JP3108656B2 - Plate type heat pipe and cooling structure using it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate-type heat pipe and a cooling structure for a cooled element such as a semiconductor element using the same.

[0002]

2. Description of the Related Art Electronic components such as semiconductor elements mounted on various devices such as personal computers and electric and electronic devices such as power equipment are inevitable to generate a certain amount of heat by use thereof. It is becoming a technical issue. As a method of cooling an electric / electronic element requiring cooling (hereinafter referred to as a cooled element), for example, a fan is attached to a device,
Representatively known are a method of lowering the temperature of the air in the equipment housing, a method of particularly cooling the element to be cooled by attaching a cooling body to the element to be cooled, and the like.

As a cooling body attached to the element to be cooled, for example, a plate made of a material having excellent heat conductivity, such as a copper material or an aluminum material, or a plate-type heat pipe is often used. The plate-type heat pipe is a plate-shaped heat pipe, and may also be called a flat heat pipe or a flat plate heat pipe. Hereinafter, the term “plate-type heat pipe” will be used.

[0004] The heat pipe will be briefly described. The heat pipe includes a container having a hollow portion and a working fluid, and heat is transported by phase transformation and movement of the working fluid sealed in the heat pipe. Of course, some heat is transferred by conducting heat through the container (container) constituting the heat pipe, but the amount is relatively small. A heat pipe is a heat transfer device mainly intended for a heat transfer operation by a working fluid.

The operation of the heat pipe is briefly described as follows. That is, on the heat absorbing side of the heat pipe, the working fluid evaporates due to heat transmitted through the material of the container (container) constituting the heat pipe, and the vapor moves to the heat radiation side of the heat pipe. On the heat radiation side, the vapor of the working fluid is cooled and returns to the liquid state again. Then, the working fluid that has returned to the liquid phase moves (recirculates) to the heat absorbing side again. Heat is transferred by such phase transformation and movement of the working fluid. The inside of the heat pipe is sealed so as to minimize mixing of gases and the like other than the working fluid in order to easily cause a phase transformation of the working fluid.

[0006]

The working fluid that has turned into a vapor on the heat absorbing side is cooled on the heat radiating side and returns to the liquid state again. In order to continue such heat transfer, the working fluid that has returned to the liquid phase must be returned to the heat absorbing side again. Usually, by disposing the heat absorbing side below the heat releasing side, the working fluid that has returned to the liquid phase can be returned by gravity. However, in the case of an electric / electronic device such as a personal computer, the device may be greatly inclined or inverted depending on the use condition. In this case, it is not possible to expect the working fluid to return by gravity.

Therefore, as a plate-type heat pipe, for example, in Japanese Patent Application Laid-Open No. 7-208884, a block-shaped wick having strong capillary force is disposed inside the plate-type heat pipe so as to contact the upper and lower surfaces of the plate-type heat pipe. Things have been suggested. In the case of such a plate-type heat pipe, FIG.
As shown in (a), if the plate-type heat pipe 40 is substantially horizontal and a heating element 41 to be cooled is attached to the lower surface thereof, sufficient cooling performance can be obtained. Similar to a heat pipe, except that a heating element 41 to be cooled is attached to the upper surface side (FIG. 4).
(A)) However, due to the capillary action of the wick, the working fluid can be expected to return to some extent.

As shown in FIG. 4A, the operation state of the heat pipe when the heating element 41 is not located at the lower part is sometimes called a top heat mode. FIG. 4A shows a typical case. By the way, in the cases of FIGS. 4A and 4B, the plate-type heat pipes 40 are arranged substantially horizontally, but in other cases, the plate-type heat pipes 40 are arranged inclined. possible.

