JP2012033670A - Flexible printed circuit board and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible printed circuit board capable of facilitating detection of a break in a signal wiring as well as an outmost wiring on a substrate.SOLUTION: A flexible printed circuit board 3 includes a signal wiring 37 electrically used and a dummy wiring 38 isolated from the signal wiring 37 formed on a substrate 34. The dummy wiring 38 has a structure that tends to break more easily than the signal wiring 38. The present invention provides a flexible printed circuit board capable of facilitating detection of such a break.

Description

  The present invention relates to a flexible printed circuit board and an electronic device.

  Conventionally, the disconnection of the wiring pattern on the flexible printed circuit board is often not visually recognized, and it has been necessary to actually check the disconnection by operating the device.

  On the other hand, for example, in Patent Document 1, the outermost two wiring patterns among a plurality of wiring patterns made of copper foil or the like extending in parallel with each other along the longitudinal direction of the surface of the flexible printed circuit board are exclusively used for disconnection detection. A cable disconnection detection device is disclosed that uses the other wiring pattern as a signal wiring pattern. This disconnection detection apparatus pays attention to the fact that the outermost wiring among the plurality of wiring patterns formed on the substrate is easily disconnected, and uses the outermost wiring as a wiring pattern dedicated to disconnection detection.

Japanese Patent Laid-Open No. 9-211052

  However, in the above-described disconnection detecting device, in the flexible printed circuit board used in a state where the wiring is curved together with the substrate, the outermost wiring is not always most easily disconnected, and particularly in a curved portion, There was a problem that wirings other than the outside were also easily disconnected.

  Accordingly, an object of the present invention is to provide a flexible printed circuit board that can easily detect disconnection of signal wiring, not limited to the outermost wiring on the board.

In order to solve the above problems, according to one aspect of the present invention,
In a flexible printed circuit board in which a signal wiring used electrically and a dummy wiring insulated from the signal wiring are formed on the substrate,
The flexible printed circuit board is characterized in that the dummy wiring has a structure that is more easily broken with respect to bending than the signal wiring.

In the flexible printed circuit board, preferably, the dummy wiring includes nickel gold plating.
In the flexible printed board, preferably, the nickel gold plating includes a nickel layer in direct contact with the dummy wiring and a gold layer formed on the nickel layer.
In the flexible printed board, preferably, the nickel gold plating includes a gold layer in direct contact with the dummy wiring and a nickel layer formed on the gold layer.
In the flexible printed circuit board, preferably, the terminal connected to the signal wiring includes direct gold plating.
In the flexible printed circuit board, preferably, a plurality of the dummy wirings and the signal wirings are formed,
A distance between the plurality of dummy wirings is smaller than a distance between the plurality of signal wirings.
In the flexible printed circuit board, preferably, the dummy wiring includes a first dummy wiring formed adjacent to a first signal wiring forming region where the signal wiring is likely to be disconnected on the substrate, and the dummy wiring on the substrate. A second dummy wiring formed adjacent to the second signal wiring formation region, which is less likely to cause disconnection of the signal wiring than the first signal wiring formation region,
The second dummy wiring has a structure that is easier to break with respect to bending than the first dummy wiring.
In the flexible printed circuit board, it is preferable that the second dummy wiring is formed narrower than the first dummy wiring.
In the flexible printed circuit board, preferably, an angle formed by a direction in which the second dummy wiring extends and a direction in which the substrate is bent is an angle between the direction in which the first dummy wiring extends and the substrate is curved. It is smaller than the angle formed by the direction.
In the flexible printed circuit board, preferably, the dummy wiring is formed in each of a plurality of regions arranged along a direction intersecting a direction in which the substrate is curved,
The signal wiring is disposed between each of the plurality of regions,
The first dummy wiring is formed in one region of the plurality of regions, and the second dummy wiring is formed in another region of the plurality of regions.
In the flexible printed circuit board, preferably, the dummy wiring is formed in each of a plurality of regions arranged along a direction intersecting a direction in which the substrate is curved,
The signal wiring is disposed between the plurality of regions.
In the flexible printed board, preferably, a plurality of the dummy wirings are formed in each of the plurality of regions.
In the flexible printed board, preferably, the visual difference between the dummy wiring and the substrate is larger than the visual difference between the signal wiring and the substrate.
In the flexible printed board, preferably, when the portion of the substrate on which the signal wiring is formed is in a curved state, the portion of the substrate on which the dummy wiring is formed is also in a curved state.
In the flexible printed circuit board, preferably, the dummy wiring is formed in a curved portion at the time of manufacture or use.

