JP2003139453A - Electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a connection method and reliability thereof for a passage for transferring heat of a heating element across a hinge part by means of a liquid, in a portable electronic transfer device with the hinge part capable of opening and closing motion. SOLUTION: A flexible tube 306 is used as the passage in the hinge part. The flexible tube is provided with partly thickened portions 304 near an end, and the worked portions are fitted in a holder 305 preformed on a case. Bands 302 and 303 are used in combination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device equipped with a cooling device for cooling a semiconductor element that generates heat with a circulating liquid.

[0002]

2. Description of the Related Art A conventional technique is disclosed in JP-A-6-266474.
See, for example, Japanese Patent Laid-Open No. 7-142886.
In the example of Japanese Patent Laid-Open No. 6-266474, an electronic device including a main body housing that houses a wiring board on which a heating element is mounted and a display device housing that includes a display panel and is rotatably attached to the main body housing, A structure is shown in which the heat receiving jacket attached to the heat generating element, the heat radiating pipe installed in the display housing and the liquid driving mechanism are connected by a flexible tube. Further, in Japanese Patent Laid-Open No. 7-142868, an example of Japanese Patent Laid-Open No. 6-266474,
An example in which the housing is made of metal is shown.

In these examples, the heat generated in the heating element is transferred to the heat receiving jacket, and the heat is transferred from the heat receiving jacket to the heat radiating pipe by driving the liquid by the liquid driving mechanism to radiate to the outside air.

[0004]

In an electronic device represented by a portable personal computer or the like, the semiconductor element is remarkably heated due to the improved performance. On the other hand, it is desired to reduce the size and thickness of the case suitable for carrying.

The above-mentioned publicly known examples all have a structure in which the heat generated by the heat generating element is transferred to the display side to radiate heat in response to higher heat generation of the heat generating element. The heat transfer from the heating element to the display side is performed by driving the liquid between them, but the driving amount of the liquid and the operating pressure are not taken into consideration. Further, there is no specific description about the connection of each element for circulating the liquid, that is, the heat receiving jacket, the heat radiating pipe, the pump, and the flexible tube. In particular, the reliability of these connection methods is an essential issue before cooling, and the practical application of this cooling technology is achieved only after ensuring this reliability.

An object of the present invention is to provide a liquid drive device having a large size by defining necessary and sufficient liquid circulation conditions with respect to an increase in the heat generation amount of a heat generating element accompanying the improvement in processing performance of an electronic device.
It is an object of the present invention to provide a water-cooling structure suitable for downsizing and thinning and a method for connecting respective elements by optimizing operating conditions.

[0007]

The above object is to provide a first housing in which a semiconductor element is mounted, and a second housing in which a display device is housed and which is rotatably supported by the first housing. A heat receiving member that is in thermal contact with the semiconductor element; a heat radiating member that is in thermal contact with the inner surface of the second housing; and a liquid driving unit that drives a liquid medium between the heat receiving member, In an electronic device including a heat receiving member, the heat radiating member, and a flexible tube connecting the liquid driving unit, a band covers the connecting portion of the flexible tube connecting the heat receiving member, the heat radiating member, and the liquid driving unit. This is achieved by fixing a flexible tube near this band to a holder provided in the first housing.

The above object can be achieved when the circulating flow rate of the liquid medium is 120 μl / sec or more.

The above object can be achieved when the circulating flow rate of the liquid medium is 1200 μl / sec or less.

The above object can be achieved by setting the height of the liquid driving means to 30 mm or less.

Further, the above object can be achieved by the liquid driving means having a flat shape and the flat shape being a flat shape in the thickness direction of the first casing.

Further, the above object is achieved by the inner diameter of the flexible tube being larger than the inner diameter of the heat dissipation member.

[0013] Further, the above object is to provide a first housing in which a semiconductor element is mounted inside, and a display device inside to store the first device.
A second housing rotatably supported by the housing, a heat receiving member in thermal contact with the semiconductor element, a heat radiating member in thermal contact with the inner surface of the second housing, and the heat receiving member. In an electronic device including a liquid driving unit that drives a liquid medium between them, and a flexible tube that connects the heat receiving member, the heat radiating member, and the liquid driving unit, the heat receiving member, the heat radiating member, and the liquid driving unit. This is achieved by providing a joint that can change the angle of the flow path direction arbitrarily at the connection portion of the flexible tube that connects the and, and the joint is formed of a rigid body.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Electronic equipment devices, so-called personal computers (hereinafter referred to as personal computers) include portable notebook type personal computers and desktop type personal computers mainly used on desks. In each of these personal computers, the demand for high-speed processing and large capacity has been increasing year by year, and as a result of satisfying these demands, the heat generation temperature of the CPU, which is a semiconductor element, has increased. This trend is expected to continue in the future.

