HEAT TRANSPORT DEVICE, ELECTRONIC APPARATUS, AND HEAT TRANSPORT MANUFACTURING METHOD

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat transport device thermally connected to a heat source of an electronic apparatus, an electronic apparatus including the heat transport device, and a heat transport device manufacturing method.

2. Description of the Related Art

A heat transport device such as a heat spreader, a heat pipe, or a CPL (Capillary Pumped Loop) has been used as a device thermally connected to a heat source of an electronic apparatus, such as a CPU (Central Processing Unit) of a PC (Personal Computer), to absorb and diffuse heat of the heat source. For example, a solid-type metal heat transport device made of for example a copper plate is known, and a heat transport device including a working fluid has been proposed recently.

It is known that nanomaterials such as carbon nanotube are high in thermal conductivity and contribute to acceleration of evaporation. As a heat transport device using carbon nanotube, a heat pipe is known (see, for example, U.S. Pat. No. 7,213,637; column 3, line 66 to column 4, line 12, FIG. 1, hereinafter referred to as Patent Document 1).

SUMMARY OF THE INVENTION

Carbon nanotube has a high thermal conductivity. However, because carbon nanotube has a nanostructure, compared to a case where a flow path or the like for a working fluid is made of a metal plate or the like having a flat surface, a friction resistance and a pressure loss are large. Then, there is a fear that the working fluid does not flow in a heat transport device properly, and as a result, heat transport is not performed properly.

In view of the above-mentioned circumstances, it is desirable to provide a heat transport device realizing higher heat transport efficiency, and an electronic apparatus including the heat transport device. It is further desirable to provide a heat transport device manufacturing method that realizes easier manufacture with higher reliability.

According to an embodiment of the present invention, there is provided a heat transport device including a working fluid, an evaporation portion, a condenser portion, a flow path portion, a concave portion, and a protrusion portion. The evaporation portion causes the working fluid to evaporate from a liquid phase to a vapor phase. The condenser portion communicates with the evaporation portion, and causes the working fluid to condense from the vapor phase to the liquid phase. The flow path portion causes the working fluid condensed in the condenser portion to the liquid phase to flow to the evaporation portion. The concave portion is provided on at least one of the evaporation portion and the flow path portion, in which the liquid-phase working fluid flows. The protrusion portion is made of nanomaterial protruding from an inner wall side surface of the concave portion such that the protrusion portion partially covers an opening surface of the concave portion.

According to the embodiment of the present invention, the nanomaterial may be carbon nanotube.

According to this embodiment, the protrusion portion is made of nanomaterial having a large specific surface area to thereby accelerate evaporation of the working fluid and realize higher heat transport efficiency. In the case where the protrusion portion is made of carbon nanotube having a high thermal conductivity, evaporation of the liquid-phase working fluid is further accelerated, and the heat transport device transports heat more efficiently.

In addition, since the protrusion portion is made of carbon nanotube protruding from the inner wall side surface of the concave portion, the liquid-phase working fluid flowing in the concave portion comes less in contact with an extremely minute tip portion of the protrusion portion made of carbon nanotube and having an extremely minute nanostructure. So, a friction resistance of the liquid-phase working fluid flowing in the concave portion and the protrusion portion and a pressure loss are suppressed. As a result, the heat transport device transports heat more efficiently.

According to the embodiment of the present invention, the opening surface of the concave portion may have a vapor flow path in which the vapor-phase working fluid flows, the vapor flow path being free from the protrusion portion. The protrusion portion, a bottom surface of the concave portion facing the protrusion portion, and the inner wall side surface of the concave portion may form a liquid flow path in which the liquid-phase working fluid flows.

According to the embodiment of the present invention, the concave portion may be groove-like.

According to this embodiment, the liquid-phase working fluid flows in the liquid flow path including the protrusion portion made of carbon nanotube. Since the liquid-phase working fluid comes in contact with the protrusion portion made of carbon nanotube, the high thermal conductivity of the carbon nanotube accelerates evaporation of the liquid-phase working fluid. The heat transport device thus transports heat more efficiently.

In a case where the protrusion portions are provided on the inner wall side surfaces facing to each other of the groove-like concave portion, a plurality of liquid flow paths are formed in the concave portion. Flow and evaporation of the liquid-phase working fluid are thus further accelerated. The heat transport device thus transports heat more efficiently.

Further, the opening surface of the concave portion may have a vapor flow path in which the vapor-phase working fluid flows, the vapor flow path being free from the protrusion portion. Accordingly, the vapor-phase working fluid evaporated in the liquid flow path flows to the condenser portion via the flow path without being blocked by the protrusion portion provided on the concave portion. Flow and condensation of the liquid-phase working fluid are thus accelerated, and the heat transport device thus transports heat more efficiently.

According to an embodiment of the present invention, there is provided an electronic apparatus including a heat source and a heat transport device thermally connected to the heat source. The heat transport device includes a working fluid, an evaporation portion, a condenser portion, a flow path portion, a concave portion, and a protrusion portion. The evaporation portion causes the working fluid to evaporate from a liquid phase to a vapor phase. The condenser portion communicates with the evaporation portion and causes the working fluid to condense from the vapor phase to the liquid phase. The flow path portion causes the working fluid condensed in the condenser portion to the liquid phase to flow to the evaporation portion. The concave portion is provided on at least one of the evaporation portion and the flow path portion, in which the liquid-phase working fluid flows. The protrusion portion is made of nanomaterial protruding from an inner wall side surface of the concave portion such that the protrusion portion partially covers an opening surface of the concave portion.

According to this embodiment, in the heat transport device, since the protrusion portion is made of nanomaterial protruding from the inner wall side surface of the concave portion, the liquid-phase working fluid flowing in the concave portion comes preferentially in contact with a portion of the protrusion portion not as minute as a tip portion, and comes less in contact with the tip portion of the protrusion portion having an extremely minute nanostructure. So, a friction resistance of the liquid-phase working fluid flowing in the concave portion and the protrusion portion and a pressure loss are suppressed. As a result, the heat transport device thus transports heat more efficiently.