According to another aspect of the invention,
An electronic device comprising the flexible printed circuit board and an electronic device main body,
An electronic device is provided, wherein the flexible printed circuit board is attached to the electronic device main body in a state where the portion of the substrate where the dummy wiring is formed is curved.

  In the electronic device, preferably, the electronic device main body is a display panel or a touch panel having a transparent substrate to which the flexible printed circuit board is connected.

  According to the present invention, a dummy wiring that is easier to break with respect to bending than a signal wiring is provided on a substrate, and the disconnection of the signal wiring is easily detected by checking whether or not the dummy wiring is disconnected. be able to.

It is a front perspective view of an electronic device provided with the flexible printed circuit board concerning a 1st embodiment. It is a back perspective view of an electronic device. It is a front view of a flexible printed circuit board. It is a schematic cross section of the flexible printed circuit board of the part in which the output terminal, the input terminal, or the dummy wiring was formed. 4A is an enlarged schematic cross-sectional view of the Va portion in FIG. 4 in the portion where the output terminal or the input terminal is formed, and FIG. 4B is an enlarged schematic cross-sectional view of the Va portion in FIG. 4 in the portion where the dummy wiring is formed. It is. It is a model front view of the flexible printed circuit board concerning a 2nd embodiment.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated using drawing. However, each embodiment described below is provided with various technically preferable limitations for carrying out the present invention, but the scope of the invention is not limited to the following embodiments and illustrated examples.

<First Embodiment>
FIG. 1 is a front perspective view of the electronic device 100, FIG. 2 is a rear perspective view of the electronic device 100, and FIG. 3 is a front view showing the flexible printed circuit board 3 in an uncurved state. As shown in FIGS. 1 and 2, the electronic device 100 includes a display panel (electronic device main body) 1, a housing 2, a flexible printed circuit board 3, and the like. 1 and 2, the signal wiring 37 and various terminals of the flexible printed circuit board 3 are omitted.

  The display panel 1 is a liquid crystal display panel configured such that a first transparent substrate 4 and a second transparent substrate 5 are disposed to face each other with a liquid crystal layer (not shown) interposed therebetween. First and second transparent electrodes (not shown) are provided on the inner surfaces of the first transparent substrate 4 and the second transparent substrate 5 facing each other. The first and second transparent electrodes form a plurality of pixels in a matrix form that control the transmission of light by changing the alignment state of the liquid crystal molecules in the liquid crystal layer by applying a voltage. A polarizing plate 6 is attached to the front surface of the second transparent substrate 5 located on the observation side. On the first transparent substrate 4 located on the rear surface side, an overhanging portion 41 that projects from the second transparent substrate 5 is formed. A display drive circuit 7 for applying a drive voltage between the transparent electrodes is mounted on the overhanging portion 41.

  The display panel 1 may not be a liquid crystal display panel, but may be an EL (Electro Luminescence) display panel, a PDP (Plasma Display Panel) display panel, an OLED (Organic light-Emitting Diode) display panel, or the like. In addition, the electronic device 100 may include a touch panel according to various methods including a capacitance method instead of the display panel 1.

