Thermally conductive composition

Abstract

To provide a thermally conductive composition excellent in heat stability and heat conductivity, even when using a base oil containing hydrocarbon oil.SOLUTION: There is provided a thermally conductive composition containing a base oil composition and an inorganic powder filler. In the thermally conductive composition, the inorganic powder filler contains silver-coated copper powder, and the base oil composition contains a base oil containing hydrocarbon oil, and a deactivator. The deactivator preferably includes benzotriazol, and further preferably, the deactivator is contained at the ratio of 0.50 pt. mass or more to 100 pts. mass base oil.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a thermally conductive composition. [Background technology]

[0002] Some semiconductor components used in electronic devices generate heat during use, such as power semiconductors for power control in computer CPUs, inverters, converters, etc. In order to protect these semiconductor components from heat and ensure their normal functioning, there is a method of dissipating the generated heat by conducting it to a heat dissipation component such as a heat sink. Thermally conductive grease is applied between these semiconductor components and heat dissipation components so that they are in close contact with each other, and is used to efficiently conduct the heat from the semiconductor components to the heat dissipation components. In recent years, the performance of electronic devices using these semiconductor components has improved, and they have become smaller and more densely packed, so there is a demand for higher heat resistance in thermally conductive compositions used for heat dissipation measures.

[0003] As such a thermally conductive composition, a thermally conductive composition based on silicone oil and containing a thermally conductive filler such as zinc oxide or alumina powder has been disclosed (see Patent Documents 1 and 2).

[0004] Also, as a thermally conductive composition to be used in places where insulation of electronic components is not required, a thermally conductive composition has been disclosed in which metal powders such as aluminum powder and copper powder are mixed into a base oil such as silicone oil in order to increase thermal conductivity (see Patent Documents 3 and 4). Thus, for thermally conductive compositions that require heat resistance, oils with high heat resistance such as silicone oil have been used conventionally. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 51-055870 [Patent Document 2] Japanese Patent Application Publication No. 50-105573 [Patent Document 3] JP 2000-063873 A [Patent Document 4] JP 2006-137930 A Summary of the Invention [Problem to be solved by the invention]

[0006] Now, when silicone oil is used as the base oil contained in the thermal conductive composition, there is a concern that the free siloxane contained in the silicone oil or generated by the thermal decomposition of the silicone oil may cause electrical failure at the contact part. Therefore, as the base oil contained in the thermal conductive composition, a base oil with high heat resistance other than silicone oil may be required. As an example of the base oil having heat resistance other than silicone oil, a base oil containing hydrocarbon oil may be mentioned.

[0007] Here, the thermally conductive filler contained in the thermally conductive composition may be copper powder, which is a metal powder. Copper in particular is a material with extremely high thermal conductivity, and even if the content of copper powder in the thermally conductive composition is relatively small, it is possible to impart high thermal conductivity to the thermally conductive composition.

[0008] However, the present inventors have found that when copper powder is contained in a hydrocarbon oil, the hydrocarbon oil oxidizes over time due to the catalytic action of the copper powder in a high-heat environment. Therefore, in a thermally conductive composition containing copper powder and a hydrocarbon oil, the hydrocarbon oil may oxidize in a high-heat environment, causing the thermally conductive composition to harden. Thus, a thermally conductive composition containing copper powder and a hydrocarbon oil has low thermal stability.

[0009] In addition, when alumina or silica is added to the hydrocarbon oil instead of copper powder as a thermally conductive filler, the oxidation of the hydrocarbon oil over time can be suppressed, but these thermally conductive fillers have a lower thermal conductivity than copper powder, and cannot impart high thermal conductivity to the thermally conductive composition. In addition, when the amount of the thermally conductive filler is increased to obtain a high thermal conductivity as a thermally conductive composition, the content of other components such as base oil components is relatively reduced, and the handling property is deteriorated, for example, the control of the consistency becomes difficult.

[0010] The present invention has been made in consideration of such problems, and has an object to provide a thermally conductive composition that has excellent thermal stability, thermal conductivity, and good handleability, even when a base oil containing a hydrocarbon oil is used. [Means for solving the problem]

[0011] As a result of intensive research conducted by the inventors in order to solve the above-mentioned problems, they discovered that the above-mentioned problems can be solved by containing silver-coated copper powder as a thermally conductive filler and further containing a specific deactivator, and thus completed the present invention.

