JP7583451B2 - Conductive film for circuit boards, and method for producing conductive film for circuit boards - Google Patents

Description

The present invention relates to a conductive film for circuit boards and a method for producing the conductive film for circuit boards. More specifically, the present invention relates to a conductive film for circuit boards and a method for producing the conductive film for circuit boards, which has a thin copper layer that is not easily oxidized, can prevent an increase in the resistance value of the thin copper layer until electrolytic plating is performed, and can easily remove an anticorrosive layer with acid during the production of the conductive film for circuit boards.

Laminated substrates have been used in various fields in the past. Patent Document 1 discloses a laminated substrate for a metal mesh touch panel.

JP 2017-64939 A

However, in the laminate substrate described in Patent Document 1, the metal is visually recognized as a mesh due to reflection from the conductive pattern. Therefore, it is necessary to sufficiently reduce the reflectance of the low-reflectance alloy layer on the outermost surface side, and the thickness of the low-reflectance alloy layer needs to be 10 nm or more.

Incidentally, when a conventional laminate substrate as described in Patent Document 1 is used for a circuit board (for example, FCCL, Flexible Copper Clad Laminate), the outermost low-reflectivity alloy layer must be removed by etching with acid before providing a plated copper layer in the copper plating process (electrolytic plating process). However, the laminate substrate described in Patent Document 1 has a large low-reflectivity alloy layer, which is difficult to sufficiently remove by etching with acid. As a result, in the laminate substrate described in Patent Document 1, the plated copper layer is formed while the low-reflectivity alloy layer remains, so that the plated copper layer may not be deposited well or may be easily peeled off.

The present invention has been made in consideration of such conventional inventions, and aims to provide a conductive film for circuit boards and a method for manufacturing a conductive film for circuit boards in which the thin-film copper layer is not easily oxidized, the anti-rust layer can be easily removed with acid during the manufacture of the conductive film for circuit boards, and an increase in the resistance value of the thin-film copper layer can be prevented until electrolytic plating is performed.

After extensive research, the inventors discovered that by providing an anticorrosive layer containing a copper-nickel alloy in a specified ratio and with an adjusted thickness on a thin-film copper layer, oxidation of the thin-film copper layer can be prevented, an increase in the resistance value of the thin-film copper layer can be prevented until electrolytic plating is performed, and such an anticorrosive layer can be easily removed with acid during the manufacture of a conductive film for circuit boards, and thus completed the present invention. In other words, the conductive film for circuit boards and the method for manufacturing a conductive film for circuit boards of the present invention, which solve the above problems, mainly include the following configurations.

(1) A conductive film for circuit boards comprising a substrate and a laminate provided on at least one surface of the substrate, the laminate having, from the substrate side, a thin-film copper layer and an anticorrosive layer in this order, the anticorrosive layer containing an alloy of copper and nickel, the proportion of copper in the alloy of copper and nickel being 35 to 70 mass %, and the average thickness of the anticorrosive layer being 1 to 9 nm.

With this configuration, the conductive film for circuit boards has an anticorrosive layer that prevents oxidation of the thin-film copper layer, and prevents an increase in the resistance value of the thin-film copper layer until electrolytic plating is performed. In addition, the conductive film for circuit boards has an anticorrosive layer that can be easily removed with acid during manufacturing.

(2) The conductive film for circuit boards described in (1), in which an intermediate layer is provided between the substrate and the thin-film copper layer.

With this configuration, the conductive film for circuit boards has better adhesion between the substrate and the thin-film copper layer.

(3) The conductive film for circuit boards according to (2), wherein the intermediate layer contains an alloy of copper and nickel.

With this configuration, the conductive film for circuit boards has better adhesion between the substrate and the thin-film copper layer when used, for example, as a film for sputtered FCCL.

(4) The conductive film for circuit boards according to (2), wherein the intermediate layer contains at least one of melamine resin, fluororesin, urethane resin, silicone compound, acrylic resin, polyethylene wax, or microcrystalline wax.

With this configuration, when the conductive film for circuit boards is used as, for example, a thin copper layer transfer film, the substrate is easily peeled off after transfer.

