JP2013038154A - Flexible printed circuit board structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an FPC structure which increases the flexibility of assembling without making the size larger than conventional FPC structures.SOLUTION: A flexible printed circuit board (FPC) structure 2 includes: an FPC 4 where an electronic circuit is formed on an insulation film; and a reinforcement plate 5 bonded to one main surface (B surface) of the FPC 4. An electronic component 41 and the like are disposed in a region (4b) where the FPC 4 overlaps with the reinforcement plate 5, from among a rear surface (A surface) of the FPC 4 which is located on the opposite side of the B surface. When an electronic circuit needs to be changed, multiple pads 21 to 26, in which the electronic components for change are mounted, are disposed on the A surface. In at least one of the pads 21 to 26 (pads 21, 22), at least parts of regions occupied by the pads 21, 22 exist in the region (4a) of the A surface where the FPC 4 does not overlap with the reinforcement plate 5.

Description

  The present invention relates to downsizing of a reinforcing plate in a flexible printed circuit board structure.

  A flexible printed circuit board (FPC) is a wiring material formed by printing and wiring an electric circuit on an insulating film, and has characteristics such as high flexibility, wiring labor saving, small size and light weight. It is used. In the FPC, an electronic component is mounted on a portion (reinforcement portion) reinforced with a reinforcing plate in the component mounting surface (hereinafter, the FPC on which the electronic component is mounted is referred to as a flexible printed circuit board structure). The portion that is not reinforced by the reinforcing plate (flexible portion) can be freely bent due to its nature (see Patent Document 1), and the more this portion, the greater the degree of freedom of assembly to other circuit boards and the like. Become.

JP-A-10-242668

  By the way, electronic devices and the like using FPC structures are being miniaturized with mobile phones and the like at the top, and it is desirable that FPC structures be freely bent and assembled in a small and narrow casing. It is. If the length of the flexible portion is simply extended, the degree of freedom of assembly can be increased. However, it is conceivable that the FPC structure cannot be accommodated in a narrow housing against the demand for downsizing the FPC structure.

  In view of the above-described problems, an object of the present invention is to provide an FPC structure that can increase the degree of assembly freedom without increasing the size of the conventional device.

  In order to solve the above problems, a flexible printed board structure of the present invention includes a flexible printed board in which an electronic circuit is formed on an insulating film, and a reinforcing plate provided on one main surface of the flexible printed board, The electronic component that constitutes the electronic circuit is arranged in a region of the back surface opposite to the main surface of the flexible printed circuit board, in which the flexible printed circuit board and the reinforcing plate overlap, and the back surface A plurality of pads on which the electronic component is mounted, wherein at least one of the pads occupies at least part of a region occupied by the pads, the flexible printed circuit board and the reinforcing plate among the back surface It exists in the area where and do not overlap.

  The flexible printed circuit board structure of this invention can provide the FPC structure which can increase an assembly | attachment freedom degree, without enlarging larger than before by providing the above-mentioned structure.

It is a figure ((a) is a top view, (b) is a bottom view) which shows the liquid crystal display module in which the FPC structure concerning one Embodiment of this invention was integrated. It is an external appearance perspective view (A surface side) of the FPC structure which concerns on one Embodiment of this invention. It is an external appearance perspective view (B surface side) of the FPC structure which concerns on one Embodiment of this invention.

FIG. 1 is a diagram illustrating an example of a liquid crystal display module in which an FPC structure according to an embodiment of the present invention is incorporated.
FIG. 1A is a plan view, and FIG. 1B is a bottom view.
The liquid crystal display module 1 is used as a display unit of a mobile phone.
The liquid crystal display module 1 includes a liquid crystal display 3 and an FPC structure 2.

The FPC structure 2 includes an FPC 4, a reinforcing plate 5 made of a synthetic resin and bonded to the FPC 4, and a connector 6.
FIG. 2 is an external perspective view of the FPC structure 2 according to the embodiment of the present invention.
3 is an external perspective view of the FPC structure according to the embodiment of the present invention as viewed from the arrow B side in FIG.

The FPC 4 is a flexible printed board in which an electronic circuit is formed on an insulating film.
A reinforcing plate 5 is bonded to the main surface of the FPC 4 on the side indicated by an arrow B in FIGS. 2 and 3, and a connector 6 connected to an electronic circuit is provided at one end. Hereinafter, the main surface on the side indicated by the arrow B in FIGS. 2 and 3 is referred to as the B surface, and similarly, the main surface on the side indicated by the arrow A is referred to as the A surface.
The portion 4b of the FPC 4 to which the reinforcing plate 5 is connected has no or low flexibility, but the portions 4a and 4c of the FPC 4 to which the reinforcing plate 5 is not connected have high flexibility.

When the liquid crystal display module 1 is incorporated in a housing, wiring is freely routed by bending the portions 4a and 4c of the FPC 4, and the connector 6 is connected to another circuit board or the like.
The FPC 4 is provided with pads 21 to 30 for mounting electronic components, and electronic components 41 and 42 are mounted thereon.

Hereinafter, the positions where the pads 21 to 30 are provided and the positions where the electronic components 41 and 42 are mounted will be described. First, matters necessary for the following description will be described in advance with reference to FIG.
A region corresponding to a portion where the FPC 4 and the reinforcing plate 5 overlap in the A surface of the FPC 4 is referred to as a region R1.

