JP7155661B2 - thermal grease - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermally conductive grease that prevents base oil from diffusing and has excellent thermal conductivity.

Semiconductor parts used in electronic devices include heat-generating parts that generate heat during use, such as computer CPUs, Peltier devices, LEDs, and power semiconductors for power supply control such as inverters.

In order to protect these heat-generating parts from heat and to function normally, there is a method of conducting the generated heat to a heat-radiating part (cooling device) such as a heat spreader or a heat sink to dissipate the heat. Thermally conductive grease is applied between the heat-generating component and the heat-radiating component so as to bring them into close contact with each other, and is used to efficiently conduct heat from the heat-generating component to the heat-radiating component. Thermally conductive grease is a base oil such as liquid hydrocarbon, silicone oil, fluorine oil, etc., and inorganic powder filler with high thermal conductivity (metal oxide such as zinc oxide, aluminum oxide, etc., boron nitride, silicon nitride, It is a grease-like composition in which a large amount of inorganic nitrides such as aluminum nitride and metal powders such as aluminum and copper are dispersed.

More specifically, thermally conductive grease is used for thermal contact interfaces between heat-generating parts such as computer CPUs and heat-radiating parts such as heat sinks, and for heat-generating parts such as high-output inverters mounted on hybrid and electric vehicles. and heat-dissipating parts such as a heat spreader. In recent years, semiconductor elements in these electronic devices have increased in heat generation density and heat generation due to miniaturization and high performance, and are often incorporated in close proximity to heat-generating parts that are other semiconductor parts. . Therefore, the thermally conductive grease applied to the thermal contact interface is exposed to higher temperatures than ever before.

When thermally conductive grease is used for a long period of time in such a high-temperature and sealed environment, the consistency of some types of thermally conductive grease may be greatly reduced. When using thermally conductive grease, if the consistency drops significantly or hardens, cracks and voids may occur in the thermally conductive grease applied to the thermal contact interface. may decrease.

Such a decrease in consistency is caused by deterioration of the thermally conductive grease applied to the thermal contact interface, as well as diffusion of the base oil contained in the thermally conductive grease, resulting in a decrease in the ratio of the base oil in the thermally conductive grease. may occur in some cases. Moreover, such diffusion of the base oil component may adversely affect other semiconductor components in the vicinity of the diffused base oil component. Therefore, the thermally conductive grease is required to have the performance of reducing the diffusion of the base oil contained in the thermally conductive grease in addition to the high thermal conductivity.

As a countermeasure to such problems, Patent Document 1 discloses, as an example, a base oil diffusion preventing agent having perfluoroalkyl groups at both ends or a gas oil diffusion preventing agent having methyl groups at both ends and including a perfluoroalkyl group. A thermally conductive grease containing

JP 2014-194006 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermally conductive grease capable of improving the diffusion prevention performance of a base oil as compared with conventional thermally conductive greases.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found a heat conducting agent containing a base oil diffusion inhibitor having a perfluoroalkyl group at one end and a hydrogen group or a phosphoric acid group at the other end. The inventors have found that the above problems can be solved by using a non-toxic grease, and have completed the present invention.

A first aspect of the present invention is a thermally conductive grease containing an inorganic powder filler, a base oil, and a base oil diffusion inhibitor, wherein the base oil diffusion inhibitor is It is a thermally conductive grease having a fluoroalkyl group and a hydrogen group or a phosphoric acid group at the other end.

A second aspect of the present invention is the thermally conductive grease according to the first aspect, wherein the base oil diffusion inhibitor is a compound having a structure represented by the following formula (1).
R—(C _n H _2n O) _m —X (1)
(In the above formula (1), R is a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms, n is an integer of 1 to 10, and m is 2 to 100 is an integer, and X is a hydrogen group or a phosphate group.)

A third invention of the present invention is the first or second invention, wherein the content of the base oil diffusion inhibitor is 0.001% by mass or more and 1% by mass or less with respect to 100% by mass of the thermally conductive grease. It is a thermally conductive grease, which is a proportion.