[0012] (1) A first aspect of the present invention is a thermally conductive composition comprising a base oil composition and an inorganic powder filler, the inorganic powder filler comprising silver-coated copper powder, and the base oil composition comprising a base oil containing a hydrocarbon oil and a passivating agent.

[0013] (2) A second aspect of the present invention is the thermally conductive composition according to the first aspect of the present invention, wherein the deactivator contains benzotriazole.

[0014] (3) A third aspect of the present invention is the thermally conductive composition according to the first or second aspect of the present invention, wherein the deactivator is contained in an amount of 0.50 parts by mass or more per 100 parts by mass of the base oil.

[0015] (4) A fourth aspect of the present invention is the thermally conductive composition according to the third aspect of the present invention, wherein the deactivator is contained in an amount of 0.50 parts by mass or more and 5.00 parts by mass or less per 100 parts by mass of the base oil.

[0016] (5) A fifth aspect of the present invention is a thermally conductive composition according to any one of the first to fourth aspects of the present invention, wherein the amount of silver coated on the copper powder is 5.0 parts by mass or more per 100 parts by mass of the copper powder. Effect of the Invention

[0017] According to the present invention, even when a base oil containing a hydrocarbon oil is used, it is possible to provide a thermally conductive composition that is excellent in thermal stability and thermal conductivity and has good handleability. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the embodiments of the present invention will be described in detail, however, the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0019] <Thermal conductive composition> The thermally conductive composition according to the present embodiment contains a base oil composition and an inorganic powder filler. The inorganic powder filler contains silver-coated copper powder, and the base oil composition contains a base oil containing a hydrocarbon oil and a passivator.

[0020] By using an inorganic powder filler containing silver-coated copper powder (hereinafter, sometimes referred to as silver-coated copper powder) as a thermally conductive filler, it is possible to prevent the surface of the copper powder from coming into contact with the hydrocarbon oil. In this state, by adding a specific deactivator to the base oil composition, it is possible to effectively suppress the oxidation of the hydrocarbon oil over time due to the catalytic action of the copper powder in a high-heat environment. Moreover, copper and silver have extremely high thermal conductivity, and by containing silver-coated copper powder, it is possible to impart high thermal conductivity to the thermally conductive composition. In this way, the thermally conductive composition according to this embodiment has excellent thermal conductivity and thermal stability.

[0021] Furthermore, since the silver-coated copper powder can impart high thermal conductivity to the thermal conductive composition even in a relatively small amount, there is no need to increase the content of the silver-coated copper powder to obtain high thermal conductivity, which makes it possible to relatively increase the content of other components such as the base oil component, and the handling properties are good.

[0022] Each component contained in the thermally conductive composition will be described below.

[0023] [About each ingredient] (Inorganic powder filler) The inorganic powder filler used in the thermally conductive composition according to the present embodiment contains silver-coated copper powder (silver-coated copper powder), which suppresses the deterioration of the hydrocarbon oil caused by contact with the copper powder in a high-temperature environment.

[0024] In the silver-coated copper powder, silver may be present on at least a portion of the surface of the copper powder, but it is preferable that the entire surface of the copper powder is coated with silver, which can reliably prevent contact between the surface of the copper powder and the hydrocarbon oil and more effectively suppress deterioration of the hydrocarbon oil.

[0025] The amount of silver coating in the silver-coated copper powder is not particularly limited, but is preferably 3.0 parts by mass or more, and more preferably 5.0 parts by mass or more, relative to 100 parts by mass of copper powder. By having the amount of silver coating of 3.0 parts by mass or more, a uniform silver coating is formed on the copper surface, making it possible to more effectively prevent the surface of the copper powder from contacting with the hydrocarbon oil. The amount of silver coating is preferably 20.0 parts by mass or less, and more preferably 15.0 parts by mass or less, relative to 100 parts by mass of copper powder. By having the amount of silver coating of 20.0 parts by mass or less relative to 100 parts by mass of copper powder, it is possible to suppress the increase in cost due to silver coating. Furthermore, it is possible to suppress the wear of the silver coating.

[0026] The average particle size of the silver-coated copper powder is not particularly limited, but is preferably 0.4 μm or more, and more preferably 1.0 μm or more. By having an average particle size of 0.4 μm or more, the coating property of the thermally conductive composition can be improved, and the film thickness of the thermally conductive composition after coating can be stabilized. In addition, multiple types of silver-coated copper powders with different average particle sizes may be mixed. It is possible to reduce the amount of base oil that enters the gaps between the particles of the silver-coated copper powder, and it is possible to increase the content of the silver-coated copper powder contained in the thermally conductive composition.

