HEAT-RADIATING COMPONENT AND METHOD OF MANUFACTURING THE SAME

Abstract

A heat-radiating component includes a wick layer formed on an inner wall of a hermetically sealed container made of metal and a working fluid encapsulated in the hermetically sealed container. In the wick layer, micro carbon fiber is mixed into metal powder. In one aspect, the wick layer is a structure combined by a first wick and a second wick, the first wick being formed of sintered metal powder, and the second wick being a plating layer into which micro carbon fiber is mixed so as to partially fill air space inside the first wick while covering a surface of the first wick. The first wick is preferably a body sintered copper powder, and the second wick is preferably made of a copper plating layer into which carbon nanotube or carbon nanofiber is mixed.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2009-271445, filed on Nov. 30, 2009, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a heat-radiating component and a method of manufacturing the same. More particularly, they relate to a heat-radiating component such as a heat pipe or the like used in cooling a heat-generating component such as a CPU embedded in a personal computer, an electronic device or the like, and also to a method of manufacturing the same.

BACKGROUND

The heat pipe has advantages in that the heat pipe can use CFC-free water for the working fluid (refrigerant), and does not require external power, for example. The heat pipe is widely used as a heat-radiating component for a large capacity power semiconductor (thyristor, diode, power module and the like), an MPU for a computer server, a hermetically sealed chassis for a control panel of a machine tool or the like. The heat pipe is increasingly used as a cooling component for a heat-generating component (a semiconductor element or the like such as a CPU, which is required to operate at higher speed along with higher integration of chips, and which thus generates a large amount of heat) embedded in a small electric device such as a notebook PC.

As heat pipes used in the aforementioned field, heat pipes small in size and diameter become mainly used along with reduction in size of electronic devices. In addition, flat heat pipes have been preferably used. This is because a flat heat pipe can be easily installed onto a component (such as a CPU) to be cooled, and also, a wide contact surface can be obtained.

As a structure of the heat pipe, various types have been proposed heretofore. In the basic structure of a heat pipe, a working fluid (typically, water) encapsulated inside a hermetically sealed pipe is evaporated (latent heat absorption) by externally heating one end (heating portion) of the pipe, and steam thus generated moves to a low temperature portion at the other end of the pipe. Then, the steam is condensed (latent heat release) at this portion, and the condensed working fluid returns to the heating portion along the inner wall of the pipe. The portion along which the working fluid returns (the inner wall of the pipe) is provided with a capillary structure called a “wick.” The wick is provided in various forms including a bundle of metal wires, a metal mesh, grooves and a sintered body of metal powder.

Among the aforementioned forms, a groove heat pipe is the mainstream. The groove heat pipe is excellent in the heat resistance (heat conductivity) of the pipe material itself, but has a problem of being poor in inclination dependency (i.e., heat transportation by the inclined heat pipe is not sufficient) because the capillary force thereof is lower than those of the other types. For example, in a case where the groove heat pipe is embedded in a notebook PC often tilted at the time of usage, the groove heat pipe can transport heat only insufficiently and itself cannot be cooled so much due to its low capillary force. Thus, a sufficient cooling effect cannot be expected.

To solve this problem, a sintered metal heat pipe (a sintered body of copper powder or the like is formed on the inner surface of the pipe) has been developed in recent years. Having a high capillary force, the sintered metal heat pipe is expected as one possible solution for the inclination dependency.

As a technique related to such conventional art, there is an electrically insulated heat pipe described in Patent Document 1 below, for example. In addition, Patent Document 2 below describes a technique for a heat pipe in which water is encapsulated as a heat medium inside a container made of copper or copper alloy, and in which an oxide film with a thickness of a predetermined value or less is formed on a contact surface of the container with the heat medium. In addition, a flat heat pipe described in Patent Document 3 below is cited as an example. Moreover, an example of the technique related to the wick using sintered metal is described in Patent Document 4 described below. Further, as described in Patent Document 5 below, there is a heat pipe using water as the working fluid and having an inner surface formed of Ni-base alloy and plated with Cu.

