Thermal Conductive Sheet and Method for Producing the Same

Abstract

Thermal conductive sheets 11a and 11b containing a non-curing liquid matrix resin (A) and thermal conductive particles (B), wherein the component (A) has a kinematic viscosity at 40 °C of 50 to 10,000 mm 2 / s of an ethylene·α-olefin copolymer (A1) and a kinematic viscosity at 40 °C of 50 to 10,000 mm 2 / s of a mixed oil (A2) of polydecene-1 and an ethylene·α-olefin copolymer, and is at least one selected from the group consisting thereof. With respect to 100 parts by mass of the component (A), the thermal conductive particles of the component (B) contain 400 to 2,800 parts by mass, and are the thermal conductive sheets 11a and 11b in a non-cured state. Thereby, a thermal conductive sheet and a manufacturing method thereof are provided, which have a long pot life (service life) in the raw material stage, eliminate the need for a heat curing process, reduce the manufacturing cost, and can reduce the hardness.

Description

Technical Field

[0001] The present invention relates to a thermally conductive sheet suitable for being interposed between a heat generating part such as an electric or electronic component and a heat sink, and a method for manufacturing the same.

Background Art

[0002] In recent years, the performance improvement of semiconductors such as CPUs has been remarkable, and accordingly, the amount of heat generated has also become enormous. Therefore, a heat sink is attached to the heat generating electronic component, and a thermally conductive silicone grease is used to improve the adhesion between the heat generating body such as a semiconductor and the heat sink. However, when the thermally conductive silicone grease is used for a long time, due to the thermal shock of the semiconductor element, it flows out from the heat radiating part, voids are generated in the heat radiating part, and there is a problem that a so-called pumping out phenomenon occurs. Patent Document 1 proposes a thermally conductive resin in which a surface-modified thermally conductive filler is blended with an α-olefin copolymer having at least two α-olefins having 2 to 12 carbon atoms as a main component and having a crystallinity of 10 or less. Patent Document 2 proposes a flame-retardant silicone rubber composition containing a liquid ethylene-propylene copolymer rubber, an organic peroxide crosslinking agent, and a metal oxide filler. The present inventors have proposed in Patent Document 3 a silicone gel composition and a silicone gel sheet containing an organopolysiloxane capable of addition reaction curing, an unsaturated hydrocarbon compound having one alkenyl group in one molecule, and an addition reaction curing catalyst, and having little oil bleed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the conventional thermal conductive composition has problems such as a short pot life (service life) at the raw material stage, a high manufacturing cost when there is a heat curing process, and a high hardness after curing.

[0005] In order to solve the above-mentioned conventional problems, the present invention provides a thermal conductive sheet with a long pot life (service life) at the raw material stage, which eliminates the need for a heat curing process to reduce the manufacturing cost and can reduce the hardness, and a method for manufacturing the same.

Means for Solving the Problems

[0006] One embodiment of the present invention is a thermal conductive sheet containing a non-curable liquid matrix resin (A) and thermal conductive particles (B), The component (A) is at least one selected from the group consisting of an ethylene·α-olefin copolymer (A1) having a kinematic viscosity at 40°C of 50 to 10,000 mm 2 / s and a mixed oil (A2) of polydecene-1 and an ethylene·α-olefin copolymer having a kinematic viscosity at 40°C of 50 to 10,000 mm 2 / s, Based on 100 parts by mass of the component (A), the thermal conductive particles of the component (B) are contained in an amount of 400 to 2,800 parts by mass, Relates to a thermal conductive sheet in a non-cured state.

[0007] One embodiment of the method of the present invention is a method for manufacturing the above-mentioned thermal conductive sheet, As the non-curable liquid matrix resin (A), at least one selected from the group consisting of an ethylene·α-olefin copolymer (A1) having a kinematic viscosity at 40°C of 50 to 10,000 mm 2 / s and a mixed oil (A2) of polydecene-1 and an ethylene·α-olefin copolymer having a kinematic viscosity at 40°C of 50 to 10,000 mm 2 / s, Based on 100 parts by mass of the component (A), 400 to 2,800 parts by mass of thermal conductive particles (B) are mixed, Relates to a method for manufacturing a thermally conductive sheet that is sheet-molded without including a heat-curing process.

