JP2021057433A - Flexible printed wiring board and manufacturing method thereof - Google Patents

Abstract

To provide a flexible printed wiring board and a manufacturing method thereof that can clearly separate the entire circuit portion and an insulating base material when an image of the flexible printed wiring board is binarized.SOLUTION: A flexible printed wiring board includes an insulating base material and a circuit portion including a copper layer provided on a part of a circuit forming surface of the insulating base material. In the copper layer, a first surface 21a on the side opposite to the circuit forming surface of the insulating base material includes a non-surface region R2 composed of crystal planes other than the surface of the copper layer and roughened, and a surface region S2 composed of the surface of the copper layer. In the surface region, a plurality of first pits 40 having a rectangular opening are formed.SELECTED DRAWING: Figure 3

Description

The present invention relates to a flexible printed wiring board and a method for manufacturing the same.

The flexible printed wiring board generally includes an insulating base material and a circuit portion provided on a part of the circuit forming surface of the insulating base material. Copper is used for the circuit portion of the flexible printed wiring board, and it is known that the method for manufacturing the flexible printed wiring board includes a step of soft-etching the copper foil using an ammonium persulfate-based etching solution. (See, for example, Patent Documents 1 and 2 below).

Japanese Unexamined Patent Publication No. 62-263689 Japanese Unexamined Patent Publication No. 2008-235801

By the way, when the flexible printed wiring board is aligned using the recognition mark of the circuit part, the light is obliquely incident on the circuit forming surface of the insulating base material, and the image pickup device is located at a position facing the circuit part. Is arranged to take an image of the flexible printed wiring board, and the obtained image is binarized. At this time, the circuit portion becomes white and the insulating base material becomes black, so that the circuit portion and the insulating base material can be distinguished from each other.

However, the conventional flexible printed wiring board has the following problems.

That is, when aligning the flexible printed wiring board using the recognition mark, light is incident on the circuit forming surface of the insulating base material at an angle, and the image pickup device is placed at a position facing the circuit portion. When the flexible printed wiring board was imaged and the obtained image was binarized, black portions were sometimes mixed in the white portions in the circuit portion of the obtained image. Therefore, it may not be possible to clearly separate the circuit portion and the insulating base material.

The present invention has been made in view of the above circumstances, and is a flexible printed wiring board capable of clearly separating the entire circuit section and the insulating base material when the image of the flexible printed wiring board is binarized. It is an object of the present invention to provide a manufacturing method.

The present inventors have conducted diligent studies to solve the above problems. As a result, the surface of the copper layer of the circuit portion on the side opposite to the circuit forming surface of the insulating base material is a non- (100) surface region roughened by crystal planes other than the (100) surface of the copper layer. It has a (100) plane region composed of (100) planes of the copper layer, and it has been found that the (100) plane region causes the obtained image to appear black when binarized. Therefore, as a result of further diligent research, the present inventors have found that the above problems can be solved by the following inventions.

That is, the present invention includes an insulating base material and a circuit portion provided on a part of the circuit forming surface of the insulating base material, the circuit portion includes a copper layer, and the copper layer contains the insulating base material. The first surface opposite to the circuit forming surface is composed of a non- (100) plane region roughened by crystal planes other than the (100) plane of the copper layer, and a (100) plane of the copper layer. A flexible printed wiring board having a (100) plane region and forming a plurality of first pits having a quadrangular opening in the (100) plane region.

According to the flexible printed wiring board of the present invention, for example, when aligning using the recognition mark of the flexible printed wiring board, light is obliquely incident on the circuit forming surface of the insulating base material, and the light from the circuit portion is emitted. When the flexible printed wiring board is imaged by receiving light from an imaging device whose optical axis is arranged in a direction orthogonal to the circuit forming surface, the non- (100) surface region of the first surface of the circuit portion is roughened. Therefore, light is scattered in the non- (100) surface region of the first surface of the copper layer of the circuit unit, and the amount of light received by the image pickup apparatus increases. Therefore, when the image of the flexible printed wiring board is binarized, the non- (100) surface region becomes white. On the other hand, since a plurality of first pits having a quadrangular opening are formed in the (100) plane region of the first plane of the circuit portion, a plurality of first pits are formed in the (100) plane region. Compared to the case without it, the light is more likely to be scattered, the amount of light received by the image pickup apparatus is increased, and when the image of the flexible printed wiring board is binarized, the (100) plane region is likely to be white. .. When the obtained image is binarized in this way, the non- (100) plane region on the first surface of the copper layer of the circuit portion becomes white, and the (100) plane region also becomes white, and as a result, the circuit portion The whole becomes white easily. On the other hand, since the circuit forming surface of the insulating base material is smooth, light is incident on the circuit forming surface of the insulating base material at an angle, and the light from the circuit portion is directed by the optical axis in a direction orthogonal to the circuit forming surface. When the image is received by the arranged image pickup device and the flexible printed wiring board is imaged, the light is less likely to be scattered on the circuit forming surface of the insulating base material, the amount of light received by the image pickup device is reduced, and the flexible printed wiring board is used. When the image of the board is binarized, the insulating base material tends to be black. If the position of the image pickup device is changed to a position where the optical axis is arranged in the direction of the reflection angle with respect to the incident light on the circuit forming surface, the circuit section when the image of the flexible printed wiring board is binarized. The non- (100) plane region on the first surface of the copper layer of the copper layer becomes black, the (100) plane region becomes black, and the insulating base material tends to become white. Therefore, according to the flexible printed wiring board of the present invention, when the image of the flexible printed wiring board is binarized, the color uniformity of the entire circuit unit can be improved, and as a result, the entire circuit unit can be improved. And the insulating base material can be clearly separated.

