JP4652085B2 - High thermal conductivity compound - Google Patents

Description

  The present invention relates to a high thermal conductivity compound having extremely high thermal conductivity, and relates to a high thermal conductivity compound with little oil separation and excellent coating properties.

  Among semiconductor components used in electronic devices, there are components that generate heat during use, such as a CPU for a computer and a power semiconductor for power control. 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 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 increase heat conduction. The thermal conductivity of these joints is better as the thermal conductivity of the thermal conductive compound is higher, and is higher as the coating property is better (the thinner the coating film, the higher the adhesion).

A thermal conductive compound is a grease-like composition having an increased thermal conductivity by dispersing a large amount of a filler having a high thermal conductivity in a base oil. Generally, silicone oil is used as the base oil, and the filler is dispersed with a silane-based surface modifier or the like. As the filler, metal oxides such as zinc oxide and aluminum oxide, nitrides such as silicon nitride, aluminum nitride, and boron nitride, and metal powders such as aluminum and copper are used. As a specific example of a conventional heat conductive compound, for example, a technique of dispersing silicon nitride in silicone oil is disclosed (see Patent Document 1). In addition, a technique of using liquid hydrocarbon or fluorine oil as a base oil and combining with a specific inorganic filler for the purpose of improving applicability and thermal conductivity is disclosed (see Patent Document 2).
Japanese Patent Laid-Open No. 9-97988 Japanese Patent No. 2938428

In a thermally conductive compound using silicone oil as a base oil, the oil component may be easily separated during use because the surface tension of the silicone oil is small. Thereby, when a compound becomes hard, peeling and a crack may be produced and adhesiveness may be impaired, and thermal conductivity may fall.
In general, the thermal conductivity of the thermally conductive compound increases as the amount of the filler increases. On the other hand, when the amount of the filler increases, the consistency decreases and there is a possibility that sufficient coatability may not be obtained. In this case, the film thickness of the coating film increases or air bubbles are mixed in, resulting in hindering heat conduction.
An object of the present invention is to provide a high thermal conductivity compound having high thermal conductivity, excellent coating properties, and less oil separation.

As a result of intensive investigations to achieve the above-mentioned problems, the present inventors have found that by adding a specific surface modifier, the compound can be highly filled with an inorganic filler without being hardened. It came.
That is, the present invention comprises (A) a combination of a coarse inorganic filler having an average particle diameter of 5 to 50 μm and a fine inorganic filler having an average particle diameter of 0.15 to 2 μm, and the mass ratio thereof is 20: 88 to 97% by weight of inorganic filler in the range of 80 to 85:15,
(B) less than 12% by weight of base oil,
(C) a polymeric surface modifier represented by the general formula (1) having a polyoxyalkylene group and an acid anhydride group,

(In the formula, AO is an oxyalkylene group, R ¹ is a hydrocarbon group having 1 to 24 carbon atoms, n is 1 to 150, and m is a number having a weight average molecular weight in the range of 500 to 100,000. 0.08-4% by mass of (poly) glyceryl ether and one or more selected from alkenyl succinimide and its boron derivative,
The present invention provides a high thermal conductivity compound characterized by containing each of them.
The present invention also provides a high thermal conductivity compound, 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 compound, wherein the base oil is at least one selected from mineral oil, synthetic hydrocarbon oil, diester, polyol ester and phenyl ether. .
Further, the present invention provides a high thermal conductivity compound in which the base oil contains one or more selected from diesters and polyol esters, and the content thereof is 2 to 90% by mass in the base oil. It is to provide.

  The high thermal conductivity compound of the present invention increases the filling amount of the inorganic filler by the effect of a specific surface modifier, and realizes excellent thermal conductivity without impairing the coating property. By using the high thermal conductivity compound of the present invention, it is possible to improve the heat dissipation of electronic parts that require heat countermeasures, and it is particularly suitable as a heat dissipation material for CPUs and power semiconductors. Furthermore, the high thermal conductivity compound of the present invention is excellent in press thin film formation and can be easily formed into a thin film.

