JP4467338B2 - Heat pipe manufacturing method - Google Patents

Description

The present invention relates to a process for the preparation of suitable non Topaipu to cool the heat source to be mounted in a small and thin electronic device.

Conventionally, this kind of heat pipe, as in Patent Document 1 In example embodiment, the wick, provided inside the container enclosing the working medium, the heat by Ri work dynamic medium is evaporated, and the dynamic its vapor flow and you condensed Unishi.
Japanese Patent No. 3408033

In the above structure, year by year thin electronic equipment for mounting the heat pipe, Ri your amount of heat generated by the heat source is increased, or to increase the shape of the container, in order to use several of the heat pipe, in the original advantage thin electronic equipment A certain degree of mobility was impaired, and there was a problem that the user could not be satisfied in terms of size and weight.

  Therefore, in view of the above problems, the present invention can effectively cool the heat source without increasing the container shape or using a plurality of heat pipes, and further has excellent heat transfer performance. It is an object of the present invention to provide a method for manufacturing a heat pipe that can form a stable oxide film and can uniformly generate an oxide film having a desired thickness.

In the invention of claim 1, inside the container copper or Dogo gold In example embodiment, has a thickness of more than 30nm on the inner surface of the wick in contact with pure water, constantly improving the hydrophilicity of the wick and pure water since the oxide film is formed to keep the can wettability of the wick and the working medium is significantly improved, to maintain a constantly good wettability. Therefore, it is possible to reduce the use number of compact or heat pipe container shape. Further, an improved spread of the work moving medium, the inner surface of the wick in contact with the working medium in the container, the thermal resistance between the evaporating section and the condensing part of the working medium is reduced, the heat transfer performance superior heat Can provide pipes.

Even if an oxide film having a thickness exceeding 100 nm is formed, the hydrophilicity between the wick and pure water is not further improved, and it becomes difficult to form a stable oxide film. Therefore, in order to always keep the hydrophilicity of the wick and pure water good and form a stable oxide film, the film thickness is preferably 100 nm or less.

In addition, while heating the container at a temperature between 150 ° C. and 200 ° C., it is possible to uniformly generate an oxide film having a desired thickness simply by supplying dry air to the container for 10 minutes to 30 minutes. .

  Since the present invention is as described above, the following effects can be obtained.

According to the first aspect of the present invention, the wettability between the wick and pure water can be remarkably improved and the heat source can be effectively cooled without enlarging the container shape or using a plurality of heat pipes. Become. Moreover , the spread of pure water is improved, and a heat pipe with excellent heat transfer performance can be provided. Furthermore, by making the film thickness 100 nm or less, a stable oxide film can be formed, and dry air is supplied to this container for 10 to 30 minutes while heating the container at a temperature between 150 ° C. and 200 ° C. As a result, an oxide film having a desired thickness can be uniformly formed.

  Hereinafter, preferred embodiments of the heat pipe and the manufacturing method thereof according to the present invention will be described with reference to the accompanying drawings.

  1 to 6 show a first embodiment of the present invention. FIG. 1 is an external view of a heat pipe before bending, and FIG. 2 is for mounting on a notebook personal computer which is a thin electronic device. It is an external view of the heat pipe after performing a bending crushing process. 3 is a cross-sectional view of the crushed portion in FIG. 2, and FIG. 4 is an enlarged cross-sectional view of the main portion.

  In each said figure, the hollow cylindrical container 2 used as the main-body part of the heat pipe 1 is preferably formed from a metal pipe material such as copper or a copper alloy having a high thermal conductivity. Moreover, in the state before the bending process shown in FIG. 1, the container 2 is entirely linear, and the outer diameter and the wall thickness are formed uniformly over the entire length in the axial direction except for the ends. Furthermore, sealing portions 2A and 2B are formed at both ends of the container 2 by appropriate means such as Tig welding, for example, and the inside of the container 2 is sealed in a vacuum state.

