CN115119384A - Flexible printed wiring board - Google Patents

Abstract

The invention provides a flexible printed wiring board capable of stably holding a folded portion. The flexible printed wiring board includes: a wiring board main body (111) including a folded-back section (150); and a holding section (112) that is integrally connected to the wiring board main body section (111) and that holds the portion of the wiring board main body section (111) that is overlapped by the folded-back section (150), at least a part of the portion of the wiring board main body section (111) that is overlapped by the folded-back section (150) being sandwiched by an adjacent portion of the wiring board main body section (111) that is adjacent to the holding section (112) by the folded-back section and the holding section (112) that is bonded by an adhesive.

Description

Flexible printed wiring board

Technical Field

The present invention relates to a flexible printed wiring board.

Background

It is known to use a flexible printed wiring board provided with a folded-back portion. In general, a flexible printed wiring board (hereinafter referred to as "FPC") is obtained by cutting a sheet-like material (intermediate product) composed of a film and a wiring (a conductor such as a copper foil) formed on the film by etching. However, for example, when the FPC is intended to be lengthened or the amount of waste remaining after a plurality of FPCs are taken out from a sheet-like material by cutting is intended to be reduced, the FPC having a folded-back portion is used.

In this case, due to the springback, a force to return the FPC to the original state acts on the portion of the flexible printed wiring board overlapped by the folded portion. Therefore, the folded-back portion is held by bonding the overlapped portion with an adhesive.

However, in the case of transportation, use, or the like, the adhesive force is reduced as a result of vibration action, impact, change in the adhesive with time, or change in the environment, and therefore, there is a possibility that the folded portion bonded with the adhesive is peeled off. Particularly, when a part of the folded portion is peeled from the vicinity of the corner portion, the peeling is gradually increased.

Documents of the prior art

Patent document 1: japanese patent laid-open publication No. Hei 1-257389

Patent document 2: japanese patent publication No. 6197925

Disclosure of Invention

The invention aims to provide a flexible printed wiring board capable of stably keeping a folding part.

In order to solve the above problems, the present invention adopts the following means.

That is, the flexible printed wiring board of the present invention includes a wiring board main body portion and a holding portion, the wiring board main body portion includes a folded portion and an adjacent portion integrally connected to the holding portion by the folded portion, and at least a part of a portion of the wiring board main body portion overlapped by the folded portion is sandwiched by the adjacent portion and the holding portion bonded by an adhesive.

The flexible printed wiring board of the present invention is provided with the holding portion configured as described above. In this way, the folded portion can be suppressed from peeling.

The wiring board main body has a circuit for electrical wiring. The holding portion may not have a circuit for electrical wiring.

The wiring board main body portion is generally provided with an electric wiring circuit made of a conductor such as a copper foil. Therefore, the folded portion of the wiring board main body has high rigidity. As a result, it becomes difficult to fold the wiring board main body. In contrast, since a circuit does not need to be provided in the holding portion, the degree of freedom in design is high. For example, a conductor need not be provided at the folded portion between the wiring board main body portion and the holding portion. Therefore, the folded-back portion has low rigidity. As a result, the wiring board main body is easily folded. However, in the present invention, it is not excluded to provide a conductor at the above-described folded portion.

A spacer may be disposed between two portions of the wiring board main body portion overlapped by the turn-back portion.

In addition, the turn-back portion may include a first turn-back portion and a second turn-back portion. In this case it is preferred that: the single spacer is disposed between the two portions of the wiring board main body portion overlapped by the first folded portion and also disposed between the two portions of the wiring board main body portion overlapped by the second folded portion.

Or preferably: the first spacer is disposed between the two portions of the wiring board main body portion overlapped by the first folded portion, and the second spacer is disposed between the two portions of the wiring board main body portion overlapped by the second folded portion.

By adopting the configuration including the spacers thus arranged, the radius of curvature of the folded-back portion can be increased only by the portion where the spacers are provided.

Preferably, a folded portion between the wiring board main body portion and the holding portion has a low-strength structure having a lower bending strength than other folded portions.

This makes it possible to easily fold back the holding portion. Further, the repulsive force at the time of bending can be suppressed.

Preferably, the low-strength structure is constituted by at least one through hole provided along a folded portion between the wiring board main body portion and the holding portion.

Further preferably, the low-strength structure is constituted by at least one slit provided along a folded portion between the wiring board main body portion and the holding portion.

Further, it is preferable that the low-strength structure is constituted by a thin-walled portion which is provided at least at one location along a folded portion between the wiring board main body portion and the holding portion and has a thickness thinner than the wiring board main body portion and the holding portion.

Further, it is preferable that: a straight line including a bending line for folding back the holding section is located at a position on the opposite side of a straight line including the other bending line of the wiring board main body section with respect to the bonding section of the holding section.

Further, the above-described configurations may be combined as much as possible.

Effects of the invention

As described above, according to the present invention, the folded portion of the flexible printed wiring board can be stably held.

