JP2021105135A - Thermally conductive composition - Google Patents

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

The present invention relates to thermally conductive compositions.

Among the semiconductor parts used in electronic devices, there are parts that generate heat during use, such as power semiconductors for power control such as computer CPUs, inverters, and converters. In order to protect these semiconductor parts from heat and make them function normally, there is a method of conducting the generated heat to heat dissipation parts such as a heat sink to dissipate heat. The heat conductive grease is applied between the semiconductor component and the heat radiating component so as to be in close contact with each other, and is used to efficiently conduct the heat of the semiconductor component to the heat radiating component. In recent years, the performance of electronic devices using these semiconductor components has been improved and compact and high-density mounting has been advanced, and higher heat resistance is required for the heat conductive composition used for heat dissipation measures.

As such a heat conductive composition, a heat conductive composition based on silicone oil and containing a heat conductive filler such as zinc oxide or alumina powder is disclosed (see Patent Documents 1 and 2).

Further, as a thermally conductive composition used in a place where insulation of electronic parts is not required, aluminum powder or copper powder which is a metal powder is mixed with a base oil such as silicone oil in order to further increase the thermal conductivity. The thermally conductive composition is disclosed (see Patent Documents 3 and 4). Conventionally, an oil having high heat resistance such as silicone oil has been used for the heat conductive composition required to have heat resistance.

Japanese Unexamined Patent Publication No. 51-055870 Japanese Unexamined Patent Publication No. 50-105573 Japanese Unexamined Patent Publication No. 2000-063873 Japanese Unexamined Patent Publication No. 2006-137930

When silicone oil is used as the base oil contained in the heat conductive composition, the free siloxane contained in the silicone oil or generated by thermal decomposition of the silicone oil causes the contact portion thereof. There is a concern that it may cause a power failure. Therefore, as the base oil contained in the thermally conductive composition, a highly heat-resistant base oil other than the silicone oil may be required. Examples of the base oil having heat resistance other than the silicone oil include a base oil containing a hydrocarbon oil.

Here, as the heat conductive filler contained in the heat conductive composition, copper powder which is a metal powder can be mentioned. In particular, copper is a material having 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.

However, the present inventors have clarified that when copper powder is contained in a hydrocarbon oil, the hydrocarbon oil is oxidized over time by the catalytic action of the copper powder in a high thermal environment. Therefore, in the thermally conductive composition containing the copper powder and the hydrocarbon oil, the hydrocarbon oil may be oxidized in a high thermal environment to cure the thermally conductive composition. As described above, the thermally conductive composition containing the copper powder and the hydrocarbon oil has low thermal stability.

Further, if alumina or silica is contained in the hydrocarbon oil instead of the copper powder as the heat conductive filler, the oxidation of the hydrocarbon oil over time can be suppressed, but these heat conductive fillers are compared with the copper powder. The thermal conductivity is low, and it is not possible to impart high thermal conductivity to the thermally conductive composition. Further, when the amount of the heat conductive filler is increased so as to obtain high heat conductivity as the heat conductive composition, the content of other components such as the base oil component is relatively reduced, and for example, the consistency can be controlled. Handleability is reduced, such as becoming difficult.

The present invention has been made in view of such a problem, and even when a base oil containing a hydrocarbon oil is used, the present invention has excellent thermal stability and thermal conductivity, and has good handleability. It is an object of the present invention to provide a sex composition.

As a result of diligent studies to solve the above-mentioned problems, the present inventors have made the above-mentioned problems by containing a copper powder coated with silver as a heat conductive filler and further containing a specific inactivating agent. We have found that we can solve the problem, and have completed the present invention.

(1) The first aspect of the present invention is a thermally conductive composition containing a base oil composition and an inorganic powder filler, wherein the inorganic powder filler contains a silver-coated copper powder. However, the base oil composition is a heat conductive composition containing a base oil containing a hydrocarbon oil and an inactivating agent.