In the flexible printed wiring board, the circuit unit is provided on the copper layer following the shape of the first surface of the copper layer, and further has a protective layer that protects the copper layer, and the protection is provided. In the layer, the second surface opposite to the copper layer corresponds to the non- (100) surface region and is roughened when viewed in the thickness direction of the protective layer. And, even if a plurality of second pits having a (100) surface region corresponding portion corresponding to the (100) surface region and having a rectangular opening are formed in the (100) surface region corresponding portion. Good.

In this case, the protective layer is provided on the copper layer following the shape of the first surface of the copper layer, and in the protective layer, the second surface opposite to the copper layer insulates the circuit portion. When viewed in a direction orthogonal to the circuit forming surface of the above, there is a non- (100) surface region corresponding portion that coincides with the non- (100) plane region and a (100) plane region corresponding portion that coincides with the (100) plane region. However, in the (100) plane region corresponding portion, a plurality of second pits having a quadrangular opening are formed. Therefore, when the image of the flexible printed wiring board is binarized, the non- (100) surface region corresponding portion on the second surface of the circuit unit becomes white or black, and the (100) surface region corresponding portion becomes white or black. It will be easier. Therefore, when the image of the flexible printed wiring board is binarized, the color uniformity of the entire circuit unit can be improved.

Further, the present invention includes a circuit portion forming step of forming a circuit portion including a copper layer in a part of the circuit forming surface of the insulating base material, and the circuit portion forming step is the circuit forming surface of the insulating base material. A copper layer forming step of forming the copper layer is included in a part of the copper layer, and in the copper layer forming step, the first surface of the copper layer opposite to the circuit forming surface of the insulating base material is the copper layer. It has a non- (100) plane region composed of crystal planes other than the (100) plane and a roughened non- (100) plane region, and a (100) plane region composed of (100) planes of the copper layer. Is a method for manufacturing a flexible printed wiring board in which the copper layer is formed so that a plurality of first pits having a quadrangular opening are formed.

According to this manufacturing method, when the image of the flexible printed wiring board is binarized, the color uniformity of the entire circuit section can be improved, and as a result, the entire circuit section and the insulating base material can be clearly defined. A flexible printed wiring board that can be classified can be manufactured.

In the method for manufacturing a flexible printed wiring board, the copper layer forming step includes a copper layer precursor forming step of forming a copper layer precursor on a part of the circuit forming surface of the insulating base material, and the copper layer precursor. In the etching step, the etching solution includes an etching step of forming the copper layer by etching a portion of the body opposite to the circuit forming surface of the insulating base material with an etching solution. Preferably contains a halide ion.

In this case, when the portion of the copper layer precursor opposite to the circuit forming surface of the insulating base material is etched with an etching solution, it has a quadrangular opening in the (100) surface region of the copper layer. A plurality of first pits are effectively formed.

In the method for manufacturing a flexible printed wiring board, the content of the halide ion in the etching solution is preferably 1 mass ppm or more.

In this case, when the portion of the copper layer precursor opposite to the circuit forming surface of the insulating base material is etched with an etching solution, it has a quadrangular opening in the (100) surface region of the copper layer. More first pits can be formed.

According to the present invention, there is provided a flexible printed wiring board and a method for manufacturing the same, which can clearly separate the entire circuit section and the insulating base material when the image of the flexible printed wiring board is binarized.

