Thermally conductive grease and method of manufacturing the same

Abstract

The thermally conductive grease of the present invention contains a liquid olefin polymer and thermally conductive particles. The liquid olefin polymer has a kinematic viscosity of 10,000 mmHg at 40°C. 2 Ethylene-α-olefin copolymers with a viscosity of less than 1 / s contain 400 to 2000 parts by mass of thermally conductive particles relative to 100 parts by mass of liquid olefin polymers. When the thermally conductive particles are set to 100% by mass, 5 to 80% by mass are alumina particles with a central particle size of 0.1 to 5 μm, and 20 to 95% by mass are other thermally conductive particles. The absolute viscosity at 23°C, measured by a Type B viscometer at a rotation speed of 5 rpm using a T-E rotating shaft, is in the range of 300 to 7000 Pas.

Description

Technical Field

[0001] This invention relates to a thermally conductive grease suitable for use between a heat-generating part and a heat sink in electrical and electronic components, and a method for manufacturing the same. Background Technology

[0002] The performance improvements of semiconductors such as CPUs in recent years have been remarkable, leading to a significant increase in heat generation. Therefore, thermally conductive silicone greases are used to install heat sinks in heat-generating electronic components and to improve the seal between heat sinks and heat sinks in semiconductors. With the miniaturization, high performance, and high integration of devices, thermally conductive silicone greases require not only high thermal conductivity but also drop resistance. Patent Document 1 proposes a composition containing a thermally conductive filler, a polyorganosiloxane resin containing at least one polysiloxane having a curable functional group within its molecule, a siloxane compound having an alkoxysilyl group and a linear siloxane structure, and a composition that prevents leakage. Patent Document 2 proposes a thermally conductive silicone composition containing liquid silicone, a thermally conductive filler, and hydrophobic spherical silica microparticles, which improves heat dissipation. Patent Document 3 proposes a composition containing liquid ethylene-propylene copolymer rubber, an organic peroxide crosslinking agent, and a metal hydroxide filler, which is then molded and crosslinked.

[0003] Existing technical documents

[0004] Patent documents

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

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

[0007] Patent Document 3: Japanese Patent Application Publication No. 2010-077220 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, conventional grease-like compositions based on liquid organopolysiloxanes have the problem of generating low-molecular-weight siloxanes. These low-molecular-weight siloxanes can detach from the composition or volatilize, causing electrical contact problems. Furthermore, in the composition of Patent Document 3, a specified amount of metal hydroxide filler such as aluminum hydroxide is added to achieve flame retardancy, resulting in relatively low thermal conductivity.

[0010] In order to solve the above-mentioned problems, the present invention provides a thermally conductive grease that does not produce low-molecular-weight siloxanes and has both the absolute viscosity and thermal conductivity suitable for TIM applications.

[0011] Methods for solving problems

[0012] The thermally conductive grease of the present invention is a thermally conductive grease containing a liquid olefin polymer and thermally conductive particles, wherein the liquid olefin polymer has a kinematic viscosity of 10000 mmHg at 40°C. 2 The ethylene-α-olefin copolymer with a mass ratio of less than / s contains 400 to 2000 parts by mass of thermally conductive particles relative to 100 parts by mass of the liquid olefin polymer. When the thermally conductive particles are set to 100% by mass, 5 to 80% by mass are alumina particles with a central particle size of 0.1 to 5 μm, and 20 to 95% by mass are other thermally conductive particles. The absolute viscosity of the thermally conductive grease at 23°C, measured by a Type B viscometer at a rotation speed of 5 rpm using a TE rotating shaft, is in the range of 300 to 7000 Pas.

[0013] The method for manufacturing the thermally conductive grease of the present invention includes a step of mixing a liquid olefin polymer with thermally conductive particles.

[0014] The liquid olefin polymer has a kinematic viscosity of 10,000 mmHg at 40°C. 2 Ethylene-α-olefin copolymers with a ratio of less than / s,

[0015] Relative to 100 parts by weight of the liquid olefin polymer, 400-2000 parts by weight of thermally conductive particles are added.

