JP7528600B2 - METAL CLAD SUBSTRATE MANUFACTURING METHOD AND VACUUM FILM DEPOSITION APPARATUS - Google Patents

Description

The present invention relates to a method for manufacturing a metal-clad substrate and a vacuum deposition apparatus. More specifically, the present invention relates to a method for manufacturing a metal-clad substrate used in the manufacture of flexible printed circuit boards (FPCs) and the like, and a vacuum deposition apparatus used in the manufacture of metal-clad substrates.

Flexible printed wiring boards, in which wiring patterns are formed on the surface of a resin film, are used in electronic devices such as liquid crystal panels, notebook computers, digital cameras, and mobile phones. Flexible printed wiring boards are manufactured from metal-clad substrates, in which the surface of a resin film is covered with a metal layer. Metal-clad substrates are obtained by forming a metal layer on the surface of a resin film by a vacuum film-forming method, or by a combination of a vacuum film-forming method and an electrolytic plating method (for example, Patent Document 1).

JP 2020-012156 A

To form metal layers on both sides of a long strip of resin film using the vacuum deposition method, a metal layer is formed on the first side of the resin film while the resin film is transported by roll-to-roll, and then a metal layer is formed on the second side. While being transported by roll-to-roll, the resin film comes into contact with multiple rolls.

Generally, resin films contain fillers, which form unevenness on the surface of the resin film. These unevenness prevents the resin film from becoming charged and sticking to the roll, improving the transportability of the resin film. However, after a metal layer is formed on the surface of the resin film, if the metal layer side of the resin film comes into contact with a roll, the parts of the metal layer formed on the convex parts of the resin film may peel off, resulting in pinholes. In particular, when metal layers are formed on both sides of a resin film, the metal layer formed on the first side comes into contact with many rolls while the metal layer is being formed on the second side, which makes it easy for pinholes to occur.

In view of the above circumstances, the present invention aims to provide a manufacturing method for metal-clad substrates and a vacuum deposition apparatus that can suppress the occurrence of pinholes caused by contact between the metal layer and the roll.

The manufacturing method of the first invention for producing a metal-clad substrate comprises a first vacuum film formation process in which a first metal thin film layer is formed on a first surface of a base film by a vacuum film formation method while transporting the base film by roll-to-roll, and an adhesive film is attached to the surface of the first metal thin film layer to obtain a substrate intermediate product; a second vacuum film formation process in which a second metal thin film layer is formed on a second surface of the base film by a vacuum film formation method while transporting the substrate intermediate product by roll-to-roll, to obtain a metal-clad substrate; and an electrolytic plating process in which the adhesive film is peeled off while transporting the metal-clad substrate by roll-to-roll, and a plating film is formed on both surfaces of the metal-clad substrate by electrolytic plating , wherein after the adhesive film is peeled off and before the plating film is formed, organic matter remaining on the surface of the first metal thin film layer is removed by atmospheric pressure plasma, and the adhesive film is a self-adhesive film having an adhesive layer made of an adhesive resin .
A second aspect of the present invention is a method for manufacturing a metal-clad substrate according to the first aspect of the present invention, characterized in that the first vacuum film-forming step and the second vacuum film-forming step are carried out continuously in a single vacuum film-forming apparatus.
The manufacturing method for a metal-clad substrate of the third invention is characterized in that, in the first invention, in the first vacuum film-forming process, the base film is unwound and the intermediate substrate is wound up, and in the second vacuum film-forming process, the intermediate substrate is unwound and the metal-clad substrate is wound up .

According to the first invention, the second metal thin film layer is formed after the adhesive film is attached to the first metal thin film layer, so that the first metal thin film layer and the roll do not come into direct contact during the formation of the second metal thin film layer. Therefore, it is possible to suppress the occurrence of pinholes caused by the contact between the first metal thin film layer and the roll. In addition, since the adhesive layer is made of a resin with a low content of organic solvent, even if the adhesive film is placed in a vacuum film forming device, it is possible to suppress the adhesive layer from collapsing and scattering due to the volatilization of the organic solvent. Furthermore, since the organic matter remaining on the surface of the first metal thin film layer is removed after the adhesive film is peeled off, it is possible to suppress the organic matter from remaining inside the conductor layer.
According to the second aspect of the present invention, a double-sided vacuum deposition apparatus can be used to deposit metal thin film layers on both sides of the base film while suppressing the occurrence of pinholes in the first metal thin film layer.
According to the third aspect of the present invention, a single-sided vacuum deposition apparatus can be used to deposit metal thin film layers on both sides of the base film while suppressing the occurrence of pinholes in the first metal thin film layer .