According to an embodiment of the present invention, there is provided a method of manufacturing a heat transport device including an evaporation portion causing a working fluid to evaporate from a liquid phase to a vapor phase, a condenser portion causing the working fluid to condense from the vapor phase to the liquid phase, and a flow path portion causing the liquid-phase working fluid to flow to the evaporation portion. A concave portion is formed on a first base member. A protrusion portion made of nanomaterial is produced on an inner wall side surface of the concave portion of the first base member such that the protrusion portion partially covers an opening surface of the concave portion to obtain a second base member being at least one of the evaporation portion and the flow path portion. A container is formed with at least the second base member. The working fluid is introduced to the container and the container is sealed.

According to this embodiment, in the case where nanomaterial is produced so as to protrude from the inner wall side surface of the concave portion to form the protrusion portion, the liquid-phase working fluid comes preferentially in contact with a portion of the protrusion portion not as minute as a tip portion, and comes less in contact with the tip portion of the protrusion portion having an extremely minute nanostructure. So, a friction resistance of the liquid-phase working fluid and the protrusion portion and a pressure loss are suppressed. As a result, the heat transport device thus capable of transporting heat efficiently can be easily manufactured with higher reliability.

In the heat transport device manufactured by this method, in a case where the protrusion portions are provided on the inner wall side surfaces of the groove-like concave portion that face to each other, a plurality of flow paths are formed in the concave portion. Flow and evaporation of the liquid-phase working fluid are thus further accelerated. The heat transport device thus transports heat more efficiently.

Further, the opening surface of the concave portion has a vapor flow path in which the vapor-phase working fluid flows, the vapor flow path being free from the protrusion portion. Accordingly, the vapor-phase working fluid evaporated in the liquid flow path flows to the condenser portion via the flow path without being blocked by the protrusion portion provided on the concave portion. Flow and condensation of the liquid-phase working fluid are thus accelerated. The heat transport device made by this method thus transports heat more efficiently.

According to the heat transport device of the embodiments of the present invention, higher heat transport efficiency is realized. According to the heat transport device manufacturing method of the embodiment of the present invention, easier manufacture and higher reliability are realized.

These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of best mode embodiments thereof, as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view showing a heat spreader of a first embodiment of the present invention, the heat spreader being thermally connected to a heat source;

FIG. 2 is a plan view showing the heat spreader;

FIG. 3 is an exploded perspective view showing the heat spreader;

FIG. 4 is a schematic sectional view showing the heat spreader taken along the line A-A of FIG. 2;

FIG. 5 is a partially enlarged perspective view showing an evaporation portion;

FIG. 6 is a partially enlarged perspective view showing protrusion portions;

FIG. 7 is a sectional view showing liquid refrigerant flow paths in a groove portion;

FIG. 8 is a schematic diagram showing the operation of the heat spreader;

FIG. 9 is a flowchart showing a manufacturing method of the heat spreader;

FIG. 10 are schematic diagrams showing in sequence an injection method of a refrigerant into a container;

FIG. 11 is a sectional view showing a heat spreader according to a second embodiment of the present invention;

FIG. 12 is a partial perspective view showing an evaporation portion;

FIG. 13 are schematic diagrams showing a production method of protrusion portions on wires;

FIG. 14 is an exploded perspective view of a heat spreader according to a third embodiment of the present invention;

FIG. 15 is a partially exploded perspective view showing flow path plate members;

FIG. 16 is a partial perspective view showing an evaporation portion of a heat spreader of a fourth embodiment of the present invention;

FIG. 17 are schematic diagrams showing a production method of protrusion portions on a mesh; and

FIG. 18 is a perspective view showing a desktop PC as an electronic apparatus including the heat spreader.

DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the following embodiments, description will be made while employing a heat spreader as a heat transport device.

First Embodiment

(Structure of Heat Spreader 1)

FIG. 1 is a side view showing a heat spreader 1 of a first embodiment of the present invention, the heat spreader being thermally connected to a heat source. FIG. 2 is a plan view showing the heat spreader 1 of FIG. 1.

As shown in FIGS. 1-2, the heat spreader 1 includes a container 2. The container 2 includes a heat reception plate 4 (first base member), a heat radiation plate 3, and sidewalls 5. The heat radiation plate 3 is provided so as to face the heat reception plate 4. The sidewalls 5 tightly bond the heat reception plate 4 and the heat radiation plate 3.

The heat radiation plate 3, the heat reception plate 4, and the sidewalls 5 may be bonded by brazing, that is, welded, or may be bonded with an adhesive material depending on the materials. The heat radiation plate 3, the heat reception plate 4, and the sidewalls 5 are made of a metal material, for example. The metal material is for example, copper having a high thermal conductivity, stainless steel, or aluminum, but not limited to the above. Other than the metal material, a material having a high thermal conductivity such as carbon may be employed. All of the heat radiation plate 3, the heat reception plate 4, and the sidewalls 5 may be formed of different materials respectively, two of them may be formed of the same material, or all of them may be made of the same material.

A heat source 50 is thermally connected to the heat reception plate 4. The phrase “thermally connected” means, in addition to direct connection, connection via a thermal conductor, for example. The heat source 50 is, for example, an electronic component that generates heat such as a CPU (Central Processing Unit) or a resistor, or an electronic apparatus such as a display. Heat from the heat source 50 is transmitted to the heat spreader 1 via the heat reception plate 4.

A heat radiation member such as a heat sink 55 is thermally connected to the heat radiation plate 3. Heat transmitted from the heat spreader 1 to the heat sink 55 is radiated from the heat sink 55.

The container 2 further includes a refrigerant (working fluid, shown in FIGS. 6-7) sealed therein. The refrigerant may be prepared by adding a small amount of an organic compound bearing a hydroxyl group (OH group) to pure water. Specific examples of the organic compound bearing a hydroxyl group added to pure water include alcohols, diols, polyols, and phenols. More specific examples of the organic compound bearing a hydroxyl group include alcohols such as methanol, ethanol, propanol, butanol, and hexanol, diols such as ethylene glycol and propylene glycol, polyols such as glycerin, and phenols such as phenol and alkylphenol.