  The inorganic filler (A) used in the present invention comprises a coarse inorganic filler having an average particle diameter of 5 to 50 μm and a fine inorganic filler having an average particle diameter of 0.15 to 2 μm. When the average particle diameter of the coarse inorganic filler exceeds 50 μm, the coating film becomes thick and the thermal conductivity tends to decrease. If the average particle size of the fine inorganic filler is less than 0.15 μm, the surface area of the filler is too large, the liquid components (base oil and surface modifier) are insufficient, and the consistency is low. It tends to be low or the compound cannot be prepared. On the other hand, when the average particle diameter of the coarse inorganic filler is less than 5 μm, or when the average particle diameter of the fine inorganic filler exceeds 2 μm, the inorganic filler may not be able to be closely packed. As a result, there is a tendency that sufficient thermal conductivity cannot be obtained. The average particle diameter of the coarse inorganic filler is preferably 5 to 40 μm, particularly preferably 8 to 30 μm. The average particle size of the fine inorganic filler is preferably 0.2 to 1.8 μm, particularly preferably 0.3 to 1.5 μm.

  Further, the mixing ratio of the coarse inorganic filler and the fine inorganic filler is preferably mixed in the range of 20:80 to 85:15 by mass ratio. If there are too many fine inorganic fillers, the surface area of the filler may become too large, resulting in a lack of liquid components (base oil and surface modifier), and a low consistency or a compound that may not be prepared. On the other hand, if the fine inorganic filler is insufficient, the inorganic filler may not be close-packed, and as a result, sufficient thermal conductivity may not be obtained.

  The type of inorganic filler is not particularly limited as long as it has a higher thermal conductivity than the base oil. For example, zinc oxide, magnesium oxide, aluminum oxide, titanium oxide, silicon nitride, boron nitride, aluminum nitride, and nitride Examples include titanium, silica, silicon carbide, diamond, nanocarbon, carbon nanotube, carbon nanofiber, and various metal powders. Among these, powders of zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride, boron nitride, and silicon carbide are preferable, and powders of zinc oxide, magnesium oxide, aluminum oxide, and silicon carbide are particularly preferable. One kind of the inorganic filler of the present invention may be used, or two or more kinds may be used in combination.

  Although the content rate of an inorganic filler is 88-97 mass%, it is excellent in thermal conductivity, so that a content rate is high, Preferably it is 90-97 mass%, More preferably, it is 92-96 mass%. If it is less than 88% 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, and the compound will not be prepared.

Various base oils can be used as the base oil (B), and examples thereof include mineral oil, synthetic hydrocarbon oil, ester, polyether, phosphate ester, silicone oil, and fluorine oil. In terms of preventing separation of the base oil, silicone oil and fluorine oil having a low surface tension are less preferred. A base oil may be used individually by 1 type, or may be used in combination of 2 or more type.
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. 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 esters 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.
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.
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.

Examples of the polyether 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 represented by the following general formula (2).

(Wherein R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ are a hydrogen atom or a hydrocarbon group having 1 to 22 carbon atoms, (At least one of R ^{2 to} R ¹¹ is a hydrocarbon group having 8 to 22 carbon atoms.)
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 a high temperature for a long time. For this reason, it is desirable that the base oil has excellent thermal oxidation stability. The kinematic viscosity of the base oil is preferably 10mm ² / s~500mm ² / s at 40 ° C.. If the viscosity is too low, evaporation or oil separation may occur at high temperatures. On the other hand, if the viscosity is too high, the consistency is lowered and the compound may be hardened.

Diesters and polyol esters can increase the consistency when used in combination with other base oil components. In that case, 1 type may be sufficient as the diester and polyol ester to combine, and 2 or more types may be combined. Further, the ratio of the diester or polyol ester is preferably 2 to 90% by mass, more preferably 2 to 50% by mass, and still more preferably 4 to 100% by mass of all base oil components including the diester or polyol ester. -30 mass%. By blending a diester or a polyol ester within the above range, a higher consistency can be achieved.
The content of the base oil is less than 12% by mass, preferably 2 to 12% by mass. When the content is more than this, the consistency becomes too high and the compound may flow out. In addition, oil separation may occur and thermal conductivity may decrease.

The surface modifier (C) used in the present invention improves the thermal conductivity by increasing the filling amount of the inorganic filler by adsorbing to the surface of the inorganic filler powder and improving the affinity with the base oil. It has the function of improving the coating properties by increasing the consistency. In addition, by using the surface modifier of this invention, a coating film can be made still thinner and the heat conduction from a heat-emitting component to a thermal radiation component can be performed efficiently. Therefore, for example, even if the compound is less than 4 W / m · K, efficient heat conduction is possible by thinning the film using the surface modifier of the present invention.
Furthermore, the surface modifier (C) used in the present invention has high heat resistance as compared with substances conventionally used as surface modifiers. Therefore, it is possible to obtain a compound having good heat and oxidation stability of oil and high heat resistance.
Examples of the surface modifier include a polymer surface modifier represented by the general formula (1) having a polyoxyalkylene group and an acid anhydride group, (poly) glyceryl ether, alkenyl succinimide and boron thereof. Derivatives can be preferably used.