A fourth invention of the present invention is the thermally conductive grease according to any one of the first to third inventions, further containing an antioxidant.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the content of the inorganic powder filler is 70% by mass or more and 97% by mass or less with respect to 100% by mass of the thermally conductive grease. The content of the base oil is 2% by mass or more and 29% by mass or less with respect to 100% by mass of the thermally conductive grease.

The thermally conductive grease of the present invention can effectively prevent diffusion of the base oil.

FIG. 3 is a plan view showing an example of a bleeding-out state on frosted glass;

Specific embodiments of the present invention (hereinafter referred to as "present embodiments") will be described in detail below. It should be noted that the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention. Further, in this specification, the notation "~" means "more than" and "less than", and the notation "X: Y to A: B" means "X: Y" and "A: B" themselves. and means a range between "X:Y" and "A:B".

≪1. Thermally conductive grease≫
The thermally conductive grease according to the present embodiment (hereinafter sometimes simply referred to as grease) contains an inorganic powder filler, a base oil, and a base oil diffusion inhibitor. Each component contained in the thermally conductive grease will be described below.

[About each component]
(Inorganic powder filler)
The inorganic powder filler imparts high thermal conductivity to the grease. The inorganic powder filler used in the thermally conductive grease according to the present embodiment is not particularly limited as long as it has higher thermal conductivity than the base oil. Metal oxides, inorganic nitrides, metals (including alloys) ), silicon compounds, carbon materials and the like are preferably used. One type of inorganic powder filler may be used, or two or more types may be used in combination.

More specifically, metal oxides include zinc oxide, magnesium oxide, and aluminum oxide. Examples of inorganic nitrides include aluminum nitride and boron nitride. Copper, aluminum, silver, etc. can be mentioned as a metal. Examples of silicon compounds include silicon carbide and silica. Carbon materials include diamond, graphite, fullerene, carbon nanotube, carbon nanohorn, and the like.

As inorganic powder fillers, non-conductive substances such as semiconductors and ceramics such as zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride, boron nitride, silicon carbide, silica, and diamond are used when electrical insulation is required. Powders are preferred, powders of zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride, boron nitride, silicon carbide and silica are more preferred, and powders of zinc oxide, aluminum oxide and aluminum nitride are particularly preferred.

In addition, from the viewpoint of having high thermal conductivity among the above inorganic powder fillers, it is selected from the group consisting of copper, aluminum, silver, zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride boron nitride and silicon carbide. At least one or more is preferable. If there is no requirement for electrical properties, it is possible to use a combination of metal powder or carbon material powder and non-conductive substance powder.

When only fine particles are used as the inorganic powder filler, it is preferable to use inorganic powder having an average particle size of 0.15 μm or more and less than 3 μm. By setting the average particle diameter to 0.15 μm or more, the ratio between the amount of the dispersant that makes the surface of the inorganic powder filler lipophilic and the amount of the liquid component (base oil, etc.) is well balanced, and when highly filled A higher consistency can be obtained by On the other hand, by setting the average particle size to less than 3 μm, the filling of the inorganic powder filler can be easily brought to a close-packed state, the thermal conductivity can be higher, and the separation of the base oil is more effective. can be effectively suppressed. In this specification, fine particles mean powders with an average particle size of less than 3 μm, and coarse particles, which will be described later, mean powders with an average particle size of 3 μm or more.

Moreover, it is preferable to combine two or more kinds of fine particles having different average particle sizes for the above inorganic powder filler. As a result, the filling of the inorganic powder filler in the thermally conductive grease can be easily brought into a close-packed state, and separation of the base oil can be more effectively suppressed.

Even when two or more types of fine particles having different average particle sizes are combined, the average particle size of each fine particle is 0.15 μm or more and less than 3 μm from the viewpoint of thermal conductivity when thermally conductive grease is mounted. is preferred. When fine grains with different average grain sizes are used in combination, the average grain size of fine grains with a small average grain size is an average of 10% or more and 60% or less of the average grain size of fine grains with a large average grain size. It is preferably a particle size, more preferably an average particle size of 20% or more and 55% or less. Further, the mixing ratio of fine particles with a small average particle size and fine particles with a large average particle size is preferably in the range of 5:95 to 85:15 in mass ratio.

