WO2022176599A1

WO2022176599A1 - Method for manufacturing wiring board, and flexible printed wiring board

Info

Publication number: WO2022176599A1
Application number: PCT/JP2022/003790
Authority: WO
Inventors: 大輔荒井; 有希成田
Original assignee: 株式会社フジクラ
Priority date: 2021-02-16
Filing date: 2022-02-01
Publication date: 2022-08-25

Abstract

A method for manufacturing a flexible printed wiring board 1 comprises: a first step for preparing a metal foil 200 having a first main surface 201 and a second main surface 202; a second step for performing half etching on a first portion 203 of the metal foil 200 from the first and second main surface 201, 202 sides simultaneously, to thin the first portion 203; a third step for affixing a base film 10 to the metal foil 200 from the first main surface 201 side; a fourth step for performing etching on the first portion 203 from the second main surface 202 side to remove the first portion 203, thereby forming wiring 20; and a fifth step for affixing a coverlay 30 to the base film 10 from the second main surface 202 side so as to cover the wiring 20.

Description

Wiring board manufacturing method and flexible printed wiring board

The present invention relates to a wiring board manufacturing method and a flexible printed wiring board.
For designated countries where incorporation by reference of literature is permitted, the content described in Japanese Patent Application No. 2021-022650 filed in Japan on February 16, 2021 is incorporated herein by reference, and the description of this specification be part of

a step of etching to form a circuit pattern on one surface of the copper plate; after the etching step, forming a substrate on the side of the circuit pattern forming surface of the copper plate, fixing and integrating the copper plate to the substrate; A method for manufacturing a circuit board is known, which includes a step of etching the side of a copper plate on which a circuit pattern is not formed, separating circuit conductors constituting the circuit pattern, and forming a predetermined circuit pattern (for example, Patent Document 1).

JP-A-2002-76571

A thick copper plate is used as a material for forming circuit patterns in wiring boards used in applications where large currents are supplied, such as coils for in-vehicle motors. The thicker the copper plate, the longer the processing time required for etching. In the method of performing etching from one side of the copper plate twice, as in the above-described prior art, there is a problem that the thicker the copper plate, the longer the processing time required for etching, which may reduce productivity.

The problem to be solved by the present invention is to provide a wiring board manufacturing method capable of improving productivity.

[1] A wiring board manufacturing method according to the present invention is a wiring board comprising a base material, wiring arranged on the base material, and a coverlay laminated on the base material so as to cover the wiring. , wherein a first step of preparing a metal foil having a first main surface and a second main surface; and a first portion of the metal foil having the first and second main surfaces a second step of thinning the first portion by simultaneously performing half-etching from the side; a third step of attaching the base material to the metal foil from the first main surface side; a fourth step of forming the wiring by removing the first portion by etching the first portion from the main surface side of 2; and covering the wiring from the second main surface side. and a fifth step of attaching the coverlay to the base material.

[2] In the above invention, the second step includes performing the half-etching on the entire surface of the first portion so that the first portion remains along the thickness direction of the wiring board. may contain.

[3] In the above invention, the second step may be performed by adjusting the thickness of the half so that the thickness of the first portion is 5% to 15% of the thickness of the second portion other than the first portion. Etching may be included.

[4] A flexible printed wiring board according to the present invention is a flexible printed wiring comprising a base material, wiring arranged on the base material, and a coverlay laminated on the base material so as to cover the wiring. A plate, wherein the wiring has, in a cross section along the width direction of the wiring, a first surface and a second surface facing each other along the width direction of the wiring, and the first and second surfaces. a third surface and a fourth surface connecting the surfaces and facing each other along the thickness direction of the wiring board, the first surface being curved so as to be recessed inside the wiring; , a first curved surface having a first end connected to the third surface, a second end curved to be recessed inside the wiring and connected to the first curved surface, and the fourth surface a second curved surface having a third end connected to the second surface, the second surface curved to be recessed inside the wiring, and having a fourth end connected to the third surface a third curved surface, a fourth curved surface curved to be recessed inside the wiring, and having a fifth end connected to the third curve and a sixth end connected to the fourth surface; A flexible printed wiring board that includes and satisfies the following formula (1).
W ₂ <W ₁ <W ₃ (1)
However, in the above formula ( ₁ ), W1 is the width between the first end and the fourth end, and W2 is the width between the _second end and the fifth end. and W3 is the width between the _third end and the sixth end.