In the general formula (1), AO is an oxyalkylene group having 2 to 4 carbon atoms, and the oxyalkylene group is one or more selected from an oxyethylene group, an oxypropylene group, and an oxybutylene group. As the oxyalkylene group, an oxybutylene group is preferable. When there are two or more oxyalkylene groups, a random structure or a block structure may be used. R ¹ is a hydrocarbon group having 1 to 24 carbon atoms, preferably a hydrocarbon group having 10 to 22 carbon atoms, and more preferably a hydrocarbon group having 14 to 20 carbon atoms. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an aryl group, and the like, and an alkyl group and an alkenyl group are preferable. n is 1-150, preferably 5-100. m represents the degree of polymerization and is a number with a weight average molecular weight in the range of 500 to 100,000, preferably a number with a weight average molecular weight in the range of 2,000 to 50,000, particularly preferably 5,000. A number in the range of ~ 40,000.

一般式（３）において、Ｒ^１２は炭素数８以上の炭化水素基を表わし、例えば、炭素数８以上のアルキル基、アルケニル基、アリール基が挙げられ、炭素数８以上のアルキル基、アルケニル基が好ましい。Ｒ^１２の炭素数は、８〜３０が好ましく、１０〜２６がより好ましく、１２〜２２が特に好ましい。また、一般式（３）において、ｐはグリセリンの重合度を表わす係数であって、１以上の数であり、好ましくは１〜５の数である。なお、ｐが１以上の場合は、ｐは平均値である。ｐが５を越えると基油への溶解性が悪くなる。 (Poly) glyceryl ether is a compound represented by the general formula (3).

In the general formula (3), R ¹² 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, and an alkyl group and alkenyl group having 8 or more carbon atoms. Is preferred. The number of carbon atoms in R ¹² is preferably 8 to 30, more preferably from 10 to 26, particularly preferably 12 to 22. Moreover, in General formula (3), p is a coefficient showing the polymerization degree of glycerol, is a number of 1 or more, preferably a number of 1-5. In addition, when p is 1 or more, p is an average value. If p exceeds 5, the solubility in the base oil will deteriorate.

The alkenyl succinimide and its boron derivative are compounds represented by the general formula (4).

In the general formula (4), R ¹³ is an alkenyl group or polyalkenyl group having 1 to 50 carbon atoms, and two R ^{13 s} may be the same or different. Examples of the alkenyl group include a propenyl group, a butenyl group, and a pentenyl group. Examples of the polyalkenyl group include a polypropenyl group, a polybutenyl group, and a polypentenyl group. R ¹⁴ is an alkylene group having 2 to 5 carbon atoms. q is 1 to 10, and q + 1 R ¹⁴ may be the same or different. X is a boron-containing substituent, and examples of X include a group of the chemical formula (5).

At this time, the molecular weight of the polyalkenyl group is preferably about 70 to 50000, more preferably 200 to 5000, and particularly preferably 500 to 3000.
A surface modifier (C) may be used individually by 1 type, and may be used in combination of 2 or more type.
The surface modifier used in the present invention is preferably contained in an amount of 0.08% by mass to 4.0% by mass. More preferably, it is 0.1-3.0 mass%, Most preferably, it is 0.1-2.0 mass%. When the content is less than 0.08% by mass, the effect is small, and even when the content is more than 4.0% by mass, the improvement of the effect cannot be expected. These surface modifiers may be used alone or in combination of two or more.

  Moreover, a well-known additive can be suitably mix | blended with the high heat conductive compound of this invention as needed. These include, for example, compounds such as phenols, amines and sulfur / phosphorus as antioxidants, and compounds such as sulfonates, carboxylic acids and carboxylates as corrosion inhibitors as rust inhibitors. Are compounds such as benzotriazole and derivatives thereof, and thiadiazole compounds, and examples of the thickener and 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.

Regarding the production of the high thermal conductivity 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.
The consistency of the high thermal conductive compound of the present invention can be used as long as it is 200 or more, but is preferably 250 to 430 from the viewpoints of applicability, spreadability, adhesion, and oil separation prevention.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by this.
Tables 1 to 3 show fillers, base oils and surface modifiers used in Examples and Comparative Examples.

