JPH09321191A - Heat conductive high polymer body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To be excellent in heat conductivity and insulation property and maintain softness and impact-resistant characteristics derived from a high polymer material by a method wherein surface of heat conductive filler particles are coated with a ceramic based material. SOLUTION: This embodiment can be obtained by containing heat conductive filler particles in a high polymer material composed of silicone rubber. In particular, surfaces of the heat conductive filler particles are coated with a ceramic based material. The ceramic based material contains not only silica, alumina, etc., but also various metallized compounds and their reaction products, etc. A sol-gel method is used as a surface coating method of the heat conductive filler particles, and then an insulation property is given, and by using a carbon based filler, the heat conductivity can be enhanced more. Further, by using silicone rubber, insulation, softness and impact-resistant properties can be kept.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat conductive polymer molded article excellent in heat conductivity, insulation and flexibility, which is used for heat dissipation of IC substrates, transistors and the like used in electronic equipment. It is about.

[0002]

2. Description of the Related Art Conventionally, in an electronic device such as an IC substrate and a transistor, heat generated during use shortens the life of parts of the electronic device.
A heat dissipation sheet or the like having excellent thermal conductivity is sandwiched between parts to promote heat dissipation. Examples of the heat dissipation sheet or the like include a polymer material such as an elastomer, a thermoplastic resin, and a thermosetting resin, and a thermally conductive filler having a high thermal conductivity and short fibers (BeO, BN, MgO, Al ₂ O ₃ , SiC, A).
Polymer moldings in which 1N, SiN, etc.) are dispersed are used.

[0003]

However, in order to obtain a high thermal conductivity in the above polymer molded article, a large amount of a heat conductive filler or the like must be added. There is a problem that the original properties of the material, such as flexibility and impact resistance, are significantly reduced. Therefore, it is conceivable to use a carbon-based filler (carbon black, graphite, carbon fiber, expanded graphite, etc.) having a higher thermal conductivity than the above-mentioned thermally-conductive filler, etc. Since not only the property but also the conductivity is high, the polymer molded body containing them is deteriorated in the electrical characteristics (insulating property) and cannot be used as a heat dissipation material for electronic devices.

The present invention has been made in view of the above circumstances, and is excellent in heat conductivity and insulation, and the heat and the flexibility derived from the polymer material and the impact resistance are maintained. The purpose thereof is to provide a conductive polymer molded body.

[0005]

In order to achieve the above object, the heat conductive polymer molding of the present invention has a high heat conductivity obtained by containing heat conductive filler particles in a polymer material. It is a molecular molded body, and has a structure in which the surface of the thermally conductive filler particles is surface-coated with a ceramic material.

In the present invention, the "ceramic material" is a general term that includes not only ceramic materials such as silica and alumina but also metal alkoxides, alkoxides, various metal compounds and reaction products thereof.
It is also used to include the precursor thereof.

That is, the inventor of the present invention, in order to obtain a polymer molded article having excellent thermal conductivity and excellent insulation,
A series of studies were repeated. Then, in the course of that research, they found out that the conventional thermally conductive particles have the following characteristics.

That is, as shown in FIG. 1, in the case of electrically conductive particles, a substance group 1 used as thermally conductive filler particles
The thermal conductivity and the electrical conductivity of each substance are specific values, and the thermal conductivity and the electrical conductivity are in direct proportion, and the filler having excellent thermal conductivity is also excellent in the electrical conductivity. Therefore, the polymer molded body containing the filler having excellent thermal conductivity also has excellent conductivity and cannot be used as a heat dissipation material for electronic devices. Therefore, in order to obtain a thermally conductive polymer molded body having excellent thermal conductivity and excellent insulating properties, the surface of the thermally conductive filler particles should be made of a ceramic material having an insulation property superior to that of the thermally conductive filler particles. The inventors have found that it is sufficient to include a material surface-coated with a material in a polymer material, and arrived at the present invention.

By using the sol-gel method as the surface coating method for the thermally conductive filler particles, the insulating property can be imparted.

Further, by using a carbon-based filler as the heat conductive filler, the heat conductivity can be further improved.

Further, by using silicone rubber as the polymer material, it is possible to maintain insulation, flexibility and impact resistance.

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described.

The heat conductive polymer molded article of the present invention is a molded article obtained by using a heat conductive filler particle whose surface is coated with a ceramic material and a polymer material.

