JPH07332883A - Flat heat pipe and heat sink using the flat heat pipe - Google Patents

Abstract

PURPOSE:To provide a heat sink capable of carrying a great amount of heat swiftly, and what is more, uniformly. CONSTITUTION:This invention relates to a heat sink 9 where a flat heat pipe 1 is mounted to a heat transfer board 6 like fins where a wick is laid out at least to the peripheral edge of an interior of a sheet-like hollow in the heat pipe 1 and a hydraulic liquid is vacuum-sealed in the interior of the sheet-like hollow. Since the flat heat pipe 1 is mounted to the heat transfer board 6, it is, therefore, possible to cool a heating element 8 placed in contact with the heat transfer board 6 swiftly, and what is more, uniformly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat heat pipe capable of quickly and uniformly transporting a large amount of heat, and a heat sink using the flat heat pipe.

[0002]

2. Description of the Related Art A heat pipe is a heat transporter which is composed of a hermetically sealed container in which a working fluid is vacuum-sealed and which utilizes heat input and output during evaporation and solidification of the working fluid. Its heat transport is 100 times that of silver. The heat pipe is used for heat transportation such as a heat exchanger and air conditioning, heating for a boiler and bath, cooling for a high output amplifier for audio, a power transistor, a thyristor and the like.

The heat pipe is roughly classified into a siphon type and a wick type. The former is one in which a working fluid is vacuum-sealed in a closed container, and the latter is one in which a porous body called a wick is arranged in the vertical direction of the inner surface of the closed container. The wick has a function of promoting the return of the evaporated working liquid, and a wire net, a biscuit body, a fiber aggregate, or the like is used. This heat pipe is
One end is placed in contact with the heating element and the other end is placed away from the heating element. The working fluid evaporates and takes heat in the evaporation portion that is in contact with the heating element, and the vapor of the working fluid is condensed and released in the condensation portion that is away from the heating element. The heat pipe is used horizontally or with the condensing part facing upward.

As shown in FIG. 8, the heat sink has a plurality of cylindrical heat pipes 22 vertically arranged on a copper plate 16 in which a plurality of cylindrical heat pipes 12 are embedded. A heat sink 29 having the fins 13 attached thereto, a heat sink 39 having the metal fins 13 attached to the back surface of a panel-shaped heat pipe 14 having a passage for the working fluid formed therein in a predetermined pattern as shown in FIG. The heating element 8 is arranged below the heat sink 29 in the former case and above the heat sink 39 in the latter case.

[0005]

SUMMARY OF THE INVENTION Electronic equipment and power equipment equipped with devices such as transistors and thyristors are
There is a trend toward higher integration and larger capacity, and the amount of heat generated is also increasing. When cooling a power device that generates a large amount of heat, a high-performance heat sink that can quickly and uniformly transfer a large amount of heat is required. The conventional heat sinks shown in FIGS. 8 and 9 cannot meet such requirements. In particular, when the heating element was placed on the top as shown in FIG. 9, the function of the heat pipe was not utilized because the evaporation part of the heat pipe was on the top and the working fluid was not supplied. Therefore, the heat sink is placed on the heating element and used, and its use is limited in space. Further, even if the metal fins are air-cooled, there is a problem in that the heat conductivity of the metal fins is poor, so that the cooling ability varies depending on the distance from the air source, and uniform cooling cannot be achieved.

[0006]

The present invention has been earnestly studied in such a situation, and its purpose is to obtain a high-performance flat plate capable of rapidly and uniformly cooling a heating element. To provide a mold heat pipe, a heat sink using the flat heat pipe, and a method of using the heat sink. That is, the invention of claim 1 is a flat heat pipe characterized in that the wick is arranged at least at the periphery of the planar hollow body, and the working liquid is vacuum-sealed inside the planar hollow body. is there.

The present invention will be specifically described below with reference to the drawings. 1A and 1B are a perspective view and a cross-sectional view, respectively, showing an embodiment of the flat heat pipe of the present invention. The flat heat pipe 1 shown in FIG. 1 has a wick 3 arranged at the periphery of the inside 2 of the planar hollow body. The peripheral wick holding portion 4 is formed to have a circular cross section, and has a shape in which the wick 3 can be easily held. The working fluid is vacuum-sealed inside the hollow body 2 and the working fluid rises or falls due to the capillary force of the wick 3. For the wick, a porous material such as an aggregate of metal fibers of aluminum or copper, an aggregate of asbestos fibers, or heat-resistant glass wool is used. The same effect can be obtained by cutting a thin groove on the inner surface of the peripheral portion instead of the wick. Water, alcohol, freon, ammonia, organic medium, naphthalene, etc. are used as the working fluid. The wall of the flat heat pipe is made of aluminum,
Composed of copper, carbon steel, stainless steel, etc.

