JP4340750B2 - Good thermal conductor with controlled heat flow rate and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a good heat conductor with a controlled heat flow rate. More specifically, the metal fiber is compounded with a matrix of a low melting point metal or alloy having a melting point of 120 ° C. or lower to align the metal fiber. Dispersed metal fiber-low melting point metal or alloy composite, a novel good heat conductor capable of reducing thermal resistance when the liquid phase is separated by heating and brought into contact with a heat source, and the same It relates to a manufacturing method. The heat-conductive material according to the present invention is controlled in the direction of the heat flow rate by the presence of metal fibers, and the improvement in strength due to the presence of metal fibers is remarkable, so that it can be used in a state where stress is applied. For example, the present invention can be used for a joining member with a large heat sink, and the present invention provides a good thermal 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 that conducts and cools heat from a heat source that generates heat of 100 ° C. or less, for example, a heat transfer interface that facilitates heat transfer and a method for using the same (see Patent Document 1), thermoplasticity High thermal conductive resin composition comprising a resin composition obtained by kneading a resin, an insulating inorganic filler and a reinforcing material (refer to Patent Document 2), ceramic and metal particles having excellent thermal conductivity, polymer materials such as resin and rubber A heat conductive sheet (see, for example, Patent Documents 3 to 4) that has been hardened in step 1 is used. Moreover, in order to improve heat conductivity, the heat conductive material which improved the adhesiveness with the heat source which plasticizes and contacts at the time of use is provided (for example, refer patent document 5).
[0003]
A composite material using a polymer such as a resin as a matrix has poor thermal conductivity. Therefore, even if a part of the polymer is plasticized to improve adhesion, there is a limit to improving the thermal conductivity. Therefore, it has been necessary to develop a material that has higher thermal conductivity than a resin and generates a liquid phase at 120 ° C. or lower. As materials satisfying such requirements, for example, the use of low melting point metals such as wood metal and multi-element alloys has been studied. However, since the direction of the heat flow rate cannot be controlled only with these materials, for example, when used in an environment in which stress is generated, the liquid phase is squeezed out and the heat flow rate needs to be controlled. As described above, various heat conductive materials that conduct and cool heat from a heat source have been developed in the past, but for good heat conductors in which metal fibers and low melting point metals are combined to control the heat flow rate, No examples have been developed so far.
[0004]
[Patent Document 1]
JP 2001-257298 A [Patent Document 2]
Japanese Patent Laid-Open No. 10-139928 [Patent Document 3]
JP 2002-329989 A [Patent Document 4]
JP-A-6-164174 [Patent Document 5]
Japanese Patent Laid-Open No. 2002-176126
[Problems to be solved by the invention]
Under such circumstances, the present inventors have eagerly aimed at developing a new heat-conducting material capable of drastically solving the problems in the prior art in view of the prior art. As a result of accumulated research, in order to effectively use the directivity of heat, the gap between the fibers is filled with a low melting point metal or alloy having a melting point of 120 ° C. or less, 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 part into a molten state, and the present invention has been completed.
That is, the present invention is a good heat conductor in which a gap between metal fibers is filled with a metal or alloy having a low melting point, and the low melting point metal or alloy part is melted by the heat from the heat source, and the adhesion to the heat source is achieved. It is an object of the present invention to provide a novel good heat conductor and a method for producing the same which can obtain a large heat conduction by improving the above.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention comprises the following technical means.
(1) A method for producing a good thermal conductor in which the gap between metal fibers is filled with a low melting point metal or alloy and the heat flow rate is controlled, and the low melting point metal metal fiber having a melting point in a temperature range lower than 120 ° C. metal fibers and composite dispersed oriented metal fibers in a matrix of metal or alloy - to prepare a low-melting metal or alloy composite, upper Symbol quickly generate a homogeneous liquid phase optionally formed complexes A method for producing a good heat conductor , characterized in that the good heat conductor has low thermal resistance .
(2) Good heat conduction as described in (1) above, wherein a compacted metal fiber having a porosity of 20 to 80% by volume is compressed and impregnated with a molten low melting point metal or alloy. Body manufacturing method.
(3) Good heat conduction as described in (1) above, 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. Body manufacturing method.
(4) A good heat according to (1) above, wherein a metal fiber molded body having a porosity of 20 to 80% by volume is filled with a powder of a low melting point metal or alloy and pressed to form a composite. A method for manufacturing a 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 joined by pressurization 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) above, 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 point metal or alloy having a melting point in a temperature range lower than 120 ° C. A good thermal conductor with controlled heat flow rate, characterized by comprising an oriented and dispersed metal fiber-low melting point metal or alloy composite.
(10) A highly heat-conductive joining member comprising the good heat conductor according to (9) as a constituent element.