  The housing 2 is a plate-like substantially box-shaped member that accommodates the display panel 1 inside. The casing 2 has a rectangular plate-like bottom plate 22 and three side walls 23a erected with respect to the bottom plate 22 from the remaining three sides excluding one side along the projecting portion 41 among the four sides of the bottom plate 22. , 23b and 23c. Of the four side surfaces of the substantially rectangular display panel 1, one side surface along the projecting portion 41 is exposed without being covered by the housing 2, and the remaining three side surfaces excluding the one side surface are three side walls. The display panel 1 is disposed in the housing 2 so as to face the 23a, 23b, and 23c, respectively. The entire front surface of the display panel 1 is exposed without being covered by the housing 2.

  The flexible printed circuit board 3 is curved and provided so as to overlap a part of the front surface and a part of the rear surface of the electronic device 100. That is, one end 31 of the flexible printed circuit board 3 is connected to the overhanging section 41 of the display panel 1 (see FIG. 1), and the other end 32 of the flexible printed circuit board 3 is disposed on the rear surface of the housing 2 (FIG. 2). reference). The curved portion 33 of the flexible printed circuit board 3 covers a part of the side surface of the bottom plate 22 of the housing 2. Here, the direction in which the flexible printed circuit board 3 is curved is defined as the X direction.

As shown in FIG. 3, the flexible printed circuit board 3 is configured by providing an output terminal 35, an input terminal 36, a signal wiring 37, a dummy wiring 38, and other various terminals on a flexible substrate 34. Yes.
The substrate 34 forms the main body of the flexible printed circuit board 3. An output terminal 35 is formed on the substrate 34 on the one end 31 side in the X direction of the flexible printed circuit board 3, and an input terminal 36 is formed on the other end 32 side in the X direction. By connecting the output terminal 35 to a connection terminal (not shown) formed on the overhanging portion 41, the one end portion 31 of the flexible printed circuit board 3 is fixed.
And the signal wiring 37 formed on the board | substrate 34 is a wiring pattern which electrically connects between the output terminal 35, the input terminal 36, and other various terminals. Direct gold plating 56 is applied to the output terminal 35 and the input terminal 36.

  In addition, a plurality of regions 341 to 344 in which the signal wiring 37 is not formed are provided on the substrate 34. As shown in FIGS. 1 and 2, the regions 341 to 344 are located in the curved portion 33 of the flexible printed circuit board 3 and are arranged along a direction substantially orthogonal to the X direction. A signal wiring 37 is disposed between the regions 341 to 344.

The dummy wiring 38 is a wiring pattern electrically insulated from the signal wiring 37 and is not connected to any terminal on the substrate 34. Therefore, even if the dummy wiring 38 is disconnected, the function of the flexible printed circuit board 3 is not affected at all.
A plurality of such dummy wirings 38 are provided in the regions 341 to 344 of the substrate 34 and extend along the X direction. The dummy wiring 38 is provided with nickel gold plating 57, and the nickel gold plating 57 has a structure that is easier to break than the signal wiring 37 with respect to bending.

  Further, the appearance of the dummy wiring 38 is formed so that the visual difference between the dummy wiring 38 and the substrate 34 is larger than the visual difference between the signal wiring 37 and the substrate 34. Here, the visual difference may be due to a light / dark ratio (contrast) or may be due to a difference in color tone. This makes it easier to visually recognize when the dummy wiring 38 is disconnected.

  Here, the regions 341 and 344 of the flexible printed circuit board 3 are adjacent to a portion (first signal wiring forming region) where the signal wiring 37 is easily disconnected on the substrate 34, and the regions 342 and 343 are on the substrate 34. , It is assumed that the signal wiring 37 is adjacent to a portion (second signal wiring forming region) where it is difficult to disconnect. First dummy wirings 381 and 384 having a large width are formed in the regions 341 and 344, and second dummy wirings 382 and 383 having a small width are formed in the regions 342 and 343. The narrower the width, the easier the dummy wiring 38 is to break with respect to bending, so the second dummy wirings 382 and 383 have a structure that is easier to break than the first dummy wirings 381 and 384. The width of the dummy wiring means a length along a direction orthogonal to the direction in which the dummy wiring is extended.

