WO2008047809A1

WO2008047809A1 - Grease

Info

Publication number: WO2008047809A1
Application number: PCT/JP2007/070200
Authority: WO
Inventors: Toshitaka Yamagata; Takuya Okada; Akira Ubukata
Original assignee: Denki Kagaku Kogyo Kabushiki Kaisha
Priority date: 2006-10-17
Filing date: 2007-10-16
Publication date: 2008-04-24
Also published as: TW200839007A; TWI457434B; CN101528902A; JPWO2008047809A1; JP5231236B2; US20100048435A1

Abstract

It is intended to provide a grease which shows a low heat resistance and has been improved in degradation due to heat cycle, in particular, a grease which is suitable for a heat-conductive material of a heat-generating electronic component. A grease comprising a heat-conductive material powder made up of one or more members selected from the group consisting of a heat-conductive material (A), a heat-conductive material (B) and a heat-conductive (C), in which the heat-conductive material powder has frequency peaks within the ranges of 2.0 to 10 μm, 1.0 to 1.9 μm and 0.1 to 0.9 μm in the grain size distribution determined by the laser diffraction grain size distribution method and which contains a base oil having a surface tension at 25oC of from 25 to 40 dyn/cm.

Description

Specification

Grease

Technical field

[0001] The present invention relates to a thermally conductive grease.

Background art

[0002] With the downsizing and higher output of heat-generating electronic components such as CPUs (central processing units)

The amount of heat per unit area generated by these electronic component forces is becoming extremely large. The amount of heat is about 20 times that of an iron. In order to prevent this heat generating electronic component from failing for a long time, it is necessary to cool the heat generating electronic component. A metal heat sink or case is used for cooling, and a heat-conducting material is used to efficiently transfer heat from heat-generating electronic components to the heat sink or case. As a reason for using this heat conductive material, when the heat-generating electronic component and the heat sink are brought into contact with each other as they are, microscopically, air is present at the interface, which hinders heat conduction. Therefore, heat can be efficiently transferred by allowing a heat conductive material to exist between the heat-generating electronic component and the heat sink in place of the air present at the interface.

[0003] The thermally conductive material is a thermally conductive sheet made of a cured product obtained by filling a silicone rubber with a thermally conductive powder; a soft silicone such as a silicone gel is filled with the thermally conductive powder and has flexibility. Thermally conductive pads made of cured products; fluid thermal grease with liquid silicone filled with thermal conductive powder; phase change thermal conductive material that softens or fluidizes at the operating temperature of heat-generating electronic components is there. Among these, heat conductive grease is particularly easy to conduct heat.

[0004] Thermally conductive grease is obtained by adding thermally conductive powder to a base oil which is a liquid silicone such as silicone oil. In order to satisfy the requirement for high thermal conductivity, it has been proposed to use aluminum nitride powder as the thermal conductive powder (Patent Document 1). However, since aluminum nitride powder has a hexagonal crystal structure and is non-spherical in shape, there is a limit to increasing the filling amount of the heat conductive powder to achieve high heat conductivity.

[0005] Alumina powder and aluminum nitride powder (Patent Documents 2 and 3), or alumina powder and metal When Noreminium powder (Patent Document 4) is used in a base oil that is dimethylsilicone oil, it has high heat conductivity. A so-called “oil-release” occurs in which the silicone oil component separates, increasing the thermal resistance.

[0006] On the other hand, in order to solve the problem of separation of the silicone oil component, which is a base oil, it has been proposed to use a special silicone (Patent Document 5). Tsu! /, It ’s listed here!

Patent Document 1: Japanese Unexamined Patent Publication No. 2000-169873

Patent Document 2: Japanese Patent Laid-Open No. 2002-194379

Patent Document 3: Japanese Patent Laid-Open No. 2005-54099

Patent Document 4: Japanese Unexamined Patent Publication No. 2005-1 70971

Patent Document 5: Japanese Unexamined Patent Application Publication No. 2004-91 7743

Disclosure of the invention

Problems to be solved by the invention

[0007] An object of the present invention is to provide a grease exhibiting low thermal resistance and improved deterioration due to heat cycle, particularly a grease suitable for a heat conductive material of a heat-generating electronic component.