Furthermore, when fine grains and coarse grains are combined as the inorganic powder filler, the above fine grains can be combined with coarse inorganic powders having an average grain size of 3 μm or more and 50 μm or less. By setting the average particle diameter of the coarse particles in the inorganic powder filler to 3 μm or more, it is possible to easily obtain a high thermal conductivity of the thermally conductive grease. By setting the average particle diameter of the coarse particles in the inorganic powder filler to 50 μm or less, it is possible to prevent the coating film of the thermally conductive grease from becoming thicker than necessary and to enhance the heat dissipation performance of the coating film during mounting.

When the inorganic powder filler is a combination of fine particles and coarse particles, the coarse particles may be a combination of two or more powders having different average particle sizes. Also in this case, the average particle size of each coarse particle is preferably 3 μm or more and 50 μm or less from the viewpoint of the thermal conductivity of the thermally conductive grease and the heat dissipation performance of the coating film during mounting.

In the thermally conductive grease according to this embodiment, the average particle diameter of the inorganic powder filler can be calculated as the volume average diameter of the particle size distribution measured by the laser diffraction scattering method (according to JIS R 1629:1997).

Further, when combining fine-grained and coarse-grained inorganic powder fillers, the mass ratio (fine grains: coarse grains) is preferably in the range of 20:80 to 85:15. By setting the blending ratio of fine particles and coarse particles within the above range, high consistency can be achieved from the balance between the amount of dispersant that makes the surface of the inorganic powder filler lipophilic and the amount of liquid components (base oil, etc.). Obtainable. In addition, it is suitable for making the balance between coarse particles and fine particles more dense, so that separation of the base oil can be more effectively suppressed. When two or more types of coarse particles are combined, the mass ratio of the coarse particles is not particularly limited. % or less.

The content of the inorganic powder filler is preferably 70% by mass or more and 97% by mass or less. The higher the content of the inorganic powder filler, the better the thermal conductivity, and the content is preferably 75% by mass or more and 97% by mass or less. When the amount is 70% by mass or more, the thermal conductivity of the thermally conductive grease itself can be sufficiently increased, and separation of the base oil can be suppressed to suppress exudation of the base oil, which is preferable. On the other hand, when it is 97% by mass or less, it is possible to suppress a decrease in consistency and to have sufficient malleability, which is preferable.

(base oil)
The base oil imparts lubricity to the thermally conductive grease by being contained in the grease.

As the base oil, various base oils can be used, for example, hydrocarbon-based base oils such as mineral oils and synthetic hydrocarbon oils, ester-based base oils, ether-based base oils, phosphate esters, silicone oils and fluorine oils. Hydrocarbon base oils, ester base oils, and ether base oils are preferred. Silicone oil and fluorine oil with low surface tension are not so preferable in terms of more effectively suppressing oil separation of the base oil. One type of base oil may be used alone, or two or more types may be used in combination.

As the mineral oil, for example, a mineral oil-based lubricating oil fraction is refined by appropriately combining refining techniques such as solvent extraction, solvent dewaxing, hydrorefining, hydrocracking, wax isomerization, etc. 150 neutral oil, 500 neutral oil Oils, bright stocks, high viscosity index base oils, and the like can be used. The mineral oil used for the base oil is preferably a highly hydrorefined high viscosity index base oil.

Synthetic hydrocarbon oils include, for example, those obtained by polymerizing alpha-olefins produced using ethylene, propylene, butene, and derivatives thereof as raw materials, singly or in combination of two or more. Alpha olefins preferably have 6 to 14 carbon atoms.

Specific examples of synthetic hydrocarbon oils include polyalphaolefins (PAO) that are oligomers of 1-decene and 1-dodecene, polybutenes that are oligomers of 1-butene and isobutylene, and co-oligomers of ethylene or propylene and alpha olefins. is mentioned. Alkylbenzene, alkylnaphthalene, or the like can also be used.

