JPH08208993A - Thermally conductive silicone composition - Google Patents

Abstract

PURPOSE: To obtain a composition which retains high heat conductivity, does not have too high a viscosity, and has a satisfactory workability by compounding a polyorganosiloxane with a polyorganohydrogensiloxane, a platinum catalyst, a heat-conductive filler, and an organosilicon compound adhesive. CONSTITUTION: This composition comprises 100 pts.wt. polyorganosiloxane (A) containing at least two Si-bonded alkenyl groups per molecule and having a viscosity (25 deg.C) of 50-100,000; a polyorganohydrogensiloxane (B) containing at least three Si-bonded hydrogen atoms per molecule in such an amount that the number of Si-bonded hydrogen atoms is 0.5-4.0 per alkenyl group contained in the component (A); a catalyst (C) selected among platinum and platinum compounds in an amount of 0.1-100ppm by weight in terms of platinum based on the component (A); 100-800 pts.wt. heat-conductive filler (D) having an average particle diameter of 5-20μm and containing at least 20% particles of 510μm; and 0.001-10 pts.wt. organosilicon compound adhesive (E) having an Si-H bond and an epoxy or another functional group in the molecule.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat conductive silicone composition, and more particularly to a heat conductive silicone composition useful as a heat radiating potting agent or an adhesive for electric / electronic materials.

[0002]

TECHNICAL BACKGROUND AND PROBLEMS OF THE INVENTION In order to prevent heat generation of a semiconductor element such as a power transistor, a heat radiating grease and a heat radiating sheet having good thermal conductivity have been used between the heat radiating fin and the semiconductor element. . The heat-dissipating grease is still used in large quantities because it can be easily applied without being affected by the shape of the semiconductor element. However, there are problems such as contamination of other parts and oil outflow after long-term use. On the other hand, the heat dissipation sheet does not have a problem of polluting other parts or outflow of oil, but it needs to be molded according to the shape of the semiconductor element.
In addition, there is a problem that the heat is dissipated due to bending due to screwing or the like.
For that reason, a method of using the liquid silicone rubber composition as a potting agent or an adhesive has been proposed (Japanese Patent Laid-Open No. 61-157569). However,
Such a current composition has an excessively high viscosity when the amount of the filler is increased in order to improve the heat dissipation effect.
When applying such a composition to the semiconductor and the heat radiation fin, there is a problem that not only uniform coating becomes impossible, but also air is mixed and heat radiation is deteriorated.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a heat conductive silicone composition having a high heat conductivity, a high viscosity and a good workability.

[0004]

The present inventor has conducted extensive studies to achieve the above object, and as a result, by limiting the particle size of the thermally conductive filler, the viscosity is too high even if the thermal conductivity is increased. The inventors have found that it does not occur and have completed the present invention. According to the present invention, (A) at least two alkenyl groups bonded to a silicon atom are present in one molecule, and the viscosity at 25 ° C. is 50 to 100,00.
100 parts by weight of 0 cp polyorganosiloxane (B) Polyorganohydrogensiloxane having at least 3 hydrogen atoms bonded to silicon atoms in one molecule, the number of hydrogen atoms bonded to silicon atoms is contained in component (A) An amount of 0.5 to 4.0 per 1 alkenyl group (C) a catalyst selected from the group consisting of platinum and platinum compounds,
Amount of platinum atom as 0.1 to 100 ppm with respect to component weight (A) (D) Average particle size of 5 to 20 μm and particle size distribution of 5
100 to 800 parts by weight of a thermally conductive filler containing 20% or more of particles each having a particle size of less than 10 μm and 10 μm or more, respectively, and (E) an organosilicon compound-based adhesion aid having the following functional groups in the molecule 0.001 -10 parts by weight Si-H bond and epoxy group Si-H bond and alkoxy group A thermally conductive silicone composition comprising a vinyl group, an epoxy group, an alkoxy group, an allyl group, an alkoxy group, a (meth) acryloxy group and an alkoxy group.

The polyorganosiloxane as the component (A) constituting the composition of the present invention has at least two alkenyl groups directly bonded to silicon atoms in one molecule and may be linear or branched. A mixture of these may be used. Examples of the alkenyl group include a vinyl group, an allyl group, a 1-butenyl group, a 1-hexenyl group, and the like, and the vinyl group is most advantageous from the viewpoint of easy synthesis. Examples of the residual organic group bonded to the silicon atom include an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, and a dodecyl group, an aryl group such as a phenyl group, a 2-phenylethyl group, and a 2-phenylpropenyl group. Examples thereof include an aralkyl group such as an alkyl group, and further examples include a substituted hydrocarbon group such as a chloromethyl group and a 3,3,3-trifluoropropyl group. Of these, a methyl group is most preferred because it is easy to synthesize and has a degree of polymerization of polyorganosiloxane necessary for maintaining good physical properties after curing, while maintaining a low viscosity before curing. . The alkenyl group bonded to the silicon atom may be present either at the terminal of the molecular chain of the polyorganosiloxane, in the middle thereof, or at both of them, but it does not give the cured composition excellent mechanical properties. In order to give it, it is preferable to exist at least at the terminal. The viscosity of this polyorganosiloxane (A) at 25 ° C. is 10 to 100,000 cP, and more preferably 50 to 10,000 cP. If the viscosity is too low, the filler of the composition will be separated immediately, and if the viscosity is too high, the necessary thermal conductivity cannot be obtained because the amount of the filler that can be blended is limited.