Advantages of the Invention

[0008] The thermally conductive sheet of the present invention is a thermally conductive sheet containing a non-curable liquid matrix resin (A) and thermally conductive particles (B). The component (A) has a kinematic viscosity at 40 °C of 50 to 10,000 mm 2 / s of an ethylene·α-olefin copolymer (A1) and a mixed oil (A2) of polydecene-1 and an ethylene·α-olefin copolymer having a kinematic viscosity at 40 °C of 50 to 10,000 mm 2 / s, and is at least one selected from the group consisting of. For 100 parts by mass of the component (A), the thermally conductive particles of the component (B) contain 400 to 2800 parts by mass. By being in a non-cured state, it has a long pot life (usable period) at the raw material stage, eliminates the need for a heat-curing process, reduces the manufacturing cost, and can provide a thermally conductive sheet with a low hardness and its manufacturing method. Further, the present invention can provide a thermally conductive sheet having a good thermal conductivity and a SHORE OO hardness as a non-silicone thermally conductive sheet.

Brief Description of the Drawings

[0009]

Figure 1

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Figure 7

Embodiments for Carrying Out the Invention

[0010] The present invention relates to a thermally conductive sheet containing a non-curable liquid matrix resin (A) and thermally conductive particles (B). The component (A) and the component (B) are made into a uniformly mixed compound composition and formed into a sheet. The component (A) has a kinematic viscosity at 40°C of 50 to 10,000 mm 2 / s of an ethylene·α-olefin copolymer (A1) and a kinematic viscosity at 40°C of 50 to 10,000 mm 2 / s of a mixed oil (A2) of polydecene-1 and an ethylene·α-olefin copolymer, and is at least one selected from the group consisting thereof. With respect to 100 parts by mass of the component (A), the thermally conductive particles of the component (B) contain 400 to 2800 parts by mass and are in a non-cured state. Due to being in a non-cured state, the pot life (usable period) is long at the raw material stage, and after becoming a product, it becomes a thermally conductive sheet with little risk of changes in hardness and the like. It is preferable that the present invention does not contain a silicone polymer. Thereby, the trouble caused by the generation of low-molecular siloxane can be eliminated.

[0011] The components (A1) and (A2) each preferably have a kinematic viscosity at 40°C of 60 to 8,000 mm 2 / s, more preferably 70 to 6,000 mm 2 / s, and even more preferably 80 to 5,000 mm 2It is / s. The ethylene-α-olefin copolymer of (A1) is preferably an ethylene-propylene copolymer. The copolymerization ratio of ethylene and polypropylene is preferably 90:10 to 10:90 by mass, more preferably 80:20 to 20:80. Further, in the mixed oil of polydecene-1 of (A2) and the ethylene-α-olefin copolymer, the mixing ratio of polydecene-1 and the ethylene-α-olefin is preferably 90:10 to 10:90 by mass, more preferably 80:20 to 20:80. Polydecene-1 is a polymer (hydrogenated polydecene) represented by the following (Chemical Formula 1). [Chemical Formula] However, n is 3 to 500.

[0012] With respect to 100 parts by mass of the component (A), the heat conductive particles of the component (B) are 400 to 2800 parts by mass, preferably 600 to 2600 parts by mass, more preferably 800 to 2400 parts by mass. Thereby, the thermal conductivity can be increased.

[0013] Thermally conductive particles (also referred to as thermally conductive fillers) are particulate substances that are macroscopically powdery and are mixed with the component (A) to form a composition. Thermally conductive particles refer to those among the particles that have excellent thermal conductivity and a higher thermal conductivity than the component (A). Thermally conductive particles include electrically conductive particles, electrically insulating particles, etc., and either can be used. Examples of electrically conductive particles include carbon powders such as carbon black or metal powders. In the case of metal powders, those with a surface resistance of 1 Ω / square or less are preferred. Specifically, powders composed of metals such as gold, silver, platinum, copper, nickel, iron, palladium, cobalt, chromium, aluminum, etc., or alloys such as stainless steel, or metal powders whose surfaces are coated with noble metals such as gold and silver to reduce electrical resistance are preferably used. Electrically insulating particles are preferably inorganic particles such as alumina (aluminum oxide), zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silica other than hydrophilic fumed silica. These inorganic particles may be added alone or in combination of multiple types. Among these, alumina (aluminum oxide) is preferred because of its low cost. When using alumina, α-alumina with a purity of 99.5% by weight or more is preferred. Various shapes of thermally conductive particles can be used, such as spherical, flaky, polyhedral, crushed, etc. The specific surface area of the thermally conductive particles is preferably in the range of 0.06 to 10 m 2 / g.

