JP4382892B2 - Flat heat pipe and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat heat pipe in which a wick is disposed in a cavity.
[0002]
[Prior art]
In recent years, cooling technology for heat-generating components such as semiconductor elements mounted on electric devices such as personal computers has attracted attention. One method is a cooling technique using a heat pipe. A typical cooling method using a heat pipe is a mode in which a heat pipe is attached to a heat generating component, and heat of the heat generating component is carried to a heat radiating fin or the like through the heat pipe as a path to dissipate. There is also an electric device in which a small fan that forcibly blows air to the fins is installed.
[0003]
Briefly describing the heat pipe, the heat pipe has a hollow portion sealed inside, and a certain amount of working fluid (also referred to as hydraulic fluid) such as water or alternative chlorofluorocarbon is contained in the hollow portion. is there. The inside of the cavity is evacuated so that the working fluid is easily evaporated. The working fluid exists in a mixed state of a liquid phase and a gas phase (vapor) in the cavity.
[0004]
In the heat pipe, the working fluid in the cavity evaporates, and the heat transfer function is activated by the movement of the vapor. For example, in the case of a straight type heat pipe, when heat is applied from one end side thereof (this part is referred to as a heat absorption part of the heat pipe), the working fluid that is in a liquid phase in the heat absorption part evaporates, and the vapor Moves to the other end, where the vapor condenses and dissipates heat (this portion is called the heat dissipating part of the heat pipe). If fins or the like are attached to the heat radiating portion of the heat pipe, the heat of the working fluid vapor is easily dissipated to the outside.
[0005]
By the way, if the working fluid condensed in the heat radiating part does not return to the heat absorbing part, the above-described operation is not continued. Therefore, it is necessary to return (reflux) the working fluid (liquid phase) condensed in the heat radiating section to the heat absorbing section. Usually, the liquid phase of the working fluid condensed in the heat dissipation part is lowered by gravity by positioning the heat absorption part below the heat dissipation part. Such a state may be referred to as a bottom heat mode.
[0006]
When the heat dissipating part cannot be arranged above the heat absorbing part, the working fluid cannot be recirculated by the gravitational action. Therefore, there are known methods of disposing a wick (mesh, wire, etc.) that develops a capillary action in the cavity of the heat pipe or forming a fine groove on the inner wall of the cavity. In addition, the case where the heat radiating part is located below the heat absorbing part may be referred to as a top heat mode. Even when the heat dissipating part is positioned substantially horizontally with the heat absorbing part, it is difficult to expect the working fluid to recirculate due to the gravity action. In such a case, a wick is often disposed.
[0007]
[Problems to be solved by the invention]
In recent years, electrical devices such as personal computers have been remarkably downsized and improved in performance, and downsizing and space saving of a cooling mechanism for cooling heat-generating components such as CPU and MPU mounted thereon are strongly desired. Therefore, in the case of a cooling mechanism using a heat pipe, it is required to reduce the diameter of the heat pipe.
[0008]
Therefore, for example, a thin heat pipe having an outer diameter of about 3 mm has been put into practical use and has already been applied to a cooling mechanism such as a personal computer. However, depending on the space in the housing of a personal computer or the like, a heat pipe (flat heat pipe) in which the thin diameter heat pipe is further crushed to have a substantially flat cross section may be used.
[0009]
By the way, one of the advantages of using a heat pipe is that the distance between the location of the heat generating component and the heat radiation location (location where fins are arranged) can be increased to some extent. In other words, for example, the heat generating parts such as CPU and MPU are often arranged not in the vicinity of the outer wall inside the personal computer body but in a position away from them, but in such a case, heat is generated by passing through the heat pipe. The heat of the parts can be efficiently transferred to the vicinity of the outer wall of the PC main body where the fins and fans are arranged.