Drawings

Fig. 1 is a plan view showing a state before folding back the flexible printed wiring board according to embodiment 1 of the present invention.

Fig. 2 is an explanatory view of a bending step of the flexible printed wiring board of embodiment 1 of the present invention.

Fig. 3 is a schematic cross-sectional view of a flexible printed wiring board of embodiment 1 of the present invention.

Fig. 4 is a diagram showing an example of a low-strength structure according to an embodiment of the present invention.

Fig. 5 is a plan view showing a state before the flexible printed wiring board of embodiment 2 of the present invention is folded.

Fig. 6 is an explanatory view of a bending step of the flexible printed wiring board of embodiment 3 of the present invention.

Fig. 7 is a schematic cross-sectional view of a flexible printed wiring board of embodiment 3 of the present invention.

Fig. 8 is an explanatory view of a bending step of the flexible printed wiring board of embodiment 4 of the present invention.

Fig. 9 is an explanatory view of a bending step of the flexible printed wiring board of embodiment 5 of the present invention.

Fig. 10 is an explanatory view of a bending step of the flexible printed wiring board of embodiment 6 of the present invention.

Fig. 11 is an explanatory view of a bending step of the flexible printed wiring board of embodiment 6 of the present invention.

Description of the reference numerals

100、100X、200、300、400、500FPC

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 portion

111C, 211C, 311C, 411C, 511C third body section

112. 212, 312, 412, 512 holder

115 through hole

116 gap

116a through hole

117 thin wall part

120. 320, 420, 520 spacers

221 first spacer

222 second spacer

131. 132, 231, 331, 332, 431, 432, 531, 532 adhesive

150. 250, 350, 450, 550 turn-back part

Detailed Description

The mode for carrying out the invention will be described in detail below exemplarily based on embodiments with reference to the accompanying drawings. However, unless otherwise specifically stated, the sizes, materials, shapes, relative arrangements thereof, and the like of the constituent members described in the embodiments do not limit the scope of the present invention only to these sizes, materials, shapes, or relative arrangements thereof. Hereinafter, when the wiring board main body or the holding portion is folded along a folding line so as to face the front side of the drawing, the folding line is referred to as a "valley folding line". On the other hand, when the wiring board body or the holding section is folded back along a bending line so as to face the depth side of the drawing, the bending line is referred to as a "mountain folding line". The flexible printed wiring board (hereinafter referred to as "FPC") according to the present embodiment is suitably used, for example, in an FPC bus bar module for voltage monitoring of a battery cell mounted on an automobile. In the following embodiments, the folded portion is formed by folding the bending portion along the bending lines to fold back the wiring board main body or the holding portion. In the following description, the term "adhesive" means a substance having adhesiveness at normal temperature and capable of adhering to an adherend with light pressure. As an example of a specific adhesive, a pressure sensitive adhesive can be exemplified.

(example 1)

An FPC100 according to embodiment 1 of the present invention will be described with reference to fig. 1 to 3. Fig. 1 is a plan view showing a state before the FPC100 of embodiment 1 of the present invention is folded. Fig. 2 is an explanatory view of the bending step of the FPC100 according to embodiment 1 of the present invention, and the state of the FPC100 at each step is shown in a plan view. Fig. 3 is a schematic cross-sectional view of FPC100 according to embodiment 1 of the present invention. Fig. 3 (a) is an AA sectional view in fig. 2 (c). Fig. 3 (b) is a BB cross-sectional view in fig. 2 (c).

< construction of FPC >

The basic structure of the FPC is a well-known technique. Therefore, a detailed description thereof will be omitted. In general, the FPC includes, for example, a base film, a wiring provided over the base film, and a cover film covering the wiring. The wiring is formed by etching a conductor such as a copper foil. In fig. 1 to 3, the wiring (circuit 110a) provided inside the FPC100 of the present embodiment is schematically shown by a broken line.

The FPC100 of the present embodiment includes: a wiring board main body 111 including a turn-back portion 150; and a holding portion 112 integrally connected to the wiring board main body portion 111. The holding section 112 holds the portion of the wiring board main body section 111 overlapped by the folded portion 150. The wiring board main body 111 has an electric circuit 110a for electric wiring. The holding portion 112 does not have an electric circuit for electric wiring. However, the holding portion 112 does not necessarily have to have a structure including no circuit.

In the FPC100 of the present embodiment, the wiring board main body portion 111 includes three folded portions. That is, in fig. 2 (c), the wiring board main body portion 111 or the holding portion 112 is folded back along the first valley folding line L1, the second valley folding line L2, and the third valley folding line L3 in fig. 1. For convenience, the portions of the wiring board main body 111 divided by the two bending lines (the first valley folding line L1 and the second valley folding line L2) are referred to as a first main body 111A, a second main body 111B, and a third main body 111C, respectively.