Means for solving the problem

The present invention employs the following means in order to solve the above problems.

(1) containing one or more heat conductive material powders selected from the group consisting of a heat conductive material (A), a heat conductive material (B), and a heat conductive material (C), The thermally conductive material powder has a particle size distribution measured by the laser diffraction particle size distribution method of 2.0-lO ^ m, 1.0-; ί · μΐΐΐ ^ and 0 ·;!-0 · Grease having a frequency maximum in the range of 9 m and containing a base oil with a surface tension of 25 to 40 dyn / cm at 25 ° C.

(2) a heat conductive material (A) having an average particle size of 2.0 to 10; a heat conductive material (B) having an average particle size of 1.0 to 1.9; and an average particle size of A grease characterized by comprising a thermally conductive material (C) of 0 to; to 0.9 and a base oil having a surface tension of 25 to 40 dyn / cm at 25 ° C.

(3) Thermally conductive material (A), (B), or (C) is composed of metallic aluminum, aluminum nitride and The grease according to (1) or 2, wherein the grease is one or more selected from the group consisting of zinc oxide.

(4) The thermal conductive material (A) is metallic aluminum, the thermal conductive material (B) is aluminum nitride, and the thermal conductive material (C) is zinc oxide (1) or Grease as described in said (2).

(5) The grease according to any one of (1) to (4)! /, Which is a viscosity of 00--OOOOmPa · s.

(6) The grease according to any one of (1) to (5), wherein the base oil is a silicone oil modified with an alkyl group.

(7) The heat conductive material (A), (B), and (C) content is 60 to 80% by volume. Grease.

(8) Among all the thermally conductive materials, the thermally conductive material (A) is 50 to 70% by volume, the thermally conductive material (B) is 30 to 20% by volume, and the thermally conductive material (C). The grease according to any one of the above (1) to (7)! /, Which is 20 to 10% by volume.

(9) The grease according to any one of (1) to (8), further comprising a silane coupling agent.

(10) The grease according to any one of (1) to (9), wherein the thermal resistance is 0.2 ° C / W or less.

The invention's effect

The present invention provides a grease suitable for thermal conductivity against heat generated from an electronic component. Grease with low thermal resistance and improved deterioration due to heat cycle.

BEST MODE FOR CARRYING OUT THE INVENTION

[0010] The thermal conductive material (A), (B), or (C) contained in the grease of the present invention is one or two selected from the group consisting of metallic aluminum, aluminum nitride, and zinc oxide. More than a seed. The thermally conductive material (A), (B), or (C) is, for example, a thermally conductive powder such as metal tin, metal silver, metal copper, silicon carbide, aluminum oxide, silicon nitride, or boron nitride powder. The total amount of metallic aluminum, aluminum nitride and zinc oxide is preferable. Up to 5% by volume, particularly preferably up to 3% by volume, can be used.

[0011] In the grease of the present invention, the powder of the heat conductive material contained in the particle size distribution measured by the laser diffraction particle size distribution method is 2 · O-lO ^ m, 1.0∼; By having a frequency maximum in the range of 9 μΐ ^ and 0.;! To 0.9 in, the force S can be increased to increase the number of contact points between the thermally conductive materials. As a result, the thermal conductivity as grease can be improved. One of the means having the particle size distribution of the heat conductive material powder having such a frequency maximum value is a method of mixing heat conductive materials having different particle size distributions.

[0012] Thermally conductive materials (A), (Β), and (C) with different average particle diameters are mixed to increase the fillability of the thermally conductive material by mixing the three types of thermally conductive materials. Can do. That is, a thermally conductive material (Α) having an average particle diameter of 2.0 to 10 m, a thermally conductive material (B) having an average particle diameter of 1.0 to 1.9 m, and an average particle diameter By mixing the heat conductive material (C) which is 0.;! ~ 0.9 ^ 111, the filling property of the heat conductive material can be improved. As a result, the thermal conductivity as grease can be improved. Further, the heat conductive material is preferably contained by including a heat conductive material made of a material having an average particle size of preferably 0.;! To 10 m, preferably 0.3 to 6 m. The grease filled with can be made thinner, and the thermal resistance (easy heat transfer) becomes smaller. This makes it possible to produce grease that is very easy to conduct heat.