1A to 1C are process diagrams illustrating a method for manufacturing a metal-clad substrate according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram of a vacuum film-forming apparatus using a double-sided film-forming method. FIG. 1 is an explanatory diagram of a vacuum film-forming apparatus for a single-sided film-forming method. FIG. 13 is an explanatory diagram of another example of a vacuum film formation apparatus for a single-sided film formation method.

Next, an embodiment of the present invention will be described with reference to the drawings.
First Embodiment
The manufacturing method of the metal-clad substrate 10 according to the first embodiment of the present invention includes at least a first vacuum film-forming step and a second vacuum film-forming step. By carrying out the first vacuum film-forming step and the second vacuum film-forming step in this order, the metal-clad substrate 10 can be manufactured from the base film 11 as shown in FIG. 1. Furthermore, if necessary, an electrolytic plating step is carried out after the second vacuum film-forming step. This allows the manufacturing of a metal-clad substrate 10t having a thick conductor layer.

The metal-clad substrate 10 is formed by covering the surface of the base film 11 with a metal layer. The composition of the metal layer is not particularly limited, but may be copper, for example. A metal-clad substrate 10 in which the metal layer is made of copper is called a copper-clad laminate.

(First vacuum film forming process)
The first vacuum film-forming step is performed while the base film 11 is being transported by roll-to-roll. The base film 11 is a long strip-shaped film having insulating properties. The base film 11 may be a polyimide film, a liquid crystal polymer film, a polyethylene terephthalate film, or the like. A resin film such as a plastic film can be used. Although not particularly limited, the thickness of the base film 11 is generally 10 to 100 μm. Hereinafter, one of the main surfaces of the base film 11 is referred to as a first surface 11a. The other main surface is referred to as a second surface 11b (see FIG. 1(1)).

In the first vacuum deposition process, a first metal thin film layer 12A is deposited on the first surface 11a of the base film 11 by a vacuum deposition method. Vacuum deposition methods are divided into physical vapor deposition and chemical vapor deposition. Physical vapor deposition methods are further divided into deposition and sputtering. Among these, sputtering is preferably used.

The first metal thin film layer 12A may be a single layer made of one type of metal or alloy, or may be a laminate of multiple layers made of different types of metals or alloys. For example, the first metal thin film layer 12A may be a single copper thin film layer. The first metal thin film layer 12A may also be a copper thin film layer laminated onto an underlying metal layer made of nickel, chromium, or a nickel-chromium alloy. In this case, although not particularly limited, the thickness of the underlying metal layer is typically 5 to 50 nm, and the thickness of the copper thin film layer is typically 50 to 400 nm.

In addition, in the first vacuum film formation process, the first metal thin film layer 12A is formed on the first surface 11a of the base film 11, and then an adhesive film 20 is attached to the surface of the first metal thin film layer 12A. Hereinafter, the product in which the first metal thin film layer 12A is formed on the base film 11 and the adhesive film 20 is attached to the first metal thin film layer 12A is referred to as the substrate intermediate product 10i (see (2) in FIG. 1).

(Second vacuum film forming process)
The second vacuum film-forming step is performed while the intermediate substrate 10i is being transported by roll-to-roll. In the second vacuum film-forming step, the second metal thin film layer 12B is formed on the second surface 11b of the base film 11 by a vacuum film-forming method. As a result, a metal-clad substrate 10 is obtained in which the metal thin film layers 12A and 12B are formed on both sides of the base film 11 (see (3) in FIG. 1). The composition, structure and thickness of the second metal thin film layer 12A may be the same as those of the first metal thin film layer 12A.

As described above, the adhesive film 20 is attached to the first metal thin film layer 12A, and then the second metal thin film layer 12B is formed. Therefore, the first metal thin film layer 12A does not come into direct contact with the transport roll during the formation of the second metal thin film layer 12B. This makes it possible to suppress the occurrence of pinholes caused by contact between the first metal thin film layer 12A and the roll.

