JPH054289Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a bent flexible printed wiring board having an L-shape, U-shape, etc.
In particular, the present invention relates to a bent flexible printed wiring board that is bent at a bent corner portion so that its extending direction can be freely changed.

[Conventional technology]

Flexible printed wiring boards (hereinafter referred to as FPCs) come in various shapes such as L-shape and U-shape due to space constraints, and can be bent at bent corners or folded back as necessary to extend the FPC. It can be used by freely changing the orientation.

For example, as shown in FIG.
As shown in FIG. 4, a U-shaped FPC 2 with bent corners A and B in the middle of a and 2b is
There are cases where it is desired to use the straight portions 2a and 2b so that they are orthogonal to each other. In such a case, the FPC is bent into the desired shape at the bending corner B at the position indicated by the broken line.

[Problem that the invention attempts to solve]

However, in a conventional bent FPC, for example, in the example shown in Fig. 3, the inner edges of the bent corners A and B are nearly perpendicular, and the conductive foil pattern formed on the insulating base It is also almost perpendicular to the shape of the inner edge of the insulating base. Therefore, when the FPC is bent or folded back at the bent corner A, stress is concentrated on the inner edge of the bent corner A, causing a problem that cracks may occur and breakage may occur.

The present invention was devised in view of the problems of the prior art, and its purpose is to provide a bent FPC in which stress is less likely to concentrate on the inner edge of the bent corner.

[Means for solving problems]

Next, the present invention will be explained with reference to FIGS. 1 and 2, which illustrate one embodiment of the present invention.

In a bent type FPC having one or more bent corner parts D and C, and in which the direction of extension of the FPC is changed by bending at the bent corner part D, the inner edge 20 of the bent corner part D is rounded. Along with gouging, the outer edge 22 of the bent corner portion is expanded outward in accordance with the shape of the gouged portion R, and the foil guiding pattern 12b formed at the bent corner portion D is also shaped to follow the shape of the gouged portion R.

[Effect]

The inner edge 20 of the bent corner D of the FPC is hollowed out into an R shape and has a small curvature, and the conductive foil pattern 1 is formed in the bent corner D.
2b also has a small curvature shape, and even if the FPC is bent at the bending corner D, stress is dispersed and does not concentrate on the inner edge 20.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

1 and 2 show an embodiment of the present invention. In these figures, the reference numeral 10 indicates a U-shaped box having corner portions C and D bent at right angles.
In the FPC, straight portions 10a and 10b extend in parallel,
A wide portion 10c is formed at the tip of the straight portions 10a, 10b, in which a land for connecting electronic components and the like is formed. The inner edge 20 of the corner part D is the straight part 1
0b is hollowed out in an R shape on the inside to form an inner edge shape with a gentle curvature.On the other hand, the outer edge 22 of the corner portion D has a shape that is expanded outward by the amount that the inner edge has been hollowed out. ing. In other words, the width d of the FPC at the location where the gouge is formed is the same as the width of the straight portion 10b, thereby avoiding stress concentration on the part where the gouge is formed, and The wiring spacing of the conductive foil pattern can be kept constant.

The FPC 10 has a foil conductive pattern 12 formed on a thin insulating base 11 made of polyester or the like, and a protective film 13 made of polyester or the like formed thereon.
Adhesive layers are interposed on both upper and lower surfaces of the foil-conducting pattern 12, so that the base 2, the pattern 12, and the protective film 13 are laminated and integrated. Figure 2 shows a bent shape with a part of the protective film 13 formed on the surface cut out.
This is an enlarged plan view of the FPC, and at a corner C, a foil-conducting pattern 12 is formed in a nearly right-angled shape, as indicated by reference numeral 12a. On the other hand, at the corner portion D, the foil guiding pattern 12 is formed in a shape that follows the R shape of the inner edge 20, as shown by reference numeral 12b.

Now, if we try to bend the FPC 10 twice at the corner D so that the straight part 10b stands up perpendicularly from the straight part 10a as shown by the imaginary line in Figure 1, then the position shown by the broken lines 24 and 26 in Figure 2 What is necessary is just to bend each at each point. In other words, the bending position 24 is located away from the conventional bending position 25.

As described above, in this embodiment, the inner edge 20 of the corner portion D that is used after being bent has a shape with a small curvature, and the curvature of the foil guiding pattern 12b formed on the corner portion D is also small. When it is bent, etc., the degree of stress concentration on the inner edge of the corner portion D is small, and there is no risk of cracking or wire breakage.

In addition, in the conventional method, as shown in FIG. 3, the two bending positions at the corner were very close to each other, so the stress caused by bending was concentrated on the inner edge of the corner. Since the bending positions 24 and 26 are separated by a distance, stress is less likely to be concentrated on the inner edge 20 of the corner portion D. Furthermore, since the bending positions 24 and 26 are separated from each other compared to the conventional example (see FIG. 3), the bending is easier and the workability is excellent.

In the above-mentioned embodiments, only the shape of the corner portion D, which is used by bending, was mentioned, but if the corner portion C has the same structure as the corner portion D, concentration of stress can also be avoided in the corner portion C. , the FPC can be bent and used at either corner C or D without concentrating stress on the inner edge.

In particular, the ends 10C, 10C of the FPC are respectively attached to relatively slidable members, and the straight parts 12a,
When 12b slides frequently, there is a problem that the stress due to repeated loads concentrates on the inner edges of corner portions C and D and tends to weaken, but the shape of corner portion C also differs from corner portion D. Having a similar shape can prevent fatigue failure due to stress concentration.

[Effect of idea]

As is clear from the above explanation, according to the present invention,
Stress concentration at the inner edge of the bent corner of the FPC is avoided, and the adverse effects associated with this stress concentration are eliminated.

[Brief explanation of the drawing]

Figure 1 shows one embodiment of the present invention, which is a bent type.
A plan view of the FPC, Fig. 2 is an enlarged plan view of its main parts, Fig. 3 is a plan view of a conventional bent type FPC,
FIG. 4 is a plan view of the bent corner portion bent to change the direction of extension. 10...FPC, 12...Foil conductive pattern, 12
a, 12b...Foil-conducting pattern bent portion, 20...Inner edge of corner portion, 22...Outer edge of corner portion, C, D
...Bent corner part.

Claims (1)

[Scope of utility model registration request] In a bent type flexible printed wiring board in which the flexible printed wiring board has one or more bent corner portions, and the direction in which the flexible printed wiring board extends is changed by bending at the bent corner portion, the inner edge of the bent corner portion is rounded. At the same time, the outer edge of the bent corner is expanded outward in accordance with the R shape of the hollowed out part, and the conductive foil pattern formed at the bent corner is also shaped to follow the R shape of the hollowed out part. A bendable flexible printed wiring board characterized by: