WO2020044460A1

WO2020044460A1 - Flexible printed board

Info

Publication number: WO2020044460A1
Application number: PCT/JP2018/031935
Authority: WO
Inventors: 卓郎品田
Original assignee: 三菱電機株式会社
Priority date: 2018-08-29
Filing date: 2018-08-29
Publication date: 2020-03-05

Abstract

This flexible printed board is provided with: a first pattern layer 2 which is disposed on a surface of a first base formed in the shape of a flexible plate, includes a plurality of signal wires 2a, 2b connecting external substrates, and has terminal portions 20a, 20b at both ends of each signal wire; a second pattern layer 3 which is disposed on a back surface of the first base and has terminal portions 30a, 30b at positions corresponding to the terminal portions 20a, 20b; first and second cover layers 4, 5 covering the first and second pattern layers with end portions thereof exposed; and first and second via holes 6a, 6b connecting the terminal portions of the second pattern layer and the first pattern layer. The terminal portions of the second pattern layer are wired across the end portions of the cover layer. The first via holes connect the terminal portions of the second pattern layer and the first pattern layer on the side closer to the external substrate connected to the terminal portions of the first pattern layer or the second pattern than the end portions of the cover layers. The second via holes connect extension portions of the terminal portions of the second pattern layer wired across the end portions of the cover layers and the signal wire portions of the first pattern layer.

Description

Flexible printed circuit board

The present application relates to a flexible printed circuit board.

フレキシブル When connecting wiring between boards, a flexible board is often used. In particular, even when an optical module product is mounted on an optical transceiver, a flexible substrate is used for connection between the transceiver-side substrate and a PKG (package) ceramic substrate.

In general, a flexible substrate is used for wiring between the substrates. Particularly, when an optical module product is mounted on an optical transceiver, the flexible substrate connected to the optical module product is bent for position adjustment. At the time of bending, stress concentrates on the base portion of the substrate, which may cause disconnection.

In order to suppress this disconnection, for example, in Patent Document 1, a first brazing material pattern is provided at one end of a flexible substrate at a lead connecting portion of a first wiring pattern, and a second brazing material pattern is provided at a lead connecting portion of a second wiring pattern. By disposing the second brazing material pattern longer than the first brazing material pattern, stress is dispersed when the flexible substrate 11 is bent, and disconnection of the first wiring pattern and the second wiring pattern is suppressed. Is disclosed.

JP-A-2011-238883 (paragraphs 0018 to 0022, FIG. 2)

However, in the flexible substrate of Patent Document 1, although the disconnection is suppressed, once the disconnection occurs, the operation of the optical module product must be interrupted, and there is a problem that the optical module product cannot be recovered unless the flexible substrate is replaced with a new one.

The present application discloses a technique for solving the above-described problems, and not only suppresses disconnection, but also can maintain electrical continuity even when disconnection occurs, realizing a long life. An object of the present invention is to provide a flexible printed circuit board that can be used.

A flexible printed board disclosed in the present application has a base formed in a flexible plate shape made of a dielectric material, and a plurality of signal lines provided on a surface of the base and connecting between external substrates. A first pattern layer provided with a terminal portion at an end thereof, and a second pattern layer provided with a terminal portion on the back surface of the base corresponding to the terminal portion of the first pattern layer; A first cover layer and a second cover layer that respectively expose and cover a surface of an end portion of the layer and the second pattern layer, and a terminal portion of the second pattern layer and a terminal of the first pattern layer via the base. A first via hole and a second via hole for electrically connecting the first and second pattern layers to each other, and a terminal portion of the second pattern layer extends over an end of the first cover layer and the second cover layer. Established and said The one via hole is provided so as to connect a portion of the terminal portion of the second pattern layer or the terminal portion of the first pattern layer on a side of the terminal portion of the second pattern layer or the first pattern layer connected to the external substrate. The second via hole is provided so as to connect an extended portion of the terminal portion of the second pattern layer to a corresponding terminal portion of the first pattern layer.