FIG. 4C shows a typical example of such a case in which the plate-type heat pipes 40 are arranged substantially vertically. In this case, if the heating element 41 is installed at the position indicated by the reference numeral 410 shown by the dotted line in the drawing, the working fluid can be recirculated by gravity action instead of the top heating mode. Plate type heat pipe 4
0, a top heat mode can be set. In this case, depending on the calorific value of the heating element 41, the size of the plate-type heat pipe 40, the amount of the working fluid, etc. In some cases, the reflux cannot catch up and dry out. Such a problem,
This can occur even when the plate-type heat pipe 40 is not necessarily vertical but is slightly inclined.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. The plate-type heat pipe of the present invention is a plate-type heat pipe provided to face a substrate on which the element to be cooled is mounted, and the inside of the plate-type heat pipe is transferred to a position corresponding to the element to be cooled. The heat column portion is disposed, and the metal porous body or the metal mesh molded body is disposed so as to contact at least the heat transfer column portion having the largest heat absorption among the one or more heat transfer column portions. Regardless of the position of the plate-type heat pipe, it operates on at least one of the heat transfer column portion or the metal porous body having the largest heat absorption amount, or at least one of the heat transfer column portion or the metal mesh molded body having the largest heat absorption amount. The liquid phase of the fluid is in contact.

In some cases, the above-described porous metal body or metal mesh molded body is arranged so as to be in contact with one of the upper and lower inner walls of the plate-type heat pipe. In some cases, the metal porous body or the metal mesh molded body is disposed in an intermediate region between the upper and lower inner walls of the plate-type heat pipe so that the upper and lower inner walls are not substantially in contact with each other.

As the outer shape of the plate-type heat pipe, it is preferable to form a projection at a position where the heat transfer column is disposed.
Further, the metal porous body may be formed integrally with the container of the plate-type heat pipe.

Further, the present inventors use the above-mentioned plate-type heat pipe of the present invention to dispose the plate-type heat pipe relative to a printed circuit board on which semiconductor elements and the like are mounted as elements to be cooled. A semiconductor device cooling structure is proposed in which a semiconductor element is connected to the plate-shaped heat pipe, and a heat sink is joined to the plate-shaped heat pipe.

[0014]

FIG. 1 is an explanatory view showing a plate-type heat pipe 10 according to the present invention. FIG. 2 is an explanatory view showing a cooling structure of the semiconductor elements 20, 21, and 22 using the plate heat pipe 10. As shown in FIG. The plate type heat pipe of the present invention will be described with reference to these drawings. Although not essential for the present invention, the plate-type heat pipe 10 has an outer shape in which predetermined convex portions are provided in accordance with the distance between the semiconductor elements 20, 21, and 22 facing each other. In this way, even if the plurality of elements to be cooled (semiconductor elements) have different heights, a single plate-type heat pipe 10 can make good thermal connection with these elements.

The plate type heat pipe of the present invention is a plate type heat pipe provided to face a substrate on which one or a plurality of elements to be cooled (corresponding to the semiconductor elements 20 to 22 in FIG. 2) are mounted. And semiconductor elements 20 to 2 inside thereof.
The heat transfer column portions 130 to 132 are arranged at positions corresponding to No. 2. The metal porous body 15 is provided at least on the heat transfer column 131 corresponding to the semiconductor element having the largest amount of heat to be cooled (here, the semiconductor element 21 is temporarily assumed).
Are provided so as to be in contact with each other.

In FIGS. 1 and 2, a metal mesh formed body formed by forming a metal mesh may be used instead of the metal porous body 15. The metal mesh molded body refers to a metal mesh formed by bundling or rolling a mesh such as a woven or non-woven metal fabric, and further applying a press or the like as necessary. still,
1 and 2, a metal mesh 14 is provided in addition to the metal porous body 15 (or a metal mesh formed body instead). This is attached as a normal wick along the vicinity of the inner surface of the plate type heat pipe 10. In the present invention, the metal mesh 14 is not indispensable, but by providing this, realization of a plate heat pipe with higher performance can be expected.

Examples of the porous metal body include a sintered metal powder, a porous metal electrodeposited (electrochemically deposited), a precision cast, a cellular porous body, and the like. A material prepared by various methods, such as a method in which a metal is plated on a porous resin body and then the resin is removed, a method in which one phase of a two-phase alloy is removed by acid, electrolysis, or the like, can be appropriately applied. The porosity of this porous metal body is preferably about 20% or more, although it depends on the type of working fluid and other factors.

