WO2008050906A1

WO2008050906A1 - Composite material and method for producing the same

Info

Publication number: WO2008050906A1
Application number: PCT/JP2007/071278
Authority: WO
Inventors: Tatsuichiro Kon; Toru Sawaki
Original assignee: Teijin Limited
Priority date: 2006-10-26
Filing date: 2007-10-25
Publication date: 2008-05-02
Also published as: JP2010034089A; TW200837202A

Abstract

Disclosed is a composite material having excellent thermal conductivity and high heat dissipation performance. The composite material has a thermal expansion coefficient close to those of Si, InP and GaAs as typical semiconductor substrate materials, and when such semiconductor substrate materials are directly arranged on the composite material, there is generated only little thermal stress. Specifically disclosed is a composite material containing a pitch-based graphitized carbon fiber (component A) having an average fiber diameter of 0.1-30 μm and a true density of 2.0-2.5 g/cc and a matrix metal (component B). In this composite material, the volume ratio between the component A and the component B (A/B) is from 20/80 to 90/10.

Description

Composite material and manufacturing method thereof Technical Field

The present invention relates to a composite material containing pitch-based carbon fibers and a matrix metal, and a method for producing the same. The present invention relates to a composite material suitable for a heat dissipation member such as a semiconductor substrate or an integrated circuit substrate. For more details, see Mechanical Strength, Thermal Conductivity and Conductivity.

And a composite material having a low coefficient of thermal expansion. book

Background art

High-performance carbon fibers are carbon fibers derived from fiber-like chain polymers made from chain polymers such as cellulose, polyvinyl alcohol, polyacrylonitrile (PAN), etc., and petroleum consisting of cyclic hydrocarbons. It can be classified into pitch-based carbon fibers made from pitches such as coal.

The former carbon fiber derived from a chain polymer can be used for IJ as a tough fiber by simply carbonizing. Especially, PAN-based carbon fiber has significantly higher strength and elastic modulus than ordinary synthetic polymers. Because of its high performance, it is widely used in aerospace / space equipment, construction / civil engineering materials, sports / leisure equipment, etc. by utilizing this characteristic.

On the other hand, the latter pitch-based carbon fibers exhibit their characteristics when subjected to graphitization, which is a high-temperature heat treatment, and exhibit the performance of graphite crystals. As a graphite crystal, although the crystal itself is small and not a single crystal, it has a network structure as a microcrystal, and thus exhibits remarkable anisotropy. And this graphitized pitch-based carbon fiber has higher electrical and thermal conductivity than carbon fiber derived from chain polymer, has excellent mechanical properties, and has a relatively low thermal expansion coefficient. Has characteristics.

Therefore, by combining this graphitized pitch-based carbon fiber with another material such as a metal, it is highly possible that not only high thermal conductivity can be maintained but also a low thermal expansion coefficient can be obtained. By the way, in recent years, heat generation of CPUs in electronic computers and Joule heat of integrated circuits have become problems. In addition, the problem of heat generation of lasers and light emitting diodes has also emerged.

To process heat with an efficient transfer path, it is generally necessary to use a heat dissipation material with excellent thermal conductivity, such as silver or copper. However, heating elements represented by lasers and light-emitting diodes have a problem that obstructs the application of silver and copper. That is, a material for housing or mounting a laser or a light emitting diode is required to have a coefficient of thermal expansion that is substantially the same as the material of the laser element or the light emitting element. If this condition is not satisfied, significant stress will occur between the materials, and it will be inevitable that damage will occur due to deterioration or strain.

In other words, the thermal conductivity of copper is as high as about 40 OW / m-K. However, Netsu膨Choritsu copper is 1. 7 X 10- ⁵ ZK, typical S i Netsu膨Choritsu 3 X 10- ⁶ ZK (thermal conductivity of about 168 W / m · of a semiconductor substrate material Κ) and InP thermal conductivity 4.5 X 10 ^→ K (thermal conductivity around 10 OW / m * K) and Ga As thermal expansion coefficient 5.9 X 10— ⁶ ZK (thermal expansion coefficient 46W7m · It is remarkably high compared with i). In addition, the thermal conductivity of Si, InP, and GaAs is relatively low, and is not necessarily sufficient as a heat sink.

Therefore, it is not suitable to use copper as a member for the heat sink for semiconductors as it is. Therefore, as a countermeasure, we have attempted alloying with metals such as tungsten and molybdenum, which have a low coefficient of thermal expansion. However, when tungsten or molybdenum is alloyed with copper, another problem arises that the thermal conductivity is reduced. ■

In order to solve these problems, it has been proposed to combine carbon materials such as carbon fine particles and carbon fibers with metal materials.

For example, Patent Document 1 (JP-A-9- 64254), comprise the following carbon fiber length 40 / m and a metal component material, the thermal expansion coefficient of 5 X 10 one ^⁶ ~ 10 X 10_ ⁶ / K A metal composite material is disclosed. However, there is almost no disclosure regarding the details of the carbon fiber used here, and it is difficult to say that a material preferred for achieving high performance has been studied. Therefore, the thermal conductivity of the composite material is at most 203W Zm · K is not enough as a heat dissipation member for semiconductor devices.

Patent Document 2 (Japanese Patent Application Laid-Open No. 11-61292) discloses a composite containing carbon fibers in a copper matrix and having a metal element such as titanium at the interface between copper and carbon fibers. Has been. However, the thermal conductivity of the composite material is at most about 270 WZ πι · Κ, which is not sufficient for use as a heat dissipation member of a semiconductor device.

Patent Document 3 (Japanese Patent Laid-Open No. 7-90725) discloses a pitch-based carbon fiber mill. Although this document does not describe the graphitization degree of pitch-based carbon fibers, the graphitization is performed at 2650 ° C. in the examples, so there is room for further improvement of the graphitization degree.

Patent Document 4 (Japanese Unexamined Patent Application Publication No. 2006-2240) discloses a composite containing carbon fiber and metal having a length of 300 / m or more. Although this composite has improved in-plane thermal conductivity, the heat conduction in the thickness direction is insufficient for the formation of a carbon fiber network, resulting in insufficient heat transfer.