The polyorganohydrogensiloxane of the component (B) constituting the composition of the present invention needs to have at least three hydrogen atoms bonded to silicon atoms in order to reticulate the composition by crosslinking. is there. Examples of the residual organic group bonded to the silicon atom include the same groups as those in the above-mentioned component (A), but a methyl group is most preferable because of ease of synthesis. Further, an alkenyl group may be present. Such polyorganohydrogensiloxane may be linear, branched or cyclic, or may be a mixture thereof. The blending amount of the component (B) is based on one alkenyl group in the component (A).
(B) The hydrogen atom bonded to the silicon atom in the component is 0.5 to
The amount is 4.0, preferably 1.0 to 3.0. Within such a preferable range, the curing of the composition is sufficiently advanced, the hardness of the composition after curing is increased, and the physical properties and heat resistance of the composition after curing are improved. .

The catalyst selected from the component (C) platinum and the platinum compound constituting the composition of the present invention promotes the addition reaction between the alkenyl group of the component (A) and the hydrosilyl group of the component (B). It is an ingredient. Examples of the component (C) include simple substance of platinum, chloroplatinic acid, platinum-olefin complex, platinum-
Examples thereof include alcohol complexes and platinum coordination compounds.
The blending amount of component (C) is platinum atom based on the weight of component (A).
It is in the range of 0.1 to 100 ppm. If it is less than 0.1 ppm, it has no effect as a catalyst, and if it exceeds 100 ppm, no particular improvement in the curing rate can be expected.

The component (D) which constitutes the composition of the present invention is a filler for imparting thermal conductivity to the composition. Such fillers include metal powders such as aluminum powder, copper powder and nickel powder; metal oxides such as alumina, magnesium oxide, beryllium oxide, chromium oxide and titanium oxide; silicon nitride, boron nitride, boron carbide, titanium. Examples thereof include ceramics such as carbide, silicon carbide, and aluminum nitride. Particularly when electrical insulation is required, metal oxides or ceramics are preferable, and alumina and silicon nitride are particularly preferable from the viewpoint of heat dissipation effect. The characteristic of the present invention is that the average particle diameter of the heat conductive filler is 5 to 20 μm.
It is to be. If the average particle size is less than 5 μm, it cannot be blended so as to give the heat radiation effect required when the composition is filled, and if the average particle size exceeds 20 μm, the reinforcing effect is small and the heat radiation effect is not good.

Further preferred in the present invention is that the particle size distribution of the filler is not monodisperse but has a broad particle size distribution. That is, even in the above-mentioned average particle size, a mixture of a fine particle and a relatively coarse particle is easily filled into the system, the thermal conductivity is high, and the viscosity of the composition is easy to maintain an appropriate value. Therefore, it is more preferable that particles having a particle size distribution of 5 μm or less and particles having a particle size of 10 μm or more are present in an amount of 20% or more. In the case of alumina, for example, such a filler having a wide particle size distribution and an average particle size of 5 to 20 μm is selected.
A monodisperse particle having a particle size of not more than μm and an average particle size of not less than 20 μm may be blended and used. The amount of component (D) is the same as component (A)
100 to 800 parts by weight based on 100 parts by weight. If it is less than 100 parts by weight, the thermal conductivity is not sufficient, and if it exceeds 800 parts by weight, it cannot be added to the system to exhibit fluidity.

When the composition (E) of the present invention is used for the purpose of adhering and fixing the composition of the present invention to the heating element and the radiation fin, it is essential to be added for the purpose of enhancing its adhesiveness. Is a component of. Examples of adhesion promoters for silicone rubber that cure by the addition reaction of component (E) include, for example, Japanese Patent Publication No.
-36255, Japanese Patent Publication No. 50-3460, Japanese Patent Publication No. 53-13508
JP, JP-B-56-39783, JP-A-48-16952, JP-A-50-124953, JP-A-52-22051,
JP-A-52-126455, JP-A-53-144960, JP-A-54-37157, JP-A-54-80358 and JP-A-
The one disclosed in Japanese Patent Publication No. 54-91559 is used. Specifically, silane derivatives and siloxane derivatives having the following functional groups in the molecule are preferable. Si-H bond and epoxy group Si-H bond and alkoxy group Vinyl group, epoxy group, alkoxy group Allyl group and alkoxy group (meth) acryloxy group and alkoxy group The following compounds are listed as compounds with these functional groups. To be However, in the following formula, Me represents a methyl group.

[0011]

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[0012]

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In this case, the blending amount of the component (E) is 1
0.001 to 10 parts by weight, preferably 0.1 to 10 parts by weight
5 parts by weight. If the amount is too small, the adhesion is not sufficiently imparted, and if the amount is too large, the properties of the rubber are adversely affected.

