Patent Description:
Hitherto, temperature regulation units have been used in electric equipment, electronic equipment, semiconductor equipment, etc., to protect circuits and other components that are sensitive to heat generation. More specifically, as the amount of power used by electric equipment or the like increases, the amount of heat generated also increases, and thus the internal temperature of the electric equipment or the like is regulated by cooling the generated heat with a temperature regulation unit. In such a temperature regulation unit, a metal fiber molded body formed from metal fibers is used in some cases.

As a method for manufacturing a metal fiber molded body, for example, methods disclosed in <CIT> (<CIT>), etc., are conventionally known. In the method for manufacturing a metal fiber molded body disclosed in <CIT> (<CIT>), a mold for molding is first immersed in a dispersion liquid containing metal fibers, then the metal fibers are attached by suction to a suction surface of the mold. Next, the mold is pulled up from the dispersion liquid while the metal fibers are attached by suction to the suction surface of the mold. Even after the mold is pulled up from the dispersion liquid, the metal fibers are still attached by suction to the suction surface of the mold. By repeating this operation many times, the metal fibers of a desired thickness are attached by suction to the suction surface of the mold. The metal fibers attached by suction to the suction surface of the mold are then sintered at a temperature that does not exceed the melting point of the metal fibers. Accordingly, a metal fiber molded body is produced.

In some cases, rather than a metal fiber molded body, a metal powder sintered body produced by sintering metal powder or metal bulk is used in a temperature regulation unit. <CIT> describes a method for producing uniform porous materials from metal fibers through sintering. The process involves arranging metal fibers in a mold under tension, sintering them to form a stable structure with high porosity (up to <NUM>%), and optionally post-processing for enhanced properties. This results in lightweight, flexible, and customizable porous metal materials suitable for various applications.

<CIT> describes a papermaking method for producing a metal fiber web comprising fibers having a length of <NUM> to <NUM> inches, i.e. <NUM> to <NUM>. The resulting web is then sintered. Metal compacts made using this method can be used as transpiration cooling elements and heat exchange materials.

In the metal fiber molded body produced by the manufacturing method disclosed in <CIT> (<CIT>), the metal fibers are oriented mainly in a plane direction. Therefore, a temperature regulation unit having such a metal fiber molded body has a problem that the thermal conductivity along the plane where the metal fibers are oriented is excellent, but the thermal conductivity in a direction orthogonal to the plane where the metal fibers are oriented is inferior. Meanwhile, a temperature regulation unit having a metal powder sintered body produced by sintering metal powder or metal bulk has inferior elasticity when the temperature changes, as compared to the metal fiber molded body, so that, when a heat-transfer object to which the temperature regulation unit is attached expands or contracts, the temperature regulation unit cannot follow the expansion or contraction of the heat-transfer object, causing a problem that the temperature regulation unit becomes detached from the heat-transfer object or destroyed.

The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a metal fiber molded body having excellent thermal conductivity in any direction and having excellent elasticity when the temperature changes, a temperature regulation unit including the metal fiber molded body, and a method for manufacturing the metal fiber molded body.

A first aspect of the present invention relates to a method for manufacturing a metal fiber molded body , comprising the steps of: accumulating a plurality of short metal fibers on a receiving part; and sintering the plurality of short metal fibers accumulated on the receiving part, to produce the metal fiber molded body, wherein the short metal fibers each have a length in a range of <NUM> to <NUM>. The method further comprises the step of physically impacting the short metal fibers to deform the short metal fibers, before the step of accumulating the plurality of short metal fibers on the receiving part.

A second aspect of the present invention relates to a metal fiber molded body obtainable by the manufacturing method described above.

<FIG> and <FIG> are diagrams showing the configuration of a cutter mill for physically impacting a plurality of short metal fibers. <FIG> and <FIG> are diagrams showing a method for manufacturing a metal fiber molded body according to the present embodiment. <FIG> are diagrams showing various configuration examples of a temperature regulation unit with the metal fiber molded body according to the present embodiment. <FIG> is a diagram showing a modification of a method for manufacturing the temperature regulation unit including the metal fiber molded body according to the present embodiment. <FIG> is an explanatory diagram for showing cut surfaces of a metal fiber molded body or a metal molded body, and <FIG> are cross-sectional views of metal fiber molded bodies and metal molded bodies according to examples and comparative examples.

First, the method for manufacturing the metal fiber molded body according to the present embodiment will be described with reference to <FIG>, <FIG>, <FIG>, and <FIG>. In the method for manufacturing the metal fiber molded body according to the present embodiment, a metal fiber molded body is formed by uniformly accumulating short metal fibers without using any medium such as water, and sintering the plurality of accumulated short metal fibers.

In more detail, first, a plurality of short metal fibers <NUM> are put into the inside of a cutter mill <NUM>. The configuration of the cutter mill <NUM> will be described with reference to <FIG> and <FIG>. As shown in <FIG> and FIG. 2B, a rotor <NUM> having a plurality of (for example, four) rotary blades <NUM> mounted thereon is provided inside the cutter mill <NUM>, and the rotor <NUM> is rotated about a shaft 14a. In addition, fixed blades <NUM> are provided at fixed positions around the rotor <NUM>. Moreover, a screen <NUM> is provided below the rotor <NUM>.