(Patent Document 1) Japanese Unexamined Patent Publication No. 9-64254

(Patent Document 2) Japanese Patent Laid-Open No. 11-61292

(Patent Document 3) JP-A-7-90725

(Patent Document 4) Japanese Unexamined Patent Publication No. 2006-2240

In addition to semiconductors, it is known that metals such as titanium are compounded with pitch-based graphitized carbon fibers to improve thermal conductivity and to suppress thermal expansion.

.

Disclosure of the invention

An object of the present invention is to provide a composite material having excellent thermal conductivity. An object of the present invention is to provide a composite material suitable for a heat dissipation member. An object of the present invention is to provide a composite material having a thermal expansion coefficient close to Si, InP, and GaAs (thermal expansion coefficients 3 to 6 × 10 ”VK), which are typical semiconductor substrate materials. An object of the present invention is to provide a composite material having excellent mechanical properties, and to provide a method for producing the composite material.

In the present invention, a pitch-type carbon fiber graphitized at a high temperature has a size exceeding several tens of nm. It is characterized by using pitch-based graphitized carbon fiber having a crystal size and high thermal conductivity. In addition, the present invention is characterized in that the content of graphitized carbon fiber, which has better thermal conductivity than the matrix metal, is increased, and the thermal conductivity of the composite material is improved. Furthermore, the composite material of the present invention is characterized by having a thermal expansion property comparable to that of a semiconductor substrate material.

That is, the present invention includes pitch-based graphitized carbon fiber (component A) and matrix metal (component B) having an average fiber diameter of 0.1 to 30 / im and a true density of 2.0 to 2.5 g / cc. However, it is a composite material with a volume ratio (AZB) between the A component and the B component of 20/80 to 90/10.

The present invention also provides: (1) Pitch-based graphitized carbon fiber (component A) having an average fiber diameter of 0.1 to 30 xm and a true density of 2.0 to 2.5 gZcc and a matrix metal ( B component),

(2) a step of compression-molding the obtained mixture to obtain a molded body, and

(3) heating the molded body and impregnating the B component into the voids of the molded body,

The manufacturing method of the composite material containing this.

The present invention also provides a non-woven fabric or random mat mainly composed of pitch-based graphitized carbon fibers (component A) having an average fiber diameter of 0.1 to 30 m and a true density of 2.0 to 2.5 g / cc. It includes a method for producing a composite material comprising a step of heating in the presence of a metal (component B) and compressing as necessary, and melting the component B and impregnating it into a void of a nonwoven fabric or random pine cake. BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the present invention will be described in detail.

(Pitch graphitized carbon fiber)

The pitch-based graphitized carbon fiber (component A) used in the present invention occupies the main part of the composite material as a filler or a core material.

The thermal conductivity of the component A in the fiber axis direction is preferably 400 to 70 OWZm · K. More preferably, it is 500 to 70 OW / πι · K. In order for carbon fiber to exhibit such a high thermal conductivity, it is preferable that the carbon fiber has a high graphitization rate and a large crystallite size. This is due to the fact that the heat conduction in carbon fibers is mainly borne by phonon conduction.

The graphitization rate is the content of graphite crystals in the carbon fiber. The blackening rate is reflected in the true density of the carbon fiber. Therefore, the true density of the soot component is 2, 0 to 2.5 gZc c, preferably 2.1 to 2.5 g / c c, and more preferably 2.2 to 2.5 gZc c.

The crystallite size (Lc) in the c-axis direction of the A component graphite crystal (hexagonal network surface) is preferably 20 to: L 00 nm, more preferably 30 to 100 nm, and still more preferably 40 to 100 nm. The ab axis direction crystallite size (La) of the A component graphite crystal (hexagonal network surface) is preferably 30 to 200 nm, more preferably 60 to 200 nm, and still more preferably 80 to 200 nm. These crystallite sizes can be obtained by the X-ray diffraction method, and can be obtained by using the Gakushin method as an analysis method and using diffraction lines from the (002) plane and (110) plane of the graphite crystal. .

Such a carbon fiber having a high graphitization rate and a large crystallite size is preferably obtained by graphitizing at 2,300 to 3,500 ° C, more preferably 2,800 to 3,200 ° C. it can.

When the component A is used as a filler, from the viewpoint of dispersibility in the metal matrix, the average fiber length is preferably 20 to 200 m, more preferably 20 to 100 im, still more preferably 20 to 60 m. is there.

On the other hand, when the component A is used as a core material, that is, when used in the form of a nonwoven fabric or a random mat, the average fiber length is preferably 200 to 240,000 m, more preferably 500 to 240,000 / zm. .

The average fiber diameter (D1) of the component A is preferably 1 to 30 m, more preferably 3 to 20 / m, and further preferably 5 to 15 zm. The average fiber diameter (D 1) is observed with an optical microscope. When the average fiber diameter is larger than 30, the adjacent fibers tend to be fused in the infusibilization process. When the average fiber diameter is less than 1 zm, the surface area per weight of the carbon fiber is increased, and the fiber surface is substantially increased. Even if it is flat, it has irregularities on the surface In some cases, the moldability may be reduced as in the case of fibers. The percentage of the fiber diameter dispersion (S 1), which is the dispersion of the fiber diameter with respect to the average fiber diameter (D 1) observed with an optical microscope, is preferably in the range of 5 to 18%. More preferably, it is in the range of 5 to 15%.

The aspect ratio of the component A is preferably 2 to 8, 0 0 0.

It is preferable that the component A has a structure in which the graph end sheet is closed by observing the shape of the fiber end face with a transmission electron microscope. When the end face of the filler is closed as a graph sheet, generation of extra functional groups and localization of electrons due to shape do not occur, so the concentration of impurities such as water can be reduced. .

The graph end 卜 is closed. The end of the graph end sheet itself constituting the carbon fiber is not exposed at the end of the carbon fiber, the graph eye layer is bent in a substantially U shape, and the bent portion is It is the state exposed to the carbon fiber edge part.

The component A preferably has a substantially flat observation surface with a scanning electron microscope. Here, “substantially flat” means that the surface does not have intense irregularities like a fibril structure. If there are severe irregularities on the surface of the carbon fiber, the surface area during kneading with the matrix resin It is desirable that the surface irregularity be as small as possible because it causes an increase in viscosity due to an increase in viscosity and lowers moldability.

