JP2016051769A - Flexible printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible printed circuit board which can inhibit disconnection of wiring.SOLUTION: A flexible printed circuit board comprises: a tabular part 2; a surface terminal part of terminals 3a, 3g which is provided at an end A of the tabular part 2 on a surface 2c side of the flexible printed circuit board; a rear terminal part of the terminals 3a, 3g which is provided at the end A of the tabular part 2 on a rear face 2d side of the flexible printed circuit board and electrically connected with the surface terminal part and in which a top face of the rear face terminal part serves as a connection part with a mounting substrate; electrical wiring 4 connected with the surface terminal part on the surface 2c side of the tabular part 2; and an extension part of the terminals 3a, 3g which is connected with the rear face terminal part on the rear face 2d side of the tabular part 2 and extends in a wiring direction where the electrical wiring 4 extends from the rear face terminal part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a flexible printed circuit board.

  Patent Document 1 describes a flexible printed circuit board connection structure. A semiconductor laser terminal is soldered to one end of the flexible printed board, and the other end of the flexible printed board is a connection terminal portion to be inserted into the connector. The conductor pattern is exposed at the connection terminal portion. A plurality of conductor patterns are formed, and two of the plurality of conductor patterns are power supply lines to the semiconductor laser.

Japanese Patent Laid-Open No. 5-335689

  By the way, in the flexible printed circuit board, when the wiring such as the connection terminal portion is bent, there is a possibility that the wiring is disconnected along with the bending of the wiring. In particular, when a high-frequency wiring that transmits a high-frequency signal of, for example, 10 Gbps or more is arranged on the flexible printed board, impedance matching is performed in the high-frequency wiring. Along with this impedance matching, the high-frequency wiring tends to be thinner than other wiring. Therefore, there is a high possibility that the high-frequency wiring is disconnected as compared with other wiring.

  This invention makes it a subject to provide the flexible printed circuit board which can suppress the disconnection of wiring.

  A flexible printed circuit board according to an embodiment of the present invention is provided on the back surface side of the flexible printed circuit board, the surface terminal portion provided on the front surface side at the end portion of the flexible circuit board, and the end portion of the flexible circuit board, On the rear surface side of the flexible substrate, the back surface terminal portion that is electrically connected to the front surface terminal portion, and the upper surface forms a connection portion with the mounting substrate, on the front surface side of the flexible substrate, and on the back surface side of the flexible substrate And an extended portion that is connected to the back surface terminal portion and extends from the back surface terminal portion in the wiring direction.

  According to the present invention, disconnection of wiring can be suppressed.

FIG. 1A is a view showing the surface of the flexible printed circuit board according to the first embodiment. FIG.1 (b) is a figure which shows the back surface of the flexible printed circuit board of Fig.1 (a). FIG. 2 is a diagram illustrating a connection state between the flexible printed circuit board and the wiring board according to the first embodiment. FIG. 3 is a plan view showing the flexible printed circuit board according to the second embodiment.

[Description of Embodiment of Present Invention]
First, the contents of the embodiment of the present invention will be listed and described. One embodiment of the present invention includes a flexible substrate, a front surface terminal portion provided on the front surface side at the end portion of the flexible substrate, and a front surface terminal portion provided on the back surface side at the end portion of the flexible substrate. Electrically connected, the back surface terminal portion whose upper surface forms a connection portion with the mounting substrate, the wiring connected to the front surface terminal portion on the front surface side of the flexible substrate, and the back surface terminal portion on the back surface side of the flexible substrate And a flexible printed circuit board including an extended portion provided in the wiring direction from the back surface terminal portion.

  According to this flexible printed circuit board, the front surface terminal portion connected to the wiring on the front surface is electrically connected to the back surface terminal portion, and the extended portion provided in the wiring direction extends from the back surface terminal portion. It extends. Accordingly, the extension portion extends to a portion closer to the end portion than the tip position of the extension portion, so that bending stress is hardly applied. Therefore, since the bending stress to the wiring located on the end side with respect to the tip of the extension portion can be reduced, disconnection of the wiring can be suppressed. Moreover, since the extension part is a terminal part that is not connected to the wiring and is not used, the terminal part that is not used can be effectively used to reduce stress.

