JP4525460B2 - Mobile device - Google Patents

Description

  The present invention relates to heat dissipation of an electronic element, and more particularly to a mobile device that dissipates heat from an electronic element such as a semiconductor mounted on a circuit board using a graphite material having good thermal conductivity.

  In the second generation, for example, the NTT-DoCoMo (trademark registered) PDC (Personal Digital Cellular) method, which is a conventional mobile phone, there is no mounting of high heat generating parts, and the structure of the mobile phone is lightweight, high strength, Thermoplastic structures such as ABS (Acrylonitrile Butadiene Styrene) and PC + ABS (Polycarbonate + Acrylonitrile Butadiene Styrene), which emphasizes manufacturability, are often used, and the internal chassis has heat conduction such as Mg alloy (Magnesium alloy). A good metal chassis was used in part, but it was not a structure specifically designed for heat dissipation.

  However, when moving to the third or fourth generation, high-speed and large-volume data communication such as TV video communication and terrestrial digital broadcasting will be processed continuously, and components that generate a large amount of heat will be installed due to the heavy circuit load. Has come to do. For this reason, it has become necessary to devise heat dissipation, but if the heat dissipation is not performed properly, thermal runaway of the electric circuit becomes a problem.

  On the other hand, mobile phones are continuously required to be lighter, smaller, and thinner, and heat dissipation is a technical issue. In particular, since a mobile phone is used by a human hand and touching the ears or cheeks, the allowable temperature is estimated to rise within 5 to 10 ° C. from the ambient temperature.

  There have been many proposals of heat dissipation in consideration of mobile devices such as mobile phones, PHS (Personal Handyphone System), PDA (Personal Digital Assistance). For example, heat dissipation of heat-generating parts is made by utilizing the light weight and high thermal conductivity of graphite. By making a composite of graphite sheet and metal sheet, insulation coating is applied and unnecessary electrical contact is made. There has been a proposal to perform heat dissipation while preventing the trouble caused by (Patent Document 1).

Graphite has a specific gravity of 1.0 and a thermal conductivity of 800 W / m · K, approximately twice that of typical heat dissipation material Cu (specific gravity 8.9), about 4 times that of Al alloy (specific gravity 2.7), Mg It has a thermal conductivity approximately 150 times that of an alloy (specific gravity 1.8). Further, the graphite sheet can be processed into a sheet of about 0.1 mm, is a flexible material that does not break even when bent, and has high heat resistance, so that it can be integrally formed with a resin. Furthermore, it is a material that does not contain harmful substances.
Japanese Patent Laid-Open No. 2004-23066

  As described above, heat dissipation treatment is a major technical issue. In particular, mobile devices are required to be lightweight, small, and thin for their intended use, and heat generated locally within these restrictions is diffused to the substrate, chassis, chassis, etc. via a heat conduction path with low thermal resistance. However, it is necessary to devise a technique for uniformly and uniformly dissipating heat into the air.

  The method proposed in Patent Document 1 uses the flexibility and thermal conductivity of graphite to radiate heat and can be applied to devices with relatively high density mounting. Mobile devices that process data are required to have a structure that can be further reduced in size and thickness.

  The present invention provides a mobile device that can be mounted at a higher density while utilizing the excellent lightness, heat resistance, and thermal conductivity of graphite by a method different from Patent Document 1.

The mobile device of the present invention is configured as follows.
(1) 1st invention 1st invention is the mobile device which arrange | positioned the circuit board in contact with the resin chassis which insert-molded the graphite sheet on the single side | surface or both surfaces.

  The resin chassis is obtained by insert-molding a graphite sheet with a thermoplastic resin, and at least one surface is a graphite surface. That is, it is a resin chassis having a thermoplastic resin surface and a graphite surface, or a resin chassis having a thermoplastic resin at the center and both surfaces being graphite surfaces. The circuit board is a board having a component surface on which a component that generates heat is mounted and a solder surface on the other surface. The insulating sheet is a sheet having electrical insulation.

  The mobile device uses the resin chassis, circuit board, and insulation sheet described above, and places the insulation sheet on the graphite surface of the resin chassis, and places the solder surface of the circuit board on the insulation sheet. This is the structure.

According to the first invention, the heat generated from the heat generating component is transmitted to the resin chassis integrated with the graphite sheet via the circuit board and the insulating sheet, so that the heat can be diffused.
(2) Second invention The second invention is a mobile device in which a graphite sheet has a sandwich structure on the solder surface of a circuit board.

