JP5765357B2 - Circuit board structure and electronic device - Google Patents

Description

The present invention relates to a circuit board structure in which a plurality of circuit boards each having a component that generates heat are mounted in the thickness direction, and an electronic apparatus including the circuit board structure.

  In portable information devices represented by portable computers and mobile communication devices, in order to process a variety of multimedia information such as characters, sounds, and images, it is required to increase the processing speed of the CPU and to make it multifunctional. In addition, in order to improve portability, the housing for housing the CPU has been miniaturized, and the mounting space inside the housing has become increasingly narrow.

  In portable information devices, a large number of circuit components including a CPU are mounted on both sides of a circuit board housed in a housing at a high density, or a plurality of circuit boards are stacked in the thickness direction to form a unit. It is a single circuit module that can be used to reduce the housing space.

  Recent CPUs used in portable information devices have a greater amount of heat generation due to higher integration and higher performance, so in order to accommodate a CPU with a large amount of heat generation inside the case, the CPU inside the case It is necessary to improve the heat dissipation performance of the CPU, and cooling means dedicated to the CPU such as a heat sink and an electric fan are indispensable.

  However, when a plurality of circuit boards are stacked in the thickness direction to form a single unit, if a CPU with a large amount of heat is interposed between adjacent circuit boards, the circuit board becomes an obstacle and surrounds the CPU. Since it becomes impossible to secure a space for installing the heat sink and the electric fan, the heat sink and the electric fan have to be arranged at a position away from the CPU as a heat source, and the heat dissipation performance of the CPU becomes insufficient.

For this reason, in Patent Document 1, another circuit board adjacent to the circuit component that generates heat can be used as a heat sink for this circuit component, and the heat dissipation of the circuit component can be improved without using any special cooling means. Possible circuit modules have been proposed.
The circuit module includes a plurality of circuit boards on which circuit elements are mounted, the circuit boards are arranged at intervals in the thickness direction, and at least one circuit board generates at least one that generates heat during operation. A TCP (Tape Carrier Package) is provided, and this TCP is interposed between adjacent circuit boards. The TCP that generates heat is thermally connected to another adjacent circuit board via thermally conductive grease, an adhesive, or an elastic sheet.

JP-A-11-112174

For example, when a wireless LAN (Local Area Network) circuit is built in a small device, the wireless LAN circuit itself is also miniaturized, so there is a concentration of heat due to self-heating, and further, from the main circuit for basic operation of the device. There is a risk of receiving heat and exceeding the limit temperature on the wireless LAN circuit side.
On the other hand, it is a problem for the main circuit side to receive heat from the wireless LAN circuit.

  Further, the circuit module of Patent Document 1 has a problem that processing such as a thermal via is required.

  An object of the present invention is to realize a reduction in size and thickness of the circuit board portion and efficient heat dissipation without using a circuit with a special dedicated structure or applying special processing to the circuit board. is there.

In order to solve the above problems, the present invention provides:
A first circuit board on which a first component that generates heat is mounted, a second circuit board on which a second component that generates heat is mounted, and a support that supports the first circuit board and the second circuit board A circuit board structure in which the first circuit board and the second circuit board are stacked in the thickness direction so as to be in contact with each other and supported by the support body. When the heat generation of one component is smaller than the heat generation of the second component, a first heat dissipation path is formed in which the heat generation of the second component is dissipated through the first circuit board and the support. When the heat generation of the first component is larger than the heat generation of the second component, the second heat dissipation path through which the heat generation of the first component is dissipated through the second circuit board and the support body Is formed .

  According to the present invention, it is possible to realize a reduction in size and thickness of the circuit board portion and efficient heat dissipation without using a circuit having a special dedicated structure or performing special processing on the circuit board. it can.

1 illustrates a configuration of an embodiment of an electronic device to which the present invention is applied, and is a front view of a camera. It is the figure which removed the battery cover from the display part housing | casing. It is the figure which saw through the inside of a display part housing | casing. It is a perspective view of a circuit module. FIG. 5 is a view of the circuit module of FIG. 4 as viewed from the back side, with the circuit board hidden. It is the perspective view which mounted | wore the circuit module in the housing | casing. It is a disassembled perspective view of a housing | casing. It is sectional drawing along the arrow YY line | wire of FIG. It is the schematic diagram which showed the heat dissipation path | route when the heat_generation | fever from a wireless LAN circuit board is smaller than the heat_generation | fever from a main circuit board by the arrow. It is the schematic diagram which showed the heat dissipation path | route when the heat_generation | fever from a wireless LAN circuit board is larger than the heat_generation | fever from a main circuit board by the arrow. It is the schematic which simulated the thermal analysis of 10-minute progress by FHD moving image photography by wireless LAN: off. It is the schematic diagram which simulated the thermal analysis of 10-minute progress by wireless LAN: on and VGA moving image photography.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

"The key point"
Laminate circuit boards that are not compatible with each other, suppress heat generation of either one, and use a member that generates less heat for heat dissipation.

