WO2012002505A1

WO2012002505A1 - Ceramic mixture, and ceramic-containing thermally-conductive resin sheet using same

Info

Publication number: WO2012002505A1
Application number: PCT/JP2011/065085
Authority: WO
Inventors: 雄樹大塚
Original assignee: 昭和電工株式会社
Priority date: 2010-07-02
Filing date: 2011-06-30
Publication date: 2012-01-05
Also published as: KR20130051456A; JP5793494B2; KR101453352B1; TWI520926B; TW201215583A; JPWO2012002505A1

Abstract

A ceramic mixture of spherical alumina particles having a volumetric D50 of 10-55μm, and flake hexagonal boron nitride particles having a volumetric D50 of at most 30μm, wherein the content ratio of the flake hexagonal boron nitride particles is 5-30 mass%; and a ceramic-containing thermally-conductive resin sheet formed from a resin composition containing 10-70 vol% of an organic matrix and 30-90 vol% of the ceramic mixture.

Description

Ceramic mixture and ceramic-containing thermally conductive resin sheet using the same

The present invention relates to a ceramic mixture and a ceramic-containing thermally conductive resin sheet using the ceramic mixture. More specifically, the present invention relates to a ceramic mixture that provides a highly thermally conductive resin sheet, and a thermally conductive resin sheet that is used to transfer heat from a heating element to a heat radiating member, particularly a semiconductor element, etc., using the ceramic mixture. The present invention relates to a heat conductive resin sheet for forming a heat conductive resin layer that transmits heat from the heating element to a heat radiating member and also functions as an insulating layer.

In recent years, the degree of integration of electronic parts such as ICs used in various electronic devices has been improved. Furthermore, in order to meet the demand for downsizing of electronic devices and the like, heat radiation countermeasures against heat generation in the housing has become a big problem by arranging electronic components such as ICs in a small space with high density. In other words, when the temperature rises, the characteristics of the electronic component such as an IC may change the characteristics of the electronic component and cause malfunction of the device, or the electronic component itself may fail.

On the other hand, while the amount of heat generated from semiconductor devices such as CPUs, which are increasing in speed, is increasing, various electronic devices have been made smaller and lighter and thinner. Therefore, in order to maintain the performance and function, it is necessary to sufficiently remove the generated heat, and an efficient heat dissipation system is required.

The heat conductive resin layer that transfers heat from the heat generating part of the electric / electronic device to the heat radiating member has high heat conductivity, insulation, and adhesive properties. A resin composition is used.
For example, in a power module, a thermosetting resin sheet or coating film containing an inorganic filler is used as a heat conductive resin layer provided between the back surface of a lead frame on which a power semiconductor element is mounted and a metal plate serving as a heat dissipation part. A technique to be used is known (see, for example, Patent Document 1).

Further, as a heat conductive resin layer interposed between a heat generating electronic component such as a CPU and a heat radiating fin, a thermosetting resin sheet filled with highly heat conductive inorganic powder is known (for example, patent document). 2).
As disclosed in Patent Document 2, spherical alumina particles are easily dispersed as inorganic powder, can be highly filled, and are very useful as a heat conductive filler used for a heat conductive sheet. For this reason, it has been studied to change the organic matrix by changing the combination with other thermally conductive fillers or an organic matrix so that the thermally conductive fillers are filled more highly (for example, Patent Documents 3 and 4). reference).

In Patent Document 5, the inorganic powder capable of exhibiting high heat dissipation characteristics is a mixed powder containing a predetermined spherical inorganic powder and a non-spherical inorganic powder having an average particle diameter smaller than that of the spherical inorganic powder, and the average particle diameter is Inorganic powders that are 5-50 μm are disclosed. However, it is unclear whether the same effect can be obtained with other inorganic powders by actually evaluating the combination selected from silica, alumina, silicon carbide, and aluminum nitride.
In addition, when a high specific filler such as alumina is highly filled, the heat conductive resin sheet itself becomes heavy, which makes it difficult to reduce the size and weight of electronic devices.
Furthermore, along with the downsizing of electronic devices and the like, if the thermal conductive resin sheet is made thinner, the dielectric breakdown characteristics may deteriorate. In addition, aluminum nitride, which is said to have high thermal conductivity, is unstable and difficult to handle due to moisture in the atmosphere, is expensive, and silicon carbide, which also has excellent thermal conductivity, has poor dielectric breakdown characteristics. Was a problem.
For example, Patent Document 6 discloses a thermal conductive resin sheet using a combination of silicon nitride having a particle diameter of 5 μm and boron nitride having a particle diameter of 7 μm. However, since the particle diameter of silicon nitride is too small, uniform dispersion is disclosed. However, there is a problem that it is not always possible to bring about the combined effect. The document also discloses a thermal conductive resin sheet using silicon carbide and boron nitride, but a system using silicon carbide may have poor dielectric breakdown characteristics.