FIG. 4 is a cross-sectional view of the flexible printed circuit board 3 where the output terminal 35, the input terminal 36, or the dummy wiring 38 is formed, and FIG. 5A is a portion where the output terminal 35 or the input terminal 36 is formed. 4 is an enlarged cross-sectional view of the Va portion of FIG. 4, and FIG. 5B is an enlarged cross-sectional view of the Va portion of FIG. 4 in the portion where the dummy wiring 38 is formed.
The flexible printed circuit board 3 is provided with signal wirings 37 and dummy wirings 38 by patterning copper foils 53A and 53B formed on both surfaces of a base material 51 made of polyimide via adhesives 52A and 52B. . Further, the coverlay is formed so as to cover the copper foils 53A and 53B and the base material 51 and to expose the copper foils 53A and 53B in the portions of the copper foils 53A and 53B which become the output terminal 35, the input terminal 36 and the dummy wiring 38. 55A and 55B are provided via adhesives 54A and 54B.
Of the copper foil 53A exposed from the cover lay 55A, a portion corresponding to the output terminal 35 and the input terminal 36 is subjected to direct gold plating 56 so as to be in direct contact with the copper foil 53A, and the copper exposed from the cover lay 55A. A portion of the foil 53A corresponding to the dummy wiring 38 is provided with a nickel gold plating 57 so as to be in direct contact with the copper foil 53A. The nickel gold plating 57 may be provided so that the nickel layer 57a is in direct contact with the copper foil 53A, or may be provided so that the gold layer 57b is in direct contact with the copper foil 53A.

A method for forming the direct gold plating 56 and the nickel gold plating 57 will be described below.
In the copper foil 53A exposed from the cover lay 55A, a portion of the copper foil 53A corresponding to the output terminal 35 and the input terminal 36 is covered and a mask (not shown) exposing the portion corresponding to the dummy wiring 38 is formed. A nickel layer 57a is formed by a plating method. Next, a gold layer 57b is formed by electrolytic plating in a state where a mask (not shown) exposing portions corresponding to the output terminal 35, the input terminal 36, and the dummy wiring 38 is formed. As a result, of the copper foil 53A exposed from the cover lay 55A, a portion corresponding to the output terminal 35 and the input terminal 36 is subjected to the direct gold plating 56 so as to directly contact the copper foil 53A, and corresponds to the dummy wiring 38. The portion is in a state where nickel gold plating 57 is applied so as to directly contact the copper foil 53A. By this method, the nickel gold plating 57 in which the nickel layer 57a and the gold layer 57b are formed in this order from the copper foil 53A side is formed.
In the state where a mask (not shown) for exposing portions corresponding to the output terminal 35, the input terminal 36, and the dummy wiring 38 in the copper foil 53A exposed from the coverlay 55A is formed, a gold layer is formed by electrolytic plating. 57b is formed, and then a nickel layer is formed by electrolytic plating in a state in which a mask (not shown) that covers portions corresponding to the output terminals 35 and the input terminals 36 and exposes portions corresponding to the dummy wirings 38 is formed. By forming 57a, a nickel gold plating 57 in which a gold layer 57b and a nickel layer 57a are formed in this order from the copper foil 53A side may be formed.

As described above, according to the present embodiment, the dummy wiring 38 is formed in the curved portion of the flexible printed circuit board 3, and the nickel wiring 57 is applied to the dummy wiring 38, so that the direct gold plating 56 is applied. The signal wiring 37 is more easily broken than the signal wiring 37. As a result, the dummy wiring 38 is disconnected before the signal wiring 37 is disconnected. By checking whether the dummy wiring 38 is disconnected, it is easy to determine whether the signal wiring 37 is disconnected. Can be detected.
Further, since the visual difference between the dummy wiring 38 and the substrate 34 is larger than the visual difference between the signal wiring 37 and the substrate 34, it becomes easy to visually recognize when the dummy wiring 38 is disconnected. ing.
Furthermore, according to the present embodiment, the first dummy wirings 381 and 384 having a large width are disposed adjacent to the portion where the signal wiring 37 is likely to be disconnected on the substrate 34, so that the signal wiring 37 is not easily disconnected. Adjacent and narrow second dummy wirings 382 and 383 are arranged. Here, the dummy wiring 38 is more likely to be broken with respect to bending as the width is thinner, and is more difficult to break as the width is larger. Therefore, by adjusting the width of the dummy wiring 38, the strength against bending of the dummy wiring 38 can be adjusted, and the disconnection detection ability can be made uniform between the part on the substrate 34 that is easily disconnected and the part that is difficult to disconnect. can do.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to FIG. The parts corresponding to those of the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