Alternatively, as the refrigerant, pure water with no alcohols added, chlorofluorocarbon, hydrochlorofluorocarbon, fluorine, ammonia, acetone, or the like may be used, but not limited to the above.

FIG. 3 is an exploded perspective view showing the heat spreader 1. FIG. 4 is a schematic sectional view showing the heat spreader 1 taken along the line A-A of FIG. 2.

The heat reception plate 4 includes a heat reception surface 41 and an evaporation surface 42 (evaporation portion). The heat reception surface 41 corresponds to an outer surface of the container 2. The evaporation surface 42 is a back surface of the heat reception surface 41, and faces the heat radiation plate 3.

A heat source 50 is thermally connected to the heat reception surface 41.

An area surrounding the evaporation surface 42 is a bond area 43 for bonding the sidewalls 5. An evaporation portion 7 is provided on the evaporation surface 42. The evaporation portion 7 causes a liquid-phase refrigerant (hereinafter referred to as “liquid refrigerant”) to evaporate.

An inner space of the container 2 mainly serves as the flow path 6 for the liquid refrigerant and the vapor-phase refrigerant (hereinafter referred to as “vapor refrigerant”). That is, in the flow path 6, the liquid refrigerant flows from the heat radiation plate 3 side to the heat reception plate 4 side by gravity, and the vapor refrigerant flows from the heat reception plate 4 side to the heat radiation plate 3 side.

The heat radiation plate 3 includes a heat radiation surface 31 and a condenser surface 32 (condenser portion). The heat radiation surface 31 corresponds to an outer surface of the container 2. The condenser surface 32 is a back surface of the heat radiation surface 31, and faces the heat reception plate 4.

The condenser surface 32 causes the vapor refrigerant evaporated in the evaporation portion 7 to condense.

A heat radiation member such as a heat sink 55 is thermally connected to the heat radiation surface 31.

Inner walls of the sidewalls 5 constitute a capillary flow path 51 (flow path portion). The capillary flow path 51 is a flow path for the liquid refrigerant condensed on the condenser surface 32 of the heat radiation plate 3. That is, in the capillary flow path 51, the liquid refrigerant flows from the heat radiation plate 3 side to the heat reception plate 4 side by a capillary force and gravity.

Note that in FIG. 4, for easier understanding, the shapes of the members are changed from the actual configuration. For example, the scale ratio of the evaporation portion 7 to the heat spreader 1 is made larger than the actual configuration. Hereinafter, for easier understanding, the shapes of the members may also be changed from the actual configuration.

The heat spreader 1 of this embodiment is substantially square in a plan view. The heat spreader 1 has about 30-50 mm length (e) (see FIG. 2) on each side, for example. The heat spreader 1 is substantially rectangular in the side view. The heat spreader 1 has about 2-5 mm height (h) (see FIG. 1), for example. The heat spreader 1 having such a size is for a CPU of a PC (Personal Computer) as the heat source 50 thermally connected to the heat spreader 1. The size of the heat spreader 1 may be defined in accordance with the size of the heat source 50. For example, in a case where the heat source 50 thermally connected to the heat spreader 1 is a large-capacity heat source of a large-sized display or the like, the length e is needed to be made larger and may be as large as about 2600 mm. The size of the heat spreader 1 is defined such that the refrigerant can flow and condense appropriately, that is, the cycle of evaporation and condensation of the refrigerant flowing in the container 2 can be repeated smoothly. The operating temperature range of the heat spreader 1 is for example −40° C. to +200° C., approximately. The endothermic density of the heat spreader 1 is for example 8W/mm²or lower.

(Structure of Evaporation Portion 7)

FIG. 5 is a partially enlarged perspective view showing the evaporation portion 7 provided on the evaporation surface 42 of the heat reception plate 4. FIG. 6 is a partially enlarged perspective view showing protrusion portions 75 provided on groove portions 71 of the evaporation portion 7.

As shown in FIGS. 5-6, the evaporation portion 7 includes a plurality of groove portions 71 (concave portion) and protrusion portions 75. The groove portions 71 are formed on the evaporation surface 42 of the heat reception plate 4. The protrusion portions 75 are provided on the groove portions 71. Specifically, the evaporation portion 7 has the following structure.

A plurality of linear groove portions 71 are formed on the evaporation surface 42 of the heat reception plate 4 (second base member). The groove portions 71 are formed such that the liquid refrigerant flow in the groove portions 71 in the longitudinal direction by a capillary force. The groove portion 71 has a rectangular concave section. The groove portion 71 has a bottom surface 72 and a pair of inner wall side surfaces 73 facing to each other. Note that the groove portion 71 may have a rectangular section or a square section.

The bottom surface 72 of the groove portion 71 is formed in parallel or substantially in parallel to the evaporation surface 42 of the heat reception plate 4. In the rectangular section, a width of the bottom surface 72 is, for example, about 10 μm to 1 mm. A depth of the groove portion 71 is, for example, about 10 μm to 1 mm.

Note that the groove portion 71 may have a rectangular concave section as described above, or may have a V-shape section, a semicircle section, a rounded rectangular section, or a rounded V-shape section. The plurality of groove portions 71 are formed in parallel as shown in the drawings, but not limited to the above. The groove portions 71 may be arbitrarily arranged as long as the refrigerant can flow in the entire groove portions 71 uniformly. For example, the plurality of groove portions may be concentric circles or concentric polygons. Alternatively, one or more groove portions may be spiral. Alternatively, concentric circle grooves, concentric polygon grooves, or spiral grooves and radial grooves may be provided so as to cross each other. Alternatively, grid-like grooves may be provided.

