Thermally conductive grease composition

Abstract

A non-cured heat conductive grease composition comprising: A: 100 parts by mass of an ethylene · alpha-olefin copolymer having a kinematic viscosity at 40°C of 10,000 mm 2 100 parts by mass, and B: 115 to 580 parts by mass relative to 100 parts by mass of the A component, of a heat conductive particle, the above heat conductive particle comprising: B1: 55 to 350 parts by mass of amorphous alumina having a center particle diameter of 0.1 to 1 µm and being alumina that is surface-treated with a part or all of a specific alkoxysilane compound or a partial hydrolyzate thereof, B2: 5 to 60 parts by mass of plate-like boron nitride having a center particle diameter of 0.1 to 10 µm, and B3: 55 to 170 parts by mass of agglomerated boron nitride having a center particle diameter of 20 to 70 µm, so as to be mixed in a mass ratio of the B3 component / B2 component = 2 to 20. Thus, a heat conductive grease composition that is less likely to generate a low molecular siloxane, has high drop resistance, and has a low specific gravity is provided.

Description

TECHNICAL FIELD

[0001] The present application relates to a heat conductive grease composition suitable for interposing between a heat generating portion of an electrical / electronic component or the like and a heat sink. BACKGROUND

[0002] The performance of recent semiconductors such as CPUs has been remarkably improved, and along with this, the amount of heat generated has also become enormous. Therefore, a heat sink is installed in the electronic component that generates heat, and a heat conductive grease is used in order to improve the adhesion of the heat generating body such as a semiconductor to the heat sink. Along with the miniaturization, high performance, and high integration of equipment, the heat conductive grease is required to have not only high heat conductivity but also fall resistance. Patent Literature 1 proposes a composition containing a heat conductive filler, a polyorganosiloxane resin containing at least one polysiloxane having one curable functional group in the molecule, and a siloxane compound having an alkoxysilyl group and a linear siloxane structure. In Patent Literature 2, a heat conductive silicone composition having improved heat dissipation is proposed, which contains a liquid silicone, a heat conductive filler, and a hydrophobic spherical silica microparticle. In

[0131] of Patent Literature 3, it is proposed that an alumina having different particle diameters and shapes is compounded in a fluorine-containing adhesive composition.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2018-104714

[0006] Patent Literature 2: Japanese Patent Application Publication No. 2016-044213

[0007] Patent Literature 3: Japanese Patent Application Publication No. 2017-190389 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] However, the conventional heat conductive silicone grease has problems of causing low molecular siloxane to cause electrical contact failure, low fall resistance, and high specific gravity.

[0010] The present application provides a heat conductive grease composition that is less likely to generate low molecular siloxane, has high fall resistance, and has low specific gravity.

[0011] MEANS FOR SOLVING THE PROBLEMS

[0012] The heat conductive grease composition of the present application is characterized by being a non-cured heat conductive grease composition, and contains:

[0013] A: 10,000 mm2 / s at 40°C2 100 parts by weight of ethylene-α-olefin copolymer with a mass ratio of less than / s, and

[0014] B: 115–580 parts by mass of thermally conductive particles relative to 100 parts by mass of component A.

[0015] The aforementioned thermally conductive particles include:

[0016] B1: Amorphous alumina with a central particle size of 0.1–1 μm, and partially or entirely formed by R… a Si(OR') 4-a (where R is a non-substituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1) represents 55 to 350 parts by mass of alumina that has undergone surface treatment of an alkoxysilane compound or its partial hydrolysate thereof.

[0017] B2: 5-60 parts by mass of plate-shaped boron nitride with a central particle size of 0.1-10 μm.

[0018] B3: 55–170 parts by mass of condensed boron nitride with a central particle size of 20–70 μm.

[0019] The components are formulated in a mass ratio of B3 to B2 of 2 to 20.

[0020] Invention Effects

[0021] This invention uses an ethylene-α-olefin copolymer as the matrix resin, which is less likely to produce low-molecular-weight siloxanes. By combining amorphous alumina, plate-shaped boron nitride, and condensed boron nitride of specific particle sizes, it can provide a thermally conductive grease composition with high shedding resistance and low specific gravity. Attached Figure Description

[0022] Figure 1 AB is an explanatory diagram illustrating a method for measuring the thermal conductivity of a sample in one embodiment of the present invention.