表中、Ｐｈｅ１は、一般式（２）のＲ^２〜Ｒ^１１のうち、１つ又は２つが炭素数１２と炭素数１４の直鎖又は分岐鎖アルキル基のものを示す。

In the table, Phe1 represents one of R ^{2 to} R ^{11 in} the general formula (2) in which one or two are linear or branched alkyl groups having 12 and 14 carbon atoms.

(Examples 1-27)
The compositions of Examples 1 to 27 are shown in Tables 4 to 9 below. In addition, other * in the table indicates an amine-based antioxidant.
The compositions shown in Tables 4 to 9 were blended to prepare a heat conductive compound by the following method.
Various additives such as surface modifiers and antioxidants were dissolved in the base oil and placed in a planetary mixer or automatic mortar together with the inorganic filler. The mixture was kneaded at room temperature to 60 ° C. for 30 minutes and mixed well to obtain a grease. Thereafter, kneading with a three roll was carried out twice to prepare a heat conductive compound.
The performance shown below was evaluated using the obtained heat conductive compound. For the penetration, the immiscibility penetration was measured according to JIS-K2220. The greater the consistency value, the softer the compound, and vice versa. The degree of oil separation was measured according to JIS-K2220. The thermal conductivity was measured at a measurement temperature of 0 ° C. by a hot wire method. These measurement results are shown in Table 12. The thermal stability test was performed by sandwiching 0.25 ml of a heat conductive compound between iron plates, forming a thin film to a thickness of 200 μm, and heating at 120 ° C. for 1000 hours or 150 ° C. for 500 hours, and then measuring the consistency. The measurement results are shown in Table 14. In the thin film test, 0.05 ml of thermal conductive compound is sandwiched between two aluminum plates with a surface roughness of Ra = 0.5 μm and crushed under a load of 3 kg, and the spreading area after 300 seconds is measured. The film thickness was calculated. The measurement results are shown in Table 15.

(Comparative Examples 1-8 )
Tables 10 and 11 below show the compositions of Comparative Examples 1 to 8 . In addition, other * in the table indicates an amine-based antioxidant.
The compositions shown in Table 10 and Table 11 were blended to prepare a thermally conductive compound in the same manner as in Example 1.

Table 12 shows the immiscibility penetration, thermal conductivity, and oil separation of Examples 1 to 27. Table 13 shows the immiscibility penetration, thermal conductivity, and oil separation degree of Comparative Examples 1 to 8 .

As can be seen from Table 12, in Examples 1 to 27, even when the filler is highly filled to increase the thermal conductivity, the consistency is high and the coating property is excellent, and the occurrence of oil separation is not observed.
On the other hand, as can be seen from Table 13, in Comparative Examples 1 and 2 in which only a fine inorganic filler is used for high filling, the liquid component is insufficient and it does not become grease. In Comparative Example 3 using only coarse inorganic fillers, the thermal conductivity is poor, and the consistency is too high, so the oil separation is large and the stability tends to be poor. If the surface modifier is not blended or is too little, the consistency will be low, and the compound will be hard or not greased (Comparative Examples 4 and 5). In Comparative Example 6 in which the amount of the inorganic filler is small, a high consistency is obtained, but the thermal conductivity is lowered . In Comparative Examples 7 and 8 using a surface modifier other than the component (C) of the present invention, it can be seen that when the filling rate is increased, it does not become a grease.
Further, as can be seen from Table 14, Example 23 remains in a grease state even after receiving a heat load. Further, as can be seen from Table 15, Examples 7, 8, and 23 can be easily thinned even in a pressure thinning test that simulates bonding between a semiconductor and a heat sink.

  The high thermal conductivity compound 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 (4)

(A) Composed of a combination of a coarse inorganic filler having an average particle diameter of 5 to 50 μm and a fine inorganic filler having an average particle diameter of 0.15 to 2 μm, and the mass ratio thereof is 20:80 to 85:15 88-97 mass% of inorganic filler in the range,
(B) less than 12% by weight of base oil,
(C) a polymeric surface modifier represented by the general formula (1) having a polyoxyalkylene group and an acid anhydride group,

(In the formula, AO is an oxyalkylene group, R ¹ is a hydrocarbon group having 1 to 24 carbon atoms, n is 1 to 150, and m is a number having a weight average molecular weight in the range of 500 to 100,000. 0.08-4% by mass of (poly) glyceryl ether and one or more selected from alkenyl succinimide and its boron derivative,
High thermal conductivity compound characterized by containing each.   The high thermal conductivity compound 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 conductivity compound 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.   The base oil contains 1 or more types chosen from diester and a polyol ester, The content is 2-90 mass% in base oil, The high heat conductive compound in any one of Claims 1-3.