(5) A conductive film for circuit boards according to any one of (1) to (4), in which, when heat-treated in an atmosphere at 250°C for 2.5 hours, the electrical resistance value in a region spaced 10 cm apart on the outermost surface opposite the substrate is 30 Ω or less.

With this configuration, the conductive film for circuit boards prevents an increase in the resistance value of the thin-film copper layer.

(6) A conductive film for circuit boards according to any one of (1) to (5), in which the electrical resistance of the outermost surface on the side opposite the substrate in a region spaced 10 cm apart is 4.0 Ω or less when subjected to a heating and humidifying treatment for 500 hours in an atmosphere of 85°C and 85% RH (relative humidity).

With this configuration, the conductive film for circuit boards prevents an increase in the resistance value of the thin-film copper layer.

(7) A method for producing a conductive film for circuit boards, comprising the steps of: preparing a substrate; forming a laminate having, on at least one surface side of the substrate, an intermediate layer, a thin-film copper layer, and an anti-rust layer in this order from the substrate side; removing the anti-rust layer after forming the laminate; and forming a plated copper layer on the thin-film copper layer by an electrolytic plating method after removing the anti-rust layer, wherein the anti-rust layer contains an alloy of copper and nickel, the intermediate layer contains an alloy of copper and nickel, the proportion of copper in the alloy of copper and nickel in the anti-rust layer is 35 to 70 mass %, and the average thickness of the anti-rust layer is 1 to 9 nm.

With this configuration, the conductive film for circuit boards has an anti-rust layer that prevents oxidation of the thin-film copper layer, and prevents an increase in the resistance value of the thin-film copper layer until electrolytic plating is performed. In addition, the anti-rust layer of the conductive film for circuit boards is easily removed by the acid in the pickling process before electrolytic plating.

(8) A method for producing a conductive film for circuit boards, comprising the steps of: preparing a substrate; forming a laminate having, on at least one surface side of the substrate, an intermediate layer, a thin-film copper layer, and an anti-rust layer in this order from the substrate side; removing the anti-rust layer after forming the laminate; and forming a plated copper layer on the thin-film copper layer by electrolytic plating after removing the anti-rust layer, wherein the anti-rust layer contains an alloy of copper and nickel, the intermediate layer contains at least one of melamine resin, fluororesin, urethane resin, silicone compound, acrylic resin, polyethylene wax, and microcrystalline wax, the proportion of copper in the alloy of copper and nickel is 35 to 70 mass %, and the average thickness of the anti-rust layer is 1 to 9 nm.

With this configuration, the conductive film for circuit boards has an anti-rust layer that prevents oxidation of the thin-film copper layer, and prevents an increase in the resistance value of the thin-film copper layer until electrolytic plating is performed. In addition, the anti-rust layer of the conductive film for circuit boards is easily removed by the acid in the pickling process before electrolytic plating.

The present invention provides a conductive film for circuit boards and a method for producing a conductive film for circuit boards, in which the thin-film copper layer is not easily oxidized, and the resistance value of the thin-film copper layer can be prevented from increasing until electrolytic plating is performed, and the rust-preventive layer can be easily removed with acid during the production of the conductive film for circuit boards.

FIG. 1 is a schematic cross-sectional view of a film according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a film according to one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing a state in which the anticorrosive layer has been removed in the film manufacturing method of one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing a state in which a plated copper layer has been formed in a film manufacturing method according to one embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a state in which the anticorrosive layer has been removed in the film manufacturing method of one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing a state in which a plated copper layer has been formed in a film manufacturing method according to one embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing a state in which the obtained film is transferred to a transfer substrate via an adhesive layer in a film manufacturing method according to one embodiment of the present invention, and then the substrate and intermediate layer are peeled off.

<Conductive film for circuit boards>
A conductive film for circuit boards (hereinafter also simply referred to as a film) according to one embodiment of the present invention includes a substrate and a laminate provided on at least one surface of the substrate. The laminate has, from the substrate side, a thin-film copper layer and an anticorrosive layer, in this order. The anticorrosive layer contains an alloy of copper and nickel. The proportion of copper in the copper-nickel alloy is 35 to 70 mass %. The average thickness of the anticorrosive layer is 1 to 9 nm. Each of these will be described below.