[5] In the above invention, it is preferable that the following formula (2) is satisfied.
H ₁ <H ₂ (2)
However, H1 is the height from the third plane to the _first virtual plane, H2 is the height from the _first virtual plane to the fourth plane, and the first virtual plane is a virtual plane passing through the second end and the fifth end.

In the present invention, wiring is formed by half-etching from both sides of the metal foil and then etching from one side of the metal foil. Therefore, in the present invention, the processing time required for etching can be reduced, and productivity can be improved.

FIG. 1 is a plan view showing a flexible printed wiring board according to an embodiment of the invention. FIG. 2 is a cross-sectional view showing a flexible printed wiring board according to an embodiment of the present invention, taken along line II-II in FIG. FIG. 3 is an enlarged cross-sectional view showing part III of FIG. FIG. 4(a) is a sectional view showing a bent state of a flexible printed wiring board in a comparative example, and FIG. 4(b) is a sectional view showing a bent state of a flexible printed wiring board in an embodiment of the present invention. is. 5(a) to 5(h) are cross-sectional views showing a method for manufacturing a flexible printed wiring board according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a plan view showing a flexible printed wiring board according to this embodiment. FIG. 2 is a cross-sectional view showing the flexible printed wiring board in this embodiment, taken along line II-II in FIG.

As shown in FIGS. 1 and 2, a flexible printed wiring board (FPC) 1 includes a base film (first coverlay) 10, a plurality of (four in this example) wirings 20, and a coverlay (second of the coverlay) 30 and. The base film 10 in this embodiment corresponds to an example of the "base material" in this invention.

The base film 10 is a flexible and elongated strip-shaped film, and is made of an electrically insulating material such as a resin material. This base film 10 has a first resin layer 11 and a first adhesive layer 12 .

The first resin layer 11 is a film made of a flexible resin material. As shown in FIG. 2, the first resin layer 11 faces a first curved surface 211 (described later) and a third curved surface 221 (described later) of the wiring 20, and is recessed toward the wiring 20. It has a recess 11a. Although the material constituting the first resin layer 11 is not particularly limited, for example, polyimide (PI), liquid crystal polymer (LCP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyetherimide (PEI), ), polyetheretherketone (PEEK), and aramid.

The first adhesive layer 12 bonds the first resin layer 11 and the wiring 20 together. The first adhesive layer 12 is interposed between the first resin layer 11 and the wiring 20 and is also interposed between the wirings 20 . Adhesives can be used as the material constituting the first adhesive layer 12, and are not particularly limited, but are polyamide-based hot-melt adhesives, polyurethane-based hot-melt adhesives, and polyester-based hot-melt adhesives. , an olefin-based hot-melt adhesive can be used.

The material constituting the first resin layer 11 and the first adhesive layer 12 of the base film 10 is not particularly limited to the above. For example, a prepreg may be used instead of the resin film described above for the first resin layer 11 . Alternatively, it may be formed using a dry film made of a photosensitive coverlay material, or by applying a liquid photosensitive coverlay material on the first adhesive layer 12 and then exposing and developing the first adhesive layer 12 . One resin layer 11 may be formed. Alternatively, the first resin layer 11 may be formed by printing liquid cover lay ink on the first adhesive layer.

