JP2002363412A - Heat conductive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat conductive composition having good heat conductivity and good operating efficiency and detachability. SOLUTION: This heat conductive composition is characterized by comprising (A) an organopolysiloxane having 20-1,000,000 cP viscosity at 25 deg.C and molecular chain terminals blocked with hydroxy groups, (B) a mixture of an organosilicon compound having 2 amide groups or aminooxy groups in one molecule with an organosilicon compound having >=3 amide groups or aminooxy groups in one molecule, (C) one or more kinds of components selected from the group of an organic compound having one functional group selected from hydroxy group, oxime group, mercapto group and amino group, an alkoxy group- containing organosilicon compound and an organosilicon compound having one amide group or one aminooxy group bound to the silicon atom in one molecule and curing only the surface in contact with the air into a rubberlike elastic body and maintaining the interior in an uncured or a semicured state and (D) a heat conductive filler. The heat conductive composition is further characterized by having mastic curability with moisture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermally conductive composition capable of efficiently conducting heat to a component that generates heat.

[0002]

2. Description of the Related Art Heat-generating electronic components, such as transistors and thyristors, used in electronic equipment generate heat during use and must be removed. Conventionally, heat is diffused by attaching a radiating fin such as copper or aluminum or a metal plate to these components, and the heat is removed from the components. The radiating fins and metal plates (hereinafter collectively referred to as radiating components) are solid, and even if they are brought into close contact with electronic components such as transistors, fine gaps are created.
Thermal conductivity was improved.

In recent years, with the miniaturization, high integration, and high output of electric / electronic devices, the amount of heat generated per unit area of mounted components has become extremely large, and the heat may damage the components themselves or cause malfunctions. there's a possibility that. Further, since heat is also transmitted to electronic components in the vicinity of the electronic components, malfunctions and the like may be caused such as adverse effects on operation and performance. Therefore, heat dissipation is required to be improved more than before, and heat conduction sheets, heat radiation adhesives, heat radiation silicone grease, etc., which have high adhesion for the purpose of improving the heat conductivity between the heat-generating component and the heat radiation member, are required. Highly efficient ones have been devised.

[0004] For example, an ultra-highly integrated computing chip such as a CPU is used inside a personal computer, and the amount of heat generated from these chips is extremely large. When heat-dissipating silicone grease is used for such heat-generating components, the amount of heat generated is large,
The grease component evaporates or the grease oil and the conductive filler component are separated. Evaporated components can adversely affect electronic components, especially contacts,
Not preferred. Further, when the components are separated, not only is the heat conduction performance lowered, but also the grease oil drips and flows, contaminating the surroundings, which is not preferable.

Further, when a heat radiation adhesive is used, it does not evaporate or leak components due to its curability, but it is difficult to remove the adhered material when repairing, inspecting, or replacing parts. Yes, requires labor and skill.

The use of a molded heat-radiating sheet eliminates the drawbacks such as outflow of components and removability, but lacks adhesion between the two because it pushes against solids. In addition, since the sheet is sheet-shaped, the thickness is large, and the sheet lacks fundamental performance that thermal conductivity is not good.

Therefore, Japanese Patent Application Laid-Open Nos. 63-119554 and 1-228848 disclose an uncured heat conductive compound layer between a heat-generating component and a heat radiating member, and a heat-generating component located around the uncured compound. A package heat dissipation structure provided with a rubber layer for bonding members has been proposed. According to this method, the bonded portion is only the peripheral portion, so it is excellent in detachability, and most of the space between the heat generating component and the heat radiating member is an uncured compound, so that the thermal conductivity is good, Since the surrounding rubber layer covers the uncured portion, there is an advantage that the uncured compound does not flow out.

[0008]

However, the method disclosed in the above publication does not describe a specific method for forming an uncured compound portion and a rubber layer. Usually this is first formed by
Apply the uncured compound to the center of the heat dissipating member and adhere molding rubber around it with an adhesive to press it against the heat-generating component, or apply the uncured compound and then cure around to form a rubber. A method of applying a curable material and compressing it.

In the former method, since the rubber layer is a molded product, it is not easy to position the rubber layer around the heat radiating member.
In some cases, the position may be shifted when pressure-bonded to the heat-generating member, resulting in poor workability. Automatic line travel by robots is an extremely difficult task.

