Flexible printed circuit board

Abstract

To provide a flexible printed circuit board with a more reliable structure.SOLUTION: A flexible printed circuit board comprises a base material 10, a conductor layer 20 printed and formed on the base material 10, and an insulation cover layer 30 formed on the base material 10 and covering a part of the conductor layer 20. The conductor layer 20 has a wiring part 50 and an electrode part 60 connected to the wiring part 50. The insulation cover layer 30 has an opening 33 exposing a part of the electrode part 60. A film thickness T1 at a part where the inner peripheral edge 33a of the opening 33 overlaps in plan view on the electrode part 60 is greater than a film thickness T2 at the central part 60a of the electrode part 60.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a flexible printed circuit board. [Background technology]

[0002] There is a flexible printed circuit board in which a conductor layer formed on a substrate has a wiring portion and an electrode portion connected to the wiring portion, and an insulating cover layer formed on the substrate has an opening that exposes a portion of the electrode portion (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-20667 Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to the investigations of the present inventors, defects such as cracks and breaks may occur in the conductor layer at the locations corresponding to the inner periphery of the opening in the insulating cover layer, which may affect the yield.

[0005] The present invention has been made in view of the above problems, and aims to provide a flexible printed circuit board having a more reliable structure. [Means for solving the problem]

[0006] According to the present invention, a substrate and a conductor layer formed by printing on the substrate; an insulating cover layer formed on the substrate and covering a portion of the conductor layer; Equipped with the conductor layer has a wiring portion and an electrode portion connected to the wiring portion, the insulating cover layer has an opening that exposes a portion of the electrode portion; The flexible printed circuit board has a thickness in the electrode portion at a portion where the inner periphery of the opening overlaps in a plan view that is greater than the thickness in the center of the electrode portion. [Effects of the Invention]

[0007] According to the present invention, a flexible printed circuit board can be made to have a more reliable structure. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a plan view showing an electrode portion of a flexible printed circuit board according to an embodiment and a structure of the electrode portion and its surroundings. [Figure 2] 2(a) is a cross-sectional view taken along line AA in FIG. 1, and FIG. 2(b) is a cross-sectional view taken along line BB in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, showing a state in which release films are attached to the front and back of the flexible printed circuit board. [Figure 4] FIG. 1 is a plan view of a flexible printed circuit board according to an embodiment. [Figure 5] 10 is a plan view showing the structure of an electrode portion and its periphery of a flexible printed circuit board according to Modification 1. FIG. [Figure 6] 10 is a plan view showing the structure of an electrode portion and its periphery of a flexible printed circuit board according to Modification 2. FIG. [Figure 7] 11 is a plan view showing the structure of an electrode portion and its periphery of a flexible printed circuit board according to Modification 3. FIG. [Figure 8] FIG. 8(a) is a plan view showing the structure of an electrode portion and its periphery of a flexible printed circuit board according to Modification 4, and FIG. 8(b) is a cross-sectional view taken along line AA in FIG. 8(a). DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments and modifications of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and the description thereof will be omitted where appropriate.

[0010] First, an embodiment will be described with reference to FIGS. As shown in Figures 1, 2(a) and 2(b), the flexible printed circuit board 100 (Figure 4) according to this embodiment comprises a substrate 10, a conductor layer 20 printed on the substrate 10, and an insulating cover layer 30 formed on the substrate 10 and covering a portion of the conductor layer 20. Here, the insulating cover layer 30 may be composed of only the main cover layer 31 , or may be composed of the main cover layer 31 and a release film 32 . The conductor layer 20 has a wiring portion 50 and an electrode portion 60 connected to the wiring portion 50. Therefore, the electrode portion 60 is electrically and mechanically connected to the wiring portion 50. The insulating cover layer 30 has an opening 33 that exposes a portion of the electrode portion 60. That is, a portion of the electrode portion 60 is exposed through the opening 33. The thickness T1 (FIG. 2(a)) of the electrode portion 60 at a portion where the inner peripheral edge 33a of the opening 33 overlaps in a plan view is larger than the thickness T2 (FIG. 2(a)) of the central portion 60a of the electrode portion 60.

[0011] Since the thickness T1 is larger than the thickness T2, the structural strength of the portion of the electrode portion 60 that overlaps with the inner peripheral edge 33a of the opening 33 in a plan view can be sufficiently ensured, and it is therefore possible to suitably prevent defects such as cracks and breaks from occurring in that portion. In other words, the flexible printed circuit board 100 can have a more reliable structure.