Alternatively, the first resin layer 11 may be composed of a so-called solder resist. Specifically, the first resin layer 11 may be formed using a dry film made of a photosensitive resist material. Alternatively, the first resin layer 11 may be formed by applying a liquid photosensitive resist material on the first adhesive layer 12, followed by exposure and development. Alternatively, the first resin layer 11 may be formed by printing liquid solder resist ink on the first adhesive layer 12 .

The first adhesive layer 12 may also be formed by exposing and developing a liquid photosensitive coverlay material instead of the above adhesive. Alternatively, the first adhesive layer 12 may be formed by printing liquid coverlay ink.

Specific examples of the above photosensitive coverlay materials and photosensitive resist materials include those using polyester, epoxy, acrylic, polyimide, polyurethane, and the like. Further, specific examples of the above cover lay ink and solder resist ink include those based on polyimide and epoxy.

A plurality of wirings 20 are formed on the base film 10 . The wiring 20 is made of a conductive material such as metal. Examples of the metal forming the wiring 20 include copper, silver, and gold. In this embodiment, thick copper is used as the material forming the wiring 20 . Although not particularly limited, the thickness T ₁ of the wiring 20 is 35 μm to 2 mm (35 μm≦T ₁ ≦2 mm) in this embodiment. Also, the thickness T ₁ of the wiring 20 may be 70 μm to 2 mm (70 μm≦T ₁ ≦2 mm). Since the thickness T1 of the wiring is large in this way, the flexible printed wiring board ₁ of the present embodiment can be suitably used for applications in which a large current is supplied.

In this embodiment, a plurality of wirings 20 extend linearly along the X direction in the figure. The plurality of wirings 20 are arranged parallel to each other at regular intervals. The number, shape, arrangement, etc. of the wirings 20 are not particularly limited to this, and can be set arbitrarily. Also, the number of wirings 20 is not limited to plural, and may be one.

FIG. 3 is an enlarged cross-sectional view showing part III of FIG. As shown in FIG. 3, the wiring 20 includes a first surface 21, a second surface 22, a third surface 23, and a fourth surface 24. As shown in FIG. In this embodiment, the first surface 21 and the second surface 22 are both side surfaces of the wiring 20 and face each other. On the other hand, in this embodiment, the third surface 23 is the bottom surface of the wiring 20 and the fourth surface 24 is the top surface of the wiring 20 . The third and

fourth surfaces

23, 24 face each other and are interposed between the first surface 21 and the second surface 22 to connect the first and

second surfaces

21, 22. ing.

The first surface 21 is composed of a first curved surface 211 and a second curved surface 212. The first curved surface 211 is a curved surface that is recessed toward the inside of the wiring 20 (+Y direction in the drawing). In this embodiment, the first curved surface 211 is located on the base film 10 side with respect to the second curved surface 212 and is interposed between the third surface 23 and the second curved surface 212. . Also, the first curved surface 211 is connected to the third surface 23 at the first end 213 and is connected to the second curved surface 212 at the second end 214 .

The second end 214 is located on the outermost side (−Y direction in the drawing) of the wiring 20 in the width direction (Y direction in the drawing) of the wiring 20 . Therefore, the first curved surface 211 as a whole inclines toward the outside of the wiring 20 (-Y direction in the figure) as the distance from the base film 10 increases.

The second curved surface 212, like the first curved surface 211, is a curved surface that is concave toward the inside of the wiring 20 (+Y direction in the drawing). In this embodiment, the second curved surface 212 is located on the coverlay 30 side with respect to the first curved surface 211 and is interposed between the first curved surface 211 and the fourth surface 24. . Also, the second curved surface 212 is connected to the fourth surface 24 at the third end 215 .

Also, the height H2 of the _second curved surface 212 is larger _than the height H1 of the _first curved surface ₂₁₁ (H1<H2). The height H1 of the _first curved surface 211 is the distance from the third surface 23 to the _first virtual plane VP1, and the height H2 of the _second curved surface 212 is the distance from the virtual plane VP1. It is the distance from ₁ to the fourth surface 24 . A _first virtual plane VP1 is a virtual plane that passes through the second end 214 and the fifth end 224 (described below) and is substantially parallel to the third and fourth faces 23,24. be.