Examples of ester-based base oils include diesters and polyol esters. Diesters include esters of dibasic acids such as adipic acid, azelaic acid, sebacic acid and dodecanedioic acid. As the dibasic acid, an aliphatic dibasic acid having 4 or more and 36 or less carbon atoms is preferable. The alcohol residue constituting the ester moiety is preferably a monohydric alcohol residue having 4 or more and 26 or less carbon atoms. The polyol ester is an ester of neopentyl polyol in which no hydrogen atom exists on the β-position carbon, and specific examples include carboxylic acid esters such as neopentyl glycol, trimethylolpropane and pentaerythritol. The carboxylic acid residue constituting the ester moiety is preferably a monocarboxylic acid residue having 4 to 26 carbon atoms.

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

Ether base oils 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 ether and dialkylated diphenyl ether; alkylated tetraphenyl ethers such as monoalkylated tetraphenyl ether and dialkylated tetraphenyl ether; Examples include alkylated pentaphenyl ethers such as pentaphenyl ether and dialkylated pentaphenyl ether.

Phosphate esters include triethyl phosphate, tributyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate and the like.

Here, since the thermally conductive grease is applied to the thermal contact interface of the heat-generating component during mounting, the coating film of the thermally conductive grease is exposed to high temperatures for a long period of time. Therefore, it is desirable that the base oil contained in the thermally conductive grease has excellent thermal oxidation stability. Among the above base oils, synthetic base oils are preferred, and synthetic hydrocarbon oils, ester base oils and ether base oils are preferred. Among these base oils, preferred are polyalphaolefins for synthetic hydrocarbon oils, polyol esters for ester-based base oils, and (poly)phenyl ethers for ether-based base oils as base oils that are particularly excellent in thermal oxidation stability. used as

These polyalphaolefins, (poly)phenyl ethers, and polyol esters may be used alone, but it is preferable to use them in combination of two or more.

When used in combination, the combination of a base oil group consisting of polyalphaolefins or (poly)phenyl ethers and polyol esters in particular results in a relatively high viscosity index and good consistency when the grease is prepared. It is preferable because it is possible to prepare a grease that is high and has excellent applicability. In this case, the content ratio of the base oil group consisting of polyalphaolefin or (poly)phenyl ether to the polyol ester is preferably 95:5 to 30:70, more preferably 90:10 to 50:50, more preferably 85:15 to 65:35.

The kinematic viscosity of the base oil is preferably 10 mm ² /s or more and 1200 mm ² /s or less at 40°C. A kinematic viscosity of 10 mm ² /s or more at 40° C. is preferable because evaporation of the base oil and oil separation at high temperatures tend to be suppressed. Further, it is preferable to set the kinematic viscosity at 40° C. to 1200 mm ² /s or less because it facilitates obtaining a high consistency.

The content of the base oil is preferably 2% by mass or more and 29% by mass or less, more preferably 3% by mass or more and 28% by mass or less, and 3% by mass with respect to 100% by mass of the thermally conductive grease. More than 25% by mass or less is particularly preferable. When the content of the base oil is 2% by mass or more, the oil component contained in the thermally conductive grease becomes an appropriate amount, and the consistency is such that the thermally conductive grease can be maintained in a grease state. It is preferable because it can be maintained. On the other hand, since the content of the base oil is 29% by mass or less, the grease may flow out when placed in a high-temperature environment, or the base oil contained in the grease may separate and cause damage to the area where the grease is applied. It is preferable because it can effectively suppress contamination of the peripheral member with the base oil.

(dispersant)
The dispersant is adsorbed on the surface of the inorganic powder filler contained in the grease, and can improve the affinity between the inorganic powder filler and the base oil. That is, the dispersant functions as a surface modifier for the inorganic powder filler and improves the affinity between the inorganic powder filler and the base oil, thereby improving the consistency of the thermally conductive grease.

Examples of the dispersant include polyglycerin monoalkyl ether compounds, compounds having a carboxylic acid structure such as higher fatty acid esters, and polycarboxylic acid compounds. These may be used alone, or may be used in combination of two or more. In particular, it is preferable to use a polyglycerin monoalkyl ether compound, a compound having a carboxylic acid structure, and a polycarboxylic acid compound together.