[0012] This will be explained in more detail below. In this embodiment, the electrode portion 60 has an exposed electrode portion 61 disposed inside the opening 33 and a peripherally disposed portion 62 extending along the inner peripheral edge 33 a of the opening 33 . The portion of the electrode portion 60 that overlaps with the inner peripheral edge 33a of the opening 33 in plan view is the portion of the peripheral arrangement portion 62 that overlaps with the inner peripheral edge 33a of the opening 33 in plan view, and the central portion 60a of the electrode portion 60 is the central portion 61a of the exposed electrode portion 61. In other words, the film thickness T1 of the portion of the peripheral arrangement portion 62 that overlaps with the inner peripheral edge 33a of the opening 33 in plan view is greater than the film thickness T2 of the central portion 61a of the exposed electrode portion 61.

[0013] 1, the exposed electrode portion 61 is entirely disposed inside the opening 33. Therefore, the exposed electrode portion 61 is exposed through the opening 33. There are no particular limitations on the planar shape of the exposed electrode portion 61. As an example, in this embodiment, the planar shape of the exposed electrode portion 61 is rectangular (e.g., rectangular with rounded corners) as shown in Fig. 1. However, the planar shape of the exposed electrode portion 61 may be square, or may be any other polygonal shape, or may be circular, elliptical, or the like.

[0014] The planar shape of the opening 33 is not particularly limited. For example, it may be a shape similar to but slightly larger than the exposed electrode portion 61. For this reason, in this embodiment, the planar shape of the opening 33 is a rectangle with rounded corners.

[0015] In this embodiment, the peripheral arrangement portion 62 extends linearly along the inner peripheral edge 33a of the opening 33. However, in the present invention, the shape of the peripheral arrangement portion 62 is not limited to this example, and it is sufficient that the peripheral arrangement portion 62 is arranged so as to overlap the inner peripheral edge 33a of the opening 33 in a plan view.

[0016] In this embodiment, the peripheral arrangement portion 62 extends in a circumferential (annular) shape along the inner peripheral edge 33a of the opening 33. More specifically, it extends along the entire circumference of the inner peripheral edge 33a of the opening 33. Therefore, in this embodiment, the planar shape of the peripheral arrangement portion 62 is a rectangular annular shape with rounded corners.

[0017] In this embodiment, the peripheral arrangement portion 62 includes a first peripheral arrangement portion 62a, a second peripheral arrangement portion 62b, a third peripheral arrangement portion 62c, and a fourth peripheral arrangement portion 62d, which extend along the four sides of the exposed electrode portion 61, respectively. The first peripheral portion 62a extends along the left side of the exposed electrode portion 61 in FIG. The second peripheral portion 62b extends along the right side of the exposed electrode portion 61 in FIG. The third peripheral portion 62c extends along the upper side of the exposed electrode portion 61 in FIG. The fourth peripheral portion 62d extends along the lower side of the exposed electrode portion 61 in FIG. The first peripheral arrangement portion 62a, the second peripheral arrangement portion 62b, the third peripheral arrangement portion 62c, and the fourth peripheral arrangement portion 62d are connected to one another and collectively form the annular peripheral arrangement portion 62. The peripheral arrangement portion 62 surrounds the periphery of the exposed electrode portion 61 in an annular shape. Here, in a plan view, the inner peripheral edge 33a of the opening 33 is disposed between the outer peripheral edge and the inner peripheral edge of the peripheral arrangement portion 62. In other words, the peripheral arrangement portion 62 exists in a range spanning the inner peripheral edge 33a of the opening 33 from the inside to the outside.

[0018] In this embodiment, the wiring portion 50 is connected to the peripheral arrangement portion 62, and is connected to the exposed electrode portion 61 via the peripheral arrangement portion 62 and a connection portion 64, which will be described later. The wiring portion 50 is connected to the first peripheral portion 62a at a connection point 70, for example. The connection point 70 is a connection point between the wiring portion 50 and the electrode portion 60 (including the exposed electrode portion 61 and the peripheral portion 62). More specifically, the connection point 70 is, for example, the center of the first peripheral portion 62a in the longitudinal direction. However, the present invention is not limited to this example, and the connection point 70 between the wiring portion 50 and the electrode portion 60 may be located at another position.

[0019] Here, the first peripheral portion 62a extends across the connection points 70 in a direction intersecting the direction in which the wiring portion 50 extends (the left-right direction in FIG. 1). That is, in this embodiment, the peripheral arrangement portion 62 includes a cross-direction extending portion (first peripheral arrangement portion 62a) that extends across the connection point 70 between the wiring portion 50 and the electrode portion 60 in a direction that intersects with the wiring portion 50. Therefore, the first peripheral portion 62a can reinforce the connection point 70 and its surroundings, making it possible to suitably prevent problems such as cracks and breaks at the connection point.

