JP2002168575A - Heat pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight heat pipe having a desired strength and exhibiting excellent machinability in which water can be used as working liquid. SOLUTION: The heat pipe comprises two sheets of clad plate material made of at least two kinds of different material where each face forming the inner wall of a container having a cavity part is made of a member exhibiting excellent affinity to water, an outer circumferential part as the joint face of the two sheets of clad plate material forming the cavity part in airtight state, and a working liquid of water or principally comprising water being encapsulated in the cavity part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat pipe for cooling a heating element such as a semiconductor chip or an integrated circuit board, and more particularly to a heat pipe using water as a working fluid.

[0002]

2. Description of the Related Art In recent years, electric and electronic devices, for example, personal computers (hereinafter referred to as "personal computers") have been improved in performance, and accordingly, CPUs, which are the heart of personal computers, have been developed.
The calorific value is rising steadily. In particular, in a notebook personal computer that is required to be small, thin and light, heat generated by the CPU is moved to a predetermined position to maintain the arithmetic function of the CPU.
A device for cooling U to a predetermined temperature is an essential requirement.

[0003] Currently used methods include C
The heat generated from the heat-generating components of the PU is first received by a heat-receiving block made of metal or the like having excellent thermal conductivity, and the heat transferred to the heat-receiving block is transferred to a predetermined position where fins and the like can be installed by a heat pipe. The technology of moving and radiating heat by the fin at that position is adopted. The heat pipe seals the working fluid in a sealed cavity inside the pipe formed by sealing the joint between the working fluid inlet and the member, degass the inside of the cavity, and removes the working fluid and the working fluid. A heat transfer device having a structure that is filled only with saturated steam.

[0004] Heat pipes made by conventional techniques are classified into several types according to the material and shape of a closed container called a container and the type of working fluid to be enclosed. The shape is roughly divided into the above-mentioned pipe-shaped heat pipe and the flat plate-shaped heat pipe. The material of the container is roughly classified into a copper-based and an aluminum-based heat pipe. Hydraulic fluids are roughly classified according to their compatibility with the material of the container.Water is used for copper-based containers, but for aluminum-based containers,
A chlorofluorocarbon-based solvent or a hydrocarbon-based substance is used.

[0005] A conventional method for manufacturing a heat pipe will be described. In a conventional method of manufacturing a heat pipe using water as a hydraulic fluid, a copper upper plate having a concave portion for forming a cavity and a hydraulic fluid inlet and a copper flat lower plate are prepared. Next, the upper plate material and the lower plate material thus prepared are combined to assemble a container having a cavity formed by a concave portion, and both members are brazed and joined with a predetermined device.

Next, water as a working fluid is injected from the working fluid inlet of the container thus formed. Next, the heat pipe is heated by a predetermined device to boil the working fluid, and the inside of the container is deaerated using the working fluid inlet. Next, the working fluid inlet is caulked and welded to prepare a heat pipe while the inside of the container is degassed.

[0007]

Conventionally, most of the heat pipes generally used are made of a combination of a copper-based container and a hydraulic fluid. But,
Copper has a problem that it has a large specific gravity and thus is heavy, and it is difficult to form a flat thin heat pipe because of poor workability.

On the other hand, aluminum is lightweight and a container having relatively high degree of freedom can be produced by extrusion or the like. However, when water is used as the hydraulic fluid, the aluminum reacts with the water,
It is known that non-condensable hydrogen is generated, and there is a problem in that the generated hydrogen deteriorates the characteristics of the heat pipe. Therefore, when an aluminum-based container is used, an alternative chlorofluorocarbon such as R123 or a hydrocarbon such as butane or pentane is used as the working fluid. However, the above-mentioned hydraulic fluid may be subject to regulation of CFCs or regulation of the Fire Service Law,
Further, there is a problem that the latent heat is small and the performance of the heat pipe is significantly inferior to that of the copper heat pipe.

As a measure for solving the above-mentioned problems, it is conceivable to form a protective film or the like so that the surface of the aluminum container does not react with water. A film could not be formed. Furthermore, even if the protective film is formed, there is a problem that the protective film cannot seal the aluminum container to form a closed cavity. Heat pipes are not provided. Furthermore,
As described above, the upper plate material and the lower plate material are used to assemble a container having a hollow portion, and by using predetermined equipment, brazing and joining both members, when using a copper plate material, a silver solder is used. There is a problem that the copper plate material is so-called annealed with heat treatment at a temperature of about 800 ° C. when used, and the strength of the plate material is reduced.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to overcome the problems of the prior art, to provide a heat pipe having desired strength, light weight and excellent workability, in which water can be used as a hydraulic fluid. Is to provide.