[0013] The heat conductive material (Α) having an average particle diameter of 2.0 to 10 μm used in the present invention needs to have an average particle diameter of 20 · 10 to 10 m, and further has an average particle diameter of Is preferably in the range of 3 to 6 m. When the average particle size is larger than 10 inches, it is difficult to make the grease thin, and the thermal resistance of the grease tends to increase. On the other hand, when the average particle size is smaller than 2.0 111, the heat conductive material (A) is preferably metallic aluminum.

[0014] The thermally conductive material (Β) having an average particle size of 1.0 to 1. 9 um used in the present invention needs to have an average particle size of 1 · 0 to; The average particle size is preferably in the range of 1-3. When the average particle size is larger than 1.9 in, the particle size is close to that of the thermally conductive material with an average particle size of 2.0 to 10 m, so the packing property tends to deteriorate and the thermal resistance tends to increase. It is in. On the other hand, if the average particle size is smaller than 1 am, the average particle size becomes 0.;! ~ 0.9 in. The filling property of the material tends to deteriorate, and the thermal resistance tends to increase. As the heat conductive material (B), aluminum nitride is preferable.

[0015] The zinc oxide powder used in the present invention has an average particle size of 0 .;! To 0.9. The heat conductive material (C) must have an average particle size of 0 .;! To 0.9. Further, those having an average particle diameter in the range of 0.3 to 0.7 μm are preferable. When the average particle size is larger than 0.9 mm, the average particle size is 1.0 to 1.9. Resistance tends to increase. When the average particle size is smaller than 0.1 l ^ m, the filling property of the whole heat conductive material tends to deteriorate, and the thermal resistance tends to increase. As the heat conductive material (C), zinc oxide is preferable.

[0016] The content of the heat conductive material (A), (B), and (C) in the grease is 60 to 80% by volume, preferably S, and more preferably 65 to 75% by volume. When the content of the heat conductive material exceeds 80% by volume, the grease tends to become hard and the thermal resistance tends to increase. Also, if the content of the heat conductive material is less than 60% by volume, the heat conductive material tends to be difficult to transfer because the filling amount of the heat conductive material is small, and the thermal resistance tends to increase.

[0017] The blending ratio of the three types of heat conductive materials having different average particle diameters is preferably 50 to 70% by volume, particularly preferably 55 to 65% by volume in the heat conductive material (A). The material (B) is preferably 30-20% by volume, particularly preferably 27-25% by volume, and the thermally conductive material (C) is preferably 20-; 10% by volume, particularly preferably 17-13% by volume. % Is preferred. When the content of the heat conductive material (A) is less than 50% by volume, the dullies tend to become hard and the thermal resistance tends to increase. On the other hand, if it exceeds 70% by volume, the filling property of the heat conductive material tends to deteriorate, and the thermal resistance tends to increase.

The average particle size in the present invention was measured using “Laser Diffraction Particle Size Distribution Measuring Device SALD-200” manufactured by Shimadzu Corporation. As an evaluation sample, 5 g of 50 cc pure water and a heat conductive powder to be measured were added to a glass beaker, stirred with a spatula, and then subjected to a dispersion treatment for 10 minutes with an ultrasonic cleaner. The powder solution of the thermally conductive material that had been subjected to the dispersion treatment was added drop-wise to the sambra portion of the apparatus using a spoid, and waited until the absorbance became measurable. When the absorbance becomes stable in this way, measure. Laser diffraction particle size distribution analyzers use particles detected by sensors. The particle size distribution is calculated from the light intensity distribution data of diffracted / scattered light. The average particle size is obtained by multiplying the measured particle size value by the relative particle amount (difference%) and dividing by the total relative particle amount (100%). The average particle diameter is the average diameter of the particles.