[0010]
On the other hand, in the case of a portable personal computer or the like, since it is desired to reduce its size and weight, the shape of the main body portion on which heat generating components such as a CPU and MPU are mounted tends to be thinned. For this reason, the heat pipe used for the cooling mechanism of the heat-generating component often has its heat absorbing portion and heat radiating portion positioned substantially horizontally. Further, depending on the usage form of a personal computer or the like, the heat pipe may be in a top heat mode. For these reasons, a wick is often inserted into a heat pipe used in a device such as a personal computer or a fine groove is formed on the inner wall of the cavity.
[0011]
However, if the heat pipe is long to some extent, the return path of the working fluid becomes long. Therefore, in the case where the groove is formed on the inner wall of the cavity, the capillary action may be insufficient. On the other hand, even in the case of a heat pipe with a wick in the cavity, especially in the case of a flat heat pipe with a small diameter, the cross-sectional area of the cavity is small, so the steam of the working fluid becomes faster and moves in the opposite direction to the steam The movement of the liquid phase of the working fluid to be performed is likely to be hindered. In particular, in the case of a thin flat heat pipe having a thickness of about 1.5 mm or less, this tendency tends to be remarkable.
[0012]
If the working fluid is not sufficiently recirculated, a so-called dry-out phenomenon may occur, and heat transfer by the heat pipe stops or performance degradation occurs. Under such circumstances, even in the case of a thin flat heat pipe, it has been desired to develop a flat heat pipe that sufficiently maintains the reflux of the working fluid and exhibits excellent characteristics.
[0013]
[Means for Solving the Problems]
The present invention has been made in view of the above-described problems, and is intended to provide an excellent flat heat pipe that sufficiently maintains the reflux of the working fluid.
That is, the flat heat pipe of the present invention is thin, the container having a flat cross-sectional shape of the cavity portion, and inserted into the container, has a length equivalent to the longitudinal direction of the cavity portion, and its longitudinal direction. It has the structure of having a plate material in which one dent portion is formed and a wick inserted and arranged in the dent portion.
[0014]
The recessed portion may be formed in the plate material so as to be positioned at a substantially central portion in the hollow portion. The plate material may be provided with a plurality of holes or notches. The plate material of the present invention is preferably made of copper.
[0015]
As a manufacturing method of the flat heat pipe ( thin type) of the present invention described above, a wick is inserted into the concave portion of the plate material in which the concave portion along the longitudinal direction is formed, and the plate material is placed in a container base tube having a substantially circular shape. The manufacturing method which has the process of inserting, the process of converting the said container base pipe into a heat pipe, and the process of flattening the said container base pipe converted into a heat pipe is proposed.
[0016]
Further, a step of inserting a wick into the concave portion of the plate material formed with a concave portion along the longitudinal direction, and inserting the plate material into a container base tube having a substantially circular shape, a step of flattening the container base tube, The manufacturing method of the flat heat pipe which has the process of making the said container into a heat pipe is proposed.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an explanatory view schematically showing a part of the manufacturing process of the flat heat pipe of the present invention.
First, a container pipe 30 (copper pipe) to be a heat pipe container is prepared. A wick is inserted into the pipe 30. At this time, a plate member 20 having a recess formed along the longitudinal direction is prepared, the wick 10 is arranged in the recess, and the container base tube 30 together with the plate member 20 is arranged. (Fig. 1 (a)).
[0018]
Some examples of the plate material in which the recesses along the longitudinal direction are formed are given in FIG. FIG. 2A shows a plate material 20 bent into a substantially U shape. The plate material 21 of FIG. 2A has a shape in which the opening side of the substantially U shape is narrowed, and the plate material 22 of FIG. It has a shape with rounded corners. Of course, the plate material may have other forms. In any of the examples shown in FIG. 2, holes or notches are provided in the plate material.
[0019]
In the example shown in FIG. 1, the one having the shape shown in FIG. Now, the wick 10 is inserted into the recess of the plate member 20, and the plate member 20 is inserted into the container base tube 30. The wick 10 may be, for example, a braided metal thin wire (sometimes called a braid) or a bundle of thin metal wires. FIG. 4 schematically shows a wick in the form of knitted metal wires (FIG. 4A) and a wick in the form of bundled metal wires (FIG. 4A).
