JP5944306B2 - High thermal conductive grease - Google Patents

Description

  The present invention relates to a high thermal conductivity grease having an extremely high thermal conductivity, and relates to a high thermal conductivity grease excellent in coating property and thermal stability in a high temperature environment.

  Among semiconductor components used in electronic devices, there are components 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 components from heat and to function normally, there is a method of conducting the generated heat to a heat radiating component such as a heat sink to radiate heat. The thermally conductive grease is applied between the semiconductor component and the heat radiating component so that the semiconductor component and the heat radiating component are 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, electronic devices using these semiconductor components have been improved in performance, and have been made smaller and more densely mounted. Thermally conductive greases used for heat dissipation measures are required to have higher thermal conductivity and good coating properties. Therefore, it is also required to have a high consistency.

Thermally conductive greases are based on liquid hydrocarbons, base oils such as silicone oil and fluorine oil, metal oxides such as zinc oxide and aluminum oxide, inorganic nitrides such as boron nitride, silicon nitride and aluminum nitride, aluminum and A grease-like composition in which a filler having a high thermal conductivity such as a metal powder such as copper is dispersed in a large amount. For example, what mix | blended a specific surface modifier (refer patent document 1, 2 grade | etc.,) Etc. are disclosed.

Japanese Patent No. 4642085 JP 2008-280516 A

Thermally conductive grease is used at a thermal contact interface in a cooling device such as a CPU of a computer or a cooling device such as a power semiconductor used in a high-power inverter. In recent years, the heat generation density and the heat generation amount of semiconductor elements in these electronic devices have increased with the miniaturization and performance enhancement, and the heat conductive grease is required to have higher heat conductivity. In general, the thermal conductivity of the heat conductive grease increases as the amount of the filler increases, but if the amount of the filler is too large, the consistency decreases and sufficient coatability cannot be obtained. In this case, there is a possibility that the thermal conductivity is lowered due to an increase in the film thickness of the coating film or mixing of bubbles.

Therefore, there is a demand for a technique that can increase the amount of filler while maintaining a high consistency and good coatability. Furthermore, since these high thermal conductive greases are directly applied to heat-generating parts and used, depending on the type of thermal conductive grease, depending on the type of thermal conductive grease, oil evaporation, bleed, pump out, etc. Heat dissipation performance may be reduced.
Therefore, in the case of being used for a long period of time in an environment with a large calorific value, the thermal conductive grease is required to have higher thermal conductivity and excellent thermal stability at high temperatures.
An object of the present invention is to provide a highly thermally conductive grease having high thermal conductivity, high consistency, good coating properties, and excellent thermal stability at high temperatures.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have used a specific surface modifier for improving the dispersibility of the inorganic powder filler, thereby highly filling the inorganic powder filler. It has been found that a high consistency can be obtained and the thermal stability can be improved, and the present invention has been completed.

That is, the present invention provides (A) an inorganic powder filler in an amount of 85 to 97% by mass, (B) a base oil in an amount of 2 to 15% by mass, and (C) a polycarboxylic acid compound represented by the general formula (1). 0.001 to 3 mass%,

(In the general formula (1), R ₁ and R ₂ are each a divalent hydrocarbon group having a straight chain or branched chain having 1 to 36 carbon atoms, n is 1 to 15, and X and Y are respectively And at least one substituent selected from the group consisting of a carboxyl group and a hydroxyl group, or a hydrogen atom, and at least one of X and Y is a carboxyl group or a hydroxyl group. In the formula (1), (—R ₂ —COO—) _n is a co-polymer composed of two or more structural units (—R ₂ —COO—), each of which is a divalent hydrocarbon group in which R ₂ is different. It may be a combined group.)

(D) 0.001 to 3% by mass of the compound represented by the general formula (2),
_{RO- (CH 2 CH (OH)} CH 2 O) n-H (2)
(In the general formula (2), R represents a hydrocarbon group having 8 or more carbon atoms, and is an alkyl group, alkenyl group or aryl group having 8 or more carbon atoms, n represents the degree of polymerization of glycerin, Number.)
(E) An unsaturated fatty acid is contained in an amount of 0.001 to 3% by mass, and (F) an antioxidant is contained in an amount of 0.001 to 3% by mass. .