[0027] The average particle size of the silver-coated copper powder is an arithmetic mean diameter determined from a volume-based particle size distribution obtained by a laser diffraction method.

[0028] The method for coating silver on copper powder is not particularly limited, and a conventionally known method can be used. For example, it may be electroplating, which uses an external power source to cause a reduction reaction of silver ions on the surface of the copper powder to precipitate silver, electroless plating, which precipitates silver by the reduction action of chemicals, or a method for coating silver by dry plating. From the viewpoint of forming a uniform silver coating, a method for coating silver by dry plating is preferable. Examples of dry plating include vacuum deposition, sputtering, and ion plating.

[0029] The inorganic powder filler may contain inorganic powder fillers other than the silver-coated copper powder. The inorganic powder filler other than the silver-coated copper powder is not particularly limited as long as it has a higher thermal conductivity than the base oil, and examples of the inorganic powder filler include powders of metal oxides, inorganic nitrides, metals (including alloys), silicon compounds, carbon materials, etc.

[0030] (Base oil composition) The base oil composition contains a base oil containing a hydrocarbon oil and a deactivator. Each component contained in the base oil composition will be described below.

[0031] (1) Base oil The base oil, when contained in the thermally conductive composition, imparts lubricity to the thermally conductive composition.

[0032] Examples of the hydrocarbon oil include mineral oil, synthetic hydrocarbon oil, ester-based base oil, and ether-based base oil.

[0033] The mineral oil is, for example, a mineral oil-based lubricating oil fraction refined by an appropriate combination of refining techniques such as solvent extraction, solvent dewaxing, hydrorefining, hydrocracking, wax isomerization, etc., and can be 150 neutral oil, 500 neutral oil, bright stock, high viscosity index base oil, etc. The mineral oil used as the base oil is preferably a high viscosity index base oil that has been highly hydrorefined.

[0034] Examples of synthetic hydrocarbon oils include alpha-olefins produced from raw materials such as ethylene, propylene, butene, and derivatives thereof, which are polymerized alone or in combination of two or more kinds. Preferred examples of alpha-olefins include those having 6 to 14 carbon atoms.

[0035] Specific examples of synthetic hydrocarbon oils used for the base oil include polyalphaolefins (PAOs) which are oligomers of 1-decene or 1-dodecene, polybutenes which are oligomers of 1-butene or isobutylene, and co-oligomers of ethylene or propylene with alpha olefins, etc. In addition, alkylbenzenes and alkylnaphthalenes can also be used.

[0036] Examples of the ester-based base oil include diesters and polyol esters. Examples of the diesters include esters of dibasic acids such as adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid. The dibasic acids are preferably aliphatic dibasic acids having 4 to 36 carbon atoms. The alcohol residue constituting the ester moiety is preferably a monohydric alcohol residue having 4 to 26 carbon atoms.

[0037] The polyol ester is an ester of neopentyl polyol having no hydrogen atom on the β-position carbon, and specific examples thereof include carboxylic acid esters of neopentyl glycol, trimethylolpropane, pentaerythritol, etc. The carboxylic acid residue constituting the ester moiety is preferably a monocarboxylic acid residue having 4 to 26 carbon atoms.

[0038] In addition to the above, the ester-based base oil may also be an ester of an aliphatic dihydric alcohol such as ethylene glycol, propylene glycol, butylene glycol, 2-butyl-2-ethylpropanediol, or 2,4-diethyl-pentanediol with a linear or branched saturated fatty acid. The linear or branched saturated fatty acid is preferably a monovalent linear or branched saturated fatty acid having 4 to 30 carbon atoms.

[0039] Examples of the ether-based base oil include polyglycols and (poly)phenyl ethers. Examples of the polyglycols include polyethylene glycols and polypropylene glycols, and derivatives thereof. Examples of the (poly)phenyl ethers include alkylated diphenyl ethers such as monoalkylated diphenyl ethers and dialkylated diphenyl ethers, alkylated tetraphenyl ethers such as monoalkylated tetraphenyl ethers and dialkylated tetraphenyl ethers, and alkylated pentaphenyl ethers such as pentaphenyl ethers, monoalkylated pentaphenyl ethers, and dialkylated pentaphenyl ethers.

[0040] The base oil may contain base oil components other than the hydrocarbon oil, such as phosphate esters, silicone oils, and fluorine oils.