The content of the dispersant is preferably 0.001% by mass or more and 3% by mass or less with respect to 100% by mass of the thermally conductive grease. The ratio is more preferably 0.05% by mass or more and 2% by mass or less, more preferably 0.15% by mass or more and 1% by mass or less, and most preferably 0.2% by mass or more and 0.5% by mass. The ratio is as follows.

When the content of the dispersant is 0.001% by mass or more, the effect of further improving the affinity between the inorganic powder filler contained in the grease and the base oil is obtained, and the consistency of the thermally conductive grease is improved. It is preferable because it can be effectively increased.

On the other hand, even if the content of the dispersant exceeds 3% by mass, the properties of the dispersant do not change significantly. A content of the dispersant of 3% by mass or less is preferable because the cost can be reduced.

(Base oil diffusion inhibitor)
The thermally conductive grease according to the present embodiment is characterized by containing a base oil diffusion inhibitor having a specific structure. Specifically, it contains a base oil diffusion inhibitor having a perfluoroalkyl group at one end and a hydrogen group or a phosphoric acid group at the other end.

According to the research of the present inventors, in the thermally conductive grease, by containing a base oil diffusion inhibitor having a perfluoroalkyl group at one end and a hydrogen group or a phosphoric acid group at the other end, It has become clear that the diffusion of oil can be effectively suppressed.

Examples of base oil diffusion inhibitors include compounds having a structure represented by the following general formula (1).

(Chem. 1)
R—(C _n H _2n O) _m —X (1)

Here, in the above formula (1), R is a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms, n is an integer of 1 to 10, m is 2 to 100 It is an integer below. X is a hydrogen group or a phosphate group.

The content of the base oil diffusion inhibitor is preferably 0.001% by mass or more and 1% by mass or less, and 0.1% by mass or more and 0.5% by mass or less with respect to 100% by mass of the thermally conductive grease. More preferably, the ratio is more preferably 0.1% by mass or more and 0.2% by mass or less.

When the content of the base oil diffusion inhibitor is 0.001% by mass or more, the diffusion of the base oil can be more effectively suppressed, which is preferable. On the other hand, even if the content of the base oil diffusion inhibitor exceeds 1% by mass, the properties of the base oil diffusion inhibitor do not change significantly. It is preferable that the content of the base oil diffusion inhibitor is 1% by mass or less because the cost can be reduced.

(Antioxidant)
The thermally conductive grease according to this embodiment can further contain an antioxidant. The antioxidant mainly prevents oxidation of the base oil contained in the thermally conductive grease, increases the stability of the thermally conductive grease, and enables the thermally conductive grease to be used for a long period of time.

The antioxidant is not particularly limited, and known antioxidants can be used. Examples thereof include hindered amine, hindered phenol, sulfur, phosphorus, benzotriazole, triazine, benzophenone, benzoate, and HALS compounds. Among these, hindered amine-based antioxidants are particularly effective and therefore preferred. These antioxidants may be used alone or in combination of two or more.

The content of the antioxidant is preferably 0.001% by mass or more and 3% by mass or less with respect to 100% by mass of the thermally conductive grease. Further, it is more preferably 0.005% by mass or more and 2% by mass or less, still more preferably 0.01% by mass or more and 1% by mass or less, and most preferably 0.05% by mass or more and 0.5% by mass or less. be.

An antioxidant content of 0.001% by mass or more is preferable because a good antioxidant effect can be obtained and the thermal durability of the thermally conductive grease can be effectively improved. On the other hand, even if the content of the antioxidant exceeds 3% by mass, the properties of the antioxidant do not change significantly. When the content of the antioxidant is 3% by mass or less, the cost can be reduced, which is preferable.

(other ingredients)
The thermally conductive grease according to the present embodiment may contain other components (other components) than the components described above, if necessary. Other components include secondary antioxidants, rust inhibitors, corrosion inhibitors, thickeners, thickeners, and the like.

Secondary antioxidants include sulfur-based antioxidants such as sulfide, disulfide, trisulfide and thiobisphenol, and phosphorus-based antioxidants such as alkyl phosphite and ZnDTP.