  The circuit board is composed of a component surface on which a component that generates heat and the other surface are composed of a solder surface, and has one or more through holes at predetermined locations, and the insulation sea has electrical insulation. A through hole is provided at a position corresponding to the circuit board, and the graphite sheet is also provided with a through hole at a position corresponding to the circuit board.

  The mobile device uses the circuit board, insulating sheet, and graphite sheet described above, and both sides of the graphite sheet are sandwiched between the insulating sheets, and further sandwiched by the solder surface of the circuit board from the outside of the sandwiched insulating sheet. It is a structure that is joined to the housing by a metal screw passed through the hole. That is, the insulating sheet is centered on the graphite sheet, and the circuit board having the solder surface in contact with the insulating sheet is disposed on both sides, and is joined to the casing with metal screws through these.

  According to the second invention, heat generated from the heat generating component is transmitted to the graphite sheet via the circuit board and the insulating sheet, and further transmitted to the casing via the metal screw, so that the heat can be diffused.

  According to the first invention, the heat generated from the heat-generating component is transmitted to the resin chassis to achieve heat diffusion, and the resin chassis in which the graphite sheet is insert-molded is light in weight but needs to be light, small and thin. Mobile devices can be provided.

  According to the second invention, it is possible to provide a mobile device that does not require a chassis because graphite having good thermal conductivity is sandwiched between the solder surfaces of the circuit board.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a diagram for explaining an embodiment of the first invention. FIG. 1 (a) shows a cross section of a mobile device so that the entire arrangement can be understood. That is, the outermost shell is the housing 60, the resin chassis 15 is disposed at a substantially central position, and the circuit board 40 on which the heat generating component 50 is mounted is disposed on the resin chassis 15. In this figure, the circuit board 40 is also arranged on the lower surface of the resin chassis 15.

  FIG. 1B is an enlarged view of the vicinity of the heat generating component 50. The resin chassis 15 in FIG. 1A is obtained by insert-molding the graphite sheet 20 with the thermoplastic resin 10, and the surface thereof is the graphite sheet 20. Is exposed. The insulating sheet 30 is disposed thereon, and the circuit board 40 is disposed on the insulating sheet 30 with the solder surface facing down. The insulating sheet 30 is inserted for the purpose of preventing the graphite sheet 20 from being in contact with the solder surface of the circuit board 40 because the graphite sheet 20 is an electrical conductor. The heat from the heat generating component 50 is conducted and diffused through the circuit board 40, the insulating sheet 30, and the resin chassis 15 through the joint with the circuit board 40. Further, the resin chassis 15 is also joined to the housing, and is thermally conducted also to the housing.

  FIG. 2 is a diagram for explaining an embodiment of the invention of a mobile device formed of a thermoplastic resin centering on a graphite sheet, and FIG. 2A shows a cross-section of the mobile device so that the entire arrangement can be understood. is there. That is, the outermost shell is the casing 60, the resin chassis 16 is disposed at a substantially central position, and the circuit board 40 on which the heat generating component 50 is mounted is disposed thereon. In this figure, the circuit board 40 is also arranged on the lower surface of the resin chassis 16.

  FIG. 2B is an enlarged view of the vicinity of the heat generating component 50, and the resin chassis 16 of FIG. 2A is obtained by insert-molding a graphite sheet 20 at the center of the thermoplastic resin 10, A portion of the thermoplastic resin 10 is opened to expose the graphite sheet 20 (the resin chassis 16 has a structure in which the graphite sheet 20 of the first invention and the thermoplastic resin 10 are replaced). The window opening portion 11 of the resin chassis 16 is opened at a position where the upper portion of the heat generating component 50 is in contact with the dimension of the heat generating component 50, and is in contact with the portion where the upper portion of the heat generating component 50 is opened and the graphite sheet 20 is exposed. It is arranged. The heat from the heat generating component 50 is directly conducted to the resin chassis 16 and thermally diffused. Further, the resin chassis 16 is also joined to the housing, and is thermally conducted also to the housing.