[0016] When the thermally conductive particles are set to 100% by mass, 5-80% by mass are alumina particles with a central particle size of 0.1-5 μm, and 20-95% by mass are other thermally conductive particles.

[0017] The absolute viscosity of the thermally conductive grease, measured at 23°C using a Type B viscometer at 5 rpm and a TE rotating shaft, is in the range of 300–7000 Pas.

[0018] Invention Effects

[0019] This invention comprises a liquid olefin polymer and thermally conductive particles, wherein the liquid olefin polymer has a kinematic viscosity of 10,000 mM at 40°C. 2The ethylene-α-olefin copolymer with a viscosity of less than / s contains 400 to 2000 parts by mass of thermally conductive particles per 100 parts by mass relative to the liquid olefin polymer. When the thermally conductive particles are set to 100% by mass, 5 to 80% by mass are alumina particles with a central particle size of 0.1 to 5 μm, and 20 to 95% by mass are other thermally conductive particles. The absolute viscosity of the thermally conductive grease, measured at 23°C using a type B viscometer at 5 rpm and a TE rotating shaft, is in the range of 300 to 7000 Pas. This provides a thermally conductive grease that does not produce low-molecular-weight siloxanes and combines absolute viscosity and thermal conductivity suitable for TIM applications. The reason for not producing low-molecular-weight siloxanes is that organopolysiloxanes are not used as the base resin at all. Furthermore, the method for manufacturing the thermally conductive grease according to the present invention enables the efficient and efficient manufacture of the thermally conductive grease. Attached Figure Description

[0020] Figure 1A -B is an explanatory diagram illustrating a method for measuring the thermal conductivity of a sample in one embodiment of the present invention. Detailed Implementation

[0021] The thermally conductive grease of the present invention (hereinafter sometimes simply referred to as "grease") is a thermally conductive grease that uses a liquid olefin polymer as the base resin and contains thermally conductive particles. The liquid olefin polymer has a kinematic viscosity of 10,000 mmHg at 40°C. 2 Ethylene-α-olefin copolymers with a viscosity of less than 1 / s. As an example of ethylene-α-olefin copolymers, there is an ethylene-propylene copolymer. This substance is a hydrocarbon synthetic oil without polar groups, commercially available under the trade name "LUCANT" series manufactured by Mitsui Chemicals Co., Ltd. The kinematic viscosity of the liquid olefin polymer at 40°C can be determined, for example, by the method described in the examples.

[0022] The liquid olefin polymer may also be a mixture of at least two ethylene-propylene copolymers with different kinematic viscosities. Furthermore, the liquid olefin polymer may also have a kinematic viscosity of less than 1000 mmHg at 40°C. 2 The kinematic viscosity at 40°C and 1000 m³ / s is [value missing]. 2 A mixture of at least two ethylene-propylene copolymers with kinematic viscosities of 1 / s or higher. This makes it easy to adjust the overall absolute viscosity to the specified absolute viscosity. If the kinematic viscosity at 40°C exceeds 10000 mm² / s... 2 If the viscosity is low, it becomes difficult to mix with thermally conductive fillers. Furthermore, the overall absolute viscosity tends to increase, leading to problems such as difficulty in grease application.

[0023] The thermally conductive particles are added in an amount of 400 to 2000 parts by weight relative to 100 parts by weight of the liquid olefin polymer. If the amount is less than 400 parts by weight, the thermal conductivity is poor; if it exceeds 2000 parts by weight, mixing with the liquid olefin polymer becomes difficult. In addition, the overall absolute viscosity tends to increase, which can lead to problems in use, such as difficulty in applying grease.

[0024] Of the thermally conductive particles, 5–80% by mass are alumina particles with a central particle size of 0.1–5 μm, and 20–95% by mass are other thermally conductive particles. The alumina particles with a central particle size of 0.1–5 μm are preferably amorphous. If the alumina particles are amorphous, the overall absolute viscosity is easily reduced, making it easier to achieve high thermal conductivity.

