JP2008218618A - Printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board which is excellent in heat radiation characteristics, of light weight, requiring no special cooling component. <P>SOLUTION: Relating to a flexible substrate 7, with a graphite sheet 1 as a base, an insulating layer is provided on both surfaces, and a conductor 2 constituting an electric circuit is formed, which is covered with a protective layer 4. The flexible substrate is integrated with a rigid substrate 8 on both surfaces. With this configuration, the heat generated at the rigid substrate is conveyed to the flexible substrate due to high heat conductivity of the graphite sheet, and then released into the air or a case. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a printed wiring board used in various electronic devices such as a personal computer, a mobile communication telephone, and a video camera.

  In recent years, as electronic devices have higher functionality and higher density, electronic components are becoming increasingly smaller, highly integrated, faster, and multi-pinned.

  Along with this, the temperature environment inside the device tends to deteriorate compared to the conventional case, and it is required to release the heat generated inside the device more efficiently in order to operate the device normally.

  As a printed wiring board corresponding to this, a metal base substrate is known in which a metal plate such as aluminum is used as a core, and a circuit pattern is formed on one or both surfaces of the metal plate via an insulating layer. In addition, when various parts are mounted on a printed wiring board and then installed in an electronic device, a heat sink is attached to the heat generating component to diffuse the heat into the air using a temperature difference, or a cooling fan is used to externally A method of forcibly releasing heat is also widely used.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP-A-10-261847

  However, in the above-described conventional printed wiring board, the use of a metal plate for the core increases the thickness and weight compared to a general printed wiring board. Also, in the method using a heat sink or a cooling fan in an electronic device, the size and weight of the entire electronic device increase due to the space and weight of the heat sink and the cooling fan. Both methods are unsuitable for electronic devices that are required to be small and light, and have the problem of obstructing the reduction in size and thickness of electronic devices.

  The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a lightweight printed wiring board that does not require a dedicated cooling component and has excellent heat dissipation characteristics.

  In order to achieve this object, the printed wiring board of the present invention has a configuration in which a rigid substrate is integrated with a part of a flexible substrate having a circuit formed on at least one side, and the flexible substrate has a graphite layer. It is characterized by.

  With this configuration, the heat generated in the rigid board part is transmitted to the flexible board part through the graphite sheet having high thermal conductivity, and is radiated from the surface to the air or from the tip of the flexible board part to the housing. Has the effect of being able to

  According to the printed wiring board of the present invention, a lightweight printed wiring board excellent in heat dissipation can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a printed wiring board according to Embodiment 1 of the present invention.

  In FIG. 1, the printed wiring board of the present invention includes a graphite sheet 1, a conductor 2, an insulating layer 3, a protective layer 4, a through hole 5, and a solder resist 6.

  An insulating layer 3 is provided on both sides of the graphite sheet 1 as a base, a conductor 2 constituting an electric circuit is formed, a flexible substrate 7 covered with a protective layer 4 thereon, and a rigid substrate 8 on both sides of the flexible substrate 7. The structure is integrated.

The graphite sheet 1 used in the present embodiment has a thermal conductivity of 400 W / mk, which is equivalent to copper or aluminum, and its weight is extremely light at 1.1 g / cm ³ .

  According to this configuration, the heat generated in the rigid substrate 8 is conducted to the flexible substrate 7 due to the characteristics of the graphite sheet 1 having high thermal conductivity, and has a function of radiating heat to the atmosphere or the housing.

  In this embodiment, the rigid substrate 8 is provided on both surfaces of the flexible substrate 7, but this may be provided on one surface.

  In addition, by providing the terminal 11 at the tip of the flexible substrate 7, it is possible to connect to another electric circuit.

(Embodiment 2)
FIG. 2 is a diagram showing a manufacturing process of the printed wiring board manufacturing process according to the second embodiment of the present invention.

  When the prepreg 9 is sandwiched between the flexible substrate 7 and the rigid substrate 8 (FIG. 2 (a)), and is crimped and integrated by a hot press, the configuration shown in FIG. 2 (b) is obtained. Next, a through hole 5 for obtaining an electrical connection is provided in a necessary part (FIG. 2C). Further, the rigid substrate portion including the through hole 5 is plated with a metal to form an electrical connection circuit between the layers (FIG. 2D). Finally, a circuit is formed on the conductor 2 on the surface layer of the rigid substrate 8, and a solder resist 6 is formed thereon.

  The graphite sheet 1 has a heat resistance temperature as high as 400 ° C., and has a feature that it does not change even when the printed wiring board is manufactured and temperature changes during component mounting by soldering.

  With this configuration, it is possible to connect the layers through the through holes 5 and improve the degree of freedom of wiring.

  In this embodiment, the through hole 5 using metal plating is used for the electrical connection between the layers. However, in addition to the plating, a method of realizing the electrical connection by filling the through hole with a conductive material is also possible. good.

  In the present embodiment, the rigid substrate 8 has two layers on one side, but may have three or more layers.

(Embodiment 3)
In FIG. 2 (a), the flexible substrate 7 has a graphite removing portion 10 formed in advance at a predetermined location of the graphite sheet 1 by drilling or punching, and the insulating layer 3 and the conductor 2 are overlapped on both surfaces and thermocompression bonded. It is obtained by forming a circuit and further forming the protective layer 4 on the surface thereof.

  With this configuration, it is possible to prevent a short circuit between the conductive graphite sheet 1 and the through hole 5.

  On the contrary, the graphite sheet 1 can have a shielding effect against electromagnetic waves by electrically connecting the specific through hole 5 and the graphite sheet 1.

  With the printed wiring board of the present invention, it is possible to realize a lightweight printed wiring board with excellent heat dissipation, and it can be used for electronic devices that are required to be small and light, such as personal computers, mobile communication telephones, video cameras, etc. It is valid.

  In addition, since electric energy is not required for heat dissipation, it is useful for improving the operating time of battery-driven electronic devices.

Sectional drawing which shows the printed wiring board in Embodiment 1 of this invention Sectional drawing which shows the manufacturing process of the printed wiring board in Embodiment 2 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Graphite sheet 2 Conductor 3 Insulating layer 4 Protective layer 5 Through hole 6 Solder resist 7 Flexible substrate 8 Rigid substrate 9 Prepreg 10 Graphite removal part 11 Terminal

Claims (3)

A printed wiring board comprising: a rigid substrate integrated with a part of a flexible substrate having a circuit formed on at least one side, wherein the flexible substrate has a graphite layer. The printed wiring board according to claim 1, wherein the rigid board and the flexible board are electrically connected by metal plating applied to the through hole. The printed wiring board according to claim 2, wherein a graphite removing portion larger than the through hole is provided at a place where the through hole of the graphite layer is provided.

Images