[0020] The electrode portion 60 has a connection portion 64 that connects the peripheral arrangement portion 62 and the exposed electrode portion 61 . The electrode portion 60 preferably has a plurality of connection portions 64, which can improve the reliability of the electrical connection between the peripheral arrangement portion 62 and the exposed electrode portion 61. In particular, it is preferable to have one or more (preferably two or more) of the following connecting portions 64 (first connecting portion 64a and second connecting portion 64b described below) connecting the peripheral arrangement portion 62 and the exposed electrode portion 61 in a first direction (for example, the left-right direction in FIG. 1) and the following connecting portions 64 (third connecting portion 64c and fourth connecting portion 64d described below) connecting the peripheral arrangement portion 62 and the exposed electrode portion 61 in a second direction (for example, the up-down direction in FIG. 1). This can further improve the reliability of the electrical connection between the peripheral arrangement portion 62 and the exposed electrode portion 61.

[0021] In this embodiment, the connection portion 64 includes a first connection portion 64a connecting the first peripheral arrangement portion 62a and the exposed electrode portion 61, a second connection portion 64b connecting the second peripheral arrangement portion 62b and the exposed electrode portion 61, a third connection portion 64c connecting the third peripheral arrangement portion 62c and the exposed electrode portion 61, and a fourth connection portion 64d connecting the fourth peripheral arrangement portion 62d and the exposed electrode portion 61. More specifically, the first connecting portion 64a, the second connecting portion 64b, the third connecting portion 64c, and the fourth connecting portion 64d each connect a central portion in the longitudinal direction of the corresponding peripheral arrangement portion 62 to the exposed electrode portion 61. The first connecting portion 64a extends from the first peripheral arrangement portion 62a to the right in FIG. 1 and connects the first peripheral arrangement portion 62a and the exposed electrode portion 61 in the left-right direction in FIG. 1. The second connecting portion 64b extends from the second peripheral arrangement portion 62b to the left in FIG. 1 and connects the second peripheral arrangement portion 62b and the exposed electrode portion 61 in the left-right direction in FIG. 1. The third connecting portion 64c extends from the third peripheral arrangement portion 62c downward in FIG. 1 and connects the third peripheral arrangement portion 62c and the exposed electrode portion 61 in the up-down direction in FIG. 1. The fourth connection portion 64d extends upward in Fig. 1 from the fourth peripheral arrangement portion 62d, and connects the fourth peripheral arrangement portion 62d and the exposed electrode portion 61 in the up-down direction in Fig. 1. The second connection portion 64b, the third connection portion 64c, and the fourth connection portion 64d each connect the central portion in the longitudinal direction of the corresponding peripheral arrangement portion 62 to the exposed electrode portion 61. For example, the first peripheral portion 62a and the second peripheral portion 62b are arranged on an extension of each other. Similarly, for example, the third peripheral portion 62c and the fourth peripheral portion 62d are arranged on an extension of each other. The gap between the outer peripheral edge of the exposed electrode portion 61 and the inner peripheral edge of the peripheral arrangement portion 62 is divided into a plurality of gaps 90 by each of the connecting portions 64. In this embodiment, the planar shape of each gap 90 is L-shaped. In this embodiment, the first connection portion 64a is disposed on an extension of the wiring portion 50.

[0022] In the present embodiment, the planar shape of the conductor layer 20 is as described above. The insulating cover layer 30 covers the wiring portion 50 and the outer peripheral portion of the annular peripheral arrangement portion 62. The inner peripheral portion of the annular peripheral arrangement portion 62, the exposed electrode portion 61, and each connection portion 64 are exposed from the openings 33 of the insulating cover layer 30.

[0023] As described above, the thickness T1 (FIG. 2(a)) of the portion of the electrode portion 60 that overlaps with the inner peripheral edge 33a of the opening 33 in a plan view is greater than the thickness T2 (FIG. 2(a)) of the central portion 60a of the electrode portion 60. In addition, in the case of this embodiment, the central portion 60a of the electrode portion 60 is the central portion 61a of the exposed electrode portion 61, and therefore the thickness T2 of the central portion 60a of the electrode portion 60 is the thickness T2 of the central portion 61a of the exposed electrode portion 61. In this embodiment, the central portion 61a of the exposed electrode portion 61 is a circle centered on the center C of the exposed electrode portion 61, as shown in Figure 1, and is an area within the circle having a diameter that is half the minor axis (short side) D1 of the exposed electrode portion 61. The thickness T2 of the central portion 61a of the exposed electrode portion 61 can be set to the 10-point average of the thickness of the central portion 61a. As described above, the planar shape of the exposed electrode portion 61 is not limited to a rectangular shape, and may be a square shape, a circle, or the like. When the planar shape of the exposed electrode portion 61 is a square shape, the central portion 61a of the exposed electrode portion 61 is a region within a circle whose center is the center C of the exposed electrode portion 61 and whose diameter is half the dimension of one side of the exposed electrode portion 61. Similarly, when the planar shape of the exposed electrode portion 61 is a circle, the central portion 61a of the exposed electrode portion 61 is a region within a circle whose center is the center C of the exposed electrode portion 61 and whose diameter is half the dimension of the diameter of the exposed electrode portion 61.