The protrusion portions 75 are provided on the inner wall side surfaces 73, respectively, in a protruding manner. The protrusion portions 75 partially cover an opening portion of the groove portion 71 from the inner wall side surface 73 sides. The protrusion portions 75 are provided at positions (area) of the inner wall side surfaces 73 apart from the bottom surface 72 such that a space is formed between the protrusion portions 75 and the bottom surface 72 of the groove portion 71. In FIG. 5, the protrusion portions 75 are provided on the entire area in the longitudinal direction (Y axis direction) of the groove portion 71. Alternatively, the protrusion portions 75 may be provided on part of the groove portion 71.

The protrusion portion 75 is made of a nanomaterial. Examples of the nanomaterial include carbon nanotube, carbon nanowire, and the like. In this embodiment, the protrusion portion 75 is made of a carbon nanotube array.

A protrusion length of the protrusion portion 75 is defined such that a space portion 76 (vapor flow path) is provided between tip end portions of the protrusion portions 75 protruding from the pair of the inner wall side surfaces 73. The space portion 76 is a zone where the opening surface of the groove portion 71 is not covered with the protrusion portions 75. The vapor refrigerant in the groove portion 71 flows to the flow path 6 via the space portion 76.

Most of the vapor refrigerant generated in the groove portion 71 of the evaporation portion 7 flows to the flow path 6 in the container 2 via the space portion 76 of the groove portion 71. The vapor refrigerant then flows to the heat radiation plate 3. Note that some of the vapor refrigerant flows to the flow path 6 through gaps in the densely-grown carbon nanotube array constituting the protrusion portions 75.

Note that carbon nanotube is superhydrophobic to pure water. So, in a case of using pure water as the refrigerant, a capillary force may not be exhibited enough. So, according to a composition of the refrigerant to be used, the surface of the protrusion portion 75 is desirably reformed so as to improve wetting ability. Examples of the surface reform treatment include introduction of hydrophilic group such as carboxyl group with ultraviolet treatment. As a result, the wetting ability of the surface of the protrusion portion 75 and the capillary force are improved.

For example, the ultraviolet treatment is performed as follows. An excimer lamp (light intensity of lamp tube surface is 50 mW/cm², for example) of wavelength 172 nm is prepared. A carbon nanotube array as the protrusion portion 75 is arranged 2 mm below the excimer lamp. The surface of the protrusion portion 75 is irradiated with ultraviolet in the atmosphere to reform the surface. The irradiation time is 1 minute, for example. With the ultraviolet treatment, active oxygen or ozone is generated from oxygen in the atmosphere to oxidize the carbon nanotube array. Hydrophilic group such as carboxyl (COOH) group having hydrophilicity is thus formed on the surface of the protrusion portion 75.

Next, flow of the refrigerant in the groove portions 71 of the evaporation portion 7 having the above-mentioned structure will be described.

FIG. 7 is a sectional view showing liquid refrigerant flow paths in the groove portion 71.

As shown in FIG. 7, a liquid refrigerant R in the container 2 of the heat spreader 1 flows in the groove 71 in the longitudinal direction by the capillary force in the evaporation portion 7. At that time, the liquid refrigerant R flows in two liquid refrigerant flow paths 74 (liquid flow path) by the capillary force. The liquid refrigerant flow paths 74 are formed at both end portions of the groove portion 71 in the width direction. Each of the liquid refrigerant flow paths 74 is formed by the inner wall side surface 73, the protrusion portion 75, and the bottom surface 72. The liquid refrigerant R receives heat from the heat reception plate 4 and evaporates to be a vapor refrigerant. The protrusion portion 75 is made of a carbon nanotube array having a high thermal conductivity. So, the protrusion portion 75 transmits heat to the liquid refrigerant R as effectively as the heat reception plate 4. In addition, the protrusion portion 75 ensures a much larger contact area with the liquid refrigerant R as compared to a metal material of a similar size. As a result, the heat spreader 1 can transmit a larger amount of heat.

The two liquid refrigerant flow paths 74 are formed in the groove portion 71 so as to face to each other. A surface of the liquid refrigerant R in the liquid refrigerant flow path 74, the surface facing the inner wall side surface 73, becomes a meniscus surface M by a surface tension. So, in the liquid refrigerant flow path 74, a contact area of the liquid refrigerant R with the protrusion portion 75 and the bottom surface 72 is made larger. Further, thin liquid film zones F are formed in which evaporation of the liquid refrigerant R is accelerated.

In this embodiment, a carbon nanotube array is formed on the inner wall side surface 73 of the groove portion 71 in parallel or substantially in parallel to the bottom portion 72 to form the protrusion portion 75. In general, a carbon nanotube array gradually becomes minute toward a tip portion thereof. In a case where the carbon nanotube array coming in contact with the liquid refrigerant R is too minute, a friction resistance of flow of the liquid refrigerant R along the groove portion 71 is increased. As a result, the liquid refrigerant R may not flow in the evaporation portion 7 properly. In this embodiment, since the carbon nanotube array is produced on the inner wall side surface 73 of the groove portion 71 in parallel or substantially in parallel to the bottom portion 72 to form the protrusion portion 75, the portion of the carbon nanotube array not as minute as the tip portion comes preferentially in contact with the liquid refrigerant R. Accordingly, the liquid refrigerant R can flow in the evaporation portion 7 properly.

Generally, the capillary force causing the liquid refrigerant R to flow in the liquid refrigerant flow path 74 is larger as the meniscus radius is smaller. However, there is a limitation to make the flow path width smaller in a case of forming grooves by a general method such as cutting or etching. There is thus a limitation to make the meniscus radius smaller. Further, in a case of forming flow paths having a small width on a plate member made of a metal material or the like for the heat reception plate, a flow amount of the liquid refrigerant R is decreased and the evaporation efficiency may be decreased.

To the contrary, according to this embodiment, the nanomaterial is produced on the inner wall side surface 73 of the groove portion 71 to form the protrusion portion 75. The liquid refrigerant flow path 74 having the small meniscus radius is thus formed in the groove portion 71. In addition, the two liquid refrigerant flow paths 74 are formed in the one groove portion 71. Accordingly, the capillary force is increased without making the groove width of the groove portion 71 smaller, and the flow amount of the liquid refrigerant R is not decreased.