  Further, a protective film may be provided on the back surface of the flexible substrate, and at least a part of the extension may be covered with the protective film. If the extended portion is not covered with the protective film, stress is easily applied to the edge of the protective film, and the stress is concentrated on the wiring located at the edge of the protective film, which may cause disconnection. Therefore, as described above, at least a part of the extended portion is covered with the protective film, so that the extended portion extends to the edge portion of the protective film. Therefore, it is possible to make it difficult for stress to be applied to the wiring located at the edge of the protective film, and it is possible to more reliably suppress the disconnection of the wiring.

  Moreover, the said surface terminal part and the said back surface terminal part may be electrically separated from the other terminal in the edge part of a flexible substrate.

[Details of the embodiment of the present invention]
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
As shown in FIG. 1A and FIG. 1B, a flexible printed circuit board 1 according to the present embodiment is stored in, for example, a housing of an optical transceiver, and is a light emitting unit of the optical transceiver. One light receiving unit is provided for each light receiving unit. In this case, the flexible printed circuit board 1 provided in the light emitting unit connects the light emitting unit and the wiring board provided in the optical transceiver, and the flexible printed circuit board 1 provided in the light receiving unit includes the light receiving unit, the wiring board, and the like. Connect.

  The flexible printed board 1 includes a flexible plate-like portion (flexible board) 2 formed in a flat plate shape. The plate-like portion 2 includes a first edge 2a located at the end A of the plate-like portion 2, a second edge 2b located on the opposite side of the first edge 2a, a front surface 2c, and a back surface 2d. ing.

  In addition, the flexible printed circuit board 1 has, on the surface 2c, terminals 3a to 3g provided at the end A of the plate-like portion 2, electric wiring (wiring) 4 connected to each of the terminals 3a and 3g, and a terminal 3d. And a high-frequency wiring 5 connected to the. Furthermore, the flexible printed circuit board 1 includes terminals 3a to 3g, electrical wiring 6 connected to the terminals 3b and 3f, and ground wiring 7 connected to the terminals 3c and 3e on the back surface 2d. Yes. Seven terminals similar to the terminals 3 a to 3 g are provided on the opposite side of the end portion A of the flexible printed circuit board 1.

  In the plate-like portion 2, the first edge 2a and the second edge 2b extend linearly. The plate-like portion 2 passes through the center of the plate-like portion 2 and extends in the longitudinal direction from the first end edge 2a toward the second end edge 2b. The plate-like portion 2 is formed substantially symmetrically with respect to the axis Ax extending in the longitudinal direction. A first end 2 a is provided at one end in the longitudinal direction of the plate-like portion 2, and a second end edge 2 b is provided at the other end in the longitudinal direction of the plate-like portion 2. Further, the width of the general part B which is a part other than the end part A of the plate-like part 2 is smaller than the width of the end part A. The end A and the general part B are connected by an inclined part 2e that is inclined with respect to the axis Ax.

  The terminals 3a to 3g are made of a conductive material. As shown in FIGS. 1 and 2, the terminals 3a to 3g are electrically connected to each other through via holes in the front surface terminal portion positioned on the front surface 2c and the back surface terminal portion positioned on the back surface 2d. The upper surfaces of the back surface terminal portions of the terminals 3 a to 3 g are soldered to the terminals 10 a on the external mounting substrate 10. That is, the upper surfaces of the back surface terminal portions of the terminals 3 a to 3 g form a connection portion with the mounting substrate 10.

  Further, the terminals 3a to 3g are fixed to the terminal 10a so that the end surface 10b of the mounting substrate 10 coincides with the reference line L when viewed from the thickness direction of the plate-like portion 2. The terminals 3a to 3g are arranged in this order along the first edge 2a. The terminals 3 a to 3 g extend from the first end edge 2 a in the longitudinal direction of the plate-like portion 2 at the end A of the plate-like portion 2.