[0024] The overall shape of the flexible printed circuit board 100 is not particularly limited, but as an example, it has a shape having a longitudinal direction and a lateral direction as shown in FIG. The flexible printed circuit board 100 has a plurality of electrode sections 60 and wiring sections 50 connected to each of the electrode sections 60 . The flexible printed circuit board 100 has external connection parts 80 for electrically connecting each wiring part 50 to an external device. The external terminal (not shown) of the external connection portion 80 may be arranged on the same surface on which the exposed electrode portion 61 is exposed, or on the surface opposite to the surface on which the exposed electrode portion 61 is exposed.

[0025] Here, according to the investigations of the present inventors, it is believed that defects such as cracks and breaks in the conductor layer 20 occur during the process of laminating the main cover layer 31 onto the substrate 10, heating and pressing the substrate 10 and the main cover layer 31 together. It has also been found that defects such as cracks and breaks in the conductor layer 20 often occur at positions overlapping the inner peripheral edge 33a of the insulating cover layer 30. This is thought to be due to the shear force acting on the conductor layer 20 at positions corresponding to the inner peripheral edge 33a of the insulating cover layer 30 due to the pressure applied during integration. Further investigation by the present inventors has revealed that the likelihood of defects such as cracks and breaks occurring may differ depending on the position relative to the center of the electrode portion 60. For example, in the case of a flexible printed circuit board 100 having a shape with a longitudinal direction and a lateral direction as shown in Figure 4, it has been found that defects may be more likely to occur in the areas aligned in the lateral direction with the center of the electrode portion 60 as the reference point. Therefore, as described above, by having one or more connection portions 64 (first connection portion 64a, second connection portion 64b described later) that connect the peripheral arrangement portion 62 and the exposed electrode portion 61 in a first direction (e.g., the left-right direction in Figure 1) and one or more connection portions 64 (third connection portion 64c, fourth connection portion 64d described later) that connect the peripheral arrangement portion 62 and the exposed electrode portion 61 in a second direction (e.g., the up-down direction in Figure 1), the reliability of the electrical connection between the peripheral arrangement portion 62 and the exposed electrode portion 61 can be improved even in areas aligned in the short direction with the center of the electrode portion 60 as the reference. The first direction here is, for example, the X direction shown in FIG. 4, and the second direction is, for example, the Y direction shown in FIG.

[0026] More specifically, in this embodiment, the electrode portion 60 includes, as the peripheral arrangement portion 62, a first direction extending portion (third peripheral arrangement portion 62c, fourth peripheral arrangement portion 62d) extending in a first direction, and a second direction extending portion (first peripheral arrangement portion 62a, second peripheral arrangement portion 62b) extending in a second direction intersecting the first direction, and, as the connection portion 64, a first connection portion (third connection portion 64c, fourth connection portion 64d) connecting the first direction extending portion and the exposed electrode portion 61, and a second connection portion (first connection portion 64a, second connection portion 64b) connecting the second direction extending portion and the exposed electrode portion 61. This improves the reliability of the electrical connection between the peripheral arrangement portion 62 and the exposed electrode portion 61. In this embodiment, the first direction (the left-right direction in FIG. 1) and the second direction (the up-down direction in FIG. 1) are perpendicular to each other, but the present invention is not limited to this example.

[0027] In this embodiment, the flexible printed circuit board 100 is a stretchable flexible printed circuit board (stretchable wiring board), and the base material 10, the conductor layer 20, and the main cover layer 31 are each stretchable. In this case, the flexible printed circuit board 100 is attached to the target surface of the target object (for example, the skin of a living body) when in use. An attachment (not shown) may be attached to the surface of the flexible printed circuit board 100 opposite to the target object side.

[0028] When the substrate 10 is stretchable, the substrate 10 is a thin film sheet material that can stretch in at least one in-plane direction. The term "stretchable" as used here refers to the property of the substrate 10 to stretch when tension is applied to the substrate 10 and to contract in response to compression, and the change in the dimensional shape of the substrate 10 due to stretching is greater than the change in dimensional shape due to contraction.

[0029] The material constituting the substrate 10 is not particularly limited, but may be, for example, an elastomer material such as nitrile rubber, latex rubber, or urethane-based elastomer. In particular, by using a urethane-based elastomer sheet used for medical purposes, high safety can be achieved even when attached to human skin.

[0030] The thickness of the substrate 10 is not particularly limited, but from the viewpoint of not inhibiting the expansion and contraction movement of the skin, it is preferably, for example, 50 μm or less, and more preferably 5 μm or less.