The plurality of short metal fibers <NUM> put into the inside of the cutter mill <NUM> through an upper opening <NUM> of the cutter mill <NUM> are ground by shearing between each fixed blade <NUM> and each rotary blade <NUM> which is mounted on the rotor <NUM> rotating about the shaft 14a. In addition, as the rotor <NUM> rotates, the plurality of short metal fibers <NUM> collide with each other inside the cutter mill <NUM>, and the short metal fibers <NUM> and the fixed blades <NUM> or the rotary blades <NUM> collide with each other, whereby the short metal fibers <NUM> are worn and deformed. Specifically, the metal fibers <NUM> are bent or folded, whereby the surfaces of the short metal fibers <NUM> become smooth. In addition, such an operation can also remove burrs from the surfaces of the short metal fibers <NUM>. The short metal fibers <NUM> sheared, worn, and deformed thus fall downward from the openings of the screen <NUM>. Then, the short metal fibers <NUM> falling downward from the openings of the screen <NUM> are collected.

Other than the cutter mill <NUM>, any device that can deform the short metal fibers <NUM> by physically impacting the short metal fibers <NUM> can be used. Examples of such a device include a stone-mill-shaped grinder (masscolloider) and a ball mill.

The short metal fibers <NUM> to be put into the inside of the cutter mill <NUM> are at least one type of fibers out of copper fibers, stainless steel fibers, nickel fibers, aluminum fibers, and alloy fibers thereof. In particular, copper fibers are preferably used as the short metal fibers <NUM>. This is because copper fibers have an excellent balance between cost and rigidity, plastic deformability, and heat transfer properties. The lengths of the physically impacted short metal fibers <NUM> are in the range of <NUM> to <NUM>, preferably in the range of <NUM> to <NUM>, and more preferably in the range of <NUM> to <NUM>. The lengths of the short metal fibers <NUM> can be confirmed by actual measurement through photographic observation (SEM, optical microscope, etc.) of a metal fiber molded body <NUM>. When the lengths of the short metal fibers <NUM> are <NUM> to <NUM>, it is easy to accumulate the short metal fibers <NUM> onto a receiving part, and the ratio, to the presence ratio of the metal fibers in a first cross-section, of the presence ratio of the metal fibers in a second cross-section orthogonal to the first cross-section in the metal fiber molded body <NUM> is easily made to be in the range of <NUM> to <NUM>.

Then, the plurality of short metal fibers <NUM> physically impacted to be deformed fall downward from the openings of the screen <NUM> of the cutter mill <NUM>. Then, the plurality of short metal fibers <NUM> falling downward from the openings of the screen <NUM> are accumulated on a graphite plate <NUM> (see <FIG>). More specifically, a molding frame <NUM> having a plurality of through holes formed therein is placed on the graphite plate <NUM> in advance, and the plurality of short metal fibers <NUM> are put into the through holes of the molding frame <NUM>. Accordingly, the plurality of short metal fibers <NUM> are accumulated inside the through holes of the molding frame <NUM> on the graphite plate <NUM>. Then, the plurality of short metal fibers <NUM> are sintered in the state shown in <FIG>, and pressed after sintering. Then, when the molding frame <NUM> is removed from the graphite plate <NUM> as shown in <FIG>, metal fiber molded bodies <NUM> are formed on the graphite plate <NUM>.

In each metal fiber molded body <NUM> manufactured by such a method, the ratio, to the presence ratio of the metal fibers in the first cross-section (for example, a cross-section P in <FIG>), of the presence ratio of the metal fibers in the second cross-section (for example, a cross-section Q in <FIG>) orthogonal to the first cross-section is in the range of <NUM> to <NUM>. That is, as a result of accumulating the plurality of short metal fibers <NUM> on the receiving part such as the graphite plate <NUM> and then sintering the plurality of short metal fibers <NUM>, the metal fibers are oriented not only in a plane direction but also in a direction orthogonal to the plane direction (that is, the thickness direction of the metal fiber molded body <NUM> (a Z direction in <FIG>)) (see <FIG>). In a metal fiber molded body obtained by immersing a mold for molding in a dispersion liquid containing metal fibers and attaching the metal fibers by suction to a suction surface of the mold as in the conventional art, the metal fibers are oriented mainly in the plane direction (see <FIG> and <FIG>). Therefore, the ratio, to the presence ratio of the metal fibers in the first cross-section (for example, the cross-section P in <FIG>), of the presence ratio of the metal fibers in the second cross-section (for example, the cross-section Q in <FIG>) orthogonal to the first cross-section is less than <NUM> or greater than <NUM>. Thus, in the metal fiber molded body <NUM> according to the present embodiment, the metal fibers are oriented not only in the plane direction (that is, an X direction and a Y direction in <FIG>) but also in a direction (that is, the Z direction in <FIG>) orthogonal to the plane direction, so that the metal fiber molded body <NUM> has excellent thermal conductivity in any direction. The properties, etc., of such a metal fiber molded body <NUM> will be described later.

Next, various configuration examples of a temperature regulation unit including such a metal fiber molded body <NUM> will be described with reference to <FIG>. The temperature regulation unit including the metal fiber molded body according to the present embodiment is attached to a heat-transfer object such as a heat-generating electric or electronic component, thereby dissipating heat from the heat-transfer object.