[0011]

Means for Solving the Problems The present inventor has made intensive studies to solve the above-mentioned conventional problems. as a result,
For example, two clad plates made of at least two different members made of a thin copper member and a thin aluminum member excellent in workability are used, and each surface forming the inner wall of the container is compatible with water. When a heat pipe having a cavity is formed by assembling a member having excellent properties, for example, copper, a desired strength is secured by a thin copper member, and excellent workability is secured by a thin aluminum member, and It was found that compatibility with water could be ensured. That is, it has the desired strength, is lightweight,
In addition, a heat pipe which can use water as a working fluid and has excellent workability is provided.

Further, one of the two clad materials described above is made of, for example, two kinds of metal members composed of a copper member and an aluminum member, and the other clad material of the two clad materials is For example, each surface of the clad material is made of a copper member, an aluminum member and a copper member, or a metal member of two or three layers composed of a copper member, an aluminum member and a nickel member, and forms an inner wall of the container. It has been found that when a container is formed such that is made of a copper member, characteristics such as ease of soldering, corrosion prevention, and discoloration prevention are further obtained by a member located on the outermost side.

The present invention has been made based on the above findings, and a first aspect of the heat pipe of the present invention is a heat pipe including the following members. Two clad plates made of at least two different members, each surface forming an inner wall of a container having a cavity, made of a member having excellent compatibility with water, and the cavity is made airtight. An outer peripheral portion as a joining surface of the two clad plate materials, and water or a hydraulic fluid containing water as a main component sealed in the hollow portion.

[0014] A second aspect of the heat pipe of the present invention is as follows.
Each of the two clad members is made of two kinds of metal members, the metal member is made of a copper member and an aluminum member, and forms the inner wall of the container. Is a heat pipe having the surface made of the copper member.

[0015] A third aspect of the heat pipe of the present invention is as follows.
A heat pipe further comprising an airtight auxiliary member, wherein an outer peripheral portion as the bonding surface is bonded by the bending process via the airtight auxiliary member to form the hollow portion in an airtight state.

A fourth aspect of the heat pipe of the present invention is as follows.
The thickness of the member having the largest specific gravity among the thicknesses of the members constituting the clad plate is not more than 1 / (the number of members constituting the clad plate) of the total weight of the clad plate. It is a pipe.

According to another aspect of the heat pipe of the present invention, one of the two clad members is made of two kinds of metal members composed of a copper member and an aluminum member. The other cladding material of
Each surface of the clad material is made of a copper member, an aluminum member and a copper member, or a metal member of two or three layers composed of a copper member, an aluminum member and a nickel member, and forms an inner wall of the container. Is a heat pipe made of the copper member.

Another aspect of the heat pipe of the present invention is a heat pipe in which an outer peripheral portion as the joining surface is joined by welding or bending to form the hollow portion in an airtight state.

Another aspect of the heat pipe of the present invention is a heat pipe further comprising a wick having a capillary force in the hollow portion.

Another aspect of the heat pipe of the present invention is a heat pipe having a portion for injecting and deaeration of the working fluid in the outer peripheral portion, which is separately hermetically sealed.

The first method of the present invention for producing a heat pipe is as follows.
Is a method for manufacturing a heat pipe, comprising the following steps. Prepare two clad plate members made of at least two different members including a member having excellent compatibility with water, and combine the two members having excellent compatibility with water so as to face each other. On at least one of the clad plate materials, a convex portion protruding outward is formed, a hollow portion, and a container having an outer peripheral portion for forming the hollow portion in an airtight state is prepared, and the outer peripheral portion is formed. Then, the hollow portion is joined so as to be airtight, water or a working fluid containing water as a main component is injected and degassed to manufacture a heat pipe.

According to another aspect of the method for manufacturing a heat pipe of the present invention, the thickness of the member having the largest specific gravity among the thicknesses of the members constituting the clad plate is 1% of the total weight of the clad plate. The method of manufacturing a heat pipe, wherein the clad plate is prepared so as to be not more than / (number of members constituting the clad plate).

