of: The thermally conductive resin composition according to any one of claims 1 to 4, wherein the content of the thermally conductive filler (C) is 40% to 75% by volume based on the total volume of the resin composition. The thermally conductive resin composition according to any one of claims 1 to 5, characterized in that the epoxy compound (A) contains a trifunctional or higher functional epoxy compound in an amount of 10% by mass or more based on the entire epoxy compound (A). thing. The heat according to any one of claims 1 to 6, characterized in that the mass ratio of the epoxy compound (A) and the amine curing agent (B) is (A)/(B) = 90/10 to 60/40. Conductive resin composition. The thermally conductive resin composition according to any one of claims 1 to 7, wherein the amine curing agent (B) has a benzoxazole skeleton. A thermally conductive adhesive comprising the thermally conductive resin composition according to any one of claims 1 to 8. An electronic component comprising the thermally conductive resin composition according to any one of claims 1 to 8.