[0007]
DETAILED DESCRIPTION OF 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 and controls the heat flow rate by combining it with metal fibers and improves the adhesion with the heat source when the matrix is dissolved. It is characterized by realizing a good heat conduction.
As the low melting point metal or alloy used in the present invention, any suitable material can be used as long as it has a melting point of 120 ° C. or lower and does not melt in the normal use temperature range of the heat conducting material. The heat source targeted by the present invention is about 100 ° C., and if the melting point exceeds 120 ° C., the matrix cannot be dissolved by the heat from the heat source. As such a low melting point metal or alloy material, for example, wood metal (50 wt% Bi-25 wt% Pb-12.5 wt% Sn-12.5 wt% Cd) and other commercially available alloys are used. However, the present invention is not limited to these, and can be used similarly as long as they have the same effect.
[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 metal fiber porous body, for example, after joining metal fibers with a paste, heating the metal fibers while removing the paste by heating, or low pressure A method of welding and joining metal fibers by pulsed electric current sintering can be used, but is not limited thereto. The metal fibers are preferably two-dimensionally oriented so that the heat flow can be controlled. For this purpose, for example, it is preferable to produce a porous body using a press or the like. If the porosity of the metal fiber porous molded body is less than 20% by volume, it is difficult to fill a metal with a low melting point 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 porous body made of metal fiber with a low melting point metal or alloy, for example, a method of powdering a low melting point metal and filling the gap between fibers, or dissolving a low melting point metal is preferable. Thus, it is possible to use a method of pressure injection into the gap between the metal fibers. When these are pulverized and the gaps between the porous molded bodies are filled, the adhesion between the metal fibers and the low melting point metal is preferably improved by heating or pressing because the adhesion with the metal fibers is poor.
[0010]
When a metal fiber porous body cannot be produced, a method of applying a metal or alloy having a low melting point to the surface of the metal fiber and molding it by pressing or heating is used. As a method for applying a metal or alloy having a low melting point to the surface of the metal fiber, preferably, for example, a method of applying the metal fiber by using a capillary phenomenon and a low melting point dissolved on the surface of the metal fiber. A method of spraying a metal or an 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 pressurizing means, for example, a method such as uniaxial pressing or rolling can be used.
[0011]
The metal fiber has a function of uniformly spreading heat from a heat source over the entire molded body, and it is preferable to use a material having 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 circular in cross section, and fibers having a rectangular cross section can also be used, but are not limited thereto. The fiber may be a continuous fiber or a cut fiber. However, in order to control the heat flow, it is preferable to use fibers having an aspect ratio of 1 or more. In addition, as a low melting point metal or alloy material, for example, a material such as wood metal can be used, but many of them use cadmium and lead which have a high environmental load, and preferably contain indium 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. Specific examples thereof include, for example, that an In—Bi—Sn alloy having an indium melting point of 60% by weight at 73 ° C., 50% by weight at 83 ° C., and 40% by weight at 88 ° C. can be produced. .
[0012]
The atmosphere in which the low melting point metal or alloy is dissolved 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, since the components contained in the low melting point metal or alloy may change, care must be taken not to increase the degree of vacuum.
[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, but it is inert to prevent oxidation of the low melting point metal or alloy or metal fiber. An atmosphere such as gas is preferred. Examples of the heat source targeted by the present invention include, but are not limited to, semiconductor elements, CPUs for computers, and chips for image processing.
[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 in the matrix. Thereby, when brought into contact with the heat source, the low melting point metal or alloy existing between the metal fibers dissolves rapidly and uniformly, thereby improving the adhesion to the heat source. Further, the mechanical strength of the molded body can be improved by the length of the metal fiber, and the strength of the molded body can be increased as the longer fiber is used.
[0015]
【Example】
EXAMPLES Next, although this invention is demonstrated concretely based on an Example, this invention is not limited at all by the following Examples.
Example 1
A copper fiber having a fiber diameter of 50 μm (manufactured by Bequinit 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 low melting point alloy In-42 mass% Bi-5 mass% Sn heated to 100 ° C., Pressure cast. The melting point of the alloy was 85 ° C.
[0016]
The obtained composite was formed into a thickness of 0.05 mm at room temperature using a roll mill. The copper fiber was planarly oriented in the sheet obtained by rolling. When this sheet was placed on a heat source, the formation of a liquid phase was observed uniformly above 85 ° C. Moreover, the thermal resistance at the time of liquid phase production | generation of this sheet | seat was 0.08 degreeC / W, and it turned out that it is a good heat conductor.
[0017]
FIG. 1 shows a constituent phase by X-ray diffraction of the obtained molded body. It was confirmed that copper did not react with the low melting point metal and was dispersed in the state of copper. Further, in FIG. 2, a stainless ball heated to 85 ° C. is placed on a sheet (left) made of only a low melting point metal and having a thickness of about 0.05 mm and a sheet of low melting point metal containing copper fibers (right). The result of having measured the temperature after 2 second with the infrared thermometer is shown. It was confirmed that the sheet in which the copper fibers are dispersed has faster heat diffusion, and the heat is well conducted in the direction in which the fibers are lined up (front to back). The sheet size was 10 mm × 20 mm.