The second body portion 111B is provided with a spacer 120 made of a foam material. An adhesive is coated on both sides of the spacer 120. In addition, an adhesive 131 is provided in the third body portion 111C. Thus, after the bending step, the respective portions of the wiring board main body 111 overlapped by the folded portion can be bonded by passing through the pressing step. The adhesive 132 is similarly provided in the holding portion 112. In addition, in the present embodiment, the spacer 120 composed of a foam material is used. However, the material of the spacer 120 is not particularly limited.

< step of turning back FPC >

First, the bent portion between the first body portion 111A and the second body portion 111B is bent along the first valley folding line L1 (see fig. 2 (a)). Next, the bent portion between the second body portion 111B and the third body portion 111C is bent along the second valley folding line L2 (see fig. 2 (B)). Finally, the bent portion between the third body portion 111C and the holding portion 112 is bent along the third valley folding line L3 (see fig. 2C). Thereafter, the respective portions of the wiring board main body portion overlapped by the folded portion 150 are bonded by applying pressure at normal temperature (pressing step).

< advantages of FPC of the present embodiment >

According to the FPC100 of the present embodiment, a part of the first main body portion 111A and the second main body portion 111B in the portion of the wiring board main body portion 111 where the folded portion 150 is overlapped is sandwiched by an adjacent portion (the third main body portion 111C) adjacent to the holding portion 112 in the wiring board main body portion 111 and the holding portion 112 integrally connected to the adjacent portion and bonded by an adhesive (see fig. 3).

This can suppress the peeling of the wiring board main body 111 portion overlapped by the folded portion 150. Therefore, the folded-back portion 150 can be stably held. Here, the holding portion 112 does not need to be provided with a circuit. Further, it is not necessary to provide a conductor such as a copper foil at the folded portion between the wiring board main body 111 and the holding portion 112. Therefore, if a configuration is adopted in which no conductor is provided in the folded portion, the holding portion 112 can be easily folded. However, the configuration in which the conductor is provided in the folded portion is not necessarily excluded.

In addition, in the FPC100 of the present embodiment, the spacer 120 is disposed between two portions of the wiring board main body portion 111 overlapped by the folded portion 150. More specifically, the folded-back portion of the FPC100 of the present embodiment includes a first folded-back portion (a portion folded back along the first valley folding line L1) and a second folded-back portion (a portion folded back along the second valley folding line L2). The single spacer 120 is disposed between the two portions of the wiring board main body 111 overlapped by the first folded portion, and is also disposed between the two portions of the wiring board main body 111 overlapped by the second folded portion (see fig. 3). By adopting a configuration including the spacers 120 arranged in this way, the radius of curvature of the folded portion can be increased only by the portion where the spacers 120 are provided. This can alleviate the repulsive force acting on the folded portion. In addition, disconnection of the electric wiring circuit 110a can be suppressed.

In the present embodiment, semicircular notches are provided on both sides of the bending line included in each bending portion to facilitate recognition of the position of the bending portion (see fig. 1 and 2). However, other configurations may be adopted as the mark of the bent portion. For example, the FPC100 can see a copper foil or the like through the cover film. Therefore, the mark may be provided by devising the shape of the copper foil.

< Low Strength Structure >

The bending portion between the wiring board main body 111 and the holding portion 112 is easily bent, and has a reduced repulsive force. Therefore, it is preferable that the bent portion has a low-strength structure having a lower bending strength than the bent portion of the wiring board main body 111. An example of the low-strength structure will be described below with reference to fig. 4. Fig. 4 is a diagram showing an example of a low-strength structure according to an embodiment of the present invention.

The low-strength structure shown in fig. 4 (a) is configured by a plurality of through holes 115 provided along the bent portion between the wiring board main body portion 111 (third main body portion 111C) and the holding portion 112. In the illustrated example, a plurality of through holes 115 are provided. However, as shown by a broken line in the figure, a configuration including only one through-hole 115a may be adopted.

The low-strength structure shown in fig. 4 (b) is constituted by at least one slit (slit) 116 provided along the bending portion between the wiring board main body portion 111 (third main body portion 111C) and the holding portion 112. In addition, in this embodiment, through holes 116a are provided at both ends of the slit 116, respectively. This can prevent the tear from spreading from both ends of the slit 116. In addition, in this embodiment, the slit 116 is provided only at one location. However, a configuration including a plurality of slits may be adopted.

The low-strength structure shown in fig. 4 (C) is constituted by a thin portion 117 provided at least at one location along the bent portion between the wiring board main body portion 111 (third main body portion 111C) and the holding portion 112 and having a thickness thinner than the wiring board main body portion 111 and the holding portion 112. In fig. 4 (c), the left side shows a plan view, and the right side shows a side view (a view seen in the arrow direction in the left side plan view). In this embodiment, the thin-walled portion 117 is provided only at one location. However, a configuration including a plurality of thin wall portions may also be adopted.

