JP2012054312A - Heat dissipation sheet and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat dissipation sheet having superior thermal conductivity and heat resistance when compared with prior art.SOLUTION: Electron beam (EB) cross-linking olefin-based resin and a thermally conductive resin composition are compression molded and then cross-linked by EB irradiation to produce a heat dissipation sheet. The thermally conductive resin composition preferably contains cross-linking assistant and/or flame retardant. When the heat dissipation sheet is produced, the thermally conductive resin composition is prepared and compression molded, and then cross-linked by EB irradiation.

Description

  The present invention relates to a heat radiating sheet and a method for producing the same, and more particularly to a heat radiating sheet that is excellent in thermal conductivity and can effectively dissipate heat and a method for producing the same.

  Conventionally, heat generated in various semiconductor elements, power supplies, light sources, components, etc. in electrical and electronic equipment is effectively dissipated to the outside, or the temperature of components is lowered by transferring heat to heat dissipation members such as heat sinks. For this purpose, a heat dissipating sheet is arranged.

  As such a heat dissipation sheet, for example, in Patent Document 1, boron nitride powder is dispersed and blended as a thermally conductive filler in an organic matrix material, and the boron nitride powder contains secondary aggregate particles having a particle size of 50 μm or more. A thermally conductive sheet containing 1 to 20% by weight is disclosed. In addition, this type of sheet is a mixed composition in which a thermally conductive filler is dispersed and blended in an organic matrix material, press molding method, injection molding method, extrusion molding method, calendar molding method, roll molding method, doctor blade. It is also known that it is produced by molding into a sheet shape by a known molding method such as a molding method.

JP 2003-060134 A (Claims etc.)

  As the performance of electric and electronic devices in recent years increases, the amount of heat generated inside these devices continues to increase, and there is a need for heat dissipation sheets that can dissipate such heat more efficiently. Yes. Moreover, in addition to being excellent in thermal conductivity, such a heat dissipation sheet is also required to have heat resistance.

  Therefore, an object of the present invention is to provide a heat radiating sheet having superior thermal conductivity and excellent heat resistance as compared with the conventional art.

  As a result of intensive studies, the inventor uses an electron beam (EB) cross-linked olefin resin as a resin component, and uses a compression molding technique as a molding method, thereby obtaining a heat dissipation sheet that can solve the above problems. As a result, the present invention has been completed.

  That is, the heat dissipation sheet of the present invention is characterized in that a heat conductive resin composition containing an electron beam cross-linking olefin resin and a heat conductive filler is compression-molded and cross-linked by electron beam irradiation. Is.

  In this invention, it is preferable that the said heat conductive resin composition contains a crosslinking adjuvant. Moreover, it is preferable that the said heat conductive resin composition contains a flame retardant. Furthermore, as the electron beam cross-linking olefin resin, an ethylene-α-olefin-nonconjugated diene terpolymer can be suitably used. Furthermore, it is preferable that the said heat conductive resin composition contains 10-1000 mass parts of said heat conductive fillers with respect to 100 mass parts of said electron beam cross-linking type olefin resins.

  In addition, the manufacturing method of the heat dissipation sheet of the present invention is characterized in that, in manufacturing the heat dissipation sheet of the present invention, the heat conductive resin composition is prepared, compression-molded, and then crosslinked by electron beam irradiation. To do.

  According to the present invention, by adopting the above-described configuration, it is possible to realize a heat radiating sheet having superior thermal conductivity and excellent heat resistance as compared with the conventional one.

It is explanatory drawing which shows the formation process of the thermal radiation sheet | seat of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The heat-dissipating sheet of the present invention is obtained by compression-molding a heat conductive resin composition containing an electron beam (EB) cross-linked olefin resin and a heat conductive filler and cross-linking it by electron beam irradiation.

  Since the olefin resin is a thermoplastic resin, it is inherently inferior in heat resistance. However, in the present invention, by using an EB-crosslinking type olefin resin, it is crosslinked by EB irradiation after molding. Thus, it is possible to obtain a heat dissipation sheet with improved heat resistance. In addition, the olefin resin has a merit that moldability is good. Furthermore, in the present invention, it is possible to obtain a heat radiating sheet having desired properties while maintaining good thermal conductivity by using a compression molding technique instead of the conventional general extrusion molding. It is a thing.

