JP5781407B2 - Thermally conductive compound - Google Patents

Description

  The present invention relates to a thermally conductive compound having excellent bleed resistance.

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, Peltier elements, LEDs, and inverters.
In order to protect these semiconductor components from heat and to function normally, there is a method of conducting the generated heat to heat dissipation components such as a heat spreader and a heat sink to dissipate heat. The thermally conductive compound 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 heat of the semiconductor component to the heat radiating component.

Thermally conductive compounds include 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 It is a compound composition in which a filler having a high thermal conductivity such as a metal powder such as copper is dispersed in a large amount. The base oil component is necessary to make the filler, which is a powder, into a compound form, but the so-called bleed that causes the liquid component to bleed out after application or use of the heat conductive compound occurs, and the compound form is retained. There is a possibility that it becomes difficult, or that the separated liquid component contaminates the inside of the electronic device.
In order to solve these problems, attempts have been made to add a specific thixotropic agent (see Patent Document 1) or use a specific polyorganosiloxane (see Patent Document 2).

WO2006 / 132253 JP2008-31336

  An object of the present invention is to provide a thermally conductive compound having excellent bleed resistance.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that bleed resistance can be improved by using a specific metal soap, and have completed the present invention.

That is, the present invention provides (A) 75 to 97% by mass of an inorganic powder filler, (B) 2 to 24% by mass of a non-silicone base oil, and (C) an aluminum soap having a total carbon number of 12 to 34. .15 to 2.5% by mass, (D) 0.05 to 1.5% by mass of (poly) glyceryl ether, and the ratio of component (C) to the content of the liquid component is 1 to 10% by mass The present invention provides a thermally conductive compound characterized by the following.
The present invention also provides a heat conductive compound characterized in that, in the above heat conductive compound, (E) 0.05 to 1% by mass of an unsaturated fatty acid having 10 to 19 carbon atoms is contained. is there.

  The heat conductive compound of the present invention is excellent in bleed resistance. Therefore, the thermally conductive compound of the present invention is extremely useful in practice.

Thermally conductive compound of the present invention, (A) an inorganic powder filler, (B) a non-silicone-based base oil, (C) an aluminum soap is the total carbon number of 12-34, a (D) (poly) glyceryl ether, Contains at a predetermined ratio.

(A) 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.

  When the above-mentioned inorganic powder fillers require electrical insulation, powders of non-conductive substances such as semiconductors and ceramics such as zinc oxide, aluminum oxide, boron nitride, silicon carbide, silica, and diamond are preferably used. Zinc oxide, aluminum oxide, boron nitride, and silica powder are more preferable, and zinc oxide and aluminum oxide powder are particularly preferable. These inorganic powder fillers may be used alone or in combination of two or more. In addition, when seeking higher thermal conductivity without requiring electrical insulation, metal powders such as metallic aluminum and metallic copper, and carbon material powders such as graphite and carbon nanotubes can be suitably used. Preferably, 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 size to 0.15 μm or more, the balance of the ratio of the liquid component 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. Further, as the fine particles, two or more kinds of inorganic powders having different average particle sizes may be combined.

When higher thermal conductivity is required than when only fine particles are used, fine particles and coarse particles may be combined. However, when only fine grains are used, the thermal conductivity is slightly lower than when fine grains and coarse grains are combined, but it is easy to make a thin film due to high consistency, thus further improving the heat dissipation performance during mounting. There is an advantage that can be.
When combining fine grains and coarse grains, the fine grains and coarse inorganic powders having an average particle diameter of 5 to 50 μm 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 inorganic powders having different average particle diameters. 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.
In the present invention, the average particle size of the inorganic powder filler can be calculated as a volume average particle size distribution measured by a laser diffraction scattering method (based on JIS R 1629).

  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. . A high consistency can be obtained from the balance between the surface area of the inorganic powder filler and the amount of the liquid component by adjusting the mixing ratio of the fine particles and the coarse particles in the above range. In addition, the balance between coarse and fine particles is suitable for closest packing, and oil separation is difficult.