2A and 2B are a perspective view and a sectional view, respectively, showing another embodiment of the flat heat pipe of the present invention. Inside the planar hollow body 2, wick holding portions are formed at the peripheral edge portion and the central portion. The central wick holder 5 communicates with the peripheral wick holder 4 at its upper and lower ends. By providing the wick holding portion also in the center, the supply amount and the supply speed of the hydraulic fluid are increased. In this way, it is preferable that the wick holding portion is formed at a portion other than the peripheral portion inside the planar hollow body to promote the supply of the hydraulic fluid.

The flat heat pipe is manufactured as follows. That is, two aluminum plates each having a wick holding portion having a semicircular cross section at the peripheral portion and the central portion are prepared, and a wick is put into the wick holding portion of one of the aluminum plates.
Two aluminum plates are superposed on the inner surface of the outer peripheral portion so as to sandwich a brazing sheet so as to be mirror-finished, and the two superposed aluminum plates are held at a predetermined temperature in a soaking furnace to braze the outer peripheral portion. After brazing, the working fluid is added and the inside is evacuated to a vacuum and sealed.

A second aspect of the present invention is a heat sink in which the flat heat pipe according to the first aspect is attached to a heat transfer substrate in a fin shape.

FIG. 3 is a perspective view showing an embodiment of the heat sink of the present invention. A large number of recessed grooves 7 are formed in parallel on the surface of the heat transfer substrate 6, and the side portions of the flat heat pipe 1 shown in FIG. 2 are inserted into each of the recessed grooves 7 and soldered. The heating element 8 is arranged below the heat sink 9. The heat of the heating element 8 evaporates the working fluid in the flat heat pipe 1 via the heat transfer substrate 6. The vapor rises inside the hollow portion of the flat heat pipe 1 and condenses above the inside of the hollow portion. The heat of condensation is released above the flat heat pipe 1.

FIG. 4 uses the heat sink shown in FIG. 3 in a horizontal orientation. FIG. 5 shows the heat sink 9
The heat transfer board 6 is placed so that the heat transfer board 6 is on the top, and the heating element 8 is placed on the heat transfer board 6.

The heat transport mechanism when the heating element 8 is placed on the heat sink 9 (FIG. 5) will be described with reference to FIG. The heat transferred through the heat transfer substrate 6 causes the working fluid in the upper wick 3 in the flat heat pipe 1 to evaporate. The vapor contacts the liquid surface 15 of the hydraulic fluid 10 in the cavity and condenses. After the working fluid 10 is evaporated, the working fluid 10 is supplied to the wick 3 by rising in the wick 3 by a capillary force. The rise of the working fluid 10 in the wick 3 is also promoted by the increase in pressure due to the vapor in the space 17 in the cavity. In this way, the heat pipe and the heat sink of the present invention can obtain the required cooling effect even if the heat generating element is arranged on the upper side and used.

FIG. 7 is a perspective view showing another embodiment of the heat sink of the present invention. This heat sink 19 is a copper pipe 11
Eight concave grooves 7 are formed in parallel on the outer periphery of, and the flat heat pipe 1 is soldered to each of the concave grooves 7. The heat sink 19 passes the high-temperature exhaust gas of the boiler through the copper pipe 11 and allows clean outside air to flow around the copper pipe 11 to cool the exhaust heat. The clean outside air is heated and used as heating air or combustion air for the boiler. This heat sink
Since the heat radiation fin is composed of a flat heat pipe,
A large amount of exhaust gas can be treated. Hot wastewater can be treated in the same way.

In the present invention, the heat transfer substrate 6 is made of any metal plate material such as a copper plate or an aluminum plate having excellent thermal conductivity. The number of flat heat pipes 1 attached to the heat transfer substrate 6 is arbitrary. It is preferable that the contact area between the flat heat pipe and the heat transfer substrate is large. If the surface of the flat heat pipe is formed in a concavo-convex shape, the wind becomes a turbulent flow during the air cooling to improve the cooling efficiency.

[0016]

In the flat heat pipe of the present invention, the wick is arranged at least at the periphery of the inside of the planar hollow body, so that the vacuum-sealed hydraulic fluid moves quickly and uniformly in the wick by the capillary force. As a result, good heat transfer is achieved.
Even when the heating element is arranged in the upper part, the working liquid is supplied while rising in the wick by the capillary force, so that the cooling is sufficiently performed. Further, in the heat sink of the present invention, since the flat heat pipe is attached to the heat transfer substrate in a fin shape, the cooling effect by the fin is increased, and the heat generating element arranged in contact with the heat transfer substrate is cooled quickly and uniformly. It

[0017]

