Flexible Printed Circuit Board

Abstract

To provide a flexible printed wiring board capable of stably maintaining the state of a folded portion.SOLUTION: A flexible printed wiring board includes a wiring board body portion 111 having a folded portion 150, and a holding portion 112 that is integrally connected to the wiring board main body 111 and holds a portion where the wiring board body portion 111 overlaps with the folded portion 150, and at least a part of the portion where the wiring board body portion 111 overlaps with the folded portion 150 is sandwiched between an adjacent portion of the wiring board body portion 111 adjacent to the holding portion 112 and the holding portion 112 that is folded back and adhered with an adhesive.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a flexible printed circuit board used in a state having a folded-back portion.

Background Art

[0002] Generally, a flexible printed circuit board (hereinafter referred to as "FPC") is obtained by cutting a sheet-like material (intermediate product) composed of a film and wiring (conductor such as copper foil) formed by etching on the film. Here, for various purposes such as the purpose of lengthening the FPC and the purpose of reducing the amount of waste remaining after taking out a plurality of FPCs by cutting from the sheet-like material, the FPC may be used in a state where a part of the FPC is folded back.

[0003] In this case, in the portion overlapped by folding, due to springback, a force acts on the FPC to return to its original state. Therefore, by adhering with an adhesive, the state of the folded-back portion is maintained.

[0004] However, during transportation or use, etc., there is a risk that the portion adhered by the adhesive may peel off due to vibration, impact, or a decrease in adhesive strength due to changes over time or environmental changes. In particular, in the folded-back portion, a part may peel off from around the corner portion, and the peeling may gradually spread.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a flexible printed wiring board capable of stably maintaining the state of a folded portion.

Means for Solving the Problems

[0007] The present invention employs the following means to solve the above problems.

[0008] That is, the flexible printed wiring board of the present invention has a wiring board main body portion having a folded portion, and a holding portion integrally connected to the wiring board main body portion for holding a portion where the wiring board main body portion overlaps due to the folded portion, and is provided with The wiring board main body has a circuit for electrical wiring, and the holding part does not have a circuit for electrical wiring. At least a part of the portion where the wiring board main body portion overlaps due to the folded portion is folded and adhered by an adhesive and while remaining in a flat state and is sandwiched between the holding portion and is characterized in this state.

[0009] According to the present invention, by providing the holding portion configured as described above, it is possible to suppress the folded portion from peeling off. Note that the "adhesive" refers to a substance having adhesiveness at normal temperature and adhering to an adherend under a light pressure.

[0011] In the wiring board main body portion, generally, an electric wiring circuit composed of a conductor such as a copper foil is provided, so that the rigidity becomes high and it becomes difficult to bend at the bent portion. On the other hand, since it is not necessary to provide a circuit in the holding portion, the degree of design freedom is high, and it is not necessary to provide a conductor at the connection portion where the wiring board main body portion and the holding portion are connected. Therefore, at this connection portion, the rigidity can be lowered to make it easy to bend. 。

[0012] A spacer may be disposed between portions on both sides of the folded portion in the wiring board main body portion.

[0013] Further, the folded portion has a first folded portion and a second folded portion, and it is also preferable that a single spacer is disposed between portions on both sides of the first folded portion and between portions on both sides of the second folded portion in the wiring board main body portion.

[0014] Furthermore, the folded portion has a first folded portion and a second folded portion, and a first spacer is disposed between portions on both sides of the first folded portion in the wiring board main body portion, and a second spacer is disposed between portions on both sides of the second folded portion in the wiring board main body portion, which is also preferable.

[0015] By adopting a configuration in which a spacer is disposed as described above, the radius of curvature of the bent portion in the folded portion can be increased by the amount of the spacer provided.

[0016] The bent portion between the wiring board main body portion and the holding portion preferably has a low-strength structure with a lower bending strength than the bent portion in the wiring board main body portion.

[0017] Thereby, the holding portion can be easily bent, and the springback force when bent can be suppressed.

[0018] The low-strength structure is preferably constituted by at least one through hole provided along the bent portion between the wiring board main body portion and the holding portion.

[0019] Also, it is also preferable that the low-strength structure is constituted by at least one slit provided along the bent portion between the wiring board main body portion and the holding portion.

[0020] Furthermore, it is also preferable that the low-strength structure is provided at at least one location along the bending portion between the wiring board main body portion and the holding portion, and is constituted by a thin portion that is thinner than the wiring board main body portion and the holding portion.

[0021] Also, it is also preferable that a straight line including the bending line for bending the holding portion is configured to be located on the opposite side of a straight line including another bending line in the wiring board main body portion with respect to the adhesive portion of the holding portion.

[0022] Note that the above-described configurations can be adopted in combination as much as possible.