[0041] (2) Inactivating agent The inactivator contained in the thermally conductive composition inhibits deterioration of the hydrocarbon oil caused by the catalytic action of the copper powder, thereby imparting high thermal stability to the thermally conductive composition.

[0042] The deactivating agent may be a heterocyclic compound having an imino group, and is preferably benzotriazole or a derivative thereof.

[0043] The content of the deactivator is preferably 0.3 parts by mass or more relative to 100 parts by mass of the base oil, more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more. This makes it possible to more effectively suppress the deterioration of the hydrocarbon oil due to the catalytic action of the silver-coated copper powder. The content of the deactivator is preferably 5.0 parts by mass or less relative to 100 parts by mass of the base oil, more preferably 3.0 parts by mass or less, and even more preferably 2.0 parts by mass or less. Even if the content exceeds 5.0 parts by mass, the effect of suppressing the deterioration of the hydrocarbon oil does not change, and by containing the deactivator at a rate of 5.0 parts by mass or less, the content of other components can be relatively increased.

[0044] (3) Other additives The thermally conductive composition according to the present embodiment may contain other additives as necessary within the range that does not impair the characteristics of the present invention. As the other additives, additives for adjusting the characteristics of the thermally conductive composition, such as antioxidants, secondary antioxidants, rust inhibitors, corrosion inhibitors, thickeners, thickeners, diffusion inhibitors, and dispersants, may be used.

[0045] In particular, since the thermally conductive composition according to the present embodiment contains silver-coated copper powder that can impart high thermal conductivity to the thermally conductive composition even in a relatively small amount, it is possible to relatively increase the contents of other components. For example, when the thermally conductive composition according to the present embodiment is used as a thermally conductive grease, a predetermined amount of a thickener may be contained in order to control the consistency of the thermally conductive grease.

[0046] <Method of manufacturing thermally conductive composition> The thermally conductive composition according to the present embodiment is produced by mixing the components. The production method is not particularly limited as long as the components can be mixed uniformly.

[0047] Specifically, the production method may involve kneading the mixture using a planetary mixer, a rotation / revolution mixer, or the like, and then kneading the mixture uniformly using a three-roll mill. EXAMPLES

[0048] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0049] A thermally conductive composition (thermally conductive grease) having the composition shown in Table 1 below was prepared using the materials shown in (1) to (3) below.

[0050] (Thermal conductive grease composition) (1) Inorganic powder filler Average particle size: 5μm Copper powder: Silver coating amount 0 mass% Silver-coated copper powder A: Silver coating amount 3.0% by mass Silver-coated copper powder B: Silver coating amount 5.0% by mass Silver-coated copper powder C: Silver coating amount 10.0% by mass Alumina Powder (2) Base oil Ester oil (High Temp Oil ES-Q manufactured by Sumitomo Lubricants Co., Ltd.) (3) Inactivating agent Benzotriazole (manufactured by Lubrizol Japan Co., Ltd.)

[0051] (Thermal Conductive Grease Manufacturing Method) Materials (1) to (3) were blended as shown in Table 1 below and mixed in a planetary mixer to form a grease. Then, the materials were kneaded using a triple roll mill to thoroughly disperse the materials, thereby producing the thermally conductive greases of the examples and comparative examples.

[0052] [Evaluation of thermal conductive grease] (Thermal conductivity evaluation) The thermal conductivity was measured at room temperature using a rapid thermal conductivity meter QTM-500 manufactured by Kyoto Electronics Manufacturing Co., Ltd. The evaluation results are shown in Table 1 (in Table 1, indicated as "thermal conductivity"). Thermally conductive greases with a thermal conductivity of 3.0 W / mk or more were judged to be good.

[0053] (Thermal stability evaluation) As an accelerated test for evaluating thermal stability, the time required for hardening in a 250°C environment was evaluated. The thermal conductive greases of the examples and comparative examples were applied to a glass substrate with an area of ​​80 mm x 80 mm and a thickness of 100 μm to prepare evaluation samples. The evaluation samples were placed in a thermostatic chamber at 250°C, and the evaluation samples were taken out of the thermostatic chamber every hour to check the degree of hardening of the thermal conductive grease.

[0054] If the thermal conductive grease maintained its fluidity, it was returned to the thermostatic chamber and the test continued. On the other hand, if the thermal conductive grease lost its fluidity, the test was stopped and the time at which it was stopped was recorded as the curing time of the thermal conductive grease. The evaluation results are shown in Table 1 (in Table 1, it is indicated as "thermal stability").