JP 2001-196495 A JP 2003-253136 A Japanese Patent Laid-Open No. 11-87958 JP 2000-1616 A JP 2007-70474 A Japanese Patent No. 4089636

The present invention has been made under such circumstances, has a thermal conductivity superior to that of the conventional one, can reduce the weight of the sheet, is excellent in workability, and has a dielectric breakdown characteristic. It is an object of the present invention to provide a ceramic mixture that gives a good heat conductive resin sheet, and a ceramic-containing heat conductive resin sheet having the above properties using the ceramic mixture.

As a result of intensive studies to achieve the above object, the present inventors have obtained the following knowledge.
First, although the flaky hexagonal boron nitride particles have high thermal conductivity, they are disadvantageous in that they are difficult to disperse in an organic matrix and have poor processability. Thus, it has been found that by mixing with spherical alumina particles having good fluidity, the scale-like hexagonal boron nitride particles can be easily dispersed and the workability is improved. In addition, by utilizing the feature that scaly hexagonal boron nitride particles have high thermal conductivity in the plane direction, spherical alumina particles play a role as an aggregate, so that they are oriented in the thickness direction of the thermal conductive sheet. It has been found that high thermal conductivity can be obtained. It was also found that excellent dielectric breakdown characteristics can be obtained by using alumina instead of silicon carbide having poor dielectric breakdown characteristics.
Based on the above findings, a ceramic mixture containing, in a predetermined ratio, flaky hexagonal boron nitride particles having a specific particle size and spherical alumina particles having a specific particle size is used as a thermally conductive filler. As a result, the thermal conductivity is superior to that of using alumina particles and boron nitride particles alone, and the weight of the sheet can be reduced and the workability is excellent. It has been found that a resin sheet can be obtained.

That is, the present invention is as follows.
[1] A mixture of spherical alumina particles having a volume-based D50 (50% by volume particle diameter) of 10 to 55 μm and flaky hexagonal boron nitride particles having a volume-based D50 of 30 μm or less, wherein the flaky shape A ceramic mixture, wherein the content of hexagonal boron nitride particles is 5 to 30% by mass.
[2] The ceramic mixture according to [1], wherein the volume-based D50 of the flaky hexagonal boron nitride particles is 5 to 30 μm.
[3] A ceramic-containing thermally conductive resin sheet obtained by molding a resin composition containing 10 to 70% by volume of an organic matrix and 30 to 90% by volume of the ceramic mixture according to [1] or [2].
[4] The ceramic-containing thermally conductive resin sheet according to [3], wherein the volume-based D50 of the spherical alumina is 3 to 7 times the volume-based D50 of the flaky hexagonal boron nitride particles.
[5] The ceramic according to [3], wherein the volume-based D50 of the spherical alumina particles in the ceramic mixture is 45 to 55 μm, and the ceramic mixture is contained in the resin composition in a proportion of 70 to 80% by volume. Contains thermally conductive resin sheet.
[6] The content ratio of the flaky hexagonal boron nitride particles in the ceramic mixture is 6 to 25% by mass, and the ceramic mixture is contained in the resin composition in a ratio of 75 to 80% by volume [5]. A ceramic-containing thermally conductive resin sheet according to 1.
[7] The ceramic-containing thermally conductive resin sheet according to [6], wherein the thermal conductivity is 7 W / m · K or more.
[8] The content ratio of the flaky hexagonal boron nitride particles in the ceramic mixture is 15 to 25% by mass, and the ceramic mixture is contained in the resin composition at a ratio of 70 to 80% by volume [5]. A ceramic-containing thermally conductive resin sheet according to 1.
[9] The ceramic-containing thermally conductive resin sheet according to [8], wherein the thermal conductivity is 9 W / m · K or more.
[10] The ceramic-containing thermally conductive resin sheet according to any one of [4] to [9], wherein the organic matrix includes a curable epoxy resin.
[11] The ceramic-containing thermally conductive resin sheet according to any one of [4] to [9], wherein the organic matrix includes a curable silicone resin.

ADVANTAGE OF THE INVENTION According to this invention, the ceramic which provides the heat conductive resin sheet which has the thermal conductivity superior to the past, can reduce the weight of a sheet | seat, is excellent in workability, and has a favorable dielectric breakdown characteristic. It is possible to provide a thermally conductive resin sheet having the above-described properties using the mixture and the ceramic mixture.

FIG. 1A is a diagram illustrating a “scale-like” form of scaly hexagonal boron nitride particles. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line XX in FIG. Show.

First, the ceramic mixture of the present invention will be described.
[Ceramic mixture]
The ceramic mixture of the present invention has a thermal conductivity superior to that of the prior art, can reduce the weight of the sheet, and provides a thermally conductive resin sheet for providing a thermally conductive resin sheet excellent in workability. A mixture of spherical alumina particles having a volume-based D50 of 10 to 55 μm and flaky hexagonal boron nitride particles having a volume-based D50 of 30 μm or less, the flaky hexagonal boron nitride particles The content is 5 to 30% by mass.

(Spherical alumina particles)
The alumina particles, which is one of the two components constituting the ceramic mixture of the present invention, have good thermal conductivity and may be spherical or non-spherical. In the ceramic mixture of the present invention, in view of the difficulty of dispersing the later-described flaky hexagonal boron nitride particles as the other component in the organic matrix, spherical alumina particles having good fluidity are used as the alumina particles. Is used. Here, the spherical alumina particles refer to powders having a spherical shape or a shape close to a spherical shape among alumina powders.

