JPH1197869A - Heat-dissipating device and small electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat-dissipating device, by which heat generated by a heat generating body is dissipated to the outside of an enclosure with a simple configuration and in which a rise in a temperature inside the enclosure and a rise in temperature on the surface of the enclosure are reduced by a method, wherein a first heat conduction member is situated at the inside of the enclosure, a second heat conduction member is installed so as to be situated in a recessed part formed at the outside of the enclosure, and the recessed part at the enclosure is closed by a heat-dissipating cover. SOLUTION: Heat which is generated by a heat-generating body 1 is transmitted to a heat-dissipating case 3 which surrounds the heat generating body 1, and it is transmitted to a heat sink 4 in a thermally coupled state to the heat-dissipating case 3. Then, since the heat sink 4 is situated outside respective enclosure 5a, 5b, heat is dissipated to the open air which is passed and circulated through ventilation holes 6a in a heat dissipating cover 6. Consequently, the heat which is generated by the heat-generating body 1 is diffused much inside the enclosures 5a, 5b, and an inside temperature and a surface temperature will rise greatly. In addition, when a third heat conduction member whose thermal conductivity is large, is interposed between the heat generating body 1 and the heat-dissipating case 3 so as to increase a heat conduction efficiency to the heat-dissipating case 3 from the heat- generating body 1, the temperature rise of the heat generating body 1 can be restrained to be much lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat radiating device for a printed circuit board mounted with an LSI having a high heat generation density or a microcomputer mounted on an electronic device such as a small personal computer, a digital camera or a video camera. Regarding improvement.

[0002]

2. Description of the Related Art The power density of printed wiring boards used in electronic devices, especially small electronic devices, increases due to the progress of high integration and high-density mounting of heat-generating components such as LSIs and microcomputers. Heat is a major problem.

Air-cooling systems are generally used for heat-dissipating devices for small electronic devices. In many cases, heat-dissipation is promoted by bringing a heat sink into close contact with a heating element, or forced air-cooling is provided by providing a blower fan. For example, JP-A-7-20
2085, JP-A-8-261672 and JP-A-8-335656).

[0004]

In such a conventional cooling method, for example, in a heat radiation method in which a heat sink is brought into close contact with a heating element, the surface temperature of an LSI or a microcomputer as a heating element can be lowered. Since the heat is dissipated into the housing of the device, the surface temperature of the housing rises, and a heat sink corresponding to an element such as an LSI or a microcomputer which is a heating element is required, so that there is a problem in cost.

There is also a method of dissipating heat to the outside of the housing by using an air duct. However, since the air duct is formed, the arrangement of the heating elements in the housing is restricted, resulting in an increase in cost.
Although there is a cooling system using a heat pipe, there is a problem that the cost is increased.

Also, the size of the volume occupied by the blower fan in a small electronic device is a problem, and high frequency noise generated by the blower fan is recorded particularly in an electronic device of a type that records sound. There is a problem.

One object of the present invention is to radiate the heat generated by a heating element in a housing of an electronic device to the outside of the housing with a simple configuration to reduce a rise in the temperature in the housing and the temperature on the surface of the housing. It is in.

Another object of the present invention is to prevent electromagnetic waves from being emitted from an internal electronic circuit in an electronic device, and further to prevent noise from being generated by an intruding electromagnetic wave from the outside.

[0009]

According to the present invention, in order to solve such a problem, a heat-generating element such as an LSI or a microcomputer mounted on a printed wiring board is surrounded by a first heat-conducting member to radiate heat into a housing. Is minimized, and the heat of the first heat conducting member is released to the outside of the housing.

More specifically, a first heat conductive member enclosing a printed wiring board on which a heating element is mounted, a second heat conductive member coupled to the first heat conductive member so as to be able to conduct heat, and a heat dissipation cover. The first heat conduction member is located inside the housing, and the second heat conduction member is located so as to be located in a recess formed outside the housing, and the recess of the housing is covered with a heat dissipation cover. The second heat conduction member may be covered by covering.

Alternatively, a first heat conductive member enclosing a printed wiring board on which a heating element is mounted, a heat radiation space partitioned by a partition wall inside the housing and accommodating the first heat conductive member, A ventilation hole formed in the housing is provided so as to circulate through the heat radiation space.

Since the first heat conducting member is made of a material that electromagnetically shields the periphery of the printed wiring board on which the heating element is mounted, emission and intrusion of electromagnetic waves from the electronic circuit are prevented.

Further, by interposing a third heat conducting member for thermally coupling the first heat conducting member and the heating element therebetween, heat transfer efficiency is enhanced, and the third heat conducting member is electrically connected. By using an insulating material, the insulation between the electronic circuit and the first heat conducting member is ensured, and the miniaturization is promoted.

