JP2004238646A - Good thermal conductor having controlled heat flow rate and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a good thermal conductor in which metal fiber is dispersed and to provide the good thermal conductor produced by the method. <P>SOLUTION: In the method for producing the good thermal conductor having controlled heat flow rate, metal fiber is composed with a matrix of metal or alloy having a melting point of ≤120°C to prepare a metal fiber/low-melting point metal or alloy composite in which the metal fiber is oriented and dispersed, and the composite is arbitrarily shaped. The good thermal conductor is constituted of the metal fiber/low-melting point metal or alloy composite which is prepared by this method and in which the metal fiber is composed with the matrix of the low-melting point metal or alloy having a melting point of ≤120°C. By this method, the good thermal conductor in which the heat flow rate can be controlled and a variance in temperature in the good thermal conductor can be prevented and a homogeneous liquid phase can be rapidly generated and which has low thermal resistance can be obtained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a good heat conductor having a controlled heat flow rate, and more specifically, a method in which a metal fiber is composited with a low melting point metal or alloy matrix having a melting point of 120 ° C. or less to orient a metal fiber. Disclosed metal fiber-low melting point metal or alloy composite, a new good thermal conductor which can reduce the thermal resistance when its liquid phase separates by heating and comes into contact with a heat source, and its novel It relates to a manufacturing method. The good heat conductive material according to the present invention controls the direction of the heat flow velocity due to the presence of the metal fiber, and has a remarkable improvement in strength due to the presence of the metal fiber, so that it can be used under stress. For example, it can be used as a joining member for a large heat sink and the like, and the present invention provides a good heat conductor with such a controlled heat flow rate and a method for efficiently manufacturing the same. Useful.
[0002]
[Prior art]
Conventionally, as a heat conductive material for conducting and cooling heat from a heat source that generates heat of 100 ° C. or less, for example, a heat transfer interface that facilitates heat transfer, a method of using the same (see Patent Document 1), and thermoplastics Highly heat-conductive resin composition composed of a resin composition obtained by kneading a resin, an inorganic filler having insulating properties, and a reinforcing material (see Patent Document 2), a ceramic material having excellent heat conductivity, or a polymer material such as resin or rubber. For example, a heat conductive sheet (for example, refer to Patent Documents 3 and 4) that has been hardened is used. Further, in order to improve the thermal conductivity, a heat conductive material is provided which has improved adhesion to a heat source which is plasticized and comes into contact during use (for example, see Patent Document 5).
[0003]
Since a composite material using a polymer such as a resin as a matrix has a poor thermal conductivity, there is a limit to the improvement of the thermal conductivity even if a part of the polymer is plasticized to improve the adhesiveness. Therefore, it has been necessary to develop a material that has a higher thermal conductivity than a resin and generates a liquid phase at 120 ° C. or lower. As materials satisfying such requirements, for example, use of low melting point metals such as wood metal or multi-element alloys is being studied. However, since the direction of the heat flow rate cannot be controlled only with these materials, when used in an environment where stress is generated, for example, the liquid phase is squeezed out and the heat flow rate needs to be controlled. As described above, conventionally, various heat conductive materials that conduct heat from a heat source and cool them have been developed.However, for a good heat conductor in which a metal fiber and a low melting point metal are combined to control a heat flow rate, No examples have been developed so far.
[0004]
[Patent Document 1]
JP 2001-257298 A [Patent Document 2]
Japanese Patent Application Laid-Open No. H10-139928 [Patent Document 3]
JP 2002-329989 A [Patent Document 4]
JP-A-6-164174 [Patent Document 5]
JP, 2002-176126, A
[Problems to be solved by the invention]
Under these circumstances, the present inventors have made a keen effort to develop a new good heat conductive material that can drastically solve the problems in the above-mentioned conventional technology in view of the above-mentioned conventional technology. As a result of accumulated research, in order to effectively utilize the directivity of heat, the gap is filled with a low melting point metal or alloy having a melting point of 120 ° C or less using metal fibers, and the heat from the heat source is used. It has been found that good heat conduction can be achieved by bringing a low melting point metal or alloy into a molten state, and the present invention has been completed.
That is, the present invention is a good thermal conductor in which the gaps between the metal fibers are filled with a low melting point metal or alloy, and the low melting point metal or alloy portion is brought into a molten state by heat from the heat source, and the adhesiveness with the heat source is obtained. It is an object of the present invention to provide a new good heat conductor which can obtain a large heat conduction by improving the above, and a method for manufacturing the same.
[0006]
[Means for Solving the Problems]
Means for Solving the Problems In order to solve the above-mentioned problems, the present invention includes the following technical means.