(2) The second aspect of the present invention is that, in the first invention, the inactivating agent is a thermally conductive composition containing benzotriazole.

(3) The third aspect of the present invention is the thermal conductive composition in which the inactivating agent is contained in a proportion of 0.50 parts by mass or more with respect to 100 parts by mass of the base oil in the first or second invention. It is a thing.

(4) The fourth aspect of the present invention is that in the third aspect, the heat contained in the inactivating agent at a ratio of 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. It is a conductive composition.

(5) Fifth of the present invention, in any one of the first to fourth inventions, the amount of silver coated on the copper powder is 5.0 parts by mass or more with respect to 100 parts by mass of the copper powder. Is a thermally conductive composition.

According to the present invention, it is possible to provide a thermally conductive composition having excellent thermal stability and thermal conductivity and good handleability even when a base oil containing a hydrocarbon oil is used.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and may be carried out with appropriate modifications within the scope of the object of the present invention. can.

≪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 a silver-coated copper powder, and the base oil composition is characterized by containing a base oil containing a hydrocarbon oil and an inactivating agent.

By using an inorganic powder filler containing silver-coated copper powder (hereinafter, may be referred to as silver-coated copper powder) as a heat conductive filler, the surface of the copper powder and the hydrocarbon oil can be brought into contact with each other. It is possible to prevent contact. Then, by incorporating a specific inactivating agent into the base oil composition in such a state, it is possible to effectively suppress the temporal oxidation of the hydrocarbon oil due to the catalytic action of the copper powder in a high thermal environment. Is possible. Moreover, copper and silver have extremely high thermal conductivity, and by containing the silver-coated copper powder, high thermal conductivity can be imparted to the thermally conductive composition. As described above, the thermally conductive composition according to the present embodiment is excellent in thermal conductivity and thermal stability.

Furthermore, the silver-coated copper powder can impart high thermal conductivity to the thermally conductive composition even with a relatively small content, and the content of the silver-coated copper powder is increased so as to obtain high thermal conductivity. You don't have to let it. Therefore, it is possible to relatively increase the content of other components such as the base oil component, and the handleability is good.

Hereinafter, each component contained in the heat conductive composition will be described.

[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). As a result, deterioration of the hydrocarbon oil due to contact with the copper powder in a high thermal environment is suppressed.

The silver-coated copper powder may have silver present on at least a part of the surface of the copper powder, but it is preferable that the silver is coated on the entire surface of the copper powder. It is possible to reliably prevent contact between the surface of the copper powder and the hydrocarbon oil, and it is possible to more effectively suppress the deterioration of the hydrocarbon oil.

The amount of silver coated in the silver-coated copper powder is not particularly limited, but is preferably 3.0 parts by mass or more, preferably 5.0 parts by mass or more with respect to 100 parts by mass of the copper powder. It is preferable to have. When the amount of silver coated is 3.0 parts by mass or more, a uniform silver film is formed on the copper surface, so that contact between the surface of the copper powder and the hydrocarbon oil can be prevented more effectively. Is possible. The amount of silver coated is preferably 20.0 parts by mass or less with respect to 100 parts by mass of copper powder, and more preferably 15.0 parts by mass or less. When the ratio is 20.0 parts by mass or less with respect to 100 parts by mass of the copper powder, the cost increase due to the silver coating can be suppressed. Further, it is possible to prevent the silver film from being worn.

The average particle size of the silver-coated copper powder is not particularly limited, but is preferably 0.4 μm or more, and preferably 1.0 μm or more. When the average particle size is 0.4 μm or more, the coatability of the heat conductive composition can be improved, and the film thickness of the heat conductive composition after coating can be stabilized. Further, a plurality of types of silver-coated copper powder having 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 heat conductive composition.