(Substrate)
The substrate is not particularly limited. For example, the substrate may be PI (polyimide), PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PMMA (methacrylic resin), PP (polypropylene), PE (polyethylene), COP (cycloolefin polymer resin), PPS (polyphenylene sulfide resin), PS (polystyrene resin), fluororesin (e.g., PTFE, PFA, ETFE, FEP), PEEK (polyether ether ketone resin), etc. By using these substrates, the film of the present embodiment is easy to handle and easy to increase productivity.

The thickness of the substrate is not particularly limited. For example, the thickness of the substrate is preferably 6 μm or more, more preferably 12 μm or more, and even more preferably 25 μm or more. The thickness of the substrate is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 200 μm or less. When the thickness of the substrate is within the above range, the film has excellent handling properties and flexibility during processing. Furthermore, the film is easily suitable for use as a bendable circuit board. The average thickness of the substrate can be appropriately adjusted depending on the use of the film. For example, in applications requiring a thinner film and high flexibility, the average thickness of the substrate can be selected to be close to 6 μm. Furthermore, the average thickness of the substrate can be selected to be close to 300 μm in terms of insulation, high reliability, and handleability.

(Middle class)
The intermediate layer is a layer that is suitably provided between the substrate and the thin-film copper layer. In addition, the material of the intermediate layer can be appropriately selected depending on the application of the film (for example, a film for sputtered FCCL or a thin-film copper layer transfer film, etc.). Hereinafter, as an example, a case where the film of this embodiment is a film for sputtered FCCL or a thin-film copper layer transfer film will be described.

- Film for sputtered FCCL Fig. 1 is a schematic cross-sectional view of the film 1a of this embodiment. When the film 1a of this embodiment is a film for sputtered FCCL, the intermediate layer 3a is provided as an adhesion layer for improving adhesion between the substrate 2 and the thin-film copper layer 4. Reference numeral 5 denotes an anticorrosive layer.

The intermediate layer 3a preferably contains an alloy of copper and nickel. This provides the film 1a with better adhesion between the substrate 2 and the thin-film copper layer 4.

In the copper-nickel alloy, the copper content is preferably 32% by mass or more, more preferably 35% by mass or more, based on the total amount of copper and nickel in the intermediate layer 3a. In addition, in the copper-nickel alloy, the copper content is preferably 70% by mass or less, more preferably 56% by mass or less, even more preferably 45% by mass or less, and particularly preferably 40% by mass or less, based on the total amount of copper and nickel in the intermediate layer 3a. By having the copper content within the above range, the alloy is no longer a ferromagnetic material at room temperature, and the magnetic permeability can be reduced. This makes it easier to form the alloy into a film by sputtering. In addition, the intermediate layer 3a is likely to have improved adhesion at the interface with the substrate 2, making it easy to obtain excellent adhesion.

On the other hand, in the alloy of copper and nickel, the nickel content is preferably 30 mass% or more, more preferably 44 mass% or more, even more preferably 55 mass% or more, and particularly preferably 60 mass% or more, based on the total amount of copper and nickel in the intermediate layer 3a. Also, in the alloy of copper and nickel, the nickel content is preferably 68 mass% or less, based on the total amount of copper and nickel in the intermediate layer 3a.

The content of the copper-nickel alloy is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, based on the total amount of the intermediate layer 3a. The intermediate layer 3a may contain other components as appropriate depending on the purpose, as long as the effect of this embodiment is achieved.

The thickness of the intermediate layer 3a is not particularly limited. As an example, the thickness of the intermediate layer 3a is preferably 3 nm or more, more preferably 4 nm or more, and even more preferably 5 nm or more. The thickness of the intermediate layer 3a is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 25 nm or less. When the thickness of the intermediate layer 3a is within the above range, the film 1a has excellent adhesion and excellent productivity.

In the case of a thin copper layer transfer film, Fig. 2 is a schematic cross-sectional view of the film 1b of this embodiment. When the film 1b of this embodiment is a thin copper layer transfer film, the intermediate layer 3b is provided as a release layer when peeling off the substrate 2 after transfer. Reference numeral 5 denotes an anticorrosive layer.

It is preferable that the intermediate layer 3b contains at least one of melamine resin, fluororesin, urethane resin, silicone compound, acrylic resin, polyethylene wax, and microcrystalline wax. This makes it easier to peel the film 1b from the substrate 2 after transfer.

