JP2992285B1 - Thermal conductive material - Google Patents

Abstract

An object of the present invention is to provide a heat conductive material having a high heat conductivity and excellent flexibility, and a heat conductive material which does not cause electric contact failure. SOLUTION: The heat conductive material of the present invention is obtained by adding a hydrate of a metal compound as a heat conductive filler to a synthetic resin material serving as a base material and mixing the same. The thermally conductive filler is
Aluminum hydroxide, magnesium hydroxide, zinc hydroxide, calcium hydroxide, tin hydroxide, and other metal hydrates. The base material is a synthetic rubber or the like, and EPDM, butyl rubber, chloroprene rubber, acrylic rubber, nitrile rubber, fluorine rubber, chlorosulfonated polyethylene rubber, styrene-butadiene rubber, and the like are preferable. Oil may be added to increase flexibility. Oils include process oil, liquid paraffin, fatty oil, chlorinated paraffin, ester plasticizer, liquid rubber,
Liquid butadiene, hydrocarbon-based synthetic lubricating oils and the like are preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat conducting material which is disposed so as to be in contact with a heating element for promoting heat radiation from a heating element such as an electronic component.

[0002]

2. Description of the Related Art Conventionally, a heat conductive material obtained by dispersing a heat conductive filler in a base material of silicone (organopolysiloxane) has been used. This kind of heat conductive material is interposed, for example, between an electronic component serving as a heat source and a component serving as a heat sink (hereinafter simply referred to as a heat sink) such as a heat sink or a housing panel inside the electric / electronic device. The heat generated by the electronic component is released to the heat sink through the heat conductive material.

[0003]

However, when the content of the heat conductive filler is increased in order to enhance the thermal conductivity, the flexibility of the conventional heat conductive material is reduced, and the heat conductive material adheres to electronic parts and heat sinks. Therefore, the thermal conductivity cannot be improved as much as expected because the contact property decreases and the substantial contact area decreases.

Here, in order to simply increase the flexibility, in the case of a general resin material, a means such as addition of a foaming agent can be adopted. However, in the case of a heat conductive material, if there are too many bubbles, a heat insulating effect may appear.Especially, even if an attempt is made to add a foaming agent within a range that does not cause a decrease in heat conductivity. However, it is difficult to adjust the amount, timing and method of addition, because a region having a low density of the thermally conductive filler may be formed in spite of a high density of the bubbles formed by the foaming agent. There was a problem of determining.

[0005] Further, the silicone rubber contains some silicone oligomers (low polymers such as dimers and trimers) in addition to the silicone polymer as a main component. Therefore, when this silicone oligomer volatilizes and approaches an electric contact portion such as a motor or a relay, it receives electric energy from the electric contact portion and may change into an insulator such as siloxane. There is a possibility that electrical contact failures such as an increase in contact resistance and contact failure may be caused due to accumulation on the contact portion.

The present invention has been made to solve the above-mentioned problems, and a first object of the present invention is to provide a heat conductive material having high heat conductivity and excellent flexibility. A second object is to provide a heat conductive material which does not cause an electrical contact failure.

[0007]

Means for Solving the Problems and Effects of the Invention The heat conductive material of the present invention, which has been made to achieve the first object, is used as a heat conductive filler in a synthetic resin material as a base material. And a hydrate of a metal compound which releases water vapor with heating is added and mixed.

[0008] In the heat conductive material of the present invention, the heat conductive filler is added to improve the thermal conductivity of the substrate, and is a powder or fine particles that can be uniformly dispersed in the substrate. Shape. However, when it is added to and mixed with the synthetic resin material serving as the base material, it is not necessary to mix the powder in the form of powder or fine particles, but for example, after mixing with an appropriate liquid.

[0009] In the thermally conductive material of the present invention, with the heating
When the hydrate of the metal compound that releases water vapor is added and mixed as the heat conductive filler, when the hydrate of the metal compound is heated by heat at the time of forming the heat conductive material, Individual particles of the thermally conductive filler generate a small amount of water vapor, which forms a myriad of air bubbles in the substrate. This bubble is about 20 to 20
It is extremely fine, about 50 μm.

The presence of such bubbles not only makes it easier for the base material itself to expand and contract due to the collapse of the bubbles, but also, unlike the case where a foaming agent is simply added, the bubbles are formed of the heat conductive filler. It is formed at a position adjacent to each particle or at a position surrounding the particles. Therefore, relative displacement between the particles of the thermally conductive filler or between the thermally conductive filler and the base material can easily occur,
As a result, the flexibility of the heat conductive material as a whole becomes extremely high.