Examples of the ceramic material include tetramethoxysilane, tetraethoxysilane, tetraphenoxysilane, trimethoxy (methyl) silane, triethoxy (methyl) silane, trimethoxy (phenyl) silane, triethoxy (phenyl) silane, triethoxy (vinyl). Silane, γ-chloropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-
(Β-aminoethyl) -γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ
-Methacryloxypropyltrimethoxysilane, dihydroxydiphenylsilane, dimethoxydimethylsilane, diethoxydimethylsilane, dimethoxy (methyl)
Silane, diethoxy (methyl) silane, diethoxy (methyl) vinylsilane, dimethoxydiphenylsilane, diethoxydiphenylsilane, [N- (β-aminoethyl) -γ-aminopropyl] (dimethoxy) methylsilane, γ-glycidoxypropyl ( Silicates such as dimethoxy) methylsilane, γ-methacryloxypropyl (dimethoxy) methylsilane, methoxytrimethylsilane, ethoxytrimethylsilane, ethoxy (dimethyl) vinylsilane, sodium methoxide, sodium ethoxide, sodium-tert-butyrate, potassium methoxide, Potassium-tert-butoxide, magnesium diethoxide, aluminum triethoxide, aluminum triisopropoxide, aluminum tri-
n-butoxide, aluminum tri-sec-butoxide, aluminum tri-tert-butoxide, trimethoxyborane, triethoxyborane, tetraethylorthotitanate, chlorotriisopropylorthotitanate, tetra-n-propylorthotitanate, titanium tetraiso Propoxide, titanium tetra-n-butoxide, dibutyldimethoxytin, trimethoxy arsenic, triethoxy arsenic, tri-n-propoxy arsenic, tri-n-butoxy arsenic and other alkoxides, boron trifluoride-diethyl ether complex, bromo ( (Dimethyl sulfide) copper (I), sodium hexachlororhodium (III) dihydrate, potassium tetrachloropalladium (II) acid, sodium hexachloroiridium (IV) acid hexahydrate, hexachlorooi Examples thereof include sodium rhidium (III) dihydrate, ammonium hexafluorophosphate, potassium hexafluorophosphate, palladium (II) acetate, and other complexes and metal compounds. These may be used alone or in combination of two or more. Of these, aluminum or silicon alkoxides are preferable from the viewpoints of high thermal conductivity and affinity with silicone rubber.

The thermally conductive filler particles include carbonaceous fillers such as graphite (high-purity graphite and expanded graphite) and carbon fibers, boron nitride (BN), aluminum nitride (AlN), mica, beryllium oxide. (BeO),
Aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), zinc oxide (ZnO), titanium oxide (TiO 2
₂ ), inorganic materials such as silica (SiO ₂ ), metal oxides, metal materials such as nickel (Ni), etc. are used. These may be used alone or in combination of two or more.
Among them, graphite that is excellent in heat conductivity, lightweight and soft is suitable.

The particle size of such heat conductive particles is
In order to improve handleability during production, for example, in the case of high-purity graphite (carbon content is 99% or more), 6 to 100 μm is preferable, and 10 to 40 μm is more preferable. Further, in the case of expanded graphite, it is preferably 20 to 600 μm, more preferably 40 to 400 μm. In the case of carbon fibers, the aspect ratio (length / diameter) is preferably 5 to 50, more preferably 7 to 30.

Further, as the above-mentioned polymer material, polypropylene, butyl rubber, polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinylcarbazole, polymethylmethacrylate, isoprene rubber, chloroprene rubber, silicone rubber, nylon, modified polyphenylene ether, poly Oxyethylene, polyethylene terephthalate, polyurethane, polybisphenol carbonate, silicone rubber, polyethylene, polytetrafluoroethylene, phenol-curable epoxy resin, epoxy resin such as silicone modified epoxy resin, synthetic resin such as phenol resin and silicone resin, or 2 liquids An adhesive such as a curable epoxy adhesive is used. These may be used alone or in combination of two or more. Of these, silicone rubber, which has high dielectric breakdown strength and excellent flexibility, is preferable.