  By the way, when the heat pipe 1 is installed in a thin electronic device such as a notebook computer, since the installation space in the thin electronic device is limited, as shown in FIG. 2 and FIG. Or the flat part 11 which performed the bending crushing process in the whole is formed. The surface of the container 2 on which the flat portion 11 is formed is substantially flat, but is bent and crushed because the container 2 is cylindrical or the inside of the container 2 is sealed under reduced pressure. The recess 12 is partially provided during processing. A method for maximizing the influence of the depression 12 on the performance of the heat pipe 1 will be described in detail later in another embodiment.

  As shown in the cross-sectional view of FIG. 3, the inner wall surface of the container 2 is provided with a large number of fins 4 protruding along the axial direction, and a working medium sealed and accommodated in the container 2 is provided between the fins 4. The groove 5 for allowing the pure water W (see FIG. 4) to flow by capillary action is formed. That is, in this embodiment, a groove type wick 6 is formed by the fins 4 and the grooves 5 formed on the inner surface of the container 2, and the grooves 5 are filled with pure water W. A hollow portion in the container 2 surrounded by the wick 6 is formed as a steam flow path 7. In the present embodiment, the groove wick structure in which the inner wall of the container 2 is made uneven is shown, but other wick structures in which the inner wall of the container 2 is provided with a mesh or fine line that promotes the flow of the working medium may be adopted. . Here, for convenience, a heating unit 13 that receives heat from a heat source such as a CPU is formed at one end of the heat pipe 1, and a cooling unit 14 that is cooled by a fan (not shown) is formed at the other end of the heat pipe 1. The In which position of the heat pipe 1 the heating unit 13 and the cooling unit 14 are formed is not particularly limited.

  As shown in FIG. 4, an oxide film 8 having a thickness of more than 30 nm and not more than 100 nm is formed on the inner surface of the wick 6 with which the pure water W inside the container 2 is in contact. The oxide film 8 is generated by putting the container 2 into an oxide film generating furnace (not shown) in a step before the pure water W is vacuum sealed in the container 2. The oxide film generation furnace raises the temperature of the container 2 between 150 ° C. and 200 ° C., heats the container 2 as a whole, takes in dry air blown from a dehumidifier (not shown), and 6 is supplied to the inside of the container 2 provided. And the oxide film 8 which has the said desired film thickness can be uniformly produced | generated on the inner surface of the container 2 by heating the container 2 for 10 minutes-30 minutes which is a fixed time inside an oxide film production furnace.

  Next, the operation when the heat pipe 1 having the above-described configuration is used for cooling the CPU in a notebook computer will be described below.

  When using a notebook computer, if the heat of the CPU is transferred to the heating unit 13 which is one end of the heat pipe 1, the temperature of the inner wall of the container 2 around the heating unit 13 rises, and the pure water W there evaporates. As the latent heat of vaporization is taken away, the CPU is cooled. On the other hand, in the wick 6 located in the heating unit 13, the vapor evaporated from the pure water W moves to a place where the temperature is low due to the pressure difference inside the container 2 and condenses. At that time, while releasing the latent heat of condensation, the heat is carried from the heating unit 13 on one end side of the heat pipe to the cooling unit 14 on the other end side cooled by a fan or the like. While the pure water W decreases in the heating unit 13 as it evaporates, the pure water W increases in the cooling unit 14 due to the condensation of steam, so that capillary force is generated in the groove-type wick 6 and the pure water W becomes the groove 5. The oxide film 8 having a thickness of more than 30 nm is formed on the wick 6 as in the heat pipe 1 of the present embodiment, and the wick 6 and the pure water W Even when the CPU has a significantly improved hydrophilicity and the CPU generates more heat, the pure water W is smoothly conveyed from the cooling unit 14 to the heating unit 13. Therefore, it is possible to avoid the possibility that the pure water W around the heating unit 13 is dried out and the heat transport is lowered, and the CPU as the heat source can be effectively cooled.

  Incidentally, even if the oxide film 8 exceeding 100 nm is formed on the groove type wick 6, the hydrophilicity between the wick 6 and the pure water W is not further improved, and a stable oxide film 8 is formed at the time of manufacture. On the contrary, it becomes difficult. Therefore, in consideration of manufacturability, the thickness of the oxide film 8 is preferably 100 nm or less.