• Patent Document 1: Japanese Laid-open Patent Publication No. 4-98093
• Patent Document 2: Japanese Laid-open Patent Publication No. 9-113162
• Patent Document 3: Japanese Laid-open Patent Publication No. 2009-180437
• Patent Document 4: Japanese Laid-open Patent Publication No. 2007-56302
• Patent Document 5: Japanese Laid-open Patent Publication No. 7-90534

As described above, the conventional wick structure employing sintered metal uses copper powder as the metal powder to be sintered. Thus, the following problems exist when copper powder is sintered.

First, one of the problems is that the facility cost is high. This is because, for a heat pipe made of copper, for example, sintering in an inert gas (such as nitrogen gas or argon gas) atmosphere needs to be performed under a high temperature (about 900 to 1050° C.). In addition, the pipe material (copper) easily causes crystal grain coarsening and uneven deformation during the sintering. Thus, there arises another problem that a bending process and flattening process performed thereafter is difficult.

Moreover, there is still another problem that it is difficult to obtain an ideal wick layer (wick layer having a high capillary force and a low flow path resistance that allows the working fluid to easily flow through the path) because the average grain size of copper powder in use is approximately the same. Specifically, when the grain size of copper powder is small, a gap between adjacent grains is small. Thus, a high capillary force can be obtained in this case but the circularity of the working fluid deteriorates corresponding to the smallness of the gap. Meanwhile, if the grain size of the copper powder is large, the gap between adjacent grains is large. Thus, the circularity of the working fluid improves in this case but a high capillary force cannot be obtained.

In addition, when metal powder such as copper powder is sintered, air space is formed on crystal grain boundaries of the sintered body (see FIG. 4C). It is generally said that the electric conductivity and heat conductivity of the sintered body are lower than those of a bulk metal (bulk of metal such as copper or the like) with approximately the same size as the sinter body. There is a literature indicating that the heat conductivity of copper powder before being sintered is 0.14 to 0.18 W/(m·K). Accordingly, when a sintered body of metal powder is used for a wick, the heat conductivity of the heat pipe using such wick often is lower than that of a groove heat pipe in which the unpowdered pipe material (copper) is processed.

In the technique disclosed in Patent Document 4 described above, a sintered wick layer of a heat pipe with a good productivity, a high capillary force, and an excellent circularity of working fluid has been proposed. This sintered wick layer of the heat pipe is obtained by heating and sintering, under a reducing atmosphere, an unsintered wick layer formed by using two types of copper powder.

However, the sintered metal is also used as the wick in the technique disclosed herein. Accordingly, it is considered that the heat pipe using this wick is inferior in the heat resistance (heat conductivity) to the groove heat pipe, which is obtained by processing an unpowdered copper material.

SUMMARY

According to one aspect of the invention, there is provided a heat-radiating component including a hermetically sealed container made of metal, a wick layer formed on an inner wall of the hermetically sealed container, and a working fluid encapsulated in the hermetically sealed container, wherein micro carbon fiber is mixed into metal powder in the wick layer.

According to another aspect of the invention, there is provided a method of manufacturing a heat-radiating component which includes a wick layer formed on an inner wall of a hermetically sealed container made of metal and which encapsulates a working fluid in the hermetically sealed container, the method including forming the wick layer, wherein the forming the wick layer includes mixing micro carbon fiber into metal powder.

The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view for explaining operational effects of a heat pipe including a sintered metal wick (capillary structure);

FIG. 2A is a vertical cross-sectional view showing a configuration of a heat pipe according to an embodiment, FIG. 2B is an enlarged cross-sectional view of a portion (evaporating portion) in FIG. 2A, and FIG. 2C is an enlarged cross-sectional view of a portion (wick layer) denoted by reference sign A in FIG. 2B;

FIG. 3A is a view for explaining effects obtainable by the heat pipe illustrated in FIGS. 2A to 2C in comparison with the case of a related art (FIG. 3B);

FIG. 4A is a vertical cross-sectional view showing a configuration of a heat pipe according to a modification of the embodiment illustrated in FIGS. 2A to 2C, FIG. 4B is an enlarged cross-sectional view of a portion (wick layer) denoted by reference sign A in FIG. 4A, and FIG. 4C is an enlarged cross-sectional view of a portion (sintered wick layer) denoted by reference sign B in FIG. 4A; and

FIG. 5A is a diagram showing an application example of a vapor chamber according to another embodiment, FIG. 5B is a vertical cross-sectional view showing a configuration of the vapor chamber in FIG. 5A, and FIG. 5C is an enlarged cross-sectional view of a portion (wick layer) denoted by reference sign A in FIG. 5B.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preliminary matters for a better understanding of embodiments are described before explaining the embodiments.