  FIG. 3 is a diagram for explaining an embodiment of the second invention. The outermost shell is a casing 60, an insulating sheet 30 is disposed on the graphite sheet 20 at a substantially central position, and is insulated from the solder surface thereon. The circuit board 40 is arranged so that the sheet 30 is in contact therewith. In FIG. 3, the graphite sheet 20 is also arranged in the same configuration on the lower surface of the graphite sheet 20, and the graphite sheet 20 is sandwiched between circuit boards. The graphite sheet 20, the insulating sheet 30, and the circuit board 40 are provided with through holes at the same position, and one of the ribs provided on the casing divided vertically so as to correspond to this position (the upper rib in FIG. 3). ) Is a through hole, and the other (lower rib in FIG. 3) is provided with a screw hole. The graphite sheet 20, the insulating sheet 30, and the circuit board 40 are sandwiched between the ribs and fixed with screws 70 (assuming that there is a similar structure not shown on the left side of FIG. 3). The insulating sheet 30 is inserted for the purpose of preventing contact with the solder surface of the circuit board 30 because the graphite sheet 20 is an electrical conductor as in the first invention.

  Heat generated from the heat generating component 50 is conducted to the circuit board 40, the insulating sheet 30, and the graphite sheet 20 through the joint portion with the circuit board 40, and further conducted through the screw 70 to be thermally diffused in the housing 60.

  FIG. 4 is a diagram for explaining an embodiment of a mobile device in which the inside of the housing has a graphite surface. The inside of the housing 60 in which the heat radiating holes 80 are formed (the lower portion of the housing 60 is the inside in FIG. 4). The insert molded graphite sheet 20 is exposed (the casing 60 is formed by inserting the graphite sheet 20 with a thermoplastic resin). On the upper part of the heat generating component 50 on the circuit board 40, a graphite sheet piece 21 matching the size of the heat generating component 50 is placed, and a heat conductive sheet 90 is further disposed on the graphite sheet piece 21 so as to be in contact with the graphite sheet 20 of the housing 60. The graphite sheet piece 21 may not be provided, and the heat conductive sheet 90 may be directly disposed on the heat generating component 50. The heat conductive sheet 90 is rich in elasticity, and the circuit board 40 and the housing 60 are fixed so as to be in close contact with the graphite sheet 20 of the housing 60. The heat conductive sheet 90 may be a metal sponge in which metal thin wires are entangled.

  The heat generated in the heat generating component 50 is conducted through the graphite sheet piece 21 and the heat conductive sheet 90 to be transmitted to the housing, where it is dissipated.

  FIG. 5 is a diagram for explaining an embodiment of a mobile device using a heat transfer plate to which a graphite sheet is bonded. A heat generating component in which a graphite sheet surface of a heat transfer plate 100 in which a graphite sheet is attached to a metal plate is mounted on a circuit board 40. The heat transfer plate 100 is inserted into a slit 61 formed in the housing 60 and fixed. The metal plate is formed of a spring material such as phosphor bronze so as to press the upper part of the heat generating component 50 as shown in FIG. Thereby, the upper part of the heat generating component 50 and the graphite sheet surface of the heat transfer plate 100 are in close contact with each other, and the heat generated in the heat generating component 50 is transmitted through the heat transfer plate 100 to the housing 60 and is dissipated.

  FIG. 6 is a view for explaining an example of a heat dissipation structure using a graphite heat dissipation box, in which a heat dissipation component 50 mounted on a circuit board 40 is covered with a graphite heat dissipation box 110 made of graphite. A heat conductive sheet 90 is disposed on the heat generating component 50, and the heat conductive sheet 90 and the graphite heat dissipation box 110 are in close contact with each other. The opening of the graphite heat dissipation box 110 is formed in a bellows structure and can be expanded and contracted in the vertical direction of FIG. 6 and is fixed so that the heat conductive sheet 90 on the heat generating component 50 is in close contact. Further, the end of the opening is metallized such as nickel plating, and is soldered to the ground terminal 120 of the circuit board 40. Since graphite has conductivity, the structure shown in FIG. 6 enables electromagnetic shielding to be performed together with heat dissipation. Further, in the embodiment of FIG. 6, a heat radiating hole 80 is provided in the housing 60, and a dust proof filter 130 for preventing dust from being attached to the heat radiating hole 80 is attached.