Further, since the amount of water vapor corresponding to the particle size is generated from the heat conductive filler, bubbles having a size corresponding to the particle size are formed in a number corresponding to the number of particles. Therefore, unlike the case where the foaming agent is simply added, excessively large bubbles are not formed in an excessively large amount.In particular, a region where only the density of the bubbles is high and the density of the thermally conductive filler is low is formed. Therefore, sufficiently excellent thermal conductivity suitable for use as a thermal conductive material is ensured.

Therefore, according to the heat conductive material of the present invention,
Even if the content of the thermally conductive filler is increased to increase the thermal conductivity, the flexibility does not decrease as compared with the conventional product, and the adhesion to the electronic component and the heat sink does not decrease. The thermal conductivity can be effectively improved without decreasing. Specific hardness and thermal conductivity vary depending on various conditions and cannot be specified unconditionally. However, in the range confirmed experimentally, for example, the hardness is about JIS A20 to A80, particularly JIS A
Those having a thermal conductivity of less than 40 can be manufactured, and the thermal conductivity is at least 0.3 W / (m · K) or more, and in many cases,
It can be about 0.6 W / (m · K) or more, and in particular, one having a high thermal conductivity exceeding 0.8 W / (m · K) can be obtained.

Also, bubbles can be formed by adding a thermally conductive filler without using a foaming agent. In particular, even if the amount, timing and method of addition are not strictly selected,
Since an appropriate amount of air bubbles can be formed at a density corresponding to the density of the heat conductive filler, flexibility can be easily provided while ensuring high heat conductivity. If it is desired to further increase the flexibility, it is optional to add some foaming agent within a range where the necessary thermal conductivity is ensured. Even in such a case, the same degree of flexibility can be obtained by simply using the foaming agent alone. , The thermal conductivity is higher than in the case where

In addition, this kind of heat conductive material is often used sandwiched between a heating element and a heat sink. In such a case, the heat conductive material is compressed, so Distortion occurs, but if there are bubbles inside the heat conductive material, the heat inside the bubbles will expand due to the heat transmitted from the heating element, and the pressure will eliminate the distortion and increase the adhesion to the heating element and heat sink. Which also contributes to a reduction in thermal resistance.

Further, if countless air bubbles are formed inside the heat conductive material, the functions as a vibration damping / vibration-proof material and a cushioning material are also enhanced, and a good performance as a sound absorbing material is exhibited. By surrounding a noise source such as a motor with this heat conductive material, noise can be suppressed while radiating heat.

In addition, when a hydrate of a metal compound is added and mixed as a heat conductive filler, there is also an effect that the flame retardancy of the heat conductive material becomes extremely high. Therefore, in particular,
The present invention can be applied to a high-pitched portion or a portion where there is a risk of ignition. By the way, in the present invention, as the hydrate of the metal compound, for example, as described in claim 2,
It is desirable to use one or a mixture of two or more selected from aluminum hydroxide, magnesium hydroxide, zinc hydroxide, calcium hydroxide, and tin hydroxide. Since these compounds release water vapor upon heating, they have an expected bubble-forming effect, and have relatively high thermal conductivity, so that they have satisfactory performance as a thermally conductive filler. However, the present invention is characterized in that bubbles are formed by water vapor released from the hydrate, and the hydrate also functions as a heat conductive filler. It is also possible to employ the compound of (1) as a thermally conductive filler, for example, a hydrate of a metal oxide, or a hydrate of a metal compound other than the metal oxide.

Further, the shape of the heat conductive material is not particularly limited, and can be used by appropriately processing into a form corresponding to the application location. For example, in order to increase the versatility, the heat conductive material may be formed into a block shape, a sheet shape, or the like, and cut and cut into a desired shape according to the application location when used, so that the material can be used. Good. Alternatively, it may be formed in a mold having a shape corresponding to the application location, and may be used as it is. When arranging the heat conductive material, the heat conductive material may be stuck with an appropriate adhesive or double-sided tape, may be sandwiched between two components, or may be simply installed depending on a place. When affixing with an adhesive or a double-sided tape, these adhesives or the double-sided tape may be previously adhered to the heat conductive material, and if such a heat conductive material is used, a release sheet covering the adhesive surface Just peel off
The heat conductive material can be easily attached to a desired location.

Next, in order to achieve the second object in addition to the first object, the heat conductive material according to claim 3 is used as the base material in a weight ratio of 1 to 30% with respect to the whole. % Of synthetic rubber, 45 to 65% by weight of the total weight of the metal compound as the heat conductive filler, and 10 to 50% of the total weight of the metal compound as a softener. % Oil.

Unlike the heat conductive material having silicone rubber as a base material, the heat conductive material thus constituted employs synthetic rubber as a base material, so that silicone oligomers are volatilized from the base material. There is no. Therefore, even if it is arranged near an electric or electronic component having an electric contact such as a motor or a relay, there is no possibility of causing an electric contact failure due to the silicone oligomer.

