JPH0632409B2 - Electronic device cooling device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for efficiently cooling a plurality of electronic elements such as integrated circuits mounted on a circuit board and requiring cooling.

Conventional technology LSI (Large scale integratio) that generates heat when energized
With regard to electronic elements such as n), the amount of heat generated by each element increases with the increase in the degree of integration, and the cooling capacity of the conventional air-cooled cooling method exceeds the limit of its cooling capacity, so that it cannot be cooled sufficiently. .

There is also a forced convection type cooling method as a water cooling type cooling method, but this cooling method may cause a trouble such as a short circuit of the circuit due to water leakage, and a large heat generation exceeding the cooling capacity. Since a large number of elements are also used, a cooling method having higher cooling capacity than the water cooling type and not causing trouble such as short circuit has been required.

Therefore, as a cooling method having a high cooling capacity, a cooling method such as fluorocarbon or the like having an electrically insulating property is used, and an electronic element is directly immersed in this refrigerant to perform boiling cooling, that is, an immersion boiling cooling method ( Immersion cool
ing) is being developed.

In this immersion boiling cooling method, the heating element that is the object to be cooled is immersed in a refrigerant that boils at a temperature below the target temperature for cooling, and the refrigerant directly contacts the surface of the heating element to remove heat and cool it. In addition, when the heating element is heated to the boiling point of the refrigerant,
First, cooling is performed by so-called pool boiling heat transfer that occurs under natural convection conditions, and if the heating element is further heated without being completely cooled by pool boiling heat transfer and the temperature difference with the refrigerant becomes large, the surface of the heating element increases. The refrigerant is nucleate-boiling to generate bubbles, and when the bubbles leave the surface of the heating element and float up, large heat transfer is caused by the disturbing effect, so-called nucleate boiling heat transfer effectively cools the heating element. This is a cooling method in which the temperature of the heating element is kept below a certain temperature by boiling the refrigerant with the heat of the heating element so that the temperature does not rise any higher.

Further, a falling liquid film method has been proposed as a cooling method having higher cooling efficiency than the immersion boiling cooling method. This liquid drop film method is a method in which a cooling liquid forms a film and is cooled by flowing down so as to wrap around the surface of an object to be cooled. For example, the cooling device for an electronic element shown in FIG. 3 is hermetically sealed. The condenser 2 is arranged in the upper part of the container 1, the reservoir 3 is provided in the middle stage of the container, and the cooling liquid R having an electric insulation property stored in the reservoir 3 is provided in the bottom of the reservoir 3. A plurality of downflow pipes 4 that flow to the bottom are provided substantially vertically, and circuit boards 5 are arranged so as to configure a part of the wall of each of these downflow pipes 4. A circulation pipe 7 having a pump 6 interposed is provided between the bottom of the container 1 and the reservoir 3.

With this configuration, when the cooling liquid R stored in the reservoir 3 flows down in each of the downflow pipes 4, the downflowing cooling liquid R forms a part of the wall of the downflow pipe 4. The electronic elements 5a that generate heat when they flow down in a film form on the surfaces of the plurality of electronic elements 5a attached to the circuit board 5
Removes heat from the product and cools it efficiently. And each downflow pipe 4
The cooling liquid R that has flowed down is collected at the bottom of the container 1 and returned to the reservoir 3 by the pump 6 via the circulation pipe 7.

In addition, a part of the cooling liquid R collected at the bottom of the container 1 is
The liquid evaporates and moves upward in the container 1, the heat is taken by the condenser 2, the condensed liquid returns to the liquid-phase cooling liquid, and the liquid drops and is collected in the reservoir 3. Reference numeral 8 is an overflow pipe.

However, when cooling a plurality of electronic elements mounted on a circuit board by the conventional liquid drop film method as in the case of the cooling device, each electronic element 5a is individually connected. Since the pump 6 and the circulation pipe 7 are used as means for returning the cooling liquid that has cooled down and accumulated at the bottom to the reservoir 3, the space for disposing the pump 6 and the circulation pipe 7 is required. There was a problem that electric power was needed to drive the pump.