(Electrolytic plating process)
The electrolytic plating process is performed as necessary. In the electrolytic plating process, a plating film 13 is formed on both sides of the metal-clad substrate 10 by electrolytic plating to obtain a metal-clad substrate 10t having a thick conductor layer (see (4) in FIG. 1). The composition of the plating film 13 is not particularly limited, but is copper when a copper-clad laminate is to be obtained as the metal-clad substrate 10t. The thickness of the plating film 13 is not particularly limited, but is generally 1 to 12 μm.

Electrolytic plating is performed while the metal-clad substrate 10 is being transported by roll-to-roll. Here, in the transport path of the metal-clad substrate 10, the adhesive film 20 is peeled off from the metal-clad substrate 10, and then electrolytic plating is performed.

When the adhesive film 20 is peeled off from the metal-clad substrate 10, organic matter originating from the adhesive layer 22 of the adhesive film 20 may remain on the surface of the first metal thin film layer 12A. If the plating film 13 is formed with the organic matter remaining, defects such as unevenness and discoloration will occur in the plating film 13.

Therefore, in the transport path of the metal-clad substrate 10, after peeling off the adhesive film 20 and before forming the plating film 13, it is preferable to irradiate the surface of the first metal thin film layer 12A with atmospheric pressure plasma. Organic matter remaining on the surface of the first metal thin film layer 12A is removed by the atmospheric pressure plasma. This makes it possible to prevent organic matter from remaining inside the conductor layer.

An atmospheric pressure plasma processing apparatus is used for irradiating atmospheric pressure plasma. The atmospheric pressure plasma processing apparatus has two electrodes arranged opposite each other, a power supply that applies a voltage between the electrodes, and a gas supply unit that supplies gas between the electrodes. Generally, a power supply capable of applying a medium frequency voltage (MHz), a high frequency voltage (MHz), or a microwave voltage (GHz) is used. When gas is introduced between the electrodes to which a voltage is applied, the gas becomes in a plasma state. The gas in the plasma state is irradiated onto the surface of the first metal thin film layer 12A.

The plasma gas used in the plasma treatment may be He, Ne, Ar, Kr, Xe, _N2 , etc. The plasma gas may contain oxygen to enhance the effect of cleaning the surface of the first metal thin film layer 12A.

(Vacuum deposition equipment)
The first vacuum film-forming step and the second vacuum film-forming step are performed, for example, by using a vacuum film-forming apparatus 3 shown in Fig. 2. Note that Fig. 2 illustrates the configuration of a sputtering apparatus.

The vacuum film-forming apparatus 3 is an apparatus that performs vacuum film formation on the long strip-shaped film-forming object D1 while transporting the film-forming object D1 by roll-to-roll, thereby manufacturing the film-formed object D2. In particular, the vacuum film-forming apparatus 3 shown in FIG. 2 is an apparatus that performs film formation on both sides of the film-formed object D1 in a single transport. In this embodiment, the film-formed object D1 is a base film 11, and the film-formed object D2 is a metal-clad substrate 10.

The vacuum coating device 3 has a vacuum chamber 30. Inside the vacuum chamber 30, an unwinding section 31 and a winding section 35 are arranged. The unwinding section 31 unwinds the coating target D1 from a coating target roll in which the coating target D1 is wound into a roll. The winding section 35 winds up the coating target D2 to form a coating target roll. The coating target D1 is transported from the unwinding section 31 to the winding section 35.

Two film-forming units 32, 34, i.e., a first film-forming unit 32 and a second film-forming unit 34, are arranged on the transport path of the film-forming product D1. The first film-forming unit 32 forms a first metal thin film layer 12A on the first surface (first surface 11a of the base film 11) of the film-forming product D1. The second film-forming unit 34 forms a second metal thin film layer 12B on the second surface (second surface 11b of the base film 11) of the film-forming product D1.

In the case of a sputtering device, each deposition section 32, 34 consists of a can roll for cooling the deposition target D1, and multiple sputtering cathodes arranged around the can roll. A target is attached to each sputtering cathode on the surface facing the can roll. Film deposition is performed by depositing sputtered particles ejected from the target on the surface of the deposition target D1. Therefore, a metal or alloy with the same composition as the first and second metal thin film layers 12A, 12B is usually selected as the target.