[0031] The maximum elongation of the substrate 10 is preferably 10% or more, more preferably 50% or more, even more preferably 100% or more, and particularly preferably 200% or more. The maximum elongation of the substrate 10 refers to the maximum value of the elongation at which the substrate can be elastically deformed in one in-plane direction. Elongation refers to the percentage of elongation in one in-plane direction due to the application of force, compared to the dimensions when no external force is applied (0% elongation dimensions). For example, an elongation of 50% is 1.5 times the 0% elongation dimension, and an elongation of 100% is twice the 0% elongation dimension.

[0032] The main cover layer 31 is laminated on one surface of the substrate 10 and covers the conductor layer 20 . The material constituting the main cover layer 31 is not particularly limited, but may be, for example, an elastomer material similar to that of the substrate 10 . However, the main cover layer 31 may be made of a material different from that of the substrate 10 as long as it is made of a material that is at least insulating and stretchable. The thickness of the main cover layer 31 is not particularly limited, but from the viewpoint of not inhibiting the expansion and contraction movement of the skin, it is preferably, for example, 50 μm or less, and more preferably 5 μm or less.

[0033] The conductor layer 20 is, for example, a coating film containing a conductive filler and a binder containing a thermoplastic resin. The conductor layer 20 contains a binder containing a thermoplastic resin, and thus can follow the expansion and contraction of the substrate 10 well. The conductive filler is made of, for example, silver, gold, platinum, carbon, copper, aluminum, cobalt, nickel, or an alloy thereof, etc. As an example, the conductive filler contained in the conductor layer 20 is silver. Examples of the thermoplastic resin include thermoplastic elastomer materials such as urethane resin, acrylic resin, and silicone rubber. It is desirable to select a thermoplastic resin with a low Young's modulus so that the modulus of elasticity of the conductor layer 20 in a coated state is equal to or smaller than the modulus of elasticity of the substrate 10. One type of elastomer material may be used, or multiple types of elastomer materials may be mixed and used. The conductor layer 20 is formed by a printing method, which is not particularly limited, but may be, for example, a screen printing method, an inkjet printing method, a gravure printing method, or an offset printing method. The conductor layer 20 is capable of transmitting electrical signals and currents. More specifically, in this embodiment, the exposed electrode portion 61 is a bioelectrode that comes into contact with the skin of a living body. Biosignals such as electroencephalograms, myoelectric potentials, and electrocardiograms can be acquired from the living body and transmitted to an external attachment via the electrode portion 60 and the wiring portion 50.

[0034] When joining the substrate 10 and the main cover layer 31, after printing the conductor layer 20 on the substrate 10, the main cover layer 31 is aligned and superimposed on the substrate 10, and then heat and pressure are applied. This allows the substrate 10 and the main cover layer to be fused together. As a heating means, a lamination method using a heated roll or a hot press means can be used.

[0035] It is also preferable that the external connection portion 80 is provided with a reinforcing sheet that is more rigid and inelastic than the substrate 10 and the main cover layer 31 .

[0036] In the present invention, the flexible printed circuit board 100 is not limited to a stretchable flexible printed circuit board (stretchable wiring board). In the flexible printed circuit board 100, the base material 10 and the main cover layer 31 are each made of a PI (polyimide film) or a PET (polyethylene terephthalate) film, and the conductor layer 20 may also be non-stretchable.

[0037] As shown in FIG. 3, in addition to the above-described configuration, the flexible printed circuit board 100 preferably has release films 32 and 40 on the front and back sides, respectively, to ensure ease of handling during manufacturing, distribution, storage, etc. of the flexible printed circuit board 100. The material of the release film 32 and the release film 40 is not particularly limited, but may be PET (polyethylene terephthalate), paper, or the like. Of these, the release film 32 on the front side is laminated on the main cover layer 31 to cover the main cover layer 31 . When the release film 32 is laminated on the main cover layer 31 , the insulating cover layer 30 is composed of the main cover layer 31 and the release film 32 . An opening is formed in the release film 32, and the opening in the release film 32 has the same position and dimensions as the opening in the main cover layer 31. When the release film 32 is laminated on the main cover layer 31, the opening 33 in the insulating cover layer 30 is formed by the opening in the main cover layer 31 and the opening in the release film 32. The back surface release film 40 is laminated on the back surface side of the substrate 10 and covers the back surface of the substrate 10 . When the flexible printed circuit board 100 is to be used, the release film 32 and the release film 40 are peeled off and removed to leave the state shown in FIGS. 2(a) and 2(b).