(Form of component A)

Carbon fiber (component A) can be contained in the composite material as a short fiber filler. In addition, the component A can be contained in the composite material as a carbon fiber aggregate such as a nonwoven fabric or a random mat. Furthermore, the component A can contain a mixture of short fiber filler and carbon fiber aggregate in the composite material. That is, the component A is preferably in the form of at least one selected from short fibers, non-woven fabrics and random mats.

(Nonwoven fabric)

The non-woven fabric of carbon fiber can be produced, for example, by paper making short carbon fiber fibers together with an appropriate binder.

That is, carbon fibers (component A) are arranged in a uniform thickness, and a polyvinyl alcohol aqueous solution is sprayed to create a cloth with a predetermined basis weight, which is rolled using a roller press. A non-woven fabric having an apparent thickness of 0.05 to 0.2 mm can be obtained. Polyvinyl alcohol is a non-woven paste that bonds carbon fibers together, and further converges carbon fibers, and is carbonized when molded into a composite material.

(Random pine cake)

A carbon fiber random mat can be produced through a process of infusibilization, firing, and graphitization based on a web of an original yarn mat spun by the melt-pro method. In addition, a woven fabric using carbon fiber long fibers can also be used as a core material of a composite material. However, long-fiber woven fabrics require large equipment for production, and the production process of fabrics using long fibers is somewhat complicated, so compared to non-woven fabrics and random pine-like carbon fiber aggregates. And there are some inferior parts in terms of productivity of carbon fiber aggregates. When creating a woven carbon fiber aggregate, the average fiber diameter of the carbon fibers of the long fibers used is in the range of about 5 to 30 m. When a carbon fiber assembly such as a nonwoven fabric, a random mat, or a woven fabric is used, the thermal regularity or anisotropy is applied to the composite material to be created by using the spatial regularity or anisotropy of the fiber arrangement in the assembly. Anisotropy of thermal expansion coefficient can be expressed.

However, even when a short fiber filler is used, a certain degree of orientation can be obtained through a mechanical compression process or the like during molding of the composite material.

In the case of using a carbon fiber aggregate such as a nonwoven fabric, a random mat, or a woven fabric, the short fiber filler may be used in combination mainly from the viewpoint of increasing the thermal conductivity of the portion that becomes the void. It is preferably carried out and is suitable for improving the thermal conductivity of the composite material or adjusting the thermal expansion rate.

(Manufacture of component A)

The component A can be produced by spinning a raw material pitch by a known melt spinning method or melt blowing method, and then infusibilizing, firing, milling, sieving, and graphitization. The graph sheet as described above is closed, and the Z or scanning electron microscope observation surface is substantially flat. The A component can be preferably obtained by performing graphitization after milling. be able to.

The method for producing carbon fiber by the melt blow method is as follows. (pitch)

In order to obtain a carbon fiber material having a high graphitization rate, a cyclic hydrocarbon having a condensed heterocyclic ring, that is, a pitch-based raw material, is preferable instead of a raw material such as PAN and rayon. Examples of such pitch-based materials include condensed polycyclic hydrocarbon compounds such as naphthalene and phenanthrene, and condensed heterocyclic compounds such as petroleum pitch and coal pitch. In particular, condensed polycyclic hydrocarbon compounds such as naphthenol and phenanthrene are preferred.

Among these, an optically anisotropic pitch, that is, mesophase pitch is particularly preferable. These may be used singly or in appropriate combination of two or more, but using mesophase pitch alone can increase the graphitization rate in the graphitization treatment, and as a result The heat conductivity of carbon fiber can be improved, which is preferable.

The pitch of the raw material pitch (preferably the saddle point is in the range of 230 to 340 ° C. The softening point can be determined by the Meller method. If the softening point is lower than 230 ° C, the fiber is infusible. If the temperature is higher than 340 ° C, the pitch tends to be thermally decomposed during the spinning process, which tends to make spinning difficult. Under certain conditions, gas components are generated, bubbles are generated inside the spun fiber, leading to strength deterioration, and yarn breakage is likely to occur.

(Spinning)

—This is the process of extruding the melted raw material pitch from the spinning nozzle. A spinning nozzle having a nozzle hole length / hole diameter ratio smaller than 3 is preferably used, and more preferably about 1.5.

There are no particular restrictions on the nozzle temperature during spinning, and there is no problem as long as the temperature can maintain a stable spinning state. When the viscosity of the raw material pitch is in an appropriate range, the spinning state is stabilized, that is, the pitch viscosity during spinning is 0.1 to 20 Pa · S, preferably 8 to 16 Pa · S, more preferably 10 to 14 P. a · S temperature is acceptable.

Fibers spun out from the nozzle holes are shortened by blowing gas at a linear velocity of 100 to 10,000 m per minute heated to 100 to 370 ° C in the vicinity of the thinning point Is done. Air, nitrogen, argon, etc. can be used as the gas to be blown, but air is preferable from the viewpoint of cost performance.

The fibers are collected on a wire mesh belt, become a continuous mat, and are further cross-wrapped to form a web with a predetermined basis weight (weight per unit area).

The web made of pitch fibers thus obtained has a three-dimensional randomness due to the entanglement of the fibers (in the present invention, this shape is defined as a random pine or random pine shape). A random mat made of this pitch fiber is infusible, fired, and graphitized is a pitch-based graphitized carbon fiber aggregate of random pine as referred to in the present invention. This web can be infusibilized by known methods. This infusibilization temperature is 2200 to 300 ° C.

(Infusibilization)

Infusibilization is achieved by applying heat treatment for a certain period of time at a temperature of 200 to 300 ° C using air or a mixed gas in which ozone, nitrogen dioxide, nitrogen, oxygen, iodine or bromine is added to air. Is done. Considering safety and convenience, it is desirable to carry out in air.

(Baking)

The infusible pitch fiber is then fired in a temperature range of 700 to 900 ° C. in a vacuum or in an inert gas such as nitrogen, argon or krypton. Usually, firing is performed at low pressure using nitrogen with low cost.