[0023] Figure 2 AD is a schematic illustration illustrating a drop test used in one embodiment of the present invention. Detailed Implementation

[0024] The thermally conductive grease composition of the present invention is a non-curing thermally conductive grease composition. Therefore, a curing catalyst and curing agent are not required, but may be added as needed. The base resin has a kinematic viscosity of 10,000 mmHg at 40°C. 2The ethylene-α-olefin copolymer has a kinematic viscosity at 40°C of 10,000 mm 2 / s or more, more preferably 100 to 8,000 mm 2 / s. As an example, the ethylene-α-olefin copolymer is an ethylene-propylene copolymer. This substance is a hydrocarbon synthetic oil containing no polar group, and is commercially available as "LUCANT" series manufactured by Mitsui Chemicals, Inc. The specific gravity of the ethylene-propylene copolymer is 0.83 to 0.85 (the density is 0.83 to 0.85 g / cm 3 ), and has an advantage of reducing the specific gravity of the composition.

[0025] The components are mixed to prepare the grease, as described below. The components include:

[0026] A: ethylene-α-olefin copolymer having a kinematic viscosity at 40°C of 10,000 mm 2 / s or less, and

[0027] B: 115 to 580 parts by mass of the thermally conductive particles, relative to 100 parts by mass of the component A. The component B is preferably 130 to 550 parts by mass, more preferably 160 to 500 parts by mass.

[0028] The thermally conductive particles include:

[0029] B1: amorphous alumina having a center particle diameter of 0.1 to 1 μm, and being surface-treated with an alkoxysilane compound represented by R a Si(OR') 4-a (wherein R is a non-substituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1) or a partial hydrolyzate thereof, 55 to 350 parts by mass,

[0030] B2: plate-like boron nitride having a center particle diameter of 0.1 to 10 μm, 5 to 60 parts by mass,

[0031] B3: agglomerated boron nitride having a center particle diameter of 20 to 70 μm, 55 to 170 parts by mass,

[0032] The components are mixed to prepare the grease, as described below. The components include:

[0033] The above "a part" means 50% by mass or more.

[0034] The above thermally conductive grease composition preferably further includes R a Si(OR')4-a 0.1 to 2 parts by mass of an alkoxysilane compound represented by the formula: RSi(OR')aOH (wherein R is a non-substituted or substituted organic group having 8 to 12 carbons, R' is an alkyl group having 1 to 4 carbons, and a is 0 or 1) as the C component (viscosity modifier). Thereby, the viscosity of the composition can be reduced.

[0035] The thermal conductivity of the above-mentioned heat-conductive grease composition is preferably 2.0 W / m-K or more and 8.0 W / m-K or less, more preferably 2.5 to 8.0 W / m-K, and further preferably 3.0 to 8.0 W / m-K. Such a heat-conductive grease is suitable as a TIM (Thermal Interface Material).

[0036] The specific gravity of the above-mentioned heat-conductive grease composition is preferably 1.0 or more and 2.4 or less, more preferably 1.1 to 2.3, and further preferably 1.2 to 2.2. Thereby, the specific gravity is low, and the weight of the entire electronic component can be reduced.

[0037] The absolute viscosity at 23°C of the above-mentioned heat-conductive grease composition, measured with a B-type viscometer at a rotation speed of 5 rpm using a T-E measuring shaft, is preferably 1,000 to 20,000 Pas, more preferably 1,000 to 18,000 Pas, and further preferably 1,000 to 15,000 Pas. Thereby, the heat-conductive grease composition is excellent in workability and also has good injection or coating properties between the heat-generating portion and the heat-dissipating portion.

[0038] In the present application, the B1 component, the B2 component, and the B3 component are mixed in the above-mentioned proportions in the A component, in order to fill the small particles between the large particles in a state close to the closest packing, and improve the thermal conductivity. The particle diameter is measured by a laser diffraction light scattering method, and the D50 (median particle diameter) of the cumulative particle size distribution based on the volume basis is measured. As the measuring device, for example, there is a laser diffraction / scattering type particle size distribution measuring device LA-950S2 manufactured by HORIBA, Ltd.

[0039] Part or all of the above-mentioned amorphous alumina having a central particle diameter of 0.1 to 1 μm is replaced with R a Si(OR') 4-asurface treatment. For example, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, and the like are used as the alkoxysilane compound. One or two or more kinds of the above silane compounds can be used. As the surface treatment agent, an alkoxysilane can be used in combination with a mono-terminal silanol siloxane. The surface treatment here includes adsorption and the like in addition to covalent bonding. By the surface treatment, the miscibility with the base resin becomes good.

[0040] The alkoxysilane compound is preferably pre-mixed with the thermally conductive particles and subjected to a pretreatment. The alkoxysilane compound is preferably added at 0.01 to 10 parts by mass with respect to 100 parts by mass of the thermally conductive particles. By the surface treatment, the effect of becoming easy to fill in the base resin is obtained.

[0041] Note that the amorphous alumina is produced by pulverization or crushing, and a commercially available product can be used.