[0025] Other thermally conductive particles are preferably particles with a central particle size of 0.1 to 5 μm or larger. Particularly preferred are thermally conductive particles with a central particle size exceeding 5 μm. These thermally conductive particles with a central particle size exceeding 5 μm are preferably at least one particle selected from alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silica other than hydrophilic fumed silica. Examples of silica other than hydrophilic fumed silica include precipitated silica (wet silica), hydrophobic fumigant silica (fumed silica), crystalline silica, and amorphous silica.

[0026] By setting alumina (alumina) with a central particle size of 0.1–5 μm to 5–80% by mass and thermally conductive particles with a central particle size exceeding 5 μm to 20–95% by mass, small particles are present between large particles, resulting in near-maximum packing and thus improving thermal conductivity. Furthermore, in this application, the central particle size is the D50 (median diameter) of the cumulative particle size distribution based on volume reference using laser diffraction light scattering. For example, the laser diffraction / scattering particle size distribution measuring device LA-950S2 manufactured by Arihoba Corporation is used for this measurement.

[0027] The thermally conductive grease of the present invention has an absolute viscosity of 300 to 7000 Pas, preferably 500 to 6500 Pas, and more preferably 600 to 6000 Pas, measured at 23°C using a type B viscometer at 5 rpm and a TE rotating shaft. As long as the absolute viscosity is within the above range, it is suitable as a grease for improving the adhesion between heat-generating and heat-dissipating elements such as semiconductors. Such a thermally conductive grease is suitable for TIM (Thermal Interface Material) applications.

[0028] The alumina with a central particle size of 0.1–5 μm is preferably produced using R... a Si(OR')4-a Surface treatment is performed on alkoxysilane compounds or their partial hydrolysates represented by (R being a non-substituted or substituted organic group with 6 to 12 carbon atoms, R' being an alkyl group with 1 to 4 carbon atoms, and a being 0 or 1). Preferred silane coupling agents include, for example, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, and dodecyltriethoxysilane compounds. One or more of these silane compounds can be used in combination. The surface treatment described here includes adsorption in addition to covalent bonding. If surface treatment is performed, the matrix resin and thermally conductive particles will have good mixability.

[0029] Silane coupling agents can be pretreated by mixing with thermally conductive particles (pretreatment method) or added when mixing the matrix resin and thermally conductive particles (overall mixing method). When using the two-treatment method, it is preferable to add 0.01 to 10 parts by weight of silane coupling agent per 100 parts by weight of thermally conductive particles. Surface treatment facilitates easy filling into the matrix resin.

[0030] In the grease of the present invention, other components besides those mentioned above can be added as needed. For example, heat-resistant improvers such as iron oxide red, titanium oxide, and cerium oxide, as well as flame retardants and flame-retardant additives, can also be added. Organic or inorganic particulate pigments can also be added for coloring or tinting purposes.

[0031] The thermal conductivity of the thermally conductive grease of the present invention is preferably 2 W / mk or higher, more preferably 2 to 15 W / mk, and even more preferably 2.2 to 10 W / mk. If the thermal conductivity is as described above, it is suitable for TIM applications.

[0032] In the manufacturing method of the thermally conductive grease of the present invention, a thermally conductive grease is formed by mixing a liquid olefin polymer and thermally conductive particles, adding other additives as needed, and mixing the entire mixture to form a thermally conductive grease with an absolute viscosity of 300-7000 Pas at 23°C, measured using a Type B viscometer at 5 rpm and a TE rotating shaft. The liquid olefin polymer has a kinematic viscosity of 10000 mmHg at 40°C. 2 In an ethylene-α-olefin copolymer with a mass ratio of less than 1 / s, 400 to 2000 parts by mass of the thermally conductive particles are added relative to 100 parts by mass of the liquid olefin polymer. When the thermally conductive particles are set to 100% by mass, 5 to 80% by mass are alumina particles with a central particle size of 0.1 to 5 μm, and 20 to 95% by mass are other thermally conductive particles.

[0033] The thermally conductive grease of the present invention can be formed into an article by filling it into a dispenser, bottle, can, tube, etc.

[0034] Example

[0035] The following example illustrates one aspect of the present invention. However, the present invention is not limited to these examples. Various parameters were measured using the methods described below.