(Milling, sieving)

Infusible / fired pitch fiber webs are further shortened and milled and sieved to achieve the desired fiber length. For milling, a pulverizer or cutting machine such as a Victory mill, a jet mill, or a high-speed rotary mill is used. In order to perform milling efficiently, it is appropriate to cut the fiber in a direction perpendicular to the fiber axis by rotating the mouth attached with the blade at high speed. The average fiber length of the fibers produced by milling is controlled by adjusting the number of rotations of blades, the angle of the blade, etc., and can be classified by the combination of the coarseness of the sieve through a sieve. (Graphitization)

The carbon fiber after milling and sieving is heated to 2,300 to 3,500 and graphitized to obtain the final carbon fiber. Graphitization is preferably performed in a non-oxidizing atmosphere in an Atchison furnace or the like.

Carbon fiber can also be produced by a melt spinning method. However, in terms of the productivity and quality of carbon fibers (surface properties, appearance, etc.), the Mel-Pro spinning method is superior.

The carbon fiber having a fine fiber diameter can be produced, for example, by the method described in International Publication No. 0 4/0 3 1 4 61 pamphlet. In this method, a composite fiber is prepared by a blend spinning method (or a composite spinning method) using a carbon material as a core material and an olefin-based material as a matrix material, and the matrix material is dissolved and removed as a post-treatment. Finally, it is a method for producing fine carbon fibers having a fiber diameter of about 0.1 to 1 m. This method can also be suitably used. Overall, the fiber diameter of the carbon fiber (component A) preferably used in the present invention is in the range of about 0.1 to 30 xm.

(surface treatment)

The component A is preferably surface-treated as necessary. Surface treatment is performed by coating resin, inorganic substance, metal oxide, metal, and their fine particles on the surface of carbon fiber, surface activation by introduction of hydrophilic functional groups and metal elements, and introduction of hydrophobic groups. The main purpose is surface deactivation and surface roughness control by etching. Specific surface treatment methods include various coating treatments (dipping coating, spray coating, electrodeposition coating, various plating, plasma C VD, etc.), ozone treatment, ozone water treatment, plasma treatment, corona treatment. , Ion implantation treatment, electrolytic oxidation treatment, acid / alkali and other chemical solution treatment.

The A component is preferably subjected to a surface treatment, and then the resin component is preferably from 0.01 to 10 parts by weight, more preferably 0.1 by weight, based on 100 parts by weight of the A component. Up to 2.5 parts by weight may be added. Examples of resin components include epoxy compounds, aromatic polyamide compounds, saturated polyesters, unsaturated polyesters, vinyl acetate, water, Lucol and glycol can be used alone or in a mixture thereof. Such surface treatment may be an effective means when trying to improve the dispersibility of the A component. However, since excessive adhesion results in thermal resistance, it can be implemented according to the required physical properties. '(Matrix metal: B component)

Matrix metal (component B) is gold, silver, copper, aluminum, magnesium, beryllium, tungsten, gallium, hafnium, titanium, silicon, alloys between these metals, alloys with these metals as main components It is preferable that the carbonaceous material is at least one selected from the group consisting of these carbonitrides, these nitrides, and these carbonitrides.

Further, the soot component is preferably a material selected from the group consisting of copper and copper-based alloys, carbides, nitrides, and carbonitrides.

The soot component is preferably a material selected from the group consisting of titanium and alloys containing titanium as a main component, carbide, nitride, and carbonitride.

The soot component can be used in the form of fine particles or metal foil. Various kinds of fine particles are commercially available, and various compositions, purity, particle sizes, etc. can be obtained. The average particle size of the fine particles is preferably 150 m or less, more preferably 10 Om or less, and even more preferably 50 xm or less.

From the viewpoint of increasing the packing density when mixing carbon fibers and metal fine particles (mixing step), two or more types having different particle sizes may be mixed as necessary. For example, average particle size 3 to: particles of L 0 im and particles of average particle size 30 to 50 m in a ratio of 50/500 to 10 Z 9 0 in the volume ratio of the former Z and the latter Can be used. There are various commercially available metal foils. The desired one can also be obtained by the following method. For example, copper powder (particle size 3-4 xm) is washed with alcohol, taken out on filter paper, dried with a vacuum dryer, and 2% by weight paraffin wax is added to the metal powder before press molding. Then, transfer to a square mold of 100 mm square and 100 mm square, and obtain a flat copper foil force by powder metallurgy treatment such as pressurizing to 2 to 10 tons / cm ² using a press machine. It is done. The volume ratio (AZB) between component A and component B is 20/80 to 90Z10, preferably 30Z70 to 70Z30. When A / B is less than 20Z80, improvement of thermal conductivity and reduction of thermal expansion coefficient are often insufficient. On the other hand, when it exceeds 90/10, the composite material becomes brittle and often has insufficient strength.

(Physical properties of composite materials)

The thermal conductivity of the composite material of the present invention is at least 30 WZm'K or more, preferably 60 WZm'K or more, more preferably 12 OW / m · K or more, more preferably 24 OWZm · K or more, most preferably 36 OW. / m · K or more.

The thermal expansion coefficient (room temperature ~ 600 ° C) is at least 15X10- ⁶ ZK below, preferred properly is 13 X 10 one ^e / K or less, more preferably ¹⁰ X 10- Θ ΖΚ less, more favorable Mashiku is 8 X 10 It is not more than ¹⁶ mm, most preferably not more than ⁶ × 10−6 mm. The filling rate of the composite material can be obtained by using the true density of the pitch-based graphitized carbon fiber and the true density of the metal material. In other words, from the theoretical density with no voids according to the mixing ratio and the value of the measured density, the percentage can be expressed as filling rate = apparent density Ζtheoretical density X 1 00 (%).

When the main purpose is to increase heat conduction (except when a porous material is intentionally made), the filling rate is preferably at least 90%, more preferably 93% or more, and still more preferably 95%. % Or more, most preferably 97% or more. <Production method for composite materials 材料>

The composite material of the present invention comprises: (1) pitch-based graphitized carbon fiber (component A) having a mean fiber diameter of 0.1 to 30 / zm and a true density of 2.0 to 2.5 gZcc (component A) and matri Process of mixing metal (metal component B) (mixing process),

(2) compression molding the resulting mixture to obtain a molded body (compression molding process), and

(3) It can be produced by a process (impregnation process) in which the compact is heated and the B component is impregnated into the voids of the compact. Here, the compression molding step and the impregnation step can be performed almost simultaneously.