Therefore, for example, if it is used for heat dissipation measures of a magnetic disk device or an optical disk device, there is an advantage that the motor for driving the disk is not adversely affected. In addition, as described above, this heat conductive material
Since it can be used as a vibration-proof material or as a cushioning material, for example, if components such as a motor that become a vibration source are held down by this heat conductive material, heat can be radiated while avoiding contact failures, and At the same time, the vibration can be suppressed, so that the manufacturing cost can be suppressed and the size of the device can be reduced as compared with the case where the heat conductive material and the vibration isolating material are separately applied.

The synthetic rubber used in the heat conductive material according to claim 3 is a component serving as a base material of the heat conductive material, and is, for example, EPDM, butyl rubber, chloroprene rubber, acrylic rubber, nitrile rubber, fluorine rubber. It is desirable to use chlorosulfonated polyethylene rubber or styrene-butadiene rubber. The content of synthetic rubber is 1 to
It is preferable to adjust the amount within the range of 30% by weight.
It may be adjusted to 20% by weight, more preferably about 8 to 14% by weight. If the content is less than 1% by weight, it becomes difficult to maintain the strength required for the substrate. On the other hand, when the content of the synthetic rubber exceeds 30% by weight, it becomes difficult to secure a sufficiently satisfactory thermal conductivity, and the hardness tends to increase.

Further, among the above various synthetic rubbers, it is desirable to use EPDM as described in claim 4. E
PDM is a terpolymer containing ethylene, propylene and a small amount of a diene monomer as constituent units.
When M is used, the strength is easily maintained even when the content of the thermally conductive filler is increased, the flexibility is easily increased by adding a softening agent or the like, the heat resistance temperature can be increased, and the weather resistance can be improved. There is an excellent effect of being excellent.

Further, the oil is mainly added as a plasticizer or a softening agent for improving the flexibility of the synthetic rubber, and more specifically, as described in claim 5, a process oil, It is desirable to employ one or a mixture of two or more selected from liquid paraffin, fatty oil, chlorinated paraffin, ester plasticizer, liquid rubber, liquid butadiene, and hydrocarbon synthetic lubricating oil.

However, oils other than those described above may be used as long as the flexibility of the synthetic rubber can be improved. The content of the oil is usually adjusted within the range of 10 to 50% by weight, preferably within the range of 20 to 40% by weight. When the content is less than 10% by weight, the tendency that the flexibility is lowered and the adhesion to electronic parts and the like is deteriorated becomes remarkable. On the other hand, when the content of the oil exceeds 50% by weight, the oil tends to excessively ooze onto the surface of the heat conductive material, and the surface of the heat conductive material becomes sticky, which may cause a problem depending on the application.

However, depending on the use, the oil may be oozing on the surface as described in claim 6. Since such a heat conductive material has a sticky surface,
There is an effect that a heat conductive material can be stuck without using an adhesive or the like in a portion where the oozing of oil is not a problem.

The content of the heat conductive filler is usually 45 to 45.
It may be prepared in the range of 65% by weight, preferably in the range of 50 to 60% by weight. If the content is less than 45% by weight, the thermal conductivity will be low, and it will be difficult to obtain a sufficiently satisfactory performance as a thermal conductive material. On the other hand, when the content of the thermally conductive filler exceeds 65% by weight, the hardness increases and the material becomes hard, so that the tendency of insufficient strength and poor adhesion to electronic components and the like becomes remarkable.

The weight ratio of the synthetic rubber, oil, and heat conductive filler is the weight ratio to the entire heat conductive material. However, the heat conductive material does not need to be composed of only these components. As long as it does not impair the function of the heat conductive material of the present invention, apart from the above main components, further, various catalysts for adjusting the reaction rate, coloring agents such as pigments and dyes, or other stabilizers And additives and the like.

[0028]

Next, an embodiment of the present invention will be described with reference to an example. A heat conductive material was manufactured according to the procedure described below. A thermally conductive filler was added to synthetic rubber as a base material and kneaded with a kneader. In this embodiment,
EPDM was used as the synthetic rubber. Aluminum hydroxide was used as the thermal conductive filler.
As a kneading machine, a closed kneading machine such as a roll mill, a Banbury mixer, an intermix, and a pressure kneader,
A continuous kneader can be used. In addition, at the time of kneading, an oil serving as a plasticizer or a softener and a small amount of various additional components were added as other components. In the present embodiment, chlorinated paraffin is used as the oil. Further, as various additive components, for example, an activator, a processing aid, a release agent, a stabilizer, and the like can be added.

Thereafter, a vulcanizing agent and a vulcanization accelerator were further added and kneaded with a roll mill and a pressure kneader. At this time, if necessary, a foaming agent may be added. Next, vulcanization was performed by placing the rubber composition in a mold and raising the temperature to form a desired heat conductive material. The step of forming the heat conductive material may be a method used for the production of ordinary vulcanized rubber. In addition to the above, for example, after forming into an arbitrary shape using an extruder, heating in a vulcanization tank is performed. By performing vulcanization, the desired heat conductive material may be formed.