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

The method of coating the copper powder with silver is not particularly limited, and a conventionally known method can be used. For example, electroplating that causes a reduction reaction of silver ions on the surface of copper powder using an external power source to precipitate silver, or electroplating that precipitates silver by the reducing action of chemicals. , The method of coating silver by dry plating may be used. From the viewpoint that a uniform silver film can be formed, a method of coating silver by dry plating is preferable. Examples of the dry plating include vacuum deposition, sputtering, ion plating and the like.

The inorganic powder filler may contain an inorganic powder filler 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 is, for example, a metal oxide, an inorganic nitride, a metal (including an alloy), and a silicon compound. , Carbon material and other powders.

(Base oil composition)
The base oil composition contains a base oil containing a hydrocarbon oil and an inactivating agent. Hereinafter, each component contained in the base oil composition will be described.

(1) Base oil The base oil imparts lubricity to the heat conductive composition by being contained in the heat conductive composition.

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

Mineral oil is, for example, a mineral oil-based lubricating oil distillate refined by appropriately combining refining methods such as solvent extraction, solvent dewaxing, hydrorefining, hydrocracking, and wax isomerization. , Brightstock, high viscosity index base oil and the like can be used. The mineral oil used as the base oil is preferably a highly hydrorefined high viscosity index base oil.

Examples of the synthetic hydrocarbon oil include those obtained by polymerizing alpha olefins produced from ethylene, propylene, butene, and derivatives thereof as raw materials, alone or in combination of two or more. The alpha olefin preferably has 6 or more carbon atoms and 14 or less carbon atoms.

Specific examples of synthetic hydrocarbon oils used as base oils are polyalphaolefin (PAO), which is an oligomer of 1-decene and 1-dodecene, polybutene, which is an oligomer of 1-butene and isobutylene, ethylene, propylene, and alphaolefin. Examples thereof include co-oligomers. Further, alkylbenzene, alkylnaphthalene and the like can also be used.

Examples of the ester-based base oil include diesters and polyol esters. Examples of the diester include esters of dibasic acids such as adipic acid, azelaic acid, sebacic acid, and dodecane diic acid. The dibasic acid is preferably an aliphatic dibasic acid having 4 to 36 carbon atoms. The alcohol residue constituting the ester portion is preferably a monohydric alcohol residue having 4 to 26 carbon atoms.

The polyol ester is an ester of a neopentyl polyol in which a hydrogen atom does not exist on the carbon at the β-position, and specific examples thereof include carboxylic acid esters such as neopentyl glycol, trimethylolpropane, and pentaerythritol. The carboxylic acid residue constituting the ester portion is preferably a monocarboxylic acid residue having 4 or more carbon atoms and 26 or less carbon atoms.

In addition to the above, the ester-based base oil is directly composed of an aliphatic dihydric alcohol such as ethylene glycol, propylene glycol, butylene glycol, 2-butyl-2-ethylpropanediol, and 2,4-diethyl-pentanediol. Esters with chain or branched saturated fatty acids can also be used. The straight-chain or branched-chain saturated fatty acid is preferably a monovalent straight-chain or branched-chain saturated fatty acid having 4 to 30 carbon atoms.

Examples of the ether-based base oil include polyglycol and (poly) phenyl ether. Examples of polyglycol include polyethylene glycol, polypropylene glycol, and derivatives thereof. (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, pentaphenyl ethers, and monoalkylated penta. Examples thereof include alkylated pentaphenyl ethers such as phenyl ethers and dialkylated pentaphenyl ethers.

The base oil may contain a base oil component other than the hydrocarbon oil. For example, phosphoric acid ester, silicone oil, fluorine oil and the like can be mentioned.

(2) Inactivating agent By being contained in the thermally conductive composition, the inactivating agent suppresses the deterioration of the hydrocarbon oil due to the catalytic action of the copper powder, and is highly thermally stable in the thermally conductive composition. Give sex.

Examples of the inactivating agent include heterocyclic compounds having an imino group, but benzotriazole or a derivative thereof is preferable.