On the other hand, these current personal computers are
An air-cooled type such as a fan is generally used. This air-cooled type
There is a limit to the heat dissipation capability, and there is a possibility that it will not be possible to follow the heat dissipation of the semiconductor element that tends to generate high heat as described above. However, although it is possible to deal with the problem by rotating the fan at high speed or increasing the size of the fan, it is not realistic because it goes against the noise reduction and the weight reduction of the personal computer.
On the other hand, there is an apparatus that circulates a liquid medium such as water to cool a semiconductor element as heat radiation instead of the conventional air-cooled heat radiation. This cooling device is a large-scale device that is mainly used for cooling a large computer used in a company or a bank, and forcibly circulates cooling water with a pump and cools it with a dedicated refrigerator.

Therefore, for a laptop computer that is frequently moved or a desktop computer that may be moved due to a relocation in the office, the water cooling device described above is used as an example. Even if the cooling device is downsized, it cannot be mounted at all.

Therefore, as in the above-mentioned prior art, various water cooling devices that can be mounted on a small personal computer have been studied, but at the time of application of this prior art, the heat generation temperature of the semiconductor element was not as high as in recent years. Even now, personal computers equipped with water cooling devices have not been commercialized.

On the other hand, according to the present invention, by making the casing forming the outer shell of the computer main body an aluminum alloy or a magnesium alloy having a good heat dissipation property, the water cooling device can be greatly downsized, and it can be used in a personal computer. Can be installed. However, even though the liquid medium is in a closed space, it is the most important issue to prevent the liquid medium from leaking, especially in a notebook type personal computer that is frequently moved. Although there is a problem of liquid permeation from the flexible tube, it is clear that the part where liquid leakage may occur is the connecting part of the pipe.

Therefore, the present invention has been variously studied in order to prevent liquid leakage from the connecting portion of the pipe.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an electronic device including an embodiment of the present invention. In FIG. 1, the electronic device is a main body case 1
A display case 2 having a display, a keyboard 3 installed in the main body case 1, a wiring board 4 having a plurality of elements mounted thereon, a hard disk drive 5,
An auxiliary storage device (for example, a floppy disk drive, a CD drive, etc.) 6 or the like is installed. On the wiring board 4, a semiconductor element (hereinafter referred to as a CPU) such as a CPU (central processing unit) 7 having a particularly large heat generation amount is mounted. A water cooling jacket 8 is attached to the CPU 7. The CPU 7 and the water cooling jacket 8 are connected via a flexible heat conducting member (for example, Si rubber mixed with a heat conducting filler such as aluminum oxide). Further, on the back surface (inside the case) of the display case 2, a metal heat dissipation plate 10 to which a heat dissipation pipe 9 shown by a dotted line is connected is installed. The display case 2 itself may be made of metal (for example, an aluminum alloy or a magnesium alloy), and the metal heat dissipation plate 10 may be omitted, and the heat dissipation pipe 9 may be directly connected to the display case 2. Further, a pump 11 which is a liquid transportation means is installed in the main body case 1. Water cooling jacket 8, radiation pipe 9, pump 1
1 are connected by flexible tubes 12, 13 and 14.

FIG. 2 is an enlarged perspective view of a joint portion between the hoop and the flexible tube. In FIG. 2, the pump 11 is provided with a pipe-shaped joint 202 for inserting the flexible tube 13. This joint 2
02 is formed integrally with the pump 11. In this embodiment, the portions where the flexible tube 13 is inserted into the joint 202 formed of such a pipe-shaped rigid tube are, in this embodiment, both ends of the flexible tube 14 that connects the heat radiation pipe 9 and the pump 11, the pump 11 and the water cooling jacket. There are a total of 6 locations at both ends of the flexible tube 13 connecting the water cooling jacket 8 and the flexible tube 12 connecting the water cooling jacket 8 and the heat radiation pipe 9. For example,
Although the portion in which the flexible tube 14 is inserted into the heat radiating pipe 9 is not shown in FIG. 1, it has a joint structure as shown in FIG. 3, so that sealing performance and reliability are ensured.