In the present invention, “spherical” is evaluated by average sphericity. The average sphericity can be measured as follows using a flow type particle image analyzer such as “FPIA-1000” manufactured by Sysmex Corporation. First, the projected area (A) and the perimeter (PM) of the particle are measured from the particle image. When the area of a perfect circle corresponding to the perimeter (PM) is (B), the sphericity of the particle can be displayed as A / B. Therefore, assuming a perfect circle having the same circumference as that of the sample particle (PM), PM = 2πr and B = πr ² , so that B = π × (PM / 2π) ² , and each particle has a spherical shape. The degree can be calculated as sphericity = A / B = A × 4π / (PM) ² . This is measured for 100 or more particles arbitrarily selected, and the average value is defined as the average sphericity. The term “spherical” in the present invention means that the sphericity is in the range of 0.93 to 1.00, and if it is a normal commercial product and is clearly shown as spherical or spherical, this range is satisfied. .

The volume-based D50 of the spherical alumina particles needs to be 10 to 55 μm and is 25 to 55 μm from the viewpoint of the dispersibility of the ceramic mixture in the organic matrix, the performance of the obtained heat conductive resin sheet, and the like. It is preferably 45 to 55 μm. From the above viewpoint, spherical alumina particles having a sharp particle size distribution are preferred.
In the present invention, the volume-based D50 can be measured by a Coulter counter method, a laser diffraction scattering method, or the like. For example, in the case of spherical alumina particles, it is preferable to measure by a Coulter counter method, and in the case of flaky hexagonal boron nitride particles, it is preferable to measure by a laser diffraction scattering method.

(Scale-like hexagonal boron nitride particles)
As the flaky hexagonal boron nitride particles as the other component constituting the ceramic mixture of the present invention, those having a volume-based D50 of 30 μm or less are used. When the volume-based D50 exceeds 30 μm, the heat conductive resin sheet from which the scaly particles can be easily oriented parallel to the thickness direction in the organic matrix is difficult to obtain desired heat conductivity.
The volume-based D50 of the flaky hexagonal boron nitride particles is preferably 5 to 30 μm, and more preferably 5 to 15 μm. When the volume-based D50 is less than 5 μm, the viscosity of the resin composition containing the organic matrix and the ceramic mixture increases, and the workability may decrease.
By using scale-like hexagonal boron nitride particles having a larger volume-based D50 within a range where the volume-based D50 does not exceed 30 μm, the interface between the particles is reduced and heat can be more easily transferred. .
Here, “scale-like” means the major axis L of the scale-like hexagonal boron nitride particles 10 as shown in the plan view of FIG. 1A and the XX cross-sectional view of FIG. 1A (FIG. 1). (B)) means a form in which the ratio (aspect ratio (L: r)) to the thickness r (average thickness) of the particles 10 is 5: 1 to 20: 1.

When a large amount of impurities (for example, B ₂ O ₃ ) is contained in the flaky hexagonal boron nitride, when an organic matrix that requires curing is used, it becomes a factor of inhibition of curing. Moreover, it becomes a factor by which the heat conductivity of the obtained heat conductive resin sheet falls. From such a viewpoint, the content of B ₂ O ₃ as an impurity inevitably mixed in the flaky hexagonal boron nitride is preferably 0.01 to 0.1% by mass, More preferably, it is -0.05 mass%.

The content of the flaky hexagonal boron nitride particles in the ceramic mixture of the present invention is required to be 5 to 30% by mass. When this content exceeds 30 mass%, the viscosity of the resin composition containing the organic matrix and the ceramic mixture increases, which causes a decrease in workability. In addition, since the scale-like hexagonal boron nitride particles are expensive, if this content exceeds 30% by mass, it becomes commercially disadvantageous. From such a viewpoint, the content of the flaky hexagonal boron nitride particles in the ceramic mixture is preferably 30% by mass or less. Moreover, if it is less than 5 mass%, the outstanding heat conductivity cannot be provided. The content is preferably 6 to 25% by mass, more preferably 10 to 25% by mass, further preferably 15 to 25% by mass, and particularly preferably 18 to 25% by mass.

The volume-based D50 of the spherical alumina particles is preferably 3 to 7 times, more preferably 4 to 6 times the volume-based D50 of the flaky hexagonal boron nitride particles. When the ratio is 3 to 7 times, it is possible to obtain a significantly higher thermal conductivity than when spherical alumina particles are used alone or scaly hexagonal boron nitride particles are used alone.

The spherical alumina particles and flaky hexagonal boron nitride particles described above are subjected to a surface treatment using various coupling agents, etc., as necessary, for the purpose of improving dispersibility in an organic matrix and improving processability. Also good.

(Coupling agent)
Examples of the coupling agent include silane-based, titanate-based, and aluminum-based, among which silane-based coupling agents are preferable from the viewpoint of effects. Examples of silane coupling agents include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, and γ- (2-aminoethyl) aminopropyltri Ethoxysilane, γ-anilinopropyltrimethoxysilane, γ-anilinopropyltriethoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane and N-β- (N-vinyl Aminosilane compounds such as (benzylaminoethyl) -γ-aminopropyltriethoxysilane are preferably used.