In another aspect of the method of manufacturing a heat pipe according to the present invention, each of the two clad members is made of two kinds of metal members, and the metal member is made of a copper member and an aluminum member. A method for manufacturing a heat pipe, wherein each surface of the clad material forming the inner wall of the container is made of the copper member.

In another aspect of the method for manufacturing a heat pipe according to the present invention, one of the two clad members is made of two kinds of metal members including a copper member and an aluminum member. The other clad material of the clad material is made of a copper member, an aluminum member and a copper member, or a metal member of two or three layers composed of a copper member, an aluminum member and a nickel member, and the inner wall of the container is A method of manufacturing a heat pipe, wherein each surface of the clad material to be formed is made of the copper member.

Another aspect of the method for manufacturing a heat pipe according to the present invention is a method for manufacturing a heat pipe, wherein the joining of the outer peripheral portion is performed by welding or bending.

Another aspect of the method for manufacturing a heat pipe according to the present invention is a method for manufacturing a heat pipe, wherein when the outer peripheral portion is joined by the bending, the bending is performed via an airtight auxiliary member.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a heat pipe according to the present invention will be described in detail with reference to the drawings. First, two clad plate members made of at least two different members, one surface of which is made of a member having excellent compatibility with water, will be described.

Each of the two clad members is made of two kinds of metal members, and the metal member may be a clad plate made of a copper member and an aluminum member. Furthermore,
One clad material of the two clad materials is composed of two types of metal members including a copper member and an aluminum member,
The other clad material of the two clad materials may be made of a copper member, an aluminum member and a copper member, or a metal member of two or three layers composed of a copper member, an aluminum member and a nickel member.

A method for manufacturing the above-described clad plate will be described. This method may be a conventionally used method. That is, a clad manufacturing method in which a joining surface of different kinds of metal plates is activated in advance in a vacuum chamber, and then the different kinds of metal plates are overlapped and cold-rolled. Further, in the above-described activation treatment, in a predetermined extremely low-pressure inert gas atmosphere, a metal plate having a bonding surface is set to one electrode A grounded to ground, and a predetermined distance is provided between the electrode A and another electrode B supported and insulated. An AC is applied to cause a glow discharge, and the area of the electrode A exposed in the plasma generated by the glow discharge is sputter-etched at a ratio of the area of the electrode B or less. .

According to the above-described method, no alloy layer is formed at the joining interface, and the joining surface is formed by gas entrainment or
A thin clad sheet material having no joining defects due to metal oxides, strong joining strength, and excellent workability can be obtained.

According to the heat pipe of the present invention, each of the surfaces forming the inner wall of the container having a hollow portion is made of a member having excellent compatibility with water, and is made of at least two different members. Heat pipe provided with a clad plate, an outer peripheral portion as a joining surface of the two clad plates for forming a hollow portion in an airtight state, and water or a hydraulic fluid containing water as a main component sealed in the hollow portion. It is.

FIG. 1 is a perspective view schematically showing a heat pipe container of the present invention. As shown in FIG. 1, provided with a convex portion 4 protruding outward, forming a hollow portion.
For example, one clad plate material 2 made of a copper material and an aluminum material and another clad plate material 3 made of a copper material and an aluminum material are combined together at the joining surface 6, and the outer peripheral portion 10 of the clad plate material is joined. A container 1 is formed. The above-mentioned clad plate 2 and another clad plate 3
Is formed by facing each copper material facing each other, and the inner wall of the container forming the cavity is formed of a copper material having excellent compatibility with water. Further, a part of the convex part 4 is provided with a working fluid inlet 5 for injecting water as a working fluid and deaeration of the container.

FIG. 2 is a sectional view taken along line AA of FIG. FIG.
As shown in FIG. 2, another clad plate 2 made of copper material 8 and aluminum material 16 and a clad plate material 2 made of copper material 9 and aluminum material 17 having convex portions 4 protruding outward forming cavity 11. The container 1 is formed by joining the clad plate 3 together with the joining surface 6 and joining the outer peripheral portion 10 of the clad plate. The above-mentioned clad plate material 2 and another clad plate material 3 are combined with the respective copper materials 8 and 9 facing each other, and the inner wall of the container forming the cavity is made of a copper material having excellent compatibility with water. Formed by In the outer peripheral portion, the copper material 8 of the clad plate material 2
And the copper material 9 of another clad plate material 3 are directly joined by welding or the like.