The low-strength structure shown in fig. 4 (a) and 4 (c) and the low-strength structure shown in fig. 4 (b) and 4 (c) may be used in combination. In addition, as described above, the various low-strength structures described above may be configured such that no conductor is provided at the bent portion. As described above, by adopting the low-strength structure, peeling of the portion of the wiring board main body portion 111 overlapped by the folded portion 150 can be further suppressed. This point will be described in detail with reference to (b) of fig. 3. In fig. 3 (b), four thick lines indicate an adhesive. The return force generated by the folded portion including the second valley folding line L2 acts in the direction R1 in which the second main body portion 111B is peeled from the spacer 120. Thus, a force (a force acting in the direction of arrow S in the drawing) acting on the adhesive between the second body portion 111B and the holding portion 112 becomes a shear stress, and does not act in a direction of peeling apart the second body portion 111B and the holding portion 112. Further, although the repulsive force generated by the folded portion including the third valley folding line L3 acts in the direction R2 in which the holding portion 112 is peeled from the second main body portion 111B, the force acting in the peeling direction R2 can be reduced by adopting the low-strength structure as described above. Therefore, peeling of the portion of the wiring board main body portion overlapped by the folded portion 150 can be more reliably suppressed. From this, it is sufficient that a straight line including a bending line (third valley folding line L3 in this embodiment) for folding back the holding section 112 is positioned on the opposite side of a straight line including the other bending line (second valley folding line L2 in this embodiment) of the wiring board main body section 111 from the bonding portion (bonding portion between the holding section 112 and the second main body section 111B in this embodiment) of the holding section 112.

(example 2)

Embodiment 2 of the present invention is shown in fig. 5. In this embodiment, a configuration in which the positions where the holding portions are provided are different in the configuration of embodiment 1 is described. Other configurations and operations are the same as those in embodiment 1. Therefore, the same components are given the same reference numerals, and the description thereof is appropriately omitted.

The FPC100X of the present embodiment also includes a wiring board main body 111 including a folded portion and a holding portion 112 integrally connected to the wiring board main body 111. The holding section 112 holds the portion of the wiring board main body section 111 overlapped by the folded portion. The wiring board main body 111 has an electric circuit 110a for electric wiring. The holding portion 112 does not have an electric circuit for electric wiring. However, the holding portion 112 does not necessarily have to have a structure including no circuit. In embodiment 1 described above, the holding portion 112 is integrally connected to the third main body portion 111C. In the present embodiment, the holding portion 112 is integrally connected to the second body portion 111B. The present embodiment is different from embodiment 1 described above in this point.

In the present embodiment, first, the bent portion between the first and second main body portions 111A and 111B is bent along the first valley folding line L4. Next, the bent portion between the second main body portion 111B and the third main body portion 111C is bent along the second valley folding line L5. Finally, the bent portion between the second body portion 111B and the holding portion 112 is bent along the third valley folding line L6. Thereafter, the respective portions of the wiring board main body portion overlapped by the folded portion are bonded by passing through a pressing process.

With the above-described configuration, the same effects as those of embodiment 1 can be obtained also in this embodiment. In addition, even in the present embodiment, various low-strength structures can be adopted in the folded-back portion between the wiring board main body portion 111 and the holding portion 112 as shown in the above-described embodiment 1. In addition, even in the configuration of the present embodiment, a straight line including a bending line for folding back the holding section 112 (third valley folding line L6 in the present embodiment) is located at a position on the opposite side of a straight line including the other bending line of the wiring board main body section 111 (second valley folding line L5 in the present embodiment) across the bonded portion of the holding section 112 (bonded portion of the holding section 112 and the third main body section 111C in the present embodiment).

(example 3)

Embodiment 3 of the present invention is shown in fig. 6. Fig. 6 is an explanatory view of a bending step of the FPC200 according to embodiment 3 of the present invention. The states of the FPC200 at the respective steps are shown in a plan view. Fig. 7 is a schematic cross-sectional view of FPC200 of embodiment 3 of the present invention. More specifically, fig. 7 is a CC sectional view in (d) of fig. 6.

< construction of FPC >

The basic structure of the FPC is as described in embodiment 1 above. The FPC200 of the present embodiment includes a wiring board main body portion 211 including a folded portion 250, and a holding portion 212 integrally connected to the wiring board main body portion 211. The holding section 212 holds the wiring board main body 211 portion overlapped by the folded-back portion 250. The wiring board body 211 also has an electric wiring circuit 210 a. The holding portion 212 does not have an electric circuit for electric wiring. However, the holding portion 212 does not necessarily have to have a structure including no circuit. In the present embodiment, the holding portions 212 are provided at two locations.

In the FPC200 of the present embodiment, the wiring board main body portion 211 includes four folded-back portions. That is, in fig. 6 (d), the wiring board main body portion 211 or the holding portion 212 is folded back along the first valley folding line L7, the second valley folding line L8, and the two third valley folding lines L9 in fig. 6 (a). For convenience, the portions of the wiring board main body portion 211 that are separated by two bending lines (the first valley folding line L7 and the second peak folding line L8) are referred to as a first main body portion 211A, a second main body portion 211B, and a third main body portion 211C, respectively.