Further, a first base formed in a flexible plate shape made of a dielectric material, and a plurality of signal lines provided on a surface of the first base and connecting between external substrates, are provided at an end of the signal line. A first pattern layer provided with a terminal portion, and a second pattern layer provided with a terminal portion on the back surface of the first base corresponding to the terminal portion of the first pattern layer, A second base provided on the front surface side and formed in a flexible plate shape made of a dielectric material, and a terminal portion was provided on the surface of the second base corresponding to the terminal portion of the first pattern layer. A third pattern layer, a first cover layer and a second cover layer that respectively expose and cover the end surfaces of the third pattern layer and the second pattern layer, the first base, the first pattern layer and Via the second base, the second A terminal portion of the pattern layer, a first via hole and a second via hole for electrically connecting the terminal portion of the first pattern layer and the terminal portion of the third pattern layer, the terminal portion of the second pattern layer and The terminal portion of the third pattern layer is disposed so as to extend over an end of the first cover layer and the second cover layer, and the first via hole is provided in the second pattern layer or the third pattern. The second pattern layer on the side connected to the external substrate of the terminal portion of the layer, provided to connect the terminal portion of the first pattern layer and the third pattern layer, the second via hole, It is provided so as to connect an extended portion of the terminal portion of the second pattern layer and the third pattern layer to a corresponding terminal portion of the first pattern layer.

According to the present application, the terminal portion of the pattern layer is extended and wired across the end portion of the cover layer, the first via hole is connected on the external substrate side connected to the terminal portion, and the second via hole is connected to the end portion of the cover layer. By connecting with the extended part of the terminal part wired across, the strength against stress concentration on the flexible printed circuit board can be improved, disconnection can be suppressed, and the signal wiring terminal part around the stress concentration part Can maintain electrical continuity even when the wire is disconnected.

FIG. 2 is an exploded perspective view showing a configuration of the flexible printed circuit board according to the first embodiment. FIG. 3 is a plan view of a pattern layer in the flexible printed board according to the first embodiment. FIG. 2 is a cross-sectional view illustrating a configuration of a flexible printed board according to Embodiment 1. FIG. 5 is a cross-sectional view showing another example of use of the flexible printed board according to the first embodiment. FIG. 9 is a plan view of a pattern layer in a flexible printed board according to Embodiment 2. FIG. 7 is a cross-sectional view illustrating a configuration of a flexible printed board according to a second embodiment. FIG. 13 is a plan view of a pattern layer in a flexible printed board according to Embodiment 3. FIG. 13 is a cross-sectional view illustrating a configuration of a flexible printed board according to a third embodiment. FIG. 14 is a plan view of a pattern layer in a flexible printed board according to a fourth embodiment.

Embodiment 1 FIG.
FIG. 1 is an exploded perspective view showing the configuration of the flexible printed circuit board according to the first embodiment. FIG. 2 is a plan view showing the configuration of the pattern layer of the flexible printed board, and FIG. 3 is a cross-sectional view of the flexible printed board at the position of the pattern layer shown in FIG.

As shown in FIGS. 1 to 3, the flexible printed circuit board 101 includes a first base 1, a first pattern layer 2 provided on the front surface of the first base 1, and a second pattern provided on the back surface of the first base 1. It comprises a layer 3, a first cover layer 4 for protecting the first pattern layer 2, and a second cover layer 5 for protecting the second pattern layer 3.

The first base 1 is made of a dielectric material such as polyimide and is formed in a 25 μm-thick flexible plate. A first pattern layer 2 is provided on the front surface of the first base 1, and a second pattern layer 3 is provided on the back surface. The first base 1 is provided with a first via hole 6 a and a second via hole 6 b penetrating from the first pattern layer 2 to the second pattern layer 3.

The first pattern layer 2 is made of a metal material such as copper or gold, and is formed on the surface of the first base 1 with a thickness of 28 μm ± 5% by a method such as plating or printing. The first pattern layer 2 has a plurality of pairs of

signal wirings

2a and 2b as signal lines connecting the external substrates. At both ends of the first pattern layer 2, a plurality of terminal portions 20g of the ground wiring are provided next to the pair of

terminal portions

20a and 20b of the

signal wirings

2a and 2b. The

terminal portions

20a and 20b of the

signal wires

2a and 2b and the terminal portion 20g of the ground wire are provided with a first via hole 6a and a second via hole 6b penetrating through the first base 1 to the second pattern layer 3, The first pattern layer 2 and the second pattern layer 3 are electrically connected.