FIG. 6 is a front view schematically showing a part of the flexible printed circuit board 3a according to the second embodiment.
In the flexible printed circuit board 3a according to the second embodiment, the widths of the plurality of dummy wirings 38a formed in the respective regions 341 to 344 are uniform, and are each extended with an inclination with respect to the X direction. The slopes of the plurality of dummy wirings 38a differ depending on the region where they are formed. That is, the first dummy wirings 381a and 384a having a large degree of inclination are formed in regions 341 and 344 adjacent to portions where the signal wiring 37 is easily disconnected on the substrate 34a. In addition, second dummy wirings 382a and 383a having a small inclination are formed in regions 342 and 343 adjacent to portions where the signal wiring 37 is difficult to be disconnected. The smaller the inclination with respect to the X direction, the easier the dummy wiring 38 is to be disconnected with respect to bending, so the second dummy wirings 382a and 383a are more easily disconnected than the first dummy wirings 381a and 384a.
The second dummy wirings 382a and 383a do not have to be inclined with respect to the X direction, and may extend in parallel to the X direction. That is, the angle formed by the direction in which the second dummy wirings 382a and 383a extend and the direction X in which the flexible printed circuit board 3a is curved is the same as the direction in which the first dummy wirings 381a and 384a extend and the flexible printed circuit board 3a is curved. It is preferable that the angle is smaller than the angle formed by the direction to be formed.

  Further, the distance between the plurality of dummy wirings 38 a formed in each of the regions 341 to 344 is smaller than the distance between the plurality of signal wirings 37. That is, the plurality of dummy wirings 38a are densely arranged.

As mentioned above, according to 2nd Embodiment, while there exists an effect similar to the above-mentioned 1st Embodiment, there exist the following effects.
According to the present embodiment, the first dummy wirings 381a and 384a having a large inclination with respect to the X direction are arranged on the substrate 34a near the portion where the signal wiring 37 is likely to be disconnected, and the signal wiring 37 is not easily disconnected. Near the location, second dummy wirings 382a and 383a having a small inclination with respect to the X direction are arranged. The dummy wiring 38a is more likely to be disconnected with respect to the bending in the X direction as the inclination with respect to the X direction is smaller, and is more difficult to be disconnected with respect to the bending in the X direction as the inclination with respect to the X direction is larger. Therefore, by adjusting the inclination of the direction in which the dummy wiring 38a extends with respect to the X direction, the strength against bending of the dummy wiring 38a can be adjusted, and the portion on the substrate 34a that is easily broken and the portion that is difficult to break. Can make the disconnection detection ability uniform.
Further, since the plurality of dummy wirings 38a are densely arranged, when the dummy wirings 38a are disconnected, the plurality of dummy wirings 38a are simultaneously disconnected. Thereby, the disconnection part becomes a line shape, and the occurrence of the disconnection is more easily detected.

In each of the above-described embodiments, the dummy wiring is provided in a portion (curved portion 33) that is bent during use in the flexible printed board. However, the dummy wiring may be provided in a portion that is bent during manufacture. Good. Here, “manufacturing” means during the manufacturing process of the flexible printed circuit board itself or during the manufacturing process of the electronic device including the flexible printed circuit board.
Further, the regions 341 to 344 of the flexible printed circuit board 3 may not be necessarily orthogonal to the X direction, but may be arranged along a direction that obliquely intersects the X direction. Furthermore, a plurality of dummy wirings 38 are not necessarily provided in each of the regions 341 to 344 of the substrate 34, and only one dummy wiring 38 may be provided in any of the regions 341 to 344 of the substrate 34.