[0055] The fluidity of the thermal conductive grease was confirmed by scratching the thermal conductive grease with a metal spatula. Thermal conductive grease with a hardening time of 5 hours or more was judged to be good.

[0056] (Applicability evaluation) The spreadability was evaluated based on the consistency of the thermally conductive grease at room temperature. The consistency was measured according to the JIS K2220 grease "consistency" measurement method. The evaluation results are shown in Table 1 (in Table 1, indicated as "consistency").

[0057] [Table 1]

[0058] As can be seen from Table 1, the examples within the scope of the present invention showed good results, with thermal conductivity of 3.2 W / mk or more and thermal stability (curing time at 250° C.) of 6 hours or more.

[0059] In particular, the thermally conductive greases of Examples 3 and 4, in which the content of the deactivator was 1.00 part by mass or more per 100 parts by mass of base oil, had a longer curing time at 250°C and further improved thermal stability, even compared to the thermally conductive greases of Examples 1 and 2, in which the content of the deactivator was less than 1.00 part by mass.

[0060] In addition, the thermal conductive grease of Example 3, in which the amount of silver coating is 5.0 parts by mass per 100 parts by mass of copper powder, had a longer hardening time at 250°C and further improved thermal stability, compared to the thermal conductive grease of Example 6, in which the amount of silver coating is 3.0 parts by mass per 100 parts by mass of copper powder. The thermal conductive grease of Example 1, in which the amount of silver coating is 5.0 parts by mass per 100 parts by mass of copper powder, and the thermal conductive grease of Example 5, in which the amount of silver coating is 10.0 parts by mass per 100 parts by mass of copper powder, had the same hardening time at 250°C. From this, it can be seen that by having a silver coating amount of 5.0 parts by mass or more per 100 parts by mass of copper powder, the hardening time at 250°C is longer and thermal stability is further improved.

[0061] On the other hand, the thermally conductive greases of Comparative Examples 1 and 2, which contained copper powder not coated with silver as an inorganic powder filler, had a short curing time at 250° C. and reduced thermal stability. The thermally conductive grease of Comparative Example 2 contained a deactivator, but compared with the thermally conductive greases of Examples 1 to 6, the curing time at 250° C. was short and sufficient thermal stability was not obtained.

[0062] Furthermore, the thermally conductive grease of Comparative Example 3, which contained silver-coated copper powder as an inorganic powder filler and did not contain a deactivator, had a shorter curing time at 250°C than the thermally conductive greases of Examples 1 to 6, and did not obtain sufficient thermal stability.

[0063] The thermally conductive grease of Comparative Example 4, which contained alumina powder as an inorganic powder filler, did not contain a deactivator, and although it had a long curing time at 250°C and good thermal stability, it did not obtain sufficient thermal conductivity.

[0064] In the thermal conductive grease of Comparative Example 5, in which the content of alumina powder was increased to obtain sufficient thermal conductivity compared to that of Comparative Example 4, the hardening time at 250°C was long, the thermal stability was good, and sufficient thermal conductivity was obtained, but the consistency was reduced. This is because the content of the base oil component was relatively reduced, making it difficult to control the consistency. Thus, it can be seen that the thermal conductive grease containing alumina powder as an inorganic powder filler has poor handleability, for example, making it difficult to control the consistency.

Claims

1. A thermally conductive composition for forming a thermally conductive layer disposed between a heat generating component and a heat dissipating component, the thermally conductive layer conducting heat from the heat generating component to the heat dissipating component and dissipating heat from the heat generating component, A base oil composition and an inorganic powder filler are included, The inorganic powder filler comprises silver-coated copper powder, The content of the copper powder in the thermally conductive composition is in the range of 85% by mass or more, The base oil composition contains a base oil containing a hydrocarbon oil and a deactivator, The deactivating agent contains benzotriazole. Thermally conductive composition.

2. The content of the deactivator is 0.50 parts by mass or more per 100 parts by mass of the base oil. The thermally conductive composition of claim 1 .

3. The content of the deactivator is 0.50 parts by mass or more and 5.00 parts by mass or less with respect to 100 parts by mass of the base oil. The thermally conductive composition of claim 2.

4. The amount of the silver coating on the copper powder is 5.0 parts by mass or more per 100 parts by mass of the copper powder. The thermally conductive composition according to any one of claims 1 to 3.

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