Like the first pattern layer 2, the second pattern layer 3 is made of a metal material such as copper or gold, and is formed on the back surface of the first base 1 with a thickness of 28 μm ± 5% by a method such as plating or printing. You. The second pattern layer 3 includes a plurality of pairs of signal wiring

terminal portions

30a and 30b, and a ground wiring 3g and a ground wiring 3g provided on the entire central portion so as to correspond to the wiring pattern of the first pattern layer 2. , And a plurality of terminal portions 30g arranged toward both ends. The

terminal portions

30a and 30b of the signal wiring and the terminal portion 30g of the ground wiring 3g are provided with a first via hole 6a and a second via hole 6b penetrating into the first pattern layer 2, and the second pattern layer 3 and the first pattern The layer 2 is electrically connected.

The first via hole 6a and the second via hole 6b are made of a metal material such as copper or gold, and are formed in a columnar shape with a thickness of 100 μm by plating or the like. The first via hole 6 a and the second via hole 6 b are formed through the first pattern layer 2, the first base 1, and the second pattern layer 3, and electrically connect the first pattern layer 2 and the second pattern layer 3. Conduct continuity.

The first cover layer 4 and the second cover layer 5 are made of a dielectric material such as polyimide, and are formed in a flexible plate having a thickness of 40 μm. The first cover layer 4 and the second cover layer 5 are respectively provided with an adhesive on the front surface of the first base 1 on which the first pattern layer 2 is formed and on the back surface of the first base 1 on which the second pattern layer 3 is formed. To protect the first pattern layer 2 and the second pattern layer 3 respectively.

The flexible printed board 101 is mounted on the external board 7 via the

terminal portions

30a, 30b, 30g of the second pattern layer 3. The

terminal portions

30a, 30b, 30g of the second pattern layer 3 and the external substrate 7 are joined by, for example, a joining material such as a solder material or a conductive film. In general, when the flexible printed board 101 is bent, stress is easily applied in a direction in which the flexible printed board 101 is peeled off from the board. As shown in FIG. 3, when the flexible printed board 101 is bent in a direction in which the flexible printed board 101 is peeled off from the board (U direction), stress tends to concentrate on the stress concentration portion Su at a cut in the second cover layer 5. When the stress is concentrated on the stress concentration portion Su, disconnection is likely to occur at the position of Bu on the second pattern layer 3. Conventionally, the

terminal portions

30a and 30b of the signal wiring of the second pattern layer 3 are wired from the end of the second pattern layer 3 to a position short of the position of Bu. Therefore, the

terminal portions

30a and 30a of the signal wiring are located at the position of Bu. There was no 30b wiring.

In the flexible printed board 101 according to the first embodiment, the

terminal portions

30a and 30b of the signal wiring of the second pattern layer 3 extend and extend over the position of Bu, that is, the position of the end of the second cover layer 5. Have been. In addition, the first via hole 6 a is closer to the

terminal portion

30 a, 30 b of the second pattern layer 3 than the end of the second cover layer 5 is connected to the external substrate 7, and the terminal portion of the signal wiring of the second pattern layer 3 The

terminals

30a and 30b are connected to the

terminals

20a and 20b of the

signal wirings

2a and 2b of the first pattern layer 2, respectively. The second via hole 6 b is formed by extending the

terminal portions

30 a and 30 b of the second pattern layer 3 wired across the end of the second cover layer 5 and the signal wiring 2 a of the first pattern layer 2. 2b are electrically connected to the corresponding portions of the

terminal portions

20a and 20b.

Thereby, strength against stress concentration on the flexible printed circuit board 101 can be improved, and disconnection can be suppressed. Further, even when the terminal portion of the signal wiring (the position of Bu) is disconnected around the stress concentration portion, the external substrate 7 → the

terminal portions

30a and 30b of the signal wiring of the second pattern layer 3 → the first via hole 6a → the first via hole. Electrical continuity can be maintained in the path of the

signal wirings

2a and 2b of the pattern layer 2.

(4) When the flexible printed board 101 is bent in the direction (D direction) opposite to the direction in which the flexible printed board 101 is peeled off from the board, stress tends to concentrate on the stress concentration portion Sd at the cut in the first cover layer 4. When the stress is concentrated on the stress concentration portion Sd, disconnection is likely to occur at the position of Bd on the first pattern layer 2.

Also in this case, in the flexible printed circuit board 101 according to the first embodiment, the

terminal portions

30a and 30b of the signal wiring of the second pattern layer 3 are also positioned at the position of Bd, that is, the position of the end of the second cover layer 5. Since the wiring is extended so as to straddle, strength against stress concentration on the flexible printed circuit board 101 can be improved, and disconnection can be suppressed. Further, even when the terminal portion of the signal wiring (the position of Bd) is broken around the stress concentration portion, the external substrate 7 → the signal

wiring terminal portions

30a and 30b of the second pattern layer 3 → the second via hole 6b → the first via hole 6b → Electrical continuity can be maintained in the path of the

signal wirings

2a and 2b of the pattern layer 2.