Next, the ceramic-containing thermally conductive resin sheet of the present invention will be described.
[Ceramics-containing thermally conductive resin sheet]
The ceramic-containing thermally conductive resin sheet of the present invention is formed by molding a resin composition containing 10 to 70% by volume of an organic matrix and 30 to 90% by volume of the ceramic mixture of the present invention described above. To do.
If the ceramic mixture exceeds 90% by volume (organic matrix is less than 10% by volume), the organic matrix is too small to make it difficult to mold the resin composition, and the ceramic mixture is less than 30% by volume (organic matrix). If it exceeds 90% by volume), the fillers are less likely to come into contact with each other in the organic matrix, the thermal conductivity is lowered, and the thermal conductivity required for heat dissipation cannot be obtained.

In the ceramic-containing thermally conductive resin sheet of the present invention, excellent thermal conductivity, weight reduction of sheet weight, good workability and dielectric breakdown are either the following first aspect or second aspect. It is preferable in terms of characteristics.
That is, in the first aspect, the content ratio of the flaky hexagonal boron nitride particles in the ceramic mixture is 6 to 25% by mass, and the ceramic mixture is contained in the resin composition in a ratio of 75 to 80% by volume. This is a ceramic-containing thermally conductive resin sheet. By setting it as this aspect, heat conductivity can be 7 W / m * K or more.
In the second aspect, the content ratio of the flaky hexagonal boron nitride particles in the ceramic mixture is 15 to 25% by mass, and the ceramic mixture is contained in the resin composition at a ratio of 70 to 80% by volume. This is a ceramic-containing thermally conductive resin sheet. By setting it as this aspect, heat conductivity can be 9 W / m * K or more.

(Organic matrix)
The organic matrix used in the ceramic-containing thermally conductive resin sheet of the present invention (hereinafter sometimes simply referred to as “thermally conductive resin sheet”) is the mechanical strength, heat resistance, and durability of the thermally conductive resin sheet. Depending on the required properties such as flexibility and flexibility, select from various thermosetting resins, thermoplastic resins, thermoplastic elastomers, etc. that are conventionally used as the organic matrix of the thermally conductive resin sheet Can be used. These organic matrices may be used singly or in combination of two or more. In the present invention, curable epoxy resins and curable silicone resins are particularly preferably used.

<Curable epoxy resin>
The curable epoxy resin used as the organic matrix in the heat conductive resin sheet of the present invention is an epoxy resin that is liquid at room temperature or a low softening point epoxy that is solid at room temperature from the viewpoint of dispersibility of the ceramic mixture in the organic matrix. Resins are preferred.
The curable epoxy resin is not particularly limited as long as it is a compound having two or more epoxy groups in one molecule, and an arbitrary one is appropriately selected from known compounds conventionally used as epoxy resins. Can be used. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, glycidyl ethers of polycarboxylic acids, and epoxy resins obtained by epoxidation of cyclohexane derivatives. These may be used individually by 1 type, and may be used in combination of 2 or more types. Among the epoxy resins, from the viewpoints of heat resistance and workability, bisphenol A type epoxy resins, bisphenol F type epoxy resins, and epoxy resins obtained by epoxidation of cyclohexane derivatives are suitable.

<Curing agent for epoxy resin>
In order to cure the curable epoxy resin, a curing agent for epoxy resin is usually used.
The curing agent for epoxy resin is not particularly limited, and any one of those conventionally used as curing agents for epoxy resins can be appropriately selected and used. For example, amine-based, phenol-based, acid-based, and the like. An anhydride system etc. are mentioned.
Preferable examples of the amine curing agent include dicyandiamide, aromatic diamines such as m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, and m-xylylenediamine.
Preferable examples of the phenolic curing agent include a phenol novolak resin, a cresol novolak resin, a bisphenol A type novolak resin, and a triazine-modified phenol novolak resin. Examples of the acid anhydride curing agent include aliphatic acids such as alicyclic acid anhydrides such as methylhexahydrophthalic anhydride, aromatic acid anhydrides such as phthalic anhydride, and aliphatic dibasic acid anhydrides. And halogen-based acid anhydrides such as anhydride and chlorendic anhydride.
One of these curing agents may be used alone, or two or more thereof may be used in combination. The amount of the epoxy resin curing agent used is usually about 0.5 to 1.5 equivalent ratio, preferably about 0.1 equivalent ratio to the curable epoxy resin, from the viewpoint of balance between curability and cured resin physical properties. It is selected in the range of 7 to 1.3 equivalent ratio.

<Curing accelerator for epoxy resin>
In this invention, the hardening accelerator for epoxy resins can be used together with the hardening | curing agent for epoxy resins as needed.
There is no restriction | limiting in particular as this hardening accelerator for epoxy resins, From the things conventionally used as a hardening accelerator of an epoxy resin, arbitrary things can be selected suitably and can be used. For example, 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, etc. Examples thereof include imidazole compounds, 2,4,6-tris (dimethylaminomethyl) phenol, boron trifluoride amine complex, and triphenylphosphine.
These hardening accelerators may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the epoxy resin curing accelerator used is usually about 0.1 to 10 parts by mass, preferably about 100 to 10 parts by mass, preferably 100 parts by mass of the curable epoxy resin, from the viewpoint of balance between curing acceleration and physical properties of the cured resin. It is selected in the range of 0.4 to 5 parts by mass.