[0020]
After inserting the plate material 20 together with the wick 10 into the container base 30, the container base 30 is subjected to processes (heat pipe formation) such as cleaning, injection of working fluid, degassing, and welding sealing at both ends. obtain.
[0021]
Next, as shown in FIG. 1A, the container pipe 30 formed into a heat pipe is subjected to flat processing such as press processing to obtain a flat heat pipe 3 as shown in FIG.
[0022]
The plate member 20 plays a role in which the wick 10 is held at a fixed position (in this case, substantially the central portion) of the container base tube 30 during the flattening. That is, when the flat heat pipe 3 is obtained by performing the flat processing, the wick 10 is substantially held in the central portion over the entire length of the hollow portion of the flat heat pipe 3 in the longitudinal direction. As described above, the wick 10 can be easily arranged by being applied to the plate member 20 over the entire length in the longitudinal direction of the hollow portion of the flat heat pipe 3 in the central portion.
[0023]
In the above example, the container base tube 30 is flattened after undergoing a heatpipe process such as injection of working fluid, deaeration, and welding sealing at both ends. It may be performed prior to the process.
[0024]
When the operation test of the flat heat pipe 3 of the present invention is performed, even when the heat absorbing portion is not located below the heat radiating portion (horizontal arrangement or top heat mode), the working fluid is maintained at a high reflux and has excellent heat. It was found that the transport characteristics were realized.
[0025]
In the above-described flat heat pipe of the present invention, even when the top heat mode or the heat absorbing portion and the heat radiating portion are substantially horizontally arranged, the present inventors infer the reason why the excellent heat transfer characteristics are maintained as follows. To do.
This will be described with reference to FIG. The wick 10 disposed in the hollow portion 31 of the flat heat pipe 3 is disposed at a substantially central portion over the substantially entire length of the flat heat pipe 3 by the plate material 20 (holes and cuts are not shown). It is like that. Although not shown, the working fluid is also accommodated in the cavity 31.
[0026]
As shown in FIG. 3, the wick 10 is arranged in the substantially central portion of the hollow portion 31 over the substantially entire length of the flat heat pipe. A portion where the vapor of the fluid moves (a space in the cavity other than the wick 10) is divided into substantially constant positions. Therefore, the movement of the liquid phase of the working fluid that goes against the flow of the working fluid vapor is less likely to be hindered by the steam. In the present invention, the inventors speculate that such a situation is a mechanism in which excellent heat transfer characteristics are maintained even when the top heat mode or the heat absorbing portion and the heat radiating portion are substantially horizontally arranged.
[0027]
The wick 10 does not necessarily have to be arranged at the center of the cavity 31. For example, it may be arranged close to the end of the cavity 31. In any case, it is important that the steam flow path 31 and the wick 10 are divided so as to reduce mutual interference over almost the entire length of the flat heat pipe 3.
[0028]
On the other hand, in the case of the conventional flat heat pipe, the wick disposed in the cavity is easily disturbed practically. This point will be described with reference to FIGS.
The example of FIG. 5 shows a case where the wire wick 50 is arranged along the inner wall in the pipe 40 by the elastic force of the spiral tape 51 wound in a spiral shape, and the pipe 40 is crushed and flattened. However, in the case of this example, in the crushing step, the wire 50 is likely to be disturbed and messy. In the example of FIG. 6, the mesh 52 is arranged along the inner wall of the pipe 40, and is crushed and flattened. In this case as well, the mesh 52 is easily disturbed during flattening.
[0029]
If the wire wick 50 and the mesh 52 are disturbed as in the conventional example shown in FIGS. 5 and 6, the wick portion and the steam flow path portion are disturbed. In particular, in the case of a flat heat pipe with a small diameter, the movement of the working fluid vapor is likely to be accelerated, and it is likely that a phenomenon such as the working fluid liquid phase on the wick surface being scattered by the working fluid vapor is likely to occur. This seems to be the cause of the insufficient reflux of the working fluid.