It is a top view which shows one Embodiment of the flexible printed wiring board of this invention. It is sectional drawing along the line II-II of FIG. It is an enlarged view which shows the part B of a part of the 1st surface of the copper layer of FIG. It is an enlarged view which shows the region A surrounded by the alternate long and short dash line of FIG. It is a figure which shows the state which performs the alignment using the recognition mark with respect to the flexible printed wiring board of FIG. It is sectional drawing which shows the preparatory process of preparing the insulating base material with a copper foil used in the manufacturing method of the flexible printed wiring board of this invention. It is sectional drawing which shows the copper layer precursor formation process of the manufacturing method of the flexible printed wiring board of this invention. It is an enlarged view which shows the region C corresponding to region B of FIG. 3 on the surface of the copper layer precursor of FIG. It is sectional drawing which shows the etching process of the manufacturing method of the flexible printed wiring board of this invention. 8 is a digital microscope image showing the surface of a copper layer precursor in Example 1. It is a digital microscope image which shows the (100) plane area correspondence part of the circuit part in the flexible printed wiring board obtained in Example 1. FIG. It is an SEM image (magnification: 3000 times) which shows the (100) plane area correspondence part of the circuit part in the flexible printed wiring board obtained in Example 1. FIG. It is an SEM image (magnification: 10,000 times) which shows the (100) plane area correspondence part of the circuit part in the flexible printed wiring board obtained in Example 1. FIG. It is an SEM image (magnification: 30,000 times) which shows the (100) plane area correspondence part of the circuit part in the flexible printed wiring board obtained in Example 1. FIG. 6 is an SEM image (magnification: 3000 times) showing a non- (100) surface region corresponding portion of the circuit portion in the flexible printed wiring board obtained in the first embodiment. It is a digital microscope image which shows the (100) plane area correspondence part of the circuit part in the flexible printed wiring board obtained in Example 2. It is a digital microscope image which shows the (100) plane area correspondence part of the circuit part in the flexible printed wiring board obtained in Example 3. It is a digital microscope image which shows the (100) plane area correspondence part of the circuit part in the flexible printed wiring board obtained in the comparative example 1. FIG. It is an SEM image (magnification: 3000 times) which shows the (100) plane area correspondence part of the circuit part in the flexible printed wiring board obtained in the comparative example 1. FIG. (A) is a binarized image of the surface of the flexible printed wiring board obtained in Example 1, and (b) is a (100) plane region corresponding portion of the circuit portion in the flexible printed wiring board obtained in Example 1. It is a digital microscope image. (A) is a binarized image of the surface of the flexible printed wiring board obtained in Example 2, and (b) is a (100) plane region corresponding portion of the circuit portion in the flexible printed wiring board obtained in Example 2. It is a digital microscope image. (A) is a binarized image of the surface of the flexible printed wiring board obtained in Example 3, and (b) is a (100) plane region corresponding portion of the circuit portion of the flexible printed wiring board obtained in Example 3. It is a digital microscope image. (A) is a binarized image of the surface of the flexible printed wiring board obtained in Example 4, and (b) is a (100) plane region corresponding portion of the circuit portion in the flexible printed wiring board obtained in Example 4. It is a digital microscope image. (A) is a binarized image of the surface of the flexible printed wiring board obtained in Example 5, and (b) is a (100) plane region corresponding portion of the circuit portion in the flexible printed wiring board obtained in Example 5. It is a digital microscope image. (A) is a binarized image of the surface of the flexible printed wiring board obtained in Example 6, and (b) is a (100) plane region corresponding portion of the circuit portion in the flexible printed wiring board obtained in Example 6. It is a digital microscope image. (A) is a binarized image of the surface of the flexible printed wiring board obtained in Comparative Example 1, and (b) is a (100) plane region corresponding portion of the circuit portion in the flexible printed wiring board obtained in Comparative Example 1. It is a digital microscope image. (A) is a binarized image of the surface of the structure immediately before the etching process in the manufacturing process of the flexible printed wiring board of Example 1, and (b) is immediately before the etching process in the manufacturing process of the flexible printed wiring board of Example 1. It is a digital microscope image of the surface of the copper layer precursor of the structure of.

[Flexible printed wiring board]
Hereinafter, embodiments of the flexible printed wiring board of the present invention will be described with reference to FIG. 1 is a plan view showing an embodiment of a flexible printed wiring board of the present invention, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a surface of the copper layer of FIG. An enlarged view showing the area B of the part, FIG. 4 is an enlarged view showing the area A surrounded by the alternate long and short dash line of FIG. 1, and FIG. 5 is a position where the recognition mark is used with respect to the flexible printed wiring board of FIG. It is a figure which shows the state which is performing the alignment.

As shown in FIGS. 1 and 2, the flexible printed wiring board 100 includes an insulating base material 10 and a circuit portion 20 provided on a part of the circuit forming surface 10a of the insulating base material 10.

The circuit unit 20 is a protective layer that protects a copper layer 21 provided on a part of the circuit forming surface 10a of the insulating base material 10, and the first surface 21a and the side surface 21b of the copper layer 21 opposite to the circuit forming surface 10a. It has 22 (see FIG. 2).

Further, as shown in the region B surrounded by the alternate long and short dash line in FIG. 3, the first surface 21a of the copper layer 21 is composed of crystal planes other than the (100) plane of the copper layer 21 and is roughened. It has a (100) plane region R2 and a (100) plane region S2 composed of (100) planes of the copper layer 21. Then, in the (100) plane region S2, a plurality of first pits 40 having a quadrangular opening are formed. The side surface 21b of the copper layer 21 is also composed of a non- (100) plane region R2 which is composed of crystal planes other than the (100) plane of the copper layer 21 and is roughened, and the (100) plane of the copper layer 21 (100). A plurality of first pits 40 having a surface region S2 and having a (100) surface region S2 having a quadrangular opening are formed.