(1) A method for producing a good thermal conductor with a controlled heat flow rate, comprising: forming a composite of a metal fiber with a matrix of a low melting point metal or alloy having a melting point at a temperature lower than 120 ° C. to orient the metal fiber. A method for producing a good thermal conductor, comprising preparing a composite of a dispersed metal fiber and a low-melting metal or alloy, and optionally forming the composite.
(2) Good heat conduction according to (1), wherein a molded body of metal fiber having a porosity of 20 to 80% by volume is impregnated with a molten low melting point metal or alloy under pressure to form a composite. How to make the body.
(3) Good heat conduction according to the above (1), wherein a molded body of a metal fiber having a porosity of 20 to 80% by volume is filled with a powder of a low-melting-point metal or alloy and heated to form a composite. How to make the body.
(4) Good heat according to the above (1), wherein a low melting point metal or alloy powder is filled in a metal fiber compact having a porosity of 20 to 80% by volume, and the powder is composited by pressing. Manufacturing method of conductor.
(5) The method for producing a good heat conductor according to the above (1), wherein a low melting point metal or alloy is applied to the surface of the metal fiber, and the fiber is bonded under pressure to form a composite.
(6) The method for producing a good heat conductor according to the above (1), wherein a low melting point metal or alloy is applied to the surface of the metal fiber, and the fibers are joined by heating to form a composite.
(7) The method for producing a good heat conductor according to any one of (1) to (6), wherein the metal fiber is a copper fiber.
(8) The method for producing a good thermal conductor according to any one of (1) to (6), wherein indium is contained in the low melting point metal or alloy.
(9) The metal fiber produced by the method according to any one of (1) to (8) is compounded with a matrix of a low-melting metal or alloy having a melting point in a region lower than 120 ° C. to form a metal fiber. A good thermal conductor having a controlled heat flow rate, comprising a composite of a metal fiber-low melting point metal or alloy composite that is oriented and dispersed.
(10) A high heat conductive bonding member comprising the good heat conductor according to (9) as a constituent element.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in more detail.
The present invention uses a low-melting-point metal or alloy material for the matrix, controls the heat flow rate by compounding it with metal fibers, and improves the adhesion to the heat source when the matrix is melted. It is characterized by realizing excellent heat conduction.
As the low melting point metal or alloy used in the present invention, an appropriate material can be used as long as it has a melting point of 120 ° C. or less and does not melt in the temperature range where the heat conducting material is always used. The heat source targeted by the present invention is a heat source having a temperature of about 100 ° C. If the melting point is higher than 120 ° C., the matrix cannot be dissolved by heat from the heat source. As such a low melting point metal or alloy material, for example, wood metal (50% by weight Bi-25% by weight Pb-12.5% by weight Sn-12.5% by weight Cd) or other commercially available alloy is used. However, the present invention is not limited to these, and any one having the same effect can be used.
[0008]
In the present invention, the metal fiber is preferably used after being formed into a porous body having a porosity of 20 to 80% by volume. As a method for producing a porous body of metal fibers, preferably, for example, after bonding the metal fibers with a glue, a method of sintering the metal fibers while removing the glue by heating, or a method of applying a low pressure However, the method of welding and joining metal fibers by pulse current sintering can be used, but is not limited thereto. It is preferable that the metal fiber be two-dimensionally oriented in order to control the flow of heat. For this purpose, it is preferable to produce a porous body using, for example, a press. If the porosity of the porous molded body of the metal fiber is less than 20% by volume, it is difficult to fill the low melting point metal between the metal fibers, and if the porosity exceeds 80% by volume, the orientation of the metal fiber is controlled. Therefore, it is not possible to control the heat flow rate using metal fibers.
[0009]
As a method of filling a low-melting metal or alloy into a porous body made of metal fibers, for example, a method of pulverizing a low-melting metal and filling the gaps between fibers, or dissolving a low-melting metal is preferable. Then, a method of injecting pressure into the gap between the metal fibers can be used. When these are powdered to fill the gaps of the porous molded body, the adhesion between the metal fibers and the low melting point metal is preferably improved by heating or pressurizing because the adhesion between the metal fibers is poor.
[0010]
When a porous body of metal fibers cannot be produced, a method of applying a metal or alloy having a low melting point to the surface of the metal fibers and molding by applying pressure or heating is used. As a method of applying a low-melting metal or alloy to the surface of the metal fiber, preferably, for example, a method of applying a metal fiber by using a capillary action by springing, or a method of applying a low-melting metal dissolved on the surface of the metal fiber For example, a method of spraying a metal or alloy can be used. A composite fiber obtained by applying a low melting point metal to a metal fiber can be formed by pressing or heating. As the pressing means, for example, a method such as uniaxial pressing or rolling can be used.