(Mixing process) The mixing of the short fiber A component and the fine particle B component can be carried out using a mixing device such as a stirrer or a bead mill, or a kneading device.

It is also possible to perform granulation using both components before this, and in this case, granulation can be performed using an organic thickener. Examples of organic thickeners include paraffin wax and polyvinyl alcohol adhesive. These organic substances are preferably hydrocarbons that can be graphitized in the final treatment.

(Compression molding process)

The compression molding can be performed by a press molding method or a cast molding method using hydraulic pressure, hydrostatic pressure, or the like at room temperature or under heating. In order to increase the melt permeability of the B component and prevent the carbon fiber from being oxidized, the compression molding is preferably performed in a vacuum or in an inert atmosphere such as nitrogen. Compression molding is a process for producing an integrally molded body.

(Impregnation process)

This step is a step of heating the molded product and deforming or melting the B component so as to impregnate the voids of the molded product, and it is preferably performed while further compressing at a high pressure as necessary. Depending on the application, it is also preferable to apply three-dimensional isotropic compression. An example of a three-dimensional isotropic compression device is an HIP device. This step is a step of integrating and densifying the A component and the B component.

In the process of heating a molded product containing carbon fiber (component A) and matrix metal (component B), diffusion of metal atoms or metal compound molecules occurs slightly on the low temperature side of the melting point of the metal. It is well known that the movement and diffusion of atoms in the vicinity of the surface occur, and this may improve the adhesion and wettability of both materials, and can be preferably used as production conditions.

In order to increase the melt permeability of component B and prevent oxidation of the carbon fiber, it is recommended that the heating process be performed in a vacuum or in an inert atmosphere such as nitrogen.

The composite material of the present invention comprises a nonwoven fabric or a random mat mainly composed of pitch-based graphitized carbon fibers (component A) having an average fiber diameter of 0.1 to 30 m and a true density of 2.0 to 2.5 g Zcc. Heat in the presence of matrix metal (component B) and pressure as required While shrinking, the B component can be melted and impregnated into a non-woven fabric or random mat void.

In this method, for example, fiber aggregates such as nonwoven fabric and random mat and metal particles

It is also possible to prepare a laminate in which (B component) is alternately stacked, heat it, and compress it as necessary for integration. As the component B, it is preferable to use matrix metal fine particles or metal foil. Further, a nonwoven fabric or a random mat pre-coated with metal particles (component B) can also be used. In addition, it is possible to preferably carry out the presence of the A component in the short fiber form together with the B component in the laminate.

(Heating)

The heating temperature is around the melting point of the B component. For example, when the B component is copper, it is preferable to heat to a temperature close to the melting point of copper (about 100 ° C.) to increase the deformability or permeability of copper.

(Other ingredients)

Further, the composite material of the present invention may contain other components in addition to the carbon fiber (component A) and the matrix metal (component B). Examples of these include, in addition to the resin binder described above, graphite fine particles, expanded graphite, flake graphite, PAN-based carbon fibers, and carbon materials such as woven fabrics and nonwoven fabrics made of the carbon fibers. <Heat dissipation material>

The composite material of the present invention can be used as a high-performance heat dissipation material in various applications. For example, cutting, cutting, and polishing are preferably performed to form a thin piece, a small piece, or a part. For example, it is processed according to the shape of the heat sink.

The composite material of the present invention can be made of various physical properties that are isotropic or anisotropic. That is, it is isotropic when pitch-based graphitized fibers are randomly arranged in the composite material, and anisotropic when carbon fibers are arranged with orientation regularity. .

To create composite materials with anisotropic physical properties, for example, carbon fiber at the preparation stage A method of giving anisotropy in the direction to the arrangement and the compressive force at the time of forming a molded body is preferable. In particular, a method using a fiber assembly such as a nonwoven fabric or a random mat is preferable for imparting a large anisotropy.

In order to create a composite material having isotropic physical properties, it is preferable to use short fiber carbon fibers. It is preferable to use a fiber having a short fiber length, and a short fiber having an average fiber length of 50 im or less is particularly preferably used.

In addition, the composite material of the present invention is preferably subjected to processing such as joining, lamination, assembly, and assembly processing to form a heat radiating member having a predetermined shape and dimension. For example, a heat radiating plate is suitably obtained. be able to.

If the metal foil powder-molded metal foil and the non-woven thin layer of graphitized fiber are alternately laminated and provided with a considerable amount of thickness, the laminate is appropriately cut in the direction of the press. A planar sheet with the thickness direction is cut out. A cutting sheet having such a plane can be preferably used as a heat dissipating material having a high thermal conductivity in the thickness direction.

In this way, graphitized fiber has high thermal conductivity in the fiber axis direction, and the thermal conductivity is relatively low in the direction perpendicular to this axis, so that a small amount of graphitized fiber functions well with anisotropy. In order to arrange the heat sink, it is preferable to cut the stacked molded body laminates in a direction substantially perpendicular to the lamination surface to produce a heat radiating plate in which the lamination direction is the thickness direction. It is also effective to perform such a cutting operation. Example

Examples are shown below, but the present invention is not limited thereto. The physical properties in the examples were measured by the following methods.

(1) Average fiber diameter of carbon fiber

The pitch-based carbon fiber that had undergone graphitization was photographed at 10 fields of view under an optical microscope at 400 magnifications, the dimensions were determined from the magnified photographic images, and the average value of 60 fibers was calculated.

(2) Average fiber length of carbon fiber

The average fiber length is the number average fiber length and is a graphitized pitch-based carbon short fiber filler. 2,000 were measured with a length measuring device under an optical microscope (10 fields, 200 at a time), and the average value was obtained. The magnification was appropriately adjusted according to the fiber length.

(3) True density of carbon fiber

It calculated | required using the specific gravity method.

(4) Carbon fiber crystal size

Calculated by X-ray diffraction, the crystal size in the thickness direction (c-axis direction) of the hexagonal mesh plane is obtained using diffraction lines from the (00 2) plane, and the crystal size in the growth direction of the hexagonal mesh plane (ab axis) is (1 10) Determined using diffraction lines from the surface. In addition, the method was determined according to the Gakushin Law.

(5) Thermal conductivity of carbon fiber

The resistivity of the graphitized fiber prepared under the same conditions other than the pulverization process was measured, and the following formula (1) showing the relationship between the thermal conductivity and the electrical resistivity disclosed in JP-A-1-1117143 From 1).