Next, the hardness of several kinds of heat conductive materials obtained by the above procedure was measured according to JIS 6301K (A hardness). The thermal conductivity of each thermal conductive material was measured using a rapid thermal conductivity meter (QTM-500, manufactured by Kyoto Electronics). Table 1 below shows the main components, hardness, and thermal conductivity of each heat conductive material.

[0031]

[Table 1]

As is clear from Table 1, each of the above-mentioned heat conductive materials has both high flexibility and high heat conductivity. In addition, the surface of the above-mentioned heat conductive material had oil oozed out and had some tackiness.

When the above-mentioned heat conductive material was observed with a microscope, it was found that bubbles of about 50 μm or less were formed around the heat conductive filler, and only the bubbles were present without the heat conductive filler. It turned out that such an area does not exist. Such fine air bubbles cause a decrease in the continuity of the heat conduction path. Therefore, if only the air bubbles are unevenly distributed, the heat insulating effect is likely to appear. Because of the presence of the heat conductive filler, the heat insulating effect of the air bubbles is reduced, which is presumed to be one of the causes of providing high heat conductivity. Also,
When there is a space due to bubbles around the heat conductive filler, when the heat conductive material is deformed, the space is crushed, or the heat conductive filler can be displaced in the space, so these have high flexibility It is presumed to be contributing.

In any case, according to each of the above-described heat conductive materials, not only the heat conductivity but also the adhesion to electronic parts and heat sinks is high. Can be encouraged. Also, unlike silicone rubber base materials, since silicone oligomers are not contained in the base material, there is a risk of causing electrical contact failures such as an increase in contact resistance and contact failure due to the volatilization of the silicone oligomer. Absent.

Although the embodiment of the present invention has been described above, various specific embodiments other than the above are conceivable for the embodiment of the present invention. For example, in the above embodiment, an example was shown in which aluminum hydroxide was used as the heat conductive filler, but a hydrate of a similar metal oxide or a hydrate of another metal compound was used as the heat conductive filler. More specifically, in addition to aluminum hydroxide, for example, magnesium hydroxide, zinc hydroxide, calcium hydroxide, tin hydroxide and the like can be used. These may be used singly or in combination of two or more without any problem.

In the above embodiment, the base material is E
Although PDM was used, other synthetic rubbers and other soft synthetic resin materials may be used. Specifically, butyl rubber, chloroprene rubber, acrylic rubber, nitrile rubber, fluorine rubber, chlorosulfonated polyethylene rubber, styrene-butadiene Rubber or the like can be used.

Further, in the above embodiment, chlorinated paraffin is used as the oil, but other softeners or plasticizers may be used. Specifically, process oil, liquid paraffin, fatty oil, Chlorinated paraffin, ester-based plasticizer, liquid rubber, liquid butadiene, hydrocarbon-based synthetic lubricating oil, and the like can be used. If chlorine-containing compounds such as chlorinated paraffins are not used, they are halogen-free and can reduce the possibility of generating harmful substances when disposed of, for example, by incineration. Good.

Claims (6)

(57) [Claims] 1. A heat conductive material, wherein a hydrate of a metal compound which releases water vapor with heating is added and mixed as a heat conductive filler into a synthetic resin material as a base material. 2. The method according to claim 1, wherein the hydrate of the metal compound is one or a mixture of two or more selected from aluminum hydroxide, magnesium hydroxide, zinc hydroxide, calcium hydroxide and tin hydroxide. The heat conductive material according to claim 1, wherein: 3. The base material according to claim 1, wherein the weight ratio to the whole is 1%.
-30% by weight of synthetic rubber, and as the heat conductive filler, a weight ratio of 4
5 to 65% by weight of a hydrate of the metal compound, and as a softener, 10 to 5% by weight based on the whole.
The heat conductive material according to claim 1, wherein the heat conductive material contains 0% by weight of oil. 4. The synthetic rubber according to claim 1, wherein the synthetic rubber is ethylene, propylene,
Ternary copolymer with a small amount of diene monomer as a structural unit
The heat conductive material according to claim 3, wherein the heat conductive material is EPDM that is united . 5. The oil according to claim 1, wherein the oil is one or two selected from process oil, liquid paraffin, fatty oil, chlorinated paraffin, ester plasticizer, liquid rubber, liquid butadiene, and hydrocarbon synthetic lubricating oil. The heat conductive material according to claim 3, wherein the heat conductive material is a mixture of two or more. 6. The heat conductive material according to claim 3, wherein said oil is oozing on the surface of the heat conductive material.