First, a first configuration example of the temperature regulation unit will be described with reference to <FIG> and <FIG>. A temperature regulation unit <NUM> shown in <FIG> and <FIG> has a frame-shaped exterior component <NUM> (support) and a plurality of metal fiber molded bodies <NUM> arranged in the internal space of the exterior component <NUM> so as to be spaced apart from each other. The exterior component <NUM> is formed from a material having heat transfer properties. In addition, the exterior component <NUM> is formed from a material that is impermeable to liquids and gases. Meanwhile, voids are formed between the metal fibers included in the metal fiber molded bodies <NUM>, so that the metal fiber molded bodies <NUM> allow liquids and gases to pass therethrough. As shown in <FIG>, one having a columnar shape is used as each metal fiber molded body <NUM>. In addition, each metal fiber molded body <NUM> having a columnar shape is arranged on each intersection point of grid lines. Moreover, a space <NUM> through which a fluid passes is formed between each metal fiber molded body <NUM>. By causing a liquid refrigerant to flow through such a space <NUM>, heat can be dissipated from a heat-transfer object such as an electric component or an electronic component to which the temperature regulation unit <NUM> is attached. In addition, as another application of the temperature regulation unit <NUM>, by causing a high-temperature fluid, which is to be cooled, to flow through the space <NUM>, heat may be dissipated from the fluid flowing through the space <NUM>.

Moreover, plating may be performed on the surface of the exterior component <NUM> of the temperature regulation unit <NUM> shown in <FIG> and <FIG>, for example, by thermal spraying. Alternatively, final polishing or grinding of the surface of the exterior component <NUM> may be performed. Still alternatively, the surface of the exterior component <NUM> may be embedded in resin. If these treatments are performed, the surface of the exterior component <NUM> is protected, so that wear, etc., of the exterior component <NUM> can be suppressed.

Next, a second configuration example of the temperature regulation unit will be described with reference to <FIG> and <FIG>. A temperature regulation unit <NUM> shown in <FIG> and <FIG> has a frame-shaped exterior component <NUM> (support), a plurality of metal fiber molded bodies <NUM> arranged in the internal space of the exterior component <NUM> so as to be spaced apart from each other, and a conventional metal fiber molded body <NUM> disposed in the space between each metal fiber molded body <NUM>. The conventional metal fiber molded body <NUM> is manufactured by a method described below. First, a fibrous material such as metal fibers is dispersed in water or the like to prepare a paper-making slurry. The water is filtered from the paper-making slurry to obtain a wet sheet. The wet sheet is further dehydrated. The dehydrated sheet is dried to obtain a dry sheet. Then, the dry sheet is bound at a temperature that does not exceed the melting point of the metal fibers. Accordingly, the conventional metal fiber molded body <NUM> is produced. Such a conventional metal fiber molded body <NUM> has substantially the same properties as a metal fiber molded body according to a first comparative example described later.

The exterior component <NUM> is formed from a material having heat transfer properties. In addition, the exterior component <NUM> is formed from a material that is impermeable to liquids and gases. Meanwhile, voids are formed between the metal fibers included in the metal fiber molded bodies <NUM> and the conventional metal fiber molded body <NUM>, so that the metal fiber molded bodies <NUM> and the conventional metal fiber molded body <NUM> allow liquids and gases to pass therethrough. As shown in <FIG>, one having a columnar shape is used as each metal fiber molded body <NUM>. In addition, each metal fiber molded body <NUM> having a columnar shape is arranged on each intersection point of grid lines. Moreover, since the conventional metal fiber molded body <NUM> is disposed between each metal fiber molded body <NUM>, there is no space inside the exterior component <NUM>. Such a temperature regulation unit <NUM> can also be attached to a heat-transfer object such as an electric component or an electronic component, thereby dissipating heat from the heat-transfer object. By changing the densities of the metal fiber molded bodies <NUM> and the metal fiber molded body <NUM>, the ease of passage of a medium such as a liquid or gas can also be controlled. Preferably, the density of the metal fiber molded bodies <NUM> is lower than the density of each metal fiber molded body <NUM>.

Next, a third configuration example of the temperature regulation unit will be described with reference to <FIG> and <FIG>. A temperature regulation unit <NUM> shown in <FIG> and <FIG> has a frame-shaped metal fiber molded body <NUM> and a plurality of metal fiber molded bodies <NUM> arranged in the internal space of the frame-shaped metal fiber molded body <NUM> so as to be spaced apart from each other. As each metal fiber molded body <NUM> arranged in the internal space of the frame-shaped metal fiber molded body <NUM>, one having a columnar shape is used. In addition, each metal fiber molded body <NUM> having a columnar shape is arranged on each intersection point of grid lines. As described above, voids are formed between the metal fibers included in the metal fiber molded bodies <NUM>, so that the metal fiber molded bodies <NUM> allow liquids and gases to pass therethrough. Moreover, a space <NUM> through which a fluid passes is formed between each metal fiber molded body <NUM> having a columnar shape. Voids are formed in the frame-shaped metal fiber molded body <NUM>, so that the frame-shaped metal fiber molded body <NUM> allows liquids to pass therethrough. Therefore, when a liquid is caused to flow through the space <NUM>, liquid leakage may occur. Therefore, the fluid flowing through the space <NUM> is preferably a gas. Such a temperature regulation unit <NUM> can also be attached to a heat-transfer object such as an electric component or an electronic component, thereby dissipating heat from the heat-transfer object.