FIGS. 3A and 3B are perspective views schematically showing the band and the joint portion fixed by the band. In FIG. 3, the heat radiating pipe 9 into which the flexible tube 14 is inserted or the joint portion is provided with a band at any portion. This band is shown in Figure 3.
As shown in (a), it comprises a main band 302 and an auxiliary band 303. Further, as shown in FIG. 3B, the flexible tube 14 is provided with a portion 304 having a partly thickened outer diameter, and a holder 305 which is made in advance in a case of an electronic device or the like.
It is designed to be incorporated into.

The operation of this electronic device will be described. The heat dissipation area on the back surface of the display case 2 is around 90,000 mm ² in a typical portable electronic device. Since the form of heat dissipation is natural convection and heat radiation, the thermal resistance related to the heat dissipation is
It is uniquely determined only by the area and is around 0.8 ℃ / W. On the other hand, the upper limit temperature at which the operator does not feel discomfort when touching the case surface is about 25 ° C. as a temperature rise value from the outside air temperature. Therefore, when the temperature rise value on the back surface of the display case is uniform at 25 ° C., there is a limit to the amount of heat that can be radiated from the back surface of the display case, and the limit heat radiation amount is about 30 W. On the other hand, the upper limit temperature of the CPU 7 is generally 95 ° C.
Therefore, the required circulating fluid amount is determined from the relationship between the limit heat radiation amount and the upper limit temperature of the CPU.

FIG. 4 is a block diagram schematically showing a heat radiation path of the electronic device. The circulating liquid amount of the cooling device will be described with reference to FIG. Note that the outside air temperature is 35 ° C for simplicity.
(Maximum outside temperature of the operating environment). In FIG. 4, the thermal resistance R1 between the CPU and the water cooling jacket is 0 ° C. /
Even in the ideal case of W, the upper limit of the refrigerant liquid is 95 ° C., which is the same as that of the CPU, and on the other hand, if the heat dissipation from the heat dissipation pipe is ideally performed, the refrigerant liquid drops to 35 ° C., which is the same as the outside air temperature. That is, the maximum value of the temperature rise of the refrigerant liquid (liquid temperature Th-Tl) is 60 ° C. Therefore, when the refrigerant liquid is water, the circulation flow rate is 120 μl / sec from the density of water of 998 kg / m ³ and the specific heat of 4180 J / kgK, and this circulation amount is the lower limit. On the other hand, when a sufficient circulation flow rate is obtained (temperature rise of the refrigerant liquid (liquid temperature T
Assuming that h-Tl) is approximately 0 ° C.), the maximum sum of the temperature difference between the CPU and the water cooling jacket and the temperature difference between the heat radiating pipe and the outside air temperature is 60 ° C. By designing, considering the manufacturing error as 10% of the maximum of this temperature difference of 60 ° C, the circulation flow rate is 1200 µl / sec, assuming that the temperature rise of the refrigerant liquid (liquid temperature Th-Tl) is 6 ° C. . In other words, the circulation flow rate is 1
200 μl / sec or less is sufficient, and even if it is circulated above this flow rate, the cooling performance is almost saturated. Circulating above this flow rate requires an excessive capacity of the pump (expansion of size, increase of power consumption) It just makes no sense.

This can be understood from the relationship between the circulation flow rate and the water cooling jacket temperature shown in FIG. FIG. 5 shows a CPU
Heat value 30W, outside air temperature 35 ℃, inner diameter 1.5mm, length
1.5m radiating pipe, cross section of flow path 3mm x 3mm, length 30mm
FIG. 6 is a diagram showing the relationship between the circulation flow rate and the water cooling jacket temperature when a water cooling jacket having eight channels is used.
In FIG. 5, in the region where the circulation flow rate is 1200 μl / sec or more, the water cooling jacket temperature hardly changes as the flow rate increases.

The following relationship approximately holds between the temperature Twj of the water cooling jacket and the circulation flow rate Q. Assuming that the density and the specific heat of the refrigerant liquid are ρ, Cp, the calorific value Qc of the CPU, the outside air temperature Ta, and the area A of the metal radiator plate, Qc = ((Th + Tl) / 2-Ta) .12.A-- (1) Qc = ρ ・ Cp ・ Q ・ (Th-Tl) ―― (2) Twj ＝ Th ―― (3) Therefore, Q = 6 ・ A ・ Qc / [(12 ・ A ・ (Twj-Ta) -Qc) ρCp]-(4) That is, in order to cool the water cooling jacket to a predetermined temperature Twj, it is necessary to circulate at least the flow rate represented by the equation (4). Since the density and specific heat of the refrigerant liquid change depending on the liquid temperature, the values at the liquid temperature during operation are used.

