JP2008085021A - Electronic circuit and its manufacturing method, and mobile terminal with electronic circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively suppress an electromagnetic wave noise without blocking its light weight and without raising its cost. <P>SOLUTION: A flexible printed wiring board 1 includes a ground layer 4 exposing outside on the back side corresponding to the surface side with an electronic component 2 mounted. A conductor-made reinforced board 10 has an opening 11 and adhered to the backside of the electronic component mounted surface of the flexible printed wiring board 1. A conductor-made cushion material 30 is arranged so as to be sandwiched between the exposed ground layer 4 and conductor-made reinforced board 10 of the flexible wiring board 1 and a ground layer 21 of a main wiring board 20 to ground the exposed ground layer 4 and the conductor-made reincorced board 10 of the flexible printed wiring board 1 to the ground layer 21 of the main wiring board 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic circuit having a flexible printed wiring board on which circuit components are mounted, a method for manufacturing the electronic circuit, and a portable terminal including the electronic circuit.

  2. Description of the Related Art Conventionally, mobile terminals that are required to be small and light, such as mobile phone terminals, have often used flexible printed wiring boards that are advantageous in reducing thickness and weight compared to rigid circuit boards. Moreover, the flexible printed wiring board in a portable terminal is used not only for routing a wiring pattern but also for mounting an electronic component such as an IC chip.

  On the other hand, in mobile terminals that have become multifunctional and downsized, such as mobile phone terminals, noise such as unwanted radiation and interference waves generated from various internal electronic components can cause other electronic components and signals. It often has an adverse effect. For this reason, conventionally, in mobile terminals, noise countermeasures have been taken such that shield members for blocking electromagnetic waves are arranged in various places.

  Here, as a noise countermeasure especially for flexible printed wiring boards, noise resistance is conventionally achieved by forming a ground (GND) pattern on one or both sides of the wiring portion of the flexible printed wiring board to shield unwanted radiation and interference waves. Techniques that improve the performance are known. In addition, there is also known a technique in which noise resistance is improved by making a reinforcing plate made of metal on the back side of the component mounting portion on one side of the flexible printed wiring board.

  In Japanese Patent Laid-Open No. 7-1554038 (Patent Document 1), a reinforcing plate for maintaining the flatness of a component mounting portion of a flexible printed circuit board is made of metal, and a conductor portion of the flexible printed circuit board and metal By fixing the reinforcing plate to the housing seat via a metal screw, the metal reinforcing plate is grounded to the housing ground without using a connector or lead wires, and the reinforcing plate is A flexible printed circuit board that realizes a noise suppression measure by using it as a shield plate, a manufacturing method thereof, and a small electronic device using the circuit board are disclosed.

Japanese Patent Laid-Open No. 7-1554038 (FIG. 7)

  As described above, when the reinforcing plate is made of metal, the distance between the ground of the flexible printed wiring board and the metal reinforcing plate becomes very close, and further, the metal reinforcing plate is made of metal. If it is grounded to the housing with screws or the like, a somewhat higher shielding effect can be obtained.

  However, it is not preferable to use a metal screw having a certain weight in a portable terminal such as a cellular phone terminal that is required to be lightweight. Also, when fixing a flexible wiring board together with a reinforcing plate with screws, a screw arrangement design that avoids wiring patterns on the flexible printed wiring board and electronic components to be mounted, or conversely, avoiding screws. Wiring pattern design and electronic component mounting design are required, leading to a reduction in design freedom and an increase in design cost. Also, the reinforcing plate must be provided with a part for allowing the screw to pass through. Therefore, the reinforcing plate in this case is considerably larger than the electronic component mounting portion on the flexible printed wiring board (that is, the reinforcing plate). You will have to make the board bigger than necessary. Further, in the case of using screws, not only a seat portion for screwing is required on the housing side, but also a step for screwing is added at the time of manufacturing, which causes an increase in cost. Thus, noise countermeasures such as fixing the metal reinforcing plate with screws are disadvantageous for reducing the weight of the mobile terminal and also disadvantageous in terms of cost.