The heat conductive polymer molded article of the present invention can be produced using these materials, for example, as follows. That is, first, the surface of the thermally conductive filler particles is surface-coated with a ceramic material. As the surface coating method, for example, a dilute solution prepared by dissolving or diluting a ceramic material with a solvent such as propanol, ethanol, or methanol, and adding water to hydrolyze the ceramic material (for example, metal alkoxide). A method (sol-gel method) of adding thermally conductive filler particles to a sol, drying and heating is used. By using this surface coating treatment method, as shown in FIG. 1, it is possible to obtain the thermally conductive filler particles 7 having excellent insulating properties while having the excellent thermal conductivity of the particles themselves. The amount of the ceramic material blended is 1 × 10 ⁻³ to 1 × with respect to 1 cm ^{3 of the} heat conductive filler so that a coating layer having a predetermined thickness is formed on the heat conductive filler particles. It is preferably set in the range of 10 ^-2 mol. Then, the thermally conductive filler particles are added to the dilute sol to promote the polycondensation of the sol on the surface of the thermally conductive filler particles, followed by drying and heating (calcination) to fix the acid / hydroxide. This reaction can be represented by the following formula (1). And
The surface of the thermally conductive filler particles is surface-coated with the ceramic material (final product and precursor) obtained by this reaction. At this time, if the unreacted precursor remains, the acid as a catalyst also remains, and this acid may foam during molding. The surface of the agent particles is preferably coated.

[0018]

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In addition to the surface coating method, a conversion method or a hybridization method may be used. However, the sol-gel method is preferable because a uniform thin film can be easily formed.

Next, the surface-treated thermally conductive filler is dispersed in the polymer material matrix using a mill or the like. In addition, it is preferable that the surface-coated thermally conductive filler particles are uniformly dispersed. That is, as shown in FIG. 2, when many of the polymer materials 2 are in a state where the surface-coated thermally conductive filler particles 3 are in contact with each other, a curve 4 shown in FIG. 3 is obtained, which is sufficient. There is a possibility that the insulating property cannot be secured before obtaining the thermal conductivity (sufficient addition amount). On the other hand, in the case where the thermally conductive filler particles 3 subjected to the surface coating are not in a state of being in contact with each other and uniformly dispersed, a curve 5 shown in FIG. 3 is obtained, and sufficient thermal conductivity ( Since a sufficient addition amount) is obtained, the thermal conductivity can be easily controlled by adjusting the addition amount.

In order to uniformly disperse the surface-coated thermally conductive filler particles 3, the volume fraction of the surface-coated thermally conductive filler particles 3 [surface-coated thermally conductive filler particles 3 3 volume / (volume of polymer material 2 + volume of surface-coated thermally conductive filler particles 3)], 0.05
It is preferable to set it in the range of 0.23. More preferably, it is 0.1 to 0.16. That is, 0.05
If it is less than, there is a possibility that high thermal conductivity may not be obtained,
If it exceeds 0.23, the insulating property cannot be ensured and the flexibility may be lost.

In this way, the desired thermally conductive polymer molded body 6 is obtained by curing and molding the polymer material in which the thermally conductive filler particles 3 having the surface coating treatment dispersed therein, by a conventionally known appropriate method. Can be obtained.

In the heat conductive polymer molding of the present invention, since the above-mentioned special heat conductive filler particles are dispersed in a polymer matrix made of a polymer material, the heat conductivity of the particles themselves and the ceramic The insulating properties of the system materials are exhibited together. Therefore, it is excellent in both insulation and thermal conductivity. Furthermore, since a filler material having high thermal conductivity can be selected, it is not necessary to use a large amount of filler having low thermal conductivity, and the flexibility and impact resistance of the polymer material serving as the matrix are impaired. It has the advantage of never.

Next, examples will be described together with comparative examples.

[0025]

Examples 1 to 3 Aluminum triisopropoxide 3
After dissolving 8 g in 200 g of 2-propanol at 80 ° C., 1.7 g of 69% nitric acid and 6.7 g of distilled water were stirred.
A mixture of 2-propanol and 200 g of 2-propanol was added dropwise to prepare an alumina sol. Then, high-purity graphite (manufactured by Nippon Graphite Co., Ltd., J-SP, average particle size 10 μm) was added to this alumina sol.
m, carbon content 99.5%) 100 g (44.4 cm ³ )
Was charged and stirred at room temperature for 2 hours to obtain a slurry mixture. The slurry mixture was dried at 150 ° C. for 5 hours,
Then, the partially solidified material was crushed and further vacuum dried at 150 ° C. for 3 hours to obtain high-purity graphite whose surface was coated with alumina gel. Then, the high-purity graphite surface-coated with the alumina gel was added to a liquid silicone rubber (TSE-3033A and TSE-3033B manufactured by Toshiba Silicone Co., which were mixed at a ratio of 1: 1) to give the volume fractions shown in Table 1 below. And mix evenly with a mill to obtain 100
The film was heat-cured at 15 ° C. for 15 minutes to prepare a 50 × 50 × 2 mm sheet-shaped thermally conductive polymer sheet.