Further, the third heat conducting member is a highly elastic sheet-like member, so that the height difference of the heating element (the size of the gap between the heating member and the first heat conducting member) is reduced by the third heat conducting member. Absorption is performed by elastic deformation of the conductive member.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an exploded perspective view of a small electronic device showing one embodiment of the present invention. FIG. 2 is a cross-sectional view of the small electronic device shown in FIG.

In FIG. 1, reference numeral 1 denotes a heating element which is a circuit element such as an LSI or a microcomputer mounted on a printed wiring board 2;
Is a first enclosing the printed wiring board 1 on which the heating element 1 is mounted.
A heat radiation case 4 as a heat conduction member, a heat sink 5a and 5b as a second heat conduction member mechanically and thermally coupled to the heat radiation case 3, a housing 5 and a heat radiation cover 6 having a ventilation hole 6a.

The heat sink 4 is provided with radiating fins for releasing heat conducted from the radiating case 3 into the air. The housings 5a and 5b are arranged such that the heat sink 4 is
There is provided a concave portion 5c for being located outside of 5b. The heat dissipation cover 6 covers the heat sink 4 by closing the recess 5c.

In such a small electronic device, the heat generated by the heating element 1 is conducted to the heat radiating case 3 surrounding the heat generating element 1 and is conducted to the heat sink 4 which is thermally coupled to the heat radiating case 3. Since the heat sink 4 is located outside the housings 5a and 5b, the heat radiation cover 6
Heat is radiated to the outside air circulating through the ventilation holes 6a. Accordingly, a large amount of heat generated by the heat generating element 1 is not dissipated into the housings 5a and 5b, and the internal temperature and the surface temperature do not greatly increase.

If the efficiency of heat conduction from the heating element 1 to the heat radiation case 3 is increased, the temperature rise of the heating element 1 can be further suppressed. In the embodiment shown in FIG. 3, in order to increase the heat conduction efficiency between the heating element 1 and the heat radiating case 3, the third heat conducting member 7 having a large thermal conductivity is formed between the heat generating element 1 and the heat radiating case 3.
a, 7b. The third heat conducting members 7a and 7b promote heat conduction between the heating element 1 and the heat radiating case 3.

In the embodiment shown in FIG. 1 and FIG. 2, since the heat conduction from the heating element 1 to the heat radiation case 2 is performed through the air layer, it is difficult to obtain high heat conduction efficiency. is there. However, as in this embodiment, the third heat conductive members 7a and 7b having a higher thermal conductivity than the air layer are interposed between the heat generating body 1 and the heat radiating case 3, so that
The effect of heat conduction can be enhanced.

Since the form (height and top shape) and arrangement of a large number of circuit elements mounted on the printed wiring board 2 are various,
A device for arranging the third heat conducting members 7a and 7b so as to securely connect the plurality of heating elements 1 and the heat radiating case 3 is required. Each heating element 1 is formed using a third heat conductive member having a thickness corresponding to the size of the gap between each heating element 1 and the heat radiation case 3.
Although it is conceivable to adopt a structure in which the circuit board and the heat radiating case 3 are individually connected to each other, this embodiment uses a flat sheet-like third heat conducting member 7a, 7b having a high elasticity and a plurality of circuit elements. The height difference of the (heating element 1) was absorbed by elastic deformation.

The third heat conducting members 7a and 7b are made of an electrically insulating material, thereby supporting electric insulation between the heat radiating case 2 and each of the LSIs and the circuit elements of the microcomputer. The gap between the element and the heat radiating case 3 can be narrowed to promote downsizing.

If it is difficult to absorb the height difference (the size of the gap between the heat radiating case 3) of the plurality of heating elements 1 due to the elastic deformation of the third heat conducting members 7a and 7b, as shown in FIG. The third heat transfer members 7a and 7b may be interposed by deforming the heat radiating case 3 to make the gap with the heating element 1 substantially uniform.

Further, the printed wiring board 2 of this small electronic device
And an electronic circuit constituted by the circuit element (heating element 1) mounted on the electronic device and the electronic device is prevented from emitting unnecessary electromagnetic waves or generating noise due to external electromagnetic waves. If desired, the heat radiating case 3 may be made of a material having good thermal conductivity and a material having an electromagnetic shielding effect.

There is no particular limitation on the shape of the heat sink 4, but in order to increase the efficiency of heat dissipation to the outside air, it is preferable to use a finned radiating plate having good space efficiency as in this embodiment.

In order to firmly construct the outer shell of the small electronic device, it is preferable that the number of parts attached to the outside of the housing is small.
FIG. 5 shows an embodiment in which a heat dissipation space is formed in the housing from such a viewpoint.