A film attachment unit 33 is disposed between the two deposition units 32, 34 on the transport path of the film-formed product D1. The film attachment unit 33 unrolls the adhesive film 20 from an adhesive film roll in which the adhesive film 20 is wound in a roll shape, and attaches the adhesive film 20 to the surface of the first metal thin film layer 12A formed on the film-formed product D1.

Inside the vacuum chamber 30, various rolls are provided that define the transport path of the film-formed product D1. Examples of such rolls include a free roll, a tension sensor roll, and a feed roll. The film-formed product D1 is wound around these rolls and transported.

As described above, inside the vacuum chamber 30, the unwinding section 31, the first film-forming section 32, the film application section 33, the second film-forming section 34, and the winding section 35 are arranged in this order from upstream to downstream along the transport path of the film-formed product D1. Therefore, by transporting the film-formed product D1 once, the first vacuum film-forming process can be performed in the first film-forming section 32 and the film application section 33, and then the second vacuum film-forming process can be performed in the second film-forming section 34. In other words, the first vacuum film-forming process and the second vacuum film-forming process can be performed consecutively within a single vacuum film-formation device 3.

In addition, since the second film forming unit 34 is disposed after the film attachment unit 33, the second metal thin film layer 12B is formed after the adhesive film 20 is attached to the surface of the first metal thin film layer 12A. Since the first metal thin film layer 12A does not come into direct contact with the roll (e.g., the can roll of the second film forming unit 34) during the formation of the second metal thin film layer 12B, the occurrence of pinholes due to contact between the first metal thin film layer 12A and the roll can be suppressed.

In addition, since the vacuum deposition device 3 is a double-sided deposition device, by transporting the base film 11 once, it is possible to deposit the metal thin film layers 12A and 12B on both sides of the base film 11 while suppressing the occurrence of pinholes in the first metal thin film layer 12A.

(Adhesive film)
The adhesive film 20 has adhesiveness that allows it to stick to the surface of the first metal thin film layer 12A. If a non-adhesive film were simply placed on the surface of the first metal thin film layer 12A, the first metal thin film layer 12A and the film would rub against each other during transport of the base film 11, causing scratches on the surface of the first metal thin film layer 12A. In contrast, the adhesive film 20 does not rub against the first metal thin film layer 12A, and therefore can prevent scratches on the surface of the first metal thin film layer 12A.

In the case of a sputtering device, if a film is interposed between the can roll of the second film forming section 34 and the film-formed product D1, the cooling efficiency of the can roll for the film-formed product D1 decreases. This can cause heat to accumulate in the film-formed product D1, which can lead to heat-induced wrinkles. However, because heat transfer in a vacuum is dominated by contact heat transfer, using the adhesive film 20 makes it easier to transfer heat from the film-formed product D1 to the can roll compared to using a non-adhesive film. Therefore, using the adhesive film 20 allows the film-formed product D1 to be sufficiently cooled, and the occurrence of wrinkles can be suppressed.

The adhesive film 20 is applied inside the vacuum deposition device 3, i.e., under vacuum. If the adhesive film 20 is applied in air, air may get in between the first metal thin film layer 12A and the adhesive film 20. This may cause problems with the deposition of the second metal thin film layer 12B. By applying the adhesive film 20 under vacuum, such problems can be prevented.

As shown in FIG. 1 (2), the adhesive film 20 is composed of a base layer 21 and an adhesive layer 22. The material of the base layer 21 is not particularly limited, but biaxially oriented polypropylene (OPP) or the like is used. The adhesive film 20 is preferably a film having so-called self-adhesive properties. In other words, the adhesive layer 22 is preferably made of a resin having adhesive properties, rather than an adhesive. For example, as disclosed in JP 2008-6815 A, a self-adhesive layer made of 50 to 80% by weight of a hydrogenated styrene-based elastomer and 50 to 20% by weight of a propylene-α-olefin random copolymer can be used.