Advantages of the Invention

[0023] As described above, according to the present invention, the state of the folded-back portion can be stably maintained.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

BEST MODE FOR CARRYING OUT THE INVENTION

[0025] Hereinafter, with reference to the drawings, the best mode for carrying out the present invention will be exemplarily and specifically described based on embodiments. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only to those, unless otherwise specifically described. Hereinafter, in the folding line, in the figure, the line where the folding line part is folded toward the front side of the drawing is referred to as a "mountain folding line", and the line where the folding line part is folded toward the depth side of the drawing is referred to as a "valley folding line". Note that the flexible printed circuit board (hereinafter referred to as "FPC") according to this embodiment can be suitably used, for example, for an FPC bus bar module for voltage monitoring of a battery cell mounted on an automobile. In addition, in the following description, the "adhesive" means a substance having adhesiveness at normal temperature and adhering to an adherend under a light pressure, and as a specific example, a pressure-sensitive adhesive can be cited.

[0026] (Embodiment 1) With reference to FIGS. 1 to 3, the FPC 100 according to Embodiment 1 of the present invention will be described. FIG. 1 is a plan view showing the state of the FPC 100 according to Embodiment 1 of the present invention before folding back. FIG. 2 is an explanatory diagram of the bending procedure of the FPC 100 according to Embodiment 1 of the present invention, and shows the state of the FPC 100 for each procedure in a plan view. FIG. 3 is a schematic cross-sectional view of the FPC 100 according to Embodiment 1 of the present invention, FIG. 3(a) is a cross-sectional view taken along line AA in FIG. 2(c), and FIG. 3(b) is a cross-sectional view taken along line BB in FIG. 2(c).

[0027] <Configuration of FPC> Since the basic structure of the FPC is a known technique, a detailed description thereof will be omitted. Generally, it is composed of a base film, wirings provided on the base film and formed by etching conductors such as copper foils, and a cover film covering the wirings. In the FPC 100 according to this embodiment, the wiring (circuit 110a) provided inside is schematically shown by a dotted line.

[0028] The FPC 100 according to this embodiment includes a wiring board main body portion 111 having a folded portion 150, and a holding portion 112 integrally connected to the wiring board main body portion 111 and for holding a portion where the wiring board main body portion 111 overlaps due to the folded portion 150. The wiring board main body portion 111 has a circuit 110a for electrical wiring. The holding portion 112 does not have a circuit for electrical wiring. However, in the holding portion 112, it is not necessarily configured not to have a circuit.

[0029] In the FPC 100 according to this embodiment, it is folded at three bending sites. That is, in FIG. 1, it is bent along the first valley fold line L1, the second valley fold line L2, and the third valley fold line L3. For convenience, among the wiring board main body portion 111, the portions divided by two folding lines (the first valley fold line L1 and the second valley fold line L2) are respectively referred to as the first main body portion 111A, the second main body portion 111B, and the third main body portion 111C.

[0030] A spacer 120 made of a foam material is provided on the second main body portion 111B. Adhesives are applied to both surfaces of the spacer 120. An adhesive 131 is provided on the third main body portion 111C. Thereby, after the folding process, by going through a pressing process, it becomes possible to bond the folded portion. Further, an adhesive 132 is similarly provided on the holding portion 112. In this embodiment, the case of using a spacer 120 made of a foam material is shown, but the material of the spacer 120 is not particularly limited.

[0031] <Folding Procedure of FPC> First, along the first valley fold line L1, the portion between the first main body part 111A and the second main body part 111B is bent (see Fig. 2(a)). Next, along the second valley fold line L2, the portion between the second main body part 111B and the third main body part 111C is bent (see Fig. 2(b)). Finally, along the third valley fold line L3, the portion between the third main body part 111C and the holding part 112 is bent (see Fig. 2(c)). Then, by applying pressure at room temperature (pressurizing step), the respective parts are adhered at the folded-back part 150.

[0032] <Advantages of the FPC According to this Embodiment> According to the FPC 100 according to this embodiment, a part of the first main body part 111A and the second main body part 111B among the overlapping parts of the wiring board main body part 111 by the folded-back part 150 is sandwiched between the adjacent part (the third main body part 111C) adjacent to the holding part 112 in the wiring board main body part 111 and the folded-back and adhered holding part 112 (see Fig. 3).

[0033] Thereby, it is possible to suppress the folded-back part 150 from peeling off. Therefore, it becomes possible to stably maintain the state of the folded-back part 150. Here, it is not necessary to provide a circuit in the holding part 112, and it is not necessary to provide a conductor such as a copper foil at the connection part where the wiring board main body part 111 and the holding part 112 are connected. Therefore, if a configuration without providing a conductor is adopted at this connection part, the holding part 112 can be made easier to bend. However, it is not necessarily the case that the provision of a conductor at the above connection part is excluded.