The latter method involves only the step of applying two kinds of liquid materials to the corresponding places, so that the operation is not so difficult and can be automated. For example, the amount of application of the uncured compound at the center is reduced. If the amount is too large, the surrounding curable rubber component may be washed away when the heat radiating member and the heat-generating component are pressed, and the desired performance may not be obtained. It is not easy to completely cover the rubber layer with this balance because it is necessary to keep the application amount and the pressing force constant.

[0011]

The present invention has been intensively studied in order to solve the drawbacks of these conventional heat conductive compositions. That is, (A) the viscosity at 25 ° C. is 20 to 1,000,000 centipoise, organopolysiloxane 100 having a molecular chain terminal blocked with a hydroxyl group
Parts by weight, (B) an organic silicon compound having two amide groups or aminoxy groups as a functional group in one molecule, and an organic silicon compound having three or more amide groups or aminoxy groups as a functional group in one molecule Mixture with compound 0.5-30
Parts by weight, (C) an organic compound having one functional group selected from a hydroxy group, an oxime group, a mercapto group and an amino group, an organosilicon compound containing an alkoxy group, and an amide bonded to a silicon atom in one molecule Selected from the group of organosilicon compounds having one group or aminoxy group,
Only the surface which is in contact with the atmosphere is cured into a rubber-like elastic material, and the interior is maintained in an uncured or semi-cured state. An object of the present invention is to provide a thermally conductive composition characterized by having mastic curability by moisture of up to 1200 parts by weight.

Hereinafter, the present invention will be described in detail. The heat conductive composition used in the present invention has a storage stability under the protection from moisture, and when cured by moisture in the atmosphere, the surface is cured into a rubber elastic body or a plastic, and the inside is partially cured or semi-cured. It has the property of maintaining a cured state (this state is referred to as mastic curability). A curing inhibitor is added to a normal deamid-curable or deaminoxy-curable silicone composition to partially cure the composition. It is a surface-curable silicone sealing material composition that has been inhibited.

The component (A) preferably used in the present invention serves as a base material of the present composition, and has the general formula HO (R ² S
iO) _n H (wherein R is the same or different, substituted or unsubstituted monovalent hydrocarbon group, and n is 20 to 10,000 at 25 ° C.)
Α, ω-
Dihydroxy-diorganopolysiloxanes are preferably used. Examples of R include an alkyl group such as a methyl group and an ethyl group, an alkenyl group such as a vinyl group and an allyl group, an aryl group such as a phenyl group, and a halogenated hydrocarbon group. It is preferable that 70 mol% or more is a methyl group.

Among the components (B) preferably used in the present invention, the organosilicon compound having two amide groups or aminoxy groups as a functional group in one molecule can be used as the component (A) in the presence of moisture at room temperature. By reacting with and extending the chain,
The organosilicon compound which imparts a low modulus and high elongation to the cured product and has at least three amide groups or aminoxy groups as functional groups in the other molecule reacts with the component (A) to react with the component (A). It is a curing agent for crosslinking and curing. As the amide group, an N-methylacetamide group, N
-Ethylacetamide group, N-phenylacetamide group and the like. Examples of the aminoxy group include N, N-diethylaminoxy group, N, N-methylethylaminoxy group,
Examples thereof include an N, N-dipropylaminoxy group and an N, N-diphenylaminoxy group. These organosilicon compounds having a functional group may be any of silane, linear polysiloxane and cyclic polysiloxane.

If the amount of the component (B) is too small, the hardening of the surface will not occur, or the storage stability in one package will be poor, and if it is too large, the curability will be poor.
The amount is 0.5 to 30 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the organopolysiloxane as the component (A) because it is economically disadvantageous.

The component (C) preferably used in the present invention is an important component for imparting masticity,
When the component (C) is not added, the rubber crosslinks and cures to form a rubber elastic body. However, when the component (C) is added, only the surface that comes into contact with the atmosphere hardens to a rubber elastic body, Maintains an uncured or semi-cured state. As the component (C), alcohol compounds such as methyl alcohol, ethyl alcohol, and propyl alcohol; oxime compounds such as methyl ethyl ketoxime and diethyl ketoxime; marcapto compounds such as isopropyl mercaptan and butyl mercaptan; amine compounds such as butyl amine and octyl amine; formula ^{_{[R 1] a [R 2}} O] b SiO
_{4-ab / 2} (wherein, R ¹ represents a hydrogen atom or a monovalent hydrocarbon group, R ² represents an alkyl group, and a represents 0 ≦ a <4, b
Is 0.01 ≦ b ≦ 4, where a + b is 1.5 ≦ a + b ≦
4), an organosilicon compound containing an alkoxy group such as methyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, or an amide group or an aminooxy group bonded to a silicon atom in one molecule. And an organic silicon compound (an amide group and an aminoxy group are the same as described above). The addition amount of the component (C) varies depending on the molecular weight of the component (A), the molecular weight and the addition amount of the component (B), the molecular weight of the component (C), the activity, and the like.
Usually, 0.01 to 15 parts by weight per 100 parts by weight of component (A)
It can be used in the range of parts by weight, preferably 0.02 to 10
It is in the range of parts by weight. When the amount of the component (C) is small,
This is because masticity cannot be obtained, the rubber-like elastic material is obtained, and if the amount is too large, the surface is not cured. The component (C) may be used alone or as a mixture of two or more.