In fig. 6 (a), a first spacer 221 composed of a foam material is provided at the third body portion 211C. A second spacer 222 made of a foam material is provided on the surface on the back side of the second body portion 211B. Adhesive is applied to both sides of these spacers. In addition, the holding portions 212 at the two locations are provided with adhesives 231, respectively. Thus, after the bending step, the respective portions of the wiring board main body 211 overlapped by the folded portion can be bonded by the pressing step. In this embodiment, the first spacer 221 and the second spacer 222 are made of a foam material. However, the material of the spacer is not particularly limited.

< step of folding back FPC >

First, the bent portion between the second body portion 211B and the third body portion 211C is bent along the first valley folding line L7 (see fig. 6 (B)). Next, the bent portion between the first body portion 211A and the second body portion 211B is bent along a second mountain folding line L8 (a valley folding line in fig. 6B) (see fig. 6 c). Finally, the bent portions between the third body portion 211C and the two holding portions 212 are bent along the third valley folding line L9 (see fig. 6 (d)). Thereafter, the respective portions of the wiring board main body 211 overlapped by the folded-back portion 250 are bonded by going through a pressing process.

< advantages of FPC of the present embodiment >

According to the FPC200 of the present embodiment, a part of the first main body portion 211A in the portion of the wiring board main body portion 211 overlapped by the folded-back portion 250 is sandwiched by an adjacent portion (third main body portion 211C) adjacent to the holding portion 212 in the wiring board main body portion 211 and the holding portion 212 integrally connected to the adjacent portion and bonded by an adhesive.

In addition, in the FPC200 of the present embodiment, the spacer is arranged between two portions of the wiring board main body portion 211 overlapped by the folded-back portion. More specifically, the folded-back portion of the FPC200 of the present embodiment includes a first folded-back portion (a portion folded back along the first valley folding line L7) and a second folded-back portion (a portion folded back along the second valley folding line L8). Further, the first spacer 221 is disposed between two portions of the wiring board main body portion 211 overlapped by the first turn portion. On the other hand, the second spacer 222 is disposed between two portions of the wiring board main body portion 211 overlapped by the second folded portion. By adopting the configuration including the spacers thus arranged, the radius of curvature of the folded-back portion can be increased only by the portion where the spacers are provided. This can alleviate the repulsive force acting on the folded portion. In addition, disconnection of the electrical wiring circuit 210a can be suppressed.

With the above configuration, the same effects as those of embodiment 1 can be obtained in this embodiment. In addition, even in the present embodiment, as shown in embodiment 1 described above, various low-strength structures can be adopted at the folded-back portion between the wiring board main body portion 211 and the holding portion 212. In the present embodiment, a configuration including the holding portion 212 provided at two locations is shown. However, a configuration including the holding portion 212 provided only at one location may be adopted. In addition, even in the configuration of the present embodiment, a straight line including a bending line (the third valley folding line L9 in the present embodiment) for folding back the lower holding portion 212 in (a) of fig. 6 is located at a position on the opposite side of a straight line including the other bending line (the first valley folding line L7 in the present embodiment) of the wiring board main body portion 211 across the bonding portion (the bonding portion of the holding portion 212 and the first main body portion 211A in the present embodiment) of the holding portion 212.

(example 4)

Embodiment 4 of the present invention is shown in fig. 8. Fig. 8 is an explanatory diagram of a bending step of the FPC300 of embodiment 4 of the present invention. The states of the FPC300 at the respective steps are shown in a plan view. In this embodiment, the FPC is further simplified as compared with the above embodiments. Therefore, the wiring, the semicircular notch as a mark for bending, and the like are omitted.

< construction of FPC >

The basic structure of the FPC is as described in embodiment 1 above. The FPC300 of the present embodiment includes a wiring board main body portion 311 including a folded portion 350 and a holding portion 312 integrally connected to the wiring board main body portion 311. The holding section 312 holds the portion of the wiring board main body portion 311 overlapped by the folded portion 350. The wiring board body 311 also has an electric circuit (not shown) for electric wiring. The holding portion 312 does not have an electric circuit for electric wiring. However, the holding portion 312 does not necessarily have to have a structure including no circuit. In the present embodiment, the holding portions 312 are provided at two locations.

In the FPC300 of the present embodiment, the wiring board main body portion 311 includes four-part turn-back portions. That is, in fig. 8 (d), the wiring board main body portion 311 or the holding portion 312 is folded back along the first valley folding line L10, the second valley folding line L11, and the two-part third valley folding line L12 in fig. 8 (a). For convenience, the portions of the wiring board main body portion 311 that are separated by two fold lines (the first valley fold line L10 and the second valley fold line L11) are referred to as a first main body portion 311A, a second main body portion 311B, and a third main body portion 311C, respectively.