FIG. 6 is a side sectional view of the electronic device of this embodiment (in a state where the display case is closed). In FIG. 6, in the case of a portable electronic device, the thickness of the housing (in the state where the display case is closed) is preferably about 50 mm or less in consideration of portability, handleability when carried, and the like. At this time,
The breakdown of the dimension in the thickness direction is shown in FIG.
mm is the display case front surface 616, the back surface 613, the main body case upper surface 617, and the lower surface 618 are four surfaces, and the heat dissipation pipe 60
The diameter of 9 is around 3 mm, and the thickness of metal heat sink 10 is 0.2 to 0.5.
mm, the thickness of the display panel 615 is 5-10 mm,
The minimum dimension of the housing is to occupy the thickness direction in any cross section. Therefore, the height of the pump 611 itself needs to be at most 30 mm or less.

In the case of a volume change type pump, if the stroke of the volume change is constant, the structure capable of changing the volume in the flat surface direction can increase the variable volume and increase the circulation flow rate. Therefore, in the portable electronic device, it is necessary that the pump size is made larger in the surface direction than in the height direction, that is, the pump shape and installation method are flat in the thickness direction of the housing. On the other hand, in the case of a centrifugal pump,
Increasing the flow rate is more effective by making the size in the radial direction larger than in the height direction (the flow rate is proportional to the square of the radial dimension, whereas it is proportional to the square of the radial dimension). For). That is, as in the case of the volume change type pump, the shape and installation method of the pump must be flat in the thickness direction of the housing.

The heat dissipating portion is thermally connected to a metal heat dissipating plate 610 in which the heat dissipating pipe 609 is in contact with the inside of the display case rear surface 613. The display case back surface 613 itself may be a metal such as an aluminum alloy or a magnesium alloy, in which case the case itself serves as a heat dissipation plate. It is desirable that the heat radiating pipe 609 crawls on average as shown in FIG. 1 in order to radiate heat from the heat radiating plate 610 in a nearly uniform state. For this reason, it is necessary to fold it back onto the heat sink 610 in a few turns and crawl it, and in the case of a typical portable electronic device (around 300 mm in width), the flow path length is 1 to 1.5 m. That is, the heat dissipation pipe 609 occupies most of the circulation flow path. Furthermore, the heat dissipation pipe 60
9 is installed between the display panel 615 and the back surface 610 of the display case, the heat dissipation pipe 609
It is desirable that the diameter of is as small as possible. Therefore, most of the flow path resistance of the circulation flow path is occupied by the heat radiation pipe portion. On the other hand, it is desirable that the flow path resistance is as small as possible in view of the matching between the operating flow rate and flow path resistance of the pump 611 and the pump characteristics. Therefore, at least the diameter of the pipe (flexible tube) in the main body case is preferably larger than that of the heat dissipation pipe 609. Also,
Even if the heat dissipation pipe 609 is made longer than the above length, the heat dissipation effect in the metal heat dissipation plate 610 works so that the heat dissipation performance is hardly changed. Therefore, it is not necessary to make the length of the heat radiation pipe longer than the above length in order to reduce the flow path resistance. In the above case, the inner diameter of the heat dissipation pipe is 1.5 mm and the length is
When the length is 1.5 m, the inner diameter of the tube that connects the water cooling jacket, pump, and radiating pipe is 2.0 mm, and the length is 0.5 m, the flow resistance is about 1 at the maximum circulating flow rate when the refrigerant liquid is water. 7x10 ⁴ Pa (the flow resistance in the water-cooling jacket and the connection part can be ignored compared to the heat radiation pipe part), and the pump power that can discharge at a pressure of at least 1.7x10 ⁴ Pa or more is required. When an antifreeze liquid is used as the refrigerant liquid, the antifreeze liquid generally has a larger viscosity coefficient than water, and thus requires a larger pressure. When the density and viscosity coefficient of the refrigerant liquid are ρ and μ, the heat dissipation pipe inner diameter is d, the length L and the flow rate Q, the flow resistance ΔP is represented by ΔP = 128 μLQ / (πd ⁴ )-(5) Be done. Since the density and the viscosity coefficient of the refrigerant liquid change depending on the liquid temperature, the values at the liquid temperature during operation are used. The pump has the ability to flow over a predetermined flow rate under the flow resistance obtained by the equation (5) (equation (5)
(Having a discharge pressure equal to or higher than the flow resistance obtained in step 1) is used. On the other hand, the enclosed amount of circulating fluid should be at least 3 cc,
Even considering the liquid pool for liquid leakage, 6cc is enough.