  Specific examples of the EB cross-linked olefin resin used in the present invention include polyethylene, ethylene-α-olefin-nonconjugated diene terpolymer, ethylene-vinyl acetate copolymer (EVA), butadiene rubber, Examples include isoprene rubber and styrene-butadiene rubber (SBR). Among them, an ethylene-α-olefin-nonconjugated diene terpolymer is preferable.

  As the α-olefin of the ethylene-α-olefin-nonconjugated diene terpolymer, propylene is usually used, but 1-butene, 1-pentene, 3-methyl-1-butene, etc. may be used. . Examples of non-conjugated dienes include dicyclopentadiene, ethylidene norbornene, vinyl norbornene, 1,4-hexadiene, 1,5-octadiene, and the like. Specific examples of such ethylene-α-olefin-nonconjugated diene terpolymers include EPDM (ethylene propylene diene terpolymer). As the ethylene-α-olefin-nonconjugated diene terpolymer, an oil-extended ethylene-α-olefin-nonconjugated diene terpolymer obtained by adding an oil component such as paraffin oil is used. May be. Further, when the oil-extended ethylene-α-olefin-nonconjugated diene terpolymer is used, an oil component may be further added and used later. Furthermore, without using an oil-extended ethylene-α-olefin-nonconjugated diene terpolymer, a mixture of an ethylene-α-olefin-nonconjugated diene terpolymer and an oil component may be used. Good. Specific commercial examples of such an ethylene-α-olefin-nonconjugated diene terpolymer include Mitsui EPT manufactured by Mitsui Chemicals.

  The heat conductive filler is not particularly limited as long as it has heat conductivity, and a conductive filler, an insulating filler, or the like can be used. Examples of the conductive filler include metal fillers such as copper, silver, iron, aluminum, and nickel; metal alloy fillers such as titanium; and carbon-based fillers such as carbon. Moreover, the surface of the inorganic filler particles coated with a metal material such as silver or copper, or the surface of the metal filler particles coated with an inorganic material or a carbon material may be used. Examples of the insulating filler include oxides such as alumina, magnesium oxide, beryllium oxide, zinc oxide, and titanium oxide; nitrides such as boron nitride, silicon nitride, and aluminum nitride; carbides such as silicon carbide; diamond and the like Insulating carbon-based fillers; silica powders such as quartz and quartz glass. These thermally conductive fillers may be used alone or in combination of two or more. The content of the thermally conductive filler in the thermally conductive resin composition according to the present invention is preferably 10 to 1000 parts by mass, more preferably 50 to 500 parts by mass with respect to 100 parts by mass of the EB cross-linked olefin resin. Part range.

  The heat conductive resin composition according to the present invention preferably contains a crosslinking aid in addition to the EB cross-linked olefin resin and the heat conductive filler. Thereby, the heat resistance of a thermal radiation sheet can be improved more. The crosslinking aid introduces a crosslinked structure into the resin, and is from the viewpoint of ease of radical polymerization, compatibility with the resin (dispersibility), processing stability for expressing the function by EB irradiation, etc. Selected from. There are no particular limitations on the type of crosslinking aid, but examples include triallyl isocyanurate, triallyl cyanurate, trimethallyl isocyanurate, diallyl monoglycidyl isocyanurate, trimethylolpropane trimethacrylate, ethylene glycol diester. Methacrylate, diallyl phthalate, divinylbenzene, diisopropenylbenzene, N, N′-m-phenylenebismaleimide, polybutadiene and the like can be mentioned. These crosslinking aids may be used alone or in combination of two or more. The content of the crosslinking aid in the thermally conductive resin composition according to the present invention is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts per 100 parts by mass of the EB crosslinked olefin resin. It is the range of mass parts.

  Moreover, it is preferable that the heat conductive resin composition according to the present invention further contains a flame retardant. Thereby, the flame retardance of a heat-radiation sheet can be improved. Use various flame retardants and flame retardant aids such as metal hydroxides such as aluminum hydroxide and magnesium hydroxide, hydrotalcite, melamine cyanurate, phosphorus compounds, zinc borate, halogen compounds as flame retardants Can do. These may be used alone or in combination of two or more. The content of the flame retardant in the thermally conductive resin composition according to the present invention is preferably 10 to 500 parts by mass, more preferably 50 to 400 parts by mass with respect to 100 parts by mass of the EB cross-linked olefin resin. It is a range.