  The present invention has been proposed in view of such circumstances, and effectively suppresses noise generated by unnecessary radiation, interference waves, and the like without impeding weight reduction and increasing costs. It is an object of the present invention to provide an electronic circuit, a method for manufacturing the same, and a portable terminal including the electronic circuit.

  In the electronic circuit of the present invention, a flexible printed wiring board provided with a ground surface exposed to the outside on the back side corresponding to the surface on which the electronic component is mounted, and the electronic component of the flexible printed wiring board are mounted. Conductive reinforcement provided with an opening provided on the back side corresponding to the front surface to reinforce the electronic component mounting surface of the flexible printed wiring board and to face the ground surface of the flexible printed wiring board A plate, a flexible conductive material having conductivity having shape recovery and flexibility, and a main ground portion having a main stable ground surface, and the flexible conductive material, The reinforcing plate and the ground surface of the flexible printed wiring board in the opening of the reinforcing plate and the ground surface of the main ground portion are sandwiched between the reinforcing plate and the opening of the reinforcing plate by the flexible conductive material. A ground plane of the flexible printed wiring board, by comprising by grounded to the ground plane of the main ground portion, to solve the problems described above.

  The electronic circuit manufacturing method of the present invention includes a flexible printed wiring board provided with a ground surface exposed to the outside on the back side corresponding to the surface on which the electronic component is mounted, and the electronic circuit of the flexible printed wiring board. Provided on the back side corresponding to the surface on which the component is mounted, has an opening arranged to reinforce the electronic component mounting surface of the flexible printed wiring board and face the ground surface of the flexible printed wiring board Manufacturing an electronic circuit having a conductive reinforcing plate, a flexible conductive material having conductivity having shape recovery and flexibility, and a main ground portion having a main stable ground plane The flexible conductive material is sandwiched between the ground plane of the reinforcing plate and the flexible printed wiring board in the opening of the reinforcing plate and the ground plane of the main ground portion. And the step of grounding the reinforcing plate and the ground surface of the flexible printed wiring board in the opening of the reinforcing plate to the ground surface of the main ground portion by using a flexible conductive material. To do.

  In addition, the portable terminal of the present invention has a flexible printed wiring board having a ground surface exposed to the outside on the back side corresponding to the surface on which the electronic component is mounted, and the electronic component of the flexible printed wiring board is mounted. Conductive with an opening provided on the back side corresponding to the front surface to reinforce the mounting surface of the electronic component of the flexible printed wiring board and to face the ground surface of the flexible printed wiring board A flexible conductive material, a flexible conductive material having conductivity having shape recovery and flexibility, and a main ground portion having a main stable ground surface Are sandwiched between the ground plane of the flexible printed wiring board and the ground plane of the main ground section in the reinforcing plate and the opening of the reinforcing plate, and the reinforcing plate and the reinforcing plate are opened by a flexible conductive material. A ground plane of the flexible printed circuit board portion, by having an electronic circuit formed by the ground on the ground surface of the main ground portion, to solve the problems described above.

  That is, according to the present invention, means for connecting at least three surfaces of the reinforcing plate, the ground surface of the flexible printed wiring board in the opening of the reinforcing plate, and the ground surface of the main ground portion to each other in a conductive state. As a flexible conductive material that has conductivity with shape recovery and flexibility, it is possible to obtain a high shielding effect without hindering the freedom of electronic circuit design and housing design. It has become.

  In the present invention, the ground surface of the flexible printed wiring board in the opening of the reinforcing plate and the reinforcing plate is connected to the ground of the main ground portion by the flexible conductive material having conductivity having shape restoration property and flexibility. Since the surface is grounded, it is possible to effectively suppress noise generated by unnecessary radiation, interference waves, or the like without impeding weight reduction and increasing costs.