Next, a fourth configuration example of the temperature regulation unit will be described with reference to <FIG>. A temperature regulation unit <NUM> shown in <FIG> has a frame-shaped exterior component <NUM> (support), a plurality of metal fiber molded bodies <NUM> (see <FIG>) arranged in the internal space of the exterior component <NUM> so as to be spaced apart from each other, and a flat-plate-shaped metal fiber molded body <NUM> (see <FIG>) for connecting each metal fiber molded body <NUM>. The exterior component <NUM> is formed from a material having heat transfer properties. In addition, the exterior component <NUM> is formed from a material that is impermeable to liquids and gases. Meanwhile, voids are formed between the metal fibers included in the metal fiber molded bodies <NUM>, so that the metal fiber molded bodies <NUM> allow liquids and gases to pass therethrough. As shown in <FIG>, one having a columnar shape is used as each of the metal fiber molded bodies <NUM> arranged in the internal space of the exterior component <NUM> so as to be spaced apart from each other. In addition, each metal fiber molded body <NUM> having a columnar shape is arranged on each intersection point of grid lines. Moreover, a space <NUM> through which a fluid passes is formed between each metal fiber molded body <NUM>.

By causing a liquid refrigerant to flow through such a space <NUM>, heat can be dissipated from a heat-transfer object such as an electric component or an electronic component to which the temperature regulation unit <NUM> is attached. In addition, as another application of the temperature regulation unit <NUM>, by causing a high-temperature fluid, which is to be cooled, to flow through the space <NUM>, heat may be dissipated from the fluid flowing through the space <NUM>.

Next, a fifth configuration example of the temperature regulation unit will be described with reference to <FIG>. A temperature regulation unit <NUM> shown in <FIG> has a frame-shaped exterior component <NUM> (support) and a plurality of metal fiber molded bodies <NUM> arranged in the internal space of the exterior component <NUM> so as to be spaced apart from each other. The exterior component <NUM> is formed from a material having heat transfer properties. In addition, the exterior component <NUM> is formed from a material that is impermeable to liquids and gases. Meanwhile, voids are formed between the metal fibers included in the metal fiber molded bodies <NUM>, so that the metal fiber molded bodies <NUM> allow liquids and gases to pass therethrough. As shown in <FIG>, one having a columnar shape is used as each metal fiber molded body <NUM>. In the temperature regulation unit <NUM> shown in <FIG>, each metal fiber molded body <NUM> having a columnar shape is not arranged on each intersection point of grid lines. Moreover, a space <NUM> through which a fluid passes is formed between each metal fiber molded body <NUM>. By causing a liquid refrigerant to flow through such a space <NUM>, heat can be dissipated from a heat-transfer object such as an electric component or an electronic component to which the temperature regulation unit <NUM> is attached. In addition, as another application of the temperature regulation unit <NUM>, by causing a high-temperature fluid, which is to be cooled, to flow through the space <NUM>, heat may be dissipated from the fluid flowing through the space <NUM>.

Next, a sixth configuration example of the temperature regulation unit will be described with reference to <FIG>. A temperature regulation unit <NUM> shown in <FIG> is obtained by bending and wrapping a plate-shaped metal fiber molded body <NUM> (support) on the outer circumferential surface of a copper pipe <NUM> used as a heat-transfer object, and further brazing fin-shaped metal fiber molded bodies <NUM> to the bent plate-shaped metal fiber molded body <NUM>. At this time, since the metal fiber molded body <NUM> contains a plurality of short metal fibers <NUM>, the metal fiber molded body <NUM> is flexible, and thus can be bent along a curved surface that is the outer circumferential surface of the pipe <NUM>, so that a gap can be inhibited from being formed between the metal fiber molded body <NUM> and the pipe <NUM>. Therefore, sufficient heat transfer properties can be maintained. With such a temperature regulation unit <NUM>, a high-temperature medium passing through an internal region <NUM> of the pipe <NUM> can be cooled. In addition, when a refrigerant is caused to flow through the internal region <NUM> of the pipe <NUM>, the environment surrounding the temperature regulation unit <NUM> can be cooled by removing heat from the environment.

Next, a method for producing a fin-shaped temperature regulation unit will be described with reference to <FIG>. First, a plurality of short metal fibers <NUM> physically impacted by the cutter mill <NUM> or the like to be deformed are accumulated on a graphite plate <NUM> (see <FIG>). More specifically, a molding frame <NUM> having a plurality of through holes formed therein is placed on the graphite plate <NUM> in advance, and the plurality of short metal fibers <NUM> are put into the through holes of the molding frame <NUM>. Accordingly, the plurality of short metal fibers <NUM> are accumulated inside the through holes of the molding frame <NUM> on the graphite plate <NUM>. Then, the plurality of short metal fibers <NUM> are sintered in the state shown in <FIG>, and pressed after sintering. Accordingly, a metal fiber molded body <NUM> is formed inside each through hole of the molding frame <NUM>. Then, the graphite plate <NUM> is removed, and nanosilver <NUM> is printed on an end portion of each metal fiber molded body <NUM>. Then, as shown in <FIG>, the surface, of the molding frame <NUM>, on the side on which the nanosilver <NUM> is printed on each metal fiber molded body <NUM> is brought into contact with the surface of a substrate <NUM>. Then, post-wetting treatment (treatment of evenly applying a thinner to the upper surface of the molding frame <NUM> shown in <FIG>) is performed on the molding frame <NUM> having the metal fiber molded body <NUM> formed inside each through hole thereof, and heating and sintering are then performed, for example, at <NUM>. At this time, the molding frame <NUM> is pressed against the substrate <NUM>. Accordingly, each metal fiber molded body <NUM> is bonded to the substrate <NUM> by the nanosilver <NUM>. Then, the molding frame <NUM> is removed as shown in <FIG>. Accordingly, the substrate <NUM> having a plurality of the fin-shaped metal fiber molded bodies <NUM> mounted thereon is obtained. Such a combination of the substrate <NUM> and the plurality of the fin-shaped metal fiber molded bodies <NUM> is also used as a temperature regulation unit.