[0034] Also, in the FPC 100 according to the present embodiment, a spacer 120 is disposed between the portions on both sides of the folded-back portion in the wiring board main body portion 111. More specifically, in the FPC 100 according to the present embodiment, it has a first folded-back portion (the portion where the first valley fold line L1 is bent) and a second folded-back portion (the portion where the second valley fold line L2 is bent). And a single spacer 120 is disposed between the portions on both sides of the first folded-back portion in the wiring board main body portion 111 and between the portions on both sides of the second folded-back portion (see FIG. 3). In this way, By adopting the configuration of arranging the spacer 120, the radius of curvature of the bent portion in the folded-back portion can be increased by the amount of the spacer 120 provided. Thereby, the spring-back force acting on the folded-back portion can be relaxed. Also, disconnection of the circuit 110a for electrical wiring can be suppressed.

[0035] In addition, in the present embodiment, semicircular notches are provided on both sides of each fold line so that the position of the portion to be bent is easily understood (see FIGS. 1 and 2). However, as a mark for the portion to be bent, other configurations can also be adopted. For example, in the FPC 100, since copper foil or the like can be seen through from the cover film, a mark can also be provided by devising the shape of the copper foil.

[0036] <Low-strength structure> The bent portion between the wiring board main body portion 111 and the holding portion 112 is preferably formed to have a low-strength structure with a lower bending strength than the bent portion in the wiring board main body portion 111 in order to facilitate bending and reduce the spring-back force. Hereinafter, with reference to FIG. 4, an example of the low-strength structure will be described. FIG. 4 is a diagram showing an example of the low-strength structure according to the embodiment of the present invention.

[0037] The low-strength structure shown in Fig. 4(a) is composed of a plurality of through-holes 115 provided along the bending portion between the wiring board main body portion 111 (the third main body portion 111C) and the holding portion 112. In the illustrated example, a plurality of through-holes 115 are provided, but as shown by the dotted line in the figure, a configuration in which only one through-hole 115a is provided can also be adopted.

[0038] The low-strength structure shown in Fig. 4(b) is composed of at least one slit (cut) 116 provided along the bending portion between the wiring board main body portion 111 (the third main body portion 111C) and the holding portion 112. In this embodiment, through-holes 116a are provided on both sides of the slit 116 to suppress the tearing from spreading from both ends of the slit 116. Also, in this embodiment, the slit 116 is provided at only one location, but a configuration in which a plurality of slits are provided can also be adopted.

[0039] The low-strength structure shown in Fig. 4(c) is provided at least at one location along the bending portion between the wiring board main body portion 111 (the third main body portion 111C) and the holding portion 112, and is composed of a thin portion 117 that is thinner than the wiring board main body portion 111 and the holding portion 112. In Fig. 4(c), a plan view is shown on the left side, and a side view (a view seen in the arrow direction in the plan view on the left side) is shown on the right side. In this embodiment, the thin portion 117 is provided at only one location, but a configuration in which a plurality of thin portions are provided can also be adopted.

[0040] Note that it is also possible to adopt a combination of the low-intensity structures shown in FIGS. 4(a) and 4(c) and the low-intensity structures shown in FIGS. 4(b) and 4(c). Further, for each of the various low-intensity structures shown above, a configuration in which no conductor is provided at the connection portion can also be adopted as described above. As described above, by adopting the low-intensity structure, it is possible to further suppress the peeling of the folded-back portion 150. This point will be described in detail with reference to FIG. 3(b) in particular. In FIG. 3(b), the four thick lines indicate the adhesive. The spring-back force due to the second valley fold line L2 acts in the direction R1 to peel the second main body portion 111B from the spacer 120. As a result, the force acting on the adhesive between the second main body portion 111B and the holding portion 112 (the force acting in the direction of arrow S in the figure) becomes a shear stress and does not act in the direction to peel the second main body portion 111B and the holding portion 112. Further, although the spring-back force due to the third valley fold line L3 acts in the direction R2 to peel the holding portion 112 from the second main body portion 111B, as described above, by adopting the low-intensity structure, the force acting in the peeling direction R2 can be reduced. Therefore, it is possible to more reliably suppress the peeling of the folded-back portion 150. From the above, it can be understood that it is preferable that the straight line including the fold line (the third valley fold line L3 in this embodiment) for bending the holding portion 112 is located on the opposite side of the straight line including the other fold line (the second valley fold line L2 in this embodiment) across the adhesion portion of the holding portion 112 (the adhesion portion between the holding portion 112 and the second main body portion 111B in this embodiment).