On the other hand, as shown in FIG. 4, in the region A surrounded by the alternate long and short dash line in FIG. 1, the second surface 20a on the side opposite to the circuit forming surface 10a of the insulating base material 10 in the protective layer 22 of the circuit unit 20. However, when the protective layer 22 is viewed in the thickness direction thereof, it has a roughened non- (100) surface region corresponding portion R1 and a (100) surface region corresponding portion S1. Here, in the (100) plane region corresponding portion S1, a plurality of second pits 30 having a quadrangular opening are formed.

The protective layer 22 follows the shape of the first surface 21a of the copper layer 21. That is, when the protective layer 22 is viewed in the thickness direction, the non- (100) plane region corresponding portion R1 in FIG. 4 coincides with the non- (100) plane region R2 in FIG. 3, and the (100) plane in FIG. 4 The area corresponding portion S1 coincides with the (100) plane area S2 in FIG.

According to the flexible printed wiring board 100 described above, as shown in FIG. 5, for example, when the flexible printed wiring board 100 is aligned using the recognition mark, it has a ring shape with respect to the circuit forming surface 10a of the insulating base material 10, for example. When light is incident obliquely from the light source L and the light from the circuit unit 20 is received by the image pickup device 110 whose optical axis is arranged in the direction orthogonal to the circuit formation surface 10a, the flexible printed wiring board 100 is imaged. Since the non- (100) surface region corresponding portion R1 of the second surface 20a of the circuit unit 20 is roughened, light is scattered in the non (100) surface region corresponding portion R1 and received by the image pickup apparatus 110. The amount of light is increased. Therefore, when the image of the flexible printed wiring board 100 is binarized, the non- (100) surface region corresponding portion R1 becomes white.

On the other hand, in the (100) surface region corresponding portion S1 of the second surface 20a of the circuit unit 20, since a plurality of second pits 30 having a quadrangular opening are formed, the (100) surface region corresponding portion S1 Compared with the case where the plurality of second pits 30 are not formed, the light is more likely to be scattered, the amount of light received by the image pickup apparatus 110 is increased, and the image of the flexible printed wiring board 100 is binarized. In this case, the (100) surface area corresponding portion S1 tends to be white. In this way, when the image of the flexible printed wiring board 100 is binarized, the non- (100) surface region corresponding portion R1 of the circuit unit 20 tends to be white, and the (100) surface region corresponding portion S1 tends to be white.

On the other hand, since the circuit forming surface 10a of the insulating base material 10 is smooth, light is obliquely incident on the circuit forming surface 10a of the insulating base material 10 and the light from the circuit unit 20 is orthogonal to the circuit forming surface 10a. When the flexible printed wiring board 100 is imaged by receiving light from the image pickup device 110 whose optical axis is arranged in the direction of the light, the light is less likely to be scattered on the circuit forming surface 10a of the insulating base material 10, and is received by the image pickup device 110. When the light amount of the light is reduced and the image of the flexible printed wiring board 100 is binarized, the insulating base material 10 tends to be black.

When the image pickup device 110 is changed to a position where the optical axis is arranged in the direction of the reflection angle with respect to the incident light on the circuit forming surface 20a, the circuit is obtained when the image of the flexible printed wiring board 100 is binarized. The non- (100) surface region corresponding portion R1 of the portion 20 becomes black, the (100) surface region corresponding portion S1 becomes black, and the insulating base material 10 tends to become white.

Therefore, according to the flexible printed wiring board 100, when the image of the flexible printed wiring board 100 is binarized, the color uniformity of the entire circuit unit 20 can be improved. As a result, the entire circuit unit 20 and the insulating base material 10 can be clearly separated.

Next, the insulating base material 10 and the circuit unit 20 will be described in detail.

<Insulating base material>
The material constituting the insulating base material 10 is not particularly limited, and examples of the material constituting the insulating base material 10 include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide resin (PI), and liquid crystal polymer. Polymer (LCP) can be mentioned.

The circuit forming surface 10a of the insulating base material 10 may be smooth. The surface roughness of the circuit forming surface 10a may be smaller than the surface roughness of the (100) surface region corresponding portion S1 of the protective layer 22 of the circuit unit 20, but is preferably 0.5 μm or less. In this case, when the image of the flexible printed wiring board 100 is binarized, for example, the (100) surface region corresponding portion S1 is made white and the circuit forming surface 10a of the insulating base material 10 is easily made black. The surface roughness refers to the average surface roughness measured by an optical surface roughness meter. The surface roughness described below also refers to the average surface roughness measured as described above.

<Circuit part>
The circuit unit 20 has a copper layer 21 and a protective layer 22.

(Copper layer)
The copper layer 21 may be a layer containing copper and is made of copper or a copper alloy. Examples of the copper layer 21 include electrolytic copper foil and rolled copper foil, but the copper layer 21 is preferably rolled copper foil because it has excellent bending resistance. In the rolled copper foil, more surfaces (100) are present than in the electrolytic copper foil, and surfaces other than the (100) surface are mottled.

The surface roughness of the (100) surface region S2 of the copper layer 21 is not particularly limited, but is preferably 0.6 times or less the surface roughness of the non- (100) surface region R2. (100) Specifically, the surface roughness of the surface region S2 is preferably 0.1 μm or less. However, the surface roughness of the (100) surface region S2 is preferably larger than the surface roughness of the circuit forming surface 10a of the insulating base material 10. In this case, when the images of the circuit unit 20 and the insulating base material 10 are binarized, for example, the (100) plane region corresponding portion S1 can be made white and the color of the insulating base material 10 can be easily made black.