In this embodiment, the carbon nanotube array is produced on the inner wall side surface 73 of the groove portion 71 in parallel or substantially in parallel to the bottom portion 72 of the groove portion 71 to form the protrusion portion 75. However, the shape of the groove portion 71 and the production direction of the carbon nanotube array are not limited to the above. For example, the carbon nanotube array may protrude in a direction including a component in a direction toward the heat radiation plate 3. In this case, the contact area of the protrusion portion 75 and the liquid refrigerant R is increased to thereby further accelerate evaporation. Further, thin liquid film zones F are made larger to thereby further accelerate evaporation. Note that this configuration is also applicable to the following embodiments to the same effect.

In this embodiment, the groove portions 71 and the protrusion portions 75 are only provided on the evaporation surface 42 of the heat reception plate 4, but not limited to the above. For example, on the capillary flow path 51 of the sidewalls 5 (first base member), linear grooves may be formed in a direction in which the evaporation surface 42 of the heat reception plate 4 and the condenser surface 32 of the heat radiation plate 3 communicate with each other. Protrusion portions similar to the protrusion portions 75 may be provided on the grooves (second base member). Accordingly, flow of the liquid refrigerant condensed on the condenser surface 32 of the heat radiation plate 3 to the evaporation surface 42 of the heat reception plate 4 by the capillary force is accelerated. Note that this configuration is also applicable to the following embodiments to the same effect.

(Operation of Heat Spreader 1)

FIG. 8 is a schematic diagram showing the operation of the heat spreader 1.

As shown in FIG. 8, when the heat source 50 generates heat, the heat reception surface 41 of the heat reception plate 4 receives the heat. Then, the liquid refrigerant flows by the capillary force in the groove portions 71 of the evaporation portion 7 provided on the evaporation surface 42 of the heat reception plate 4 (arrow A). Specifically, the liquid refrigerant flows by the capillary force in the two liquid refrigerant flow paths 74 facing to each other formed in the groove portion 71. The liquid refrigerant in the liquid refrigerant flow paths 74 receives heat and evaporates to be the vapor refrigerant. Some of the vapor refrigerant flows in the groove portions 71 of the evaporation portion 7, but most of the vapor refrigerant flows in the flow path 6 mainly via the space portion 76 formed between the protrusion portions 75 facing to each other to the heat radiation plate 3 side (arrow B). As the vapor refrigerant flows in the flow path 6, the heat diffuses, and the vapor refrigerant condenses on the condenser surface 32 of the heat radiation plate 3 to be the liquid phase (arrow C). Thus, the heat diffused by the heat spreader 1 is transferred from the heat radiation surface 31 of the heat radiation plate 3 to the heat sink 55. The heat sink 55 radiates the heat (arrow D). The liquid refrigerant flows in the capillary flow path 51 by the capillary force or in the flow path 6 by gravity to return to the groove portions 71 of the evaporation portion 7 (arrow E). By repeating the above operation, the heat spreader 1 transports the heat of the heat source 50.

The operational zones as shown by the arrows A to E are merely rough guide or rough standard and not clearly defined since respective operational zones may be shifted according to the amount of heat generated by the heat source 50 or the like.

(Manufacturing Method of Heat Spreader 1)

A manufacturing method of the heat spreader 1 of this embodiment will be described.

FIG. 9 is a flowchart showing a manufacturing method of the heat spreader 1.

The groove portions 71 are formed on the evaporation surface 42 of the heat reception plate 4 (first base member) by cutting or etching (Step 101).

Next, a catalyst layer (not shown) such as an iron, nickel, or cobalt layer is formed on an upper portion of the inner wall side surface 73 of the groove portion 71. Carbon nanotube is densely produced on the catalyst layer to thereby form the carbon nanotube array as the protrusion portion 75 (Step 102). The carbon nanotube array is formed in parallel to the bottom surface 72, for example. In the provision of the catalyst layer, a resist may be applied and reversed. The carbon nanotube array may be produced on the catalyst layer by plasma CVD (Chemical Vapor Deposition) or thermal CVD, but not limited to the above. The surface of the protrusion portion 75 may be reformed by an ultraviolet treatment to improve hydrorophilicity.

Next, the heat reception plate 4 having the groove portions 71 and the protrusion portions 75 (second base member), the sidewalls 5, and the heat radiation plate 3 are bonded to form the container 2 (Step 103). In the bonding, the respective members are precisely aligned.

Next, the refrigerant is injected into the container 2 and the container 2 is sealed (Step 104).

FIG. 10 are schematic diagrams showing in sequence the injection method of the refrigerant into the container 2.

The heat reception plate 4 includes an injection port 45 and an injection path 46.

As shown in FIG. 10A, the pressure of the flow path 6 is decreased via the injection port 45 and the injection path 46, for example, and the refrigerant is injected into an inner flow path from a dispenser (not shown) via the injection port 45 and the injection path 46.

As shown in FIG. 10B, a press area 47 is pressed and the injection path 46 is closed (temporal sealing). The pressure of the flow path 6 is decreased via another injection path 46 and another injection port 45, and when the pressure of the flow path 6 reaches a target pressure, the press area 47 is pressed and the injection path 46 is closed (temporal sealing).

As shown in FIG. 10C, on a side closer to the injection port 45 than the press area 47, the injection path 46 is closed by laser welding for example (final sealing). Accordingly, the inner space of the heat spreader 1 is sealed tightly. By injecting the refrigerant into the container 2 and sealing the container 2 as described above, the heat spreader 1 is manufactured.

Next, the heat source 50 is mounted on the heat reception surface 41 of the heat reception plate 4 (Step 105). In a case where the heat source 50 is a CPU, the process is for example a reflow soldering processing. The reflow processing and the manufacturing processing of the heat spreader 1 may be executed in different areas (for example different factories). So, in the case of executing the injection of the working fluid after the reflow processing, it is necessary to transport the heat spreader 1 to and from the factories, which leads to problems of cost, manpower, time, or generation of particles of the transfer between factories. According to this manufacturing method, it is possible to execute the reflow processing after the completion of the heat spreader 1, solving the above problem.