  The hydrophilicity of the groove type wick 6 and the pure water W is greatly influenced by the surface state. For example, if the surface state of the wick 6 in contact with the pure water W is good, a certain degree of hydrophilicity can be ensured without forming the oxide film 8, but if the surface state of the wick 6 is not appropriate, the present embodiment Thus, the hydrophilicity can be remarkably improved by forming the oxide film 8 having a desired film thickness on the surface of the wick 6. In addition, since it is difficult to always keep the surface state of the wick 6 on the inner wall portion of the container 2 in a good state, the formation of the oxide film 8 is effective to always keep the hydrophilicity with the pure water W good. It can be said that it is a means.

  Here, various experimental results regarding the heat pipe 1 on which the oxide film 8 is formed in the present embodiment will be described below. FIG. 5 shows the thermal resistance-heater power characteristic A1 of the heat pipe in which no oxide film is formed in the conventional example and the thermal resistance-heater power characteristic A2 of the heat pipe 1 in which the oxide film 8 is formed. The characteristics A1 and A2 are values obtained by measuring three heat pipes 1 each. All of the heaters here are thermally connected to the heating unit 13 at one end of the heat pipe, and the cooling unit 14 is cooled by air blown from the same fan. As can be seen from FIG. 5, the heat resistance (temperature difference per unit power) of the heat pipe 1 on which the oxide film 8 is formed is remarkably low. In the thermal resistance-heater power characteristic A2 of the heat pipe 1 in this embodiment, there is a range of thermal resistance with the same heater power, but this depends on the amount of pure water W sealed in the container 2.

  Next, Table 1 shows a comparison between the appearance on the inner wall surface of the container 2 and the wettability before the oxide film 8 is generated and after the oxide film 8 is generated. The wettability was measured by measuring the spread distance (wet distance) when 0.01 cc of water was dropped, and for each measurement, four measurements and the average were calculated.

  From Table 1 above, it can be seen that the formation of the oxide film 8 significantly improves the wettability of water and the working medium.

  Further, FIG. 6 shows a change in wettability when the container 2 is heated inside the oxide film production furnace while taking in dry air. As is apparent from the experimental results, when the heating time exceeds 10 minutes, the wettability is improved as compared with the state before the oxide film 8 is generated, and then the wettability reaches the maximum value. However, even if the heating time is longer than that and the film thickness of the oxide film 8 is gradually increased, the wettability gradually decreases, and when the heating time exceeds 30 minutes, that is, the film thickness of the oxide film 8 is 100 nm. When it exceeds, wettability will return substantially to the state before heating. Therefore, the heating time is preferably within the range of 10 minutes to 30 minutes.

As described above, in the present embodiment, in the heat pipe 1 in which the pure water W is sealed in the container 2 made of metal having high thermal conductivity and having the wick 6 formed on the inner surface, the container 2 is, for example, an oxide film generation furnace. The inside of the wick 6 in contact with the pure water W in the container 2 is heated at a temperature between 150 ° C. and 200 ° C. by supplying air, which is a dry gas, to the inside of the container 2 for 10 minutes to 30 minutes. on the surface, and to have a thickness of less than 100nm exceeded 30 nm, to produce an oxide film 8 to keep always satisfactorily hydrophilic wick 6 and the pure water W, the inner surface of the wick 6 in contact with the pure water W, A manufacturing method for reducing the thermal resistance between the evaporation part and the condensation part of the pure water W is adopted.

  In this case, the pure water W decreases as the heating section 13 of the heat pipe 1 evaporates, while the pure water W increases in the cooling section 14 of the heat pipe 1 due to the condensation of the steam. Capillary force is generated, and the pure water W is transported along the groove 5 from the cooling unit 14 to the heating unit 13. For example, a wick that contacts the pure water W in a metal container 2 such as copper or a copper alloy is used. Since the oxide film 8 having a thickness exceeding 30 nm is formed on the inner surface of 6, the wettability between the wick 6 and the pure water W is remarkably improved, and good wettability can always be maintained. Therefore, even if more heat is transmitted from the CPU, which is a heat source, to the heating unit 13, the pure water W is smoothly conveyed from the cooling unit 14 to the heating unit 13, and the heat transport function resulting from the dry-out of the heating unit 13 Can be reduced, and the size of the container 2 can be reduced or the number of heat pipes 1 used can be reduced. Further, the spread of the pure water W in the heating unit 13 and the cooling unit 14 is improved, and the heat between the inner surface of the wick 6 in contact with the pure water W in the container 2 and the evaporation unit and the condensation unit of the pure water W is improved. The resistance can be reduced, and the heat pipe 1 having excellent heat transfer performance can be provided.