Adhesives usually contain a large amount of organic solvent. When an adhesive containing an organic solvent with a particularly low vapor pressure (low molecular weight) is placed inside the vacuum chamber 30, the organic solvent evaporates and the adhesive becomes brittle. This can cause the adhesive layer to crumble and scatter, contaminating the inside of the vacuum chamber 30 or foreign matter to adhere to the film-forming surface, causing problems in subsequent processes (e.g., electrolytic plating).

On the other hand, if the adhesive layer 22 is made of a resin with a low content of organic solvent, even if the adhesive film 20 is placed in the vacuum deposition device 3, the adhesive layer 22 can be prevented from crumbling and scattering due to the evaporation of the organic solvent. Therefore, problems caused by the adhesive layer 22 scattering can be prevented.

Second Embodiment
As shown in Fig. 3, a vacuum film-forming apparatus 4 of a single-sided film-forming type may be used in which a film is formed on one side of a film-forming target object D1 in one transport. The vacuum film-forming apparatus 4 has a vacuum chamber 30. Inside the vacuum chamber 30, an unwinding section 31, a first film-forming section 32, a film application section 33, and a winding section 35 are arranged in this order from upstream to downstream along the transport path of the film-forming target object D1. Note that a second film-forming section 34 is not arranged.

When using a vacuum film-forming apparatus 4 with a single-sided film-forming method, the first vacuum film-forming process and the second vacuum film-forming process are performed in two stages. That is, in the first vacuum film-forming process, a base film 11 is set in the vacuum film-forming apparatus 4 as the product D1 to be film-formed. Then, the base film 11 is unwound, the first metal thin film layer 12A is formed, the adhesive film 20 is attached, and the intermediate substrate product 10i (film-formed product D2) is wound up in this order. The first metal thin film layer 12A is formed in the first film-forming section 32, and the adhesive film 20 is attached in the film attachment section 33.

Then, the substrate intermediate roll in which the substrate intermediate 10i is wound into a roll is removed from the vacuum deposition device 4 (removed under atmospheric pressure).

In the second vacuum film-forming process, the substrate intermediate product 10i is set in the vacuum film-forming device 4 as the product to be film-formed D1. Then, the substrate intermediate product 10i is unwound, the second metal thin film layer 12B is formed, and the metal-clad substrate 10 (film-formed product D2) is wound up in that order. Here, the second metal thin film layer 12B is formed in the first film-forming section 32. That is, the film-formed surface is reversed between the first and second vacuum film-forming processes. Also, the film attachment section 33 is stopped, and the adhesive film 20 is not attached.

In the first vacuum deposition process, an adhesive film 20 is attached to the surface of the first metal thin film layer 12A. In the subsequent second vacuum deposition process, the first metal thin film layer 12A does not come into direct contact with the roll during deposition of the second metal thin film layer 12B. This prevents pinholes from occurring due to contact between the first metal thin film layer 12A and the roll.

In this way, using the vacuum deposition apparatus 4 with a single-sided deposition method, it is possible to deposit metal thin film layers 12A and 12B on both sides of the base film 11 while suppressing the occurrence of pinholes in the first metal thin film layer 12A.

The adhesive film 20 may be applied between the deposition of the first metal thin film layer 12A and the winding of the substrate intermediate product 10i. However, from the viewpoint of reducing the chance of contact between the first metal thin film layer 12A and the roll, it is preferable to apply the adhesive film 20 immediately after the deposition of the first metal thin film layer 12A. Therefore, as shown in FIG. 3, it is preferable to position the film attachment unit 33 immediately after the first deposition unit 32.

However, as shown in FIG. 4, the vacuum film-forming device 4 may be configured to apply the adhesive film 20 immediately before winding the substrate intermediate product 10i. The temperature of the film-formed product D2 is lower during winding than immediately after film formation, and dimensional changes due to heat are small. Therefore, if the adhesive film 20 is applied immediately before winding the substrate intermediate product 10i, the stress generated in the adhesive film 20 after winding is kept low, which leads to suppression of effects on the tightness of the winding and the winding shape, as well as rubbing due to the difference in thermal expansion between the base film 11 and the adhesive film 20.

Next, an embodiment will be described.
Example 1
A polyimide film (Kapton 150ENA, manufactured by Toray DuPont) with a thickness of 38 μm was prepared as the base film. The base film was set in a magnetron sputtering device with a double-sided film formation method. In the magnetron sputtering device, the formation of a first metal thin film layer, the attachment of an adhesive film, and the formation of a second metal thin film layer were performed continuously in this order to obtain a metal-clad substrate. Here, the composition of the first and second metal thin film layers was copper, and each had a thickness of 100 nm. In addition, a self-adhesive film (Taiko FSA, grade 010C, manufactured by Futamura Chemical) was used as the adhesive film.

A small piece was taken from the metal-clad substrate taken out into the air, the adhesive film was peeled off, and the conductor layer (second metal thin film layer) on the second surface was removed with an etching solution. A halogen lamp (illuminance 4,500 cd, the same applies below) was irradiated from the base film side exposed after the conductor layer was removed, and the number of transmitted lights was counted as the number of pinholes. The number of pinholes with a diameter of 5 μm or more confirmed in the small piece (area 10 cm ² ) was 4.

Example 2
A polyimide film (Apical NPI, manufactured by Kaneka) having a thickness of 25 μm was used as the base film. Other than that, the treatment was carried out under the same conditions as in Example 1. As a result, the number of pinholes having a diameter of 5 μm or more confirmed in the small piece (area 10 cm ² ) was 6.

Example 3
A polyimide film (Upilex S, manufactured by Ube Industries) having a thickness of 25 μm was used as the base film. Other than that, the treatment was carried out under the same conditions as in Example 1. As a result, the number of pinholes having a diameter of 5 μm or more confirmed in the small piece (area 10 cm ² ) was two.

Example 4
A metal thin film layer was formed on both sides of the base film under the same conditions as in Example 1 to obtain a metal-clad substrate. Then, the adhesive film was peeled off from the metal-clad substrate, and a plating film was formed on both sides of the metal-clad substrate by electrolytic plating. Here, the plating film had a composition of copper and a thickness of 2 μm.

A small piece was taken from the metal-clad substrate with the thickened conductor layer, and the conductor layer on the second surface (the second metal thin film layer and the plating film) was removed with an etching solution. A halogen lamp was irradiated from the base film side exposed after the conductor layer was removed, and the number of transmitted lights was counted as the number of pinholes. The number of pinholes with a diameter of 5 μm or more confirmed in the small piece (area 10 cm ² ) was 6.

Example 5
A polyimide film (Kapton 150ENA, manufactured by Toray DuPont) with a thickness of 38 μm was prepared as the base film. The base film was set in a magnetron sputtering device with a single-sided film formation method. In the magnetron sputtering device, the first metal thin film layer was formed and the adhesive film was attached in this order to obtain a substrate intermediate. Here, the composition of the first metal thin film layer was copper, and the thickness was 100 nm. In addition, a self-adhesive film (Taiko FSA, grade 010C, manufactured by Futamura Chemical) was used as the adhesive film.

The resulting intermediate substrate was removed from the magnetron sputtering device and set back into the magnetron sputtering device as the substrate on which the film was to be formed. A second metal thin film layer was formed using the magnetron sputtering device. Here, the composition of the second metal thin film layer was copper, and the thickness was 100 nm.

A small piece was taken from the metal-clad substrate taken out into the air, the adhesive film was peeled off, and the conductor layer (second metal thin film layer) on the second surface was removed with an etching solution. A halogen lamp was irradiated from the base film side exposed after the conductor layer was removed, and the number of transmitted lights was counted as the number of pinholes. The number of pinholes with a diameter of 5 μm or more confirmed in the small piece (area 10 cm ² ) was 4.

Example 6
A metal thin film layer was formed on both sides of the base film under the same conditions as in Example 5 to obtain a metal-clad substrate. The adhesive film was then peeled off from the metal-clad substrate, and a plating film was formed on both sides of the metal-clad substrate by electrolytic plating. Here, the plating film had a composition of copper and a thickness of 2 μm.

A small piece was taken from the metal-clad substrate with the thickened conductor layer, and the conductor layer on the second surface (the second metal thin film layer and the plating film) was removed with an etching solution. A halogen lamp was irradiated from the base film side exposed after the conductor layer was removed, and the number of transmitted lights was counted as the number of pinholes. The number of pinholes with a diameter of 5 μm or more confirmed in the small piece (area 10 cm ² ) was 6.

(Comparative Example 1)
A metal-clad substrate was obtained under the same conditions as in Example 1. However, no adhesive film was attached. The number of pinholes was counted using the same procedure as in Example 1, and the number of pinholes with a diameter of 5 μm or more confirmed in the small piece (area 10 cm ² ) was 50.

(Comparative Example 2)
A metal-clad substrate was obtained under the same conditions as in Example 2, except that no adhesive film was attached. The number of pinholes was counted using the same procedure as in Example 2, and the number of pinholes with a diameter of 5 μm or more found in the small piece (area 10 cm ² ) was 150.

(Comparative Example 3)
A metal-clad substrate was obtained under the same conditions as in Example 3. However, no adhesive film was attached. The number of pinholes was counted using the same procedure as in Example 3, and the number of pinholes with a diameter of 5 μm or more confirmed in the small piece (area 10 cm ² ) was 25.

(Comparative Example 4)
A metal-clad substrate was obtained under the same conditions as in Example 4, except that no adhesive film was attached. The number of pinholes was counted using the same procedure as in Example 4, and the number of pinholes with a diameter of 5 μm or more confirmed in the small piece (area 10 cm ² ) was 80.

(Comparative Example 5)
A metal-clad substrate was obtained under the same conditions as in Example 5. However, no adhesive film was attached. The number of pinholes was counted using the same procedure as in Example 5, and the number of pinholes with a diameter of 5 μm or more confirmed in the small piece (area 10 cm ² ) was 50.

(Comparative Example 6)
A metal-clad substrate was obtained under the same conditions as in Example 6, except that no adhesive film was attached. The number of pinholes was counted using the same procedure as in Example 6, and the number of pinholes with a diameter of 5 μm or more found in the small piece (area 10 cm ² ) was 70.

The conditions and the number of pinholes in Examples 1 to 6 and Comparative Examples 1 to 6 are summarized in Table 1.

As is clear from Table 1, in Examples 1 to 6 in which an adhesive film was applied, the number of pinholes was 6 or less. In contrast, in Comparative Examples 1 to 6 in which an adhesive film was not applied, the number of pinholes was 25 or more. This confirmed that the application of an adhesive film can suppress the occurrence of pinholes. It was also confirmed that the application of an adhesive film can suppress the occurrence of pinholes, regardless of the thickness of the base film, the type of magnetron sputtering device (double-sided/single-sided), or whether electrolytic plating is performed or not.

REFERENCE SIGNS LIST 11 Base film 10i Substrate intermediate product 10 Metal-clad substrate 12A First metal thin film layer 12B Second metal thin film layer 13 Plated film 20 Adhesive film 3 Vacuum film-forming device 30 Vacuum chamber 31 Unwinding section 32 First film-forming section 33 Film attachment section 34 Second film-forming section 35 Winding section

Claims (3)

a first vacuum film-forming process in which a first metal thin film layer is formed on a first surface of the base film by a vacuum film-forming method while transporting the base film by a roll-to-roll method, and an adhesive film is attached to the surface of the first metal thin film layer to obtain a substrate intermediate product;
a second vacuum deposition process in which a second metal thin film layer is deposited on a second surface of the base film by a vacuum deposition method while the intermediate substrate is transported by a roll-to-roll method to obtain a metal-clad substrate;
and an electrolytic plating process in which the adhesive film is peeled off while the metal-clad substrate is transported by a roll-to-roll method, and a plating film is formed on both sides of the metal-clad substrate by electrolytic plating .
After the adhesive film is peeled off, and before the plating film is formed, organic matter remaining on the surface of the first metal thin film layer is removed by atmospheric pressure plasma;
The adhesive film is a self-adhesive film having an adhesive layer made of an adhesive resin.
A method for producing a metal-clad substrate comprising the steps of: 2. The method for manufacturing a metal-clad substrate according to claim 1, wherein the first vacuum film-forming step and the second vacuum film-forming step are performed consecutively in a single vacuum film-forming apparatus. In the first vacuum film-forming step, the base film is unwound and the intermediate substrate is wound up;
2. The method for manufacturing a metal-clad substrate according to claim 1, wherein the second vacuum film-forming step includes unwinding the intermediate substrate and winding up the metal-clad substrate.