[0030]
By the way, the meaning which provided many holes and notches (slits) in the board | plate materials 20-22 shown in FIG. 2 is demonstrated easily. Such holes and notches are not essential, but when assembled in a flat heat pipe, the plate 20 to 22 has a bend of the flat heat pipe to some extent in addition to ensuring the vapor permeability of the working fluid. When used, there is also a meaning that the plate members 20 to 22 are more easily bent. If the plate material is easy to bend, it is desirable that the occurrence of the deviation of the recess portion of the plate material in the hollow portion of the flat heat pipe can be suppressed to some extent.
[0031]
【Example】
Although the embodiment of the present invention is not limited to the above-described example, the example will be described with respect to the example shown in FIGS.
The container base tube 30 was made of copper and had an outer diameter of 6 mm and a wall thickness of 0.25 mm. As the board | plate material 20, what formed many holes and notches (slits) in the copper-made board of thickness 0.25mm was used. A wick 10 in which a large number of metal wires having a wire diameter of 0.1 mm were bundled (not shown at both ends, but processing for preventing the metal wires from being scattered) was inserted into the recesses of the plate material 20.
[0032]
After inserting the plate material 20 into the container base tube 30, the container base tube 30 was formed into a heat pipe (the working fluid was water), and further pressed in the direction of the arrow shown in the figure to be crushed to a thickness of 1 mm. The flat heat pipe 3 (with a length of about 200 mm) obtained in this way was placed horizontally, the 50 mm portion was heated from one end, and the other side was cooled and dissipated. The temperature difference could be kept very small. It was found that several times the heat transport characteristics were realized compared to the result of a similar test conducted with a conventional heat pipe.
[0033]
【The invention's effect】
As described above, the flat heat pipe and the manufacturing method thereof according to the present invention sufficiently maintain the reflux of the working fluid and realize excellent heat transfer characteristics.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing a part of a manufacturing process of a flat heat pipe of the present invention.
FIG. 2 is an explanatory view showing an example of a plate material of the present invention.
FIG. 3 is a partial cross-sectional view of an example of a flat heat pipe of the present invention.
FIG. 4 is an explanatory diagram showing an example of a wick used in the present invention.
FIG. 5 is an explanatory view schematically showing a part of a manufacturing process of a conventional flat heat pipe.
FIG. 6 is an explanatory view schematically showing a part of a manufacturing process of a conventional flat heat pipe.
[Explanation of symbols]
10 Wick 20 Plate Material 21 Plate Material 22 Plate Material 3 Flat Heat Pipe 30 Container Base 31 Cavity 50 Wire Wick 51 Spiral Tape 52 Mesh

Claims (6)

A container having a flat cross-sectional shape of the cavity, and a plate member inserted into the container, having a length equivalent to the longitudinal direction of the cavity, and having one recess in the longitudinal direction; A thin flat heat pipe having a wick inserted and disposed in the recess. The thin flat heat pipe according to claim 1, wherein the recess is formed in the plate material so as to be positioned at a substantially central portion in the cavity. The thin flat heat pipe according to claim 1 or 2 , wherein the plate member is provided with a plurality of holes or notches. The thin flat heat pipe according to claim 1, wherein the plate material is made of copper. It is a method of manufacturing the thin flat heat pipe in any one of Claims 1-4, Comprising: A wick is inserted in the said dent part of the board | plate material in which the dent part along the longitudinal direction was formed, and the board | plate material is substantially circular shape. A method for producing a thin flat heat pipe, including a step of inserting the container base tube into a heat pipe, a step of converting the container base tube into a heat pipe, and a step of flattening the container base tube into a heat pipe. It is a method of manufacturing the thin flat heat pipe in any one of Claims 1-4, Comprising: A wick is inserted in the said dent part of the board | plate material which formed the dent part along a longitudinal direction, The board | plate material is substantially circular. A method for producing a thin flat heat pipe , comprising a step of inserting into a container base pipe having a shape, a step of flattening the container base pipe, and a step of forming the container into a heat pipe .

Images