The present invention also provides a high thermal conductive grease, wherein the inorganic filler is at least one selected from zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride and silicon carbide. is there.
The present invention also provides a high thermal conductivity grease in which the base oil is at least one selected from mineral oil, synthetic hydrocarbon oil, diester, polyol ester and phenyl ether. .

The high thermal conductivity grease of the present invention increases the filling amount of the inorganic filler due to the effect of the specific surface modifier, can realize higher thermal conductivity without impairing the coating property, and improves the thermal stability. Can do. By using the thermally conductive grease of the present invention, the heat dissipation of electronic parts that emit high heat can be improved, and it is particularly suitable as a heat dissipation material for power semiconductors and LEDs.

(1) Inorganic powder filler The inorganic powder filler of component (A) used in the present invention is not particularly limited as long as it has a higher thermal conductivity than the base oil, but metal oxide, inorganic nitride, metal Powders such as silicon compounds and carbon materials are preferably used. One kind of the inorganic powder filler of the present invention may be used, or two or more kinds may be used in combination.

  In the case where the above-mentioned inorganic powder filler is required for electrical insulation, non-conductive substances such as semiconductors and ceramics, such as zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride, boron nitride, silicon carbide, silica, diamond, etc. Are preferably used, more preferably zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride, boron nitride, silicon carbide, and silica powder, and particularly preferably zinc oxide, aluminum oxide, and aluminum nitride powder. These inorganic powder fillers may be used alone or in combination of two or more. In addition, metal powders such as metallic aluminum, metallic silver, and metallic copper, and carbon material powders such as graphite, fullerene, and carbon nanotubes can be suitably used when seeking higher thermal conductivity without requiring electrical insulation. Metal powder is more preferable, and metal aluminum powder is particularly preferable. Further, a metal powder or a carbon material powder can be used in combination with the above-mentioned non-conductive substance powder.

The inorganic powder filler is preferably an inorganic powder having an average particle size of 0.15 to 3 μm when only fine particles are used. By setting the average particle diameter to 0.15 μm or more, the ratio of the liquid components (base oil and surface modifier) to the surface area of the inorganic powder filler is good, and a higher consistency can be obtained. On the other hand, when the average particle size is 3 μm or less, it becomes easy to perform close packing, higher thermal conductivity can be achieved, and oil separation is difficult. Moreover, when combining a fine grain and a coarse grain, said fine grain and a coarse inorganic powder with an average particle diameter of 5-50 micrometers can be combined. In this case, by setting the average particle size of the coarse particles to 50 μm or less, the coating film can be thinned and the heat dissipation performance during mounting can be further enhanced. On the other hand, when the average particle size of the coarse particles is 5 μm or more, higher thermal conductivity can be easily obtained.

When the inorganic powder filler is a combination of fine particles and coarse particles, the coarse particles can be a combination of two or more kinds of powders having different average particle sizes. Also in this case, it is preferable that the average particle diameter of each coarse grain is 5-50 micrometers from a viewpoint of heat conductivity and the thermal radiation performance at the time of mounting.

Moreover, it is preferable to mix in the range of 20: 80-85: 15 mass ratio in the case of combining a fine grain and coarse grain inorganic powder filler. When two or more kinds of coarse particles are combined, the mass ratio between the coarse particles is not particularly limited. In this case, the mass ratio of the fine particles is preferably in the range of 20% to 85% of the inorganic powder filler. . By setting the mixing ratio of fine particles and coarse particles in the above range, a high consistency can be obtained from the balance between the surface area of the inorganic powder filler and the amount of liquid components (base oil and surface modifier). In addition, the balance between coarse and fine particles is suitable for closest packing, and oil separation is difficult.

  Although the content rate of an inorganic powder filler is 85-97 mass%, it is excellent in thermal conductivity, so that the content rate is high, Preferably it is 90-96 mass%. If it is less than 85% by mass, the thermal conductivity may be lowered, or oil separation may occur and the base oil may ooze out. On the other hand, if it exceeds 97% by mass, the consistency will be low and sufficient coatability will not be maintained, or a heat conductive grease will not be prepared.