Specifically, the surface roughness of the non- (100) plane region R2 is preferably 0.1 μm or more. In this case, when the image of the circuit unit 20 is binarized as compared with the case where the surface roughness of the non- (100) surface region R2 is less than 0.1 μm, for example, the non- (100) surface region corresponding portion R1 Can be made white so that the color of the insulating base material 10 can be made black more easily.

The first pit 40 of the copper layer 21 has a quadrangular opening. Here, the first pit 40 has a bottom surface and an inner peripheral surface connecting the opening and the bottom surface, and has a tapered shape in which the inner peripheral surface tapers in a direction becoming deeper from the first surface 21a of the copper layer 21. It is preferable to have. In this case, since the protective layer 22 has a shape that follows the copper layer 21, the second pit 30 has a bottom surface and an inner peripheral surface connecting the opening and the bottom surface, and the inner peripheral surface is the protective layer 22. It has a tapered shape that tapers from the second surface 20a in the direction of deepening. Therefore, when the light is obliquely incident on the circuit forming surface 10a, the light incident on the second pit 30 is likely to be scattered on the inner peripheral surface of the second pit 30, and is received by the image pickup apparatus 110. The amount of light emitted can be increased, and when the image of the circuit unit 20 is subjected to the binarization processing, the color uniformity of the entire circuit unit 20 can be further improved, and as a result, the circuit unit 20 can be used. The entire 20 and the insulating base material 10 can be more clearly separated.

It is preferable that a plurality of pits having a quadrangular opening are further formed on the bottom surface of the first pit 40. In this case, since the protective layer 22 has a shape that follows the copper layer 21, a plurality of pits having a quadrangular opening are formed on the bottom surface of the second pit 30. Therefore, when the light is obliquely incident on the circuit forming surface 10a, the light incident on the second pit 30 is likely to be scattered on the bottom surface, and the amount of light received by the image pickup apparatus 110 is increased. When the image of the flexible printed wiring board 100 is binarized, the color uniformity of the entire circuit unit 20 can be further improved, and as a result, the entire circuit unit 20 and the insulating base material 10 can be further improved. Can be clearly separated.

(Protective layer)
The protective layer 22 protects the copper layer 21 from rust and the like, and the conductor constituting the protective layer 22 is not particularly limited as long as it protects the copper layer 21 from rust and the like. For example, examples of the conductor constituting the protective layer 22 include gold, nickel, tin, and solder.

Since the protective layer 22 has a shape that follows the copper layer 21, the surface roughness of the (100) surface region corresponding portion S1 of the protective layer 22, the surface roughness of the non- (100) surface region corresponding portion R1, and these. The magnitude relation is the same as the surface roughness of the (100) plane region S2 of the copper layer 21, the surface roughness of the non- (100) plane region R2, and the magnitude relation between them.

Further, the second pit 30 of the protective layer 22 has the same configuration as the first pit 40 of the copper layer 21.

[Manufacturing method of flexible printed wiring board]
Next, the manufacturing method of the flexible printed wiring board 100 described above will be described with reference to FIGS. 6 to 9. FIG. 6 is a cross-sectional view showing a preparatory step for preparing an insulating base material with a copper foil used in the method for manufacturing a flexible printed wiring board of the present invention, and FIG. 7 is a cross-sectional view showing copper in the method for manufacturing a flexible printed wiring board of the present invention. FIG. 8 is a cross-sectional view showing a layer precursor forming step, FIG. 8 is an enlarged view showing a region C corresponding to a region B of FIG. 3 on the surface of the copper layer precursor of FIG. 7, and FIG. 9 is an enlarged view of the present invention. It is sectional drawing which shows the etching process of the manufacturing method of a flexible printed wiring board.

First, as shown in FIG. 6, a copper-clad laminate in which a copper foil 221 is formed on the entire surface of the circuit forming surface 10a of the insulating base material 10 is prepared.

Next, when the surface of the copper foil 221 is covered with a rust preventive film, the rust preventive film is removed with a sulfuric acid / hydrogen peroxide-based soft etching solution.

Next, as shown in FIG. 7, the copper layer precursor 121 is formed by photolithography (copper layer precursor forming step).

At this time, the photolithography is specifically performed as follows. That is, first, the copper foil 221 is covered with a resist to expose the resist, and then development is performed to expose a part of the copper foil 221. Next, the exposed copper foil 221 is etched with, for example, a copper chloride / iron chloride etching solution. Finally, the resist is peeled off.

The copper layer precursor 121 is in a state before the etching step, and in the region C corresponding to the region B in FIG. 3, the first pit 40 is not formed in the (100) plane region S1 (FIG. 3). 8).

Next, after forming a coverlay and a solder resist so as to expose the copper layer precursor 121, the exposed copper layer precursor 121 is etched with an etching solution described later (etching step). As shown in 9, the copper layer 21 is formed (copper layer forming step).