This invention was made under the technical background described above,
An object of the present invention is to provide a cooling device for an electronic element by a falling liquid film method that has high cooling performance and does not require power such as a pump to pump the cooling liquid to an upper reservoir.

Means for Solving the Problems As a means for solving the above problems, the cooling device for an electronic element according to the present invention is such that a lower part in a sealed container is a storage part of a refrigerant, and heat is externally supplied to an upper part in the container. A circuit board provided with a condenser to take away and an electronic element requiring cooling in the refrigerant stored in the storage section is arranged so as to be immersed and boil-cooled, and is below the condenser and in the storage section. A reservoir for collecting the condensed and dripping refrigerant is provided above, and a liquid return pipe for returning the refrigerant to the reservoir is provided at the bottom of the reservoir, and a part or all of the pipe wall is formed of a circuit board. It is characterized in that the electronic element attached to the circuit board is arranged so that the liquid film is cooled by the coolant flowing down in the pipe.

When a plurality of electronic elements mounted on the circuit board placed in the refrigerant stored in the bottom of the container generate heat, these electronic elements are immersed and cooled by immersion, and the refrigerant evaporates due to the heat taken from the electronic elements. , Becomes vapor and moves upward in the container. Then, the vapor of the refrigerant that has been deprived of heat by the upper condenser returns to the liquid-phase refrigerant and drops into the reservoir, and the refrigerant collected in the reservoir is the liquid that is connected to the bottom of the reservoir. It flows down to the bottom of the container through the return pipe. At this time, the refrigerant flowing down in the liquid return pipe flows in the form of a liquid film that wraps the surfaces of the plurality of electronic elements mounted on the circuit board forming a part of the wall of the liquid return pipe. It takes the heat of the element and cools it. Further, the refrigerant that has flowed down in the liquid return pipe flows into the refrigerant reservoir in the lower portion of the container, and the circuit board immersed in the refrigerant reservoir is subjected to immersion boiling cooling of the electronic element, and then repeatedly boiled and evaporated. Here, the liquid-phase refrigerant flowing from the reservoir in the upper part of the container to the refrigerant reservoir in the lower part of the container is
In the refrigerant pool, it receives heat from the electronic element and boils.
The vapor is evaporated, and the vapor is condensed by the condenser to become the liquid phase again and is dropped into the reservoir, so that the vapor is returned to the reservoir. That is, the heat given from the electronic element in the refrigerant reservoir in the lower part of the container serves as a power source to return the refrigerant to the reservoir. Therefore, unlike the case of the conventional general liquid drop film cooling device, external power (pump or the like) for returning the refrigerant from the refrigerant reservoir to the reservoir is not particularly required.

First Embodiment Hereinafter, a first embodiment of a cooling device for an electronic element according to the present invention will be described.
A description will be given with reference to FIGS.

The closed box-shaped container 11 has a condenser 1 above the inside thereof.
2 is provided, and a reservoir 13 is provided in the middle stage of the container 11 below the condenser 12. The reservoir 13 has a U-shaped cross-section, and in the depth direction of the container 11 (up and down in FIG. 2) with spaces for steam passages left on both sides in the width direction (left and right direction in FIG. 1) of the container 11, respectively. Direction), and is provided in a liquid-tight saucer shape, and a condensable refrigerant R having electrical insulation such as fluorocarbon is stored in the lower portion of the container 11. . Also, this container 1
1 has a plurality of LSs each having a large heat generation amount.
The circuit board 14 on which the I14a is mounted is fitted so that the surface on which the LSI 14a is mounted is inside the container 11, and forms a part of the bottom plate.
4a is electrically connected so as to function, and these LSIs 14a are subjected to immersion boiling cooling in the stored refrigerant R.