From the above description, the pressure required to simply circulate the liquid is at most several tens of kPa, but it is necessary to take the water vapor pressure of the liquid into consideration. When the circulating liquid is water, the water vapor pressure at a temperature of 100 ° C. is 100 kPa.

As described above, the upper limit temperature of the heating element, that is, the CPU assumed in this embodiment is 95 ° C. Therefore, it is sufficient to assume a pressure load of about 200 kPa at maximum in the liquid cooling system. A band having the shape shown in FIG. 3A was used to provide a pressure resistance of 200 kPa.
The circumference of this band can be widened by pinching the tab 301, and when mounting on a flexible tube, the auxiliary band 3
03, and fix the claw 301 so that the claw 301 does not move at the portion 304. The band is made of SUS spring material with a thickness of 0.3 mm. Here, the role of the band is to secure pressure resistance against the pressure of the liquid in the circulation system. Therefore, it has a sufficient tensile strength against the pressure currently considered, and the thermal deformation (expansion, softening) can be ignored at the temperature of the environment where this band is used (the maximum temperature of liquid is 95 ° C). Any material may be used as long as it is a material. However, an elastic spring material is preferable in consideration of workability when the pipe and the flexible tube are attached to the connecting portion.

In the embodiment shown in FIG. 1, the flexible tube connecting between the heat radiation pipe and the pump and between the water cooling jacket and the heat radiation pump is particularly important. The display case and the main body case are frequently opened and closed. Therefore, the flexible tube used for connecting this part is mainly twisted and deformed with each opening / closing operation.
Moreover, it is difficult to say that there is no possibility that a force that pulls one of the two ends of the tube connected to the pipe will be applied during the opening and closing operations. However, even in such a situation, with the structure shown in FIG. 3, at least both ends of the flexible tube cannot come out of the pipe.

A heat resistant tape or the like may be wound instead of the processing 304 provided on the flexible tube 306 shown in FIG. 3B. In the embodiment described in FIG. 3, the flexible tube must be molded,
If a heat-resistant tape or the like is used instead, a mass-produced flexible tube for general-purpose tail can be used, which is economical.

(Other Embodiments) As described above, the electronic apparatus according to the embodiment of the present invention is provided with a system for circulating the liquid in a very narrow space inside the case. The work of connecting a flexible tube having an inner diameter of 2 mm to a pipe having an outer diameter of about 3 mm in such a narrow space lowers the workability at the time of assembly and increases the production cost (particularly the amount of assembly process). In addition, workability during maintenance may be reduced. Therefore, when such a problem occurs, the structure shown in FIG. 7 is effective as a means for avoiding it. This is an effective means for connecting the flexible tube 702 and the pipe 705 in a narrow space. The end surface of the joint or the heat radiating pipe which is previously formed in the pump or the water cooling jacket is processed into the shape shown in FIG. 7 (a). An auxiliary joint 701 having a similar shape is previously connected to the flexible tube 702 by using the band 703 described above. At the time of assembly, using a push screw 704 having a shape shown in FIG. 7B,
Use a pipe 705 with an internal thread to connect them to each other as shown in FIG. 7 (c).
Connect in. At this time, if the gasket 707 is used,
The processing roughness of both end faces can be absorbed. The advantage of such an auxiliary joint and set screw means is that there is no need to turn both when connecting the flexible tube to the pipe. Since it is connected just by turning the set screw, it can be applied even in a narrow space inside this case or display case during assembly. When turning the push screw, a dedicated assembly tool that can be inserted into a narrow space may be prepared and used. Particularly, it is effective for connection in a narrow space where the fingers of the assembling worker cannot enter.

In the embodiments described so far, since the opening / closing operation occurs at the hinge portion between the main body case and the display case, the heat dissipation pipe in the display case and the flow path on the main body case side are connected by the flexible tube.