<Curable silicone resin>
As the curable silicone resin, a mixture of an addition reaction type silicone resin and a silicone-based crosslinking agent can be used. Examples of the addition reaction type silicone resin include at least one selected from polyorganosiloxane having an alkenyl group as a functional group in the molecule. Preferred examples of the polyorganosiloxane having an alkenyl group as a functional group in the molecule include polydimethylsiloxane having a vinyl group as a functional group, polydimethylsiloxane having a hexenyl group as a functional group, and a mixture thereof. .

Examples of the silicone-based crosslinking agent include polyorganosiloxane having a structure in which at least two silicon and hydrogen are bonded in one molecule. Specific examples thereof include dimethylhydrogensiloxy group end-capped dimethylsiloxane-methylhydrogensiloxane copolymer, trimethylsiloxy group end-capped dimethylsiloxane-methylhydrogensiloxane copolymer, trimethylsiloxane group end-capped poly (methylhydrogen). Siloxane), poly (hydrogensilsesquioxane) and the like.

Also, platinum compounds are usually used as the curing catalyst. Examples of the platinum compounds include fine platinum, fine platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, palladium catalyst, rhodium catalyst, and the like. It is done.

(Preparation of heat conductive resin sheet)
The heat conductive resin sheet of the present invention can be produced, for example, as follows using an organic matrix and the ceramic mixture of the present invention.
First, a ceramic mixture having a concentration of about 59 to 80% by mass, in which a ceramic mixture of the present invention comprising a mixture of spherical alumina particles of a predetermined ratio and flaky hexagonal boron nitride particles is dispersed in a suitable solvent. A suspension of is prepared.
Next, an organic matrix is added to the suspension so that the ceramic mixture is contained at a ratio of 30 to 90% by volume with respect to the total of the organic matrix and the ceramic mixture, thereby preparing a resin composition.
When a curable epoxy resin is used as the main component of the organic matrix, a mixture of the curable epoxy resin, a curing agent for the epoxy resin, and a curing accelerator for the epoxy resin that is used as required is an organic matrix. Become.
When a curable silicone resin is used as the main component of the organic matrix, a mixture of an addition reaction type silicone resin, a silicone-based crosslinking agent, and a curing catalyst becomes an organic matrix.

When spherical alumina particles are used alone as the heat conductive filler, high filling of at least 50% by volume, preferably 80% by volume or more is required in the organic matrix in order to obtain a resin sheet having desired heat conductivity. Become. However, since the ceramic mixture of the present invention is a mixture of spherical alumina particles and flaky hexagonal boron nitride particles, it can exhibit better thermal conductivity with lower filling than when spherical alumina particles are used.
In order to obtain better thermal conductivity, the ceramic mixture is contained in an amount of 30 to 90% by volume based on the total of the organic matrix and the ceramic mixture, but is contained in a ratio of 70 to 80% by volume, or 75 to 80% by volume. By making it, the heat conductive resin sheet which has the further outstanding heat conductivity is obtained.
In the present invention, the volume-based content ratio (volume%, volume fraction) of the ceramic mixture, spherical alumina particles, and flaky hexagonal boron nitride particles is the specific gravity (3.98) of spherical alumina particles, flaky hexagonal It can be determined from the specific gravity (2.27) of the crystalline boron nitride particles and the specific gravity of the various resins used.

The resin composition prepared as described above can contain other additives as required in addition to the organic matrix and the ceramic mixture. Examples of other additives include plasticizers, pressure-sensitive adhesives, reinforcing agents, colorants, heat resistance improvers, and the like.

The resin composition is coated on a releasable film such as a resin film with a release layer with a normal coating machine, etc., and dried by a far-infrared radiation heater, hot air spraying, etc. to form a sheet Is done.
As the release layer, a melamine resin or the like is used. As the resin film, a polyester resin such as polyethylene terephthalate is used.

On the other hand, when the organic matrix is a curable matrix, the resin sheet obtained above is further heated and cured under pressure as necessary to obtain the thermally conductive resin sheet of the present invention. It is done.

The thickness of the heat conductive resin sheet of the present invention thus obtained is preferably in the range of 0.1 to 10 mm, and more preferably in the range of 0.1 to 0.3 mm.
Moreover, in the heat conductive resin sheet of this invention, Preferably heat conductivity is 3 W / m * K or more, More preferably, it is 7 W / m * K or more, More preferably, it is 9 W / m * K or more.
Furthermore, the dielectric breakdown voltage, which is an index of dielectric breakdown characteristics, is preferably 1.0 kV or higher, and more preferably 1.5 kV or higher.
The thermally conductive resin sheet of the present invention may be used by laminating or embedding a sheet-like, fibrous, or mesh-like member on one or both sides and in the sheet for the purpose of improving workability or reinforcing. .