  Hereinafter, an embodiment of an electronic circuit of the present invention, a method for manufacturing the same, and a mobile terminal including the electronic circuit will be described with reference to the drawings.

  In the present embodiment, a mobile phone terminal is cited as an example of the mobile terminal according to the present invention. Of course, the content described here is merely an example, and it goes without saying that the present invention is not limited to this example. Yes.

[Outline of flexible printed wiring board]
1 and 2 are enlarged views of an electronic circuit according to an embodiment of the present invention, particularly a circuit portion in the vicinity of a flexible printed wiring board.

  FIG. 1 is an enlarged view of a part of the surface side on which an electronic component 2 such as an IC chip is mounted, of the front and back surfaces of the flexible printed wiring board 1 of the present embodiment. FIG. 2 shows an enlarged part of the back surface side corresponding to the surface on which the electronic component 2 is mounted, of the front and back surfaces of the flexible printed wiring board 1 of the present embodiment.

  In this embodiment, on the back side of the flexible printed wiring board 1, a reinforcing plate 10 is attached to a portion corresponding to the mounting portion of the electronic component 2 on the front side. Moreover, in this embodiment, the said reinforcement board 10 is formed with conductors, such as a metal which has the magnitude | size which can cover at least the mounting part of the surface side electronic component 2 of the said flexible printed wiring board 1. FIG. The conductor reinforcing plate 10 is provided with an opening 11 as shown in FIG.

  3 shows the flexible printed wiring board 1, the electronic component 2 (circuit portion) mounted on the front side of the flexible printed wiring board 1, and a conductor made of affixed to the back side of the flexible printed wiring board 1. The cross section of the reinforcing plate 10 is shown enlarged. In the cross-sectional view of FIG. 3, the thickness of the flexible printed wiring board 1 and the conductor reinforcing board 10 in the drawing, the width of the opening 11 and the like are exaggerated as appropriate for easy illustration. It does not correspond to the scale of. FIG. 3 also shows a cross section of the main wiring board 20 of the portable terminal and a conductor cushion material 30 described later.

  As shown in FIG. 3, the flexible printed wiring board 1 according to the present embodiment is formed on a base material 5 made of an insulating and flexible film-like resin, and on both surfaces of the base material 5. The wiring layers 4 and 6 are formed of conductive wiring patterns, and the insulating resist layers 7 and 8 are formed on the wiring layers 4 and 6. Of the wiring layers 4 and 6, the wiring layer 4 in the portion where the electronic component 2 is provided on the surface side where the conductor reinforcing plate 10 is particularly attached is a ground layer.

  The flexible printed wiring board 1 includes insulating resist layers 7 and 8 on both front and back surfaces. In the present embodiment, at least a portion corresponding to the opening 11 of the conductor reinforcing plate 10 is provided. The resist layer 7 is not formed on the wiring layer 4 so that the wiring layer 4 as the ground layer is exposed to the outside. That is, in other words, according to the present embodiment, the conductor reinforcing plate 10 is formed so that the opening 11 substantially matches the externally exposed portion of the ground layer, that is, the external exposure of the ground layer from the opening 11. After being aligned so that the portion can be seen, it is affixed to the flexible printed wiring board 1. In other words, in the present embodiment, the flexible printed wiring board 1 is provided with at least a part of the ground on the back side corresponding to the portion where the electronic component 2 is mounted and on the surface where the reinforcing plate 10 is attached. A portion for exposing the layer to the outside is provided, and the opening 11 is aligned so as to substantially match the externally exposed portion of the ground layer, and the conductor reinforcing plate 10 is attached. .

[Method of grounding flexible wiring board ground and reinforcing board to main board ground]
Here, as in the present embodiment, in order to increase the noise resistance by shielding unwanted radiation and interference waves in the flexible printed wiring board on which electronic components and the like are mounted, the ground layer of the flexible printed wiring board The reinforcing plate provided at a very close distance has conductivity such as metal, and further, the ground layer of the flexible printed wiring board and the reinforcing plate such as metal are connected to the ground of the main wiring board of the mobile terminal, for example. Must be grounded (that is, grounded to the casing of the portable terminal). Note that grounding the ground layer of the flexible printed wiring board and the reinforcing plate made of metal, for example, to the ground of the main wiring board through a metal screw or the like, as described above, reduces weight and costs. It is not preferable in terms of the aspect.