[0038] Here, the width dimension W1 (FIG. 1) of each part of the peripheral arrangement portion 62 is not particularly limited, but is preferably 0.5 mm or more and 1.5 mm or less, and is also preferably 0.5 mm or more and 1.3 mm or less, or 0.5 mm or more and 1.0 mm or less. The positional accuracy of the bonding of the main cover layer 31 to the substrate 10 is, for example, approximately ±0.5 mm, and by making the width dimension W1 of the peripheral arrangement portion 62 1.0 mm or more, the main cover layer 31 can be bonded to the substrate 10 so that the inner peripheral edge 33a overlaps the peripheral arrangement portion 62 more reliably. The width dimension W2 (FIG. 1) of the connecting portion 64 is equal to the width dimension W1 of the peripherally disposed portion 62. The width W3 (FIG. 1) of the wiring portion 50 is equal to the width W1 of the peripheral arrangement portion 62.

[0039] The film thickness of each portion of the conductor layer 20 varies depending on the physical properties of the conductive paste that constitutes the conductor layer 20, the mesh and emulsion of the printing plate, etc., but can be, for example, 5 μm or more and 50 μm or less. The film thickness of the peripheral arrangement portion 62, the connection portion 64, and the wiring portion 50 can be, for example, 10 μm or more and 50 μm or less, and preferably 15 μm or more and 30 μm or less. The thickness of the exposed electrode portion 61 can be set to, for example, 5 μm or more and 20 μm or less, and the thickness of the central portion 61a can be set to, for example, about 5 μm. The manufacturing conditions for the conductor layer 20 are set so that the film thickness of the peripheral arrangement portion 62, the connection portion 64, and the wiring portion 50 is greater than the film thickness of the central portion 61a.

[0040] The cross-sectional shape of each part of the conductor layer 20 is not particularly limited, but as an example, each of the cross-sectional shapes can be as follows. The cross-sectional shape of the peripheral arrangement portion 62 (the cross-sectional shape perpendicular to the extension direction of the linearly extending peripheral arrangement portion 62) can be an upwardly convex semicircular, semi-elliptical or trapezoidal shape, as shown in Figure 2(a). That is, the portion of the electrode section 60 that overlaps with the inner peripheral edge 33a of the opening 33 in a plan view is raised upward. The cross-sectional shapes of the connecting portion 64 and the wiring portion 50 are similar to that of the peripheral arrangement portion 62 . The cross-sectional shape of the exposed electrode portion 61 may be such that the peripheral edge is raised compared to the other portions, as shown in FIG. 2(a).

[0041] <Variation 1> Next, a flexible printed circuit board according to Modification 1 will be described with reference to FIG. The flexible printed circuit board of this modified example differs from the flexible printed circuit board 100 of the above embodiment in the points described below, but is otherwise configured in the same way as the flexible printed circuit board 100 of the above embodiment.

[0042] As shown in FIG. 5, in this modification, a plurality of wiring portions (for example, a plurality of branch wiring portions 52a, 52b, 52c) are connected to one electrode portion 60. This makes it possible to suitably prevent defects such as cracks and disconnections from occurring at the connection points 70 between the wiring portion 50 and the electrode portion 60.

[0043] More specifically, in this modification, the main portion 51 of one wiring portion 50 branches into multiple (e.g., three) branch wiring portions 52a, 52b, and 52c, and each of the multiple branch wiring portions 52a, 52b, and 52c is connected to a peripheral arrangement portion 62 (e.g., a first peripheral arrangement portion 62a) of one electrode portion 60. The film thickness of the wiring portion 50 is greater than the film thickness T2 of the central portion 60a of the electrode portion 60 (the central portion 61a of the exposed electrode portion 61). The width of each of the branch wiring portions 52a, 52b, and 52c can be set to be equal to the width of the main portion 51, for example. The width of each of the branch wiring portions 52a, 52b, and 52c and the width of the main portion 51 can be set to be equal to the width of the wiring portion 50 described in the above embodiment.

[0044] <Variation 2> Next, a flexible printed circuit board according to Modification 2 will be described with reference to FIG. The flexible printed circuit board of this modified example differs from the flexible printed circuit board 100 of the above embodiment in the points described below, but is otherwise configured in the same way as the flexible printed circuit board 100 of the above embodiment. In the above embodiment, an example has been described in which the peripheral arrangement portion 62 surrounds the periphery of the exposed electrode portion 61 in an annular shape, but the present invention is not limited to this example. For example, as shown in Figure 6, this modified example may have only a cross-direction extending portion (first peripheral portion 62a) that extends across the connection point 70 between the wiring portion 50 and the electrode portion 60 and in a direction that intersects with the wiring portion 50, as the peripheral portion 62. In this modification, the insulating cover layer 30 covers the wiring portion 50 and a portion (the left half in FIG. 6) of the linear peripheral arrangement portion 62 (first peripheral arrangement portion 62a). The other portion (the right half in FIG. 6) of the linear peripheral arrangement portion 62 (first peripheral arrangement portion 62a), the exposed electrode portion 61, and the connection portion 64 (first connection portion 64a) are exposed from the opening 33 of the insulating cover layer 30.