According to the above-mentioned manufacturing method, in Step 102, the carbon nanotube is densely produced on the upper portion of the inner wall side surface 73 of the groove portion 71 to thereby form the carbon nanotube array as the protrusion portion 75. The liquid refrigerant flow path 74 forming the meniscus surface M having a small meniscus radius is thus formed without processing a groove having a small width.

In addition, the carbon nanotube array forming the protrusion portion 75 is formed in parallel or substantially in parallel to the bottom surface 72. So, the liquid refrigerant R flowing in the liquid refrigerant flow path 74 comes preferentially in contact with the portion of the carbon nanotube array not as minute as the tip portion, and comes less in contact with the minutest tip portion of the carbon nanotube array. So, a friction resistance of the liquid refrigerant R and the protrusion portion 75 and a pressure loss are suppressed.

In addition, when the carbon nanotube is densely produced on the upper portion of the inner wall side surfaces 73 of the groove portion 71 to thereby form the carbon nanotube arrays, the space portion 76 through which the vapor refrigerant flows is easily formed between the protrusion portions 75 facing to each other. For example, in a case where a portion corresponding to the protrusion portion 75 is made by a metal plate or the like, it is necessary to laminate plate members on the heat reception plate 4 and form pores by etching or the like to thereby form the space portion 76. To the contrary, according to the manufacturing method of this embodiment, by controlling the protrusion length of the carbon nanotube array, the protrusion portion 75 and the space portion 76 each having a predetermined shape are formed without performing a fine processing.

Second Embodiment
Structure of Heat Spreader 11

FIG. 11 is a sectional view showing a heat spreader 11 according to a second embodiment of the present invention.

Hereinafter, components, functions, and the like similar to those of the heat spreader 1 of the first embodiment will be attached with similar reference symbols, the description will be simplified or omitted, and different part will mainly be described.

The heat spreader 11 includes a container 12. The container 12 includes a heat reception plate 14, a heat radiation plate 13, and sidewalls 15. The heat radiation plate 13 is provided so as to face the heat reception plate 14. The sidewalls 15 tightly bond the heat reception plate 14 and the heat radiation plate 13. The container 12 further includes a refrigerant sealed therein. An inner space of the container 12 mainly serves as a flow path 16 for the refrigerant.

The heat reception plate 14 includes a heat reception surface 141, an evaporation surface 142, and a bond area 143. A heat source is thermally connected to the heat reception surface 141. An evaporation portion 17 is provided on the evaporation surface 142.

The heat radiation plate 13 has a structure same as that of the heat radiation plate 3, and includes a heat radiation surface 131 and a condenser surface 132. A heat radiation member such as a heat sink is thermally connected to the heat radiation surface 131. Inner surfaces of the sidewalls 15 constitute a capillary flow path 151.

(Structure of Evaporation Portion 17)

FIG. 12 is a partial perspective view showing the evaporation portion 17 provided on the evaporation surface 142 of the heat reception plate 14.

As shown in FIG. 12, the evaporation portion 17 includes a plurality of wires 171 and protrusion portions 175. The wires 171 are provided on the evaporation surface 142 of the heat reception plate 14. The protrusion portions 175 are provided on the wires 171. Note that in FIG. 12, for easier understanding, five wires 171 are shown.

The wire 171 is made of a material having a high thermal conductivity such as a metal material or carbon. Examples of the metal material include copper, stainless steel, and aluminum. The wires 171 are arranged spaced apart and in parallel, and bonded to the evaporation surface 142 of the heat reception plate 14 by brazing, that is, welded, or may be bonded with an adhesive material. One wire 171, another wire 171 next to the one wire 171, and the evaporation surface 142 constitute a portion corresponding to the groove portion 71 (concave portion) of the first embodiment. The wire 171 may have a circular section, but not limited to the above. The wire 171 may alternatively have a polygonal section. Further, according to a protrusion direction of the carbon nanotube forming the protrusion portion 175, the wire 171 may be processed appropriately and the shape of the wire 171 may be changed arbitrarily.

A carbon nanotube array is produced at a portion of the wire 171 apart from the evaporation surface 142 such that the carbon nanotube arrays respectively produced on the adjacent wires 171 face to each other, to thereby form the protrusion portions 175. The protrusion portions 175 face to each other via a space portion 176. The protrusion portions 175 facing to each other via the space portion 176 partially cover a space between the adjacent two wires 171 arranged spaced apart and in parallel.

In the evaporation portion 17, the protrusion portions 175, circumferential surfaces of the wires 171, and the evaporation surface 142 of the heat reception plate 14 form liquid refrigerant flow paths 174. The liquid refrigerant flows in the liquid refrigerant flow paths 174 in the longitudinal direction of the liquid refrigerant flow path 174, that is, in the longitudinal direction of the wire 171, by the capillary force. The liquid refrigerant flowing in the liquid refrigerant flow path 174 has a meniscus surface. Further, thin liquid film zones are formed in the vicinity of the meniscus surface. In the thin liquid film zones, the evaporation of the liquid refrigerant is accelerated.

The heat spreader 11 having the above structure operates in the similar manner as the heat spreader 1.

(Manufacturing Method of Heat Spreader 11)

Next, a manufacturing method of the heat spreader 11 of this embodiment will be described. Specifically, a production method of the protrusion portions 175 on the wires 171 will be described, which is different from the manufacturing method of the heat spreader 1 of the first embodiment.

FIG. 13 are schematic diagrams showing the production method of the protrusion portions 175 on the wires 171.

As shown in FIG. 13A, two portions of the wire 171 symmetrical about a center of a circular section are pressed at a predetermined angle. The two portions of the wire 171 are arranged so as to face the heat radiation plate 13. The wire 171 may alternatively be processed by cutting or the like.