The content of the inactivating agent is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and 1.0 part by mass with respect to 100 parts by mass of the base oil. It is more preferable to contain it in a proportion of 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 inactivating agent is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and 2.0 parts by mass or less with respect to 100 parts by mass of the base oil. It is more preferable to contain it in a proportion of parts by mass or less. Even if it is contained in excess of 5.0 parts by mass, the effect of suppressing deterioration of the hydrocarbon oil does not change, and by containing it in a proportion of 5.0 parts by mass or less, the content of other components is relatively increased. Can be increased.

(3) Other Additives The thermally conductive composition according to the present embodiment may contain other additives, if necessary, as long as the characteristics of the present invention are not impaired. Other additives include antioxidants, secondary antioxidants, rust inhibitors, corrosion inhibitors, thickeners, thickeners, diffusion inhibitors, dispersants, etc., which adjust the properties of the thermally conductive composition. Additives can be used.

In particular, the thermally conductive composition according to the present embodiment is relatively different because it contains a silver-coated copper powder capable of imparting high thermal conductivity to the thermally conductive composition even with a relatively small content. It is possible to increase the content of the components of. For example, when the thermally conductive composition according to the present embodiment is used as the thermally conductive grease, a predetermined amount of thickener may be contained in order to control the consistency of the thermally conductive grease.

≪Manufacturing method of thermally conductive composition≫
The thermally conductive composition according to the present embodiment is produced by mixing each component. The production method is not particularly limited as long as the components can be mixed uniformly.

Specifically, as a manufacturing method, a method of kneading with a planetary mixer, a rotation / revolution mixer, or the like, and further uniformly kneading with three rolls can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention. The present invention is not limited to the following examples.

Using each of the materials shown in (1) to (3) below, a thermally conductive composition (thermally conductive grease) having the composition shown in Table 1 below was prepared.

(Composition of thermally conductive grease)
(1) Inorganic powder filler Average particle size: 5 μm
Copper powder: Silver coating amount 0% by 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 Sumiko Lubricant Co., Ltd.)
(3) Inactivating agent Benzotriazole (manufactured by Nippon Lubrizol Co., Ltd.)

(Manufacturing method of thermally conductive grease)
As shown in Table 1 below, the materials (1) to (3) were blended and mixed with a planetary mixer to prepare a grease. Then, each material was sufficiently dispersed by kneading with three rolls to produce the heat conductive greases of Examples and Comparative Examples.

[Evaluation of thermally conductive grease]
(Evaluation of thermal conductivity)
The thermal conductivity was measured at room temperature using a rapid thermal conductivity meter QTM-500 manufactured by Kyoto Denshi Kogyo Co., Ltd. The evaluation results are shown in Table 1 (indicated as "thermal conductivity" in Table 1). The heat conductive grease having a thermal conductivity of 3.0 W / mk or more was judged to be good.

(Evaluation of thermal stability)
As an accelerated test for thermal stability evaluation, the time required for curing in an environment of 250 ° C. was evaluated. The heat conductive greases of Examples and Comparative Examples were applied on a glass substrate in an area of 80 mm × 80 mm to a thickness of 100 μm to prepare an evaluation sample. This evaluation sample was allowed to stand in a constant temperature bath at 250 ° C., and the evaluation sample was taken out from the constant temperature bath every hour to check the degree of curing of the heat conductive grease.

If the thermally conductive grease maintained its fluidity, it was returned to the constant temperature bath and the test was continued. On the other hand, when the heat conductive grease lost its fluidity, the test was terminated and the time was defined as the curing time of the heat conductive grease. The evaluation results are shown in Table 1 (indicated as "thermal stability" in Table 1).

The fluidity of the thermally conductive grease was confirmed by scratching the thermally conductive grease with a metal spatula. As for the heat conductive grease, those having a curing time of 5 hours or more were judged to be good.