[0011]
The metal fiber has a function of uniformly spreading the heat from the heat source to the entire molded body, and it is preferable to use a material having a high thermal conductivity as the metal fiber. Therefore, it is most preferable to use copper fiber as the metal fiber. The thickness of the metal fiber is not particularly specified, but preferably a metal fiber of 100 μm or less can be used. The shape is preferably a circular cross section, and a fiber having a rectangular cross section can be used, but is not limited thereto. The fibers may be continuous fibers or cut fibers. However, to control the heat flow, it is preferable to use fibers having an aspect ratio of 1 or more. Further, as the low melting point metal or alloy material, for example, a material such as wood metal can be used, but cadmium or lead having a high environmental load is often used, and indium is preferably used as a main component. It is desirable to use a low melting point metal or alloy material. In this case, the melting point can be easily changed depending on the amount of indium, and a melting point of 120 ° C. or less can be realized without using cadmium or lead. As a specific example of these, for example, in an In-Bi-Sn alloy, it is possible to produce an alloy having a melting point of 73 ° C at 60% by weight of indium, 83 ° C at 50% by weight, and 88 ° C at 40% by weight. .
[0012]
The atmosphere in which the low melting point metal or alloy is melted by heating is not particularly limited, but an inert gas atmosphere is preferable in order to prevent oxidation of metal fibers or low melting point metal or alloy. A vacuum atmosphere can also be used, but in this case, care must be taken not to increase the degree of vacuum because the components contained in the low melting point metal or alloy may change.
[0013]
The treatment atmosphere for improving the adhesion between the low melting point metal or alloy and the metal fiber by pressurization is not particularly limited. However, in order to prevent oxidation of the low melting point metal or alloy or oxidation of the metal fiber, an inert atmosphere is used. An atmosphere such as a gas is preferred. Examples of the heat source to which the present invention is applied include, but are not limited to, a semiconductor element, a CPU for a computer, a chip for image processing, and the like.
[0014]
According to the method of the present invention, a good heat conductor having a structure in which heat is diffused in the longitudinal direction of the metal fiber is obtained by orienting the metal fiber having high heat conductivity and filling the matrix into the matrix. Thereby, when it is brought into contact with a heat source, the low melting point metal or alloy existing between the metal fibers is rapidly and uniformly melted, whereby the adhesion to the heat source can be improved. Further, the mechanical strength of the molded article can be improved by the length of the metal fiber, and the longer the fiber is, the higher the strength of the molded article can be.
[0015]
【Example】
Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples.
Example 1
A copper fiber having a fiber diameter of 50 μm (manufactured by Bekinit Co., Ltd.) was processed into a porous body having a porosity of 50% by volume by low-pressure pulse current sintering. The size of the obtained molded body is 40 mm × 40 mm × 2 mm, and impregnated with a material obtained by heating and melting a low melting point alloy of In-42 mass% Bi-5 mass% Sn at 100 ° C. It was pressure cast. The melting point of the above alloy was 85 ° C.
[0016]
The obtained composite was formed into a thickness of 0.05 mm at room temperature by a roll mill. The sheet obtained by rolling had copper fibers oriented in a plane. When the sheet was placed on a heat source, it was found that a liquid phase was uniformly formed above 85 ° C. The sheet had a thermal resistance of 0.08 ° C./W when a liquid phase was generated, and was found to be a good heat conductor.
[0017]
FIG. 1 shows the constituent phases of the obtained molded body by X-ray diffraction. It was confirmed that copper did not react with the low melting point metal and was dispersed in a copper state. FIG. 2 shows a stainless steel ball heated to 85 ° C. placed on a sheet (left) made of only low melting point metal and having a thickness of about 0.05 mm (left) and a sheet of low melting point metal containing copper fibers (right). The result of measuring the temperature after 2 seconds with an infrared thermometer is shown. It was confirmed that the sheet in which the copper fibers were dispersed diffused heat faster, and the heat was well conducted in the direction in which the fibers were arranged (front to back). The size of the sheet was 10 mm × 20 mm.
[0018]
Example 2
A copper fiber having a fiber diameter of 100 μm (manufactured by Bekinit Co., Ltd.) was processed into a porous body having a porosity of 50% by volume by low-pressure pulse current sintering. The size of the obtained molded body is 50 mmΦ × 2 mm, into which 100 μm or less alloy powder of In-42 mass% Bi-5 mass% Sn is dispersed in ethyl alcohol together with a surfactant and injected. did. After drying, the compact in which the alloy powder was dispersed in the gaps between the copper fibers was heated to 87 ° C. in a vacuum under a pressure of 30 MPa to produce a compact having a thickness of 1 mm.
[0019]
The obtained molded body was a composite material in which copper fibers were planarly oriented, and a liquid phase was generated at 85 ° C. When the formed body was further formed into a thickness of 0.2 mm by a roll rolling mill, no crack or the like was generated, and a sheet-shaped formed body could be obtained. When this sheet was brought into contact with a heat source at 100 ° C., a liquid phase was uniformly formed, the adhesion to the heat source was improved, and the sheet acted as a good heat conductor. The thermal resistance during the generation of the liquid phase was 0.08 ° C./W.