Examples of rust preventives include sulfonates, carboxylic acids, carboxylates, succinate esters, and the like. Examples of corrosion inhibitors include compounds such as benzotriazole and derivatives thereof, thiadiazole compounds, and the like. Thickeners may include polybutenes, polymethacrylates, olefin copolymers, high viscosity polyalphaolefins, and the like.

Examples of thickening agents include urea compounds, sodium terephthalamate, polytetrafluoroethylene, organic bentonite, silica gel, petroleum wax, polyethylene wax and the like.

The content of these additives can be about the same as the content used in ordinary thermally conductive greases within a range that does not impair the characteristics of the present invention.
[Properties of grease]
The consistency of the thermally conductive grease according to this embodiment is not particularly limited. It can be selected as appropriate from the viewpoint of the applicability, spreadability, and adhesion of the thermally conductive grease. From the viewpoint of having these properties, the consistency of the thermal conductive grease is preferably 200 or more and 400 or less, more preferably 250 or more and 400 or less, further preferably 300 or more and 400 or less, and 330 or more. 400 or less is particularly preferred.

≪2. Method for producing thermally conductive grease>
The thermally conductive grease according to this embodiment is manufactured by mixing each component. The manufacturing method is not particularly limited as long as the components can be uniformly mixed, and a general grease manufacturing method can be employed.

Specifically, as a production method, a method can be used in which the mixture is kneaded using a planetary mixer, a rotation-revolution mixer, or the like to form a grease, and then uniformly kneaded using a triple roll.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples of the present invention. In addition, the present invention is not limited at all by the following examples.

<<Examples 1 and 2 and Comparative Examples 1 and 2>>
[reagent]
Components used in Examples and Comparative Examples are shown below.
(A) Inorganic powder filler (A-1) Zinc oxide 1 Average particle size: 0.6 μm
(A-2) Zinc oxide 2 Average particle size: 10 μm
The average particle size of each inorganic powder filler was measured by a laser diffraction scattering method using a particle size distribution analyzer (SALD-7000 manufactured by Shimadzu Corporation).
(B) Base oil (B-1) Ester of pentaerythritol and monocarboxylic acid having 8 and 10 carbon atoms 40° C. kinematic viscosity: 32 mm ² /s (ester base oil)
(C) Dispersant (C-1) Higher fatty acid ester (D) Base oil diffusion inhibitor (D-1) Perfluoroalkyl group-containing compound having a hydrogen group (D-2) Perfluoroalkyl group having a phosphate group Containing compound (D-3) Perfluoroalkyl group-containing compound having a sulfone group (D-4) Perfluoroalkyl group-containing compound having a carbonate group (E) Antioxidant (E-1) Hindered amine antioxidant (F ) Additive (F-1) Thickener Organically treated bentonite

[Example 1]
Preparation of the thermally conductive grease according to Example 1 was carried out as follows.
That is, to achieve the contents shown in Table 1, 10% by mass of the base oil (B-1), 1.6% by mass of the antioxidant (E-1), and 0.6% of the dispersant (C-1) were added. 2% by mass, 0.2% by mass of the base oil diffusion inhibitor (D-1) is dissolved, and further, 55% by mass of the inorganic powder filler (A-1) and 30% by mass (A-2), a thickener (F-1) 3% by mass was placed in a planetary mixer. The mixture was kneaded while being heated from room temperature to about 100° C. and thoroughly mixed to form a grease. After that, kneading with a triple roll was performed three times to prepare a thermally conductive grease.

Using the prepared thermally conductive grease, base oil diffusibility was evaluated by the following method.

(Base oil diffusibility evaluation)
The thermally conductive grease was applied on frosted glass in a shape of 6 mm in diameter and 1.5 mm in thickness, left at room temperature for 72 hours, and then evaluated for the amount of diffused base oil. To evaluate the amount of diffusing base oil, as shown in FIG. The average value (A+B)/2 was taken as the diffusion distance (bleed-out amount). The measurement results are shown in Table 1 below (indicated as "diffusion distance" in Table 1; the same shall apply hereinafter). The maximum diffusion distances A and B are the maximum values in the horizontal (X-axis) or vertical (Y-axis) direction of the thermally conductive grease in a bleed-out state after being diffused circularly as shown in FIG. and the distance of each maximum value in the horizontal (X-axis) or vertical (Y-axis) direction in the applied thermally conductive grease before diffusion.