  For this reason, in this embodiment, as shown in FIG. 3, the conductor cushioning material 30 having shape restoring property and flexibility and at least the surface of which is conductive is provided in the opening of the conductor reinforcing plate 10. The conductor cushioning material 30 is arranged so as to hang over the portion 11, and the flexible printed wiring board 1 and the conductor reinforcing board 10 on which the electronic component 2 is mounted and the ground layer of the main wiring board 20 of the portable terminal. (The wiring layer 21), the surface of the ground layer (wiring layer 4) exposed to the outside of the flexible printed wiring board 1, the surface of the reinforcing plate 10 made of the conductor and the side surface of the opening 11, and the above By making at least three places of the ground layer (wiring layer 21) of the main wiring board 20 into an electrically conductive state through the conductor cushioning material 30, the above flexible Ground layer of printed wiring board 1 and the conductor-made reinforcing plate 10 (wiring layer 4) so as to be grounded to the ground layer of the main circuit board 20 (wiring layer 21).

  In the present embodiment, the conductive cushion material 30 has, as an example, a conductive material on the outer peripheral portion of the cushion material having shape restoring property and flexibility such as a cylindrical or elliptical sponge or foam rubber. The material (for example, metal thread | yarn or metal cloth) etc. can be mentioned by being wound or stuck. Of course, in the present invention, the shape of the conductor cushion material 30 is not limited to a cylindrical shape, and the material is not limited, and not only the surface but also the inside may have conductivity. When the conductor cushion material 30 is disposed, for example, at least one of the ground layer of the flexible printed wiring board 1, the conductor reinforcing board 10, and the ground layer (wiring layer 21) of the main wiring board 20. It is desirable to prevent the conductor cushion material 30 from being displaced after assembly by attaching the conductor cushion material 30 with, for example, a conductive adhesive or a conductive double-sided tape using the conductive adhesive material.

  As described above, according to the present embodiment, for example, the conductor cushion material 30 in which a conductive material is attached to the outer circumferential portion of a cylindrical cushion material, the flexible printed wiring board 1 and the conductor reinforcement are used. By sandwiching between the board 10 and the ground layer of the main wiring board 20, the outer circumferential part of the conductor cushioning material 30 is deformed and the ground layer exposed part of the flexible printed wiring board 1 and the conductor reinforcing board 10 are deformed. And the ground layer exposed portion of the flexible printed wiring board 1 and the surface of the conductor reinforcing board 10, the ground layer of the main wiring board 20, and the ground layer of the main wiring board 20. As a result, a higher shielding effect can be obtained.

  Further, according to the present embodiment, the ground layer exposed portion of the flexible printed wiring board 1 and the surface of the conductor reinforcing board 10 are connected to the main wiring board 20 via the conductor cushioning material 30 that can be disposed at any place. Since it is grounded to the ground layer, there is no need to perform special screw layout design, wiring pattern design, and electronic component mounting design, for example, when using metal screws to ground the housing. Since a process such as screwing is not required, an increase in cost can be suppressed, and the conductor cushion material 30 is much lighter than a metal screw, which is also effective in reducing the weight of the mobile terminal. It is the target.

  Furthermore, according to the present embodiment, since the conductor cushion material 30 can have a certain thickness, for example, the ground layer exposed portion of the flexible printed wiring board 1 and the surface of the conductor reinforcing plate 10 are used. To the ground layer 21 of the main wiring board 20, at least the conductor cushion is required even when a design that requires some other non-conductive member or the like to be disposed is required. Only by providing a space in which the material 30 can be placed in the other nonconductive member, the ground layer exposed portion of the flexible printed wiring board 1 and the surface of the conductor reinforcing plate 10 and the ground layer of the main wiring board 20 It is possible to dispose another non-conductive member while ensuring grounding.