Further, four slits 13b are formed in the bottom portion 13a of the reservoir 13 at substantially equal intervals and in a length that is full of the inner dimension of the container 11 in the depth direction.
Is connected to the lower surface of the bottom portion 13a in a liquid-tight manner, and two plate members having the same width as the inner dimension in the depth direction are provided substantially vertically apart from each other by the width of the slit 13b. The two liquid return tubes 15 having a rectangular cross section are formed by liquid-tightly contacting both side edges of the both wall surfaces of the container 11 which face each other in the depth direction. Further, the gap width of each slit 13b and the interval between the pipe walls of each liquid return pipe 15 are such that the refrigerant flowing down in the liquid return pipe 15 has a thickness of about 0.
It is set so that it forms a liquid film of about 5 mm and flows down. Further, each liquid return pipe 15 is liquid-tightly connected to the merging pipe 16 at a height where the lower part thereof is below the liquid surface of the refrigerant R stored in the container lower part.
Are arranged substantially horizontally, and their ends open toward the bottom 11a below the liquid surface and in the vicinity of the side wall of the container 11 deviated from the center of the container 11.

Then, the refrigerant R stored in the lower portion of each liquid return pipe 15
Above the liquid surface of the LS, multiple LSs that require cooling
The circuit board 17 on which the I17a is mounted is provided so as to form a part of one pipe wall of each liquid return pipe 15 with the surface on which the LSI 17a is mounted facing the inside of the pipe. The boards 17 are electrically connected to each other so that each LSI 17a is connected to the reservoir 1
3, the refrigerant R flowing down the respective liquid return pipes 15 is cooled by the falling liquid film method.

Next, the operation of this embodiment will be described.

The circuit board 14 that is immersed in the refrigerant R stored in the lower portion of the container 11 and cooled by the immersion boiling cooling method is
When the LSI 4a is energized and heat is generated, the refrigerant R takes heat from the surface of each LSI 14a that has generated heat to cool it. When the taken heat raises the temperature of the refrigerant R to the boiling point, the refrigerant R boils. The heat is dissipated by evaporating from the liquid surface, and the pool boiling heat transfer that occurs under natural convection conditions cools each LSI 14a that is generating heat.

Further, when the heat generation amount of each LSI 14a increases and exceeds the cooling capacity by the pool boiling heat transfer, and each LSI 14a becomes even higher in temperature, nucleate boiling occurs on the surface of each LSI 14a in contact with the refrigerant R and a large amount of nucleate boiling occurs. Generates bubbles of steam. Each LSI 14a is effectively cooled by the nucleate boiling heat transfer that causes a large heat transfer due to the disturbing effect when the generated bubbles float on the surface. Then, a large amount of the generated vapor moves to the space above the liquid surface, the heat is taken by the condenser 12, is condensed and returns to the liquid phase, and is dripped into the reservoir 13 and collected. The condenser 12 carries the heat taken from the vapor of the refrigerant R to the outside or outside of the device and releases it.

Then, the liquid-phase refrigerant R accumulated in the reservoir 13 is supplied from the slits 13b formed in the bottom portion 13a to the liquid return pipe 15
It flows in and flows down in each pipe. At this time, the flowing-down refrigerant R flows in the form of a liquid film so as to cover the surface of each LSI 17a of the circuit board 17 forming a part of the tube wall of each liquid return pipe 15, and heat of each LSI 17a is transferred. It is deprived and cooled by the so-called falling film method. Particularly, in this embodiment, since only the refrigerant R condensed by the condenser 12 is collected in the reservoir 13 and used for the liquid drop film cooling, as in the case of the conventional liquid drop film cooling, Unlike the case where a refrigerant that has been once used for cooling the falling film is heated and pumped up to a reservoir for reuse, the cooling efficiency is kept constant because the low-temperature refrigerant flows down the surface of the object to be heated to cool it. Is even higher.