Although the case where the external substrate 7 is bonded to the

terminal portions

30a and 30b of the second pattern layer 3 has been described, the present invention is not limited to this. As shown in FIG. 4, the external substrate 7 may be joined to the

terminal portions

20a and 20b of the first pattern layer 2. In this case, the same effect can be obtained.

As described above, according to the flexible printed circuit board 101 according to the first embodiment, the first base 1 formed of a flexible plate made of a dielectric material and the first base 1 A first pattern layer 2 having a plurality of pairs of

signal wirings

2a and 2b for connecting between the substrates, having

terminal portions

20a and 20b provided at both ends of the

signal wirings

2a and 2b, and terminals of the first pattern layer 2 Corresponding to the

portions

20a and 20b, the second pattern layer 3 in which the

terminal portions

30a and 30b are provided on the back surface of the first base 1, and the surfaces of the end portions of the first pattern layer 2 and the second pattern layer 3, respectively. The first and second cover layers 4 and 5 that are exposed and covered, and the

terminals

30a and 30b of the second pattern layer 3 and the

terminals

20a and 20b of the first pattern layer 2 are electrically connected via the first base 1. Connect to first And second via

holes

6a, 6b, and the

terminal portions

30a, 30b of the second pattern layer 3 are wired so as to extend over the ends of the first and second cover layers 4, 5, and the first via hole 6a Are the

terminal portions

30a and 30b of the second pattern layer 3 or the

terminal portions

30a and 30b of the second pattern layer 3 on the side connected to the external substrate 7 of the

terminal portions

20a and 20b of the first pattern layer 2. The second via holes 6b are provided so as to connect the

terminal portions

20a and 20b of the second pattern layer 2 and the corresponding terminal portions 20a of the first pattern layer 2 with the extended portions of the

terminal portions

30a and 30b of the second pattern layer 3. , 20b are connected to each other, so that strength against stress concentration on the flexible printed circuit board can be improved, and disconnection can be suppressed. Further, even when the terminal portion of the signal wiring is disconnected around the stress concentration portion, electrical conduction can be maintained.

Embodiment 2 FIG.
In the first embodiment, the case where the

terminal portions

30a and 30b of the signal wiring of the second pattern layer 3 are disconnected has been described. It shows about.

FIG. 5 is a plan view showing the configuration of the pattern layer of the flexible printed board according to the second embodiment, and FIG. 6 is a cross-sectional view of the flexible printed board at the position of the CC in the pattern layer of FIG.

As shown in FIGS. 5 and 6, in the second embodiment, in the configuration of the flexible printed circuit board 102, the second base 8 and the second base layer 8 are further provided on the second pattern layer 3 of the flexible printed circuit board 101 of the first embodiment. The third pattern layer 9 is provided on the second base 8.

The second base 8 is made of a dielectric material such as polyimide, like the first base 1, and is formed in a 25 μm-thick flexible plate. The third pattern layer 9 is provided on the surface of the second base 8. The second base 8 is provided with a first via hole 6 a and a second via hole 6 b penetrating from the third pattern layer 9 to the second pattern layer 3.

Like the second pattern layer 3, the third pattern layer 9 is made of a metal material such as copper or gold, and is formed on the surface of the second base 8 with a thickness of 28 μm ± 5% by a method such as plating or printing. You. The third pattern layer 9 includes a plurality of pairs of signal

wiring terminal portions

90a and 90b and a ground wiring 9g and a ground wiring 9g provided on the entire central portion so as to correspond to the wiring pattern of the first pattern layer 2. And a plurality of terminal portions 90g disposed toward both ends of the terminal portion. The first via hole 6a and the second via hole 6b penetrating to the second pattern layer 3 are provided in the

terminal portions

90a and 90b of the signal wiring and the terminal portion 90g of the ground wiring 9g. The layer 2 and the second pattern layer 3 are electrically connected.