1 Display panel (electronic equipment body)
2 Housing 3 Flexible printed circuit board 4 First transparent substrate 5 Second transparent substrate 35 Output terminal (terminal)
36 Input terminal (terminal)
37 Signal wiring 38 Dummy wiring 56 Direct gold plating 57 Nickel gold plating 57a Nickel layer 57b Gold layer 100 Electronic equipment 381, 381a First dummy wiring 382, 382a Second dummy wiring 383, 383a First dummy wiring 384, 384a Second dummy wiring

Claims (17)

In a flexible printed circuit board in which a signal wiring used electrically and a dummy wiring insulated from the signal wiring are formed on the substrate,
The flexible printed circuit board, wherein the dummy wiring has a structure that is easier to break with respect to bending than the signal wiring.   The flexible printed circuit board according to claim 1, wherein the dummy wiring includes nickel gold plating.   3. The flexible printed circuit board according to claim 2, wherein the nickel gold plating includes a nickel layer in direct contact with the dummy wiring and a gold layer formed on the nickel layer.   3. The flexible printed circuit board according to claim 2, wherein the nickel gold plating includes a gold layer in direct contact with the dummy wiring and a nickel layer formed on the gold layer.   The flexible printed circuit board according to any one of claims 1 to 4, wherein the terminal connected to the signal wiring includes direct gold plating. A plurality of the dummy wirings and the signal wirings are formed,
6. The flexible printed circuit board according to claim 1, wherein a distance between the plurality of dummy wirings is smaller than a distance between the plurality of signal wirings. The dummy wiring includes a first dummy wiring formed adjacent to a first signal wiring forming region where the disconnection of the signal wiring is likely to occur on the substrate, and the first signal wiring forming region on the substrate than the first signal wiring forming region. A second dummy wiring formed adjacent to the second signal wiring forming region where the signal wiring is less likely to be disconnected,
The flexible printed circuit board according to any one of claims 1 to 6, wherein the second dummy wiring has a structure that is easier to break with respect to bending than the first dummy wiring.   The flexible printed circuit board according to claim 7, wherein the second dummy wiring is formed thinner than the first dummy wiring.   The angle formed by the direction in which the second dummy wiring extends and the direction in which the substrate is bent is smaller than the angle formed by the direction in which the first dummy wiring extends and the direction in which the substrate is bent. A flexible printed circuit board according to claim 5 or 6. The dummy wirings are respectively formed in a plurality of regions arranged along a direction intersecting a direction in which the substrate is curved.
The signal wiring is disposed between each of the plurality of regions,
The first dummy wiring is formed in one region of the plurality of regions, and the second dummy wiring is formed in another region of the plurality of regions. The flexible printed circuit board as described in any one. The dummy wirings are respectively formed in a plurality of regions arranged along a direction intersecting a direction in which the substrate is curved.
The flexible printed circuit board according to any one of claims 1 to 10, wherein the signal wiring is arranged between the plurality of regions.   The flexible printed circuit board according to claim 10, wherein a plurality of the dummy wirings are formed in each of the plurality of regions.   The flexible printed circuit board according to claim 1, wherein a visual difference between the dummy wiring and the substrate is larger than a visual difference between the signal wiring and the substrate. .   The portion of the substrate where the signal wiring is formed is in a curved state, and the portion of the substrate where the dummy wiring is formed is also in a curved state. A flexible printed circuit board according to the item.   The flexible printed circuit board according to any one of claims 1 to 14, wherein the dummy wiring is formed in a portion that is curved during manufacture or use. An electronic device comprising the flexible printed circuit board according to any one of claims 1 to 15 and an electronic device main body,
The electronic device, wherein the flexible printed circuit board is attached to the main body of the electronic device in a state where the portion of the substrate where the dummy wiring is formed is curved.   The electronic device according to claim 16, wherein the electronic device main body is a display panel or a touch panel having a transparent substrate to which the flexible printed circuit board is connected.

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