FIG. 13B shows the processed wires 171. In FIG. 13B, surfaces 177 and 178 are formed on the wire 171. The surfaces 177 face to each other via the center of the section of the wire 171. The surfaces 178 are orthogonal to the surfaces 177. On the surface 177 formed on the wire 171, a catalyst layer (not shown) such as an iron, nickel, or cobalt layer is formed by vapor deposition or spattering. Carbon nanotube is densely produced on the catalyst layer to thereby form the carbon nanotube array being the protrusion portion 175.

FIG. 13C shows the protrusion portion 175 thus formed. The wires 171 having the protrusion portions 175 and the evaporation surface 142 of the heat reception plate 14 are bonded by brazing, that is, welded, or bonded with an adhesive material.

The evaporation portion 17 is thus formed on the evaporation surface 142 of the heat reception plate 14. Thereafter, the heat spreader 11 only needs to be manufactured by the manufacturing method of the heat spreader 1.

Third Embodiment
Structure of Heat Spreader 21

FIG. 14 is an exploded perspective view of a heat spreader 21 according to a third embodiment of the present invention.

The heat spreader 21 includes a container 22. The container 22 includes a heat reception plate 24, a heat radiation plate 23, and bond areas 281 of a plurality of flow path plate members 28. The heat radiation plate 23 is provided so as to face the heat reception plate 24. The container 22 further includes a refrigerant sealed therein.

The heat reception plate 24 has a structure same as the structure of the heat reception plate 4. The heat reception plate 24 includes a heat reception surface 241, an evaporation surface 242, and a bond area 243.

The bond area 243 is bonded to the bond areas 281 of the plurality of flow path plate members 28.

An evaporation portion 27 having a structure same as the evaporation portion 7 is provided on the evaporation surface 242.

A heat source is thermally connected to the heat reception surface 241.

The heat radiation plate 23 has a structure same as the structure of the heat radiation plate 3. The heat radiation plate 23 includes a heat radiation surface 231 and a condenser surface 232. A heat radiation member such as a heat sink is thermally connected to the heat radiation surface 231.

The plurality of flow path plate members 28 are laminated between the heat reception plate 24 and the heat radiation plate 23 and form flow paths 26 for the refrigerant. The number of the flow path plate members 28 are arbitrarily changed according to an amount of heat generated from the heat source thermally connected to the heat reception surface 241 of the heat reception plate 24.

FIG. 15 is a partially exploded perspective view showing the flow path plate members 28.

Hereinafter, in describing each of the plurality of flow path plate members 28, each member will be referred to as “flow path plate member 28a”, “flow path plate member 28b”, or the like.

As shown in FIG. 15, the flow path plate member 28 has a structure similar to the structure of the heat reception plate 4 having the evaporation portion 7. The flow path plate member 28 further has openings 282, which is different from the heat reception plate 4.

The flow path plate member 28 has the bond area 281 and linear groove portions 291 (concave portion). The bond area 281 is provided in a circumferential portion of one surface of the flow path plate member 28. The groove portions 291 have a rectangular section, are formed in parallel to each other, and are provided on the entire area of the surface of the flow path plate member 28 excluding the bond area 281. The groove portion 291 includes a bottom surface 292 and an inner wall side surface 293. A protrusion portion 295 is provided on the entire area in the longitudinal direction of an upper portion of the inner wall side surface 293 of the groove portion 291. The protrusion portions 295 face to each other via a space portion. Between the protrusion portion 295 and the bottom surface 292 of the groove portion 291, a liquid refrigerant flow path similar to the liquid refrigerant flow path 74 is formed. The liquid refrigerant flows in the liquid refrigerant flow path in the longitudinal direction of the liquid refrigerant flow path, that is, in the longitudinal direction of the groove portion 291, by the capillary force.

A plurality of openings 282 are provided on the bottom surface 292 of the groove portion 291 formed on the flow path plate member 28. The openings 282 penetrate the flow path plate member 28, and are provided at regular intervals along the longitudinal direction of the groove portion 291.

The plurality of flow path plate members 28 are laminated with each other such that the linear groove portions 291a provided on one flow path plate member 28a and the linear groove portions 291b provided on another flow path plate member 28b next to the one flow path plate member 28a are orthogonal to each other. That is, the plurality of flow path plate members 28 are laminated with each other such that the flow path plate members 28 are rotated by 90 degrees in the XY plane. The plurality of openings 282a provided on the bottom surface 292a of the groove portion 291a and the plurality of openings 282b provided on the bottom surface 292b of the groove portion 291b respectively penetrate with each other in the Z axis direction. The plurality of openings 282a and the plurality of openings 282b respectively communicate with each other from the evaporation surface 242 of the heat reception plate 24 to the condenser surface 232 of the heat radiation plate 23 in the Z direction, to thereby form the flow paths 26 for the vapor refrigerant. The liquid refrigerant condensed on the condenser surface 232 of the heat radiation plate 23 flows on the surfaces of the flow path plate members 28 by the capillary force to thereby return to the evaporation portion 27 of the heat reception plate 24. Alternatively, penetrating holes may be provided in the vicinity of the bond areas 281 of the flow path plate members 28 to thereby form a return flow path accelerating the flow of the liquid refrigerant to the evaporation portion 27.

The heat reception plate 24, the plurality of flow path plate members 28, and the heat radiation plate 23 laminated with each other are diffusion-bonded. The heat spreader 21 is thus formed. In laminating, the respective plate members are precisely aligned. In the diffusion bonding, metal binding occurs. The strength or stiffness of the heat spreader 21 is thus improved.

The heat spreader 21 having the above structure operates in the similar manner as the heat spreader 1.

In this embodiment, the flow path plate member 28 has the structure same as the structure of the heat reception plate 4 of the first embodiment except for the provision of the openings 282. So, the flow path plate member 28 has two liquid refrigerant flow paths in each linear groove portion 291. Accordingly, the number of the liquid refrigerant flow paths is increased and the thin liquid film zones of the liquid refrigerant flowing in the liquid refrigerant flow paths are made larger to thereby accelerate evaporation.