(Preliminary Matters; See FIG. 1)

FIG. 1 is a diagram showing an example of a heat pipe including a sintered metal wick (capillary structure). In the illustrated heat pipe 10, a hermetically sealed metal pipe 12 has a shape processed into a flat shape in a cross-sectional view. In addition, a sintered wick layer 14 is formed on an inner wall surface of the metal pipe 12. Further, an appropriate amount of water 16 (vaporized water W1 illustrated by white ∘ and condensed water W2 illustrated by black •, which are schematically expressed at the molecular level in the illustrated example) is vacuum encapsulated in the metal pipe 12 as the working fluid.

While the heat pipe 10 functions, the working fluid (water 16) is externally heated and thus evaporated at one end (evaporating portion at the left end portion in the illustrated example), and then, steam W1 of the evaporated working fluid moves to the other end (condensing portion at the right end portion) in the pipe 12. Then, the steam W1 is condensed at the condensing portion. In addition, the condensed water W2 moves to the one end via the wick layer 14 on the inner wall surface of the pipe 12. Thus, the working fluid refluxes in the pipe 12 by repeating the aforementioned movement.

The sintered wick layer 14 formed on the inner wall surface of the metal pipe 12 is obtained by, for example, depositing copper powder to a required thickness on a surface of a metal plate made of copper or copper alloy (metal plate before being subjected to a bending process, flattening process and the like to form the metal plate into a required metal pipe shape) and then heating and sintering the resultant object. Here, when viewed microscopically, the cross-sectional structure of the sintered wick layer 14 has a structure in which grains of copper powder grain having the approximately same average grain size are partially in contact with each other as if pebbles are stacked (see FIG. 4C, for example). In other words, a gap (air space) exists between grains (of copper powder).

As described above, in the wick structure using the sintered metal according to the current technique, copper powder is used as the metal powder to be sintered. Accordingly, there arise various problems described above when the powder is sintered.

Hereinafter, the embodiments are described.

First Embodiment

FIGS. 2A to 2C are diagrams showing a configuration of a heat pipe according to an embodiment. FIG. 2A shows a vertical cross-sectional structure of the heat pipe 20. FIG. 2B shows an enlarged cross-sectional structure of a portion (evaporating portion) in FIG. 2A. FIG. 2C shows an enlarged cross-sectional structure of a portion (wick layer 24) denoted by reference sign A in FIG. 2B.

The heat pipe 20 according to this embodiment includes a hermetically sealed metal pipe 22 as illustrated. The metal pipe 22 has a shape processed into a flat shape in a cross-sectional view. The wick layer 24 (capillary structure) is formed on an inner wall surface of the metal pipe 22. Further, a working fluid is vacuum encapsulated in the metal pipe 22 as the heat medium.

As the material of the metal pipe 22, a material excellent in heat conductivity is preferable, and copper or copper alloy (such as low-oxygen copper or oxygen-free copper, for example) is preferably used. In this case, an appropriate amount of water is sealed inside the metal pipe 22 as the working fluid. In particular, pure water such as ion exchange water or distilled water is preferred in that such water is unlikely to cause an electrochemical reaction. Although not illustrated in FIGS. 2A to 2C, the working fluid (water) refluxes in the pipe as illustrated in FIG. 1, while the heat pipe 20 functions. Specifically, the working fluid moves inside the metal pipe 22 from one end (evaporating portion) to the other end (condensing portion), and then moves from the other end (condensing portion) to the one end (evaporating portion) via the wick layer 24, thus refluxing in the pipe 22 by repeating the aforementioned movement thereafter.

Note that, the material of the metal pipe 22 is not limited to copper or copper alloy as a matter of course, and other materials can be used as appropriate.