  (A) Content of a component is 75-97 mass% with respect to the whole quantity of a heat conductive compound, but it is excellent in heat conductivity, so that content is high. (A) Content of a component is 75-97 mass%, Preferably it is 78-95 mass%. In the case of only fine particles, the preferred content of component (A) is 75 to 95% by mass, more preferably 78 to 90% by mass. When fine particles and coarse particles are combined, component (A) The preferable content of is 80 to 97 mass%, more preferably 85 to 95 mass%. If it is less than 75% by mass, the thermal conductivity may be lowered, or oil separation may occur and the liquid component may ooze out. On the other hand, if the content of the component (A) exceeds 97% by mass, the consistency becomes low and sufficient coatability cannot be maintained, or a heat conductive compound cannot be prepared.

(B) Base oil As the non-silicone base oil of component (B) used in the present invention, various base oils can be used. For example, hydrocarbon base oils such as mineral oils and synthetic hydrocarbon oils, ester bases Oil, ether base oil, phosphate ester and the like, hydrocarbon base oil, ester base oil and ether base oil are preferable, and synthetic hydrocarbon oil, ester base oil and ether base oil are preferable. . By using a base oil other than the silicone base oil having a low surface tension, the separation of the base oil can be reduced. 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 compound is applied to the heat generating part, it is exposed to 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 polyalphaolefins in synthetic hydrocarbon oils, polyol esters in ester base oils, and phenyl ethers in ether base oils as preferred base oils. . Further, among these base oils, when a polyalphaolefin and a polyol ester are used in combination, the aluminum soap as the component (C) tends to be dissolved, and the bleed amount tends to be reduced.
Further, the consistency tends to be high, and there is a tendency that sufficient coating properties can be maintained.
5-60 mass% is preferable, as for the ratio of the polyol ester in base oil, 10-50 mass% is more preferable, and 20-40 mass% is further more preferable.

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.

  (B) Content of a component is 2-24 mass% with respect to the whole quantity of a heat conductive compound, 3-22 mass% is preferable and 4-19 mass% is more preferable. By setting the content of the component (B) to 2% by mass or more, the consistency tends to be high, and sufficient applicability tends to be maintained. Moreover, it exists in the tendency which becomes easy to prepare a heat conductive compound. It is preferable that the content of the component (B) is 24% by mass or less because the consistency does not become too high, and the thermal conductive compound tends to flow out and the decrease in thermal conductivity due to oil separation can be suppressed. .

(C) Aluminum soap The aluminum soap of the (C) component used for this invention consists of metallic aluminum and a fatty acid.
The fatty acid moiety may be linear or branched, and may be saturated or unsaturated. The carbon number of the fatty acid is not particularly limited, but is preferably 6 to 25, more preferably 7 to 23, still more preferably 7 to 20, and most preferably 7 to 13.

The total number of carbon atoms of the fatty acid contained in the component (C) is 12 to 34, more preferably 12 to 30, further preferably 12 to 25, and particularly preferably 12 to 20, Most preferably, it is 12-17.
By making the total number of carbon atoms of the fatty acid contained in the component (C) 12 or more, the aluminum soap is easily dissolved in the base oil component. (C) By making the total number of carbon atoms of the fatty acid contained in the component 34 or less, the size of the network structure constructed by the aluminum soap is set to an appropriate size compared to the liquid component to be retained, and the liquid component is Presumed to be easier to hold.

  Examples of fatty acids include saturated fatty acids such as caproic acid, 2-ethylhexanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, and the like. Examples include palmitoleic acid, oleic acid, eicosenoic acid, eicosadienoic acid, arachidonic acid, erucic acid, brassic acid, and nervonic acid, preferably 2-ethylhexanoic acid and stearic acid.