[0019] The base oil used in the present invention has a surface tension of 25 to 40 dyn / cm at 25 ° C, particularly preferably 30 to 35 dyn / cm. If the surface tension is less than 25 dyn / cm, the base oil tends to separate due to repeated heat cycles on the grease, which tends to cause the grease to become harder and heat conductivity to deteriorate. . On the other hand, if the surface tension force is greater than 0 dyn / cm, the wettability of the grease tends to be poor, and the thermal conductivity tends to be poor because the grease is difficult to spread.

[0020] Surface tension is a property of a liquid that tends to make the surface as small as possible, and is a kind of interfacial tension. When in contact with a liquid or gas, the liquid has the property of reducing the surface area as much as possible. While the molecules in the liquid are attracted from the surroundings, the molecules on the surface are not affected by the attraction of the liquid molecules only in the parts not touching the liquid. Accordingly, the molecules on the surface have excess energy, which is the strength of the surface tension. When this surface tension becomes strong and shows a large value, the base oil is separated from the dull.

In the present invention, the Wilhelmy method is preferable as a method for measuring the surface tension. In the Wilhelmy method, when a plate (mainly a platinum plate) is immersed perpendicularly to the liquid level, the liquid wets, but the surface tension works to reduce the area of the increased liquid level. This force is calculated as the force per length (dyne / cm) divided by the perimeter of the plate (twice the sum of width and thickness). This determines the surface tension. As an apparatus for measuring surface tension, an “automatic surface tension meter” manufactured by Kyowa Interface Chemical is used.

[0022] The surface tension of the base oil can also be adjusted by adding an additive having a low surface tension and a large base oil surface tension. For example, the force S is used to adjust the surface tension by adding a silane coupling agent having an alkyl group to dimethylsilicone oil having a low surface tension.

[0023] The viscosity of the base oil is preferably 300 to 1000 mPa-s, and particularly preferably 500 m to 700 mPa's. If the base oil has a viscosity of less than 300 mPa's, One base oil and a thermally conductive material tend to be separated, and the thermal resistance tends to increase. When the viscosity of the base oil exceeds lOOOOmPa's, it tends to be difficult to fill the heat conductive material at a high level, and the thermal conductivity of the grease tends to deteriorate.

[0024] The viscosity of the base oil is measured using "Digital Viscometer DV-I" manufactured by Brookfield. Using the RV spindle set, use rotor No. 1 and use a container that can contain the rotor and base oil up to the reference line. Immerse the rotor in base oil and evaluate the viscosity value at lOrp m.

[0025] In the present invention, as the base oil, the surface tension is preferably 25 to 40 dyn / cm and the viscosity is 300 to; the methyl group of dimethylsilicone oil having lOOOOPa's has 3 or more carbon atoms, It is particularly preferable to use a silicone oil which is modified with an alkyl group of 8 to 12 and has a surface tension of preferably 27 to 37 dy n / cm and a viscosity of 400 to 800 mPa's. Silicone oil modified with an alkyl group has a large surface tension, and when it is made dull, it can suppress deterioration of thermal resistance due to heat cycle.

[0026] The grease of the present invention contains a silane coupling agent, and can make the filler hydrophobic as a surface modifier, improve dispersibility, and modify other organic resins. Suitable silane coupling agents include alkyl silanes having an alkyl group having 8 to 10 carbon atoms. Examples of preferred silane coupling agents include n-octyltrimethoxysilane, n-octyltriethoxysilane, _n -decyltrimethoxysilane and the like.

In addition to the above-described components, the grease of the present invention may further contain an antioxidant, a metal corrosion inhibitor and the like as necessary.

[0028] The grease of the present invention can be produced by kneading the above materials with a universal mixing stirrer, kneader, hybrid mixer or the like.

[0029] The thermal resistance of the grease can be measured using a rectangular copper jig with a heater embedded in a lcm ² (lcm X lcm) tip and a rectangular copper jig with a cooling fin attached to a lcm ² tip. (1cm x lcm) with grease between them, applying a load of 4kg per square centimeter to bring the sample and the copper jig in close contact. The amount of the sample should be such that the entire contact surface is filled. Apply 20W power to the heater and hold it for 30 minutes, measure the temperature difference (° C) between copper jigs, formula, thermal resistance (° C / W) = (temperature difference (° C) / power (W) }. The thermal resistance of the grease according to the present invention is preferably in consideration of the thermal conductivity of the grease.