The wick layer 24 formed on the inner wall surface of the metal pipe 22 has a structure in which two types of wicks are combined. A first wick is a copper powder sintered body (sintered wick layer) 26 obtained by sintering copper powder. A second wick is a copper plating layer 28a in which carbon nanotube (CNT) or carbon nanofiber (CNF) 28b is mixed. This copper plating layer 28a in which CNT (or CNF) 28b is mixed is hereinafter referred to as a “CNT mixed copper plating wick layer 28,” or simply, “plating wick layer 28” for the sake of convenience.

The sintered wick layer 26 (first wick) is equivalent to the sintered metal wick formed by using the current technique (sintered wick layer 14 of FIG. 1). Accordingly, when the cross-sectional structure of the sintered wick layer 26 is viewed microscopically, the sintered wick layer 26 has a structure in which grains of copper powder 26a having the approximately same average grain size are partially in contact with each other as if pebbles are stacked (see FIG. 4C, for example). In other words, air space exists between the grains (copper powder 26a).

The CNT mixed copper plating wick layer 28 (second wick) is formed by applying, copper plating in which CNT (or CNF) is mixed, onto the surface of the sintered wick layer 26 as described later. As illustrated in FIG. 2C, this plating wick layer 28 is formed to cover the surface of the sintered body (surface portion of the sintered wick layer 26) while filling the air space inside the sintered wick layer 26. When the plating wick layer 28 is formed, adjustment is important such that the plating wick layer 28 fills the air space inside the sintered wick layer 26 not completely but partially.

In the example illustrated in FIG. 2C, the state where the air space in the copper powder sintered body 26 is completely filled with the plating wick layer 28 is illustrated. However, slight air space is left in part of the air space, actually. Such slight air space is left in the wick layer 24 to maintain a required capillary force.

Next, a method of forming the wick layer 24 in particular is described in a method of manufacturing the heat pipe 20 of the embodiment.

As one method, a metal plate having a size necessary for forming the metal pipe 22 is first prepared. Specifically, what is prepared here is a metal plate before being subjected to a bending process, flattening process and the like to be formed into a required shape as the metal pipe 22 in which a working fluid is eventually encapsulated and hermetically sealed. As the material of this metal plate, copper or copper alloy excellent in heat conductivity is preferably used.

Next, copper powder is deposited on one of surfaces of the metal plate (copper plate) to a required thickness. Then, the resultant object is heated and sintered. Accordingly, the sintered wick layer (copper powder sintered body) 26, which is the first wick, is formed (the state illustrated in FIG. 4C).

Next, copper plating in which CNT (or CNF) is mixed is applied onto the surface of the sintered wick layer 26. Accordingly, the CNT mixed copper plating, wick layer 28, which is the second wick layer, is formed (the state illustrated in FIG. 2C).

As the plating solution used for forming the plating wick layer 28, a copper plating solution in which CNT (or CNF) is dispersed by using protein as a dispersing agent is preferably used, for example. Here, use of protein (gelatin, collagen peptide or the like) as a dispersing agent improves the dispersibility of CNT, thus enabling an improvement in the flatness of the plating film to be formed (achieving uniform film thickness). In addition, application of ultrasonic wave in dispersing CNT (or CNF) further enables the improvement in the dispersibility.

When the CNT mixed copper plating is applied onto the copper powder sintered body (sintered wick layer) 26, the copper plating solution also enters the air space inside the copper powder sintered body 26 (copper plating layer 28a is formed on the surfaces of the copper powder 26a) as illustrated and functions so as to fill the air space. However, if the air space is completely filled, the capillary force of the wick layer 24 is reduced.

Accordingly, when the CNT mixed copper plating is applied, the plating time needs to be appropriately adjusted such that the air space inside the copper powder sintered body 26 is partially filled (specifically, slight air space to maintain sufficient capillary force is left). For example, when the size of a grain of the copper powder 26a is 100 μm, the thickness of the plating (plating wick layer 28) applied to the surface of the sintered body is set approximately equal to or less than 30 μm.