  The heat-radiating sheet of the present invention can be produced by preparing a heat conductive resin composition containing at least an EB cross-linked olefin resin and a heat conductive filler, and compression-molding it, followed by cross-linking by electron beam irradiation. Specifically, the heat radiating sheet of the present invention is manufactured by the above-described material using three steps of material preparation, compression molding, and electron beam irradiation.

<Preparation of material>
First, an EB cross-linked olefin resin and a heat conductive filler are mixed with a mixer to prepare a heat conductive resin composition. If desired, a crosslinking aid, a flame retardant, and other various additives may be added to the heat conductive resin composition. As a method of kneading and mixing the thermally conductive resin composition, a general apparatus such as a roll can be used in addition to a mixer.

<Compression molding>
Next, as shown in FIG. 1, the prepared thermally conductive resin composition 11 is a polyethylene terephthalate (PET) film 12 that has been subjected to a release treatment on one side, and the release treatment surface 12a is a thermally conductive resin. Hold it so that it comes to the composition side. By setting this in a mold and performing compression molding, a molded product can be obtained. Here, the compression molding method is the oldest technology among molding methods of resin products, particularly molding methods of thermosetting resins. The raw material is placed in the space between the upper mold and the lower mold, and the gold molding is performed. This is a method in which the mold itself is heated, pressurized after the raw material is in a molten state, the raw material is spread to the details of the space, and then cooled and solidified. A compression molded product has the advantage of low orientation. The molding conditions for compression molding can be appropriately selected according to the material of the thermally conductive resin composition, but preferably the molding temperature is 80 to 180 ° C. and the molding pressure is 5 to 50 t.

<Electron beam irradiation>
Next, the heat-radiation sheet of the present invention can be obtained by irradiating a molded product obtained by compression molding with an electron beam. As the EB irradiation apparatus, for example, a low energy EB apparatus “LB1023” (curtain type electron beam irradiation apparatus) manufactured by I. Electron Beam Co., Ltd. can be used. The EB irradiation conditions can be appropriately selected according to the compounding material of the heat conductive resin composition, the dimensions of the heat dissipation sheet, and the like. Preferably, the acceleration voltage is 50 to 300 kV, and the irradiation dose is 50 to 400 kGy. And

  The dimensions of the heat-dissipating sheet of the present invention can be appropriately selected according to the application, and are not particularly limited. For example, the dimensions may be 10 mm × 10 mm × thickness 0.2 mm to 150 mm × 150 mm × thickness 2 mm. it can. The heat dissipation sheet of the present invention can be used by being disposed in the vicinity of various semiconductor elements in electric / electronic devices, heat dissipation members such as a power source, a light source, components, and a heat sink.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Preparation of material>
The following blending components were mixed with a mixer according to a conventional method to prepare each heat conductive resin composition of Formulation 1 to Formulation 3.

(Formulation 1)
Resin: 100 parts by mass of EPDM Mitsui EPT 3072 EPM (manufactured by Mitsui Chemicals)
Thermally conductive filler: Zinc oxide LPZINC-11 (manufactured by Sakai Chemical Industry Co., Ltd.) 500 parts by mass,
Flame retardant: Magnesium hydroxide N-6 (Kanjima Chemical Co., Ltd.) 250 parts by mass,
Melamine cyanurate MC-4000 (manufactured by Nissan Chemical Industries Ltd.) 100 parts by mass,
Cross-linking assistant: triallyl isocyanurate (TAIC) (manufactured by Nippon Kasei Co., Ltd.) 1 part by mass

(Formulation 2)
Resin: 100 parts by mass of EPDM Mitsui EPT 3072 EPM (manufactured by Mitsui Chemicals)
Thermally conductive filler: Zinc oxide LPZINC-11 (manufactured by Sakai Chemical Industry Co., Ltd.) 500 parts by mass,
Flame retardant: Magnesium hydroxide N-6 (Kanjima Chemical Co., Ltd.) 250 parts by mass,
Melamine cyanurate MC-4000 (manufactured by Nissan Chemical Industries, Ltd.) 100 parts by mass