As the metal mesh formed body, a metal mesh sheet such as a metal woven fabric or a metal nonwoven fabric is used, and the sheet is rolled into a cylindrical shape, or if necessary, multiple rounded. It is preferable to form a sheet of metal mesh on top of another.

When a metal woven fabric is used as a metal mesh sheet used for obtaining a metal mesh molded body,
Although it depends on the type of the working fluid and the like, it is generally 0.03-0.
It is preferable to use a fiber having a fiber diameter of 3 mm and a roughness of about $ 30 to $ 200. When a plurality of metal mesh sheets are stacked and used, depending on the type of the working fluid and the size of the plate-shaped heat pipe, it is appropriate to stack approximately 3 to 30 sheets. When a metal non-woven fabric is used as the metal mesh, it depends on the type of the working fluid and the like, but has a fiber diameter of about 0.03 to 0.3 mm and a thickness of 0.1 to 5 mm assembled to have an appropriate porosity. It is good to use something of the order. When a plurality of these are used, depending on the type of the working fluid and the size of the plate-shaped heat pipe, it is appropriate to generally overlap about 3 to 30 sheets.

The external shape of the porous metal body or the metal mesh molded body can be appropriately applied to a cylindrical shape, a rod shape, or other shapes. FIG. 5 is a conceptual diagram schematically showing a metal porous body and a metal mesh formed body formed into a rod shape. FIG.
(A) is obtained by rolling a sheet of a metal mesh (woven cloth) and subjecting it to a further forming process to appropriately shape the sheet. FIG. 5 (a) shows a structure in which metal fibers are aggregated and hardened into an appropriate shape (metal nonwoven fabric). FIG. 5C shows a metal porous body formed into an appropriate shape.

Returning to FIGS. 1 and 2, the plate-type heat pipe 10 of the present invention is provided opposite to a substrate 24 on which semiconductor elements 20 to 22 are mounted.
Heat transfer columns 130 to 132 are provided at positions corresponding to 0 to 22. Here, of the semiconductor elements 20 to 22,
The element which generates the largest amount of heat and which should be cooled the most is assumed to be a semiconductor element 21.

In FIG. 2, the semiconductor element 20 to be cooled is
To 22 are located below the plate-shaped heat pipe 10,
Accordingly, the heat absorbing portion of the plate-type heat pipe 10 is located below the heat radiating portion (the side in contact with the fin 16 in FIG. 2). Therefore, this state is not the top heat mode,
The working fluid returns by gravity. However, when the plate-type heat pipe 10 is inclined, for example, to the left, the liquid phase portion of the working fluid contained therein is:
Most of the heat is concentrated near the right end of the plate-type heat pipe 10. In this case, the liquid phase portion of the working fluid due to gravity cannot move from the right end to the left end of the plate heat pipe.

However, even in such a case, the heat transfer column 13
Numerals 0 to 132 serve to transfer heat of the corresponding semiconductor elements 20 to 22 to the fins 16 by heat conduction. on the other hand,
At least, among the heat transfer columns 130 to 132, the heat transfer column 131 having the largest heat absorption is provided so as to be in contact with the metal porous body 15 (or, alternatively, a metal mesh formed body). Then, regardless of the attitude (inclination) of the plate heat pipe 10, the liquid phase portion of the working fluid is always in contact with the metal porous body 15 (or a metal mesh formed body) or the heat transfer column 131. It has become.

Depending on the attitude (inclination) of the plate-type heat pipe 10, the liquid phase of the working fluid comes into contact with both the metal porous body 15 (or, alternatively, a metal mesh formed body) and the heat transfer column 131. There may be a state where the liquid phase portion of the working fluid is in contact with only one of them. In any case, regardless of the attitude (inclination) of the plate-type heat pipe 10, the liquid phase portion of the working fluid is a metal porous body 15 (or a metal mesh formed body when a metal mesh formed body is used instead). Or at least one of the heat transfer columns 131.

Therefore, irrespective of the position of the plate-type heat pipe 10, the heat transfer column 13 showing at least the maximum heat absorption amount
In part 1, the working fluid returned to the liquid phase can be recirculated by the capillary action of the metal porous body 15 (or a metal mesh formed body instead). Therefore, sufficient cooling performance can be maintained.