While the heat pipe 20 of the embodiment functions, the heat generated in the metal pipe 22 due to the heat supplied from the outside (from a semiconductor element generating heat such as a CPU) is conducted to the working fluid (water in this case) in the metal pipe 22 via the wick layer 24 (structure in which the sintered wick layer 26 and the CNT mixed copper plating wick layer 28 are combined). Accordingly, the water in the corresponding portion (evaporating portion) inside the pipe 22 is evaporated. Then, the steam moves to the low temperature portion (condensing portion), which is at the end opposite from the evaporating portion inside the pipe 22, and is then condensed at the low temperature portion. Moreover, the condensed water returns to the one end via the wick layer 24 on the inner wall surface of the pipe 22 and then refluxes in the pipe 22 by repeating the aforementioned movement.

As described above, with the heat pipe 20 according to this first embodiment and the method of manufacturing the same, the CNT mixed copper plating wick layer 28 is formed on the copper powder sintered body (sintered wick layer) 26 formed on the inner wall surface of the metal pipe 22 as follows. Here, the CNT mixed copper plating wick layer 28 is formed to partially fill the air space (gaps between grains of the copper powder 26a) inside the copper powder sintered body 26 while covering the surface portion thereof by use of the copper plating solution in which CNT (or CNF) is dispersed. Thus, the size of the air space inside the copper powder sintered body 26 can be reduced.

In other words, the size of the air space can be easily controlled by appropriately changing the thickness of the plating wick layer 28 in accordance with the grain size of the copper powder 26a. During the process, the plating wick layer 28 is formed to partially fill the air space instead of completely filling the air space (slight air space to maintain sufficient capillary force is left). Thus, high capillary force and good circularity of the working fluid can be maintained.

The copper powder sintered body in the state of the art has a problem that heat conductivity is low as compared with the case of a bulk type due to the presence of a large number of gaps (air space) as illustrated in FIG. 3B. On the other hand, in the structure of the heat pipe 20 (wick layer 24) of the embodiment, the copper plating solution (copper plating layer 28) enters the air space (gaps between grains of the copper powder 26a) inside the copper powder sintered body 26 and then partially fills the air space as illustrated in FIG. 3A. Accordingly, the structure having high capillary force and excellent circularity of the working fluid is implemented.

In addition, the CNT (or CNF) 28b having a heat conductivity equal to or greater than that of diamond is mixed (dispersed) into the plating wick layer 28 (copper plating solution). Thus, the heat conductivity of the wick layer 24 as a whole can be increased. Although depending on the amount of the CNT (or CNF) 28b to be mixed, an increase of approximately 10 to 20% of the heat conductivity can be expected as compared with the case illustrated in FIG. 1. Here, the heat conductivity of the CNT is around 3000 W/(m·K) while the heat conductivity of the CNF is around 1200 W/(m·K).

In the aforementioned embodiment, an example of the case where the wick layer 24 (structure in which the copper powder sintered wick layer 26 and the CNT mixed copper plating wick layer 28 are combined) is formed over the entire inner wall surface of the metal pipe 22 is described. However, as apparent from the gist of the invention, the wick layer 24 does not have to be necessarily formed over the entire inner wall surface of the pipe 22. Basically, any configuration is sufficient if a temperature gradient sufficient to cause the working fluid (water in this case) to reflux is formed in the pipe 22.

FIGS. 4A to 4C show an example of such a configuration, and illustrate a configuration of a heat pipe according to a modification of the embodiment illustrated in FIGS. 2A to 2C. Here, FIG. 4A shows a vertical cross-sectional structure of the heat pipe 20a. FIG. 4B shows an enlarged cross-sectional structure of a portion (wick layer 24) denoted by reference sign A in FIG. 4A. FIG. 4C shows an enlarged cross-sectional structure of a portion (sintered wick layer 26) denoted by reference sign B in FIG. 4A.

As compared with the configuration of the heat pipe 20 (FIGS. 2A to 2C) of the aforementioned embodiment, the heat pipe 20a according to this modification is different in that the wick layer 24 is formed only at positions on the inner wall surface of the metal pipe 22 respectively corresponding to the portions where the heat pipe 20a exchanges heat with the outside (evaporating portion and condensing portion respectively at both end portions of the pipe). In addition, the heat pipe 20a is different in that only the copper powder sintered body (sintered wick layer 26) is formed in the other portions of the inner wall surface of the metal pipe 22. The other configuration of the heat pipe 20a is the same as in the case of the embodiment illustrated in FIGS. 2A to 2C. Accordingly, the description thereof is omitted herein.