The third end 215 is positioned inside the wiring 20 (in the +Y direction in the figure) from the second end 214 described above. Therefore, the second curved surface 212 as a whole inclines toward the inner side of the wiring (+Y direction in the figure) as the distance from the base film 10 increases.

The second surface 22 is substantially plane-symmetrical with the first surface 21 with respect to the _second virtual plane VP2. The _second virtual plane VP2 extends in the thickness direction (the Z direction in the drawing) of the flexible printed wiring board 1 in a cross section along the width direction of the wiring 20, and substantially extends the wiring 20 in the width direction. is the plane that bisects . This second surface 22 is composed of a third curved surface 221 and a fourth curved surface 222 .

The third curved surface 221 is substantially plane-symmetrical with the first curved surface 211 with respect to the _second virtual plane VP2, and is recessed toward the inner side of the wiring 20 (-Y direction in the drawing). It is a curved surface. In this embodiment, the third curved surface 221 is located on the base film 10 side with respect to the fourth curved surface 222 and is interposed between the third surface 23 and the fourth curved surface 222. . The third curved surface 221 is connected to the third surface 23 at the fourth end 223 and connected to the fourth curved surface 222 at the fifth end 224 . Also, the third curved surface 221 has the same height as the height H1 of the _first curved surface.

The fifth end 224 is formed at a position substantially symmetrical to the second end 214 with respect to the _second virtual plane VP2, and is arranged in the width direction of the wiring 20 (the Y direction in the drawing). , is positioned on the outermost side of the wiring 20 (+Y direction in the drawing). Therefore, the third curved surface 221 as a whole inclines toward the outside of the wiring 20 (+Y direction in the drawing) as the distance from the base film 10 increases.

The fourth curved surface 222 is substantially plane-symmetrical with the second curved surface 212 with respect to the _second virtual plane VP2, and is recessed toward the inner side of the wiring 20 (-Y direction in the drawing). It is a curved surface. In this embodiment, the fourth curved surface 222 is located on the coverlay 30 side with respect to the third curved surface 221 and is interposed between the third curved surface 221 and the fourth surface 24. . Also, the fourth curved surface 222 is connected to the fourth surface 24 at the sixth end 225 . Also, the fourth curved surface 222 has the same height as the height H2 of the _second curved surface 212 .

The sixth end 225 is positioned inside the wiring 20 (in the -Y direction in the figure) relative to the fifth end 224 . Therefore, the fourth curved surface 222 as a whole inclines toward the inner side of the wiring (-Y direction in the drawing) as the distance from the base film 10 increases.

The third and

fourth surfaces

23 and 24 are planes substantially parallel to the horizontal direction (the XY plane direction in the drawing) in this embodiment. As described above, since the first and fourth ends 213 and 223 are positioned outside the wiring 20 relative to the third and sixth ends 215 and 225, the line width W of the wiring 20 on the third plane is ₁ (the width between the first end 213 and the fourth end 223) is the line width W ₂ (the width between the third end 215 and the sixth end 225) of the wiring 20 on the fourth surface ) (W ₂ <W ₁ ). On the other hand, since the second and fifth ends 214, 224 are located further outside the wiring 20 than the first and fourth ends 213, 223, the line width W of the wiring 20 on the third surface is ₁ is smaller than the line width W3 of the wiring 20 between the _second and _fifth ends 214, 224 ₍ W1<W3).

As shown in FIG. 2 , the coverlay 30 is arranged on the base film 10 so as to cover the wiring 20 . In addition, although not shown, the terminal portion of the wiring 20 and the like may be exposed from the coverlay 30 . The coverlay 30 has a second resin layer 31 for protecting the wiring 20 and a second adhesive layer 32 for bonding the second resin layer 31 to the base film 10 and the wiring 20. there is

The second resin layer 31, like the first resin layer 11, is made of a flexible resin material. The second resin layer 31 also has a second concave portion 31 a that faces the second curved surface 212 and the fourth curved surface 222 of the wiring 20 and is recessed toward the wiring 20 .