[0042] The above thermally conductive grease composition is preferably disposed at 0.4 g between two plates, compressed and clamped to a thickness of 0.5 mm, and set in a thermal shock tester with the above two plates vertically held, and in a thermal shock test of 100 cycles in which each of -40°C and 125°C is held for 30 minutes, the grease falls within 5 mm. Thus, the fall resistance can be maintained at a high level.

[0043] In the grease of the present application, components other than the above can be compounded as needed. For example, a heat resistance improver such as red iron oxide, titanium oxide, cerium oxide, a flame retardant, a flame retardant aid, and the like can be added. An organic or inorganic particle pigment can be added for the purpose of coloring or toning. As a material added for the purpose of filler surface treatment and the like, an alkoxyl group-containing silicone can be added.

[0044] The thermally conductive grease composition of the present application can be filled in a dispenser, a bottle, a can, a tube, and the like to be made into a product.

[0045] Example

[0046] The following is explained using examples. The present application is not limited to the examples. As for various parameters, the following methods are used for measurement.

[0047] <Thermal conductivity>

[0048] The thermal conductivity of the thermally conductive grease is measured by Hot Disk (in accordance with ISO / CD 22007-2). The thermal conductivity measuring device 1 is as shown in FIG. 1. Figure 1As shown in Figure A, the polyimide film sensor 2 is clamped between two samples 3a and 3b. A constant power is applied to the sensor 2, causing it to heat up constantly, and the thermal characteristics are analyzed based on the temperature rise of the sensor 2. The diameter of the front end 4 of the sensor 2 is 7 mm. Figure 1 As shown in B, the electrode has a double-helix structure, with an electrode 5 for applying current and an electrode 6 for measuring resistance (temperature measurement) arranged at the bottom. The thermal conductivity is calculated using the following formula (Mathematical Formula 1).

[0049] [Mathematical Expression 1]

[0050]

[0051] λ: Thermal conductivity (W / m·K)

[0052] P o Constant power (W)

[0053] r: Radius of the sensor (m)

[0054] τ:

[0055] α: Thermal diffusivity of the sample (m² / s)

[0056] t: Measurement time (s)

[0057] D(τ): A dimensionless function of τ

[0058] ΔT(τ): Temperature rise of the sensor (K)

[0059] <Absolute viscosity of grease>

[0060] The absolute viscosity of the grease was determined using a Type B viscometer (BROOKFIELD HBDV2T). A TE measuring shaft was used to measure the absolute viscosity at a rotational speed of 5 rpm and a temperature of 23°C.

[0061] <Drop Test>

[0062] pass Figure 2 The drop test shown in AD is used to determine this.

[0063] Apply 0.4g of thermally conductive grease 4 between an aluminum plate 12 (40mm long, 100mm wide, 5mm thick) and a glass plate 11 (40mm long, 100mm wide, 5mm thick). Figure 2 A), the spacer 13 is compressed and clamped with a thickness of 0.5 mm. Figure 2 B). 15 is a thermally conductive grease compressed to a thickness of 0.5 mm. Next, it is placed in a thermal cycling test chamber such that the gap between the aluminum plate 12 and the glass plate 11 becomes perpendicular.Figure 2 C). 16 is a test piece before the test. In this state, a thermal cycle test is performed in which each of -40°C and 125°C is maintained for 30 minutes. The test piece is taken out after 100 cycles, and it is observed whether or not the heat conductive grease 15 falls off. 17 is a test piece after the test Figure 2 D), 18 is a falling distance. If the falling of the heat conductive grease is within 5 mm, it is judged as A, and in the case where it exceeds 5 mm, it is judged as B.

[0064] (Examples 1 to 2, Comparative Examples 1 to 2)

[0065] 1. Raw material components

[0066] (1) A component: ethylene-propylene copolymer

[0067] • Ethylene-propylene copolymer having a kinematic viscosity at 40°C of 400 mm 2 / s: manufactured by Mitsui Chemicals, Inc., trade name "LUCANT LX004"

[0068] • Non-curable silicone oil (dimethylpolysiloxane) having a kinematic viscosity at 40°C of 110 mm 2 / s

[0069] Used in the proportions shown in Table 1.

[0070] (2) B component: heat conductive particles

[0071] • Amorphous alumina having a center particle diameter of 0.3 μm (D50 = 0.3 μm): octyltrimethoxysilane pretreated product (2.4 g of octyltrimethoxysilane adsorbed with respect to 100 g of alumina)

[0072] • Plate-like boron nitride having a center particle diameter of 5 μm (D50 = 5 μm) (without surface treatment)

[0073] • Spherical agglomerated boron nitride having a center particle diameter of 60 μm (D50 = 60 μm) (without surface treatment)

[0074] • Amorphous alumina having a center particle diameter of 2.3 μm (D50 = 2.3 μm): decyltrimethoxysilane pretreated product (1.1 g of decyltrimethoxysilane adsorbed with respect to 100 g of alumina)

[0075] • Spherical alumina having a center particle diameter of 20 μm (D50 = 20 μm) (without surface treatment)

[0076] The compounding amounts are shown in Table 1.