Examples of the aluminum soap include mono (fatty acid) aluminum soap, di (fatty acid) aluminum soap, and tri (fatty acid) aluminum soap, and di (fatty acid) aluminum soap is preferable. In addition, in the case of di (fatty acid) aluminum soap and tri (fatty acid) aluminum soap, an aluminum soap composed of one or more fatty acids may be used, or an aluminum soap composed of two or more fatty acids may be used.
Preferable examples of the aluminum soap include di (2-ethylhexanoic acid) aluminum and mono (stearic acid) aluminum.

  (C) Content of component is 0.15-2.5 mass% with respect to the whole quantity of a heat conductive compound, Preferably it is 0.2-2.0 mass%, More preferably, it is 0.5. It is -2.0 mass%. When the content of the component (C) is 0.15% by mass or more, the aluminum soap forms a network structure, the liquid component is easily held, and the bleed resistance tends to be easily obtained. When the content of the component (C) is 2.5% by mass or less, a high consistency is likely to be obtained.

  Moreover, the ratio of (C) component with respect to content of a liquid component is 1-10 mass%, Preferably it is 1.5-9 mass%, More preferably, it is 2-8.5 mass%, Preferably it is 2.5-7 mass%. In addition, the liquid component here has shown the sum total of the component except the (A) inorganic powder filler among the components which comprise in the composition. When the ratio of the component (C) with respect to the content of the liquid component is 1% by mass or more, bleeding resistance tends to be easily obtained. This is presumed to be because the aluminum soap forms a network structure and easily retains the liquid component. When the ratio of the component (C) to the content of the liquid component is 10% by mass or less, high consistency tends to be easily obtained.

  In addition, as a method of adding the component (C), there are a method of adding and dissolving the base oil component first, a method of kneading the base oil component and the inorganic powder filler, and adding them to a compounded state, etc. Can be mentioned. (C) The temperature of the stage which adds and knead | mixes a component is 20-150 degreeC, Preferably it is 20-140 degreeC, More preferably, it is 20-100 degreeC, Most preferably, it is 40-100 degreeC. . Bleed resistance may be improved by heating. The step of adding and kneading the component (C) includes the step of kneading the base oil component in which the component (C) is dissolved and the inorganic powder filler, or the step of adding and kneading the component (C). Represent.

(D-1) (Poly) glyceryl ether The (D) component (poly) glyceryl ether used in the present invention is a compound represented by the general formula (1).

(In the formula, R represents a hydrocarbon group having 8 or more carbon atoms, and m is a coefficient representing the degree of polymerization of glycerin and is a number of 1 or more.)
In the general formula (1), R is 8 carbon atoms.
The above hydrocarbon groups are represented, and examples thereof include an alkyl group having 8 or more carbon atoms, an alkenyl group, and an aryl group, and an alkyl group and alkenyl group having 8 or more carbon atoms are preferable. 8-30 are preferable, as for carbon number of R, 10-26 are more preferable, and 12-22 are more preferable. Moreover, in General formula (1), m is a coefficient showing the polymerization degree of glycerol, Comprising: It is a number of 1 or more, Preferably it is a number of 1-5. When m is 1 or more, m is an average value. If m exceeds 5, the solubility in the base oil will deteriorate.

(D) component used in the present invention, (poly) a glyceryl ether, (poly) may be a glyceryl ether one, have good even (poly) glyceryl ether 2 or more.

  Content of (D) component used for this invention is 0.05-1.5 mass% with respect to the whole quantity of a heat conductive compound, Preferably it is 0.06-1.0 mass%, More Preferably it is 0.07-0.8 mass%, Most preferably, it is 0.25-0.8 mass%. (D) By increasing the content of the component to 0.05% by mass or more, the amount of the inorganic powder filler is increased by adsorbing to the surface of the inorganic powder filler and improving the affinity with the base oil. It has the function of improving heat conductivity and improving the consistency by increasing the consistency. Moreover, it is presumed that the above-mentioned aluminum soap easily forms a network structure by containing the component (D), thereby tending to improve the bleed resistance, and has a function as a bleed resistance improver. (D) By making content of a component into 1.5 mass% or less, it exists in the tendency which prevents the heat resistant fall of a heat conductive compound.