Fourth Embodiment

A heat spreader 31 according to a fourth embodiment of the present invention includes a container. The container includes a heat reception plate, a heat radiation plate, and sidewalls. The heat radiation plate is provided so as to face the heat reception plate. The sidewalls tightly bond the heat reception plate and the heat radiation plate. The container further includes a refrigerant sealed therein. An inner space of the container mainly serves as the flow path for the refrigerant. On the heat reception plate of the heat spreader 31, no groove is formed. An evaporation portion 37 is provided on a heat reception surface of the heat reception plate.

(Structure of Evaporation Portion 37)

FIG. 16 is a partial perspective view showing the evaporation portion 37 of the heat spreader 31 of the fourth embodiment of the present invention.

As shown in FIG. 16, the evaporation portion 37 includes a mesh 371 and protrusion portions 375. The protrusion portions 375 are provided on the mesh 371.

The mesh 371 is a mesh of wires 379 made of a material having a high thermal conductivity such as a metal material or carbon. Examples of the metal material include copper, stainless steel, and aluminum. The mesh 371 is bonded to the evaporation surface of the heat reception plate by brazing, that is, welded, or bonded with an adhesive material. The mesh 371 and the evaporation surface form a concave portion. The wire 379 may have a circular section or a polygonal section, but not limited to the above. According to a protrusion direction of the protrusion portions 375, the mesh 371 may be processed appropriately and the shape of the mesh 371 may be changed arbitrarily.

The protrusion portions 375 are provided on predetermined portions of the mesh 371. For example, carbon nanotube arrays are formed on the predetermined portions of the mesh 371 in parallel to the evaporation surface of the heat reception plate such that the carbon nanotube arrays face to each other. The protrusion portions 375 are thus formed.

In the evaporation portion 37, the protrusion portions 375, circumferential surfaces of the wires 379 of the mesh 371, and the evaporation surface of the heat reception plate form liquid refrigerant flow paths. That is, two liquid refrigerant flow paths facing to each other are formed between the two wires 379 arranged spaced apart and in parallel in the X axis direction. Further, two liquid refrigerant flow paths facing to each other are formed between the two wires 379 arranged spaced apart and in parallel in the Y axis direction. In addition, carbon nanotube is produced in parallel to the evaporation surface of the heat reception plate to thereby form the carbon nanotube array being the protrusion portion 375. So, the liquid refrigerant permeated the mesh 371 comes less in contact with the tip portion of the carbon nanotube array. So, a friction resistance of the liquid refrigerant and the protrusion portion 375 and a pressure loss is suppressed. Accordingly, the heat spreader 31 of this embodiment operates in the similar manner as the heat spreader 1.

Note that the plurality of meshes 371 each having the protrusion portions 375 may be laminated with each other. In this case, openings 371a of one mesh 371 and openings 371a of another mesh 371 penetrate with each other in the Z axis direction. That is, the plurality of openings 371a communicate with each other from the evaporation surface of the heat reception plate to the condenser surface of the heat radiation plate in the Z direction, to thereby form the flow paths for the vapor refrigerant. Further, the liquid refrigerant condensed on the condenser surface of the heat radiation plate flows on the surfaces of the meshes 371 and the protrusion portions 375 by the capillary force to thereby return to the evaporation portion of the heat reception plate.

(Manufacturing Method of Heat Spreader 31)

Next, a manufacturing method of the heat spreader 31 will be described. Specifically, a production method of the protrusion portions 375 on the mesh 371 will be described, which is different from the manufacturing method of the heat spreader 1 of the first embodiment.

FIG. 17 are schematic diagrams showing the production method of the protrusion portions 375 on the mesh 371.

The mesh 371 of FIG. 17A is pressed from a side facing the heat radiation plate at a predetermined angle.

FIG. 17B shows the processed mesh 371. In FIG. 17B, surfaces 377 and 378 are formed on the wires 379 of the mesh 371. The surfaces 377 face to each other via the diameter of the section of the wire 379 of the mesh 371. The surfaces 378 are orthogonal to the surfaces 377. On the surface 377 formed on the wire 379, a catalyst layer (not shown) such as an iron, nickel, or cobalt layer is formed by vapor deposition or spattering. Carbon nanotube is densely produced on the catalyst layer to thereby form the carbon nanotube array being the protrusion portion 375.

FIG. 17C shows the protrusion portions 375 thus formed. In FIG. 17C, the plurality of protrusion portions 375 are provided in the X and Y directions. The mesh 371 having the protrusion portions 375 and the evaporation surface of the heat reception plate are bonded by brazing, that is, welded, or bonded with an adhesive material. Thereafter, the heat spreader 31 only needs to be manufactured by the manufacturing method of the heat spreader 1.

(Electronic Apparatus)

FIG. 18 is a perspective view showing a desktop PC 120 as an electronic apparatus including the heat spreader 1.

In a case 121 of the PC 120, a circuit board 122 is provided, and a CPU 123, for example, as a heat source is mounted on the circuit board 122. The CPU 123 is thermally connected to the heat spreader 1 (11, 21, 31), and the heat spreader 1 (11, 21, 31) is thermally connected to a heat sink.

The embodiments according to the present invention are not limited to the embodiments described above, and various modifications are conceivable.

As a heat transport device, the heat spreader is exemplarily shown. However, the heat transport device is not limited to the above, but may be a heat pipe or a CPL.

The shape of the heat spreader 1 (11, 21, 31) is square in a plan view. However, the shape in a plan view may be circular, ellipsoidal, polygonal, or another arbitrary shape.

As an electronic apparatus, the desktop PC is exemplarily shown, but not limited to the above. As an electronic apparatus, a laptop PC, a PDA (Personal Digital Assistance), an electronic dictionary, a camera, a display apparatus, an audio/visual apparatus, a projector, a mobile phone, a game apparatus, a robot apparatus, or another electronic appliance may be employed.

The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2009-091215 filed in the Japan Patent Office on Apr. 3, 2009, the entire content of which is hereby incorporated by reference.

HEAT TRANSPORT DEVICE, ELECTRONIC APPARATUS, AND HEAT TRANSPORT MANUFACTURING METHOD

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CPC

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Abstract

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Priority Claims (1)