EXAMPLES The present invention will be described in detail below with reference to examples. (Example 1) The flat type heat pipe shown in FIG. 1 or 2 was used to cool a high frequency transformer for SMT incorporated in an electric device. Since there was no space above this transformer, four flat heat pipes were arranged side by side, and the side surface was directly soldered and attached to the bottom surface of the transformer. The lower part of the flat heat pipe was projected to the outside of the case and air-cooled by a fan. The flat heat pipe container was made of a 0.5 mm thick copper plate. The dimensions of the heat pipe are 70 mm in length, 40 mm in height, 4 mm in thickness of the flat surface, and 9 mm in outer diameter of the wick holder.
φ, water was used as the working fluid. An assembly of aluminum fine wires was used for the wick. When the temperature of the transformer in use was measured, the maximum transformer temperature was suppressed to 42 ℃. In the past, a small fan was placed in the case to cool it, but it often exceeded the allowable temperature (50 ° C).

(Embodiment 2) The flat heat pipe used in Embodiment 1 is soldered to the above-mentioned groove of a heat transfer substrate in which five grooves having a cross section of 5 * 5 mm are formed on a copper plate of 70 * 70 * 10 mm. Then, two types of heat sinks having the shapes shown in FIG. 3 were produced. The heat sink was placed on the audio amplifier with the heat transfer board facing down. For comparison, the same cooling experiment was performed on the heat sink using the cylindrical heat pipe shown in FIG. Experiments were performed both with and without air cooling of a flat heat pipe or metal fins. The results are shown in Table 1.

[0019]

[Table 1] * HP: heat pipe, HS: heat sink.

As is clear from Table 1, the product of the present invention (N
o.1, 2) was well below the allowable temperature (60 ° C) of the audio amplifier. Cooling was somewhat better with the heat pipe (No. 2) in which the wick was also placed in the center. On the other hand, No. 3 of the comparative example product was below the permissible temperature when it was air-cooled, and significantly exceeded the permissible temperature when it was not air-cooled.

Example 3 An audio amplifier was cooled using the heat sink of the present invention shown in FIG. The heat sink was placed with the heat conductive substrate facing upward, and the audio amplifier was placed on the upper surface of the heat conductive substrate. For comparison, the same cooling experiment was conducted for the conventional heat sink shown in FIG. The results are shown in Table 2.

[0022]

[Table 2] * HP: heat pipe, HS: heat sink.

As is clear from Table 2, the product of the present invention (N
o.4,5) slightly exceeded the permissible temperature (60 ° C) without air cooling, but fell below the permissible temperature by air cooling. On the other hand, the conventional heat sink greatly exceeded the allowable temperature. This is because the working fluid was hardly supplied above the heat pipe.

The flat heat pipe in which the aggregate (wick) of the aluminum fine wires is arranged in the peripheral edge of the planar cavity using the copper container has been described above, but the present invention uses another container such as aluminum. The same effect can be obtained when a heat pipe having other wicks arranged therein or having a narrow groove is used.

[0025]

As described above, according to the heat sink of the present invention, a high cooling effect can be obtained and a remarkable industrial effect can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view and a sectional view showing an embodiment of a flat heat pipe of the present invention.

FIG. 2 is a perspective view and a cross-sectional view showing another aspect of the flat heat pipe of the present invention.

FIG. 3 is a perspective view showing a heat sink of the present invention and a first usage example thereof.

FIG. 4 is a perspective view showing a second usage example of the heat sink of the present invention.

FIG. 5 is a perspective view showing a third usage example of the heat sink of the present invention.

FIG. 6 is an explanatory view of a heat transport mechanism of the square heat pipe of the present invention.

FIG. 7 is a perspective view showing a fourth mode of the heat sink of the present invention.

FIG. 8 is a perspective view showing a conventional heat sink and a usage example thereof.

FIG. 9 is a perspective view showing a conventional heat sink and a usage example thereof.

[Explanation of symbols]

 1 ────── Flat heat pipe 2 ────── Inside the planar cavity 3 ────── Wick 4 ────── Perimeter wick holding part 5 ─────── Central wick holder 6 ────── Heat transfer board 7 ────── Recessed groove 8 ─────── Heating element 9,19,29,39 ─ Heat sink 10 ────── Liquid 11 ─────── Copper pipe 12,22 ──── Cylindrical heat pipe 13 ────── Metal fin 14 ────── Panel heat pipe 15 ────── Working fluid Liquid level 16 ────── Copper plate with a cylindrical heat pipe embedded 17 ────── Space inside the cavity

Claims (2)

[Claims] 1. A flat heat pipe, wherein a wick is arranged at least at the periphery of the inside of the planar hollow body, and the working liquid is vacuum-sealed inside the planar hollow body. 2. A heat sink comprising the flat heat pipe according to claim 1 attached to a heat transfer substrate in a fin shape.