[0041] (Embodiment 2) FIG. 5 shows Embodiment 2 of the present invention. In this embodiment, a configuration in which the position where the holding portion is provided is different from that in Embodiment 1 is shown in the configuration of Embodiment 1. Since the other configurations and operations are the same as those in Embodiment 1, the same reference numerals are given to the same constituent parts, and the description thereof will be omitted as appropriate.

[0042] Also in the FPC100X according to this embodiment, it includes a wiring board main body portion 111 having a folded-back portion, and a holding portion 112 that is integrally connected to the wiring board main body portion 111 and holds the portion where the wiring board main body portion 111 overlaps due to the folded-back portion. And the wiring board main body portion 111 has a circuit 110a for electrical wiring. Also, the holding portion 112 does not have a circuit for electrical wiring. However, in the holding portion 112, it is not necessarily required to be configured so as not to have a circuit. In the above-mentioned Example 1, the holding portion 112 is connected to the third main body portion 111C, whereas in this embodiment, it is different in that the holding portion 112 is connected to the second main body portion 111B.

[0043] In this embodiment, first, along the first valley fold line L4, the portion between the first main body portion 111A and the second main body portion 111B is bent. Next, along the second valley fold line L5, the portion between the second main body portion 111B and the third main body portion 111C is bent. Finally, along the third valley fold line L6, the portion between the second main body portion 111B and the holding portion 112 is bent. Then, through a pressing process, the respective parts are adhered at the folded-back portion.

[0044] With the above configuration, in this embodiment as well, the same effects as those in the above-mentioned Example 1 can be obtained. Note that also in this embodiment, as shown in the above-mentioned Example 1, various low-strength structures can be adopted at the connection portion where the wiring board main body portion 111 and the holding portion 112 are connected. Also, in this embodiment as well, a straight line including the fold line (in this embodiment, the third valley fold line L6) for folding the holding portion 112 is configured to be located on the opposite side of a straight line including another fold line (in this embodiment, the second valley fold line L5) with the adhesive portion of the holding portion 112 (in this embodiment, the adhesive portion between the holding portion 112 and the third main body portion 111C) interposed therebetween.

[0045] (Example 3) Example 3 of the present invention is shown in FIG. 6. FIG. 6 is an explanatory diagram of the folding procedure of the FPC 200 according to Example 3 of the present invention, and shows the state of the FPC 200 for each procedure in a plan view. FIG. 7 is a schematic cross-sectional view of the FPC 200 according to Example 3 of the present invention, and is a CC cross-sectional view in FIG. 6(d).

[0046] <Configuration of FPC> Regarding the basic structure of the FPC, it is as described in the above Example 1. The FPC 200 according to this example includes a wiring board main body portion 211 having a folded-back portion 250, and a holding portion 212 that is integrally connected to the wiring board main body portion 211 and holds the portion where the wiring board main body portion 211 overlaps due to the folded-back portion 250. And the wiring board main body portion 211 has a circuit 210a for electrical wiring. Also, the holding portion 212 does not have a circuit for electrical wiring. However, in the holding portion 212, it is not necessarily required to be configured not to have a circuit. In this example, the holding portions 212 are provided at two locations.

[0047] In the FPC 200 according to this example, it is folded at four bending sites. That is, in FIG. 6(a), it is folded by the first valley fold line L7, the second mountain fold line L8, and two third valley fold lines L9. For convenience, among the wiring board main body portion 211, the portions divided by two folding lines (the first valley fold line L7 and the second mountain fold line L8) are respectively referred to as the first main body portion 211A, the second main body portion 211B, and the third main body portion 211C.

[0048] 3 The C main body portion 211 C is provided with a first spacer 221 made of a foam material. , The 2 main body portion 211 B is provided with a second spacer 222 made of a foam material. (In Fig. 6(a), it is provided on the back side surface) Adhesives are applied to both sides of these spacers. Also, adhesives 231 are provided at two holding portions 212 respectively. Thereby, after the folding process, by going through the pressing process, it becomes possible to bond the folded-back portion. In this embodiment, the case of using the first spacer 221 and the second spacer 222 made of a foam material is shown, but the material of the spacer is not particularly limited.

[0049] <FPC Folding Procedure> First, along the first valley fold line L7, the portion between the second main body portion 211B and the third main body portion 211C is folded (see Fig. 6(b)). Next, along the second mountain fold line L8 (which becomes a valley fold line in Fig. 6(b)), the portion between the first main body portion 211A and the second main body portion 211B is folded (see Fig. 6(c)). Finally, along the third valley fold line L9, the portions between the third main body portion 211C and the two holding portions 212 are folded respectively (see Fig. 6(d)). Thereafter, through the pressing process, the respective portions are bonded at the folded-back portion 250.