0.2 ° C / W or less, particularly preferably 0. C / W or less is preferred.

[0030] For grease separation conditions of the present invention, a thickness of ^{lmm 10000mm 2 (100mm X 10 Omm} ) of 900mm in thickness 100 mu m between the transparent glass plates are of the area ² (30mm X 30 mm) In this state, a heat cycle test was performed at 40 ° C for 30 minutes and 130 ° C for 30 minutes. The number of cycles is 100. The weight of the base oil separated from the thermally conductive dull was measured to evaluate the separation.

Example

[0031] (Examples;! To 24 comparative examples;! To 8)

The heat conductive materials (A), (B), (C) shown in Table 1, the base oil (D) shown in Table 2, and the silane coupling agent (E) shown in Table 3 are used in Tables 4-6. And blended for 5 minutes using “Shintaro Awatori AR-250” manufactured by Shinky to produce grease. Table 4 shows the results of evaluating the thermal resistance and separation state of the obtained grease. In the evaluation results, a heat conductive grease with a thermal resistance exceeding 0.2 ° C / W has a thermal characteristic and can efficiently transfer heat from the heat generating part to the cooling part.

[0032] [Table 1]

table 1

[0033] [Table 2] Table 2

[0034] [Table 3] Table 3

[0035] [Table 4]

[0036] [Table 5]

6]

6

[0038] The grease of the present invention exhibits low thermal resistance, and can efficiently transfer heat from a heat generating electronic component that is less deteriorated by heat cycle to a cooling part such as a heat sink or a casing. Industrial applicability

[0039] The thermally conductive grease according to the present invention is suitably used in various fields, but in particular, because it can efficiently transfer heat by being present between a heat-generating electronic component and a heat sink, etc. Used for cooling electronic parts that generate heat. The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2006-282457, filed on October 17, 2006, are cited herein as the disclosure of the specification of the present invention. Incorporated.

Claims

The scope of the claims

[1] containing one or more heat conductive material powders selected from the group consisting of a heat conductive material (A), a heat conductive material (B), and a heat conductive material (C), The frequency of the thermal conductive material powder in the range of 2. 1. 0 ~; ί · 9 μ ΐ ^ and 0 .;! ~ 0 · 9 m in the particle size distribution measured by the laser diffraction particle size distribution method. A grease having a maximum value and containing a base oil having a surface tension of 25 to 40 dyn / cm at 25 ° C.

[2] Thermally conductive material (Α) with an average particle size of 2.0 to 10 μm, thermal conductive material (Β) with an average particle size of 1. 0 to 1.9 μm, and average particle size A grease characterized by comprising a thermally conductive material (C) of 0 .;! To 0.9, and a base oil having a surface tension of 25 to 40 dyn / cm at 25 ° C.

[3] The heat conductive material (A), (B), or (C) is one or more selected from the group consisting of metallic aluminum, aluminum nitride, and zinc oxide. Dally listed.

[4] The heat conductive material (A) is metallic aluminum, the heat conductive material (B) is aluminum nitride, and the heat conductive material (C) is zinc oxide. Grease

[5] The grease according to any one of claims 1 to 4, wherein the base oil has a viscosity of 300 to 1000 mPa's.

6. The grease according to any one of claims 1 to 5, wherein the base oil is a silicone oil modified with an alkyl group.

[7] The content of the heat conductive material (A), (B), and (C) is 60 to 80% by volume.

Any force of 6, grease according to item 1.

[8] Among all the heat conductive materials, the heat conductive material (A) is 50 to 70% by volume, and the heat conductive material (B

The grease according to any one of claims 1 to 7, wherein the thermal conductive material (C) is 20 to 10% by volume.

[9] The grease according to any one of claims 1 to 8, further comprising a silane coupling agent.

[10] The grease according to any one of claims 1 to 9, having a thermal resistance of 0.2 ° C / W or less.