(2) Base oil As the base oil of component (B), various base oils can be used, for example, hydrocarbon base oils such as mineral oil and synthetic hydrocarbon oil, ester base oils, ether base oils, phosphorus Examples include acid esters, silicone oils and fluorine oils. In terms of preventing separation of base oils, hydrocarbon base oils, ester base oils, polyether groups are lower than silicone oils and fluorine oils having a low surface tension. Oil is preferred. A base oil may be used individually by 1 type, or may be used in combination of 2 or more type.
As mineral oil, for example, a mineral oil-based lubricating oil fraction is refined by appropriately combining purification methods such as solvent extraction, solvent dewaxing, hydrorefining, hydrocracking, wax isomerization, 150 neutral oil, 500 neutral Oil, bright stock, and high viscosity index base oil. The mineral 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 using ethylene, propylene, butene, and derivatives thereof as a raw material alone or in combination of two or more. As an alpha olefin, a C6-C14 thing is mentioned preferably.
Specific examples include polyalphaolefin (PAO) which is an oligomer of 1-decene, polybutene which is an oligomer of 1-butene and isobutylene, and a co-oligomer of ethylene and alphaolefin. Moreover, alkylbenzene, alkylnaphthalene, etc. can also be used.
Examples of ester base oils include diesters and polyol esters.

Examples of the diester 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 to 36 carbon atoms is preferable. 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 neopentyl polyol in which a hydrogen atom does not exist on the β-position carbon, and specifically includes carboxylic acid esters such as neopentyl glycol, trimethylolpropane, and pentaerythritol. The carboxylic acid residue constituting the ester part is preferably a monocarboxylic acid residue having 4 to 26 carbon atoms.
In addition to the above, aliphatic dihydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, 2-butyl-2-ethylpropanediol, and 2,4-diethyl-pentanediol, and linear or branched chain saturation Esters with fatty acids can also be used. As the linear or branched saturated fatty acid, a monovalent linear or branched saturated fatty acid having 4 to 30 carbon atoms is preferable.

Examples of the ether base oil include polyglycol and phenyl ether.
Examples of the polyglycol include polyethylene glycol, polypropylene glycol, and derivatives thereof.
Examples of the phenyl ether include alkylated diphenyl ether and (alkylated) polyphenyl ether.

  Examples of phosphate esters include triethyl phosphate, tributyl phosphate, triphenyl phosphate, tricresyl phosphate, and trixylenyl phosphate.

  Since the heat conductive grease is applied to the heat generating portion, it is exposed to a high temperature for a long time. For this reason, it is desirable that the base oil has excellent thermal oxidation stability. Among the above base oils, synthetic base oils are preferable, and synthetic hydrocarbon oils, ester base oils, and ether base oils are preferable. Among these base oils, those that are particularly excellent in thermal oxidation stability include poly α olefins for synthetic hydrocarbon oils, polyol esters for ester base oils, and phenyl ethers for ether base oils as preferred base oils. . Further, among these base oils, polyα-olefins having a high viscosity index and polyol esters having high solubility of additives are used as particularly preferred base oils.

The kinematic viscosity of the base oil is preferably 10mm ² / s~600mm ² / s at 40 ° C.. It is preferable to set the kinematic viscosity at 40 ° C. to 10 mm ² / s or more because evaporation of base oil and oil separation at high temperatures tend to be suppressed. Moreover, since it becomes easy to obtain a high consistency by making dynamic viscosity in 40 degreeC 600 mm < ² > / s or less, it is preferable.
The content of the base oil is 2 to 15% by mass, preferably 2.5 to 12% by mass, and particularly preferably 3 to 10% by mass. When the content exceeds 15% by mass, the consistency becomes too high, and the thermally conductive grease may flow out. In addition, oil separation may occur and thermal conductivity may decrease.

(3) Additive The polycarboxylic acid compound of component (C) used in the present invention is a compound represented by the general formula (1), adsorbs on the surface of the inorganic powder filler, and has an affinity with the base oil. It simultaneously functions as a surface modifier that improves the viscosity and as a dispersant that prevents aggregation of fillers due to steric hindrance.