[0026]

Examples 4 to 7 and Comparative Examples 1 to 4 In the same manner as in Example 1, slurry mixtures were obtained. After drying this slurry-like mixture at 150 ° C. for 5 hours, a partially solidified product was crushed and vacuum dried at 150 ° C. for 3 hours to obtain a powder having a heating rate of 10
It was heated at 0 ° C./h to 650 ° C., kept at that temperature for 2 hours and then cooled to obtain high-purity graphite surface-coated with alumina. Then, the high-purity graphite surface-coated with alumina was used as liquid silicone rubber (TS manufactured by Toshiba Silicone Co., Ltd.
E-3033A and TSE-3033B were mixed at a ratio of 1: 1) so that the volume fractions shown in Tables 2 and 3 below were obtained, uniformly mixed by a mill, and heated at 100 ° C. for 15 minutes. It was cured to prepare a 50 × 50 × 2 mm sheet-shaped heat conductive polymer sheet.

[0027]

Examples 8 to 10 An alumina sol was prepared in the same manner as in Example 1. 100 g of carbon fiber (10 μm × 70 μm, aspect ratio: 7) manufactured by Petka Co., Ltd. in this alumina sol
(48.5 cm ³ ) was charged and the mixture was stirred at room temperature for 2 hours to obtain a slurry mixture. This slurry mixture is heated to 150 ° C.
For 5 hours, then vacuum dry at 150 ° C for 3 hours,
Then, the temperature was raised to 650 ° C. at a heating rate of 100 ° C./h, and the temperature was maintained for 2 hours and cooled to obtain a carbon fiber surface-coated with alumina. Then, the carbon fiber surface-coated with alumina was mixed with liquid silicone rubber (TSE-3033A and TSE-3033B manufactured by Toshiba Silicone Co., Ltd. in a ratio of 1: 1) in a volume fraction shown in Table 4 below. And mix evenly with a mill, 100 ℃
Was heat-cured for 15 minutes to prepare a 50 × 50 × 2 mm sheet-like thermally conductive polymer sheet.

[0028]

[Comparative Examples 5 to 11] High-purity graphite (J-SP, manufactured by Nippon Graphite Co., average particle size 10 µm, carbon content 99.5%) which is not surface-coated is used as liquid silicone rubber (TSE manufactured by Toshiba Silicone Co., Ltd.). -3033A and TSE-3033B were mixed at a ratio of 1: 1) to obtain the volume fraction shown in Table 5 below, and uniformly mixed by a mill to obtain 100
The film was heat-cured at 15 ° C. for 15 minutes to prepare a 50 × 50 × 2 mm sheet-shaped thermally conductive polymer sheet.

[0029]

Comparative Examples 12 to 18 Alumina (AS-30 manufactured by Showa Denko KK) which is not surface-coated is a liquid silicone rubber (TSE-3033A and TSE manufactured by Toshiba Silicone Co., Ltd.).
-3033B mixed at a ratio of 1: 1) to a volume fraction shown in Table 6 below, uniformly mixed by a mill, and heat-cured at 100 ° C. for 15 minutes to obtain 50 × 50.
A sheet-shaped heat conductive polymer sheet having a size of 2 mm was prepared.

The heat conductivity and electric conductivity of the heat conductive polymer sheets of Examples 1 to 10 and Comparative Examples 1 to 18 were measured, and the results are shown in Tables 1 to 6 below. It was In addition, each measuring method is as follows.

[Thermal Conductivity] The thermal conductivity was measured at a measurement temperature of 60 ° C. by a steady method (guarded hot plate method).

[Electrical conductivity] A voltage (0.1 to 100 V) is applied in the volume direction using KEITHLEY237,
It was calculated from the current value at that time.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

[0037]

[Table 5]

[0038]

[Table 6]

Comparative Examples 3, 4, 10 and 11
The softness of the heat conductive polymer molded product was examined for the products, 17, and 18 by touch, but they were poor in flexibility.