  4 and 5 show other arrangement examples of the conductor cushion material 30. FIG.

  FIG. 4 shows an example in which the conductor cushioning material 30 is disposed approximately at the center of the opening 11 of the conductor reinforcing plate 10. That is, in FIG. 3 described above, the conductor cushioning material 30 is arranged at the edge of the opening 11 of the conductor reinforcing plate 10 so that the ground contact area between the conductor reinforcing plate 10 and the conductor cushioning material 30 is increased. In FIG. 4, the conductor cushion material 30 is disposed substantially in the center of the opening 11 of the conductor reinforcing plate 10, so that the ground layer of the flexible printed wiring board 1 and the conductor cushion material 30 are grounded. The area is increased.

  FIG. 5 shows an example in which the thickness of the conductor reinforcing plate 10 is larger than those in the examples of FIGS. 3 and 4. That is, as in the example of FIG. 3 and FIG. 4, when the conductor reinforcing plate 10 is thin, it is possible to ground the surface of the conductor reinforcing plate 10 by the conductor cushion material 30. For example, when the conductor reinforcing plate 10 is thick as shown in FIG. 5, there is a possibility that the surface of the conductor reinforcing plate 10 cannot be grounded by the conductor cushion material 30. In such a case, as shown in FIG. 5, the conductor cushioning material 30 is fitted into the opening 11 of the conductor reinforcing plate 10, and the wall surface of the opening 11 of the conductor reinforcing plate 10 is grounded. To do.

  3 to 5 exemplify the case where the conductor reinforcing plate 10 is attached to the resist layer 7 of the flexible printed wiring board 1, the ground layer of the wiring layer 4 and the conductor reinforcing plate 10 are exemplified. Only the resist layer 7 sandwiched between the two is removed, and the conductive reinforcing plate 10 is attached to the wiring layer 4 (ground layer) with, for example, a conductive adhesive or a conductive double-sided tape using the conductive adhesive. Thus, the ground area of the flexible printed wiring board 1 and the conductor reinforcing plate 10 may be made larger.

  In addition to the ground layer of the main wiring board 20, the other party that grounds the ground layer of the flexible printed wiring board 1 may be a stable ground such as the ground terminal of the casing of the portable terminal.

[Summary]
As described above, according to the present embodiment, the opening 11 provided with a conductive surface (ground) on the back side of the single-sided component mounting portion of the flexible printed wiring board 1 and the conductive reinforcing plate 10 having conductivity. The conductive cushioning material 30 having at least the surface of the conductive material is disposed so as to be in contact with both of them, and the conductive cushioning material 30 is connected to the flexible printed wiring board 1, the conductive reinforcing plate 30, and the main wiring. The conductive surface on the back side of the single-sided component mounting portion of the flexible printed wiring board 1 and the opening 11 of the conductive reinforcing plate 10 are brought into contact with the ground of the main wiring board 20 by being sandwiched between the boards 20. Noise induced by a strong electric field signal radiated to the wiring pattern on the flexible printed wiring board 1 by being grounded at It can be effectively suppressed, noise resistance, in particular it is possible to increase resistance to radiation from outside.

  The above description of the embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made according to the design or the like as long as the technical idea according to the present invention is not deviated.

  For example, the present invention can be applied not only to mobile phone terminals but also to various mobile terminals such as PDAs (Personal Digital Assistants), portable music players, and portable television broadcast receivers.