[0020]
Example 3
A copper fiber having a fiber diameter of 100 μm (manufactured by Bekinit Co., Ltd.) was cut into a length of 40 mm, and 200 were bundled and immersed in a crucible in which In-42 mass% Bi-5 mass% Sn was dissolved. . By applying a vibration of about 100 Hz to the fiber, the liquid of the low-melting metal covered the surface of the fiber, and a bundle of silver-colored fibers was obtained. The dissolution of In-42 mass% Bi-5 mass% Sn was performed by heating to 100 ° C. in the air, and aluminum crucible was used as the crucible.
[0021]
The obtained bundle of copper fibers to which the low-melting-point metal was adhered was directly rolled by a roll rolling mill to produce a molded body having a thickness of 0.2 mm. Since the low-melting-point metal was deformed during rolling, it was possible to produce a molded body having no cracks except at the ends. In this sheet-like molded body, the copper fibers were oriented in one direction, and a liquid phase was uniformly generated at 85 ° C. The thermal resistance during the generation of the liquid phase was 0.08 ° C./W.
[0022]
【The invention's effect】
As described in detail above, the present invention relates to a good heat conductor capable of controlling a heat flow rate and a method for manufacturing the same, and the following effects are exerted by the present invention.
(1) It is possible to obtain a good heat conductor having a low thermal resistance capable of controlling the heat flow rate to prevent temperature variations in the good heat conductor and quickly generating a homogeneous liquid phase.
(2) By using the good heat conductor of the present invention, heat generated from a minute portion is transmitted to a large cooling module, so that heat can be efficiently radiated.
(3) It is possible to prevent unevenness in temperature generated in the heat conductor by orienting the metal fibers having high thermal conductivity and generate the liquid phase uniformly, as compared with the conventional one in which a liquid phase is generated by the alloy composition. it can.
(4) Since the low melting point metal and the metal fiber constituting the good heat conductor of the present invention do not react with each other, when recovering the good heat conductor of the present invention after use, the fiber and the metal are removed. It can be easily disassembled and separated.
(5) By using a long fiber as the metal fiber, the strength and durability of the good heat conductor formed into a sheet can be dramatically improved.
(6) Since the good heat conductor of the present invention transfers heat generated from a heat source in a directional manner, cooling in a limited space becomes possible, and the degree of freedom for designing a cooling mechanism increases.
[Brief description of the drawings]
FIG. 1 shows an X-ray diffraction of a low melting point metal sheet mixed with a copper fiber.
FIG. 2 shows a temperature distribution when stainless steel balls at 80 ° C. are placed on a low-melting metal sheet (left) and a low-melting metal sheet containing copper fibers (right).

Claims (10)

A method for producing a good thermal conductor with a controlled heat flow rate, wherein metal fibers are composited with a matrix of a low melting point metal or alloy having a melting point in a region lower than 120 ° C., and the metal fibers are oriented and dispersed. A method for producing a good thermal conductor, comprising preparing a metal fiber-low melting point metal or alloy composite and optionally molding the composite. 2. A good heat conductor according to claim 1, wherein a molded body of a metal fiber having a porosity of 20 to 80% by volume is impregnated with a molten low melting point metal or alloy under pressure to form a composite. Method. 2. A good heat conductor according to claim 1, wherein a metal fiber compact having a porosity of 20 to 80% by volume is filled with a powder of a low melting point metal or alloy and heated to form a composite. Method. 2. A good heat conductor according to claim 1, wherein a low melting point metal or alloy powder is filled into a metal fiber compact having a porosity of 20 to 80% by volume, and the powder is composited. Method. 2. The method for producing a good thermal conductor according to claim 1, wherein a low-melting metal or an alloy is applied to the surface of the metal fiber, and the fiber is joined under pressure to form a composite. 2. The method for producing a good thermal conductor according to claim 1, wherein a low melting point metal or alloy is applied to the surface of the metal fiber, and the fiber is joined by heating to form a composite. The method for producing a good heat conductor according to any one of claims 1 to 6, wherein the metal fiber is a copper fiber. 7. The method for producing a good thermal conductor according to claim 1, wherein indium is contained in the low melting point metal or alloy. A metal fiber produced by the method according to any one of claims 1 to 8, which is composited with a matrix of a low melting point metal or alloy having a melting point in a temperature range lower than 120 ° C, and the metal fibers are oriented and dispersed. A good heat conductor having a controlled heat flow rate, comprising a composite of metal fiber-low melting point metal or alloy. A highly heat-conductive joining member comprising the good heat conductor according to claim 9 as a component.

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