The second body portion 311B is provided with a spacer 320 made of a foam material. An adhesive is coated on both sides of the spacer 320. In addition, an adhesive 331 is provided in the third body portion 311C. Thus, after the bending step, the respective portions of the wiring board main body 311 overlapped by the folded portion can be bonded by passing through the pressing step. Similarly, the adhesive 332 is provided on each of the two holding portions 312. In addition, in the present embodiment, the spacer 320 composed of a foam material is used. However, the material of the spacer 320 is not particularly limited.

< step of folding back FPC >

First, the bent portion between the first and second main body portions 311A and 311B is bent along the first valley folding line L10 (see fig. 8B). Next, the bent portion between the second main body portion 311B and the third main body portion 311C is bent along the second valley folding line L11 (see fig. 8C). Finally, the bent portions between the second body portion 311B and the two holding portions 312 are bent along the third valley folding line L12 (the mountain folding line in fig. 8 c) (see fig. 8 d). Thereafter, the respective portions of the wiring board main body portion 311 overlapped by the folded portion 350 are bonded by going through a pressing process.

< advantages of FPC of the present embodiment >

According to the FPC300 of the present embodiment, a part of the first main body portion 311A and the third main body portion 311C in the wiring board main body portion 311 portion where the folded-back portion 350 is overlapped is sandwiched by 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 holding portion 312 integrally connected to the adjacent portion and bonded by the adhesive.

In addition, in the FPC300 of the present embodiment, the spacer 320 is arranged between two portions of the wiring board main body portion 311 overlapped by the folded-back portion. More specifically, the folded-back portion of the FPC300 of the present embodiment includes a first folded-back portion (a portion folded back along the first valley fold line L10) and a second folded-back portion (a portion folded back along the second valley fold line L11). The single spacer 320 is disposed between the two portions of the wiring board main body portion 311 overlapped by the first folded portion, and is also disposed between the two portions of the wiring board main body portion 311 overlapped by the second folded portion. By adopting the configuration including the spacers 320 thus configured, the radius of curvature of the folded-back portion can be increased only by the portion where the spacers 320 are provided. This can alleviate the repulsive force acting on the folded portion. In addition, disconnection of the electric circuit for electric wiring can also be suppressed.

With the above-described configuration, the same effects as those of embodiment 1 can be obtained also in this embodiment. In addition, even in the present embodiment, as shown in embodiment 1 described above, various low-strength structures can be adopted at the folded-back portion between the wiring board main body portion 311 and the holding portion 312. In addition, in the present embodiment, a configuration including the holding portion 312 provided at two locations is shown. However, a configuration including the holding portion 312 provided at only one location may be adopted. In addition, even in the configuration of the present embodiment, a straight line including a bending line (the third valley folding line L12 in the present embodiment) for folding back the holding portion 312 on the upper side in (a) of fig. 8 is located at a position on the opposite side of a straight line including the other bending line (the second valley folding line L11 in the present embodiment) of the wiring board main body portion 311 across the adhesive portion (the adhesive portion of the holding portion 312 and the third main body portion 311C in the present embodiment) of the holding portion 312.

(example 5)

Embodiment 5 of the present invention is shown in fig. 9. Fig. 9 is an explanatory view of a bending step of the FPC400 according to embodiment 5 of the present invention. The states of the FPC400 at the respective steps are shown in a top view, respectively. In this example, the FPC is further simplified as compared with examples 1 to 3. Therefore, the wiring, the semicircular notch as a mark for bending, and the like are omitted.

< construction of FPC >

The basic structure of the FPC is as described in embodiment 1 above. The FPC400 of the present embodiment includes a wiring board main body 411 including a folded portion 450 and a holding portion 412 integrally connected to the wiring board main body 411. The holding section 412 holds the portion of the wiring board main body 411 overlapped by the folded portion 450. The wiring board body 411 includes an electric circuit (not shown) for electric wiring. The holding portion 412 does not have an electric circuit for electric wiring. However, the holding portion 412 does not necessarily have to have a structure including no circuit.

In the FPC400 of the present embodiment, the wiring board main body 411 includes three-part folded portions. That is, in fig. 9 (d), the wiring board main body portion 411 or the holding portion 412 is folded back along the first valley folding line L13, the second valley folding line L14, and the third valley folding line L15 in fig. 9 (a). For convenience, portions of the wiring board main body 411 that are separated by two bending lines (the first valley folding line L13 and the second valley folding line L14) are referred to as a first main body 411A, a second main body 411B, and a third main body 411C, respectively.

In the configurations shown in the above embodiments, the first body portion and the second body portion are provided continuously and linearly. The third body portion is provided in parallel with the first body portion and the second body portion and is provided linearly. In the configuration of the present embodiment, the first body 411A and the second body 411B are continuous and linear. However, the third body 411C is provided in a straight line perpendicular to the first body 411A and the second body 411B.