(E) Unsaturated fatty acid having 10 to 19 carbon atoms In the present invention, an unsaturated fatty acid as component (E) may be further used. The component (E) has 10 to 19 carbon atoms, preferably 12 to 19 carbon atoms, and may be linear or branched. The number of unsaturated bonds may be one or more. The upper limit is 4 or less, preferably 3 or less. Examples of unsaturated fatty acids include decenoic acid, undecenoic acid, palmitoleic acid, oleic acid, elaidic acid, linoleic acid, and linolenic acid. As the unsaturated fatty acid (E), one type may be used, or a mixture of two or more types may be used. By setting the number of carbon atoms to 10 to 19, it is presumed that the above-described aluminum soap easily forms a network structure, and tends to improve bleed resistance.

  Content of (E) component used for this invention is 0.05-1 mass% with respect to the whole quantity of a heat conductive compound, Preferably it is 0.08-0.9 mass%, More preferably It is 0.2-0.9 mass%. When the content of the component (E) is 0.05% by mass or more, it is presumed that the above-described aluminum soap is likely to form a network structure, and tends to improve bleed resistance. (E) By making content of a component into 1 mass% or less, it exists in the tendency which prevents the heat resistant fall of a heat conductive compound.

(F) Other Additives Other known additives can be appropriately blended as the component (F) in the heat conductive compound of the present invention as necessary. These additives include, for example, phenolic, amine and sulfur / phosphorous compounds as antioxidants, and sulfonate, carboxylic acid, carboxylate and other compounds as corrosion inhibitors. Compounds such as benzotriazole and derivatives thereof, thiadiazole compounds as inhibitors, compounds such as succinimide as dispersants, polybutene, polymethacrylate, fatty acid salts, urea compounds as thickeners and thickeners Petroleum wax, polyethylene wax, 12-hydroxystearic acid and the like. The amount of these additives may be a normal amount.

The immiscible penetration of the heat conductive compound of the present invention can be used if it is 200 or more, but it is preferably 220 to 400 from the viewpoints of applicability, spreadability, adhesion and the like.
With respect to the production of the heat conductive compound of the present invention, the method is not limited as long as the components can be mixed uniformly. As a general production method, there is a method of kneading with a mortar, a planetary mixer, a twin-screw extruder, or the like to form a grease and then uniformly kneading with three rolls.

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.

(A-1) Zinc oxide 1 Average particle diameter: 0.2 μm (laser diffraction scattering method)
(A-2) Zinc oxide 2 Average particle diameter: 0.6 μm (laser diffraction scattering method)
(A-3) Zinc oxide 3 Average particle diameter: 11 μm (laser diffraction scattering method)

(B-1) Polyalphaolefin (1-decene-oligomer) 40 ° C. kinematic viscosity: 47 mm ² / s
(B-2) Ester of pentaerythritol and monocarboxylic acid having 8 and 10 carbon atoms 40 ° C. kinematic viscosity: 32 mm ² / s
(B-3) Ester of trimethylolpropane and saturated fatty acid (monocarboxylic acid) having 12 to 18 carbon atoms 40 ° C. kinematic viscosity: 126 mm ² / s
(B-4) Mixing of an ester of neopentyl glycol and a saturated fatty acid (monocarboxylic acid) having 12 to 18 carbon atoms, an ester of trimethylolpropane and a saturated fatty acid (monocarboxylic acid) having 12 to 18 carbon atoms, 40 ° C Kinematic viscosity: 430 mm ² / s

(C-1) Di (2-ethylhexanoic acid) aluminum Total carbon number: 16
(C-2) Aluminum monostearate Total carbon number: 18
(C′-3) Aluminum distearate Total carbon number: 36
(C′-4) Zinc distearate Total carbon number: 36

(D-1) (Poly) glyceryl monooleyl ether A mixture of 92% by weight of monoglyceryl monooleyl ether in which m is 1 in the general formula (1) and polyglyceryl monooleyl ether having a polymerization degree of 2 to 5, The average value is 2.4.
(D-2) Erucic acid

(E) Mixture of unsaturated fatty acids having 14 to 18 carbon atoms (number of unsaturated bonds: 1)
(F-1) Other additives 1 Amine-based antioxidant Dioctyl diphenylamine (F-2) Other additives 2 12-hydroxystearic acid 3-5 molecular polymer

  In addition, (C)% in the liquid component in the table means that the total of the components excluding the inorganic powder filler of the component (A) among the components constituting the composition is 100 parts by mass, The ratio of the component C) to the aluminum soap is shown as mass%.