In the general formula (1), R ₁ and R ₂ are each a divalent hydrocarbon group having a straight chain or branched chain having 1 to 36 carbon atoms, and may be the same or different. Examples of the divalent hydrocarbon group include an alkylene group, an alkenylene group, and an arylene group, and an alkylene group is preferable. Moreover, carbon number of a bivalent hydrocarbon group is 1-36, 2-32 are preferable and 8-30 are more preferable. In addition, the divalent hydrocarbon group preferably has a branch, and more preferably has one branch point. If the total number of carbon atoms in the divalent hydrocarbon group is more than 36, the viscosity becomes too high, and a thermally conductive grease may not be prepared or may become hard.

Moreover, n is 1-15, but when n is 2-15, the part of (—R ₂ —COO—) _{n in} the general formula (1) is a divalent hydrocarbon group in which R ₂ is different. It may be a copolymer group composed of two or more structural units (—R ₂ —COO—). The copolymer group may have a random structure or a block structure.
Further, the weight average molecular weight of the (C) component polycarboxylic acid compound is preferably about 400 to 10,000.
In General formula (1), n is 1-15, and 2-10 are more preferable. When n is more than 15, the viscosity becomes too high, and a thermally conductive grease may not be prepared or may become hard.

In the general formula (1), X and Y are each at least one substituent selected from the group consisting of a carboxyl group and a hydroxyl group, or a hydrogen atom, and at least one of X and Y is a carboxyl group or a hydroxyl group. is there. The combination of X and Y is preferably a combination of a carboxyl group and a hydroxyl group. A combination in which X is a carboxyl group and Y is a hydroxyl group is most preferable.

The polycarboxylic acid compound as component (C) can be obtained, for example, by polymerizing a hydroxycarboxylic acid having 2 to 37 carbon atoms. Such a hydroxycarboxylic acid is not particularly limited as long as the structure described in the general formula (1) is obtained. For example, 3-hydroxylauric acid, 3-hydroxypaltimic acid, 3-hydroxystearic acid 3-hydroxyarachidic acid, 8-hydroxypaltimic acid, 12-hydroxystearic acid, 12-hydroxylauric acid, 12-hydroxypalmitoleic acid, 12-hydroxyoleic acid, 16-hydroxypaltimic acid and the like. In addition, when Y is a carboxyl group, a dicarboxylic acid having 2 to 36 carbon atoms is used, and when X is a hydroxyl group, a divalent alcohol having 1 to 36 carbon atoms is bonded to the hydroxycarboxylic acid polymer by an ester bond. Can be obtained.

(C) It is preferable to contain 0.001-3 mass% of polycarboxylic acid compounds of a component. More preferably, it is 0.005-2 mass%, More preferably, it is 0.01-1 mass%, Most preferably, it is 0.05-0.5 mass%. When the content is less than 0.001% by mass, not only high consistency and good thermal stability can be obtained, but also the filling rate cannot be increased and high thermal conductivity cannot be obtained. On the other hand, even if the content is more than 3% by mass, an improvement in the effect cannot be expected.

The polyglycerin monoalkyl ether compound (D) used in the present invention is a compound represented by the general formula (2), and is adsorbed on the surface of the inorganic powder filler to improve the affinity with the base oil. It functions simultaneously as a quality agent and as a dispersant that prevents aggregation of fillers due to steric hindrance.
In the general formula (2), R represents a hydrocarbon group having 8 or more carbon atoms, and examples thereof include an alkyl group, alkenyl group, and aryl group having 8 or more carbon atoms. preferable. 8-30 are preferable, as for carbon number of R, 10-26 are more preferable, and 12-22 are especially preferable. Moreover, in General formula (2), n represents the polymerization degree of glycerol, is a 1 or more positive number, Preferably it is a 1-5 positive number. If n exceeds 5, the solubility in the base oil will deteriorate.
In addition, although the polymerization degree n in each molecule | numerator is an integer, in the case of the aggregate | assembly of 2 or more types of molecules from which the polymerization degree n differs, n is an average value.