As described above, in the heat pipe of the embodiment shown in FIGS. 1 and 2, the outer peripheral portions of the two clad plate members are joined by welding or the like. As a result, the part directly in contact with water as the working fluid is formed of a copper material having excellent compatibility with water.

Further, another embodiment of the heat pipe of the present invention will be described. FIG. 3 is a perspective view schematically showing a container according to another embodiment of the heat pipe of the present invention. As shown in FIG. 3, a convex portion 4 that protrudes outward and forms a hollow portion, and water as a working fluid formed in connection with the convex portion is injected to deaerate the container. One clad plate 2 made of, for example, a copper material and an aluminum material, and another clad plate material 3 made of a copper material and an aluminum material, provided with a working liquid inlet 7 for performing the operation, are combined with the joining surface 6 being combined. Then, the outer peripheral portion 10 of the clad plate is joined to form the container 1. The clad plate material 2 described above
And another clad plate material 3 are combined with the respective copper materials 8 and 9 facing each other, and the inner wall of the container forming the hollow portion is formed of a copper material having excellent compatibility with water. The above-mentioned hydraulic fluid inlet 7 forming a part of the outer peripheral portion is separately processed by sealing or the like, so that the hollow portion is hermetically sealed.

As described above, each of the two clad members is made of two kinds of metal members, and the metal members are
It consists of a copper member and an aluminum member. Further, each surface of the clad material forming the inner wall of the container is made of a copper member. As a result, water can be used as the working fluid.

Further, one of the two clad materials described above is composed of two types of metal members consisting of a copper member and an aluminum member, and the other clad material of the two clad materials is a copper member. , An aluminum member and a copper member, or a metal member of two or three layers composed of a copper member, an aluminum member and a nickel member. Even in this case, forming the inner wall of the container,
It is sufficient that each surface of the clad material is made of a copper member.

By using a copper material for the outermost member, soldering when fins are installed on the heat pipe becomes easy. By making the outermost member a nickel material, corrosion and discoloration of the heat pipe can be prevented.

The thickness of the member having the highest specific gravity among the thicknesses of the members constituting the clad plate described above is not more than 1 / (the number of members constituting the clad plate) of the total weight of the clad plate. It is preferred that For example, in the case of a clad plate made of a copper material and an aluminum material, the thickness of the copper material may be １ ／ or less of the total weight of the clad plate. In the case of a clad plate made of a copper material, an aluminum material, or a copper material, the thickness of each copper material may be equal to or less than 1/3 of the total weight of the clad plate material. Further, in the case of a clad plate made of two types and three layers of metal members made of a copper material, an aluminum material and a nickel material, the thickness of the copper material having the largest specific gravity is not more than 1/3 of the total weight of the clad plate material. I just need.

Further, another embodiment of the heat pipe of the present invention will be described. FIG. 4 is a schematic view schematically showing a method of forming a container according to another embodiment of the heat pipe of the present invention. As shown in FIG. 4 (a), for example, provided with a convex part 4 protruding outward forming a hollow part 11, for example,
One clad plate material 2 made of copper material 8 and aluminum material 16 and another clad plate material 3 made of copper material 9 and aluminum material 17 are combined together with joining surfaces 6, and bent to outer peripheral portion 10 of the clad plate material. And the container 1 is formed. The above-mentioned clad plate material 2 and another clad plate material 3 are respectively made of copper materials 8, 9
The inner wall of the container forming the cavity is formed of a copper material having excellent compatibility with water. The bending process described above is performed by bending the outer peripheral portion 10 once and further crimping. FIG. 6 is a perspective view of a heat pipe container formed by bending the outer peripheral portion in this manner. As shown in FIG. 6, another clad plate 3 is bent toward the clad plate 2 and caulked to form an outer peripheral portion 10. According to this method, the mass productivity of the heat pipe is improved.

As shown in FIG. 4B, in the container shown in FIG. 4A, the outer peripheral portion 10 may be bent twice and further crimped. The heat pipe container formed by bending the outer peripheral portion in this manner is the same as the container shown in FIG. That is, as shown in FIG. 6, another clad plate 3 is bent toward the clad plate 2 and caulked to form the outer peripheral portion 10. The airtightness by the bending process is further improved.