The first via hole 6a and the second via hole 6b are made of a metal material such as copper or gold, similarly to the via hole 6 in the first embodiment, and are formed in a columnar shape with a thickness of 100 μm by plating or the like. The first via hole 6a and the second via hole 6b are formed through the first pattern layer 2, the first base 1, the second pattern layer 3, the second base 8 and the third pattern layer 9, and the third pattern layer 9 The first pattern layer 2 and the second pattern layer 3 are electrically connected.

(4) The first cover layer 4 is bonded to the surface of the second base 8 on which the third pattern layer 9 is formed with an adhesive or the like to protect the third pattern layer 9. Other configurations of the flexible printed circuit board 102 according to the second embodiment are the same as those of the flexible printed circuit board 101 according to the first embodiment, and corresponding portions are denoted by the same reference numerals and description thereof will be omitted.

Also in the flexible printed board 102 according to the second embodiment, as shown in FIG. 6, when the flexible printed board 102 is bent in a direction in which the flexible printed board 102 is peeled off from the board (U direction), the stress at the cut in the second cover layer 5 is reduced. Stress tends to concentrate on the concentrated portion Su. When the stress is concentrated on the stress concentration portion Su, not only the disconnection occurs at the position of Eu of the second pattern layer 3 but also the disconnection may occur up to the position of Eu of the first pattern layer 2.

In the flexible printed board 102 according to the second embodiment, the

terminal portions

30 a and 30 b of the signal wiring of the second pattern layer 3 are wired so as to straddle the position of Eu, that is, the position of the end of the second cover layer 5. In addition, the

terminal portions

90a and 90b of the signal wiring of the third pattern layer 9 are also wired so as to straddle the position B, that is, the position of the end of the second cover layer 5.

In addition, the first via hole 6 a is closer to the

terminal portion

30 a, 30 b of the second pattern layer 3 than the end of the second cover layer 5 is connected to the external substrate 7, and the terminal portion of the signal wiring of the second pattern layer 3 30a, 30b, the

terminal portions

20a, 20b of the first pattern layer 2 and the

terminal portions

90a, 90b of the third pattern layer 9 are electrically connected. The second via holes 6b are extended portions of the

terminal portions

30a, 30b of the second pattern layer 3 wired across the end of the second cover layer 5, the signal wires 2a of the first pattern layer 2, The corresponding portions of the

terminal portions

20a and 20b of the second pattern layer 2b and the extended and wired portions of the

terminal portions

90a and 90b of the third pattern layer 9 wired across the end of the second cover layer 5 are electrically connected. I do.

Thereby, the strength against stress concentration on the flexible printed circuit board 102 can be further improved, and disconnection can be suppressed. In addition, not only the terminal portion of the signal wiring (the position of Bu) but also the signal wiring (the position of Eu) is broken around the stress concentration portion, the external substrate 7 → the terminal portion 30a of the signal wiring of the second pattern layer 3. , 30b → the first via hole 6a → the

terminal portions

90a, 90b of the signal wiring of the third pattern layer 9 → the second via hole 6b → the electrical wiring is maintained in the route of the

signal wiring

2a, 2b of the first pattern layer 2. Can be.

Even when the flexible printed circuit board 102 is bent in the direction (D direction) opposite to the direction in which the flexible printed circuit board 102 is peeled off from the board, the

terminal portions

30a and 30b of the signal wiring of the second pattern layer 3 are formed in the flexible printed circuit board 102 in the second embodiment. , Eu, that is, not only are wired so as to straddle the position of the end of the second cover layer 5, but also the

terminal portions

90a, 90b of the signal wiring of the third pattern layer 9 are located at the position of B, that is, Since the wiring is provided so as to straddle the position of the end of the two cover layers 5, the strength against stress concentration on the flexible printed circuit board 102 can be further improved, and disconnection can be suppressed. In addition, not only the signal wiring terminal portion (Bd position) but also the signal wiring (Ed position (not shown)) is broken around the stress concentration portion, the external substrate 7 → the signal wiring terminal of the second pattern layer 3. Electrical continuity can be maintained in the path of the

parts

30a, 30b → the second via hole 6b → the

signal wirings

2a, 2b of the first pattern layer 2.

Although the case where the external substrate 7 is bonded to the

terminal portions

30a and 30b of the second pattern layer 3 has been described, the present invention is not limited to this. The external substrate 7 may be joined to the

terminal portions

90a and 90b of the third pattern layer 9. In this case, the same effect can be obtained.