At this time, in the copper layer 21, the first surface 21a and the side surface 21b of the copper layer 21 are a non- (100) surface region R2 in which the first surface 21a and the side surface 21b are crystal planes other than the (100) surface of the copper layer 21, and the (100) surface of the copper layer 21. ) Is formed to have a (100) plane region S2 composed of planes. Further, at this time, the copper layer 21 is formed so that a plurality of first pits 40 having a quadrangular opening are formed in the (100) plane region S2. Further, the etching performed in the etching step is so-called soft etching, and the etching amount is set to, for example, 0.2 to 2 μm.

Next, electrolytic or electroless plating is performed on the first surface 21a of the copper layer 21 to form the protective layer 22.

At this time, the protective layer 22 is formed so as to follow the surface shape of the copper layer 21 and so that the surface shape of the second surface 20a is the same as the surface shape of the first surface 21a. Further, the protective layer 22 is formed so that the second surface 20a has a roughened non- (100) surface region corresponding portion R1 and a (100) surface region corresponding portion S1. Further, the protective layer 22 is formed so that a plurality of second pits 30 having a quadrangular opening are formed in the (100) surface region corresponding portion S1.

In this way, the production of the flexible printed wiring board 100 is completed.

When the flexible printed wiring board 100 is manufactured as described above, the color uniformity of the entire circuit unit 20 can be improved when the image of the flexible printed wiring board 100 is binarized, and as a result, the circuit It is possible to manufacture a flexible printed wiring board 100 capable of clearly separating the entire portion 20 and the insulating base material 10.

Next, the etching solution used for the soft etching of the copper layer precursor 121 described above will be described in detail.

The etching solution may be used as long as it is possible to perform soft etching on the copper layer precursor 121 and form the first pit 40 in the (100) surface region S2 of the first surface 21a of the copper layer 21. Therefore. In addition, the etching solution contains a persulfate and a halide ion.

Examples of the persulfate include ammonium persulfate and sodium persulfate. These can be used alone or in combination.

Examples of the halide ion include chloride ion, bromide ion and fluoride ion. Of these, chloride ion is preferable. In this case, the first pit 40 can be formed more effectively in the (100) plane region S2 of the first plane 21a.

The concentration of persulfate is not particularly limited, but may be, for example, 2 to 200 g / L.

The concentration of the halide ion is not particularly limited, but is preferably 1 mass ppm or more. In this case, when the copper layer precursor 121 is etched with an etching solution, more first pits 40 having a quadrangular opening can be formed in the (100) plane region S2 of the copper layer 21. it can. However, the concentration of the halide ion is preferably 100 mass ppm or less. In this case, the shape of the circuit unit 20 can be made better than that in the case where the concentration of the halide ion exceeds 100 mass ppm.

The material for supplying the halogenated ion is not particularly limited, and examples of such a material include sodium halide, hydrogen halide, calcium halide, and the like.

The etching solution may further contain sulfuric acid or the like, if necessary.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the circuit unit 20 has the copper layer 21 and the protective layer 22, but the circuit unit 20 does not have to have the protective layer 22. Even in this case, since the surface shape of the first surface 21a of the copper layer 21 is the same as the surface shape of the second surface 20a, when the image of the flexible printed wiring board 100 is binarized, the entire circuit unit 20 is subjected to the binarization process. The color uniformity can be improved, and the entire circuit unit 20 and the insulating base material 10 can be clearly separated.

Further, in the above embodiment, the circuit unit 20 is provided only on the circuit forming surface 10a of the insulating base material 10, but the circuit unit 20 is provided on the surface of the insulating base material 10 opposite to the circuit forming surface 10a. You may.

Hereinafter, the content of the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

(Example 1)
First, a copper-clad laminate in which a copper foil was formed on the entire surface of the circuit forming surface of the insulating base material, and a copper-clad laminate using HA-V2 foil (manufactured by JX Nippon Mining & Metals Co., Ltd.) as the copper foil was prepared. At this time, the surface roughness of the circuit forming surface was 0.05 μm. Next, the rust preventive film covering the copper foil was removed with a sulfuric acid / hydrogen peroxide-based soft etching solution. Next, a copper layer precursor was formed by photolithography. Specifically, the copper foil was covered with a resist to expose the resist, and then development was performed to expose a part of the copper foil. Next, the exposed copper foil was etched with a copper chloride / iron chloride etching solution. Finally, the resist was peeled off. In this way, a copper layer precursor was formed. A digital microscope image of the surface of the copper layer precursor is shown in FIG.
Next, a coverlay and a solder resist were formed so as to expose the copper layer precursor.

Next, hydrochloric acid was added as a halide ion feeder to an aqueous solution of 100 g / L of ammonium persulfate and 15 mL / L of 89% sulfuric acid so that the concentration of chloride ions was 10 ppm to prepare an etching solution.

Next, using this etching solution, only a portion having a thickness of 1.00 micron in the copper layer precursor was etched to form a copper layer.