  On the surface 2c, one ends of the terminals 3a to 3g coincide with the first end edge 2a, and the other ends of the terminals 3a, 3d, and 3g coincide with a reference line L extending in parallel with the first end edge 2a. The reference line L passes through a connection portion C1 between the terminals 3a and 3g and the electric wiring 4, and a connection portion C2 between the terminal 3d and the high-frequency wiring 5. On the surface 2c, the other ends of the terminals 3b, 3c, 3e, and 3f extend from the reference line L to the second end edge 2b side. That is, the terminals 3b, 3c, 3e, and 3f extend from the first end edge 2a to a position that exceeds the reference line L and does not reach the second end edge 2b. In addition, inclined portions 3h, 3j, 3k, and 3m that are inclined with respect to the axis Ax (high-frequency wiring 5) are provided at the other ends of the terminals 3b, 3c, 3e, and 3f, respectively.

  Further, on the back surface 2d, one ends of the terminals 3a to 3g coincide with the first end edge 2a, and the other ends of the terminals 3b, 3d, and 3f coincide with the reference line L. The reference line L passes through the connection portion C3 between the terminals 3b and 3f and the electric wiring 6. On the back surface 2d, the other ends of the terminals 3a and 3g extend from the reference line L to the second edge 2b side. The terminals 3a and 3g extend from the first end edge 2a to a position that exceeds the reference line L and does not reach the second end edge 2b.

  That is, the part from the 1st edge 2a of the terminals 3a and 3g in the back surface 2d to the reference line L is a back surface terminal part. Further, the portion extending from the reference line L of the terminals 3a and 3g on the back surface 2d to the second end edge 2b side is an extension. The other ends of the terminals 3a and 3g are provided with inclined portions 3n and 3p that are inclined with respect to the axis Ax (ground wiring 7), respectively.

  The electrical wiring 4 extends along the side edge of the plate-like portion 2 from the connection portion C1 with the terminals 3a and 3g on the surface 2c, and is located on the opposite side of the end portion A (second end edge 2b). It extends to each terminal. The direction in which the electrical wiring 4 extends is the wiring direction.

  The high-frequency wiring 5 extends linearly along the axis Ax. Specifically, the high-frequency wiring 5 extends linearly from the connection portion C2 to the terminal 3d toward the second end edge 2b on the surface 2c and extends to the terminal located on the opposite side of the end portion A. Exist. The high-frequency wiring 5 is a wiring that transmits a high-frequency signal such as 10 Gbps to 25 Gbps. In the high-frequency wiring 5, impedance matching is performed. Along with this impedance matching, the high-frequency wiring 5 is thinner than the electrical wirings 4 and 6.

  The electrical wiring 6 extends along the side edge of the plate-like portion 2 from the connection portion C3 with the terminals 3b and 3f on the back surface 2d to the terminal located on the opposite side of the end portion A.

  The ground wiring 7 is connected to the terminals 3c and 3e on the back surface 2d. The ground wiring 7 extends from each of the terminals 3c and 3e toward the second edge 2b. The ground wiring 7 extending from the terminal 3c toward the second end edge 2b and the ground wiring 7 extending from the terminal 3e toward the second end edge 2b join in the middle.

  As described above, in the flexible printed circuit board 1, the surface terminal portions of the terminals 3a and 3g connected to the electric wiring 4 on the surface 2c are electrically connected to the back surface terminal portions of the terminals 3a and 3g. And the extended part provided in the wiring direction is extended from the back surface terminal part of terminal 3a, 3g. Accordingly, the extension portion extends to a portion closer to the end portion A than the distal end position P of the extension portions of the terminals 3a and 3g, so that bending stress is hardly applied. Therefore, since the bending stress to the electric wiring 4, the high-frequency wiring 5, and the electric wiring 6 located on the end A side with respect to the distal end position P of the extension portion can be reduced, the electric wiring 4, the high-frequency wiring 5, and the electric wiring are reduced. 6 disconnection can be suppressed. Further, since the extended portions of the terminals 3a and 3g are terminal portions which are not connected to the wiring and are not used, the terminal portions which are not used can be effectively used to reduce stress. The front surface terminal portion and the back surface terminal portion of the terminals 3a and 3g are electrically separated from the other terminals 3b to 3f at the end portion A.