The refrigerant R that has taken heat from each LSI 17a and has risen in temperature when flowing down flows into a single confluent pipe 16 that connects the lower portions of the respective liquid return pipes 15, and from the vicinity of the side wall deviated from the center of the container 11, In the refrigerant R stored in the lower part, the bottom part 1
It is discharged toward the 1a direction. In this way, the liquid return pipe 1
After the refrigerant flowing down the inside of the container 5 is joined to the joining pipe 16, the refrigerant R is discharged into the refrigerant R in the vicinity of the side wall of the container 11, so that the refrigerant R discharged from the liquid return pipe 15 is stored in the lower part of the container. In R, the smooth floating of bubbles of vapor generated on the surface of each LSI 14a of the circuit board 14 cooled by the immersion boiling cooling method is not hindered.

EFFECTS OF THE INVENTION As described above, the cooling device for electronic devices of the present invention is
Refrigerant is stored in the bottom of a closed container with a condenser provided in the upper part, a circuit board with electronic elements is placed in this refrigerant for immersion boiling cooling, and the refrigerant stored in the lower part of the container is positively charged. It is evaporated and moved to the upper part of the container, condensed by a condenser and collected in a reservoir, and the refrigerant collected in this reservoir is made to flow down in the liquid return pipe to form a part of the pipe wall. Since the electronic element attached to the circuit board is cooled by the liquid drop film method, cooling is performed by the liquid drop film method by the always low temperature refrigerant condensed in the condenser and collected in the reservoir. Compared with the cooling device using the liquid drop film method of No. 1, a higher cooling capacity is obtained, and the pump and piping for pumping the refrigerant stored in the lower part of the container to the upper reservoir are not required, which reduces the cost and It is possible to miniaturize the device, also have an effect, such as energy saving can be achieved.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of an electronic cooling device, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. It is sectional drawing of the cooling device of the electronic element by the conventional liquid drop film method. 11 ... Container, 11a ... Bottom, 12 ... Condenser, 13 ... Reservoir, 13a ... Bottom, 13b ... Slit, 14, 17 ...
Circuit board, 14a, 17a ... LSI, 15 ... Liquid return tube,
16 ... Junction pipe, R ... Refrigerant.

Front Page Continuation (72) Inventor Ryuichi Okiayu 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Line Co., Ltd. (72) Masataka Mochizuki 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Electric Line Co., Ltd. In-house (72) Inventor Anthony F. Matalk United States, California, Los Altos, William Henry Coat, 1700 (72) Inventor Jonsey Hanshker, California, Morgan Hill, Pinto Court, 2520 (56) References JP-A-50-26142 (JP, A) JP-A-59-129577 (JP, A) JP-A-49-92549 (JP, A)

Claims (3)

[Claims] 1. A refrigerant storage part is provided in the lower part of a closed container, and a condenser for removing heat to the outside is provided in the upper part of the container.
A circuit board having an electronic element that requires cooling is arranged in the refrigerant stored in the storage section so as to be cooled by immersion boiling, and is condensed below the condenser and above the storage section. Provide a reservoir for collecting the dripping refrigerant,
Further, a liquid return pipe for returning the refrigerant to the reservoir is formed at the bottom of the reservoir, and a part or all of the wall of the pipe is formed by a circuit board, and the electronic element attached to the circuit board is dropped by the refrigerant flowing down the pipe. A cooling device for an electronic element, which is arranged so as to be film-cooled. 2. A plurality of the liquid return pipes are provided, and the lower ends of the plurality of liquid return pipes are above the circuit board whose opening ends are below the liquid surface of the refrigerant in the reservoir and are cooled by immersion boiling. The cooling device for an electronic element according to claim 1, wherein the cooling device is connected to a merging pipe arranged at a position apart from the above. 3. The cooling device for an electronic element according to claim 1, wherein the liquid return pipe is insulated from the atmosphere in a closed container.