The heat conductive resin sheet thus obtained is peeled off from the releasable film, or in the state where the releasable film is used as a protective film, the shape of the product for use as a heat conductive resin sheet can do.
Moreover, the heat conductive resin sheet of this invention is good also as a structure which further provided the adhesive layer in the upper surface or lower surface of the heat conductive resin sheet, and this improves the convenience at the time of product use.

The heat conductive resin sheet of the present invention is used for transferring heat from heat-generating electronic components such as MPUs, power transistors, and transformers to heat-dissipating components such as heat-dissipating fins and heat-dissipating fans. Used by being sandwiched between heat dissipation components. As a result, heat transfer between the heat-generating electronic component and the heat-dissipating component is improved, and malfunction of the heat-generating electronic component can be significantly reduced.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
The volume-based D50 of the spherical alumina particles and the flaky hexagonal boron nitride particles and the thermal conductivity of the thermally conductive resin sheet obtained in each example were measured by the following methods.

(1) The volume-based D50 of spherical alumina particles and flaky hexagonal boron nitride particles was measured using a particle size distribution meter. In the case of flaky hexagonal boron nitride particles, measurement is performed using a model name “Granurometer 715” manufactured by Cirrus, and in the case of alumina particles, a volume standard using a model name “Multisizer” manufactured by Beckman Coulter. D50 was measured.

(2) Thermal conductivity of thermal conductive resin sheet Measure the thermal diffusivity using the model name "Eye Phase Mobile" manufactured by Eye Phase Co., Ltd., and give the theoretical values of specific heat and density of each resin sheet. It is a value calculated by multiplying.

Examples 1 to 3
(1) Preparation of resin composition containing organic matrix and ceramic mixture As organic matrix, liquid curable epoxy resin [manufactured by Japan Epoxy Resin, trade name “jER828”, bisphenol A type, epoxy equivalent of 184-194 g / eq, 25 A combination of 100 parts by mass with a specific gravity of 1.17] at 100 ° C. and 5 parts by mass of imidazole (trade name “2E4MZ-CN” manufactured by Shikoku Kasei Co., Ltd.) as a curing agent was used. In addition, as a ceramic mixture, spherical alumina particles [made by Showa Titanium, trade name “CB”], scale-like hexagonal boron nitride particles [made by Showa Denko, trade name “UHP-1”, and volume-based D50 is 9 μm. A mixture with an aspect ratio (L: r) of 8: 1 (n = 30)] and a mass ratio of 79:21 was used.
In addition, as the spherical alumina particles, three types having a volume-based D50 of 11 μm (may be described as “A10S”), 28 μm, and 51 μm (may be described as “A50S”) were used, respectively. In addition, as shown in Table 1 below, Example 1 using spherical alumina particles with D50 of 11 μm, Example 2 using Example 50 with spherical alumina particles with D50 of 28 μm, and using spherical alumina particles with D50 of 51 μm are used. Example 3 was designated as Example 3.

100 parts by mass of the ceramic mixture and 45 parts by mass of methyl ethyl ketone (MEK) are added to a stainless steel container for homogenizer (when A50S is used), and the mixture is stirred and mixed with a homogenizer at a rotational speed of 5000 rpm for 2 minutes. A suspension of the mixture was prepared. (Because MEK is used to adjust the viscosity so that it can be applied with an applicator, the amount varies depending on the system. Therefore, the description regarding the amount of MEK is omitted hereinafter.)
Next, the organic matrix is added to the ceramic mixture suspension so that the content of the ceramic mixture in the organic matrix becomes 70% by volume, and the mixture is stirred and mixed again with a homogenizer at a rotational speed of 5000 rpm for 10 minutes. Thus, a resin composition was prepared.

(2) Production of thermally conductive resin sheet After the resin composition was applied on a release film cut to a width of 10.5 cm and a length of 13 cm with an applicator so that the cured film thickness was 500 μm or less, 40 It was allowed to stand for 30 minutes in a dryer set at ° C., and the solvent MEK was evaporated and dried to obtain three kinds of sheet-shaped resin compositions.
Next, these three types of sheet-shaped resin compositions are pressure-bonded for 15 minutes at 120 ° C. and 1 MPa through different release films, respectively, thereby curing the sheet-shaped resin composition and three types of heat. A conductive resin sheet was produced.
The thermal conductivity of the obtained three types of thermally conductive resin sheets was measured (average value of 30 points). The results are shown in Table 1 below.

Examples 4 and 5
In Example 1 (1), spherical alumina particles (supra) [volume-based D50 of 28 μm (Example 4), 51 μm (Example 5)] and scaly hexagonal boron nitride were used as the ceramic mixture. The same operation as in Example 1 was performed except that a mixture of the particles (supra) with a mass ratio of 94: 6 was used and the content of the ceramic mixture was 80% by volume of the whole, and two kinds of heat A conductive resin sheet was produced.
The thermal conductivity of the obtained two types of thermally conductive resin sheets was measured. The results are shown in Table 1 below.