Further, a spacer 420 made of a foam material is provided in the second body portion 411B. An adhesive is coated on both sides of the spacer 420. In addition, an adhesive 431 is provided in the third body 411C. Thus, after the bending step, the respective portions of the wiring board main body 411 overlapped by the folded portion can be bonded by passing through the pressing step. The adhesive 432 is similarly provided in the holding portion 412. In addition, in the present embodiment, the spacer 420 composed of a foam material is used. However, the material of the spacer 420 is not particularly limited.

< step of turning back FPC >

First, the bent portion between the first and second body portions 411A and 411B is bent along the first valley folding line L13 (see fig. 9 (B)). In each of the above embodiments, the bending line is perpendicular to the direction in which each main body extends. In contrast, the first valley folding line L13 (folding line) is inclined at 45 ° with respect to the direction in which the first and second main bodies 411A, 411B extend. Next, the bent portion between the second body 411B and the third body 411C is bent along the second valley folding line L14 (see fig. 9C). Finally, the bent portion between the third body 411C and the holding portion 412 is bent along the third valley folding line L15 (see fig. 9 (d)). Thereafter, the respective portions of the wiring board main body 411 overlapped by the folded portion 450 are bonded by going through a pressing process.

< advantages of FPC of the present embodiment >

According to the FPC400 of the present embodiment, a part of the first main body portion 411A and the second main body portion 411B in the wiring board main body portion 411 portion where the folded-back portion 450 is overlapped is sandwiched by an adjacent portion (third main body portion 411C) adjacent to the holding portion 412 in the wiring board main body portion 411 and the holding portion 412 integrally connected to the adjacent portion.

In addition, in the FPC400 of the present embodiment, the spacer 420 is disposed between two portions of the wiring board main body 411 overlapped by the folded portion. More specifically, the turn-back portion of the FPC400 of the present embodiment includes a first turn-back portion (a portion turned back along the first valley fold line L13) and a second turn-back portion (a portion turned back along the second valley fold line L14). Further, a single spacer 420 is arranged between two portions of the wiring board main body 411 overlapped by the first folded portion, and also between two portions of the wiring board main body 411 overlapped by the second folded portion. By adopting the configuration including the spacers 420 arranged in this way, the radius of curvature of the folded portion can be increased only by the portion where the spacers 420 are provided. This can alleviate the repulsive force acting on the folded portion. In addition, disconnection of the electric circuit for electric wiring can also be suppressed.

With the above configuration, the same effects as those of embodiment 1 can be obtained in this embodiment. In addition, even in the present embodiment, as shown in the above-described embodiment 1, various low-strength structures may be adopted at the folded-back portion between the wiring board main body portion 411 and the holding portion 412. In addition, even in the configuration of the present embodiment, a straight line including a bending line (the third valley folding line L15 in the present embodiment) for folding back the holding portion 412 in (a) of fig. 9 is located at a position on the opposite side of the straight line including the other bending line (the second valley folding line L14 in the present embodiment) of the wiring board main body portion 411 across the bonded portion of the holding portion 412 (the bonded portion of the holding portion 412 and the second main body portion 411B and the third main body portion 411C in the present embodiment).

(example 6)

Embodiment 6 of the present invention is shown in fig. 10 and 11. Fig. 10 and 11 are explanatory views of the bending step of the FPC500 according to embodiment 6 of the present invention. The states of the FPC500 at the respective steps are shown in a plan view. In addition, in this example, the FPC is further simplified as compared with examples 1 to 3. Therefore, the wiring, the semicircular notch as a mark for bending, and the like are omitted.

< construction of FPC >

The basic structure of the FPC is as described in embodiment 1 above. The FPC500 of the present embodiment includes a wiring board main body portion 511 including a folded portion 550, and a holding portion 512 integrally connected to the wiring board main body portion 511. The holding section 512 holds the portion of the wiring board main body 511 overlapped by the folded-back section 550. The wiring board main body portion 511 includes an electric circuit (not shown) for electric wiring. The holding portion 512 does not have an electric circuit for electric wiring. However, the holding portion 512 does not necessarily have to have a structure including no circuit. In the present embodiment, the holding portions 512 are provided at four locations.

In the FPC500 of the present embodiment, the wiring board main body portion 511 includes twelve locations of folded-back portions. That is, in fig. 11 (b), the wiring board main body portion 511 is folded back along the 4 first valley folding lines L16, the 4 second valley folding lines L17, and the 4 third valley folding lines L18 in fig. 10 (a). For convenience, the portions of the wiring board main body portion 511 divided by the 4 first valley folding lines L16 and the 4 second valley folding lines L17 are referred to as a first main body portion 511A (one portion), a second main body portion 511B (four portions), and a third main body portion 511C (four portions), respectively.