(Formulation 3)
Resin: 100 parts by mass of EPDM Mitsui EPT K-9720 (manufactured by Mitsui Chemicals)
Thermally conductive filler: Zinc oxide LPZINC-11 (manufactured by Sakai Chemical Industry Co., Ltd.) 500 parts by mass,
Flame retardant: Magnesium hydroxide N-6 (Kanjima Chemical Co., Ltd.) 250 parts by mass,
Melamine cyanurate MC-4000 (manufactured by Nissan Chemical Industries, Ltd.) 100 parts by mass

<Compression molding>
Using each heat conductive resin composition prepared above, compression molding was performed under the conditions of a molding temperature of 120 ° C. and a molding pressure of 45 t according to the conditions shown in Table 1 and Table 2 below. Specifically, as shown in FIG. 1, the prepared thermally conductive resin composition 11 is a polyethylene terephthalate (PET) film 12 having a release treatment on one side, and the release treatment surface 12a is thermally conductive. The product was sandwiched so as to come to the side of the functional resin composition, set in a mold, and subjected to compression molding to obtain a molded product.

<Electron beam irradiation>
Next, a low energy EB device (manufactured by I. Electron Beam Co., Ltd., model: curtain type electron beam irradiation device “LB1023”) is used for the molded product under irradiation conditions of an acceleration voltage of 165 kV and an irradiation dose of 200 kGy. Electron beams were irradiated to crosslink the molded product to obtain each heat dissipation sheet.

<Evaluation of heat shrinkage>
The aluminum container containing talc was placed in an oven at 250 ° C. and sufficiently heated. A 5 × 5 cm sample was cut out from each obtained heat dissipation sheet, placed in an aluminum container in a 250 ° C. oven, allowed to stand for 3 minutes, and then the sample was taken out. The heat shrinkage rate was calculated from the change in the length of the sample taken out. The heat shrinkage rate is considered to be good if it is within 1.0%.

<Evaluation of thermal conductivity>
The thermal conductivity (λ) of each obtained heat dissipation sheet was calculated based on the equation of λ = αρC using the density (ρ), thermal diffusivity (α), and specific heat capacity (C) of each heat dissipation sheet. . Specific gravity, thermal diffusivity, and specific heat capacity were determined by the following methods.
(1) Specific gravity The specific gravity of each heat dissipation sheet was measured using an electronic hydrometer MD-300S (manufactured by Alpha Mirage Co., Ltd.).
(2) Thermal diffusivity The thermal diffusivity of each heat-dissipating sheet at 25 ° C. was measured using a thermal diffusivity measuring device LFA447 Nanoflash (manufactured by NETZSCH). The measurement direction was perpendicular to each heat dissipation sheet.
(3) Specific heat capacity Based on JIS K 7123, the specific heat capacity in 25 degreeC of each heat radiating sheet was computed with the differential scanning calorimeter EXSTAR6000 (made by Seiko Instruments Inc.).

  As shown in the above table, each of the heat-dissipating sheets of each example obtained by compression-molding a heat-conductive resin composition containing an EB cross-linked olefin resin and a heat-conductive filler and then cross-linking by EB irradiation It is clear that it has good thermal conductivity and excellent heat resistance.

11 Thermal Conductive Resin Composition 12 Release Processed PET Film 12a Release Processed Surface

Claims (6)

  A heat-dissipating sheet, wherein a heat conductive resin composition containing an electron beam cross-linkable olefin resin and a heat conductive filler is compression-molded and cross-linked by electron beam irradiation.   The heat dissipation sheet according to claim 1, wherein the heat conductive resin composition contains a crosslinking aid.   The heat dissipation sheet according to claim 1 or 2, wherein the heat conductive resin composition contains a flame retardant.   The heat radiation sheet according to any one of claims 1 to 3, wherein the electron beam crosslinking olefin-based resin is an ethylene-α-olefin-nonconjugated diene terpolymer.   The heat dissipation sheet according to any one of claims 1 to 4, wherein the heat conductive resin composition includes 10 to 1000 parts by mass of the heat conductive filler with respect to 100 parts by mass of the electron beam cross-linking olefin resin. .   In manufacturing the heat-radiating sheet according to any one of claims 1 to 5, the heat-conductive resin composition is prepared, compression-molded, and then cross-linked by electron beam irradiation. Manufacturing method.

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