C = l 272. 4 / ER-49. 4 (1)

Here, C is the thermal conductivity (WZm · K) of the graphitized fiber, and ER is the electrical resistivity / Ωπι of the same fiber.

(6) Thermal conductivity of the compact

Calculated using the following formula (2).

Thermal conductivity = specific gravity X specific heat X thermal diffusivity (2)

Here, the specific gravity was measured using the Archimedes method, the specific heat was measured using the DSC method, and the thermal diffusivity was measured using the laser-flash method at room temperature.

Experimental Example 1 Production of graphitized carbon fiber

(Spinning)

Pitch made of condensed polycyclic hydrocarbon compound was used as the main raw material. The optical anisotropy ratio was 100%, and the softening point was 283 ° C. Using a spinneret with a diameter of 0.2 mm in diameter, carbon fiber with an average fiber diameter of 15 / m is drawn by blowing hot air from the slits at a linear velocity of 5,000 m / min and pulling the molten pitch. Was spun. The spun carbon fiber is collected on a belt to form a mat, and the basis weight is 320 g by cross wrapping. A random mat of Zm ² was used.

(Infusibilization, firing, graphitization)

This random mat was infusibilized by raising the temperature from 175 ° C to 280 ° C in air at an average rate of 7 ° CZ. The infusible random mat was fired at 800 ° C in a nitrogen atmosphere, then milled and sieved to fibers with an average fiber length of 500 m (carbon fiber A) and fibers with an average fiber length of 50 m (carbon fiber B). Divided.

Thereafter, carbon fiber A and carbon fiber B were each graphitized by heat treatment at 3,000 ° C in an electric furnace in a non-oxidizing atmosphere. The average fiber diameter was 9.7 m. The percentage of the fiber diameter dispersion to the average fiber diameter was 14%. The true density was 2.18 g Ze e.

Using a transmission electron microscope, carbon fibers A and B obtained at a magnification of 1 million were observed and magnified on a photograph at 4 million times. It was confirmed that the graphene sheet was closed at the end faces of carbon fibers A and B. The surfaces of carbon fibers A and B, which were observed with a scanning electron microscope at a magnification of 4,000 times, had no large irregularities and were smooth.

The crystallite size in the c-axis direction of the graphite crystals of carbon fibers A and B determined by X-ray diffraction was 33 nm. The crystallite size in the ab axis direction was 57 nm.

In addition, the single yarn was extracted from the graphitized web, which was produced in the same process up to firing and was not milled, and heat treated at 3,000 ° C in an electric furnace with a non-oxidizing atmosphere. When the resistance was measured, it was 2.2 ^ Ω · πι. The thermal conductivity obtained using the following equation (1) was 53 OW / m · K.

C = 1272. 4 ER-49. 4 (1)

(ER is the electrical resistivity, and the unit here is / χΩ * m)

Experimental Example 2 Production of graphitized carbon fiber

(Spinning)

A pitch made of a condensed polycyclic hydrocarbon compound was used as a main raw material. Optical anisotropy percentage was 100%, the softening point was 283 ^D C. Uses spinneret with a diameter of 0.2 mm Then, heated air was ejected from the slits at a linear velocity of 6,000 m / min, and the molten pitch was pulled to produce carbon fibers with an average fiber diameter of 11 m. The spun carbon fibers were collected on a belt to form a mat, and then a random mat composed of carbon fibers having a basis weight of 280 g / m ^{2 by} cross-wrapping.

(Infusibilization, firing, graphitization)

This random mat was infusibilized by raising the temperature from 175 ° C to 280 ° C at an average heating rate of 7 ° C / min. The infusible random mat was fired at 800 ° C in a nitrogen atmosphere and then milled into fibers with an average fiber length of 30 O m (carbon fiber C) and fibers with an average fiber length of 30 m (carbon fiber D). Sieving was performed.

Thereafter, carbon fiber C and carbon fiber D were each graphitized by heat treatment at 3,000 ° C in an electric furnace in a non-oxidizing atmosphere. The average fiber diameter of carbon fibers C and D was 8.1 m. The true density was 2.21 g / c c. It was observed at a magnification of 1 million with a transmission electron microscope, and magnified on a photograph at 4 million times. The end faces of carbon fibers C and D were closed with darafen sheets. In addition, the surfaces of carbon fibers C and D observed with a scanning electron microscope at a magnification of 4,000 times were smooth with no large irregularities.

The crystallite size of carbon fibers C and D in the c-axis direction of graphite crystals determined by X-ray diffraction was 41 nm. The crystallite size in the ab axis direction was 68 nm.

A single yarn is extracted from a carbon fiber web that has been manufactured in the same process up to firing, and has not been milled, and heat treated at 3,000 ° C in an electric furnace with a non-oxidizing atmosphere. The measured value was 2.0 Ω · m. The thermal conductivity in the fiber axis direction determined using the above formula (1) was 580 W / m · K. Table 1 shows the characteristics of carbon fibers A and B obtained in Experimental Example 1 and carbon fibers C and D obtained in Experimental Example 2. table 1

Example 3 Fabrication of nonwoven fabric

50 parts by volume of carbon fiber A prepared in Experimental Example 1, 40 parts by volume of carbon fiber C obtained in Experimental Example 2, and 10 parts by volume of PV A fiber (trade name vinylon) with an average fiber length of 5 mm as a binder were mixed. Later, after making paper using a 30 ° C water bath, after calcining at 1,500 ° C under a nitrogen atmosphere and then firing at 3,000 ° C, a nonwoven fabric made of graphitized carbon fiber was obtained. It was. The obtained nonwoven fabric had a carbon content of 99% by weight, a thickness of 0.3 mm, and a filling rate of 35% by volume.

Experimental Example 4 Production of graphitized random mat

The random mat created in Experimental Example 1 was heated in air from 170 ° C to 310 ° C at an average heating rate of 5 ° CZ for infusibility, then fired at 700 ° C, and then further The graphitized random mat was obtained by calcination and graphitization at 3,000 ° C. The values of thermal conductivity, specific gravity and the like were the same as those of the carbon fiber of Example 1. Example 1

The carbon fiber B prepared in Experimental Example 1 was treated with ozone water. That is, using an ozone water treatment device manufactured by ERC Technology, carbon fiber surface treatment was performed for 30 minutes in ozone water circulated at a high ozone concentration to make the carbon fiber surface hydrophilic. Hydrophilicity was confirmed from the concentration of C = 0 group in the surface functional group analysis using ESCA.