(Evaluation of coatability)
The coatability was evaluated by the consistency of the heat conductive grease at room temperature. Consistency was measured according to the "consistency" measuring method of JIS K2220 grease. The evaluation results are shown in Table 1 (indicated as "concentration" in Table 1).

From Table 1, in the examples within the scope of the present invention, the thermal conductivity was 3.2 W / mk or more, and the thermal stability (curing time at 250 ° C.) was 6 hours or more, showing good results.

In particular, the heat conductive greases of Examples 3 and 4 having an inactivating agent content of 1.00 parts by mass or more with respect to 100 parts by mass of the base oil have an inactivating agent content of 1.00 parts by mass. Compared with the heat conductive greases of Examples 1 and 2 which are less than, the curing time at 250 ° C. was longer and the thermal stability was further improved.

Further, the heat conductive grease of Example 3 having a silver coating amount of 5.0 parts by mass with respect to 100 parts by mass of copper powder has a silver coating amount of 3.0 parts by mass with respect to 100 parts by mass of copper powder. Compared with the heat conductive grease of Example 6, the curing time at 250 ° C. was longer and the thermal stability was further improved. Then, the heat conductive grease of Example 1 in which the amount of silver coated is 5.0 parts by mass with respect to 100 parts by mass of copper powder, and the amount of silver coated with respect to 100 parts by mass of copper powder is 10.0 parts by mass. The thermally conductive grease of Example 5 had the same curing time at 250 ° C. From this, it can be seen that when the coating amount of silver is 5.0 parts by mass or more with respect to 100 parts by mass of the copper powder, the curing time at 250 ° C. becomes longer and the thermal stability is further improved.

On the other hand, the heat conductive greases of Comparative Examples 1 and 2 containing a copper powder not coated with silver as an inorganic powder filler had a short curing time at 250 ° C. and had reduced thermal stability. Although the thermally conductive grease of Comparative Example 2 contained an inactivating agent, it had a shorter curing time at 250 ° C. and sufficient thermal stability as compared with the thermally conductive grease of Examples 1 to 6. Was not obtained.

Further, the heat conductive grease of Comparative Example 3 containing silver-coated copper powder as an inorganic powder filler and not containing an inactivating agent was cured at 250 ° C. as compared with the heat conductive grease of Examples 1 to 6. The time was short and sufficient thermal stability could not be obtained.

Further, the thermally conductive grease of Comparative Example 4 containing alumina powder as an inorganic powder filler has a long curing time of 250 ° C. and good thermal stability even though it does not contain an inactivating agent. However, sufficient thermal conductivity could not be obtained.

The heat conductive grease of Comparative Example 5 in which the content of the alumina powder was increased as compared with the heat conductive grease of Comparative Example 4 so as to obtain sufficient thermal conductivity had a long curing time of 250 ° C. and was thermally stable. The properties were good and sufficient thermal conductivity was obtained, but the consistency was reduced. This is because the content of the base oil component is relatively reduced, making it difficult to control the consistency. As described above, it can be seen that the heat conductive grease containing alumina powder as an inorganic powder filler has reduced handleability, for example, it becomes difficult to control the consistency.

Claims (5)

A thermally conductive composition containing a base oil composition and an inorganic powder filler.
The inorganic powder filler contains silver-coated copper powder and contains.
The base oil composition is a thermally conductive composition containing a base oil containing a hydrocarbon oil and an inactivating agent. The thermally conductive composition according to claim 1, wherein the inactivating agent contains benzotriazole. The heat conductive composition according to claim 1 or 2, wherein the inactivating agent is contained in a proportion of 0.50 parts by mass or more with respect to 100 parts by mass of the base oil. The thermally conductive composition according to claim 3, wherein the inactivating agent is contained in a ratio of 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 heat conductive composition according to any one of claims 1 to 4, wherein the amount of silver coated on the copper powder is 5.0 parts by mass or more with respect to 100 parts by mass of the copper powder.