Finally, the copper layer was gold-plated to prevent rust, and a protective layer was formed so as to cover the copper layer. In this way, a circuit portion was formed on the insulating base material to produce a flexible printed wiring board.

With a mounter as a component mounting machine (product name "i-cubeII, manufactured by YAMAHA"), a CCD camera is mounted on the obtained flexible printed wiring board so that the optical axis is arranged in a direction orthogonal to the circuit forming surface. Arranged, using a ring-shaped light source, light is incident diagonally on the circuit forming surface of the insulating base material, and the light from the circuit section and the circuit forming surface is received by the CCD camera to image the flexible printed wiring board. The results are shown in FIG. 11. FIG. 11 shows a digital microscope image of the (100) plane region corresponding portion of the circuit portion in the flexible printed wiring board of the first embodiment. For the flexible printed wiring board, SEM observation was also performed on the (100) surface area corresponding part and the non- (100) surface area corresponding part of the circuit part. The results are shown in FIGS. Is an SEM image of the (100) surface area corresponding portion when the magnification is 3,000 times, 10,000 times, and 30,000 times, and FIG. 15 shows the SEM of the non- (100) surface area corresponding portion when the magnification is 3,000 times. As shown in FIGS. 11 to 14, a plurality of first pits were formed in the (100) surface region corresponding portion. Further, the (100) plane region corresponding portion and the non- (100) surface region corresponding portion of the circuit portion were formed. ) The surface roughness in the surface area corresponding portion was measured with a digital microscope VHX-7000 (manufactured by KEYENCE). The results are shown in Table 1.

(Example 2)
When preparing the etching solution, sodium chloride was used instead of hydrochloric acid as the halide ion supply substance, and the surface roughness of the (100) surface region corresponding portion and the non- (100) surface region corresponding portion of the circuit section is shown in Table 1. A flexible printed wiring board was produced in the same manner as in Example 1 except as shown. For the obtained flexible printed wiring board, the circuit portion of the flexible printed wiring board was imaged in the same manner as in Example 1. The results are shown in FIG. Note that FIG. 16 shows a digital microscope image of the (100) plane region corresponding portion of the circuit portion in the flexible printed wiring board of the second embodiment. As shown in FIG. 16, a plurality of first pits were formed in the (100) plane region corresponding portion.

(Example 3)
When preparing the etching solution, calcium chloride was used instead of hydrochloric acid as the halide ion supply substance, and the surface roughness in the (100) plane region corresponding portion and the non- (100) plane region corresponding portion of the circuit part is shown in Table 1. A flexible printed wiring board was produced in the same manner as in Example 1 except as shown. For the obtained flexible printed wiring board, the circuit portion of the flexible printed wiring board was imaged in the same manner as in Example 1. The results are shown in FIG. Note that FIG. 17 shows a digital microscope image of the (100) plane region corresponding portion of the circuit portion in the flexible printed wiring board of the third embodiment. As shown in FIG. 17, a plurality of first pits were formed in the (100) plane region corresponding portion.

(Example 4)
When preparing the etching solution, the concentration of hydrochloric acid was changed from 10 mass ppm to 1 mass ppm, and the surface roughness of the (100) surface region corresponding portion and the non- (100) surface region corresponding portion of the circuit section is shown in Table 1. A flexible printed wiring board was produced in the same manner as in Example 1 except as shown. For the obtained flexible printed wiring board, the circuit portion of the flexible printed wiring board was imaged in the same manner as in Example 1. As a result, a plurality of first pits were formed in the (100) plane region corresponding portion.

(Example 5)
When preparing the etching solution, the concentration of hydrochloric acid was changed from 10 mass ppm to 2 mass ppm, and the surface roughness of the (100) surface region corresponding portion and the non- (100) surface region corresponding portion of the circuit section is shown in Table 1. A flexible printed wiring board was produced in the same manner as in Example 1 except as shown. For the obtained flexible printed wiring board, the circuit portion of the flexible printed wiring board was imaged in the same manner as in Example 1. As a result, a plurality of first pits were formed in the (100) plane region corresponding portion.

(Example 6)
When preparing the etching solution, the concentration of hydrochloric acid was changed from 10 mass ppm to 0.5 mass ppm, and the surface roughness of the (100) surface region corresponding portion and the non- (100) surface region corresponding portion of the circuit part was shown. A flexible printed wiring board was produced in the same manner as in Example 1 except as shown in 1. For the obtained flexible printed wiring board, the circuit portion of the flexible printed wiring board was imaged in the same manner as in Example 1. As a result, a plurality of first pits were formed in the (100) plane region corresponding portion.