[0045] <Variation 3> Next, a flexible printed circuit board according to Modification 3 will be described with reference to FIG. The flexible printed circuit board of this modified example differs from the flexible printed circuit board 100 of the above embodiment in the points described below, but is otherwise configured in the same way as the flexible printed circuit board 100 of the above embodiment. In the above embodiment, an example has been described in which the peripheral arrangement portion 62 is formed as a continuous line as a whole, but the present invention is not limited to this example. For example, as shown in Fig. 7 as a modified example, the peripheral arrangement portion 62 (first peripheral arrangement portion 62a) may be formed of dot-shaped portions 65, which are multiple dot-shaped portions arranged in a row along the inner peripheral edge 33a of the opening 33. Each dot-shaped portion 65 is arranged in an island shape separated from the exposed electrode portion 61 and the wiring portion 50 . In other words, in the present invention, a portion of the electrode portion 60 (in this modified example, the peripheral portion 62 constituted by the dot-shaped portion 65) does not have to be connected (electrically and mechanically) to the wiring portion 50.

[0046] <Variation 4> Next, a flexible printed circuit board according to Modification 4 will be described with reference to FIGS. 8(a) and 8(b). The flexible printed circuit board of this modified example differs from the flexible printed circuit board 100 of the above embodiment in the points described below, but is otherwise configured in the same way as the flexible printed circuit board 100 of the above embodiment. In the above embodiment, an example has been described in which the inner peripheral edge 33a of the opening 33 overlaps with the peripheral edge arrangement portion 62 arranged around the exposed electrode portion 61 in a plan view. In contrast to this, in this modified example, the inner peripheral edge 33a of the opening 33 overlaps the peripheral edge 67 of the electrode portion 60, which has a solid pattern as a whole, in a plan view. In this modified example, the thickness T1 of the peripheral portion 67 of the electrode portion 60 (FIG. 8(a)) is greater than the thickness T2 of the central portion 60a of the electrode portion 60 (FIG. 8(a)). That is, the manufacturing conditions for the conductor layer 20 including the electrode portion 60 are set so that the thickness T1 of the peripheral portion 67 is greater than the thickness T2 of the central portion 60a. The planar shape of the electrode section 60 is not particularly limited, but as an example, it may be a rectangular shape (for example, a rectangular shape with rounded corners) as shown in FIG. 8(a). The peripheral edge portion 67 is an annular portion that follows the outer periphery of the electrode portion 60 . In plan view, the inner peripheral edge 33a of the opening 33 is disposed between the outer peripheral edge and the inner peripheral edge of the peripheral edge portion 67. In other words, the peripheral edge portion 67 exists in a range spanning the inner peripheral edge 33a of the opening 33 from the inside to the outside. In this modified example, the insulating cover layer 30 covers the wiring portion 50 and the outer peripheral portion of the peripheral edge portion 67 of the electrode portion 60. The other portion of the electrode portion 60 is exposed from the opening 33 of the insulating cover layer 30.

[0047] In this modified example, the central portion 60a of the electrode portion 60 is a circle centered on the center C of the electrode portion 60, as shown in Figure 8(a), and is an area within the circle having a diameter half the minor axis (short side) D1 of the electrode portion 60. The thickness T2 of the central portion 60a of the electrode portion 60 can be set to the 10-point average of the thickness of the central portion 60a. The planar shape of the electrode section 60 is not limited to a rectangular shape, and may be a square shape, a circle, or the like. When the planar shape of the electrode section 60 is a square shape, the central section 60a of the electrode section 60 is a region within a circle whose center is the center C of the electrode section 60 and whose diameter is half the dimension of one side of the electrode section 60. Similarly, when the planar shape of the electrode section 60 is a circle, the central section 60a of the electrode section 60 is a region within a circle whose center is the center C of the electrode section 60 and whose diameter is half the dimension of the diameter of the electrode section 60.

[0048] Although the embodiments and modifications have been described above with reference to the drawings, these are merely examples of the present invention, and various configurations other than those described above can also be adopted.