[0050] <Advantages of the FPC According to this Embodiment> According to the FPC 200 according to this embodiment, among the portions where the wiring board main body portion 211 overlaps due to the folded-back portion 250, 1 main body portion 211 A a part of which is in a state of being sandwiched between the adjacent portion (the third main body portion 211C) adjacent to the holding portion 212 among the wiring board main body portions 2 11 and the folded-back and bonded holding portion 212.

[0051] Further, in the FPC 200 according to the present embodiment, spacers are arranged between the portions on both sides of the folded-back portion in the wiring board main body portion 211. More specifically, in the FPC 200 according to the present embodiment, it has a first folded-back portion (the portion where the first valley fold line L7 is bent) and a second folded-back portion (the portion where the second valley fold line L8 is bent). And, a first spacer 221 is arranged between the portions on both sides of the first folded-back portion in the wiring board main body portion 211, and a second spacer 222 is arranged between the portions on both sides of the second folded-back portion. By adopting the configuration of arranging the spacers in this way, the radius of curvature of the bent portion in the folded-back portion can be increased by the amount of the spacers provided. Thereby, the spring-back force acting on the folded-back portion can be relaxed. Also, disconnection of the circuit 210a for electrical wiring can be suppressed.

[0052] With the above configuration, in this embodiment as well, the same effects as those in the above-described Embodiment 1 can be obtained. In this embodiment as well, as shown in the above-described Embodiment 1, various low-strength structures can be adopted at the connection portion where the wiring board main body portion 211 and the holding portion 212 are connected. In this embodiment, the configuration in the case where the holding portion 212 is provided at two locations is shown, but the holding portion 212 can also adopt a configuration in which it is provided only at one location. Also, in this embodiment as well, a straight line including a fold line (in this embodiment, the third valley fold line L9) for folding the lower holding portion 212 in FIG. 6(a) is located on the opposite side of a straight line including another fold line (in this embodiment, the first valley fold line L7) across the adhesion portion of the holding portion 212 (in this embodiment, the adhesion portion between the holding portion 212 and the first main body portion 211A).

[0053] (Embodiment 4) FIG. 8 shows Embodiment 4 of the present invention. FIG. 8 is an explanatory diagram of the folding procedure of the FPC 300 according to Embodiment 4 of the present invention, and shows the state of the FPC 300 for each procedure in a plan view. In this embodiment, compared with the above-described embodiments, the FPC is shown even more simply, and wirings and semi-circular cutouts serving as folding marks are shown omitted.

[0054] <Configuration of FPC> Regarding the basic structure of the FPC, it is as described in the above-mentioned Example 1. The FPC 300 according to this example includes a wiring board main body portion 311 having a folded-back portion 350, and a holding portion 312 that is integrally connected to the wiring board main body portion 311 and holds the portion where the wiring board main body portion 311 overlaps due to the folded-back portion 350. And the wiring board main body portion 311 has a circuit for electrical wiring (not shown). Also, the holding portion 312 does not have a circuit for electrical wiring. However, in the holding portion 312, it is not necessarily configured not to have a circuit. In this example, the holding portions 312 are provided at two locations.

[0055] In the FPC 300 according to this example, it is folded at four bending sites. That is, in FIG. 8(a), it is bent at the first valley fold line L10, the second valley fold line L11, and two third valley fold lines L12. For convenience, among the wiring board main body portion 311, the portions divided by two folding lines (the first valley fold line L10 and the second valley fold line L11) are respectively referred to as the first main body portion 311A, the second main body portion 311B, and the third main body portion 311C.

[0056] A spacer 320 made of a foam material is provided on the second main body portion 311B. Adhesives are applied to both sides of this spacer 320. Also, an adhesive 331 is provided on the third main body portion 311C. Thereby, after the folding process, by going through a pressing process, it becomes possible to bond the folded-back portion. Further, adhesives 332 are similarly provided on the two holding portions 312 respectively. In this example, the case of using a spacer 320 made of a foam material is shown, but the material of the spacer 320 is not particularly limited.

[0057] <Folding Procedure of FPC> First, along the first valley fold line L10, the portion between the first main body portion 311A and the second main body portion 311B is bent (see Fig. 8(b)). Next, along the second valley fold line L11, the portion between the second main body portion 311B and the third main body portion 311C is bent (see Fig. 8(c)). Finally, along the third valley fold line L12 (which becomes a mountain fold line in Fig. 8(c)), the portions between the second main body portion 311B and the two holding portions 312 are bent respectively (see Fig. 8(d)). Then, through a pressing process, each part is adhered at the folded-back portion 350.