As described above, according to the flexible printed circuit board 102 according to the second embodiment, the first base 1 formed of a flexible plate made of a dielectric material and the surface of the first base 1 A first pattern layer 2 having a plurality of pairs of

signal wirings

2a and 2b for connecting between the substrates, having

terminal portions

20a and 20b provided at both ends of the

signal wirings

2a and 2b, and terminals of the first pattern layer 2 A second pattern layer 3 having

terminal portions

30a and 30b provided on the back surface of the first base 1 corresponding to the

portions

20a and 20b, and a flexible material made of a dielectric material provided on the front surface side of the first pattern layer 2 The second base 8 formed in a flat plate shape and the third pattern layer 9 having the

terminal portions

90a and 90b provided on the surface of the second base 8 corresponding to the

terminal portions

20a and 20b of the first pattern layer 2. When, The first and second cover layers 4 and 5 expose and cover the surfaces of the end portions of the three pattern layer 9 and the second pattern layer 3, respectively, and the first base 1, the first pattern layer 2 and the second base 8 And first and second via

holes

6a and 6b for electrically connecting the

terminal portions

30a and 30b of the second pattern layer 3 and the

terminal portions

90a and 90b of the third pattern layer 9, respectively. The

terminal portions

30a, 30b and the

terminal portions

90a, 90b of the third pattern layer 9 are wired so as to extend over the ends of the first and second cover layers 4, 5, and the first via hole 6a is The

terminal portions

30a, 30b of the second pattern layer 3 on the side of the

terminal portions

30a, 30b of the layer 3 or the

terminal portions

90a, 90b of the third pattern layer 9 connected to the external substrate 7, and the terminal portions 20a of the

first pattern layer

2 , 20b and third pattern 9 are provided so as to connect the

terminal portions

90a and 90b, and the second via holes 6b are formed by extending the

terminal portions

30a and 30b of the second pattern layer 3 and the

terminal portions

90a and 90b of the third pattern layer 9. And the corresponding

terminal portions

20a and 20b of the first pattern layer 2 are connected to each other, so that the strength against stress concentration on the flexible printed circuit board can be further improved, and disconnection can be suppressed. In addition, even when not only the terminal portion of the signal wiring but also the signal wiring is disconnected around the stress concentration portion, electrical conduction can be maintained. Further, since the second pattern layer 3 and the third pattern layer 9 have the same shape, the same mask can be used for forming the second pattern layer 3 and the third pattern layer 9. Therefore, the cost for manufacturing the flexible substrate can be reduced.

Embodiment 3 FIG.
In the first and second embodiments, the first and second cover layers 4 and 5 have the same length, but in the third embodiment, the first and second cover layers have different lengths. The case is shown.

FIG. 7 is a plan view showing the configuration of the pattern layer of the flexible printed board according to the third embodiment, and FIG. 8 is a cross-sectional view of the flexible printed board at the position of the FF in the pattern layer of FIG.

As shown in FIGS. 7 and 8, in the third embodiment, in the configuration of the flexible printed circuit board 103, the first cover layer 4 of the flexible printed circuit board 102 of the second embodiment is provided shorter than the second cover layer 5. Have been. Other configurations of the flexible printed circuit board 103 according to the third embodiment are the same as those of the flexible printed circuit board 102 according to the second embodiment, and the corresponding portions are denoted by the same reference numerals and description thereof will be omitted.

Normally, when a flexible printed circuit board is bent, if the lengths of both cover layers are the same, stress is concentrated on the same cut portion, and there is a high possibility that a break occurs in the pattern layer. As shown in FIG. 8, by shifting the positions of the end portions of the first and second cover layers 4 and 5, a position where disconnection may occur is determined by the position of Gu in the second pattern layer 3 and the first pattern layer 2. And Hd positions of the third pattern layer 9 and the first pattern layer 2. This makes it possible to suppress disconnection by dispersing the stress concentration positions. Further, similarly to the second embodiment, electrical continuity can be maintained not only at the terminal portion of the signal wiring around the stress concentration portion but also when the signal wiring is disconnected.

As described above, according to the flexible printed circuit board 103 according to the third embodiment, the length of the first cover layer 4 and the length of the second cover layer 5 are different from each other. By shifting the position of the portion and the end of the second cover layer 5, not only the effect of the second embodiment but also the position of stress concentration can be dispersed, and disconnection can be suppressed.