Example 6
In Example 1 (1), as a ceramic mixture, a mixture of spherical alumina particles (supra) [volume-based D50 is 51 μm] and scaly hexagonal boron nitride particles (supra) 94: 6 A heat conductive resin sheet was produced in the same manner as in Example 1 except that the content of the ceramic mixture was 70% by volume of the whole.
The thermal conductivity of the obtained heat conductive resin sheet was measured. The results are shown in Table 1 below.

Example 7
In Example 1 (1), as a ceramic mixture, a mixture of spherical alumina particles (supra) [volume-based D50 is 51 μm] and scaly hexagonal boron nitride particles (supra) 79:21 A heat conductive resin sheet was produced in the same manner as in Example 1 except that the content of the ceramic mixture was 80% by volume of the total.
The thermal conductivity of the obtained heat conductive resin sheet was measured. The results are shown in Table 1 below.

Comparative Examples 1 to 4
(1) Preparation of Resin Composition Containing Organic Matrix and Spherical Alumina Particles In Example 1 (1), instead of the ceramic mixture, spherical alumina particles (supra) [volume-based D50 is 11 μm, 21 μm (“A20S” A suspension of spherical alumina particles was prepared in the same manner as in Example 1 (1) except that only 4 types of 28 μm and 51 μm were used.
In addition, as shown in Table 2 below, an example using a spherical alumina particle having a D50 of 11 μm is Comparative Example 1, an example using a spherical alumina particle having a D50 of 21 μm is a Comparative Example 2, and a spherical alumina particle having a D50 of 28 μm is used. The example used was Comparative Example 3, and the example using spherical alumina particles having a D50 of 51 μm was used as Comparative Example 4.

Subsequently, the same operation as in Example 1 (1) was performed except that an organic matrix was added to the suspension of spherical alumina particles so that the content of the spherical alumina particles in the organic matrix was 80% by volume. And four types of resin compositions were prepared.

(2) Preparation of heat conductive resin sheet Using the four resin compositions obtained in (1) above, the same operation as in Example 1 (2) was performed to prepare four heat conductive resin sheets. .
The thermal conductivity of the obtained four types of thermally conductive resin sheets was measured. The results are shown in Table 2 below.

As can be seen from Tables 1 and 2, the thermal conductivity in the thermally conductive resin sheets of Examples 1 to 7 of the present invention obtained using the ceramic mixture as the thermally conductive filler is determined by the amount of the ceramic mixture filled. They are in the range of 3.4 to 10.2 W / m · K at 70 volume% and 80 volume%, respectively.
On the other hand, the heat conductive resin sheet of the comparative example in which only 80% by volume of spherical alumina particles are filled as the heat conductive filler has a heat conductivity in the range of 3.8 to 4.7 W / m · K. is there.

When the thermal conductivity of the thermally conductive resin sheet of the example and the comparative example when the volume-based D50 of the spherical alumina particles is 28 μm and 51 μm is compared, the thermal conductivity is obtained when the volume-based D50 of the spherical alumina particles is 28 μm. The rates are 5.9 W / m · K and 5.3 W / m · K in Examples 2 and 4, respectively, while 3.3 W / m · K in Comparative Example 3, which is higher than that in Examples. Pretty low.

Further, when the volume-based D50 of the spherical alumina particles is 51 μm, the thermal conductivities are 9.1 W / m · K and 10.2 W / m · K in Examples 3 and 7, respectively. In Example 4, it is 4.7 W / m · K, which is significantly lower than that of the example.
From this, it can be seen that the ceramic mixture of the present invention, which is a mixture of spherical alumina particles and flaky hexagonal boron nitride particles, is superior as a thermally conductive filler compared to the spherical alumina particles alone.

Comparative Example 5
(1) Preparation of resin composition containing organic matrix and spherical alumina particles A suspension of spherical alumina particles was prepared in the same manner as in Comparative Example 2 (1).
Next, an operation similar to that in Comparative Example 2 (1) was performed except that an organic matrix was added to the suspension of spherical alumina particles so that the content of the spherical alumina particles in the organic matrix was 70% by volume. And a resin composition was prepared.

(2) Preparation of heat conductive resin sheet Using the resin composition obtained in (1) above, the same operation as in Comparative Example 2 (2) was performed to prepare a heat conductive resin sheet. The thermal conductivity of the obtained heat conductive resin sheet was measured. The results are shown in Table 3 below.

Comparative Example 6
(1) Preparation of resin composition containing organic matrix and flaky hexagonal boron nitride particles In Example 1 (1), instead of the ceramic mixture, flaky hexagonal boron nitride particles (supra) [volume-based D50 Was used in the same manner as in Example 1 (1) except that only 9 μm] was used.
Subsequently, the same operation as in Example 1 (1) was performed except that an organic matrix was added to the suspension of spherical alumina particles so that the content of the spherical alumina particles in the organic matrix was 70% by volume. And a resin composition was prepared.

(2) Production of thermally conductive resin sheet Using the resin composition obtained in (1) above, the same operation as in Example 1 (2) was performed to produce a thermally conductive resin sheet. The thermal conductivity of the obtained heat conductive resin sheet was measured. The results are shown in Table 4 below.

As can be seen from Tables 3 and 4, it can be seen that the improvement in thermoelectric conductivity is hardly seen in the case of using a combination of spherical alumina with a small particle diameter instead of boron nitride or a filler using only boron nitride. It was.