[0058] <Advantages of the FPC according to this embodiment> According to the FPC 300 according to this embodiment, a part of the first main body portion 311A and the third main body portion 311C among the portions where the wiring board main body portion 311 overlaps due to the folded-back portion 350 is sandwiched between the adjacent portion (the second main body portion 311B) adjacent to the holding portion 312 in the wiring board main body portion 311 and the folded-back and adhered holding portion 312.

[0059] Also, in the FPC 300 according to this embodiment, a spacer 320 is disposed between the portions on both sides of the folded-back portion in the wiring board main body portion 311. More specifically, in the FPC 300 according to this embodiment, it has a first folded-back portion (the portion where the first valley fold line L10 is bent) and a second folded-back portion (the portion where the second valley fold line L11 is bent). And a single spacer 320 is disposed between the portions on both sides of the first folded-back portion in the wiring board main body portion 311 and between the portions on both sides of the second folded-back portion. By adopting such a configuration of disposing the spacer 320, the radius of curvature of the bent portion in the folded-back portion can be increased by the amount of the spacer 320 provided. Also, disconnection of the circuit for electrical wiring can be suppressed.

[0060] With the above configuration, in this embodiment as well, the same effects as those in the above-described Embodiment 1 can be obtained. Note that, also in this embodiment, as shown in the above-described Embodiment 1, various low-strength structures can be adopted at the connection portion where the wiring board main body portion 311 and the holding portion 312 are connected. Further, in this embodiment, the configuration in the case where the holding portion 312 is provided at two locations is shown, but the holding portion 312 can also adopt a configuration in which it is provided at only one location. Also, in this embodiment as well, a straight line including a bending line (in this embodiment, the third valley fold line L12) for bending the upper holding portion 312 in FIG. 8(a) is configured to be located on the opposite side of a straight line including another bending line (in this embodiment, the second valley fold line L11) across the adhesion portion of the holding portion 312 (in this embodiment, the adhesion portion between the holding portion 312 and the third main body portion 311C).

[0061] (Embodiment 5) FIG. 9 shows Embodiment 5 of the present invention. FIG. 9 is an explanatory diagram of the bending procedure of the FPC 400 according to Embodiment 5 of the present invention, and shows the state of the FPC 400 for each procedure in a plan view. Note that, in this embodiment, compared with the above-described Embodiments 1 to 3, the FPC is shown even more simply, and wirings and semicircular notches serving as bending marks are shown omitted.

[0062] <Configuration of FPC> Regarding the basic structure of the FPC, it is as described in the above-described Embodiment 1. The FPC 400 according to this embodiment includes a wiring board main body portion 411 having a folded-back portion 450, and a holding portion 412 that is integrally connected to the wiring board main body portion 411 and holds the portion where the wiring board main body portion 411 overlaps due to the folded-back portion 450. And the wiring board main body portion 411 has a circuit (not shown) for electrical wiring. Also, the holding portion 412 does not have a circuit for electrical wiring. However, in the holding portion 412, it is not necessarily required to be configured not to have a circuit.

[0063] In the FPC400 according to this embodiment, it is folded back at three bending portions. That is, in FIG. 9(a), it is bent along the first valley fold line L13, the second valley fold line L14, and the third valley fold line L15. For convenience, among the wiring board main body portions 411, the portions divided by two folding lines (the first valley fold line L13 and the second valley fold line L14) are respectively referred to as the first main body portion 411A, the second main body portion 411B, and the third main body portion 411C.

[0064] In each of the above embodiments, the first main body portion and the second main body portion are provided continuously and linearly, and the third main body portion is provided parallel and linearly with respect to these first and second main body portions. In contrast, in this embodiment, the first main body portion 411A and the second main body portion 411B are provided continuously and linearly, and the third main body portion 411C is provided perpendicular and linearly with respect to these first main body portion 411A and second main body portion 411B.

[0065] And a spacer 420 made of a foam material is provided on the second main body portion 411B. Adhesives are applied to both surfaces of this spacer 420. Also, an adhesive 431 is provided on the third main body portion 411C. Thereby, after the folding process, by going through a pressing process, it becomes possible to bond the folded-back portion. Further, hold An adhesive 432 is also provided on the portion 412 in the same manner. In this embodiment, the case of using the spacer 420 made of a foam material is shown, but the material of the spacer 420 is not particularly limited.

[0066] <Folding Procedure of FPC> First, along the first valley fold line L13, the portion between the first main body portion 411A and the second main body portion 411B is bent (see Fig. 9(b)). In each of the above embodiments, the fold lines were perpendicular to the direction in which each main body portion extends, whereas this first valley fold line L13 (fold line) is inclined at 45° with respect to the direction in which the first main body portion 411A and the second main body portion 411B extend. Next, along the second valley fold line L14, the portion between the second main body portion 411B and the third main body portion 411C is bent (see Fig. 9(c)). Finally, along the third valley fold line L15, the portion between the third main body portion 411C and the holding portion 412 is bent (see Fig. 9(d)). Thereafter, through a pressing process, the respective portions are adhered at the folded-back portion 450.