In the example shown in FIGS. 1 and 2, the metal porous body 15 (or, alternatively, a metal mesh molded body) is used.
Is installed so as to contact not only the heat transfer column 131 showing the maximum heat absorption but also the other heat transfer columns 130 and 132.

By the way, the metal porous body 15 (or, alternatively, a metal mesh formed body) is made of a plate-shaped heat pipe 1.
Although it may be arranged so as to be in contact with the inner wall of 0,
It is desirable that the heat pipe 10 is disposed apart from the upper inner wall or the lower inner wall of the plate-shaped heat pipe 10 because a wide steam flow path for the working fluid can be secured. When installed at a position (intermediate portion) apart from any of the upper and lower inner walls, a vapor flow path can be secured above and below.

The metal porous body 15 may be formed by laminating metal meshes or by appropriately shaping a rounded one.

In the example shown in FIGS.
Are arranged so as not to contact the upper inner wall of the plate type heat pipe 10 and to contact the lower inner wall. In FIGS. 1 and 2, the metal porous body 15 is illustrated as being separated from the lower inner wall, but this is convenient for illustration.

The heat transfer pillars 130 to 132 may be used separately, but may be used as an integrated one.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows the appearance of the plate-type heat pipe 10 of the present embodiment. FIG. 3A illustrates the opposite side of FIG. The container of the plate-type heat pipe 10 is formed by joining the upper plate 11 and the lower plate 12 provided with the convex portions 120 and 121. The joining method is BAg-8
(Silver brazing). Convex part 120, 1
21 was formed by press working. Inside the container thus formed, a metal mesh 14 and the like described later are installed. Then, pure water equivalent to 30% of the internal volume of the plate-type heat pipe 10 was vacuum-sealed as a working fluid.

FIG. 1 is a partial sectional view of a plate-type heat pipe 10. The heat transfer columns 130 to 132 made of oxygen-free copper were placed at positions corresponding to the protrusions 120 and 121. The heat transfer columns 130 to 132 were joined to the inner wall (upper plate 11 and lower plate 12) of the plate-type heat pipe 10 by brazing as described above.

A single metal mesh 14 (made of oxygen-free copper) is used as a wick inside the plate type heat pipe 10.
Was arranged substantially along the inner wall. Further, the metal porous body 15 was placed so as to be in contact with any of the heat transfer columns 130 to 132. The metal porous body 15 is
To 132. Further, the metal porous body 15 is arranged so as to be in contact with only the lower plate 12 side (in the figure, the metal porous body 15 is drawn away from the lower plate 12, but this is convenient for illustration). Due to).

In this embodiment, as the metal porous body 15,
A cellular copper porous body having a cell diameter of about 0.3 mm, a porosity of 80%, and a thickness of 2.5 mm was applied (Example 1). Also, instead of the metal porous body 15, it is made of pure copper and has a wire diameter of 80 μm,
15 meshes are stacked and folded about 2.5m thick
Example (Example 2) in which a metal mesh molded body having a diameter of m was applied (Example 2).
Example 3 (Example 3) in which a copper nonwoven fabric having a m, a porosity of 60%, and a thickness of 2.5 mm was applied. Further, an example (Example 4) in which the size of the metal mesh of Example 2 was set to 5 mm in thickness and arranged so as to be in contact with both the upper and lower inner walls of the plate-shaped heat pipe 10 (Example 4).

For comparison, an example (Comparative Example 1) having no metal porous body 15 was prepared. In addition, the second embodiment described above
In the above, a metal mesh compact was used in place of the metal porous body 15, but the metal mesh compact was used as the heat transfer column 1
An example (Comparative Example 2) in which no contact was made with 30 to 132 was also prepared.

The cooling performance of Examples 1 to 4 and Comparative Examples 1 and 2 was examined. FIG.
4. The appearance of the plate-type heat pipes of Comparative Examples 1 and 2,
The semiconductor element 1 having a heating value of 100 W is provided
Each of the four semiconductor elements having a heating value of 5 W was mounted on the remaining four convex portions 121 via thermal conductive grease. Further, as shown in FIG. 2, fins 16 for heat radiation were mounted on the upper plate 11 side.