The following additional notes are disclosed with respect to the above embodiments.
(Appendix 1)
A resin chassis in which a graphite sheet to be inserted is arranged so that at least one surface thereof is a graphite surface and a thermoplastic resin is molded;
A circuit board in which a component surface on which a component that generates heat is mounted and a solder surface on the other surface;
An insulating sheet having electrical insulation;
The mobile device, wherein the insulating sheet is disposed on a graphite surface of the resin chassis, and further, the solder surface of the circuit board is in contact with the insulating sheet.
(Appendix 2)
A resin chassis in which a graphite sheet to be inserted is arranged at the center, and a thermoplastic resin is molded by opening a predetermined portion so that the graphite sheet is exposed,
A circuit board in which a component surface on which a component that generates heat is mounted and a solder surface on the other surface;
The mobile device, wherein the circuit board is disposed in contact with an upper surface of the heat-generating component on a graphite sheet exposed by opening a window of the resin chassis.
(Appendix 3)
A circuit board having a component surface on which a component that generates heat and the other surface are composed of a solder surface, and having one or more through holes at a predetermined location;
An insulating sheet having electrical insulation and having a through hole corresponding to the predetermined location;
A graphite sheet having a through hole corresponding to the predetermined location;
The graphite sheet is disposed by sandwiching both sides of the insulating sheet, further sandwiched by the solder surface of the circuit board from the outside of the sandwiched insulating sheet, and joined to the casing by metal screws passed through the through holes. Mobile devices.
(Appendix 4)
A resin casing in which a graphite sheet to be inserted is disposed so that the inside of the casing becomes a graphite surface and a thermoplastic resin is molded;
A circuit board with components that generate heat;
A heat conductive sheet that is rich in elasticity and has thermal conductivity;
The mobile device, wherein the heat conductive sheet is disposed on an upper surface of the component that generates heat, and the heat conductive sheet is disposed in contact with the graphite surface of the resin casing.
(Appendix 5)
A heat transfer plate having a graphite sheet bonded to one surface of an elastic metal plate;
A circuit board with components that generate heat;
A mobile device, wherein an upper surface of the heat generating component is disposed in contact with a graphite sheet of the heat transfer plate, and an end portion of the heat transfer plate is bonded to a resin casing by a predetermined bonding method.
(Appendix 6)
The mobile device according to appendix 4, wherein the heat conductive sheet is a metal sponge entangled with metal thin wires.
(Appendix 7)
The material is graphite, and the side wall of the opening surface has a predetermined depth and a heat dissipation box with a bellows structure,
A circuit board with components that generate heat;
A heat conductive sheet that is rich in elasticity and has thermal conductivity;
The heat transfer sheet is disposed on the upper surface of the component, and the heat transfer sheet is placed so that the heat transfer sheet is in contact with the bottom surface of the heat dissipation box with the surface that opens the heat dissipation box facing downward, and the heat dissipation box and the circuit board are predetermined. A mobile device characterized by being electrically connected by the method described above.

1 is a mobile device according to a first invention; This is a mobile device in which a graphite sheet is molded into a thermoplastic resin. It is the mobile device of the second invention. It is a mobile device that has a graphite surface inside the housing. It is a mobile device using a heat transfer plate with a graphite sheet bonded. This is a mobile device using a graphite heat dissipation box.

DESCRIPTION OF SYMBOLS 10 Thermoplastic resin 11 Window opening part 15 Resin chassis 16 Resin chassis 20 Graphite sheet 30 Insulation sheet 40 Circuit board 50 Heating component 60 Case 61 Slit 70 Screw 80 Heat radiation hole 90 Heat conduction sheet 100 Heat conduction plate 110 Graphite heat radiation box 120 Earth Terminal 130 Dustproof filter

Claims (2)

A resin chassis in which a graphite sheet to be inserted is arranged so that at least one surface thereof is a graphite surface and a thermoplastic resin is molded;
A circuit board in which a component surface on which a component that generates heat is mounted and a solder surface on the other surface;
An insulating sheet having electrical insulation;
The mobile device , wherein the insulating sheet is disposed on a graphite surface of the resin chassis, and further, the solder surface of the circuit board is in contact with the insulating sheet. The component surface on which the component that generates heat and the other surface are composed of the solder surface,
A circuit board having a through hole;
An insulating sheet having electrical insulation and having a through hole corresponding to the predetermined location;
A graphite sheet having a through hole corresponding to the predetermined location;
The both sides of the graphite sheet are sandwiched between the insulating sheets, and the insulating sheet is further sandwiched.
Sandwiched by the solder surface of the circuit board from the outside of the circuit board, and the housing by a metal screw passed through the through hole
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A mobile device characterized by that.