(Comparative Example 1)
A flexible printed wiring board was produced in the same manner as in Example 1 except that hydrochloric acid was not used when preparing the etching solution. For the obtained flexible printed wiring board, the circuit portion of the flexible printed wiring board was imaged in the same manner as in Example 1. The results are shown in FIG. Note that FIG. 18 shows a digital microscope image of the (100) plane region corresponding portion of the circuit portion in the flexible printed wiring board of Comparative Example 1. Further, for the flexible printed wiring board of Comparative Example 1, SEM observation of the (100) plane region corresponding portion of the circuit portion was also performed. The results are shown in FIG. FIG. 19 is an SEM image of the (100) plane region corresponding portion when the magnification is increased to 3000 times. As shown in FIGS. 18 to 19, a plurality of first pits are formed in the (100) plane region corresponding portion. At this time, the surface roughness of the (100) surface region corresponding portion and the non- (100) surface region corresponding portion of the circuit portion was measured in the same manner as in Example 1. The results are shown in Table 1.

<Evaluation of binarization processing>
The surfaces of the flexible printed wiring boards obtained before the etching of Examples 1 to 6 and Comparative Example 1 were binarized by a component mounting machine (product name "i-cubeII", manufactured by YAMAHA). The results are shown in Table 1 and FIGS. 20-27. In FIGS. 20 to 27, (a) shows a binarized image, and (b) shows a digital microscope image. Further, in Table 1, “◯”, “Δ” and “×” are based on the following criteria.

〇… The division between the entire circuit section and the insulating base material is very clear △… The division between the entire circuit section and the insulating base material is clear ×… The division between the entire circuit section and the insulating base material is very unclear.

From the results shown in FIGS. 20 to 27, it was found that in Examples 1 to 6, the entire first surface of the circuit portion can be made white, and the entire circuit portion and the insulating base material can be clearly separated.

On the other hand, in Comparative Example 1, many smooth regions were distributed on the second surface of the circuit unit, and the entire first surface of the circuit unit could not be whitened.

From the above, it was confirmed that according to the present invention, when the image of the flexible printed wiring board is binarized, the entire circuit section and the insulating base material can be clearly separated.

The flexible printed wiring board of the present invention can improve the color uniformity of the entire circuit section when the image of the flexible printed wiring board is binarized. Therefore, the flexible printed wiring board of the present invention is not only used for clearly separating the entire circuit section and the insulating base material when aligning the flexible printed wiring board with the recognition mark, but also for foreign matter. It can also be applied to the binarization process of the image of the circuit part and the optical inspection for separating the BVH (Bullied Via Hole) formed after the fact and the image of the circuit part by the binarization process. In the flexible printed wiring board, the circuit portion may be replaced with solid copper (unprocessed copper layer). In this case, this structure can also be applied to a binarization process of an image of a foreign substance and a copper layer, an optical inspection for separating the two by a binarization process of an image of a BVH formed after the fact and an image of a circuit portion, and the like.

10 ... Insulation base material 10a ... Circuit forming surface 20 ... Circuit part 20a ... Second surface 21 ... Copper layer 21a ... First surface 22 ... Protective layer 30 ... Second pit 40 ... First pit 100 ... Flexible printed wiring board 121 ... Copper layer precursor S1 ... (100) plane region corresponding portion S2 ... (100) plane region R1 ... non (100) plane region corresponding portion R2 ... non (100) plane region

Claims (5)

Insulating base material and
A circuit portion provided on a part of the circuit forming surface of the insulating base material is provided.
The circuit portion includes a copper layer, and in the copper layer, the first surface of the insulating base material opposite to the circuit forming surface is formed of a crystal plane other than the (100) plane of the copper layer and is roughened. It has a non- (100) plane region and a (100) plane region composed of (100) planes of the copper layer.
A flexible printed wiring board in which a plurality of first pits having a quadrangular opening are formed in the (100) plane region. The circuit unit is provided on the copper layer following the shape of the first surface of the copper layer, and further has a protective layer that protects the copper layer.
In the protective layer, the second surface opposite to the copper layer is a roughened non- (100) surface region that coincides with the non- (100) surface region when viewed in the thickness direction of the protective layer. It has a corresponding portion and a (100) plane region corresponding portion that matches the (100) plane region.
The flexible printed wiring board according to claim 1, wherein a plurality of second pits having a quadrangular opening are formed in the (100) surface region corresponding portion. A circuit portion forming step of forming a circuit portion including a copper layer is included in a part of the circuit forming surface of the insulating base material.
The circuit portion forming step includes a copper layer forming step of forming the copper layer on a part of the circuit forming surface of the insulating base material.
In the copper layer forming step, the first surface of the copper layer opposite to the circuit forming surface of the insulating base material is a non-roughened surface composed of crystal planes other than the (100) plane of the copper layer. A plurality of first pits having a (100) plane region and a (100) plane region composed of (100) planes of the copper layer and having a quadrangular opening are formed in the (100) plane region. A method for manufacturing a flexible printed wiring board that forms the copper layer as described above. The copper layer forming step
A copper layer precursor forming step of forming a copper layer precursor on a part of the circuit forming surface of the insulating base material, and
The copper layer precursor includes an etching step of forming the copper layer by etching a portion of the insulating base material opposite to the circuit forming surface with an etching solution.
The method for manufacturing a flexible printed wiring board according to claim 3, wherein in the etching step, the etching solution contains halide ions. The method for manufacturing a flexible printed wiring board according to claim 4, wherein the content of the halide ion in the etching solution is 1 mass ppm or more.

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