50 parts by volume of this surface-hydrophilized carbon fiber B, copper powder with an average particle size of about 40 im (manufactured by High Purity Chemical Laboratory) 33. 3 parts by volume of copper powder with an average particle size of about 5 m (high purity chemical research) 16. After mixing 7 parts by volume with a bead mill, 5 Omm diameter The mixture was put into a container and subjected to compression molding in a vacuum at a temperature of 50 MPa and 900 to 1,050 ° C. to obtain a composite molded body composed of carbon fiber and copper.

Filling rate by specific gravity calculation is 96%, thermal conductivity and thermal expansion coefficient in the direction perpendicular to the press direction (A direction) are 35 OWXm · K, 10 X 10 "VK, press direction (B direction) is 28 OWZm · K, was 11 X 10- ⁶ ΖΚ.

Furthermore, when this compact was subjected to isotropic pressure compression with heating using a HI Ρ device manufactured by Kobe Steel, and further densified, the filling rate improved to 99%. thermal conductivity and thermal expansion coefficient of a direction became ^{39 OWZm · K, 10X 10- 6} ΖΚ :, in Β direction 31 OW / m · K, 10 X 10 one ^{6 ΖΚ.}

Example 2

The carbon fiber D prepared in Experimental Example 2 was treated with ozone water. That is, using an ozone water treatment device manufactured by ERC Technology, carbon fiber surface treatment was performed for 30 minutes in ozone water circulated at a high ozone concentration to make the carbon fiber surface hydrophilic. Hydrophilization was confirmed from the concentration-up data of C = Ο group in the surface functional group analysis using ESCA. 50 parts by volume of this carbon fiber D with hydrophilic surface, copper powder with an average particle size of about 40 im (manufactured by High Purity Chemical Laboratory) 33. 16. After uniformly mixing 7 parts by volume using a peas mill, place them in a 5 Omm diameter container and perform compression molding under vacuum at a temperature of 50 MPa and 900 to 1050 ° C. A composite molded body made of fiber and copper was obtained.

Filling rate by the specific gravity calculation is 95%, the thermal conductivity and thermal expansion coefficient in the direction perpendicular to the pressing direction (A direction) is 36 OW / m · K, 11 X 10- 6 / Κ, the pressing direction (beta in direction) 30 OW / m 'Κ, was 12 X 10- ⁶ / Κ.

Furthermore, when this compact was subjected to isotropic pressure compression with heating using a HI Ρ device manufactured by Kobe Steel, and further densified, the filling rate improved to 99%. thermal conductivity and thermal expansion coefficient of a direction is 38 OW / m · K, 1 1 X 10- 6 ΖΚ, in Β direction 33 OW / m · K, and a 11X 10- ⁶ ΖΚ.

Example 3

The non-woven fabric created in Experimental Example 3 and a 0.2 mm thick copper foil were alternately laminated 50 times. Thereafter, compression molding was performed under vacuum at a temperature range of 50 MPa, 900 to 1,050 ° C. to obtain a composite molded body composed of carbon fiber and copper.

Filling rate by the specific gravity calculation is 97%, the thermal conductivity and thermal expansion coefficient in the direction perpendicular to the pressing direction (A direction) is ^{39 OWZm · K, 10X 10- 6} Κ, the pressing direction (beta direction) at 29 OWZm was · Κ :, 12 X 10- ⁶ Roh K.

Example 4

After alternately stacking the random mat created in Experimental Example 4 and a 0.3 mm thick copper foil 30 times, compression molding was performed in a temperature range of 50 MPa, 900-1, 050 under vacuum, and carbon fiber and copper A composite molded body was obtained.

Filling rate by the specific gravity calculation is 97%, the thermal conductivity and thermal expansion coefficient in the direction perpendicular to the pressing direction (A direction) is 38 OW / m · K, 12 X 10- 6 / Κ, the pressing direction

It was (beta direction) at 31 OWZm · K, 13 X 10- 6 ΖΚ.

Comparative Example 1

In Example 1, without using carbon fiber, copper powder having an average particle size of about 40 im (manufactured by High Purity Chemical Research Laboratory) 40 parts by volume, copper powder having an average particle size of about 5 m (manufactured by High Purity Chemical Research Laboratory) After 20 parts by volume were uniformly mixed using a bead mill, it was placed in a 5 Omm diameter container, and compression molding was performed in a temperature range of 50 MPa and 900 to 1,050 ° C. under vacuum to obtain a molded body.

Filling factor becomes 98%, the thermal conductivity and the thermal expansion rate was 370 WZm · K, 1 7 X 1 0- 6 ΖΚ. In this molded product, there was almost no difference in physical properties between the heel direction and the B direction.

Furthermore, this compact was subjected to isotropic pressure compression under heating using a HIP device manufactured by Kobe Steel, and further densification treatment was performed. As a result, the filling rate was improved to 99%. Den electrical and thermal expansion ratio was 38 OWZm · K, 17X 10 one ⁶ / kappa.

That is, when comparing the molded body of Examples 1 to 4 and the molded body of Comparative Example 1, the thermal conductivity values are almost the same, but the thermal expansion values of the molded bodies of Examples 1 to 4 are significantly higher. Small and excellent in thermal expansion coefficient matching with semiconductor substrates and ceramic materials.

Example 5 The carbon fiber D prepared in Experimental Example 2 was treated with ozone water. That is, using an ozone water treatment device manufactured by ERC Technology Co., Ltd., carbon fiber surface treatment was performed for 30 minutes in ozone water circulated at a high ozone concentration to make the carbon fiber surface hydrophilic. The hydrophilization was confirmed from the concentration of C = O group in the surface functional group analysis using ESCA.

60 parts by volume of this surface-hydrophilized carbon fiber D and 40 parts by volume of titanium powder (manufactured by High Purity Chemical Laboratories) with an average particle size of about 40 m are mixed uniformly using a bead mill, and then placed in a 50 mm diameter container. Under vacuum, compression molding was performed at a temperature range of 50 MPa, 1,500 to 1,650 ° C. to obtain a composite molded body made of carbon fiber and titanium.