  Moreover, the flexible printed circuit board 1 is provided with the electrical wiring 4 provided in the surface 2c, and the terminals 3a and 3g connected to the electrical wiring 4 by the surface 2c. The terminals 3a and 3g on the back surface 2d extend beyond the reference line L and reach a position that does not reach the second edge 2b. That is, the terminals 3a and 3g on the back surface 2d extend longer to the second edge 2b side than the terminals 3a and 3g on the front surface 2c.

  Further, the flexible printed circuit board 1 includes an electrical wiring 6 and a ground wiring 7 provided on the back surface 2d, terminals 3b and 3f connected to the electrical wiring 6 on the back surface 2d, and terminals connected to the ground wiring 7 on the back surface 2d. 3c, 3e. The terminals 3b, 3c, 3e, and 3f on the surface 2c extend beyond the reference line L and to a position that does not reach the second end edge 2b. That is, the terminals 3b, 3c, 3e, and 3f on the front surface 2c extend longer toward the second edge 2b than the terminals 3b, 3c, 3e, and 3f on the back surface 2d.

  By extending the terminals 3b, 3c, 3e, and 3f to the portion on the first end edge 2a side of the front end position Q on the second end edge 2b side of the terminals 3b, 3c, 3e, and 3f on the surface 2c, Bending stress is difficult to apply. Therefore, the bending stress applied to the electrical wiring 4, the high-frequency wiring 5, and the electrical wiring 6 located on the first edge 2a side of the tip position Q on the second edge 2b side of the terminals 3b, 3c, 3e, and 3f. Since it can reduce, disconnection of the electric wiring 4, the high frequency wiring 5, and the electric wiring 6 can be suppressed. In addition, since the terminals 3b, 3c, 3e, and 3f located on the surface 2c are not connected to the wiring and are not used, the unused terminals can be effectively used to reduce stress.

  Further, the terminals 3 a to 3 g are fixed to the mounting substrate 10 so that the end surface 10 b of the mounting substrate 10 coincides with the reference line L when viewed from the thickness direction of the plate-like portion 2. Here, when the terminals 3a to 3g are fixed to the wiring board so that the reference line L and the end face 10b of the mounting substrate 10 coincide with each other, the electric wiring 4, the high-frequency wiring 5 and the electric wiring 6 located near the reference line L are connected. Bending stress is easily applied. Therefore, as in the present embodiment, the terminals 3a to 3c and 3e to 3g extend beyond the reference line L and extend to the second edge 2b side, so that the electrical wiring 4 and the high-frequency wiring positioned near the reference line L 5 and the electrical wiring 6 can be effectively protected, and disconnection of the electrical wiring 4, the high-frequency wiring 5, and the electrical wiring 6 can be more reliably suppressed.

(Second Embodiment)
FIG. 3 is a plan view showing the flexible printed circuit board 11 according to the second embodiment. The flexible printed circuit board 11 is different from the flexible printed circuit board 1 according to the first embodiment in that it includes an overcoat 12 that functions as a protective film.

  As shown in FIG. 2, the overcoat 12 protects the electrical wiring 4 and the high-frequency wiring 5 by covering the electrical wiring 4 and the high-frequency wiring 5 on the surface 2 c of the plate-like portion 2. The overcoat 12 is made of, for example, a resin and is made of a flexible material. The end side 12 a of the overcoat 12 has a linear shape extending in parallel with the first end edge 2 a of the plate-like portion 2. Further, the end side 12a of the overcoat 12 is located on the second end edge 2b side with respect to the reference line L and on the first end edge 2a side with respect to the tip positions Q of the terminals 3b, 3c, 3e, and 3f. For this reason, a part of the terminal 3b, 3c, 3e, 3f located on the second end edge 2b side from the reference line L is covered with the overcoat 12.