From the above results, all of the products of Examples 1 to 10 are excellent in thermal conductivity and insulation. Moreover, since the blending amount of the thermally conductive filler particles is relatively small,
The flexibility of the heat conductive polymer molding is not impaired. On the other hand, Comparative Examples 2 to 4 contained a large amount of the surface-coated thermally conductive filler, and thus exhibited excellent thermal conductivity, but also increased electrical conductivity and ensured insulation. Not done. Furthermore, Comparative Examples 5 to 11 have excellent thermal conductivity because the thermally conductive filler particles (high-purity graphite) that have not been surface-coated are dispersed in the polymer material. Has not been secured. Comparative Example 1
2 to 18 products use the ceramic material itself (alumina) used for the surface coating treatment as the thermally conductive filler particles, but sufficient thermal conductivity is not obtained, and those added in a large amount, The flexibility of the heat conductive polymer molding is also impaired.

Then, Examples 4 to 7 and Comparative Examples 1 to 4
The curve plotting the volume fraction and the electrical conductivity for each of the above is A, the curve plotted in the same manner as the curve A for each of the Comparative Examples 5-11 is B, and the curve A for each of the Comparative Examples 12-18. The curve plotted in the same manner as above is designated as C and is shown in FIG.

From the above FIG. 4, the surface-coated thermally conductive filler particles (high-purity graphite surface-coated with alumina)
The curve A in which is dispersed in a polymer material has a volume fraction of 0.
A heat conductive polymer molding having low electric conductivity (excellent in insulation) can be obtained up to 16. However, when the volume fraction exceeds 0.17, the electric conductivity sharply rises and the insulation cannot be secured.

Further, the curve B in the case where the thermally conductive filler particles (high-purity graphite) not surface-treated are dispersed in the polymer material, the curve B shows a slight increase in the volume fraction and an increase in the electrical conductivity. As a result, insulation cannot be secured.

Further, in the curve C in which the ceramic material (alumina) used for the surface coating treatment is dispersed in the polymer material, the electric conductivity is sufficiently low and the insulating property is secured. However, from Table 6, when the volume fraction is small, the thermal conductivity is insufficient, and when the volume fraction is large, the flexibility of the heat conductive polymer molding is insufficient.

[0045]

As described above, in the heat conductive polymer molding of the present invention, the heat conductive filler particles surface-coated with the ceramic material are dispersed in the polymer matrix made of the polymer material. Therefore, both the excellent thermal conductivity of the thermally conductive filler particles and the insulating property of the ceramic material are exhibited. Therefore, the heat conductive polymer molding of the present invention is excellent in heat conductivity and insulation. Furthermore, since a filler material having high thermal conductivity can be selected, it is not necessary to use a large amount of low thermal conductivity filler to obtain a predetermined thermal conductivity. And impact resistance is not impaired.

In particular, in the heat conductive polymer molding of the present invention, the heat conductive filler particles are surface-coated by the sol-gel method, whereby a uniform thin film can be easily formed on the surface of the heat conductive filler particles. It is possible to obtain a heat-conductive polymer molded article that can be manufactured in accordance with the above method and has excellent insulation.

By using a carbon-based filler as the heat-conductive filler, it is possible to obtain a heat-conductive polymer molded body having more excellent heat conductivity.

Furthermore, by using silicone rubber as the polymer material, it is possible to obtain a heat conductive polymer molded body having excellent flexibility and impact resistance.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between electrical conductivity and thermal conductivity of a general substance.

FIG. 2 is an explanatory view showing an embodiment of thermally conductive filler particles in a polymer material.

FIG. 3 is a diagram showing the amount of electrically conductive filler particles added to a polymer material and the electrical conductivity.

FIG. 4 is a diagram showing a relationship between volume fraction and electric conductivity in the case where high-purity graphite surface-treated with alumina, high-purity graphite, and alumina are dispersed in silicone rubber.

Claims (4)

[Claims] 1. A heat conductive polymer molding obtained by incorporating heat conductive filler particles in a polymer material, wherein the surface of the heat conductive filler particles is surface-coated with a ceramic material. A heat-conductive polymer molded article characterized by being provided. 2. The heat conductive polymer molding according to claim 1, wherein the surface coating treatment is a sol-gel method. 3. The heat conductive polymer molded article according to claim 1, wherein the heat conductive filler is a carbon-based filler. 4. The heat conductive polymer molded article according to claim 1, wherein the polymer material is silicone rubber.