Even if the oxide film 8 having a thickness exceeding 100 nm is formed, the hydrophilicity between the wick 6 and the pure water W is not further improved, and it becomes difficult to form a stable oxide film 8 on the contrary. . Therefore, in order to always maintain good hydrophilicity between the wick 6 and the pure water W and form a stable oxide film 8, the film thickness is preferably 100 nm or less.

  In addition, regarding the manufacturing method of the heat pipe 1, the container 2 is heated at a temperature between 150 ° C. and 200 ° C., and the heated air is supplied to the inside of the container 2 for 10 minutes to 30 minutes. A uniform oxide film 8 can be generated.

  As a modification of the present embodiment, in the case where another wick structure in which a mesh or a fine wire for promoting the flow of the working medium is provided on the inner wall of the container 2 is employed, the oxide film 8 includes pure water W including the mesh and the fine wire. It is preferable to form the contact surface.

  Next, a second embodiment of the present invention will be described with reference to FIGS. The heat pipe 1 used here is exactly the same as in the first embodiment. Therefore, the same parts as those in the first embodiment are denoted by the same reference numerals, and description of common parts is omitted as much as possible.

  The container 2 that is the main body of the heat pipe 1 is formed with a flat portion 11 that has been subjected to bending crushing as described above. The flat portion 11 is formed in a part or the whole of the container 2 corresponding to the accommodation space in the thin electronic device to which the heat pipe 1 is attached. In addition, as shown in FIG. 10, the contact area between the flat heat receiving plate 32 that receives heat from the CPU 31 and the rectangular fins 33 that are heat radiators and the container 2 is secured to maximize the heat connection between them. The flat portion 11 described above is also provided in order to be strong. Such a flat part 11 is provided according to the surrounding situation of the heat pipe 1, and in the present embodiment, located in the heating part 13 that thermally connects the heat receiving plate 32 and the cooling part 14 that connects the fins 33, Each is partially provided in the container 2.

  FIG. 7 shows a cross-sectional view of the container 2 in the flat part 11 subjected to the bending crushing process, but here, the performance as the heat pipe 1 is reduced by the depression 12 provided when the flat part 11 is formed. In order to prevent this from occurring as much as possible, a protrusion 17 for expanding the steam passage 7 in the container 2 is formed on a part or the whole of the flat portion 11. The projecting portion 17 has a substantially semicircular cross-sectional shape, and is provided at a substantially central portion on the upper surface side, which is one side of the flat portion 11 where at least the recess 12 is formed. A projecting top portion 17A is formed along the longitudinal direction of the container 2 forming the above. In this way, although there is a recess 12 recessed inward of the container 2 on the lower surface side of the flat portion 11, the upper surface side of the flat portion 11 on the opposite side swells greatly outward of the container 2 instead of the recess 12. A protruding portion 17 is formed, and the protruding portion 17 secures a flow path 7 that promotes the flow of a large amount of steam not only on both sides of the container 2 but also in a substantially central portion.

  In the example shown in FIG. 7, the protruding portion 17 is provided only at the substantially central portion on the upper surface side of the flat portion 11, and the substantially flat flat portion 11 remains in the periphery in the width direction. As described above, the protruding portion 17 may be provided on the entire upper surface side of the flat portion 11 so as not to leave the flat portion 11. Also in this case, although there is a recess 12 on the lower surface side of the flat portion 11, a projecting portion 17 that is greatly bulged is formed above it, and the cross-sectional shape of the container 2 becomes a substantially semicircular shape. A substantially semicircular flow path 7 that facilitates the flow of a large amount of steam is secured.