A method of manufacturing the heat pipe 20a is basically the same as the method used in the aforementioned embodiment. In this modification, the copper powder sintered body (sintered wick layer 26) is first formed on the surface of the required metal plate (metal plate before being subjected to a bending process, flattening process and the like to form the metal plate into a required shape as the hermetically sealed metal pipe) in the same manner as the aforementioned embodiment (see FIG. 4C). However, an appropriate mask (plating resist) is then used to cover a portion on the sintered wick layer 26 except for the positions corresponding to both end portions of the pipe (evaporating portion and condensing portion), and the CNT mixed copper plating is applied onto the portion not covered by the resist to form the plating wick layer 28 (see FIG. 4B). Thus, the wick layer 24 is formed only at the corresponding positions (positions corresponding to the evaporating portion and the condensing portion at both end portions of the pipe, respectively) on the inner wall surface of the metal pipe 22.

Second Embodiment

In the aforementioned embodiments, described is an example of the case where the wick layer 24 is formed of a combined structure including the first wick (sintered wick layer 26) of sintered metal type and the second wick formed of the plating layer in which CNT or the like is mixed (CNT mixed copper plating wick layer 28), and the second wick is formed by a wet process using plating. However, the method of forming the wick layer 24 is not limited only to this as a matter of course. The method to be described below is another example of the method.

In the second embodiment, a dry process is used to form a sintered wick layer (wick layer in which CNT (or CNF) is mixed) corresponding to the aforementioned wick layer 24. A technique (Japanese Laid-open Patent Publication No. 2005-343749) previously proposed by the applicant of this application can be used for the method of forming the CNT mixture by sintering.

First, copper powder and CNT are evenly mixed by use of a fast gas mixture technique. In this process, the processing atmosphere is preferably an inert gas (such as nitrogen gas or argon gas), and the powder flow rate is preferably set to 50 to 400 Km/H.

Next, the mixture of the copper powder and CNT formed by the aforementioned technique is sintered by using copper pulse electric current sintering with the mixture pressed, by the amount of pressure not to destroy the copper powder, against and thus put in close contact with one of surfaces of a required copper plate (copper plate before being subjected to a bending process, flattening process and the like to form the copper plate into a required shape as the metal pipe 22 in which a working fluid is eventually encapsulated and hermetically sealed). Thus, the sintered wick layer (wick layer in which CNT is mixed) is formed. In this process, it is preferable that a vacuum gas or nitrogen gas is used as the processing atmosphere, the temperature of the processing atmosphere is between approximately 400 to 1050° C., and pulse current is used as the conduction method.

In the case of using the method according to the second embodiment, the plating process as described in the aforementioned embodiment does not have to be performed, and all the processes are performed in dry condition. Accordingly, the oxidization of copper or the like is reduced, and a sintered wick layer with high quality and high reliability can be formed.

Furthermore, the aforementioned embodiments are described by taking the heat pipes 20 and 20a (FIGS. 2A to 2C and 4A to 4C) as examples of the form of heat-radiating component. However, the form of the heat-radiating component is not limited to the examples. For example, the invention is applicable to a vapor chamber which is called a heat-sink type heat pipe.

FIGS. 5A to 5C show an example of such a vapor chamber. FIG. 5A shows an application example of a vapor chamber 30. FIG. 5B shows a vertical cross-sectional structure of the vapor chamber 30. FIG. 5C shows an enlarged cross-sectional structure of a portion (wick layer 24) denoted by reference sign A in FIG. 5B.

The vapor chamber 30 is arranged between a semiconductor element (chip) 40 such as a CPU and a heat sink 42 as illustrated in FIG. 5A. The chip 40 and the heat sink 42 are each bonded to the vapor chamber 30 via an adhesive such as an epoxy-base resin having high heat conductivity.