[0018]
Example 2
Copper fiber (manufactured by Bequinit Co., Ltd.) having a fiber diameter of 100 μm 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, and an alloy powder of 100 μm or less composed of In-42 mass% Bi-5 mass% Sn is dispersed in ethyl alcohol and injected with a surfactant. did. After drying this, the molded body in which the alloy powder was dispersed in the gaps between the copper fibers was heated to 87 ° C. under a pressure of 30 MPa in vacuum to produce a 1 mm thick molded body.
[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 this formed body was further formed to a thickness of 0.2 mm by a roll mill, no cracks were generated, and a sheet-like 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 to improve adhesion with the heat source, and acted as a good heat conductor. The thermal resistance during liquid phase generation was 0.08 ° C./W.
[0020]
Example 3
Copper fiber (manufactured by Bequinit Co., Ltd.) having a fiber diameter of 100 μm was cut into a length of 40 mm, and 200 pieces thereof were bundled and immersed in a crucible in which In-42 mass% Bi-5 mass% Sn was dissolved. . By applying vibration of about 100 Hz to the fiber, a low melting point metal liquid covered the surface of the fiber, and a bundle of fibers exhibiting a silver color was obtained. In-42 mass% Bi-5 mass% Sn was dissolved by heating to 100 ° C. in the atmosphere, and aluminum oxide was used as the crucible.
[0021]
The obtained bundle of copper fibers to which the low melting point metal was adhered was rolled as it was with a roll mill to produce a 0.2 mm-thick shaped body. Since the low melting point metal was deformed during rolling, it was possible to produce a molded body having no cracks except at the end. In this sheet-like molded body, the copper fibers were oriented in one direction, and the liquid phase was uniformly generated at 85 ° C. The thermal resistance during liquid phase generation was 0.08 ° C./W.
[0022]
【The invention's effect】
As described above in detail, the present invention relates to a good heat conductor that can control the heat flow rate and a method for manufacturing the same, and the following effects are exhibited by the present invention.
(1) It is possible to obtain a good heat conductor with low thermal resistance that can control the heat flow rate to prevent temperature variation in the good heat conductor and can quickly generate a homogeneous liquid phase.
(2) 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) Compared to the conventional one that generates a liquid phase by alloy composition, by aligning metal fibers having high thermal conductivity, it is possible to prevent uneven temperature generated in the heat conductor and generate a liquid phase uniformly. 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 collecting the good heat conductor of the present invention after use, the fiber and metal 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 shape can be dramatically improved.
(6) Since the good heat conductor of the present invention transmits heat generated from the heat source in a directional manner, cooling in a limited space is possible, and the degree of freedom in designing the cooling mechanism is increased.
[Brief description of the drawings]
FIG. 1 shows X-ray diffraction of a low melting point metal sheet mixed with copper fibers.
FIG. 2 shows the temperature distribution when an 80 ° C. stainless steel sphere is placed on a low melting point metal sheet (left) and a low melting point metal sheet containing copper fibers (right).

Claims (10)

A method for producing a good thermal conductor in which a gap between metal fibers is filled with a low melting point metal or alloy to control a heat flow rate, and the metal fiber has a low melting point metal or alloy having a melting point at a temperature lower than 120 ° C. matrix metal fibers were dispersed in composite oriented metal fibers - to prepare a low-melting-point metal or alloy composite, may be arbitrarily shaped on SL complex generates a homogeneous liquid phase rapidly A method for producing a good heat conductor , characterized in that the good heat conductor has a low thermal resistance .   2. The production of a good heat conductor according to claim 1, wherein a compacted metal fiber having a porosity of 20 to 80% by volume is compressed and impregnated with a molten low melting point metal or alloy. Method.   2. A good thermal conductor according to claim 1, wherein a metal fiber molded body having a porosity of 20 to 80% by volume is filled with a powder of a low melting point metal or an alloy and heated to be compounded. Method.   2. A good thermal 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 an alloy and pressed to form a composite. Method.   2. The method for producing a good heat 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 pressure to form a composite.   2. The method for producing a good heat 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 fibers are copper fibers.   The method for producing a good heat conductor according to any one of claims 1 to 6, wherein the low melting point metal or alloy contains indium.   A metal fiber produced by the method according to any one of claims 1 to 8 is compounded 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 fiber is oriented and dispersed. A good heat conductor having a controlled heat flow rate, comprising a metal fiber-low melting point metal or alloy composite.   A highly heat-conductive joining member comprising the good heat conductor according to claim 9 as a constituent element.

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