A radiating space 5e partitioned by a partition wall 5d is formed inside the housing 5a, and the radiating case 3 having a radiating fin 3a formed on the surface thereof is accommodated in the radiating space 5e. A printed wiring board 2 on which a circuit element as a heating element 1 is mounted in a heat radiation case 3 is accommodated in the same manner as in the above-described embodiment.

A ventilation hole 5f is formed in a region corresponding to the heat radiation space in the housing 5a forming a heat radiation space 5e between the partition wall 5d.
And circulates outside air to diffuse heat released from the radiation fins 3a to the outside of the housing.

The printed wiring board 2 in the heat radiating case 3 is connected to a main circuit board 8 in the housings 5a and 5b via a connector 9.

Also in this embodiment, the heat generated by the heat generating element 1 in the heat radiating case 3 can be efficiently radiated out of the housing because it is slightly diffused into the housing.

In a small electronic device, it is important to locate the heat sink 4 in the housings 5a and 5b.
2. Description of the Related Art A portable small electronic device such as a micro video camera or an electronic camera compatible with MPEG is designed to support the device with a left hand and operate with a right hand. The power supply battery is generally arranged at a lower portion in the housing from the viewpoint of weight distribution. It is desirable that the heat sink that dissipates heat is arranged such that the cooling air naturally circulates smoothly and efficiently dissipates the hot air out of the housing. The embodiment shown in FIG. 6 is configured in consideration of such points.

The small electronic device shown in FIG. 6 is an electronic camera compatible with MPEG, and has a concave portion 5g as a place for arranging the heat sink 4 at an upper corner portion of the housings 5a and 5b (upper right corner when viewed from the object side, In the upper left corner when viewed from above). A heat sink 4 connected to a heat radiating case 3 containing a printed wiring board on which a circuit element as a heating element is mounted is disposed in the concave portion 5g at the upper corner, and is covered with a heat radiating cover 6 for protection.
The heat dissipation cover 6 has a ventilation hole 6a formed on each exposed surface to facilitate natural circulation of outside air.

Reference numeral 10 denotes a CCD image sensor lens arranged at the center of the upper part of the housing, and 11 denotes a housing 5
a and a power supply battery arranged below 5b.

[0035]

According to the present invention, the heat of the first heat conducting member surrounding the heating element is efficiently radiated to the outside of the housing to suppress heat diffusion into the inside of the housing. The effect is obtained that the rise of the pressure can be reduced.

Further, by using a material having an electromagnetic shielding effect for the heat radiation case which is the first heat conductive member surrounding the printed wiring board, the electromagnetic wave from the electronic circuit constituted by the LSI or the microcomputer is formed on the printed wiring board. An effect is obtained in that emission and intrusion of electromagnetic waves from outside can be prevented to prevent electromagnetic interference.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a small electronic device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the small electronic device shown in FIG.

FIG. 3 is a cross-sectional view of a small electronic device showing another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a small electronic device showing still another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a small electronic device according to still another embodiment of the present invention.

FIG. 6 is an exploded perspective view of a small electronic device showing still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating element, 2 ... Printed wiring board, 3 ... Heat dissipation case, 4 ...
Heat sink, 5a, 5b ... housing, 6 ... heat dissipation cover, 7
a, 7b: Third heat conducting member.

Claims (9)

[Claims] A first heat conductive member enclosing a printed wiring board on which a heating element is mounted, a second heat conductive member coupled to the first heat conductive member in a heat conductive manner, and a heat dissipation cover; The first heat conductive member is located inside the housing, and the second heat conductive member is installed so as to be located in a recess formed outside the housing, and the recess of the housing is closed with a heat dissipation cover. A heat dissipating device, wherein the heat dissipating device covers the second heat conducting member. A first heat conduction member enclosing the printed wiring board on which the heating element is mounted; a heat radiation space defined by a partition wall inside the housing and accommodating the first heat conduction member; A heat dissipation device comprising a ventilation hole formed in the housing so as to circulate in a heat dissipation space. 3. The heat radiating device according to claim 2, wherein the first heat conducting member has a heat radiating fin on a surface thereof. 4. The heat dissipation device according to claim 1, wherein the first heat conductive member is made of a material that electromagnetically shields a periphery of a printed wiring board on which a heating element is mounted. 5. The heat radiation device according to claim 1, wherein a third heat conductive member for thermally connecting the first heat conductive member and the heating element is interposed therebetween. apparatus. 6. The heat radiating device according to claim 5, wherein said third heat conducting member is made of a material having electrical insulation. 7. The heat radiating device according to claim 5, wherein the third heat conducting member is a sheet-like member having high elasticity. 8. The heat radiating device according to claim 1, wherein said second heat conducting member includes a heat radiating fin. 9. A small electronic device comprising the heat radiating device according to claim 1.