Then, electricity is supplied to the five semiconductor elements,
A temperature difference between two points TA and TB shown in FIG. 3 was examined.
At this time, the posture of the plate-type heat pipe 10 in FIG. 2 (referred to as the case of an installation angle of 0 °. This posture corresponds to the posture shown in FIG. 4A), and the case of the installation angle of 180 ° (installation angle Inverted posture at 0 °, ie, corresponds to the posture shown in FIG. 4A), and at an installation angle of 90 ° (installation angle of 0 °)
(C), ie, a posture rotated by 90 °, that is, a posture as shown in FIG. 4 (C)). Table 1 shows a value R (thermal resistance) obtained by dividing a temperature difference between two points of TA and TB by power consumption W, and R = (TA−TB) / W.

[0038]

[Table 1]

As can be seen from the results shown in Table 1, Comparative Examples 1 and 2 have a very large thermal resistance when the installation angle is 90 °. Even when the installation angle is 90 °, the thermal resistance is as small as 0.1 K / W or less, and excellent cooling performance is maintained. Therefore, it can be seen that the plate-type heat pipe of the present invention can achieve excellent cooling performance regardless of its posture.

[0040]

As described above, the cooling structure using the plate-type heat pipe of the present invention is sufficiently excellent even in the top heat mode in which the plate-type heat pipe is installed vertically or inclined. The cooling performance can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a plate-type heat pipe according to the present invention.

FIG. 2 is an explanatory view showing an example of a cooling structure using a plate-type heat pipe according to the present invention.

FIG. 3 is an external view showing an example of a plate-type heat pipe according to the present invention.

FIG. 4 is a diagram illustrating the attitude of a plate-type heat pipe.

FIG. 5 is a conceptual diagram schematically showing a metal mesh formed body and a metal porous body.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 plate heat pipe 11 upper plate 12 lower plate 130 heat transfer column 131 heat transfer column 132 heat transfer column 14 metal mesh 15 metal porous body 16 fin 20 semiconductor element 21 semiconductor element 22 semiconductor element 23 lead 120 convex part 121 convex part 40 plate type heat pipe 41 element to be cooled

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-6-129783 (JP, A) JP-A-10-209355 (JP, A) JP-A-7-208884 (JP, A) 73754 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F28D 15/02 H01L 23/427

Claims (6)

(57) [Claims] 1. A plate-type heat pipe provided to face a substrate on which an element to be cooled is mounted, wherein a heat transfer column is provided inside the plate-type heat pipe at a position corresponding to the element to be cooled. A metal porous body or a metal mesh formed body is arranged so as to be in contact with at least the heat transfer column having the largest heat absorption among the one or more heat transfer columns. Irrespective of the posture, the liquid phase of the working fluid is applied to at least one of the heat transfer column portion or the metal porous body having the largest heat absorption amount, or at least one of the heat transfer column portion or the metal mesh molded body having the largest heat absorption amount. A plate-shaped heat pipe whose parts are in contact. 2. The plate heat pipe according to claim 1, wherein the metal porous body or the metal mesh formed body is arranged so as to be in contact with one of upper and lower inner walls of the plate heat pipe. 3. The plate-type heat pipe according to claim 1, wherein the metal porous body or the metal mesh formed body is arranged in an intermediate region between upper and lower inner walls of the plate-type heat pipe. 4. The plate-type heat pipe according to claim 1, wherein a convex portion is formed at a position where the heat transfer column is disposed, on the outer shape of the plate-type heat pipe. 5. The metal porous body is formed integrally with a container of the plate-type heat pipe.
5. The plate-type heat pipe according to any one of 4. 6. The plate-shaped heat pipe according to claim 1, wherein the plate-shaped heat pipe is disposed opposite to a printed circuit board on which a semiconductor element is mounted as a device to be cooled. A cooling structure, wherein a heat sink is joined to the plate-shaped heat pipe.