[0036] Thermal conductivity

[0037] The thermal conductivity of the thermally conductive grease was determined using a hot disk (transient planar heat source method) (according to ISO / CD22007-2). The thermal conductivity measuring apparatus 1 is as follows: Figure 1A As shown, a polyimide film sensor 2 was fabricated by sandwiching two samples 3a and 3b. A constant current was applied to the sensor 2, causing it to heat up constantly. The thermal characteristics were analyzed from the temperature rise of the sensor 2. The diameter of the front end 4 of the sensor 2 is 7 mm. Figure 1B As shown, the electrode has a double helix structure, with a current-applying electrode 5 and a resistance electrode (temperature-measuring electrode) 6 arranged at the bottom. The thermal conductivity is calculated using the following formula (Mathematical Formula 1).

[0038] [Mathematical Expression 1]

[0039]

[0040] λ: Thermal conductivity (W / m·K)

[0041] Po: Hengdian Power (W)

[0042] r: Radius of the sensor (m)

[0043] τ:

[0044] α: Thermal diffusivity of the sample (m) 2 / s)

[0045] t: Measurement time (s)

[0046] D(τ): A dimensionless function of τ

[0047] ΔT(τ): Temperature rise of the sensor (K)

[0048] <Kinetic viscosity of ethylene-propylene copolymer>

[0049] The viscosity is listed in the manufacturer's product catalog and is the kinematic viscosity at 40°C as measured by an Uberloud viscometer.

[0050] <Absolute viscosity of grease>

[0051] The absolute viscosity of the grease was measured using a Type B viscometer (HBDV2T manufactured by Brookfield). A TE rotary shaft was used, and the absolute viscosity at 23°C was measured at 5 rpm. However, for Comparative Example 1, a TF rotary shaft was used because the viscosity exceeded the upper limit measured by the TE rotary shaft.

[0052] (Examples 1-4, Comparative Examples 1-2)

[0053] 1. Raw material composition

[0054] (1) Liquid olefin polymers

[0055] The kinematic viscosity at 40°C is 400 mm³. 2 / s Ethylene-propylene copolymer: Manufactured by Mitsui Chemicals, trade name "LUCANT LX004"

[0056] The kinematic viscosity at 40°C is 9850 mm³. 2 / s Ethylene-propylene copolymer: Manufactured by Mitsui Chemicals, trade name "LUCANT LX100"

[0057] The kinematic viscosity at 40°C is 37500 mm³. 2 / s of ethylene-propylene copolymer: manufactured by Mitsui Chemicals, trade name "LUCANT LX400"

[0058] (2) Thermally conductive particles

[0059] • Amorphous alumina with a central particle size of 2.3 μm: decyltrimethoxysilane pretreated product (1.1 g of decyltrimethoxysilane adsorbed relative to 100 g of alumina).

[0060] • Amorphous alumina with a center particle size of 0.3 μm: octyltrimethoxysilane pretreated product (adsorbed 2.4 g of octyltrimethoxysilane per 100 g of alumina)

[0061] • Spherical alumina with a center particle size of 20 μm (untreated)

[0062] • Spherical alumina with a center particle size of 35 μm (untreated)

[0063] • Amorphous silica with a center particle size of 20μm (non-crystalline silica, no surface treatment)

[0064] • Aluminum hydroxide with a center particle size of 20 μm (untreated)

[0065] 2. Mixing method

[0066] Thermally conductive grease is formed by mixing thermally conductive particles into the above-mentioned liquid olefin polymer.

[0067] The grease obtained as described above was evaluated. The conditions and results are summarized in Table 1 below.

[0068] Table 1

[0069]

[0070] The results above confirm that Examples 1-4 are grease-like thermally conductive greases that do not produce low-molecular-weight siloxanes and possess both suitable absolute viscosity and thermal conductivity for TIM applications. The reason low-molecular-weight siloxanes are not produced is that no organopolysiloxanes are used as the base resin.

[0071] Industrial availability

[0072] The thermally conductive grease of the present invention is suitable for use as a TIM (Thermal Interface Material) between a heat-generating part and a heat sink in electrical and electronic components, etc.