In this embodiment, since the width W1 of the third surface 23 of the wiring ₂₀ is larger than the width W2 of the _fourth surface 24, the distance from the third end 215 to the sixth end 225 between the wirings 20 is is greater than the distance d ₁ between the _first end 213 and the fourth end 223 between the wirings 20 (d ₁ <d ₂ ). Therefore, the second recess 31a is recessed more than the first recess 11a of the base film 10, and the depth D2 of the _second recess 31a is larger than the depth of the first recess 11a. (D ₁ <D ₂ ). As the material forming the second resin layer 31, the same material as the material forming the first resin layer 11 of the base film 10 can be used. In addition, the material which comprises the 1st resin layer 11 and the 2nd resin layer 31 may differ.

On the other hand, as the material forming the second adhesive layer 32, the same material as the material forming the first adhesive layer 12 of the base film 10 can be used. Although not particularly limited, in the present embodiment, the second adhesive layer 32 and the first adhesive layer 12 are integrated. The materials forming the first adhesive layer 12 and the second adhesive layer 32 may be the same or different.

Further, the second resin layer 31 may be formed using a dry film made of a photosensitive coverlay material instead of the resin film described above, or a liquid photosensitive coverlay material may be used as the second resin film. The second resin layer 31 may be formed by coating the adhesive layer 32 and then exposing and developing. Alternatively, the second resin layer 31 may be formed by printing liquid cover lay ink on the second adhesive layer 32 . Alternatively, the second resin layer 31 may be composed of a so-called solder resist.

The second adhesive layer 32 may also be formed by exposing and developing a liquid photosensitive coverlay material instead of the above adhesive. Alternatively, the second adhesive layer 32 may be formed by printing liquid coverlay ink.

FIG. 4(a) is a sectional view showing a bent state of the flexible printed wiring board 1B in the comparative example, and FIG. 4(b) is a sectional view showing a bent state of the flexible printed wiring board 1 in the present embodiment. is.

As shown in FIG. 4A, in the wiring 20B of the flexible printed wiring board 1B in the comparative example, the width W1 between the _first and fourth ends 213B, 223B and the width W1 between the second and fifth ends 214B, 224B The width W ₂ between the ends and the width W ₃ between the third and sixth ends 215B and 225B are all equal (W ₁ =W ₂ =W ₃ ). Therefore, in the flexible printed wiring board 1B, the distance between the wirings 20B is small, and the range of motion at the time of bending becomes narrow, making it difficult to bend the flexible printed wiring board 1B. Moreover, when the flexible printed wiring board _1B is bent, the distance d2 between the sixth end 225B and the third end 215B between the wirings 20B becomes small. As described above, the wirings 20B are partially too close to each other, so that the insulation reliability between the wirings 20B is lowered.

In contrast, in the flexible printed wiring board 1 of this embodiment, the width W1 between the _first and

fourth ends

213 and 223 is greater than the width W2 between the _second and fifth ends 214 and 224. Largely, the width W3 between the _third and _sixth ends 215, ₂₂₅ is greater _than the width W1 ₍ W2<W1<W3). Therefore, compared to the comparative example, the distance between the wirings 20 is large, and the flexible printed wiring board 1 is easy to bend because the range of motion during bending is large. Moreover, when the flexible printed wiring board 1 is bent, the distance d2 between the sixth end 225 and the third end 215 between the wirings ₂₀ is larger than in the comparative example. Therefore, deterioration in insulation reliability between the wirings 20 can be suppressed.

Next, a method for manufacturing the flexible printed wiring board 1 according to this embodiment will be described with reference to FIG. 5(a) to 5(h) are cross-sectional views showing a method for manufacturing a flexible printed wiring board according to an embodiment of the present invention.