Spacers 520 made of a foam material are provided at the second main body portion 511B at the four locations, respectively. An adhesive is coated on both sides of the spacer 520. The first body portion 511A is provided with an adhesive 531 in the vicinity of the second body portion 511B adjacent to the four portions. Further, the adhesives 532 are provided to the four holding portions 512, respectively. In addition, in the present embodiment, the spacer 520 composed of a foam material is used. However, the material of the spacer 520 is not particularly limited.

< step of folding back FPC >

First, the bent portion between the third body portion 511C and the second body portion 511B is bent along each of the 4 first valley folding lines L16 (see fig. 10 (B)). Next, the bent portion between the second body portion 511B and the first body portion 511A is bent along 4 second valley folding lines L17 (see fig. 11A). Finally, the bent portion between the second body portion 511B and the holding portion 512 is bent along 4 third valley folding lines L18 (called mountain folding lines in fig. 11 a) (see fig. 11B). Thereafter, the respective portions of the wiring board main body 511 overlapped by the four folded portions 550 are bonded through a pressing process.

< advantages of FPC of the present embodiment >

According to the FPC500 of the present embodiment, a part of the first main body portion 511A and the third main body portion 511C in the wiring board main body portion 511 portion overlapped with the folded-back portion 550 is sandwiched by an adjacent portion (the second main body portion 511B) adjacent to the holding portion 512 in the wiring board main body portion 511 and the holding portion 512 integrally connected to the adjacent portion and bonded by an adhesive.

In addition, in the FPC500 of the present embodiment, the spacer 520 is disposed between two portions of the wiring board main body portion 511 overlapped by the folded-back portion. More specifically, the folded-back portion of the FPC500 of the present embodiment includes a first folded-back portion (a portion folded back along the first valley fold line L16) and a second folded-back portion (a portion folded back along the second valley fold line L17). The single spacer 520 is disposed between the two portions of the wiring board main body portion 511 overlapped by the first folded portion, and is also disposed between the two portions of the wiring board main body portion 511 overlapped by the second folded portion. By adopting the configuration including the spacers 520 thus configured, the radius of curvature of the folded portion can be increased only by the portion where the spacers 520 are provided. In addition, this can alleviate the repulsive force acting on the folded portion. It is possible to suppress disconnection of the electric circuit for electric wiring.

With the above configuration, the same effects as those of embodiment 1 can be obtained in this embodiment. In addition, even in the present embodiment, as shown in the above-described embodiment 1, various low-strength structures can be adopted at the folded-back portion between the wiring board main body portion 511 and the holding portion 512. In addition, even in the configuration of the present embodiment, a straight line including a bending line (the third valley folding line L18 in the present embodiment) for folding back the holding section 512 is located at a position on the opposite side of a straight line including the other bending line (the second valley folding line L17 in the present embodiment) of the wiring board main body portion 511 with the adhesive portion (the adhesive portion of the holding section 512 and the first main body portion 511A in the present embodiment) of the holding section 512 interposed therebetween.

Claims (10)

1. A flexible printed wiring board characterized in that,

the flexible printed wiring board includes a wiring board main body including a folded portion and an adjacent portion,

the adjacent portion is integrally connected with the holding portion by the folded-back portion,

at least a part of the portions of the wiring board main body portion overlapped by the folded-back portion is sandwiched by the adjacent portion and the holding portion bonded by the adhesive.

2. The flexible printed wiring board according to claim 1,

the wiring board main body portion has a circuit for electrical wiring, and the holding portion does not have a circuit for electrical wiring.

3. The flexible printed wiring board according to claim 1 or 2,

the spacer is arranged between two portions of the wiring board main body portion overlapped by the turn-back portion.

4. The flexible printed wiring board according to claim 3,

the folded-back portion includes a first folded-back portion and a second folded-back portion,

a single spacer is disposed between both the portions of the wiring board main body portion overlapped by the first folded back portion and also between both the portions of the wiring board main body portion overlapped by the second folded back portion.

5. The flexible printed wiring board according to claim 3,

the turn-back portion includes a first turn-back portion and a second turn-back portion,

a first spacer is disposed between two portions of the wiring board main body portion overlapped by the first folded-back portion,

the second spacer is disposed between two portions of the wiring board main body portion overlapped by the second folded portion.

6. The flexible printed wiring board according to any one of claims 1 to 5,

the folded-back portion between the wiring board main body portion and the holding portion is provided with a low-strength structure having a lower bending strength than other folded-back portions.

7. The flexible printed wiring board according to claim 6,

the low-strength structure includes at least one through-hole provided along the turn-back portion.

8. The flexible printed wiring board according to claim 6,

the low-strength structure includes at least one slit disposed along the turn-back portion.

9. The flexible printed wiring board according to claim 6,

the low-strength structure includes a thin-walled portion that is provided at least at one location along the turn-back portion and has a thickness thinner than the wiring board main body portion and the holding portion.

10. The flexible printed wiring board according to any one of claims 1 to 9,

a straight line including a bending line for folding back the holding section is located at a position on the opposite side of a straight line including the other bending line of the wiring board main body section with respect to the bonding section of the holding section.

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