However, if the rotary type joint shown in FIG. 8 is used, the hinge portion can be connected without using a flexible tube. The rotary joint shown in FIG. 8 is composed of a rotor 801 made of heat-resistant resin and a case 802, and joints 804 and 803 are preformed in each case. In either case, when connecting the heat radiating pipe, the pump, or the water cooling jacket, if the connection is made by, for example, the method shown in FIG.

[0037]

According to the present invention, the heat of the heating element can be radiated from the rear surface of the display case at a necessary and sufficient circulating liquid flow rate, and an electronic device having high reliability at each connection portion can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view of an electronic device including an embodiment of the present invention.

FIG. 2 is an enlarged perspective view of a joint portion between a pump or a water cooling jacket and a flexible tube.

FIG. 3 is an enlarged perspective view of a joint according to the present invention.

FIG. 4 is a block diagram illustrating a cooling principle.

FIG. 5 is a graph illustrating the relationship between the circulation flow rate and the water cooling jacket temperature.

FIG. 6 is a sectional view showing an embodiment of the present invention.

FIG. 7 is a sectional view illustrating a joint structure according to another embodiment of the present invention.

FIG. 8 is a perspective view illustrating a joint structure according to still another embodiment of the present invention.

[Explanation of symbols]

1 ... Main body case, 2 ... Display case, 3 ... Keyboard, 4 ... Wiring board, 5 ... Hard disk, 6 ... Auxiliary storage device, 7 ... CPU, 8 ... Water cooling jacket, 9 ... Radiating pipe, 10 ... Metal radiator plate, 11 … Pumps, 12, 13,
14 ... Flexible tube, 302 ... Band, 303
... auxiliary band, 306 ... flexible tube (with processing), 305 ... holder provided on the case side, 704 ... push screw, 705 ... female screw processed case, 707 ... gasket.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshihiro Kondo             502 Kintatemachi, Tsuchiura City, Ibaraki Japan             Tate Seisakusho Mechanical Research Center (72) Inventor Shigeo Ohashi             502 Kintatemachi, Tsuchiura City, Ibaraki Japan             Tate Seisakusho Mechanical Research Center (72) Inventor Takeshi Nakagawa             810 Shimo-Imaizumi Stock Exchange, Ebina City, Kanagawa Prefecture             Hitachi Platform Platform             Home Office F-term (reference) 3L044 AA04 BA06 CA13 DB01 FA02                       KA01 KA02 KA04                 5E322 AA07                 5F036 AA01 BB08 BB43 BB44

Claims (7)

[Claims] 1. A first housing in which a semiconductor element is mounted, a second housing in which a display device is housed and which is rotatably supported by the first housing, the semiconductor element and a thermal device. A heat receiving member in contact with the second housing, a heat radiating member in thermal contact with the inner surface of the second housing, a liquid driving means for driving a liquid medium between the heat receiving member, the heat receiving member, the heat radiating member, and In an electronic device comprising a flexible tube connecting to a liquid driving means, a flexible tube near the band is covered with a connection portion of the flexible tube connecting the heat receiving member, the heat radiating member and the liquid driving means. Is fixed to a holder provided in the first housing. 2. The electronic device according to claim 1, wherein a circulation flow rate of the liquid medium is 120 μl / sec or more. 3. The electronic device according to claim 1, wherein the circulating flow rate of the liquid medium is 1200 μl / sec or less. 4. The electronic device according to claim 1, wherein the height of the liquid driving means is 30 mm or less. 5. The liquid driving means has a flat shape,
The electronic device according to claim 1, wherein the flat shape is a flat shape in the thickness direction of the first casing. 6. The electronic device according to claim 1, wherein an inner diameter of the flexible tube is larger than an inner diameter of the heat dissipation member. 7. A first housing in which a semiconductor element is mounted, a second housing in which a display device is housed and which is rotatably supported by the first housing, the semiconductor element and a thermal device. A heat receiving member in contact with the second housing, a heat radiating member in thermal contact with the inner surface of the second housing, a liquid driving means for driving a liquid medium between the heat receiving member, the heat receiving member, the heat radiating member, and In an electronic device including a flexible tube that connects with liquid driving means, the flow path direction can be arbitrarily changed at a connection portion of a flexible tube that connects the heat receiving member, the heat dissipation member, and the liquid driving means. An electronic device comprising a joint, the joint being formed of a rigid body.