As shown in FIG. 5A, first, a metal foil 200 having a first main surface (lower surface) 201 and a second main surface (upper surface) 202 is prepared (first step). In this embodiment, although not particularly limited, thick copper is prepared as the metal foil 200 . Here, thick copper is a copper foil having a thickness T ₁ of 35 μm to 2 mm (35 μm≦T ₁ ≦2 mm). As the metal foil 200, for example, other than copper foil, silver foil, gold foil, or the like may be prepared.

Next, an etching mask 401 is formed on the second portion 204 other than the first portion 203 of the metal foil 200 . The etching mask 401 is formed in a shape corresponding to the shape of the pattern of the wiring 20, and has a linear pattern corresponding to the wiring 20 (see FIG. 1) in this embodiment. The first portion 203 in this embodiment is a portion to be half-etched and etched in a post-process, and the second portion 204 is a portion not to be half-etched and etched. The first portion 203 ends up being the space between wires 20 while the second portion 204 ends up being the wire 20 .

The etching mask 401 can be formed using a resist such as dry film resist. In addition, the resist may be a positive resist that makes the portion irradiated with light soluble in the developer and leaves the portion not irradiated with light, or makes the portion irradiated with light insoluble in the developer. It may be a negative type resist that leaves the light-irradiated portion.

As shown in FIG. 5B, the first portion 203 of the metal foil 200 is subjected to half-etching simultaneously from the first and second

main surfaces

201 and 202 to thin the first portion 203. (Second step). Since this half-etching is isotropic etching, the first portion 203 is dissolved radially from the first and second

main surfaces

201 and 202 sides. Therefore, the

surfaces

203a and 203b of the first portion 203 after half-etching are curved rather than flat. In this embodiment, the

surfaces

203a, 203b have a semi-cylindrical shape.

The method for half-etching is not particularly limited, but a spray etching method in which etching is performed by spraying an etchant onto the metal foil from a spray nozzle (not shown) can be used. Moreover, as etching liquid, ferric-chloride aqueous solution, cupric-chloride aqueous solution, etc. can be used, for example. The half-etching method is not limited to the spray etching method. For example, an immersion etching method in which a metal foil is immersed in an etchant may be used. A dry etching method using an etching gas may be used instead of the wet etching method.

In the second step of half-etching, the entire surface of the first portion 203 is half-etched so that the first portion 203 remains along the thickness direction of the metal foil 200 (the Z direction in the drawing). Etching is preferred. As a result, the second portions 204 are not separated from each other over the entire surface of the metal foil 200, and the post-process can be performed while the second portions 204 are connected to each other via the first portion 203. The distance between the second portions 204, etc. can be maintained. Therefore, the positional accuracy of the circuit (wiring 20) of the flexible printed wiring board 1 can be improved.

In the second step, half etching is preferably performed so that the thickness T ₂ of the first portion 203 is 5% to 15% of the thickness T ₁ of the second portion 204 (0 .05×T ₁ ≦T ₂ ≦0.15×T ₁ ). In particular, half-etching is preferably performed so that the thickness T ₂ of the first portion 203 is 7% to 13% of the thickness T ₁ of the second portion 204 (0.07×T ₁ ≦T ₂ ≤ 0.13 x T ₁ ).

The amount of etching of the first portion 203 by half-etching may vary within the plane of the metal foil 200, but the thickness T2 of the _first portion 203 is equal to the thickness T1 of the _second portion 204. If half-etching is performed so as to have a thickness of 5% or more, the first portion 203 can be left over the entire surface of the first portion 203 . As a result, the first portion 203 can be left between the second portions 204, so that the circuit position accuracy of the flexible printed wiring board 1 can be improved. On the other hand, half-etching is performed so that the thickness T2 of the _first portion 203 is 15% or less of the thickness T1 of the _second portion 204, thereby performing a single-sided etching step (fourth step) described later. processing time can be shortened.