The polyglycerin monoalkyl ether compound (D) used in the present invention is preferably contained in an amount of 0.001 to 3% by mass. More preferably, it is 0.005-2 mass%, More preferably, it is 0.01-1 mass%, Most preferably, it is 0.05-0.5 mass%. When the content is less than 0.001% by mass, not only high consistency and good thermal stability can be obtained, but also the filling rate cannot be increased and high thermal conductivity cannot be obtained. On the other hand, even if the content is more than 3% by mass, an improvement in the effect cannot be expected.

In this invention, the moisture resistance of heat conductive grease can be improved by mix | blending the unsaturated fatty acid of (E) component further. When an unsaturated fatty acid is blended, it is possible to prevent a change in consistency and curing when placed in a high humidity environment, and it is possible to prevent a decrease in heat dissipation performance.
As a kind of unsaturated fatty acid, C8-C30 is preferable, C12-C26 is especially preferable, and C16-C24 is the most preferable. By setting the carbon number within this range, a high consistency can be obtained. The unsaturated fatty acid is preferably one in which the unsaturated group is a carbon-carbon double bond. The number of carbon-carbon double bonds is more preferably 1 or 2 and particularly preferably 1. Those with more than two carbon-carbon double bonds can reduce thermal stability. The unsaturated fatty acid is preferably a monovalent or divalent unsaturated fatty acid with respect to the carboxyl group, more preferably a monovalent unsaturated fatty acid, and the hydrocarbon group with a linear or branched chain having 8 or more carbon atoms. Saturated fatty acids are preferred.

Specific examples of the unsaturated fatty acid include, for example, caproleic acid, undecylenic acid, Linderic acid, tuzuic acid, myristoleic acid, palmitoleic acid, zomarinic acid, peteroceric acid, oleic acid, elaidic acid, pasenic acid, codoic acid, gondoin Examples thereof include acid, cetreic acid, erucic acid, brassic acid, and ceracoleic acid.
These unsaturated fatty acids may be used alone or in combination of two or more. It is preferable to contain 0.001-3 mass% of unsaturated fatty acid used for this invention. More preferably, it is 0.005-2 mass%, More preferably, it is 0.01-1 mass%, Most preferably, it is 0.05-0.5 mass%. By making the content 0.001% by mass or more, it is possible to more effectively suppress the change in consistency in a high-humidity environment. Cannot be expected.

 The (C) component polycarboxylic acid compound, the (D) component polyglycerin monoalkyl ether compound, and the (E) component unsaturated fatty acid can be used alone, but they can be used alone. By using it, the highest consistency is obtained. When combining 3 types, the mass ratio between the additives is not particularly limited, but each weight ratio of (C) :( D), (D) :( E), (C) :( E) is 10: It is preferable to mix in the range of 80-80: 10, and more preferably in the range of 30: 70-70: 30. By making the compounding ratio of the additives within the above range, the surface active effect of each additive is promoted, and a high consistency can be obtained.

Moreover, it is preferable to contain 0.05-3 mass% of 3 types of total amounts with respect to the weight of an inorganic powder filler. More preferably, it is 0.1-2 mass%, More preferably, it is 0.15-1 mass%, Most preferably, it is 0.2-0.5 mass%. By making the content 0.05 mass% or more with respect to the weight of the inorganic powder filler, it can be greased with a high consistency, and even if it exceeds 3.0 mass%, the further improvement in consistency is achieved. I can't expect it.

A known antioxidant can be appropriately blended with the antioxidant of the component (F) used in the present invention. Examples of the antioxidant include compounds such as hindered amine, hindered phenol, sulfur, phosphorus, benzotriazole, triazine, benzophenone, benzoate, and HALS. A hindered amine-based antioxidant is preferable because it is particularly effective. These may be used alone or in combination.
The total amount of the antioxidant is preferably 0.001 to 3% by mass. More preferably, it is 0.005-2 mass%, More preferably, it is 0.01-1 mass%, Most preferably, it is 0.05-0.5 mass%. When content is less than 0.001 mass%, a favorable antioxidant effect is not acquired and thermal durability falls. On the other hand, even if the content is more than 3% by mass, an improvement in the effect cannot be expected.