It is a figure which expands and shows a part of the surface side by which an electronic component is mounted among the front and back both surfaces of the flexible printed wiring board of this embodiment. It is a figure which expands and shows a part of the back surface side corresponding to the surface where the electronic component is mounted among the front and back both surfaces of the flexible printed wiring board of this embodiment. It is a figure which expands and shows the cross section of the flexible printed wiring board of this embodiment, the electronic component mounted in the surface side, and the conductor reinforcement boards affixed on the back surface side. It is a figure which shows the grounding state at the time of arrange | positioning the cushion material made from a conductor in the approximate center of the opening part of a conductor reinforcement board. It is a figure which shows the earthing | grounding state at the time of arrange | positioning the conductor cushioning material in the approximate center of the opening part of the conductor reinforcement board with large thickness.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Flexible printed wiring board, 2 Electronic components, 4 Wiring layer (ground layer) of flexible printed wiring board, 5 Base material of flexible printed wiring board, 6 Wiring layer of flexible printed wiring board, 7, 8 Resist of flexible printed wiring board Layer, 10 conductor reinforcing plate, 11 opening, 20 main wiring board, 21 wiring layer (ground layer) of main wiring board, 30 conductor cushioning material

Claims (6)

A flexible printed wiring board having a ground surface exposed to the outside on the back side corresponding to the surface on which the electronic component is mounted;
Provided on the back side corresponding to the surface on which the electronic component of the flexible printed wiring board is mounted, reinforces the mounting surface of the electronic component of the flexible printed wiring board, and provides the ground surface of the flexible printed wiring board. A conductive reinforcing plate having an opening arranged to face the surface;
A flexible conductive material having electrical conductivity with shape restoration and flexibility;
A main ground portion having a main stable ground plane,
The flexible conductive material is sandwiched between the reinforcing plate and the ground surface of the flexible printed wiring board in the opening of the reinforcing plate and the ground surface of the main ground portion. The reinforcing plate and the ground surface of the flexible printed wiring board in the opening of the reinforcing plate are grounded to the ground surface of the main ground portion.
An electronic circuit characterized by that.   2. The electronic circuit according to claim 1, wherein the flexible conductive material is a cushion material provided with a conductive material on at least a surface thereof.   3. The electronic circuit according to claim 2, wherein the conductive material provided on the surface of the cushion material is formed of a metal thread.   2. The electronic circuit according to claim 1, wherein the ground surface of the flexible printed wiring board and the reinforcing plate are attached with a conductive adhesive. A flexible printed wiring board having a ground surface exposed to the outside on the back side corresponding to the surface on which the electronic component is mounted;
Provided on the back side corresponding to the surface on which the electronic component of the flexible printed wiring board is mounted, reinforces the mounting surface of the electronic component of the flexible printed wiring board, and provides the ground surface of the flexible printed wiring board. A conductive reinforcing plate having an opening arranged to face the surface;
A flexible conductive material having electrical conductivity with shape restoration and flexibility;
A manufacturing method for manufacturing an electronic circuit having a main ground portion having a main stable ground plane,
Sandwiching the flexible conductive material between the ground plane of the reinforcing plate and the flexible printed wiring board in the opening of the reinforcing plate and the ground plane of the main ground portion;
A step of grounding the reinforcing plate and the ground surface of the flexible printed wiring board in the opening of the reinforcing plate to the ground surface of the main ground portion by the flexible conductive material,
A method for manufacturing an electronic circuit. A flexible printed wiring board having a ground surface exposed to the outside on the back side corresponding to the surface on which the electronic component is mounted;
Provided on the back side corresponding to the surface on which the electronic component of the flexible printed wiring board is mounted, reinforces the mounting surface of the electronic component of the flexible printed wiring board, and provides the ground surface of the flexible printed wiring board. A conductive reinforcing plate having an opening arranged to face the surface;
A flexible conductive material having electrical conductivity with shape restoration and flexibility;
A main ground portion having a main stable ground plane,
The flexible conductive material is sandwiched between the reinforcing plate and the ground surface of the flexible printed wiring board in the opening of the reinforcing plate and the ground surface of the main ground portion. An electronic circuit formed by grounding a reinforcing plate and a ground surface of the flexible printed wiring board in the opening of the reinforcing plate to the ground surface of the main ground portion;
A portable terminal characterized by that.

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