[0073] Symbol Explanation

[0074] 1: Thermal conductivity measuring device

[0075] 2: Sensors

[0076] 3a, 3b: Samples

[0077] 4: Sensor front end

[0078] 5: Electrodes for applying current

[0079] 6: Electrodes for resistance measurement (electrodes for temperature measurement)

Claims

1. A thermally conductive grease, comprising a liquid olefin polymer and thermally conductive particles, wherein, It does not contain organopolysiloxanes. The liquid olefin polymer contains a kinematic viscosity of less than 1000 mmHg at 40°C. 2 / s of ethylene-α-olefin copolymer and a kinematic viscosity of 1000 mm at 40°C. 2 / s or more and 10000mm 2 A mixture of at least two ethylene-α-olefin copolymers with a ratio of less than / s. Relative to 100 parts by weight of the liquid olefin polymer, it contains 400 to 2000 parts by weight of the thermally conductive particles. When the thermally conductive particles are set to 100% by mass, 5–80% by mass are alumina particles with a central particle size of 0.1–5 μm, and 20–95% by mass are other thermally conductive particles, wherein the other thermally conductive particles are thermally conductive particles with a central particle size exceeding 5 μm. The alumina particles with a central diameter of 0.1–5 μm are amorphous. The alumina particles with a central particle size of 0.1–5 μm are processed using R… a Si (OR') 4-a The indicated alkoxysilane compound or its partial hydrolysate, i.e., the silane coupling agent, has undergone surface treatment. In the formula, R is a non-substituted or substituted organic group with 6 to 12 carbon atoms, R' is an alkyl group with 1 to 4 carbon atoms, and a is 0 or 1. Surface treatment is performed by adding 0.01 to 10 parts by weight of the silane coupling agent relative to 100 parts by weight of the thermally conductive particles. The absolute viscosity of the thermally conductive grease, measured at 23°C using a Type B viscometer at 5 rpm and a TE rotating shaft, is in the range of 300–7000 Pas.

2. The thermally conductive grease according to claim 1, wherein, The thermally conductive particles with a central particle size exceeding 5 μm are selected from at least one of aluminum oxide, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silicon dioxide other than hydrophilic fumed silica.

3. The thermally conductive grease according to claim 1 or 2, wherein, The thermal conductivity of the thermally conductive grease is above 2 W / mk.

4. A method for manufacturing a thermally conductive grease, which is the method for manufacturing the thermally conductive grease according to any one of claims 1 to 3, wherein, This includes a process of mixing liquid olefin polymers with thermally conductive particles, without using organopolysiloxanes. The liquid olefin polymer contains a kinematic viscosity of less than 1000 mmHg at 40°C. 2 / s of ethylene-α-olefin copolymer and a kinematic viscosity of 1000 mm at 40°C. 2 / s or more and 10000mm 2 A mixture of at least two ethylene-α-olefin copolymers with a ratio of less than / s. Relative to 100 parts by weight of the liquid olefin polymer, 400 to 2000 parts by weight of the thermally conductive particles are added. When the thermally conductive particles are set to 100% by mass, 5-80% by mass are alumina particles with a central particle size of 0.1-5 μm, and 20-95% by mass are other thermally conductive particles, wherein the other thermally conductive particles are thermally conductive particles with a central particle size exceeding 5 μm. The alumina particles with a central diameter of 0.1–5 μm are amorphous. The alumina particles with a central particle size of 0.1–5 μm are processed using R… a Si (OR') 4-a The indicated alkoxysilane compound or its partial hydrolysate, i.e., the silane coupling agent, has undergone surface treatment. In the formula, R is a non-substituted or substituted organic group with 6 to 12 carbon atoms, R' is an alkyl group with 1 to 4 carbon atoms, and a is 0 or 1. Surface treatment is performed by adding 0.01 to 10 parts by weight of the silane coupling agent relative to 100 parts by weight of the thermally conductive particles. The absolute viscosity of the thermally conductive grease, measured at 23°C using a Type B viscometer at 5 rpm and a TE rotating shaft, is in the range of 300–7000 Pas.

5. A method of using the thermally conductive grease according to any one of claims 1 to 3 as a thermally conductive interface material between an electrical or electronic component and a heat sink.

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