[0049] The present embodiment encompasses the following technical ideas. (1) a substrate; a conductor layer formed by printing on the substrate; an insulating cover layer formed on the substrate and covering a portion of the conductor layer; Equipped with the conductor layer has a wiring portion and an electrode portion connected to the wiring portion, the insulating cover layer has an opening that exposes a portion of the electrode portion; A flexible printed circuit board in which the thickness of a portion of the electrode portion that overlaps with the inner periphery of the opening in a plan view is greater than the thickness of a central portion of the electrode portion. (2) The electrode portion has an exposed electrode portion disposed inside the opening and a peripheral portion extending along the inner peripheral edge of the opening, a portion of the electrode portion that overlaps with the inner peripheral edge of the opening in a plan view is a portion of the peripheral edge arrangement portion that overlaps with the inner peripheral edge of the opening in a plan view, The flexible printed circuit board according to (1), wherein the central portion of the electrode portion is the central portion of the exposed electrode portion. (3) The flexible printed circuit board according to (2), wherein the peripheral arrangement portion includes a cross-direction extending portion that extends across the connection point between the wiring portion and the electrode portion in a direction that intersects with the wiring. (4) The flexible printed circuit board according to (2) or (3), wherein the electrode portion has a connection portion that connects the peripheral arrangement portion and the exposed electrode portion. (5) The flexible printed circuit board according to (4), wherein the electrode portion has a plurality of the connection portions. (6) The peripheral arrangement portion includes a first direction extending portion extending in a first direction and a second direction extending portion extending in a second direction intersecting the first direction, The flexible printed circuit board according to (5) includes, as the connection portion, a first connection portion connecting the first direction extending portion and the exposed electrode portion, and a second connection portion connecting the second direction extending portion and the exposed electrode portion. (7) The flexible printed circuit board according to any one of (2) to (6), wherein the width of the peripheral arrangement portion is 0.5 mm or more and 1.5 mm or less. (8) The flexible printed circuit board according to any one of (1) to (7), wherein a plurality of the wiring portions are connected to one of the electrode portions. (9) The flexible printed circuit board according to any one of (1) to (8), wherein the electrode portion has a portion that overlaps with the inner periphery of the opening in a plan view and that protrudes upward. (10) The flexible printed circuit board according to any one of (1) to (3), wherein the conductor layer is stretchable. [Explanation of symbols]

[0050] 10 Base material 20 Conductor layer 30 insulating cover layer 31 Main Cover Layer 32 Release film 33 Aperture 33a inner edge 40 Release film 50 Wiring section 51 Main Section 52a, 52b, 52c branch wiring section 60 Electrode section 60a central section 61 Exposed electrode part 61a central part 62 Peripheral placement section 62a First peripheral arrangement portion 62b Second peripheral arrangement portion 62c Third peripheral arrangement part 62d Fourth peripheral arrangement part 64 Connection 64a First connection part 64b Second connection part 64c Third connection part 64d 4th connection part 65 Dotted part 67 Periphery 70 connection points 80 External connection part 90 Blank section 100 Flexible Printed Circuit Board

Claims

1. A substrate; a conductor layer formed by printing on the substrate; an insulating cover layer formed on the substrate and covering a portion of the conductor layer; Equipped with the conductor layer has a wiring portion and an electrode portion connected to the wiring portion, the insulating cover layer has an opening that exposes a portion of the electrode portion; A flexible printed circuit board in which the thickness of a portion of the electrode portion that overlaps with the inner periphery of the opening in a plan view is greater than the thickness of a central portion of the electrode portion.

2. the electrode portion has an exposed electrode portion disposed inside the opening and a peripheral portion extending along an inner peripheral edge of the opening, a portion of the electrode portion that overlaps with the inner peripheral edge of the opening in a plan view is a portion of the peripheral edge arrangement portion that overlaps with the inner peripheral edge of the opening in a plan view, The flexible printed circuit board according to claim 1 , wherein the central portion of the electrode portion is the central portion of the exposed electrode portion.

3. The flexible printed circuit board according to claim 2 , wherein the peripheral portion includes a cross-direction extending portion that extends across a connection point between the wiring portion and the electrode portion in a direction that crosses the wiring portion.

4. The flexible printed circuit board according to claim 2 or 3, wherein the electrode portion has a connection portion that connects the peripheral arrangement portion and the exposed electrode portion.

5. The flexible printed circuit board according to claim 4 , wherein the electrode portion has a plurality of the connection portions.

6. the peripheral arrangement portion includes a first direction extending portion extending in a first direction and a second direction extending portion extending in a second direction intersecting the first direction, 6. The flexible printed circuit board according to claim 5, wherein the connection portion includes a first connection portion connecting the first direction extending portion and the exposed electrode portion, and a second connection portion connecting the second direction extending portion and the exposed electrode portion.

7. 4. The flexible printed circuit board according to claim 2, wherein the width of the peripheral arrangement portion is 0.5 mm or more and 1.5 mm or less.

8. The flexible printed circuit board according to claim 1 , wherein a plurality of the wiring portions are connected to one of the electrode portions.

9. The flexible printed circuit board according to claim 1 , wherein a portion of the electrode portion that overlaps with an inner periphery of the opening in a plan view is protruded upward.

10. The flexible printed circuit board according to claim 1 , wherein the conductor layer is stretchable.

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