  FIG. 9 is a plan view of the heat pipe 1 in a state in which the protrusion 17 in FIG. 7 is provided. In the figure, the protrusion 17 is provided on the upper surface side of the flat part 11 formed in the heating part 13 and the cooling part 14 of the heat pipe 1 respectively, but the protrusion 17 is provided on the lower surface side of the flat part 11. Alternatively, the protrusions 17 may be provided intermittently rather than continuously along the longitudinal direction of the container 2.

  FIG. 10 shows a state in which heat from the CPU 31 mounted on the notebook computer is carried to the fins 33 using the heat pipe 1 shown in FIG. In this figure, here, a heat receiving plate 32 as a heat receiving portion for receiving heat from the CPU 31 is closely connected to the lower surface side of the substantially flat flat portion 11 formed in the heating portion 13 and a blower (not shown). The fin 33 as a heat radiating part through which the wind from the air passes through is closely connected to the upper surface side of the flat part 11 formed in the cooling part 14. Note that the heat receiving plate 32 and the fins 33 may be configured as a part of the blower.

  Next, the operation of the above configuration will be described. When the heat of the CPU 31 is transferred from the heat receiving plate 32 to the heating unit 13 that is one end of the heat pipe 1 when using the notebook computer, the container 2 around the heating unit 13 is heated. The temperature of the inner wall rises, the pure water W there evaporates and the latent heat of vaporization is taken away, whereby the CPU 31 is cooled. On the other hand, in the wick 6 located in the heating unit 13, the vapor evaporated from the pure water W moves to a place where the temperature is low due to the pressure difference inside the container 2 and condenses. At that time, while releasing condensation latent heat, heat is carried from the heating unit 13 on one end side of the heat pipe to the cooling unit 14 on the other end side cooled by the fins 33 or the like. While the pure water W decreases in the heating unit 13 as it evaporates, the pure water W increases in the cooling unit 14 due to the condensation of steam, so that capillary force is generated in the groove-type wick 6 and the pure water W becomes the groove 5. Are carried from the cooling unit 14 to the heating unit 13.

  In this series of cooling cycles, in order to maximize the contact area between the heat receiving plate 32 and the container 2, and between the container 2 and the fin 33, and to strengthen the mutual heat connection, the heating unit 13 and the cooling of the container 2 are cooled. In the portion 14, a flat portion 11 is formed by crushing. However, in recent years, as the amount of heat generated by the CPU 31 has increased, the amount of steam generated inside the container 2 has greatly increased, and the steam flow path 7 in the container 2 is limited to the speed of sound (the speed of steam can exceed the speed of sound). No) and the scattering limit (water is not returned by flying the water facing the steam), and it is difficult to further increase the amount of heat transport. Conventionally, the shape of the entire container 2 has been increased, or the number of heat pipes 1 has been increased.

  However, when the flat portion 11 is formed by the crushing process as described above, a recess 12 of the flat portion 11 is generated during processing. Therefore, the flow path 7 of the steam is narrowed by the recess 12, and the above-described sound velocity limit and The scattering limit is likely to occur, and the performance as the heat pipe 1 is adversely affected. Therefore, in this embodiment, in order to prevent the sound velocity limit and the scattering limit due to the steam flow path 7, the flat part 11 is provided with a projecting part 17 having a substantially semicircular cross section, and the steam flow path 7 in the container 2. By ensuring sufficient, the heat pipe 1 that is optimal for thin electronic devices such as notebook computers with a small storage space can be supplied without increasing the overall shape of the container 2 or increasing the number of heat pipes 1 This makes it possible to effectively cool the CPU 31 that is a heat source. In addition, since the contact area between the heat receiving plate 32 and the container 2 and between the container 2 and the fin 33 can be largely secured by the flat portion 11, the heat pipe 1 having a small heat resistance and excellent heat transfer performance can be provided.

  As described above, in the present embodiment, in the heat pipe 1 in which the pure water W as the working medium is enclosed in the container 2, the substantially flat flat portion 11 is formed on a part or the whole of the container 2, A projecting portion 17 having a substantially semicircular cross-sectional shape is formed on a part or the whole of the flat portion 11.