[0077] (3) C component: viscosity modifier

[0078] • Decyltrimethoxysilane

[0079] 2. Mixing method

[0080] The thermally conductive particles and the viscosity modifier were mixed in the above A component to produce a thermally conductive grease composition.

[0081] The grease obtained by the above operation was evaluated. The conditions and results are shown collectively in Table 1 below.

[0082] [Table 1]

[0083]

[0084] From the above results, it was found that Examples 1 to 2 are thermally conductive grease compositions in the form of grease, less likely to generate low-molecular siloxane, high in drop resistance, and low in specific gravity.

[0085] In contrast, Comparative Example 1 has a problem of generating low-molecular siloxane, and is not preferable in drop resistance and specific gravity, compared to Examples 1 to 2, because silicone oil is used as the base resin. Comparative Example 2 is not preferable in drop resistance and specific gravity, compared to Examples 1 to 2, because B2 and B3 components are not used.

[0086] Industrial applicability

[0087] The thermally conductive grease composition of the present application is suitable for interposing between a heat generating portion of an electric / electronic component or the like and a heat sink.

[0088] Explanation of symbols

[0089] 1 Thermal conductivity measuring device

[0090] 2 Sensor

[0091] 3a, 3b Test sample

[0092] 4 Front end of sensor

[0093] 5 Electrode for applying current

[0094] 6 Electrode for resistance value (electrode for temperature measurement)

[0095] 11 Glass plate

[0096] 12 Aluminum plate

[0097] 13 Spacer

[0098] 14 Thermally conductive grease

[0099] 15 Thermally conductive grease after compression

[0100] 16 Test piece before test

[0101] 17 test piece after test

[0102] 18 drop distance

Claims

1. A thermally conductive lubricating grease composition, characterized in that, It is a non-curing, thermally conductive grease composition comprising: A: The kinematic viscosity at 40℃ is 10,000 mm³. 2 100 parts by weight of ethylene-α-olefin copolymer with a mass ratio of less than / s, and B: 115–580 parts by mass of thermally conductive particles relative to 100 parts by mass of component A. The thermally conductive particles comprise: B1: Amorphous alumina with a median particle size D50 of 0.1–1 μm, and partially or entirely formed by R… a Si(OR') 4-a The indicated compound is a surface-treated alumina comprising 55–350 parts by mass of an alkoxysilane compound or its partial hydrolysate, wherein R is a non-substituted or substituted organic group having 8–12 carbon atoms, R' is an alkyl group having 1–4 carbon atoms, and a is 0 or 1. B2: 5-60 parts by weight of plate-shaped boron nitride with a median particle size D50 of 0.1-10 μm. B3: 55-170 parts by mass of spherical agglomerated boron nitride with a median particle size D50 of 20-70 μm. The components are formulated in a mass ratio of B3 to B2 of 2 to 20.

2. The thermally conductive grease composition according to claim 1, wherein, The thermally conductive grease composition further comprises R a Si(OR') 4-a The indicated alkoxysilane compound is used as a viscosity modifier in 0.1 to 2 parts by mass: component C, wherein R is a non-substituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1.

3. The thermally conductive grease composition according to claim 1 or 2, wherein, The thermal conductivity of the thermally conductive grease composition is above 2.0 W / m·K and below 8.0 W / m·K.

4. The thermally conductive grease composition according to claim 1 or 2, wherein, The specific gravity of the ethylene-α-olefin copolymer is 0.83 to 0.

85.

5. The thermally conductive grease composition according to claim 1 or 2, wherein, The specific gravity of the thermally conductive grease composition is 1.0 or more and 2.4 or less.

6. The thermally conductive grease composition according to claim 1 or 2, wherein, The absolute viscosity of the thermally conductive grease composition, measured by a type B viscometer at a rotational speed of 5 rpm and a temperature of 23°C, is 1,000–20,000 Pas.

7. The thermally conductive grease composition according to claim 1 or 2, wherein, The thermally conductive grease composition is applied at a rate of 0.4g between two plates, compressed and clamped to a thickness of 0.5mm, and the two plates are held vertically in a thermal shock testing machine. The plates are held at -40°C and 125°C for 30 minutes each. After 100 cycles of thermal shock testing, the grease falls by less than 5mm.

8. The thermally conductive grease composition according to claim 1 or 2, wherein, The ethylene-α-olefin copolymer is an ethylene-propylene copolymer.

9. The thermally conductive grease composition according to claim 1 or 2, wherein, The thermally conductive grease composition is filled into a dispenser, bottle, can, or tube.

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