Filling rate by the specific gravity calculation is 97%, the thermal conductivity and thermal expansion coefficient in the direction perpendicular to the pressing direction (A direction) 1 1 OWZm ·:, 6 X 10- 6 / K :, pressing direction (beta direction ) 7 OW / m · K, 7 X 10— ^δ ΖΚ.

Furthermore, when this compact was subjected to isotropic pressure compression with heating using a HI Ρ device manufactured by Kobe Steel, and further densified, the filling rate improved to 99%. thermal conductivity and thermal expansion coefficient of a direction is 12 OWZm · K, 6 X 1 Ο- 6 Bruno Κ, 8 OW / m · K at Β direction became 6X 10_ ⁶ Bruno kappa.

Comparative Example 2

In Example 5, without using carbon fiber, titanium powder having an average particle size of about 40 m (manufactured by Kojundo Chemical Laboratories) was placed in a 5 Omm diameter container, and 50 MPa, 1, 500-1 Compression molding was performed in the temperature range of 650 ° C to obtain a molded body.

The filling rate was 98%, and the thermal conductivity and the thermal expansion coefficient were 2 OWZm · K, 8 X 10 ¹⁶ . In this compact, there are almost no differences in the physical properties between the heel direction and the B direction.

Furthermore, when this compact was subjected to isotropic pressure compression with heating using a HIP apparatus manufactured by Kobe Steel, and further densified, the filling rate improved to 99%. thermal conductivity and thermal expansion coefficient were almost the same as 2 OW / m * K, 8 X 10- 6 ΖΚ. That is, the molded product of Example 5 had a significantly improved thermal conductivity and excellent heat dissipation compared with the molded product of Comparative Example 2. Further, the thermal expansion coefficient of the molded body of Example 5 was significantly small, and the matching with the thermal expansion coefficient of the semiconductor substrate or the ceramic material was excellent. The invention's effect

The composite material of the present invention has excellent heat conductivity and high heat dissipation performance. Since the composite material of the present invention has a thermal expansion coefficient value close to Si, InP, and GaAs, which are typical semiconductor substrate materials, for example, when laminated directly on these semiconductor substrate materials. However, there are advantages such as less generation of thermal stress. The composite material of the present invention is lightweight and excellent in mechanical properties. According to the production method of the present invention, the composite material can be produced. The composite material of the present invention is subjected to processing such as alignment, lamination, and arrangement, and the alignment angle of the black portion, the direction of the film layer state, etc. are adjusted, and the thermal conductivity, thermal expansion coefficient, etc. It is possible to have a realistic anisotropy. In addition, when used as a heat sink, the amount of heat transfer and thermal expansion can be adjusted according to the purpose so that excess or deficiency does not occur in relation to peripheral devices.

The composite material of the present invention can be used as a heat sink for electronic components by utilizing its high thermal conductivity. In addition, since high thermal conductivity can be obtained by increasing the amount of graphitized fiber filler, automobiles that require heat resistance in electronic components are also used in industrial power modules that require large currents. It can be suitably used for connectors and the like. Specifically, it can be used for heat sinks, semiconductor package components, heat sinks, heat spreaders, die pads, printed wiring boards, cooling fan components, housings, and the like. It can also be used as a heat exchanger component and can be used as a heat pipe. Furthermore, it is possible to use the radio wave shielding property of a carbon fiber filler, and particularly to use it suitably as a radio wave shielding member in the GH z band.

Claims

The scope of the claims

1. Contains pitch-based graphitized carbon fiber (component A) and matrix metal (component B) with an average fiber diameter of 0.1 to 30 m and true density of 2.0 to 2.5 g / cc. A composite material with a volume ratio (AZB) to the component of 20/80 to 90/10.

2. The crystallite size of the A component in the c-axis direction (L c) ifi The composite material according to claim 1, which is 20 to 100 nm.

3. The composite material according to claim 1, wherein the crystallite size (La) force of the A component in the ab axis direction is 30 to 200 nm.

4. The composite material according to claim 1, wherein the average fiber length of the component A is 20 to 200 m.

5. The composite material according to claim 1, wherein the aspect ratio of the A component is 2 to 8000.

6. The composite material according to claim 1, wherein component A is pitch-based graphitized carbon fiber graphitized at 2,800 to 3,200 ° C.

7. The composite material according to claim 1, wherein the thermal conductivity of the component A is 400 to 700 W / m · K.

8. The composite material according to claim 1, wherein the component A is in at least one form selected from short fibers, non-woven fabrics, and random mats.

9. The composite material according to claim 8, wherein the component A is in the form of a short fiber.

10. The composite material according to claim 8, wherein the component A is in the form of a nonwoven fabric or a random mat.

11. The composite material according to claim 8, wherein the component A is in the form of a mixture of short fibers and a nonwoven fabric or a random mat.

12. B component is gold, silver, copper, aluminum, magnesium, beryllium, evening tungsten, gallium, hafnium, titanium, silicon, alloys between these metals, alloys with these metals as main components 2. The composite material according to claim 1, which is at least one selected from the group consisting of these carbides, these nitrides, and these carbonitrides.

13. The composite material according to claim 12, wherein the B component is a material selected from the group consisting of copper and copper-based alloys, carbides, nitrides, and carbonitrides.

14. The composite material according to claim 12, wherein the B component is a material selected from the group consisting of titanium and titanium-based alloys, carbides, nitrides, and carbonitrides.

15. A heat dissipating member comprising the composite material according to claim 1.

16. (1) Average fiber diameter in the form of short fibers 0.1 to 30 m, true density 2.0 to 2.

A step of mixing 5 g / c c of pitch-based graphitized carbon fiber (component A) and matrix metal (component B);

The manufacturing method of the composite material containing this.

17. Average fiber diameter 0.1 to 30 m, true density 2.0 to 2.5 g / cc pitch Graphitized carbon fiber (component A) Strength, mainly non-woven fabric or random mat is heated in the presence of matrix metal (component B), and compressed as necessary to melt the component B to create a non-woven fabric or random mat A method for producing a composite material comprising a step of impregnating a void of a random mat.