The degree of mastic curability of the present invention is preferably such that the cured film thickness per month in an atmosphere at a temperature of 20 ° C. and a relative humidity of 60% is 0.5 to 2 mm. After one month, the curing does not proceed and the inside must be kept uncured.

As the heat conductive filler used in the component (D) used in the present invention, known fillers can be used. For example, aluminum hydroxide, magnesium hydroxide,
Calcium carbonate, magnesium carbonate, calcium silicate,
Inorganic oxides such as magnesium silicate, calcium oxide, magnesium oxide, alumina powder, silica, etc., nitrogen inorganic compounds such as aluminum nitride, boron nitride and silicon nitride, organic substances such as carbon, graphite, silicon carbide, silver, copper, aluminum etc. Metal powder is preferably used. These are 1
It is possible to use a combination of two or more species.

The heat conductive filler is spherical, powdery, fibrous,
Any shape such as a needle shape and a scale shape may be used, and the average particle size is about 1 to 100 μm.

The amount of the heat conductive filler used varies depending on the shape and type of the filler used, but is 20 to 1200 parts by weight based on the total amount of the components (A) to (C). When the amount is less than 20 parts by weight, the heat conduction performance is not sufficient.

The heat conductive composition of the present invention comprises the above essential components. If necessary, a fine powder inorganic filler may be added in order to improve the flow characteristics before curing. For example, fumed silica, quartz fine powder, calcium carbonate, fumed titanium dioxide, diatomaceous earth, aluminum hydroxide, particulate alumina, magnesia, zinc oxide, zinc carbonate, and silanes, silazanes, and low-polymerization degree siloxane , Organic compounds and the like which have been surface-treated.

Further, an organic solvent, a fungicide, a flame retardant, a plasticizer, a thixotropy-imparting agent, an adhesion-imparting agent, a curing accelerator, a pigment, and the like can be added to the heat-conductive composition of the present invention. For example, examples of the plasticizer include hydrocarbon compounds such as polybutene, hydrogenated polybutene, liquid polybutadiene, hydrogenated polybutadiene, paraffin oil and naphthenic oil, chlorinated paraffins, phthalates such as dibutyl phthalate and di (2-ethylhexyl) phthalate. Examples thereof include non-aromatic dibasic acid esters such as acid esters, dioctyl adipate and dioctyl sebacate, esters of polyalkylene glycol, and phosphoric esters such as tricresyl phosphate.

The heat conductive composition of the present invention can be used for a CPU or an MPU.
It is applied to arithmetic circuits, such as, and heat-generating components such as transistors and thyristors, and is used between heat-dissipating members such as heat-dissipating fins and Peltier elements. The method of use will be described with reference to FIG. FIG. 1 shows a case in which it is used between a CPU and a radiation fin. Reference numeral 4 denotes a CPU mounted on the substrate 6, and reference numeral 5 denotes a radiation fin. The heat conductive composition 1 is uniformly applied to the side of the heat radiation fin 5 that comes into contact with the CPU, and is immediately attached to the CPU 4. The heat conductive composition 1 is cured using a metal fitting for fixing the radiation fins 5 or a jig for temporary fixing (not shown). The end 2 of the thermally conductive composition 1 is cured by moisture in the air. However, since the present composition is mastic curable, the inside 3 does not solidify from the end 2 and maintains a liquid or soft gel state. Further, the end portion 2 is solidified to be in a rubber state, and has a function of fixing the radiation fin by bonding to the radiation fin 5 and the CPU 4. Further, the liquid material in the inside 3 does not leak.
Even if a part of the end portion 4 is broken by an impact or the like, moisture in the air permeates from the broken portion from the broken portion to harden the thermoconductive composition 1 slightly inside the broken portion. The end is in a hardened state.