(4) Other additives As other additives, compounds such as sulfonate, carboxylic acid and carboxylate are used as rust inhibitors, compounds such as benzotriazole and its derivatives are used as corrosion inhibitors, and thiadiazole compounds However, examples of the thickener / thickener include polybutene, polymethacrylate, fatty acid salt, urea compound, petroleum wax, polyethylene wax and the like. The amount of these additives may be a normal amount.

(5) Manufacturing Method Regarding the manufacturing of the high thermal conductivity grease of the present invention, the method is not limited as long as the components can be mixed uniformly. As a general manufacturing method, there is a method of kneading with a mortar, a planetary mixer, a twin screw extruder, a rotation and revolution mixer, etc., making it grease, and then kneading uniformly with three rolls. .

(6) Property of grease The high thermal conductive grease of the present invention can be used if it has a consistency of 200 or more, but it is 250 to 400 from the viewpoints of coating property, spreading property, adhesion property, oil separation prevention property and the like. It is preferable that it is 300-400, and it is especially preferable that it is 330-400.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by this.
It shows below about each component used for the Example and the comparative example.
(1) (A) Inorganic powder filler zinc oxide 1: average particle size 0.6 μm
Zinc oxide 2: Average particle size 11 μm
(2) (B) Base oil PAO: poly-α-olefin (1-decene-oligomer), 40 ° C. kinematic viscosity of 47 mm ² / s.
POE: ester of pentaerythritol and monocarboxylic acid having 8 and 10 carbon atoms, 40 ° C. kinematic viscosity of 32 mm ² / s.
Dialkylated diphenyl ether: (having an alkyl group having a branched chain having 12 to 14 carbon atoms), having a kinematic viscosity at 40 ° C. of 98 mm ² / s.
Dialkylated tetraphenyl ether: (having an alkyl group having a branched chain having 12 to 14 carbon atoms), having a kinematic viscosity at 40 ° C. of 410 mm ² / s.

(3) Additive (a) (C) Polycarboxylic acid compound 12-Hydroxystearic acid oligomer obtained by polymerizing 3 to 5 molecules
(In General Formula (1), R ₁ and R ₂ are both alkylene groups having 17 carbon atoms, n is 2 to 4, X is a carboxyl group, and Y is a hydroxyl group. Weight average molecular weight Mw (in terms of GPC polystyrene) ) Is approximately 2400.)
(I) (D) Polyglycerol monoalkyl ether compound (Poly) glyceryl ether (Monoglycerol monooleyl ether contains a small amount of polyglycerol monooleyl ether. In general formula (2), n = 3.)
(C) (E) Unsaturated fatty acid erucic acid (unsaturated fatty acid having 22 carbon atoms)
(D) (F) Antioxidant amine antioxidant (dialkylated diphenylamine)

(Examples 1-7)
Table 1 below shows the compositions of Examples 1 to 7 and the performance and properties of the thermally conductive grease. The heat conductive grease was prepared by the following method by blending the components having the composition shown in Table 1. In Table 1, the unit of the numerical value of the composition is mass%, and the numerical value in parentheses of the inorganic powder filler is the average particle diameter.
Preparation of thermally conductive grease Various additives such as surface modifiers and antioxidants were dissolved in the base oil and placed in a planetary mixer or an automatic mortar together with an inorganic powder filler. The mixture was kneaded at room temperature to 60 ° C. for 30 minutes and mixed well to obtain a grease. Thereafter, kneading with three rolls was carried out 1 to 3 times to prepare a heat conductive grease.

The performance shown below was evaluated using the obtained heat conductive grease. For the penetration, the immiscibility penetration was measured according to JIS-K2220. The greater the consistency value, the softer the heat conductive grease, and vice versa. The thermal conductivity was measured at room temperature using a rapid thermal conductivity meter QTM-500 manufactured by Kyoto Electronics Industry Co., Ltd. In the high-temperature standing test, 0.25 ml of heat conductive grease is sandwiched between iron plates, thinned to a thickness of 200 μm, heated at 150 ° C. for 500 hours, a predetermined weight is applied, and the diameter of the area from the center is measured. Thus, the consistency before and after the test was simply measured. In the constant temperature and humidity test, a heat conductive grease was allowed to stand for 72 hours in an environment of a temperature of 60 degrees and a relative humidity of 90%, and the immiscible penetration before and after the test was measured.