The metal fiber molded body <NUM> configured as described above and produced by sintering the plurality of short metal fibers <NUM> accumulated on the receiving part (specifically, the graphite plate <NUM>) has excellent thermal conductivity in any direction, and also has excellent elasticity when the temperature changes. More specifically, in the metal fiber molded body obtained by immersing a mold for molding in a dispersion liquid containing metal fibers and attaching the metal fibers by suction to a suction surface of the mold as in the conventional art, the metal fibers are oriented mainly in the plane direction, so that a temperature regulation unit having such a metal fiber molded body has excellent thermal conductivity along the plane where the metal fibers are oriented, but has inferior thermal conductivity in a direction orthogonal to the plane where the metal fibers are oriented. On the other hand, as for the metal fiber molded body <NUM> of the present embodiment, the plurality of short metal fibers <NUM> are accumulated on the receiving part such as the graphite plate <NUM> and then sintered, whereby the metal fibers are oriented not only in the plane direction but also in a direction (that is, the thickness direction of the metal fiber molded body <NUM>) orthogonal to the plane direction. Therefore, the thermal conductivity becomes excellent in any direction. In addition, since the metal fiber molded body <NUM> contains the metal fibers, gaps are formed inside the metal fiber molded body <NUM>. Therefore, the metal fiber molded body <NUM> has better elasticity than a metal powder sintered body or metal bulk produced by sintering metal powder.

Hereinafter, the present invention will be described in more detail by means of examples and comparative examples. The first to sixth examples are not according to the present invention.

<NUM> of short copper fibers having an average fiber length of <NUM> and an average fiber diameter of <NUM> was put into a cutter mill (manufactured by Horai Co. : BO-<NUM> model), and the short copper fibers were processed using a <NUM> screen. Next, the short copper fibers taken out of the cutter mill were accumulated on a high-purity alumina plate (manufactured by KYOCERA Corporation). More specifically, a molding frame having a plurality of through holes (<NUM> in length, <NUM> in width, <NUM> in height) formed therein was placed on the high-purity alumina plate in advance, and the short copper fibers were put into the through holes of the molding frame. Accordingly, the short copper fibers were accumulated inside the through holes of the molding frame on the high-purity alumina plate. Then, the high-purity alumina plate having the short copper fibers accumulated inside the through holes of the molding frame thereon was put into a vacuum sintering furnace (manufactured by CHUGAI RO CO. ), and sintered in this vacuum sintering furnace under nitrogen gas at a pressure of <NUM> Torr and a sintering temperature of <NUM> for <NUM> hours. Then, the sintered bodies were taken out of the molding frame, a spacer was placed to achieve a desired thickness, and the sintered bodies were pressed at a pressure of <NUM> kN. The metal fiber molded bodies produced as described above had a thickness of <NUM> and a basis weight of <NUM>/m2.

The cut surface when the metal fiber molded body according to the first example was cut at the cross-section P in <FIG> was as shown in a photograph in <FIG>. In addition, the cut surface when the metal fiber molded body according to the first example was cut at the cross-section Q in <FIG> was as shown in a photograph in <FIG>. These photographs were taken by a scanning electron microscope (SEM) manufactured by NIKON CORPORATION. In <FIG> and <FIG>, the white portions indicate portions where the metal fibers are present, and the black portions indicate voids between the metal fibers. As shown in <FIG> and <FIG>, in the metal fiber molded body according to the first example, the metal fibers are oriented not only in a plane direction (that is, the X direction and the Y direction in <FIG>) but also in a direction (that is, the Z direction in <FIG>) orthogonal to the plane direction. Here, the presence ratio of the metal fibers in the cross-section shown in <FIG> was <NUM>, and the presence ratio of the metal fibers in the cross-section shown in <FIG> was <NUM>. Therefore, the ratio, to the presence ratio of the metal fibers in the first cross-section (cross-section shown in <FIG>), of the presence ratio of the metal fiber in the second cross-section (cross-section shown in <FIG>) orthogonal to the first cross-section was <NUM>.

<NUM> of short copper fibers having an average fiber length of <NUM> and an average fiber diameter of <NUM> was put into a cutter mill (manufactured by Horai Co. : BO-<NUM> model), and the short copper fibers were processed using a <NUM> screen. Next, the short copper fibers taken out of the cutter mill were accumulated on a high-purity alumina plate (manufactured by KYOCERA Corporation). More specifically, a molding frame having a plurality of through holes (<NUM> in length, <NUM> in width, <NUM> in height) formed therein was placed on the high-purity alumina plate in advance, and the short copper fibers were put into the through holes of the molding frame. Accordingly, the short copper fibers were accumulated inside the through holes of the molding frame on the high-purity alumina plate. Then, the high-purity alumina plate having the short copper fibers accumulated inside the through holes of the molding frame thereon was put into a vacuum sintering furnace (manufactured by CHUGAI RO CO. ), and sintered in this vacuum sintering furnace under nitrogen gas at a pressure of <NUM> Torr and a sintering temperature of <NUM> for <NUM> hours. Then, the sintered bodies were taken out of the molding frame, a spacer was placed to achieve a desired thickness, and the sintered bodies were pressed at a pressure of <NUM> kN. The metal fiber molded bodies produced as described above had a thickness of <NUM> and a basis weight of <NUM>/m2. The metal fiber molded bodies according to the second example are denser than the metal fiber molded bodies according to the first example.