Further, another embodiment of the heat pipe of the present invention will be described. FIG. 5 is a schematic view schematically showing a method of forming a container according to another embodiment of the heat pipe of the present invention. As shown in FIG. 5, the heat pipe of this embodiment further includes an airtight auxiliary member 15, and the outer peripheral portion 6 as a joining surface is joined by the bending process via the airtight auxiliary member 15 to form the hollow portion 11. It is formed in an airtight state.
That is, for example, one clad plate 2 made of a copper material 8 and an aluminum material 16 having a convex portion 4 protruding outward and forming a hollow portion 11, and made of a copper material 9 and an aluminum material 17 And another clad plate material 3 whose outer peripheral portion is larger than that of the clad plate material 2 in combination with the joining surface 6, and an airtight auxiliary member 15 such as an adhesive or solder is disposed at the end of the clad plate material 2. The outer peripheral portion 10 of the clad plate material 3 is subjected to bending processing and joined,
A container 1 is formed.

Since the airtight auxiliary member 15 is provided,
The airtightness of the cavity is further improved. Also in this embodiment,
The above-mentioned clad plate material 2 and another clad plate material 3 are combined with the respective copper materials 8 and 9 facing each other, and the inner wall of the container forming the cavity is made of a copper material having excellent compatibility with water. Formed by The bending process described above is performed by bending the outer peripheral portion 10 once and further crimping.
The heat pipe container formed by bending the outer peripheral portion in this manner is as shown in FIG. As shown in FIG. 6, another clad plate 3 is bent toward the clad plate 2 and caulked via an airtight auxiliary member to form an outer peripheral portion 10. Further, in the heat pipe of the present invention, a wick having a capillary force may be provided in the hollow portion.

Further, a method of manufacturing a heat pipe according to the present invention is a method of manufacturing a heat pipe comprising the following steps. That is, two clad plate members made of at least two different members including a member having excellent compatibility with water are prepared, and two members having excellent compatibility with water are combined so as to face each other. On at least one of the clad plate materials, a convex portion protruding outward is formed, a hollow portion, and a container having an outer peripheral portion for forming the hollow portion in an airtight state is prepared. The parts are joined in an airtight state, and water or a working fluid containing water as a main component is injected and degassed to produce a heat pipe. As described above, according to the present invention, it is possible to provide a heat pipe that has desired strength, is lightweight, and can use water as a working fluid and has excellent workability. Furthermore, in the heat pipe of the present invention, the outer peripheral portion is joined,
Alternatively, since the bending process is performed, the flatness of the flat portion as the plate-type heat pipe is maintained.

[0045]

The present invention will be described in more detail with reference to the following examples. Example 1 As shown in FIG. 1, a central portion of a thin clad sheet material having a thickness of 1 mm made of a copper material having a length of 100 mm, a width of 50 mm, a thickness of 0.2 mm, and an aluminum material having a thickness of 0.8 mm was pressed. A thin clad plate material 2 having a projection 4 forming a cavity was prepared. In addition, the same height 100mm,
Copper material of width 50mm, thickness 0.2mm and thickness 0.8m
Thus, a thin clad plate material 3 having a thickness of 1 mm made of an aluminum material having a thickness of 1 m was prepared. The thin clad sheet material 2 thus prepared
As shown in FIG. 2, the thin clad plate material 3 was combined so that the copper material was on the inside, and the joining portion 6 was joined by welding. The air in the cavity of the flat container thus formed was removed, pure water was sealed as a working fluid, and the working fluid inlet was cut off to produce a heat pipe of the present invention. The heat pipe produced in this way has a pressure of 200 kPa
It was strong enough to withstand the internal pressure, was lightweight, and could use water as the working fluid.

Embodiment 2 As shown in FIG. 4 (a), the height is 120 mm and the width is 100 m.
m, a convex portion 4 forming a hollow portion by pressing a central portion of a 0.6 mm thick thin clad plate made of a copper material having a thickness of 0.1 mm and an aluminum material having a thickness of 0.5 mm.
Was prepared. Further, a copper material having a length of 120 mm, a width of 100 mm, a thickness of 0.1 mm and an aluminum material having a thickness of 0.5 mm has a thickness of 0.6 mm.
mm was prepared. The thin clad sheet material 2 and the thin clad sheet material 3 prepared as described above are shown in FIG.
As shown in (a), the copper material is combined so that it is on the inside, and the joining portion 6 is subjected to a bending process once so that the thin clad plate material 3 appears on the surface, and further caulked thereon. A container as shown in FIG. 6 was formed. The air in the cavity of the flat container thus formed is removed, pure water is sealed as a working fluid, and the working fluid inlet is shut off.
The heat pipe of the present invention was manufactured. The heat pipe manufactured in this way can secure airtightness by caulking using a caulking jig, and since the contact part with water can be made only of copper, ensure long-term reliability Was completed.