[0014] The thermally conductive particles preferably have a particle diameter (D50 (median diameter)) of 0.1 μm or more and 150 μm or less. Also, the thermally conductive particles may be blended singly or in combination of two or more types. When combining two or more types, 2 to 6 types are preferable. For example, as small particles, the particle diameter (D50 (median diameter)) can be 0.1 μm or more and less than 5 μm, as medium particles, the particle diameter (D50 (median diameter)) can be 5 μm or more and less than 50 μm, and as large particles, the particle diameter (D50 (median diameter)) can be 50 μm or more and 150 μm or less. When blended in combination of two or more types, the medium particles and / or small particles are filled between the large particles, and can be filled in a state close to the closest packing, resulting in high thermal conductivity. Also, a thermally conductive composition with a low plasticity degree of the composition and good moldability can be obtained. The particle diameter is the D50 (median diameter) of the cumulative particle size distribution based on volume in the particle size distribution measurement by the laser diffraction light scattering method. As this measuring instrument, for example, there is the laser diffraction / scattering type particle distribution measuring device LA-950S2 manufactured by Horiba, Ltd.

[0015] The thermally conductive sheet preferably has a thickness of 0.1 mm or more and 10 mm or less, more preferably 0.2 to 9 mm, and even more preferably 0.3 to 8 mm. With such a thickness, it is suitable as a thermally conductive material: TIM (Thermal Interface Material) to be interposed between the heat generating part of electrical and electronic components, etc. and the heat sink.

[0016] At least a part of the thermally conductive particles may be surface-treated with a coupling agent in advance. As an example of the coupling agent, R a Si(OR') 4-aThere is a silane compound represented by (R is an unsubstituted or substituted hydrocarbon group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, a is 0 or 1), or a partial hydrolyzate thereof. The alkoxysilane compound of the above chemical formula (hereinafter simply referred to as "silane") is, for example, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane and other silane compounds. The above silane compounds can be used alone or in combination of two or more. In particular, when fine heat conductive particles with a particle size D = 50 of less than 5 μm are surface-treated with a coupling agent in advance, the miscibility is improved and the workability is improved when making a compound.

[0017] The heat conductive sheet of the present invention further contains RaSi(OR') as component (C) 4-a (However, R is an unsubstituted or substituted hydrocarbon group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, a is 0 or 1). It is preferably contained in an amount of 0.1 to 2.2 parts by mass, more preferably 0.2 to 2.1 parts by mass, based on 100 parts by mass of component (A). Component (C) is not an essential component, but when component (C) is added, the miscibility is improved and the workability is improved when making a compound.

[0018] The thermal conductivity of the heat conductive sheet is preferably 1.0 W / m·K or more and 20.0 W / m·K or less , yo more preferably 2.0 to 20 W / m·K, and still more preferably 3.0 to 20 W / m·K. Such a heat conductive sheet is suitable as a TIM (Thermal Interface Material).

[0019] The SHORE OO hardness of the thermal conductive sheet is preferably 5 or more and 80 or less, more preferably 7 or more and 70 or less, and still more preferably 10 or more and 60 or less. With such hardness, when used as a thermal conductive material: TIM (Thermal Interface Material) interposed between the heat generating part of electrical and electronic components and the heat sink, it can follow even if there are irregularities on the heat generating part of electrical and electronic components and / or the heat sink, and can smooth the heat transfer. Also, the workability as a sheet becomes good. The lower the SHORE OO hardness value, the softer it is. The SHORE OO hardness is measured by the method defined in ASTM D2240.

[0020] The manufacturing method of the thermal conductive sheet of the present invention includes the following steps. (1) Compounding step As the non-curable liquid matrix resin (A), at least one selected from the group consisting of an ethylene-α-olefin copolymer (A1) having a kinematic viscosity at 40°C of 50 to 10,000 mm 2 / s and a mixed oil (A2) of polydecene-1 and an ethylene-α-olefin copolymer having a kinematic viscosity at 40°C of 50 to 10,000 mm 2 / s, 400 to 2800 parts by mass of the thermal conductive particles (B) are uniformly mixed with 100 parts by mass of the component (A) to form a compound. It is preferable to degas this compound under vacuum. Vacuum degassing is to reduce the pressure of the compound to -0.08 to -0.1 Pa, leave it for about 5 to 10 minutes, and degas. (2) Sheet forming step The compound is formed into a sheet without including a heat curing step. Sheet forming includes roll rolling with a polyethylene terephthalate (PET) film sandwiched, or press rolling, etc., and roll rolling that can continuously form a sheet is preferable.