The cut surface when the metal fiber molded body according to the second example was cut at the cross-section P in <FIG> was as shown in a photograph in <FIG>. In addition, the cut surface when the metal fiber molded body according to the second example was cut at the cross-section Q in <FIG> was as shown in a photograph in <FIG>. These photographs were taken by a scanning electron microscope (SEM) manufactured by NIKON CORPORATION. In <FIG> and <FIG>, the white portions indicate portions where the metal fibers are present, and the black portions indicate voids between the metal fibers. As shown in <FIG> and <FIG>, in the metal fiber molded body according to the second example, the metal fibers are oriented not only in a plane direction (that is, the X direction and the Y direction in <FIG>) but also in a direction (that is, the Z direction in <FIG>) orthogonal to the plane direction. Here, the presence ratio of the metal fibers in the cross-section shown in <FIG> was <NUM>, and the presence ratio of the metal fibers in the cross-section shown in <FIG> was <NUM>. Therefore, the ratio, to the presence ratio of the metal fibers in the first cross-section (cross-section shown in <FIG>), of the presence ratio of the metal fiber in the second cross-section (cross-section shown in <FIG>) orthogonal to the first cross-section was <NUM>.

Metal fiber molded bodies of third to sixth examples were produced in the same manner as the first example, except that short copper fibers having an average fiber length and an average fiber diameter shown in Table <NUM> were used and the size of each through hole of the high-purity alumina plate was changed as appropriate. Each physical property value is as shown in Table <NUM>.

<NUM> of short copper fibers having an average fiber length of <NUM> and a fiber diameter of <NUM> and <NUM> of PVA fibers (trade name: "Fibribond VPB105-<NUM>", manufactured by Kuraray Co. ) which has a dissolution temperature in water of <NUM> were put into water such that the concentration thereof was <NUM>%, <NUM> of a nonionic surfactant (trade name: Desgran B, manufactured by DAIWA CHEMICAL INDUSTRIES CO. ) was added to the mixture, and the mixture was agitated for dispersion. This dispersion liquid was put into a container having a diameter of <NUM> and a volume of <NUM> liters, and <NUM> liters of a paper-making polyacrylamide-based dispersing viscous agent solution (solid concentration: <NUM>%, trade name "ACRYPERSE PMP", manufactured by Mitsubishi Chemical Corporation) was further added, water was further added to make <NUM> liters, and the mixture was agitated for dispersion, to prepare a paper-making slurry. The paper-making slurry was put into a molding mold (<NUM> in diameter, <NUM> in length) having a <NUM>-mesh wire net wrapped therearound, and was dehydrated while being sucked with a vacuum pump, to obtain a wet sheet. Then, the wet sheet was put into a dryer at a temperature of <NUM> and dried for <NUM> minutes. The dried sheet was sintered in a vacuum sintering furnace under nitrogen gas at a pressure of <NUM> Torr and a sintering temperature of <NUM> for <NUM> hours. Then, the sintered bodies were taken out, a spacer was placed to achieve a desired thickness, and the sintered bodies were pressed at a pressure of <NUM> kN. The metal fiber molded bodies produced as described above had a thickness of <NUM> and a basis weight of <NUM>/m2.

The cut surface when the metal fiber molded body according to the first comparative example was cut at the cross-section P in <FIG> was as shown in a photograph in <FIG>. In addition, the cut surface when the metal fiber molded body according to the first comparative example was cut at the cross-section Q in <FIG> was as shown in a photograph in <FIG>. These photographs were taken by a scanning electron microscope (SEM) manufactured by NIKON CORPORATION. In <FIG> and <FIG>, the white portions indicate portions where the metal fibers are present, and the black portions indicate voids between the metal fibers. As shown in <FIG> and <FIG>, in the metal fiber molded body according to the first comparative example, the metal fibers are oriented mainly in a plane direction (that is, the X direction and the Y direction in <FIG>), but not so much oriented in a direction (that is, the Z direction in <FIG>) orthogonal to the plane direction. Here, the presence ratio of the metal fibers in the cross-section shown in <FIG> was <NUM>, and the presence ratio of the metal fibers in the cross-section shown in <FIG> was <NUM>. Therefore, the ratio, to the presence ratio of the metal fibers in the first cross-section (cross-section shown in <FIG>), of the presence ratio of the metal fiber in the second cross-section (cross-section shown in <FIG>) orthogonal to the first cross-section was <NUM>.

Spherical copper powder having an average diameter of <NUM> was accumulated on a high-purity alumina plate (manufactured by KYOCERA Corporation). More specifically, a molding frame having a plurality of through holes (<NUM> in length, <NUM> in width, <NUM> in height) formed therein was placed on the high-purity alumina plate in advance, and the copper powder was put into the through holes of the molding frame. Accordingly, the copper powder was accumulated inside the through holes of the molding frame on the high-purity alumina plate. Then, the high-purity alumina plate having the copper powder accumulated inside the through holes of the molding frame thereon was put into a vacuum sintering furnace (manufactured by CHUGAI RO CO. ), and sintered in this vacuum sintering furnace under nitrogen gas at a pressure of <NUM> Torr and a sintering temperature of <NUM> for <NUM> hours. Then, the sintered bodies were taken out of the molding frame. The metal molded bodies made of copper and produced as described above had a thickness of <NUM> and a basis weight of <NUM>/m2. Accordingly, the metal molded bodies made of copper were manufactured.