"effect"
Heat generation can be suppressed and heat can be efficiently dissipated, and both miniaturization and wireless LAN sensitivity can be achieved.

(Embodiment)
FIG. 1 shows a digital camera (hereinafter simply referred to as a camera) 1 as a configuration of an embodiment of an electronic apparatus to which the present invention is applied. 2 is a display unit housing, 3 is a lens unit housing, and 4 is a frame. Reference numeral 5 denotes a battery lid.

  As illustrated, the camera 1 includes a display unit housing 2, a lens unit housing 3, and a frame 4. The display unit housing 2 includes a detachable battery cover 5 on one side, and a display unit (not shown) on the other side.

  FIG. 2 shows a state in which the battery cover 5 is removed from the display unit housing 2, and 6 is a battery.

  As illustrated, when the battery cover 5 is removed, the resin case 2A and the battery 6 of the display housing 2 are exposed.

  FIG. 3 shows a state where the inside of the display unit housing 2 is seen through, and 10 is a wireless LAN circuit module.

  As shown in the figure, the wireless LAN circuit module 10 is attached to the magnesium chassis 2B of the display unit housing 2 by screwing.

  FIG. 4 shows the wireless LAN circuit module 10, where 11 is a wireless LAN circuit board, 12 is a chip antenna, 13 is a holder, and 14 is a frame.

  As illustrated, a chip antenna 12 is mounted on the end of the wireless LAN circuit board 11. The wireless LAN circuit board 11 is held and positioned by a resin holder 13 inside a resin case 2A so as not to block radio waves, and is bonded or fixed to a high-conductivity aluminum frame 14 or double-sided tape. Yes.

  Various electronic components other than the chip antenna 12 are mounted on the wireless LAN circuit board 11 to form a wireless LAN circuit. When the chip antenna 12 and various electronic components constituting the wireless LAN circuit are driven with a high load, the amount of heat generation becomes large.

The aluminum frame 14 is formed with a notch window 14a that is separated from each other by dimensions d1 to d4 so as to surround the periphery of the chip antenna 12 so as not to block radio waves.
Here, the vertical and horizontal dimensions d1 to d4 surrounding the periphery of the chip antenna 12 are determined based on the sensitivity simulation with the actual machine and the actual machine measurement in consideration of the relationship with the heat radiation described later, but about 10 mm is necessary.

  The frame 14 has an area sufficient to dissipate heat from the electronic components mounted on the wireless LAN circuit board 11 and fixes the wireless LAN circuit board 11 on the main circuit board 21 (see FIG. 7). Therefore, it is formed in a necessary shape.

  FIG. 5 shows the wireless LAN circuit module 10 as viewed from the back side. The wireless LAN circuit board 11 is not shown, 15 is a heat conductive sheet, 16 is a copper foil tape, and 17 is a copper foil fixing tape.

  On the back surface of the wireless LAN circuit board 11, as shown in the figure, a heat conductive sheet 15 is stuck and is in close contact with the electronic circuit chip 22 on the main circuit board 21. Further, a copper foil tape 16 for reinforcing GND is connected to the wireless LAN circuit board 11 and the frame 14 by a copper foil fixing tape 17.

  FIG. 6 shows a state in which the wireless LAN circuit module 10 is mounted in the chassis 2B of the display unit housing 2, and reference numeral 23 denotes a connection FPC.

  As shown in the figure, a connection FPC 23 that electrically connects the wireless LAN circuit board 11 and the main circuit board 21 is provided.

  FIG. 7 is an exploded perspective view of the display unit housing 2, and 24 and 25 are double-sided tapes for fixing FPCs.

  As shown in the figure, two double-sided FPC fixing tapes 24 and 25 are affixed to the frame 14 of the wireless LAN circuit module 10, and the connection FPC 23 is affixed on the FPC fixing double-sided tapes 24 and 25. It is done.

  It is desirable that the electronic circuit chip 22 does not generate much heat, has a high guaranteed temperature, and has a flat and large surface, like a NAND-FLASH memory.

  FIG. 8 shows a cross section taken along the line YY in FIG. 1. 2C is a display unit (LCD that also serves as a touch panel), 26 and 27 are electronic circuit chips, and 28 is a heat conductive sheet.