[0021] Other components than those described above can be blended in the thermal conductive sheet of the present invention as needed. For example, heat resistance improvers such as red iron oxide, titanium oxide, and cerium oxide, flame retardants, and flame retardant aids may be added. Organic or inorganic particle pigments may be added for coloring and color adjustment purposes.

[0022] The following drawings will be used for explanation. In the following drawings, the same reference numerals denote the same components. FIG. 2 is a schematic cross-sectional view of a heat conductive sheet incorporated in a heat dissipation structure 10 according to an embodiment of the present invention. The heat conductive sheet 11b dissipates heat generated by an electronic component 13 such as a semiconductor element, and is fixed to the main surface 12a of the heat spreader 12 facing the electronic component 13, and is sandwiched between the electronic component 13 and the heat spreader 12 and. Further, the heat conductive sheet 11a is sandwiched between the heat spreader 12 and the heat sink 15. The heat conductive sheets 11a and 11b together with the heat spreader 12 constitute a heat dissipation member that dissipates heat of the electronic component 13. The heat spreader 12 is formed, for example, in a rectangular plate shape, and has a main surface 12a facing the electronic component 13 and side walls 12b erected along the outer periphery of the main surface 12a. The heat spreader 12 has the heat conductive sheet 11b provided on the main surface 12a surrounded by the side walls 12b, and the heat sink 15 is provided on the other surface 12c opposite to the main surface 12a via the heat conductive sheet 11a. The electronic component 13 is, for example, a semiconductor element such as a BGA and is mounted on a wiring board 14.

Example

[0023] The following examples will be used for explanation. The present invention is not limited to the examples. Various parameters were measured by the following methods. <Thermal conductivity> The thermal conductivity of the heat conductive sheet was measured by a hot disk (conforming to ISO 22007-2:2008). As shown in FIG. 1A, this thermal conductivity measuring device 1 sandwiches a sensor 2 made of a polyimide film between two samples 3a and 3b, applies a constant power to the sensor 2, generates heat constantly, and analyzes the thermal characteristics from the temperature rise value of the sensor 2. The tip 4 of the sensor 2 has a diameter of 7 mm, and as shown in FIG. 1B, it has a double spiral structure of electrodes, and an electrode 5 for applying current and an electrode for resistance value (electrode for temperature measurement) 6 are arranged at the lower part. The thermal conductivity is calculated by the following formula (Equation 1).

Equation

[0024] (Examples 1 to 4, Comparative Examples 1 to 3) 1 Matrix resin (Component A) (1) A non-curable ethylene-propylene copolymer liquid oil with a kinematic viscosity of 200 mm 2 / s (2) A non-curable liquid mixed oil of polydecene-1 and ethylene-propylene copolymer with a kinematic viscosity of 100 mm 2 / s. The mixing ratio is 65% content of polydecene-1 and 35% content of ethylene-propylene copolymer. (3) A non-curable ethylene-propylene copolymer liquid oil with a kinematic viscosity of 37500 mm 2 / s 2 Thermally conductive particles (1) Amorphous crushed alumina shown in Figure 3, D50 = 0.3 μm, pre-treated product with octyltrimethoxysilane. (2) Amorphous crushed alumina shown in Figure 4, D50 = 2.2 μm, pre-treated product by decyltrimethoxysilane treatment. (3) Spherical alumina shown in Figure 5, D50 = 75 μm. (4) Rounded aluminum nitride (AlN) shown in Figure 6, D50 = 20 μm. (5) Amorphous crushed aluminum nitride (AlN) shown in Figure 7, D50 = 15 μm. 3 Silane coupling agent (Component C) Decyltrimethoxysilane was used. 4 Mixing process A silane coupling agent and thermally conductive inorganic particles were added to the above matrix component, and they were mixed and stirred using a planetary mixer to form a compound. Next, this compound was depressurized to -0.08 to -0.1 Pa and left for about 5 to 10 minutes for vacuum degassing. 5 Sheet forming process The above compound was sandwiched between polyethylene terephthalate (PET) films and roll-rolled. The obtained sheet had a thickness of 2 mm, a width of 200 mm, and a length of 300 m. It was evaluated whether mixing could be easily performed in the above mixing process, and it was evaluated whether sheet forming could be easily performed in the sheet forming process. Since practical production cannot be carried out if there are problems in the above mixing process and sheet forming process, this evaluation is important. The above conditions and results are summarized in Table 1 below.