The cut surface when the metal molded body made of copper according to the second comparative example was cut at the cross-section P in <FIG> was as shown in a photograph in <FIG>. In addition, the cut surface when the metal molded body made of copper according to the second comparative example was cut at the cross-section Q in <FIG> was as shown in a photograph in <FIG>. These photographs were taken by a scanning electron microscope (SEM) manufactured by NIKON CORPORATION. In <FIG> and <FIG>, the white portions indicate portions where the metal is present, and the black portions indicate voids between the metals. The presence ratio of the metal in the cross-section shown in <FIG> was <NUM>, and the presence ratio of the metal in the cross-section shown in <FIG> was <NUM>. Therefore, the ratio, to the presence ratio of the metal in the first cross-section (cross-section shown in <FIG>), of the presence ratio of the metal in the second cross-section (cross-section shown in <FIG>) orthogonal to the first cross-section was <NUM>.

Irregular-shaped copper powder (manufactured by MITSUI MINING & SMELTING CO. : MA-CC (average particle diameter: <NUM>)) was accumulated on a high-purity alumina plate (manufactured by KYOCERA Corporation). More specifically, a molding frame having a plurality of through holes (<NUM> in length, <NUM> in width, <NUM> in height) formed therein was placed on the high-purity alumina plate in advance, and the irregular-shaped copper powder was put into the through holes of the molding frame. Accordingly, the irregular-shaped copper powder was accumulated inside the through holes of the molding frame on the high-purity alumina plate. Then, the high-purity alumina plate having the irregular-shaped copper powder accumulated inside the through holes of the molding frame thereon was put into a vacuum sintering furnace (manufactured by CHUGAI RO CO. ), and sintered in this vacuum sintering furnace under nitrogen gas at a pressure of <NUM> Torr and a sintering temperature of <NUM> for <NUM> hours. Then, the sintered bodies were taken out of the molding frame. The metal molded bodies made of copper and produced as described above had a thickness of <NUM> and a basis weight of <NUM>/m2. Accordingly, the metal molded bodies made of copper were manufactured.

The cut surface when the metal fiber molded body according to the third comparative example was cut at the cross-section P in <FIG> was as shown in a photograph in <FIG>. In addition, the cut surface when the metal fiber molded body according to the third comparative example was cut at the cross-section Q in <FIG> was as shown in a photograph in <FIG>. These photographs were taken by a scanning electron microscope (SEM) manufactured by NIKON CORPORATION. In <FIG> and <FIG>, the white portions indicate portions where the metal is present, and the black portions indicate voids between the metals. The presence ratio of the metal in the cross-section shown in <FIG> was <NUM>, and the presence ratio of the metal in the cross-section shown in <FIG> was <NUM>. Therefore, the ratio, to the presence ratio of the metal in the first cross-section (cross-section shown in <FIG>), of the presence ratio of the metal in the second cross-section (cross-section shown in <FIG>) orthogonal to the first cross-section was <NUM>.

A copper sheet having a thickness of <NUM> was used as a metal according to a fourth comparative example. Each physical property value is as shown in Table <NUM>.

Metal fiber molded bodies of a fifth comparative example were produced in the same manner as the first comparative example, except that short copper fibers having an average fiber length and an average fiber diameter shown in Table <NUM> were used and the size of each through hole of the high-purity alumina plate was changed as appropriate. Each physical property value is as shown in Table <NUM>.

Metal fiber molded bodies of a sixth comparative example were produced in the same manner as the first comparative example, except that short copper fibers having an average fiber length and an average fiber diameter shown in Table <NUM> were used, the size of each through hole of the high-purity alumina plate was changed as appropriate, and agitation was not performed when preparing the dispersion liquid. Each physical property value is as shown in Table <NUM>.

<NUM> of short copper fibers having an average fiber length of <NUM> and a fiber diameter of <NUM> and <NUM> of PVA fibers (trade name: "Fibribond VPB105-<NUM>", manufactured by Kuraray Co. ) which has a dissolution temperature in water of <NUM> were put into water such that the concentration thereof was <NUM>%, <NUM> of a nonionic surfactant (trade name: Desgran B, manufactured by DAIWA CHEMICAL INDUSTRIES CO. ) was added to the mixture, and the mixture was agitated for dispersion. This dispersion liquid was put into a container having a diameter of <NUM> and a volume of <NUM> liters, and <NUM> liters of a paper-making polyacrylamide-based dispersing viscous agent solution (solid concentration: <NUM>%, trade name "ACRYPERSE PMP", manufactured by Mitsubishi Chemical Corporation) was further added, water was further added to make <NUM> liters, and the mixture was agitated for dispersion, to prepare a paper-making slurry. The paper-making slurry was put into a molding mold (<NUM> in diameter, <NUM> in length) having a <NUM>-mesh wire net wrapped therearound, and was dehydrated while being sucked with a vacuum pump, to obtain a wet sheet. Then, the wet sheet was put into a dryer at a temperature of <NUM> and dried for <NUM> minutes to obtain a dry sheet. The dry sheet was impregnated with a slurry in which magnesium oxide particles were dispersed in water, was put into a dryer at a temperature of <NUM>, and was dried for <NUM> minutes. The dried sheet was sintered in a vacuum sintering furnace under nitrogen gas at a pressure of <NUM> Torr and a sintering temperature of <NUM> for <NUM> hours. Then, the sintered bodies were taken out, were immersed in dilute hydrochloric acid to dissolve and remove the magnesium oxide particles, and were then washed. Then, a spacer was placed to achieve a desired thickness, and the sintered bodies were pressed at a pressure of <NUM> kN. The metal fiber molded bodies produced as described above had a thickness of <NUM> and a basis weight of <NUM>/m2. Each physical property value is as shown in Table <NUM>.

