JPS60221481A - Orienting heat conductive member - Google Patents

Abstract

PURPOSE:An orienting heat conductive member, obtained by covering a bundle of carbon fibers, grown in the vapor-phase, and having a specific element fiber diameter and remarkably higher heat conductivity in the longitudinal direction than in the direction perpendicular thereto with a low heat conductive material, and having excellent heat conductivity in the axial direction. CONSTITUTION:An orienting heat conductive member obtained by covering a bundle of carbon fibers, grown in the vapor phase, prepared by thermal decomposition of a mixed gas of a hydrocarbon, e.g. benzene, and hydrogen gas in the presence of fine particles, e.g. Fe, at a temperature as high as about 1,000 deg.C by the vapor-phase method, and having 5-20mu, preferably 10+ or -3mu element fiber diameter and remarkably higher heat conductivity in the longitudinal direction than in the direction perpendicular thereto with a low heat conductive material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Object of the Invention) The present invention relates to an oriented thermally conductive member using vapor grown carbon fibers.

(Prior Art) Various methods have been studied to rapidly dissipate heat locally generated due to electrical or mechanical causes to the outside of the system, and some of them have been put into practical use, for example, by the Heat Pump 0.

However, the geometrical size, especially the thickness, of the heat transfer body is limited, and there are still limitations on the temperature range in which it can be used, as well as poor machinability. It is an object of the present invention to provide an oriented thermally conductive member which has improved thermal conductivity in the axial direction.

(Structure of the Invention) The present invention provides a carbon fiber obtained by a vapor phase growth method having a strand diameter of 5 to 20μ, preferably 10±3μ, and desirably has a thermal conductivity in the layer direction (longitudinal direction) ( In-
plane thermal conductivity
y) is 2000 to 3000 kcal/rn-h
+”C, and the thermal conductivity in the direction perpendicular to the above on the same layer plane is 2, which is equivalent to 1/100 of the above.
It is an oriented heat conductive member having a temperature of 0 to 30 kcat//rrI-hr·°C and made by covering a bundle of highly anisotropic carbon fibers with a low thermal conductive material.

The present invention was conceived based on the fact that carbon fiber produced by the vapor phase method has extremely good thermal conductivity in the axial direction, and extremely low thermal conductivity in the direction perpendicular to the axis. The vapor phase method that led to the so-called CVD method (C
chemical vapor dep6sition)
Many carbon fiber manufacturing methods have been published in the past, but the basic method is, for example, as seen in Japanese Patent Publication No. 58-22571, in which a mixed gas of a hydrocarbon such as benzene and hydrogen gas is mixed with Fe etc. It is produced by thermal decomposition at a high temperature of around 1000°C in the presence of fine particles.

The diameter of the carbon fibers obtained in this manner can be adjusted as desired depending on the conditions of the vapor phase method, but is generally 50 μm or less. In order to achieve the object of the present invention, the vapor grown carbon fiber in the present invention preferably has a thickness of 20μ or less and 5μ or more -1.

The oriented carbon fiber thermally conductive member of the present invention has an axial thermal conductivity of 2000 to 3000k at/m.
・Has a numerical value of hr・℃. The temperature range in which the above values can be obtained is from 100° to 800°. Such thermal conductivity is comparable to that of copper or iron trichloride (FeCt3), which are considered to be other good thermal conductors.

The value is actually more than five times the value in the same temperature range as above, and moreover, it is a high value that almost approximates the thermal conductivity in the layer direction of HOPG, which is known as highly oriented pyrolytic graphite with the highest degree of graphitization. It is. Such temperature-thermal conductivity characteristics are shown in FIG.