  Similarly, an overcoat 12 is provided on the back surface 2 d of the plate-like portion 2. The overcoat 12 on the back surface 2 d protects the electrical wiring 6 and the ground wiring 7 by covering the electrical wiring 6 and the ground wiring 7. In the back surface 2d, the end side 12a of the overcoat 12 is located closer to the first end edge 2a than the tip position P of the terminals 3a and 3g. For this reason, a part of the part (extension part) located in the 2nd edge 2b side from the reference line L in terminal 3a, 3g is covered with the overcoat 12. FIG.

  As described above, the overcoat 12 is provided on the back surface 2 d of the plate-like portion 2, and the extension portion is covered with the overcoat 12. If the terminals 3a and 3g are not covered with the overcoat 12, stress is easily applied to the end side 12a of the overcoat 12, and stress is concentrated on the electrical wiring 6 and the ground wiring 7 located on the end side 12a. It may cause disconnection. Therefore, when at least a part of the extension is covered with the overcoat 12 as in the present embodiment, the terminals 3a and 3g extend to the end side 12a. Therefore, it is possible to make it difficult for stress to be applied to the end side 12a, and it is possible to more reliably suppress disconnection of the electric wiring 6 and the ground wiring 7.

  The same effect as described above can also be obtained from the overcoat 12 provided on the surface 2c of the plate-like portion 2. That is, disconnection of the electrical wiring 4 and the high-frequency wiring 5 can be more reliably suppressed by the same operation as the above-described operation.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The flexible printed board according to the present invention is not limited to the above embodiment, and various other modifications are possible.

  For example, in the above embodiment, the plate-like portion 2 is formed substantially symmetrically with respect to the axis Ax extending in the longitudinal direction. However, the plate-like portion may not be formed substantially symmetrical, and the shape of the plate-like portion 2 is It can be changed as appropriate. For example, the first edge 2a and the second edge 2b may be curved. In addition, the shape of the overcoat 12 can be changed as appropriate.

  Furthermore, although each flexible printed board mentioned above was provided with the seven terminals 3a-3g along the 1st edge 2a, the number of terminals may be 6 or less, or 8 or more. Moreover, in the said embodiment, although the end of the terminal corresponded to the 1st edge 2a, it does not need to correspond.

DESCRIPTION OF SYMBOLS 1,11 ... Flexible printed circuit board, 2 ... Plate-shaped part (flexible board), 2a ... 1st edge, 2b ... 2nd edge, 2c ... Surface, 2d ... Back surface, 2e ... Inclined part, 3a-3g ... Terminal 4, 6 ... Electrical wiring, 5 ... High frequency wiring, 7 ... Ground wiring, 10 ... Mounting substrate, 10a ... Terminal, 10b ... End face, 12 ... Overcoat (protective film), 12a ... End side, A ... End part, Ax ... axis, B ... general part, C1-C3 ... connecting part, L ... reference line, P, Q ... tip position.

Claims (3)

A flexible substrate;
In the end portion of the flexible substrate, a surface terminal portion provided on the surface side,
In the end portion of the flexible substrate, provided on the back surface side, electrically connected to the surface terminal portion, the back surface terminal portion whose upper surface forms a connection portion with the mounting substrate,
On the surface side of the flexible substrate, wiring connected to the surface terminal portion,
On the back side of the flexible substrate, connected to the back terminal part, and an extension provided to extend from the back terminal part in the wiring direction,
Flexible printed circuit board with A protective film is provided on the back surface of the flexible substrate, and at least a part of the extension is covered with the protective film.
The flexible printed circuit board according to claim 1. The front surface terminal portion and the back surface terminal portion are electrically separated from other terminals at the end of the flexible substrate.
The flexible printed circuit board of Claim 1 or 2.

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