In addition to the above-mentioned components (A) to (E), a reinforcing filler may be added to the composition of the present invention if necessary. As the filler, fumed silica, hydrophobized sedimentation silica, fused silica, fine quartz powder, diatomaceous earth, fused talc,
Examples thereof include talc, glass fiber, graphite, carbon and pigment. The amount of this filler is not preferable to be added in a large amount because the viscosity increase due to the filler of (D) is large, and is 30 parts by weight or less relative to 100 parts by weight of the component (A).

The composition of the present invention can be obtained by mixing the above-mentioned components (A) to (E), which comprises (A), (B) and
Component (C) reacts and cures at room temperature when mixed, so store one of the components (A), (B), and (C) before using it. It is necessary to prevent the curing reaction by mixing or using a known stabilizer in the composition.

[0016]

The composition of the present invention thus obtained is used for heat dissipation adhesion between a ceramic substrate such as a regulator and an igniter and heat dissipation fins, heat dissipation adhesion between power transistors and heat dissipation fins, and printer dot heads and heat dissipation fins. Used for heat dissipation bonding. As described above, the heat-conductive silicone composition of the present invention has a high heat conductivity, and therefore can efficiently transfer the heat from the heat source to the heat radiation fin or the like. It is also very useful for increasing the amount of heat generated by powering up and integrating semiconductors and the like. Further, the composition having adhesiveness does not require screwing or the like, and is sufficiently useful for miniaturization of electric / electronic parts. Particularly, it is suitably used for electric / electronic parts for vehicles.

[0017]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the following, all "parts" represent "parts by weight" and all "%" represent "% by weight". First, the following components forming the composition of the present invention and the composition of the comparative example were prepared. Component (A); A-1: Both ends are blocked with dimethylvinylsilyl groups, 25 ° C
Viscosity of 1,000 cP in Polydimethylsiloxane A-2: Both ends blocked with dimethylvinylsilyl group, 25 ℃
Viscosity of 350 cP in polydimethylsiloxane

[0018]

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Component (C); C-1: Octanol solution of chloroplatinic acid, 2 as platinum atom
% Content (D) component; D-1: content of average particle size 3.5 μm, particle size 2-8 μm
85% monodisperse alumina D-2: average particle size 25μm, particle size 10 ~ 50μm content 90
% Monodisperse alumina D-3: average particle size 15 μm, content of particle size 5 μm or less 35
%, And the content of particles having a particle size of 10 μm or more is 35% and having a wide distribution of 35%.
%, And an alumina (E) component having a broad distribution of 30% with a particle size of 10 μm or more;

[0020]

[Chemical 4]

The components (A) to (E) were mixed as follows to obtain the composition of the present invention and the composition of the comparative example. That is, in the container (A)
The components were taken, the component (D) was added in the blending amount shown in Table 1, gradually heated and kneaded at 150 ° C. for 1 hour, and then heated and depressurized at 30 mmHg or less. This mixture was cooled to room temperature to obtain a base compound, and the components (B), (C) and (E) were added in the compounding amounts shown in Table 1 and mixed uniformly. The following evaluations were performed on this composition. Viscosity: Measured with a rotational viscometer (25 ℃) Thermal conductivity: Each composition was made into a sheet with a thickness of 2 mm 150
After heating to ℃ for 1 hour to make a rubber elastic body, return to 25 ℃,
Measured with Shotherm QTM-DII rapid thermal conductivity meter manufactured by Showa Denko. Shear adhesive strength: An Al plate and a polyphenylene sulfide (PPS) plate each having a thickness of 1 mm were prepared according to JIS C-2107. The results are shown in Table 1.

[0022]

[Table 1]

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[Procedure amendment]

[Submission date] December 26, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

Claims (1)

[Claims] 1. (A) 100 parts by weight of a polyorganosiloxane having at least two alkenyl groups bonded to silicon atoms in one molecule and having a viscosity at 25 ° C. of 50 to 100,000 cp (B) bonded to silicon atoms Polyorganohydrogensiloxane having at least 3 hydrogen atoms in one molecule, such that the number of hydrogen atoms bonded to silicon atom is 0.5 to 4.0 per 1 alkenyl group contained in the component (A). Amount (C) a catalyst selected from the group consisting of platinum and platinum compounds,
Amount of platinum atom as 0.1 to 100 ppm with respect to component weight (A) (D) Average particle size of 5 to 20 μm and particle size distribution of 5
100 to 800 parts by weight of a thermally conductive filler containing 20% or more of particles each having a particle size of less than 10 μm and 10 μm or more, respectively, and (E) an organosilicon compound-based adhesion aid having the following functional groups in the molecule 0.001 ~ 10 parts by weight Si-H bond and epoxy group Si-H bond and alkoxy group Vinyl group, epoxy group, alkoxy group Allyl group and alkoxy group A thermally conductive silicone composition consisting of (meth) acryloxy group and alkoxy group.