Next, as shown in FIG. 5(c), the etching mask 401 is removed. For stripping the etching mask 401, for example, an alkaline aqueous solution such as sodium hydroxide can be used as a stripping solution.

Next, as shown in FIG. 5(d), the base film 10 is attached to the metal foil 200 from the first main surface 201 side (third step). The base film 10 used is the same as the base film 10 described above. By attaching the base film 10 to the metal foil 200 , the surface 203 b of the first portion 203 is covered with the first adhesive layer 12 of the base film 10 .

Next, as shown in FIG. 5( e ), an etching mask 402 is formed on the second main surface 202 side of the second portion 204 . This etching mask 402 can be formed by a method similar to that of the etching mask 401 described above.

Next, as shown in FIG. 5F, the first portion 203 is etched from the second main surface 202 side to remove the first portion 203, thereby forming the wiring 20 (second main surface 202). 4 step). Single-sided etching in the fourth step can be performed by the above-described spray etching method or the like. Since this single-sided etching is isotropic etching like half-etching, the first portion 203 is dissolved radially from the surface 203a.

The first main surface 201 of the metal foil 200 is only half-etched, while the second main surface 202 is half-etched and also single-sided etched. Therefore, the etching amount on the second main surface 202 side is larger than the etching amount on the first main surface 201 side. Therefore, as shown in FIG. 3, the height H2 of the _second curved surface 212 of the wiring 20 is greater than the height H1 of the _first curved surface 211 of the wiring 20 . Furthermore, the width W1 of the _third surface is greater _than the width W2 of the fourth surface. Since half etching is performed from both sides, the width W3 from the _second end 214 to the fifth end 224 is the largest.

Next, as shown in FIG. 5(g), the etching mask 402 is removed. The etching mask 402 can be peeled off by a method similar to that of the etching mask 401 .

Next, as shown in FIG. 5(h), the coverlay 30 is attached to the base film 10 so as to cover the wiring 20 from the second main surface 202 side. This coverlay 30 is similar to the coverlay 30 described above. As described above, the flexible printed wiring board 1 is manufactured.

In the method for manufacturing the flexible printed wiring board 1 as in the present embodiment, after the metal foil 200 is half-etched from both sides, single-sided etching is performed. Processing time required for processing can be reduced. In particular, when using thick copper as in this embodiment, the processing time required for the etching process can be effectively reduced.

In order to evaluate the effect of reducing the processing time according to this embodiment, a copper foil having a thickness of 500 μm was etched in two steps as follows, and the processing times were compared in Examples and Comparative Examples. In the examples and comparative examples, the etching rate of one main surface of the copper foil was set to 10 μm/min.

First, in the example, the copper foil was half-etched from both sides in the first etching, and etched from one side in the second etching. At this time, the amount of etching in the first half-etching was 450 μm, leaving 10% (50 μm) of the thickness of the copper foil. The processing time required at this time was 22.5 minutes, as shown in Table 1 below. The etching amount in the second etching was 50 μm. The processing time required at this time was 5 minutes, as shown in Table 2 below.

On the other hand, in the comparative example, one side of the copper foil was half-etched from one side in the first etching, and one side was etched from the other side in the second etching. The time required for the first etching and the time required for the second etching were 25 minutes, respectively, as shown in Tables 1 and 2 below.

In the example, the total processing time for etching a 500 μm copper foil was 27.5 minutes, while in the comparative example the total processing time was 50 minutes. Thus, it was confirmed that in the example, the processing time could be shortened by 45% compared to the comparative example.

In addition, in this embodiment, the base film 10 is attached to the metal foil 200 after the metal foil 200 is half-etched and before the first portion 203 is removed by single-sided etching. As a result, the first portion 203 can be removed while the position of the second portion 204 that becomes the wiring 20 is fixed on the base film 10. The position of the portion 204 does not shift. Therefore, the positional accuracy of the circuit (wiring 20) of the flexible printed wiring board 1 can be improved.