Further, the thermally conductive member with oriented carbon fibers of the present invention has a thermal conductivity of 20 to 30 kc in the direction perpendicular to its axis.
a7! /'it+-hr・'C. This value indicates that the carbon fiber having such heat transfer characteristics as described above was obtained for the first time by the present inventors. Utilizing the heat transfer properties of carbon fibers is extremely convenient for quickly dissipating locally generated heat from the location where it is generated. That is, the amount of heat dissipated by conduction is much smaller than the amount of heat dissipated by radiation and convection, and the amount of heat dissipated by radiation and convection is negligibly low compared to the amount of heat conducted. Therefore, there is an advantage that locally generated heat can be taken out of the system without having a thermal effect on the surrounding area of the generated location. For example, it is possible to find a wide range of applications such as cooling IC boards, cooling word drive sisters, cooling speaker yoke coils, and exchanging heat for high-temperature gases.

As mentioned above, the carbon fiber of the present invention has a strand diameter of 5 to 20μ,
Since the average diameter is 10μ, a plurality of strands are aligned and used as a carbon fiber bundle. The operating temperature is 5001: or less, which is the oxidation start temperature of the present carbon fiber. Since it still has excellent flexibility and elasticity, it can be bent into any shape and used without any adverse effect on thermal conductivity.

FIG. 2 shows an example of the heat conductive member of the present invention.

In the figure, reference numeral 2 denotes a bundle of carbon fibers aligned in the length direction, and the periphery thereof is coated with a low heat conductive material such as resin 1. The coating is performed by coating or welding a film. In addition to resin, water glass can also be used as this material.

Next, an example of use of the heat conductive member of the present invention will be shown.

In power transistors where heat dissipation from heat generating parts is limited due to the arrangement of the parts, the heat conductive member of the present invention is bundled with washed carbon fibers around the outer periphery of the printed circuit board to form a bundle with a diameter of 1 square inch, as shown in Figure 3. Excluding heat receiving and heat dissipating parts,
Other parts were covered with polyimide film and used. This carbon fiber was adhered to the lower part of the fixing plate 4 of the power transistor 3 with silver paste, and was adhered with silver paste to the heat dissipation plate 6 around the outer periphery of the printed circuit board 5. The temperature rise at 10 watts of self-heating of the transistor was 80°C before using this heat-conducting member, but it decreased to 30°C with the use of wood, and the heat dissipation effect was recognized to be remarkable.

[Brief explanation of the drawing]

FIG. 1 shows a temperature-thermal conductivity characteristic curve, FIG. 2 is a sectional view of the heat conductive member of the present invention, and FIG. 3 shows an example of the use of this member in a power transistor. DESCRIPTION OF SYMBOLS 1... Covering material, 2... Carbon fiber, 3... Power transistor, 4... Transistor fixing plate, 5...
- Printed circuit board, 6... heat sink, 7... case. Agent Kikudakusaba - Figure 1, Figure 2, Figure 3 Procedures Amendment (voluntary) 1981! Monday - 22nd Japan Patent Office Commissioner Kazuo Wakasugi 1. Indication of the case Patent Application No. 75825 of 1982 2. Name of the invention Oriented heat conductive member 3. Person making the amendment Relationship to the case Patent applicant address Port of Tokyo Shiba Daimon-ku, T-13-9 Representative Yasunobu Kishimoto 4, Agent (zip code 105) Address 13-8 Shiba Daimon-chome, Minato-ku, Tokyo Showa Denko Co., Ltd. Phone number 1 Tokyo 432-5111 (Main) Representative) Name (
7037) obscene, + koji spirit -5. The fence in the drawing. 6. Contents of the amendment (1) Change “pump” to “pipe” on page 1, line 18 of the specification
Correct. (2) [or iron trichloride (
Fec13) Delete J. (3) Figure 1 of the drawing will be corrected as shown in the attached sheet.

Claims (1)

[Claims] An oriented thermally conductive member comprising a bundle of vapor-grown carbon fibers having a wire diameter of 5 to 20μ and whose thermal conductivity in the longitudinal direction is significantly higher than that in the direction perpendicular to the fibers, coated with a low thermally conductive material. .