The results of the high temperature storage test and the constant temperature and humidity test described in each table are indicated by the consistency change rate and the immiscible consistency change rate, respectively, and when the consistency decreases or becomes hard, the change rate is indicated. When the consistency increased, that is, when the consistency became soft, the rate of change was indicated by a positive value.
The consistency change rate after 500 hours of the high temperature standing test is preferably within ± 50%, more preferably within ± 44%, and particularly preferably within ± 40%.

(Comparative Examples 1-7)
Table 2 below shows the compositions of Comparative Examples 1 to 7 and the performance and properties of the thermally conductive grease. Ingredients having the composition shown in Table 2 were blended to prepare a heat conductive grease in the same manner as in the examples.

As can be seen from Table 1, Examples 1 to 7 containing (C) a polycarboxylic acid compound, (D) a polyglycerin monoalkyl ether compound, and (E) an unsaturated fatty acid have 4.5 W / m · K or more. It can be seen that while having high thermal conductivity, the consistency is high and the coating property is excellent. In addition, it can be seen that there is little change in the consistency after the high temperature standing test and after the constant temperature and humidity test, and it has both good thermal stability and good moisture resistance.
On the other hand, Comparative Examples 1 to 3 including one of (C) a polycarboxylic acid compound, (D) a polyglycerin monoalkyl ether compound and (E) an unsaturated fatty acid dispersant have good thermal conductivity. However, the consistency is low and the coating property is not excellent. Moreover, it can be seen that the consistency change after the high-temperature standing test is large and the thermal stability is poor.
In addition, Comparative Examples 4 to 7 including two types of dispersants of the compound (C), the compound (D), and the unsaturated fatty acid (E) have good thermal conductivity and consistency, but have a high temperature. It can be seen that the penetration after the standing test is low and the thermal stability is poor.

The high thermal conductive grease of the present invention can improve the heat dissipation of electronic components that require heat countermeasures, and is particularly suitable as a heat dissipation material for CPUs and power semiconductors.

Claims (3)

(A) 85 to 97% by mass of the inorganic powder filler, (B) 2 to 15% by mass of the base oil, and (C) 0.001 to 3% by mass of the polycarboxylic acid compound represented by the general formula (1). (D) 0.001 to 3% by mass of a polyglycerin monoalkyl ether compound represented by the general formula (2), (E) 0.001 to 3% by mass of an unsaturated fatty acid, and (F) an antioxidant. A highly thermally conductive grease characterized by containing 0.001 to 3% by mass.

(In the general formula (1), R ₁ and R ₂ are each a divalent hydrocarbon group having a straight chain or branched chain having 1 to 36 carbon atoms, n is 1 to 15, and X and Y are respectively And at least one substituent selected from the group consisting of a carboxyl group and a hydroxyl group, or a hydrogen atom, and at least one of X and Y is a carboxyl group or a hydroxyl group. In the formula (1), (—R ₂ —COO—) _n is a co-polymer composed of two or more structural units (—R ₂ —COO—), each of which is a divalent hydrocarbon group in which R ₂ is different. It may be a combined group.)
_{RO- (CH 2 CH (OH)} CH 2 O) n-H (2)
(In the general formula (2), R represents a hydrocarbon group having 8 or more carbon atoms, and is an alkyl group, alkenyl group or aryl group having 8 or more carbon atoms, n represents the degree of polymerization of glycerin, Number.)   The high thermal conductive grease according to claim 1, wherein the inorganic filler is at least one selected from zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride, and silicon carbide. The high thermal conductive grease according to claim 1 or 2, wherein the base oil is at least one selected from mineral oil, synthetic hydrocarbon oil, diester, polyol ester and phenyl ether.