As compared with the configuration of the heat pipe 20 (FIGS. 2A to 2C) of the aforementioned embodiment, the vapor chamber 30 is only different in that the vapor chamber 30 includes a metal container 32 instead of the metal pipe 22 as illustrated in FIG. 5B. In addition, the internal structure of the vapor chamber 30 is the same as the internal structure of the heat pipe 20. Thus, the description of the structure is omitted herein.

As illustrated, the vapor chamber 30 efficiently cools the CPU 40 by widely dispersing the heat generated from the CPU 40 into the heat sink 42 having a large cooling area. The amount of heat generation of an electronic device such as the CPU 40 is expected to increase in the future as the performance of such an electronic device further increases. Thus, the vapor chamber 30 is quite effectively used to cool such an electronic device.

In addition to the aforementioned type of the vapor chamber in which the heat sink 42 is provided on top of the vapor chamber 30, the types of vapor chambers include one provided with a heat fin on top of a vapor chamber, one provided with a heat pipe, and the like. In any types of the vapor chambers, heat exchange can be efficiently performed between a heat-generating component (semiconductor element such as a CPU) and a heat-radiating component (such as a heat sink, heat fin or heat pipe).

All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.

Claims

1. A heat-radiating component comprising:

a hermetically sealed container made of metal;

a wick layer formed on an inner wall of the hermetically sealed container; and

a working fluid encapsulated in the hermetically sealed container,

wherein micro carbon fiber is mixed into metal powder in the wick layer.

2. The heat-radiating component according to claim 1, wherein the wick layer is a structure combined by a first wick and a second wick, the first wick being formed of sintered metal powder, and the second wick being a plating layer into which micro carbon fiber is mixed so as to partially fill air space inside the first wick while covering a surface of the first wick.

3. The heat-radiating component according to claim 2, wherein the first wick is a body sintered copper powder, and the second wick is formed of a copper plating layer into which carbon nanotube or carbon nanofiber is mixed.

4. The heat-radiating component according to claim 2, wherein the wick layer is formed at least at a position on the inner wall of the hermetically sealed container, the position corresponding to a portion where the heat-radiating component exchanges heat with outside.

5. The heat-radiating component according to claim 1, wherein the wick layer is a sintered wick layer formed by sintering copper powder into which carbon nanotube or carbon nanofiber is mixed.

6. The heat-radiating component according to claim 5, wherein the wick layer is formed at least at a position on the inner wall of the hermetically sealed container, the position corresponding to a portion where the heat-radiating component exchanges heat with outside.

7. The heat-radiating component according to claim 1, wherein the micro carbon fiber is carbon nanotube or carbon nanofiber.

8. The heat-radiating component according to claim 1, wherein the working fluid is water.

9. A method of manufacturing a heat-radiating component which includes a wick layer formed on an inner wall of a hermetically sealed container made of metal and which encapsulates a working fluid in the hermetically sealed container, the method comprising forming the wick layer,

wherein the forming the wick layer includes mixing micro carbon fiber into metal powder.

10. The method of manufacturing a heat-radiating component, according to claim 9, wherein the forming the wick layer includes:

forming a first wick by depositing and then sintering metal powder on one of surfaces of a metal plate before being formed into a required shape as the hermetically sealed container; and

forming, by use of a plating solution in which micro carbon fiber is dispersed, a second wick so as to partially fill air space inside the first wick while covering a surface portion of the first wick.

11. The method of manufacturing a heat-radiating component, according to claim 10, wherein copper powder is used as the metal powder in the forming of the first wick, and a copper plating solution in which carbon nanotube or carbon nanofiber is dispersed is used in the forming of the second wick.

12. The method of manufacturing a heat-radiating component, according to claim 9, wherein the forming the wick layer includes forming a sintered wick layer through a dry process by sintering a mixture of copper powder and carbon nanotube or carbon nanofiber with the mixture put in close contact with one of surfaces of a metal plate before being formed into a required shape as the hermetically sealed container.

13. The method of manufacturing a heat-radiating component, according to claim 12, wherein the dry process includes:

uniformly mixing the copper powder and the carbon nanotube or carbon nanofiber by a fast gas mixture technique; and

sintering the mixture through copper pulse electric current sintering with the mixture pressed against and put in close contact with the one of surfaces of the metal plate.