Embodiment 3 As shown in FIG. 5, the height is 60 mm, the width is 60 mm, and the thickness is 0.3 mm.
A thin clad plate 2 having a convex portion 4 forming a cavity was prepared by pressing a central portion of a 1.0 mm thick thin clad plate made of a 4 mm copper material and a 0.6 mm thick aluminum material. Furthermore, the same copper material of length 60 mm, width 60 mm, thickness 0.4 mm and thickness 0.6 mm
A thin clad plate material 3 having a thickness of 1.0 mm made of an aluminum material was prepared. As shown in FIG. 5, the thin clad sheet material 2 and the thin clad sheet material 3 thus prepared are combined so that the copper material is on the inside, and an adhesive material as an airtight auxiliary material is attached to the end of the joint 6 of the clad plate material 2 Was bent once to cover the thin clad plate 2 with the thin clad plate, and further caulking was performed thereon to form a container as shown in FIG. The air in the cavity of the flat container thus formed was removed, pure water was sealed as a working fluid, and the working fluid inlet was cut off to produce a heat pipe of the present invention. The heat pipe manufactured in this manner was able to secure sufficient airtightness even with caulking with a small pressure, and was able to improve the reliability against leakage.

[0048]

As described above, according to the present invention, a container having desired strength, light weight and excellent workability can be obtained.
A heat pipe capable of using water as a working fluid can be provided, and has high industrial value.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a heat pipe container of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a perspective view schematically showing a container according to another embodiment of the heat pipe of the present invention.

FIG. 4 is a schematic view schematically showing a method of forming a container according to another embodiment of the heat pipe of the present invention.

FIG. 5 is a schematic view schematically showing a method of forming a container according to another embodiment of the heat pipe of the present invention.

FIG. 6 is a perspective view schematically showing another container of the heat pipe of the present invention.

[Explanation of Codes] Container 2. 2. clad sheet material 3. Another clad plate material Convex part 5. Hydraulic fluid inlet 6. Joint surface 7. Working fluid inlet 8. Copper material 9. Copper material 10. Outer periphery 11. Cavity part 16. Aluminum material 17. Aluminum material

Continued on the front page (72) Inventor Masaaki Yamamoto 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F-term (reference) 5F036 AA01 BA08 BA23 BB60 BD01 BD03

Claims (5)

[Claims] 1. Each surface forming the inner wall of a container having a heat pipe cavity having the following members is made of at least two different members made of a member having excellent compatibility with water. Two clad plate members, an outer peripheral portion as a joining surface of the two clad plate members for forming the cavity portion in an airtight state, and water or water mainly contained in the cavity portion enclosed in the cavity portion . 2. The container according to claim 1, wherein each of the two cladding members comprises two types of metal members, wherein the metal members comprise copper members and aluminum members, and form an inner wall of the container. The heat pipe according to claim 1, wherein each surface of the clad material is made of the copper member. 3. The method according to claim 4, further comprising an airtight auxiliary member, wherein an outer peripheral portion serving as the joining surface is bonded by the bending process via the airtight auxiliary member to form the hollow portion in an airtight state. The heat pipe as described. 4. The thickness of the member having the highest specific gravity among the thicknesses of the members constituting the clad plate material is 1 / (the number of members constituting the clad plate material) of the total weight of the clad plate material. The heat pipe according to any one of claims 1 to 5, wherein: 5. A method for producing a heat pipe, comprising the steps of: preparing two clad plates made of at least two different members including a member excellent in compatibility with water; A convex portion protruding outward is formed on at least one of the two clad plate materials in which excellent members are combined so as to face each other, and the hollow portion and the hollow portion are formed in an airtight state. Preparing a container having an outer peripheral part for the outer peripheral part, joining the outer peripheral part so that the hollow part is in an airtight state, injecting water or a hydraulic fluid containing water as a main component, degassing,
Manufacture heat pipes.