Also, in this embodiment, the first to fourth

curved surfaces

211, 212, 221, 222 of the wiring 20 are inclined away from each other as they approach the main surface of the flexible printed wiring board 1. FIG. That is, the distance between the wires increases as the distance between the wires approaches the base film 10 and the coverlay 30 . Therefore, in the step of attaching the base film 10 and the coverlay 30 , the spaces between the wirings 20 are easily filled with the first and second

adhesive layers

12 , 32 . Therefore, the distance between the first and second resin layers 11 and 31 and the wiring 20 can be reduced, and the thickness of the flexible printed wiring board 1 can be reduced.

It should be noted that the embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is meant to include all design changes and equivalents that fall within the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Flexible printed wiring board 10... Base film 11... 1st resin layer 12... 1st adhesive layer 20... Wiring 21... 1st surface 211... 1st curved surface 212... 2nd curved surface 213... 1st surface End 214 Second end 215 Third end 22 Second surface 221 Third curved surface 222 Fourth curved surface 223 Fourth end 224 Fifth end 225 Sixth end 23 3rd surface 24 4th surface L ₁ 1st imaginary straight line L ₂ 2nd imaginary straight line 30 Cover lay 31 2nd resin layer 32 2nd adhesion layer 200 Metal foil 201 1st main surface 202 2nd main surface 203 1st part 204

2nd part

401, 402 Etching mask

Claims

A method for manufacturing a wiring board comprising a base material, wiring arranged on the base material, and a coverlay laminated on the base material so as to cover the wiring, the method comprising:
a first step of providing a metal foil having a first major surface and a second major surface;
a second step of thinning the first portion of the metal foil by subjecting the first portion of the metal foil to half-etching simultaneously from the first and second main surface sides;
a third step of attaching the base material to the metal foil from the first main surface side;
a fourth step of forming the wiring by etching the first portion from the second main surface side to remove the first portion;
and a fifth step of attaching the coverlay to the base material so as to cover the wiring from the second main surface side.
A method for manufacturing a wiring board according to claim 1,
The second step includes performing the half-etching on the entire surface of the first portion so that the first portion remains along the thickness direction of the metal foil.
A method for manufacturing a wiring board according to claim 1 or 2,
In the second step, the half-etching is performed so that the thickness of the first portion is 5% to 15% of the thickness of the second portion other than the first portion, which is not subjected to the half-etching. A method of manufacturing a wiring board, comprising:
a substrate;
wiring arranged on the base material;
A flexible printed wiring board comprising a coverlay laminated on the base material so as to cover the wiring,
The wiring is
a first surface and a second surface facing each other along the width direction of the wiring;
a third surface and a fourth surface that connect the first and second surfaces and face each other along the thickness direction of the wiring;
The first surface is
a first curved surface curved to be recessed inside the wiring and having a first end connected to the third surface;
a second curved surface curved to be recessed inside the wiring and having a second end connected to the first curved surface and a third end connected to the fourth surface;
The second surface is
a third curved surface curved to be recessed inside the wiring and having a fourth end connected to the third surface;
a fourth curved surface curved to be recessed inside the wiring and having a fifth end connected to the third curved surface and a sixth end connected to the fourth surface;
A flexible printed wiring board that satisfies the following formula (1).
W 2 <W 1 <W 3 (1)
However, in the above formula ( 1 ), W1 is the width between the first end and the fourth end, and W2 is the width between the second end and the fifth end. and W3 is the width between the third end and the sixth end.
The flexible printed wiring board according to claim 4,
A flexible printed wiring board that satisfies the following formula (2).
H 1 <H 2 (2)
However, H1 is the height from the third plane to the first virtual plane, H2 is the height from the first virtual plane to the fourth plane, and the first virtual plane is a virtual plane passing through the second end and the fifth end.