  In this way, even if the flat portion 11 is formed due to the surrounding situation of the heat pipe 1, the steam flow path 7 inside the container 2 is sufficiently secured by the protruding portion 17. The scattering limit is less likely to occur, and the container shape can be downsized or the number of heat pipes 1 used can be reduced. In addition, by providing the flat portion 11 in the pipe-shaped container 2, it becomes possible to perform sufficient flattening on the heat receiving member such as the heat receiving plate 32 and the heat connecting portion with the heat radiating member such as the fin 33, Since heat resistance can be reduced by ensuring a large contact area with each of these members, the heat pipe 1 having excellent heat transfer performance can be provided.

  Further, as shown in FIGS. 9 and 10, if the projecting portion 17 is formed along the longitudinal direction of the container 2, the projecting portion 17 is formed along the direction in which the steam in the container 2 flows. The sound speed limit and the scattering limit in the container 2 are further less likely to occur.

  Moreover, as shown in FIG. 8, you may form the cross-sectional shape of a part of or the whole container 2 in a substantially semicircular shape. Also in this case, by forming a part or the whole of the cross-sectional shape of the container 2 in a substantially semicircular shape, the steam flow path 7 in the container 2 is sufficiently secured. The limit is less likely to occur, and the container shape can be downsized or the number of heat pipes 1 used can be reduced. Further, if the projecting portion 17 having a substantially semicircular cross-sectional shape is provided on one side of the flat portion 11, a heat connection portion with a heat receiving member such as the heat receiving plate 32 or a heat radiating member such as the fin 33 In addition, it is possible to perform sufficient flattening, and it is possible to provide a heat pipe 1 with excellent heat transfer performance because a large contact area with each of these members can be secured to reduce thermal resistance.

  Next, another modification of the present embodiment is shown in FIGS. Here, the protruding portion 17 is formed not in the longitudinal direction of the container 2 but in the width (left and right) direction of the container 2 and thus the flat portion 11. Providing such a protrusion 17 makes it difficult for the sound speed limit and the scattering limit in the container 2 to occur, and the container shape can be downsized or the number of heat pipes 1 used can be reduced. Further, particularly in this case, since the projecting portions 17 can be concentrated and provided at the locations where the recesses 12 are likely to occur when the flat portion 11 is formed on the container 2, the sound velocity limit and scattering locally generated by the recesses 12 can be provided. Limits can be effectively prevented.

  In addition, this invention is not limited to the said Example, It can change in the range which does not deviate from the meaning of this invention.

It is a front view before the bending process of the heat pipe in 1st Example of this invention. It is a perspective view of a heat pipe after performing bending crushing processing same as the above. FIG. 3 is a cross-sectional view of the flat portion in FIG. It is an expanded sectional view of the principal part shown in FIG. 3 same as the above. It is a graph which shows the thermal resistance-heater electric power characteristic of the heat pipe in a present Example and a prior art example. It is a graph which shows the relationship between heating time and wettability. It is sectional drawing of the flat part which showed the state which provided the protrusion part in the container in 2nd Example of this invention. It is sectional drawing of the flat part which shows the modification of FIG. 7 same as the above. It is a top view of the heat pipe of the state which provided the protrusion part shown in FIG. 7 same as the above. It is a front view of the state which thermally connected various members to the heat pipe shown in FIG. 9 same as the above. It is a top view of the heat pipe of the state which provided the protrusion part which shows another modification same as the above. It is a front view of the heat pipe shown in FIG. 11 same as the above.

1 Heat pipe 2 Container 6 Wick 8 Oxide film W Pure water (working medium)

Claims (1)

In a method of manufacturing a heat pipe made of copper or copper alloy having high thermal conductivity and having a working medium enclosed in a container having a wick formed on the inner surface, the container is heated at a temperature between 150 ° C. and 200 ° C. , by supplying dry air into the container 10 to 30 minutes, the wick inside surface in contact with the working medium, to have a thickness of less than 100nm exceeded 30 nm, net said a wick and the working medium An oxide film that maintains good hydrophilicity with water at all times is uniformly generated, and the thermal resistance between the inner surface of the wick in contact with the working medium and the evaporation section and the condensation section of the working medium is reduced. A method for manufacturing a heat pipe.

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