Comparative Example 7
In Example 3, as the ceramic mixture, a mixture having a mass ratio of spherical alumina particles (supra) [volume-based D50 of 51 μm] and scaly hexagonal boron nitride particles (supra) is 97: 3, A heat conductive resin sheet was produced in the same manner as in Example 1 except that the content of the ceramic mixture was 70% by volume of the whole.
The thermal conductivity of the obtained heat conductive resin sheet was measured. The results are shown in Table 5 below.

As can be seen from Table 5, it was found that the thermal conductivity of the boron nitride having a mass ratio of less than the lower limit of 3% by mass is less improved.

Examples 8 to 14 and Comparative Examples 8 to 11
(1) Preparation of resin composition containing organic matrix and ceramic mixture As organic matrix, liquid curable epoxy resin [manufactured by Japan Epoxy Resin, trade name “Epicoat 828”, bisphenol A type] 100 parts by mass, and curing agent Of 1-cyanoethyl-2-methylimidazole (manufactured by Shikoku Kasei Co., Ltd., trade name “Cureazole 2PN-CN”) was used in combination. Moreover, the particles described in Table 6 below were used as the ceramic mixture.

To the stainless steel container for homogenizer, add 101 parts by mass of the ceramic mixture (formulation shown in Table 7 below) and methyl ethyl ketone (MEK), and stir and mix for 2 minutes with a homogenizer at a rotational speed of 5000 rpm. A suspension was prepared.
Next, the organic matrix is added to the suspension of the ceramic mixture so that the content of the ceramic mixture in the organic matrix becomes the amount shown in Table 6 below, and the suspension is again mixed with a homogenizer at a rotational speed of 5000 rpm. The resin composition was prepared by stirring and mixing for a minute.

(2) thermal conductivity in a solution of Preparation The thermosetting resin composition of the resin sheet, the same volume as the thermosetting resin composition, D _R particulate silicon nitride filler 5μm {SN-7: Electrochemical Industry Co., Ltd.} was added and premixed. This preliminary mixture was further kneaded with three rolls to obtain a compound in which the filler was uniformly dispersed in the solution of the thermosetting resin composition.
Next, the above compound was applied onto a release treatment surface of a polyethylene terephthalate sheet having a single-sided release treatment with a thickness of 100 μm by a doctor blade method, followed by a heat drying treatment at 110 ° C. for 15 minutes. A stage-state thermally conductive resin sheet was prepared.
Next, the said heat conductive resin sheet was heated at 120 degreeC for 1 hour, and 160 degreeC for 3 hours, and the heat conductive resin sheet was produced.
The thermal conductivity of the obtained heat conductive resin sheet was measured in the same manner as in Example 1 (30-point average value). The results are shown in Table 6 below.

Evaluation of dielectric breakdown characteristics of thermally conductive resin sheet A thermally conductive resin sheet was bonded between a copper plate (40 × 40 × 5 mm ³ ) and an aluminum plate (30 × 30 × 5 mm ³ ) with an adhesive area of 30 × 30 mm ² . A test piece was prepared. The test piece was measured according to the withstand voltage test method of JIS C 2110 with a specified voltage of 1.5 kV and a specified time of 60 seconds. The case where dielectric breakdown did not occur was evaluated as acceptable (◯), and the case where dielectric breakdown occurred was determined as unacceptable (x).
In addition, according to Example 1, the heat conductive resin sheet was variously produced with the mixing | blending shown in Table 7 below. Moreover, it carried out similarly to Example 1, and also measured the heat conductivity of the heat conductive resin sheet. The results are shown in Table 7 below.

The ceramic mixture of the present invention is useful as a thermally conductive filler. And the heat conductive resin sheet of this invention obtained using this heat conductive filler is the heat dissipation components, such as a heat dissipation fin and a heat dissipation fan, for example, heat from heat generation electronic components, such as MPU, a power transistor, and a transformer. Can be used for heat transfer to. Moreover, since the dielectric breakdown characteristics of the heat conductive resin sheet are good, it is possible to sufficiently cope with the thinning of the heat conductive resin sheet accompanying the downsizing of electronic devices and the like.

10 ... scale-like hexagonal boron nitride particles L ... major axis r ... thickness

Claims

A mixture of spherical alumina particles having a volume-based D50 of 10 to 55 μm and flaky hexagonal boron nitride particles having a volume-based D50 of 30 μm or less, wherein the content ratio of the flaky hexagonal boron nitride particles is 5 Ceramic mixture, characterized in that it is ˜30% by mass.
2. The ceramic mixture according to claim 1, wherein the volume-based D50 of the flaky hexagonal boron nitride particles is 5 to 30 μm.
A ceramic-containing thermally conductive resin sheet obtained by molding a resin composition containing 10 to 70% by volume of an organic matrix and 30 to 90% by volume of the ceramic mixture according to claim 1.
The ceramic-containing thermally conductive resin sheet according to claim 3, wherein the volume-based D50 of the spherical alumina is 3 to 7 times the volume-based D50 of the flaky hexagonal boron nitride particles.