  As shown in the figure, on the main circuit board 21, two electronic circuit chips 26 and 27 are mounted on the back side of the electronic circuit chip 22.

Here, the main circuit board 21 is mounted with many components that generate relatively high heat, such as a power supply IC, a CPU, and a DDR.
In this embodiment, a NAND-FLASH memory 22 that generates a small amount of heat even when driven at a high load is disposed on the main circuit board 21, and two DDR3 26 and 27 are disposed on the back side of the NAND-FLASH memory 22. ing.

The DDR3 26/27 is driven with a high load and generates a large amount of heat.
These DDR3 26 and 27 are in close contact with a chassis 2B through a heat conductive sheet 28, which has a high thermal conductivity such as magnesium, a high heat capacity, and a rigidity required as a chassis. Accordingly, the heat generated by the DDR3 26 and 27 is radiated to the chassis 2B through the heat conductive sheet 28.

In the camera 1 described above, when the CPU or DDR of the main circuit board 21 such as FHD (Full HD) moving image shooting is operated with a high load, the wireless LAN is stopped because it requires a large amount of power and generates heat. Keep it. After moving image shooting is completed, the wireless LAN may be turned on to transfer data.
In this case, the movement of heat is as shown by arrows in FIG.

  That is, FIG. 9 shows a heat dissipation path when the heat generation from the wireless LAN circuit board 11 is smaller than the heat generation from the main circuit board 21, and the heat generation of the DDR3 26/27 driven by a high load is indicated by an arrow. As described above, the main circuit board 21 is transmitted to the wireless LAN circuit board 11 through the upper NAND-FLASH memory 22 and the heat conductive sheet 15, and is radiated from the battery lid 5 to the outside air via the air above the main circuit board 21.

  Also, as indicated by the arrows, heat is radiated from the wireless LAN circuit board 11 to the chassis 2B via the holder 13 and the frame 14.

  The heat generated by the DDR3 26 and 27 is radiated to the chassis 2B through the lower heat conductive sheet 28 as shown by the arrows.

On the other hand, when the wireless LAN circuit of the wireless LAN circuit board 11 is operated simultaneously with the photographing, it is preferable to limit the operation to a light operation such as VGA moving image photographing.
In this case, the heat generation of the wireless LAN circuit board 11 is greater than that of the main circuit board 21, resulting in heat transfer as indicated by arrows in FIG. 10.

  That is, FIG. 10 shows a heat dissipation path when the heat generation from the wireless LAN circuit board 11 is larger than the heat generation from the main circuit board 21, and the heat generation of the wireless LAN circuit driven at a high load is indicated by an arrow. Then, the heat is dissipated from the wireless LAN circuit board 11 to the chassis 2B through the heat conduction sheet 15, the NAND-FLASH memory 22, the main circuit board 21, DDR3 26 and 27, and the heat conduction sheet 28.

  Also, as indicated by the arrows, heat is radiated from the wireless LAN circuit board 11 to the chassis 2B via the holder 13 and the frame 14.

  Then, the heat generated in the wireless LAN circuit is radiated from the battery lid 5 to the outside air via the air above it, as indicated by an arrow.

  Table 1, FIG. 11 and FIG. 12 show examples in which the above heat generation and heat transfer are simulated.

  As described above, in the wireless LAN circuit board 11 and the main circuit board 21 that are stacked, the operation is reversed, the heat generation of either one is suppressed, and the member with less heat generation is also used for heat dissipation.

  As described above, according to the circuit board structure of the embodiment, the electronic circuit chip 12 and the electronic circuit chips 22, 26, and 27 that are not necessarily driven at the same time when the camera 1 is electrically functioned are mounted. Since the wireless LAN circuit board 11 and the main circuit board 21 are stacked in the thickness direction and are connected to each other by the heat conductive sheets 15 and 28, a special dedicated circuit is used or special processing is applied to the circuit board. Without application, the circuit board portion can be reduced in size and thickness, and efficient heat dissipation can be realized.

(Modification)
In the above embodiment, the camera is used. However, the present invention is not limited to this, and may be another electronic device such as a mobile phone including the camera.
Furthermore, the present invention is not limited to a wireless LAN, and can be used for devices that emit radio waves such as bluetooth and 3G, and electronic devices that have two completely different circuits.
In place of the NAND-FLASH memory of the embodiment, another memory chip may be used.

In the embodiment, the wireless LAN is stopped when the main circuit is driven with a high load, but the wireless LAN may be driven with a low load.
As an additional function, in addition to the above-described wireless LAN, bluetooth, and 3G, a communication function with the outside, such as GPS and TV, may be used.
Further, in addition to the communication function, an image editing function such as changing the color and brightness of the display image, or cutting and pasting the image may be used.