[0067] <Advantages of the FPC according to this embodiment> According to the FPC400 according to this embodiment, a part of the first main body portion 411A and the second main body portion 411B among the portions where the wiring board main body portion 411 overlaps due to the folded-back portion 450 is sandwiched between the adjacent portion (third main body portion 411C) adjacent to the holding portion 412 in the wiring board main body portion 411 and the folded-back and adhered holding portion 412.

[0068] Also, in the FPC400 according to this embodiment, a spacer 420 is disposed between the portions on both sides of the folded-back portion of the wiring board main body portion 411. More specifically, in the FPC400 according to this embodiment, it has a first folded-back portion (the portion where the first valley fold line L13 is bent) and a second folded-back portion (the portion where the second valley fold line L14 is bent). And a single spacer 420 is disposed between the portions on both sides of the first folded-back portion and between the portions on both sides of the second folded-back portion of the wiring board main body portion 411. By adopting such a configuration of disposing the spacer 420, the radius of curvature of the bent portion in the folded-back portion can be increased by the amount of the spacer 420 provided. Also, disconnection of the circuit for electrical wiring can be suppressed.

[0069] With the above configuration, in this embodiment as well, the same effects as those in the above-described Embodiment 1 can be obtained. Note that, also in this embodiment, as shown in the above-described Embodiment 1, various low-strength structures can be adopted at the connection portion where the wiring board main body portion 411 and the holding portion 412 are connected. Further, also in this embodiment, a straight line including a bending line (in this embodiment, the third valley folding line L15) for bending the holding portion 412 in FIG. 9(a) is located on the opposite side of a straight line including another bending line (in this embodiment, the second valley folding line L14) with the adhesive portion of the holding portion 412 (in this embodiment, the adhesive portion between the holding portion 412, the second main body portion 411B, and the third main body portion 411C) interposed therebetween.

[0070] (Embodiment 6) Examples 6 of the present invention are shown in FIGS. 10 and 11. FIGS. 10 and 11 are explanatory views of the folding procedure of the FPC 500 according to Example 6 of the present invention, and show the state of the FPC 500 for each procedure in a plan view. Note that, in this embodiment, compared with the above-described Embodiments 1 to 3, the FPC is shown even more simply, and wirings, semicircular notches serving as folding marks, and the like are shown in an omitted manner.

[0071] <Configuration of FPC> Regarding the basic structure of the FPC, it is as described in the above-described Embodiment 1. The FPC 500 according to this embodiment includes a wiring board main body portion 511 having a folded-back portion 550, and a holding portion 512 that is integrally connected to the wiring board main body portion 511 and holds a portion where the wiring board main body portion 511 overlaps due to the folded-back portion 550. The wiring board main body portion 511 has a circuit for electrical wiring (not shown). The holding portion 512 does not have a circuit for electrical wiring. However, in the holding portion 512, it is not necessarily required to be configured not to have a circuit. In this embodiment, the holding portions 512 are provided at four locations.

[0072] In the FPC500 according to this embodiment, it is folded back at 12 folding sites. That is, in FIG. 10(a), it is folded at four first valley fold lines L16, four second valley fold lines L17, and four third valley fold lines L18. For convenience, among the wiring board main body portions 511, the portions divided by the four first valley fold lines L1 6 and the four second valley fold lines L1 7 are respectively referred to as a first main body portion 511A (one place), a second main body portion 511B (four places), and a third main body portion 511C (four places).

[0073] Spacers 520 made of a foam material are respectively provided on the four second main body portions 511B. Adhesives are applied to both sides of this spacer 520. Also, in the first main body portion 511A, adhesives 531 are respectively provided in the vicinity adjacent to the four second main body portions 511B. Further, adhesives 532 are also respectively provided on the four holding portions 512. In this embodiment, the case of using a spacer 520 made of a foam material is shown, but the material of the spacer 520 is not particularly limited.

[0074] <Folding procedure of FPC> First, along the four first valley fold lines L16, the portions between the third main body portion 511C and the second main body portion 511B are respectively folded (see FIG. 10(b)). Next, along the four second valley fold lines L17, the portions between the second main body portion 511B and the first main body 5 11A are respectively folded (see FIG. 11(a)). Finally, along the four third valley fold lines L18 (which become mountain fold lines in FIG. 11(a)), the portions between the second main body portion 511B and the holding portion 512 are respectively folded (see FIG. 11(b)). Then, through a pressing process, at the four folded-back portions 5 50, each part is adhered.