The heat conductive compound was prepared according to the following preparation method.
(Preparation method 1) A base oil in which various additives including the aluminum soap of the component (C) were dissolved was placed in a planetary mixer together with an inorganic powder filler. The mixture was mixed well for 30 minutes to form a compound. Thereafter, kneading with three rolls was carried out 1 to 3 times to prepare a heat conductive compound.
(Preparation Method 2) A base oil in which various additives other than the component (C) were dissolved was placed in a planetary mixer together with an inorganic powder filler. The component (C) was added to the compounded state, and kneaded for 30 minutes and mixed well. Thereafter, kneading with three rolls was carried out 1 to 3 times to prepare a heat conductive compound.
In the table, preparation method paragraph 1 indicates preparation method 1 and preparation method 2 indicates preparation method 2. The temperature at the time of metal soap addition is shown in the table.

The performance shown below was evaluated using the obtained heat conductive compound.
The immiscible penetration was measured in accordance with JIS-K2220. The larger the immiscible penetration value, the softer the heat conductive compound, and vice versa.
The thermal conductivity was measured at room temperature (25 ° C.) with a rapid thermal conductivity meter QTM-500 manufactured by Kyoto Electronics Industry Co., Ltd.

Bleed resistance is No. manufactured by ADVANTEC. 5A, a heat conductive compound is applied to a central part of a filter paper having a diameter of 100 mm and a cylindrical shape having a diameter of 18 mm and a thickness of 2 mm (≈0.51 mm ³ ). The average (mm) of the vertical and horizontal diameters of the minute was evaluated as the bleed amount. The smaller the bleed amount, the better the bleed resistance. In addition, what protruded the filter paper was> 100 mm. The bleed amount is preferably 70 mm or less, more preferably 60 mm or less, still more preferably 50 mm or less, and particularly preferably 40 mm or less.

Examples 1 to 11 are excellent in bleed resistance and have a high immiscible consistency.
On the other hand, Comparative Example 1 in which the proportion of the component (C) in the liquid component is small has a large amount of bleed and is inferior in bleed resistance, and Comparative Example 2 in which the proportion of the component (C) is large has a small immiscible consistency and coatability. Inferior to In Comparative Example 3, although the percentage is more liquid component (A) component in the composition as compared with Comparative Examples 1 and 2 is small, since containing no component (C), the bleed amount is large. (D) The comparative example 4 which does not contain a component has a small immiscible consistency and a large bleed amount as compared with the example 4. Comparative Example 5 having (C) component but not (D) component, Comparative Example 6 having aluminum distearate having 36 carbon atoms in place of aluminum soap having 12 to 30 carbon atoms as component (C), 7. Comparative Example 8 containing zinc distearate having a total carbon number of 36 instead of aluminum soap having a total carbon number of 12 to 30 as the component (C) is inferior in bleed resistance.

Claims (2)

(A) 75 to 97% by mass of the inorganic powder filler, (B) 2 to 24% by mass of the non-silicone base oil, and (C) 0.15 to 2.5 of the aluminum soap having a total carbon number of 12 to 34. % By mass, 0.05 to 1.5% by mass of (D) (poly) glyceryl ether, and the ratio of component (C) to the content of the liquid component is 1 to 10% by mass Thermally conductive compound. Furthermore, (E) The heat conductive compound of Claim 1 which contains 0.05-1 mass% of C10-C19 unsaturated fatty acid.