The metal fiber molded bodies according to the first to sixth examples, the metal fiber molded bodies according to the first comparative example and the fifth to seventh comparative examples, the metal molded bodies (metal powder sintered bodies) according to the second comparative example and the third comparative example, and the metal body (metal bulk) according to the fourth comparative example were examined for ratio of metal presence ratios, thickness, space factor, thermal conductivity, elongation percentage, CTE relaxation properties, and air permeability. The results of the examinations are shown in Tables <NUM> and <NUM> below.

In Table <NUM>, etc., the ratio of metal presence ratios refers to the ratio, to the presence ratio of the metal in the first cross-section, of the presence ratio of the metal in the second cross-section orthogonal to the first cross-section in each of the metal fiber molded bodies and the metal molded bodies, etc., according to the examples and the comparative examples. In addition, the space factor refers to the ratio of the metal in the unit volume of each of the metal fiber molded bodies and the metal molded bodies, etc., according to the examples and the comparative examples. Moreover, the thermal conductivity was measured as a thermal conductivity in the thickness direction (Z direction (up-down direction) in <FIG>) of each of the metal fiber molded bodies, the metal molded bodies, etc., by the steady-state method using a steady method thermal conductivity measurement system (manufactured by ADVANCE RIKO, Inc. Moreover, the elongation percentage was measured as an elongation percentage in the plane direction (X direction or Y direction in <FIG>) of each of the metal fiber molded bodies, the metal molded bodies, etc., by a method conforming to ISO <NUM>-<NUM>: <NUM>, Metallic materials-Tensile testing-Part <NUM>: Method of test at room temperature (MOD using a Tensilon universal material testing instrument (manufactured by A&D Company, Limited)). A test piece broken at an elongation amount of not less than <NUM> ppm was determined as excellent, a test piece broken at an elongation amount of less than <NUM> ppm and not less than <NUM> ppm was determined as good, and a test piece broken at an elongation amount of less than <NUM> ppm was determined as poor.

Moreover, for the CTE relaxation properties, each of the metal fiber molded bodies and the metal molded bodies, etc., according to the examples and the comparative examples was bonded to an object such as an alumina plate by an inorganic adhesive, and it was examined whether each of the metal fiber molded bodies, the metal molded bodies, etc., follows the expansion or contraction of the object when being heated or when being cooled. Specifically, the case where, even when the object such as an alumina plate to which one of the metal fiber molded bodies, the metal molded bodies, etc., was bonded expanded or contracted, no warpage, peeling, cracking, etc., occurred due to said one of the metal fiber molded bodies, the metal molded bodies, etc., following the expansion or contraction, was evaluated as "excellent" for CTE relaxation properties, and the case where slight warpage occurred but no peeling, cracking, etc., occurred was evaluated as "good" for CTE relaxation properties. On the other hand, the case where, when the object such as an alumina plate to which one of the metal fiber molded bodies, the metal molded bodies, etc., was bonded expanded or contracted, warpage, peeling, cracking, or the like occurred in said one of the metal fiber molded bodies, the metal molded bodies, etc., was evaluated as "fair" or "poor" for CTE relaxation properties. Moreover, for the air permeability, the time required for <NUM> cc of air to pass through each of the metal molded bodies, etc., was examined by a Gurley tester method (ISO <NUM>-<NUM>) using an air permeability tester that is a Gurley type densometer (manufactured by Toyo Seiki Seisaku-sho, Ltd. ), and evaluation was made based on this passage time. The metal molded body or the like for which the passage time was less than <NUM> seconds was determined as excellent, the metal molded body or the like for which the passage time was not shorter than <NUM> seconds and shorter than <NUM> seconds was determined as good, the metal molded body or the like for which the passage time was not shorter than <NUM> seconds and shorter than <NUM> seconds was determined as fair, and the metal molded body or the like for which the passage time was not shorter than <NUM> seconds was determined as poor.

The metal fiber molded bodies according to the first to sixth examples had better thermal conductivities in the thickness direction (Z direction (up-down direction) in <FIG>) than the metal fiber molded bodies according to the first and fifth to seventh comparative examples. In the metal fiber molded bodies according to the first and fifth to seventh comparative examples, the metal fibers are oriented mainly in the plane direction, so that the thermal conductivity along the plane where the metal fibers are oriented is excellent, but the thermal conductivity in the direction (that is, the thickness direction) orthogonal to the plane where the metal fibers are oriented is inferior. On the other hand, in the metal fiber molded bodies according to the first to sixth examples, the ratio, to the presence ratio of the metal in the first cross-section, of the presence ratio of the metal in the second cross-section orthogonal to the first cross-section is in the range of <NUM> to <NUM>, and the metal fibers are oriented in both the plane direction and the thickness direction, so that the thermal conductivity in the direction (that is, the thickness direction) orthogonal to the plane where the metal fibers are oriented is excellent.

Claim 1:
A method for manufacturing a metal fiber molded body (<NUM>), the method comprising the steps of:
accumulating a plurality of short metal fibers (<NUM>) on a receiving part (<NUM>); and
sintering the plurality of short metal fibers (<NUM>) accumulated on the receiving part (<NUM>), to produce the metal fiber molded body (<NUM>), wherein
the short metal fibers (<NUM>) each have a length in a range of <NUM> to <NUM>,
further comprising the step of physically impacting the short metal fibers (<NUM>) to deform the short metal fibers (<NUM>), before the step of accumulating the plurality of short metal fibers (<NUM>) on the receiving part (<NUM>).