Further, the CPU is used for maintenance and repair.
When it becomes necessary to remove the radiation fins 5 from 4,
The CPU 4 and the radiation fins 5 can be removed by cutting the entire periphery of the end 2 with a knife or a cutter. Since the internal uncured portion 3 is not adhered, it can be removed by removing it after removing it by wiping it with an organic solvent or a surfactant.

[0025]

EXAMPLES The compositions of Examples 1 to 6 and Comparative Examples 1 and 2 were prepared with the compositions shown in Table 1. The components used in Table 1 are as follows. As other components, component (A): A: α, ω-dihydroxydimethylsiloxane having a viscosity of 15,000 centipoise at 25 ° C., A2: α, ω-dihydroxydimethyl having a viscosity of 5,000 centipoise at 25 ° C. Polysiloxane (B) component: B1: dimethylbis (N-ethylacetamido) silane, B2: compound represented by the following structural formula

Embedded image

B3: Compound represented by the following structural formula

Embedded image

Component (C): C1: methyltrimethoxysilane, C2: iso-propyl alcohol, C3: methyl ethyl ketoxime, C4: n-butyl mercaptan, C5 trimethylbis (N-ethylacetamido) silane (D) Component: D1: thermal conductive filler aluminum oxide

A thermal conductivity test was performed using the composition obtained above. 3 g of each composition was applied to the center of a 5 × 5 cm flat heater, and an aluminum heat sink (radiation fin) was pressed against the flat heater. The heat conductive composition was cured by fixing it with a temporary fixing jig for 24 hours. Air cooling fan (DC made by Alpha Co., Ltd.)
PicoAce25) was attached. 60 for flat heater
The heater was heated by applying electric power of W, and the surface temperature of the heater and the temperature of the heat sink were measured to calculate the thermal resistance ° C / W of the entire apparatus. The results are shown in Table 1.

Further, each composition of xxg was applied to the center of a 5 × 5 cm aluminum plate, and the aluminum plates were pressed together. This was left under an atmosphere of 25 ° C and 40 ° C for 3 months.
After the standing, a test was performed to determine whether or not the opening was formed by prying open with a flathead screwdriver. Those that could not be pryed open with a flathead screwdriver were pryed with a knife into the joint surface to cut open the cured product. Further, the internal curability was confirmed. The internal curability was evaluated as ○ when the composition could be removed by wiping with a solvent, Δ when the composition could be further removed with a scraper, and × when the composition could not be removed with a scraper.

[0030]

[Table 1]

[0031]

As described above, the thermally conductive composition of the present invention is mastic cured, so that separation and elution of uncured components are suppressed, and since it is not a solid, it has excellent thermal conductivity. Further, repair, replacement, and the like can be easily performed.

[0032]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example to which a heat conductive composition of the present invention is applied.

[Explanation of symbols]

1: heat conductive composition, 2: cured part at end, 3: uncured part inside, 4: heat-generating component, 5: heat dissipation member

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 CP031 CP092 DA027 DA037 DA077 DA097 DE077 DE087 DE147 DE237 DF017 DJ007 DJ017 EC036 EN026 ES016 EV026 EX036 GQ00

Claims (2)

[Claims] (A) A viscosity at 25 ° C. of 20 to 100.
100 parts by weight of an organopolysiloxane having a molecular chain terminal of 0000 centipoise and capped with a hydroxyl group. (B) An organic silicon compound having two amide groups or aminoxy groups as functional groups in one molecule; A mixture with an organic silicon compound having three or more amide groups or aminoxy groups as functional groups 0.5 to 30 parts by weight (C) A functional group selected from a hydroxy group, an oxime group, a mercapto group and an amino group Selected from the group consisting of organic compounds having an organic group, organosilicon compounds containing an alkoxy group, and organic silicon compounds having one amide group or aminoxy group bonded to a silicon atom in one molecule, and only those surfaces that come into contact with the atmosphere. Is one or more components that cure to a rubber-like elastic body and maintain an uncured or semi-cured state inside 0.01 to 15 wt. (D) a thermally conductive filler (A) ~ thermally conductive composition, characterized in that it comprises a mastic curable by moisture consisting of from 20 to 1,200 parts by weight with respect to the total amount of (C). 2. A film having a mastic curability of 0.5 to 2 m per month in an atmosphere at a temperature of 20 ° C. and a relative humidity of 60%.
The thermally conductive composition according to claim 1, wherein m is m.