[0075] <Excellent points of the FPC according to this embodiment> According to the FPC500 according to this embodiment, a part of the first main body part 511A and the third main body part 511C among the overlapping parts of the wiring board main body part 511 by the folded-back part 550 are adjacent to the holding part 512 among the wiring board main body parts 511. It is sandwiched between the adjacent part (second main body part 511B) and the folded-back and adhered holding part 512.

[0076] Further, in the FPC500 according to this embodiment, a spacer 520 is disposed between the portions on both sides of the folded-back portion of the wiring board main body part 511. More specifically, in the FPC500 according to this embodiment, it has a first folded-back portion (a portion obtained by bending the first valley fold line L16) and a second folded-back portion (a portion obtained by bending the second valley fold line L17). And a single spacer 520 is disposed between the portions on both sides of the first folded-back portion of the wiring board main body part 511 and between the portions on both sides of the second folded-back portion. By adopting the configuration of disposing the spacer 520 in this way, the radius of curvature of the bent portion in the folded-back portion can be increased by the amount of the spacer 520 provided. Also, disconnection of the circuit for electrical wiring can be suppressed.

[0077] With the above configuration, in this embodiment as well, the same effects as those in the above-described Embodiment 1 can be obtained. Note that, also in this embodiment, as shown in the above-described Embodiment 1, various low-strength structures can be adopted at the connection portion where the wiring board main body part 511 and the holding part 512 are connected. Also, in this embodiment as well, a straight line including the fold line (the third valley fold line L18 in this embodiment) for folding the holding part 512 sandwiches the adhesion part of the holding part 512 (the adhesion part between the holding part 512 and the first main body part 511A in this embodiment), and is configured to be located on the opposite side of a straight line including another fold line (the second valley fold line L17 in this embodiment).

Explanation of Reference Numerals

[0078] 100, 100X, 200, 300, 400, 500 FPC 110a, 210a Circuit 111, 211, 311, 411, 511 Wiring Board Main Body Part 111A, 211A, 311A, 411A, 511A First body part 111B, 211B, 311B, 411B, 511B Second body part 111C, 211C, 311C, 411C, 511C Third body part 112, 212, 312, 412, 512 Holding part 115 Through-hole 116 Slit 116a Through-hole 117 Thin-walled part 120, 320, 420, 520 Spacer 221 First spacer 222 Second spacer 131, 132, 231, 331, 332, 431, 432, 531, 532 Adhesive 150, 250, 350, 450, 550 Folded-back part

Claims

1. A wiring board main body having a folded-back portion, a holding portion integrally connected to the wiring board main body and for holding a portion where the wiring board main body overlaps due to the folded-back portion, comprising: the wiring board main body has a circuit for electrical wiring, and the holding portion does not have a circuit for electrical wiring, at least a part of the portion where the wiring board main body overlaps due to the folded-back portion is sandwiched between an adjacent portion adjacent to the holding portion in the wiring board main body, the folded-back and adhesively bonded by an adhesive, and the holding portion in a flat state, a flexible printed wiring board characterized by being in a sandwiched state.

2. A spacer is disposed between portions on both sides of the folded-back portion of the wiring board main body, the flexible printed wiring board according to claim 1, characterized in that.

3. The folded-back portion has a first folded-back portion and a second folded-back portion, a single spacer is disposed between portions on both sides of the first folded-back portion of the wiring board main body and between portions on both sides of the second folded-back portion, the flexible printed wiring board according to claim 1, characterized in that.

4. The folded-back portion has a first folded-back portion and a second folded-back portion, a first spacer is disposed between portions on both sides of the first folded-back portion of the wiring board main body, a second spacer is disposed between portions on both sides of the second folded-back portion of the wiring board main body, the flexible printed wiring board according to claim 1, characterized in that.

5. The bending site between the wiring board main body and the holding portion has a low-strength structure with a lower bending strength than the bending site in the wiring board main body, the flexible printed wiring board according to any one of claims 1 to 4, characterized in that.

6. The low-strength structure is constituted by at least one through hole provided along the bending site between the wiring board main body and the holding portion, the flexible printed wiring board according to claim 5, characterized in that.

7. The low-strength structure is constituted by at least one slit provided along the bending site between the wiring board main body and the holding portion, the flexible printed wiring board according to claim 5, characterized in that.

8. The low-strength structure is provided at least at one location along the bending portion between the wiring board main body portion and the holding portion, and is composed of a thin-walled portion that is thinner than the wiring board main body portion and the holding portion. The flexible printed wiring board according to claim 5, characterized in that.

9. The straight line including the bending line for bending the holding portion is configured to be located on the opposite side of the straight line including the other bending line in the wiring board main body portion with respect to the adhesive portion of the holding portion. The flexible printed wiring board according to any one of claims 1 to 8, characterized in that.

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