[0025]

Table 1

[0026] From the above results, the following was found. (1) In Examples 1 to 4, the formability of the thermally conductive sheet was good, the SHORE 00 hardness and the thermal conductivity were also good, and it was suitable as a thermally conductive material: TIM (Thermal Interface Material) to be interposed between the heat generating part and the heat sink of electrical and electronic components, etc. Also, it was confirmed that it is a thermally conductive sheet with a long pot life (service period) at the raw material stage, no need for a heat curing process, low manufacturing cost, and low hardness. (2) On the other hand, in Comparative Example 1, the viscosity of the ethylene-propylene copolymer was too high, the oil and the thermally conductive particles (fillers) did not mix, and mixing could not be performed. In Comparative Example 2, the blending amount of the thermally conductive particles (fillers) was too large, the oil and the thermally conductive particles (fillers) did not mix, and mixing could not be performed. In Comparative Example 3, the blending amount of the thermally conductive particles (fillers) was too small, the mixture became liquid, and sheet formation could not be performed.

Industrial applicability

[0027] The thermally conductive silicone sheet of the present invention is suitable as a thermally conductive material: TIM (Thermal Interface Material) to be interposed between a heat generating part of an electric or electronic component or the like and a heat sink.

Explanation of symbols

[0028] 1 Thermal conductivity measuring device 2 Sensor 3a, 3b Sample 4 Tip of the sensor 5 Electrode for applied current 6 Electrode for resistance value (electrode for temperature measurement) 10 Heat dissipation structure 11a, 11b Thermally conductive sheet 12 Heat spreader 13 Electronic component 14 Wiring board 15 Heat sink

Claims

1. A thermally conductive sheet comprising a non-curable liquid matrix resin (A) and thermally conductive particles (B), The component (A) has a kinetic viscosity of 50 to 10,000 mm at 40°C. 2 / s and a kinematic viscosity at 40°C of 50 to 10,000 mm 2 and (A2) a mixed oil of polydecene-1 and an ethylene-α-olefin copolymer, The thermally conductive particles of the component (B) are contained in an amount of 400 to 2800 parts by mass relative to 100 parts by mass of the component (A), the thermally conductive sheet is in an uncured state; The thermally conductive sheet has a SHORE OO hardness of 5 or more and 80 or less.

2. 2. The thermally conductive sheet according to claim 1, wherein the thermally conductive particles have a particle diameter (D50 (median diameter)) of 0.1 μm or more and 150 μm or less.

3. The thermally conductive sheet according to claim 1 , wherein the thermally conductive particles are of one type or a combination of two or more types.

4. The thermally conductive sheet according to claim 1 , wherein the thermally conductive sheet has a thickness of 0.1 mm or more and 10 mm or less.

5. At least a portion of the thermally conductive particles is RaSi(OR') 4-a 2. The thermally conductive sheet according to claim 1, which has been surface-treated in advance with (wherein R is an unsubstituted or substituted hydrocarbon group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1).

6. The thermally conductive sheet further contains RaSi(OR') as component (C). 4-a 2. The thermally conductive sheet according to claim 1, comprising 0.1 to 2.2 parts by mass of (wherein R is an unsubstituted or substituted hydrocarbon group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1) per 100 parts by mass of component (A).

7. 2. The thermally conductive sheet according to claim 1, wherein the thermal conductivity of the thermally conductive sheet is 1.0 W / m·K or more and 20.0 W / m·K or less.

8. A method for producing a thermally conductive sheet according to any one of claims 1 to 7, The non-curable liquid matrix resin (A) has a kinetic viscosity of 50 to 10,000 mm at 40°C. 2 / s and a kinematic viscosity at 40°C of 50 to 10,000 mm 2 and (A2) a mixed oil of polydecene-1 and an ethylene-α-olefin copolymer, Mixing 400 to 2,800 parts by mass of thermally conductive particles (B) with 100 parts by mass of the component (A); 1. A method for producing a thermally conductive sheet, comprising forming the thermally conductive sheet into a sheet without a heat curing step, and setting the SHORE OO hardness of the thermally conductive sheet to 5 or more and 80 or less.