In the embodiment, two circuit boards are stacked, but three or more circuit boards may be stacked and connected to each other by a heat conductor.
Further, the type, material, shape and the like of the substrate, chip, and heat conductor are arbitrary, and it is needless to say that other specific detailed structures can be appropriately changed.

As mentioned above, although several embodiment of this invention was described, the scope of the present invention is not limited to the above-mentioned embodiment, The range of the invention described in the claim, and its equivalent range Including.
The invention described in the scope of claims attached to the application of this application will be added below.
The item numbers of the claims described in the appendix are as set forth in the claims attached to the application of this application.
[Appendix]
<Claim 1>
A plurality of circuit boards, each mounted with electronic circuit chips that do not necessarily have to be driven at a high load at the same time when the device functions electrically, are stacked in the thickness direction and connected to each other by a heat conductor. Circuit board structure characterized by
<Claim 2>
2. The circuit board structure according to claim 1, wherein when the electronic circuit chip on one circuit board is driven at a high load, the electronic circuit chip on the other circuit board is stopped or driven at a low load. .
<Claim 3>
The one circuit board is mounted with an electronic circuit chip for realizing the basic function of the device,
3. The circuit board structure according to claim 2, wherein an electronic circuit chip for realizing an additional function of the device is mounted on the other circuit board.
<Claim 4>
The apparatus is a digital camera,
The basic function is a shooting function,
4. The circuit board structure according to claim 3, wherein the additional function is an external communication function.
<Claim 5>
The apparatus is a digital camera,
The basic function is a shooting function,
4. The circuit board structure according to claim 3, wherein the additional function is an image editing function.
<Claim 6>
The back surface of the other circuit board and the memory chip on the one circuit board are attached to each other with the heat conductive sheet. Circuit board structure.
<Claim 7>
An electronic apparatus comprising the circuit board structure according to any one of claims 1 to 6 accommodated in a housing.

1 Digital camera (electronic equipment)
2 Display unit housing 2A Case 2B Chassis 2C Display unit 3 Lens unit housing 4 Frame 5 Battery cover 6 Battery 10 Circuit module 11 Circuit board 12 Electronic circuit chip 13 Holder 14 Frame 14a Cutout window 15 Thermal conduction sheet (thermal conductor )
16 Copper foil tape 17 Copper foil fixing tape 21 Circuit board 22 Electronic circuit chip 23 Connection FPC
24 Double-sided tape for fixing FPC 25 Double-sided tape for fixing FPC 26 Electronic circuit chip 27 Electronic circuit chip 28 Thermal conductive sheet (thermal conductor)

Claims (5)

A first circuit board mounted with a first component that generates heat;
A second circuit board on which a second component that generates heat is mounted;
A support for supporting the first circuit board and the second circuit board,
A circuit board structure in which the first circuit board and the second circuit board are stacked in the thickness direction so as to be in contact with each other and supported by the support,
When the heat generation of the first component is smaller than the heat generation of the second component, there is a first heat dissipation path through which the heat generation of the second component is radiated through the first circuit board and the support. Formed,
When the heat generation of the first component is larger than the heat generation of the second component, there is a second heat dissipation path through which the heat generation of the first component is radiated through the second circuit board and the support. A circuit board structure characterized by being formed . The surface of the first circuit board on which the first component is not mounted is the second circuit board side, and the surface of the second circuit board on which the second component is not mounted is the first circuit board. The first circuit board and the second circuit board are stacked in the thickness direction so as to be in contact with each other so as to be on the side of the circuit board, and are supported by the support body. 2. The circuit board structure according to 1. The second circuit board has a third component mounted on a surface opposite to the surface on which the second component is mounted;
In the first heat dissipation path, the heat generated by the second component is radiated through the third component, the first circuit board, and the support,
In the second heat dissipation path, the heat generated by the first component is radiated through the third component, the second circuit board, the second component, and the support.
The circuit board structure according to claim 2. The first circuit board and the third component are in contact via a first thermal conductor, the second component and the support are in contact via a second thermal conductor;
In the first heat dissipation path, the heat generated by the second component is dissipated through the third component, the first thermal conductor, the first circuit board, and the support.
In the second heat dissipation path, the heat generated by the first component is generated when the third component, the first heat conductor, the second circuit board, the second component, the second heat conductor, Heat is dissipated through the support,
The circuit board structure according to claim 3. An electronic apparatus, comprising accommodating the circuit substrate as claimed in housing claims 1 to any one of 4.