In addition, the outer edge of the region R1 is referred to as a boundary E1. A region separated from the outer edge E1 by L1 or more inward is referred to as a region R2.
In addition, the outer edge of the region R2 is referred to as a boundary E2. A region surrounded by the outer edges E1 and E2 is referred to as a region R3.
Further, in the A surface of the FPC 4, a region other than the region R 1, that is, a region corresponding to a portion where the FPC 4 and the reinforcing plate 5 do not overlap is referred to as a region R 4.

Next, the positions of the pads and electronic components will be described.
The electronic components 41 and 42 are mounted in the region R2. More specifically, the electronic component 41 is mounted so as to be connected to the pads 27 and 28 provided in the region R2, and the electronic component 42 is mounted so as to be connected to the pads 29 and 30 provided in the region R2. . This is because when an electronic component is mounted in the region R3, if the FPC 4 is bent, the electronic component mounted in the region R3 is not less stressed, and a failure of the electronic component or a connection failure may occur.

Here, the distance L1 away from the outer edge E1 may normally be about 2 mm, but what value L1 should be set is a design matter, and an appropriate value is derived by experiment, simulation, etc. That's fine. When L1 is 0, the region R3 disappears and the regions R1 and R2 match.
Here, the pads 21 to 26 are electronic when there is a need to change the electronic circuit, such as when a component is not actually mounted and a malfunction occurs or a circuit parameter such as a resistance value needs to be adjusted. This is a spare pad on which a component is mounted. Therefore, it is not used when there is no change in the electronic circuit. Such a spare pad is often provided especially in a trial production stage.

In the present embodiment, among the spare pads 21 to 26, a part of the region occupied by the pads 21 and 22 exists in the region R4 where the FPC 4 and the reinforcing plate 5 do not overlap. With this configuration, the size of the reinforcing plate can be made smaller than in the case where all of the electronic components and pads are provided in a region where the FPC and the reinforcing plate overlap as in the conventional case.
Even if it does in this way, there is no problem when it is not necessary to change an electronic circuit after that.

  On the other hand, when it is necessary to change the electronic circuit, as an example, electronic components are mounted on the spare pads 21 and 22, but if mounted as they are, the reinforcing plate 5 and the FPC 4 are not overlapped. A new electronic component will be mounted, and it will be influenced by the bending stress of FPC4. Therefore, instead of the reinforcing plate 5, a reinforcing plate larger than the reinforcing plate 5 that can reinforce a region where a new electronic component is mounted is adhered to the FPC 4.

However, in this case, it is only necessary to change the size of the reinforcing plate 5, and it is not necessary to change the circuit pattern provided in the FPC 4, so there is no need to change the production line of the FPC 4, and the influence of the circuit change is affected. Can be kept to a small range.
Note that the arrangement of the spare pads 21 to 26 varies depending on the contents of the circuit pattern of the electronic circuit, and therefore cannot be arranged freely. Even if the contents of the circuit pattern are taken into consideration, when a part of the area occupied by each of the spare pads 21 to 26 can be present in the area R4 where the FPC 4 and the reinforcing plate 5 do not overlap with each other, it is even more than before. The size of the reinforcing plate can be reduced.

As described above, in this embodiment, the size of the reinforcing plate can be made smaller than in the case where all of the electronic components and pads are provided in a region where the flexible printed circuit board and the reinforcing plate overlap as in the conventional case. As the reinforcing plate becomes smaller, the flexible part can be enlarged, so that the degree of freedom of assembly can be increased.
<Modification>
Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention. Of course.
(1) Although the above embodiment has been described with an example of a liquid crystal display module used as a display unit of a mobile phone, the present invention is not limited to this. It can also be used as an FPC structure used in other types of devices.
(2) The above-described embodiments and modifications may be combined partially or all together.

  The flexible printed circuit board structure of the present invention is suitable as wiring between circuit modules in an electronic device that requires downsizing.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display module 2 FPC structure 3 Liquid crystal display 4 FPC
5 Reinforcing plate 6 Connector 21-30 Pad 41, 42 Electronic component R1-R3 area E1 boundary (outer edge of R1)
E2 boundary (outer edge of R2)

Claims (3)

A flexible printed circuit board in which an electronic circuit is formed on an insulating film;
A reinforcing plate provided on one main surface of the flexible printed circuit board,
The electronic component constituting the electronic circuit is arranged in a region of the back surface opposite to the main surface of the flexible printed circuit board in which the flexible printed circuit board and the reinforcing plate overlap,
A plurality of pads disposed on the back surface on which the electronic component is mounted;
At least one of the pads occupies at least a part of a region occupied by the pad in a region of the back surface where the flexible printed circuit board and the reinforcing plate do not overlap. body. 2. The flexible printed circuit board structure according to claim 1, wherein the electronic component is disposed on the inner side with a predetermined distance or more away from an outer edge of a region where the flexible printed circuit board and the reinforcing plate overlap. Each of all the pads has at least a part of a region occupied by the pad in a region of the back surface where the flexible printed circuit board and the reinforcing plate do not overlap with each other. The flexible printed circuit board structure as described.

Images