In the first, second, and third embodiments, the

ground wirings

3g, 9g of the second pattern layer 3 and the third pattern layer 9 may have a mesh shape as shown in FIG. In the case of a mesh shape, the second pattern layer 3 and the third pattern layer 9 are easily bent. Therefore, when the flexible printed board is bent, the stress is dispersed due to the deformation of the mesh portion first, and it is possible to suppress the occurrence of disconnection due to the concentration of stress at the cut of the cover layer.

Although this application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments may apply to particular embodiments. However, the present invention is not limited thereto, and can be applied to the embodiment alone or in various combinations. Accordingly, innumerable modifications not illustrated are contemplated within the scope of the technology disclosed herein. For example, a case where at least one component is deformed, added or omitted, and a case where at least one component is extracted and combined with a component of another embodiment are included.

Reference Signs List 1 1st base, 2 1st pattern layer, 2a, 2b signal wiring, 3 2nd pattern layer, 4 1st cover layer, 5 2nd cover layer, 6a 1st via hole, 6b 2nd via hole, 7 outside board, 8 Second base, 9 {third pattern layer, 20a, 20b, 30a, 30b, 90a, 90b} terminal section, 101, 102, 103} flexible printed circuit board.

Claims

A base formed into a flexible plate made of a dielectric material,
A first pattern layer provided on the surface of the base and having a plurality of signal lines connecting between external substrates, and a terminal portion provided at an end of the signal line;
In correspondence with the terminal portion of the first pattern layer, a second pattern layer provided with a terminal portion on the back surface of the base,
A first cover layer and a second cover layer that respectively expose and cover the surfaces of the end portions of the first pattern layer and the second pattern layer,
A first via hole and a second via hole for electrically connecting a terminal portion of the second pattern layer and a terminal portion of the first pattern layer via the base,
The terminal portion of the second pattern layer is disposed so as to extend over an end of the first cover layer and the second cover layer, and the first via hole is provided in the second pattern layer or the first pattern. The second pattern layer on the side of the terminal portion of the layer connected to the external substrate and the terminal portion of the first pattern layer are provided so as to be connected, and the second via hole is a terminal of the second pattern layer A flexible printed circuit board provided so as to connect an extended portion of the portion and a corresponding terminal portion of the first pattern layer.
A first base formed into a flexible plate made of a dielectric material,
A first pattern layer provided on the surface of the first base and having a plurality of signal lines connecting between external substrates, and a terminal portion provided at an end of the signal line,
Corresponding to the terminal portion of the first pattern layer, a second pattern layer provided with a terminal portion on the back surface of the first base,
A second base provided on the surface side of the first pattern layer and formed in a flexible plate shape made of a dielectric material,
Corresponding to the terminal portion of the first pattern layer, a third pattern layer provided with a terminal portion on the surface of the second base,
A first cover layer and a second cover layer that respectively expose and cover the surfaces of the end portions of the third pattern layer and the second pattern layer,
Via the first base, the first pattern layer and the second base, electrically connect the terminal portion of the second pattern layer, the terminal portion of the first pattern layer and the terminal portion of the third pattern layer. Comprising a first via hole and a second via hole to be connected,
The terminal portion of the second pattern layer and the terminal portion of the third pattern layer are disposed so as to extend over the end portions of the first cover layer and the second cover layer, and the first via hole is The second pattern layer or the terminal portion of the third pattern layer on the side connected to the external substrate of the terminal portion is provided so as to connect the terminal portions of the first pattern layer and the third pattern layer. The second via hole is provided so as to connect an extended portion of the terminal portion of the second pattern layer and the third pattern layer to a corresponding terminal portion of the first pattern layer. Flexible printed circuit board.
3. The flexible printed circuit board according to claim 1, wherein a length of the first cover layer is different from a length of the second cover layer. 4.
The second pattern layer is provided with a ground wiring connecting between the external substrates, and a plurality of ground wiring terminal portions disposed adjacent to each of the signal line terminal portions. 2. A flexible printed circuit board according to claim 1, wherein a terminal portion corresponding to a terminal portion of the ground wiring is provided at a position corresponding to the second pattern layer, and the ground wiring has a mesh shape. .
The second pattern layer and the third pattern layer are provided with a ground wire connecting between the external substrates, and a plurality of ground wire terminal portions disposed adjacent to each of the signal line terminal portions. And a terminal portion corresponding to a terminal portion of the ground wiring is provided on the first pattern layer at a position corresponding to the second pattern layer, and the ground wiring has a mesh shape. A flexible printed circuit board according to claim 1.