[Example 2]
A thermally conductive grease was prepared in the same manner as in Example 1, except that the base oil diffusion inhibitor was changed to (D-2), and the base oil diffusibility was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

[Comparative Examples 1 and 2]
A thermally conductive grease was prepared in the same manner as in Example 1 except that the base oil diffusion inhibitor was changed to (D-3) (Comparative Example 1) and (D-4) (Comparative Example 2). Base oil diffusibility was evaluated in the same manner as in 1. Table 1 shows the evaluation results.

[Examples 3 to 5]
The amount of the base oil diffusion inhibitor (D-1) was set to 0.1% by mass (Example 3), 0.5% by mass (Example 4), and 1.0% by mass (Example 5), and the base oil diffusion A thermally conductive grease was prepared in the same manner as in Example 1, except that the amount of the base oil (B-1) was adjusted as shown in Table 1 along with the amount of the inhibitor (D-1). Base oil diffusibility was evaluated in the same manner as in 1. Table 1 shows the evaluation results.

[Comparative Example 3]
A thermally conductive grease of Comparative Example 3 was prepared in the same manner as in Example 1 except that no base oil diffusion inhibitor was added, and the base oil diffusibility was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

As can be seen from Table 1, Examples 1 to 5 containing a perfluoroalkyl group-containing compound having a hydrogen group or a phosphoric acid group as a base oil diffusion inhibitor are evaluated for base oil diffusibility. It was confirmed that the diffusion distance of the base oil was shorter and the base oil diffusion property was superior to that of Comparative Example 3, which did not contain the base oil.

On the other hand, Comparative Examples 1 and 2, which contain a perfluoroalkyl group-containing compound having a sulfonic acid group or a carbonate group different from the above base oil diffusion inhibitor, as a base oil diffusion inhibitor, in base oil diffusion evaluation, The diffusion distance is about the same as in Comparative Example 3, which does not contain the oil diffusion inhibitor, and it can be seen that the thermally conductive grease according to the composition of the present invention cannot obtain the base oil diffusion prevention effect.

It has been confirmed that the thermally conductive greases of the examples of this evaluation have the properties required for thermally conductive greases in terms of viscosity, thermal conductivity, etc., in addition to base oil diffusibility. .

The heat-resistant thermally conductive grease of the present invention can improve the anti-diffusion performance of the base oil. Therefore, by applying the thermally conductive grease of the present invention to the contact interface between a heat-generating component such as an electronic component and a heat-radiating component such as a heat sink, the heat-radiating property of the heat-generating component can be improved. It is particularly suitable as a thermally conductive grease used in CPUs and power semiconductors that require high heat dissipation properties.

Claims (3)

A thermally conductive grease containing an inorganic powder filler, a base oil, and a base oil diffusion inhibitor,
The base oil diffusion inhibitor has a perfluoroalkyl group at one end and a hydrogen group or a phosphate group at the other end,
The content of the base oil diffusion inhibitor is a ratio of 0.1% by mass or more and 1% by mass or less with respect to 100% by mass of the thermally conductive grease ,
The base oil diffusion inhibitor is a compound having a structure represented by the following formula (1)
Thermally conductive grease.
R—(C _n H _2n O) _m —X (1)
(In the above formula (1), R is a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms, n is an integer of 1 to 10, and m is 2 to 100 is an integer, and X is a hydrogen group or a phosphate group.) The thermally conductive grease of claim 1 , further comprising an antioxidant. The content of the inorganic powder filler is 70% by mass or more and 97% by mass with respect to 100% by mass of the thermally conductive grease,
The thermally conductive grease according to claim 1 or 2 , wherein the content of the base oil is 2% by mass or more and 29% by mass or less with respect to 100% by mass of the thermally conductive grease.

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