In addition, in this embodiment, when the film 1b is a thin copper layer transfer film and the substrate 2 is a fluororesin or olefin resin, the intermediate layer 3b may be omitted.

The thickness of the intermediate layer 3b is not particularly limited. As an example, the thickness of the intermediate layer 3b is preferably 10 nm or more, more preferably 50 nm or more, and even more preferably 100 nm or more. The thickness of the intermediate layer 3b is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less. When the thickness of the intermediate layer 3b is within the above range, the film 1b has excellent peelability and excellent productivity.

(Laminate)
The laminate is provided on at least one surface of a substrate, and includes, from the substrate side, a thin-film copper layer and an anticorrosive layer in this order.

Thin-film copper layer The thin-film copper layer is provided as a base for forming electrodes on a circuit board. Copper is inexpensive compared to other metals used in circuit boards and has a low resistivity, making it suitable as a metal type for forming a conductive pattern for a circuit board. In addition, by providing the thin-film copper layer, copper is easily deposited when a plated copper layer is subsequently formed. The thin-film copper layer, together with the above-mentioned intermediate layer, is etched into a desired pattern by a photolithography process when it is made into an FPC (Flexible Printed Circuit).

The method for forming the thin-film copper layer is not particularly limited. For example, the thin-film copper layer can be formed by a conventionally known physical vapor deposition method such as a vacuum deposition method, a sputtering method, or an ion plating method. Among these, it is preferable to form the thin-film copper layer of the film of this embodiment by a sputtering method because the film quality after deposition is excellent. Conventionally known sputtering conditions can be appropriately adopted based on the desired thickness of the thin-film copper layer.

The thickness of the thin-film copper layer is not particularly limited. As an example, the thickness of the thin-film copper layer is preferably 50 nm or more, more preferably 60 nm or more, and even more preferably 70 nm or more. When the thickness of the thin-film copper layer is within the above range, the film is easily thickened by copper electrolytic plating. In addition, the thickness of the thin-film copper layer is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less. When the thickness of the thin-film copper layer is within the above range, the film has excellent productivity.

Anti-rust layer The anti-rust layer is provided on the thin copper layer. The anti-rust layer is preferentially oxidized (corroded) by oxygen in the air. This prevents the oxidation of the thin copper layer.

The anticorrosive layer includes an alloy of copper and nickel. The copper content of the copper-nickel alloy may be 32% by mass or more, preferably 35% by mass or more, based on the total amount of copper and nickel in the anticorrosive layer. The copper content of the copper-nickel alloy may be 70% by mass or less, preferably 55% by mass or less, more preferably 45% by mass or less, based on the total amount of copper and nickel in the anticorrosive layer. If the copper content is less than 32% by mass based on the total amount of copper and nickel in the anticorrosive layer, the alloy becomes ferromagnetic at room temperature and the magnetic permeability cannot be reduced, making it difficult to form a film by sputtering. On the other hand, if the copper content exceeds 70% by mass based on the total amount of copper and nickel in the anticorrosive layer, the film has a problem that the oxidation prevention performance of the anticorrosive layer is reduced and the resistance value of the thin film copper layer is easily increased.

On the other hand, the nickel content of the copper-nickel alloy may be 30% by mass or more, preferably 45% by mass or more, and more preferably 55% by mass or more, based on the total amount of copper and nickel in the anticorrosive layer. By having the nickel content within the above range, the anti-oxidation performance of the anticorrosive layer is more excellent, and the increase in the resistance value of the thin film copper layer is suppressed. Furthermore, the nickel content of the copper-nickel alloy may be 68% by mass or less, preferably 65% by mass or less, based on the total amount of copper and nickel in the anticorrosive layer. By having the nickel content within the above range, the copper-nickel alloy becomes non-magnetic at room temperature, making it easier to form the anticorrosive layer by sputtering.

The content of the copper-nickel alloy is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, based on the total amount of the anticorrosive layer. The anticorrosive layer may contain other components as appropriate depending on the purpose, as long as the effect of this embodiment is achieved.

The method for forming the anti-rust layer is not particularly limited. For example, the anti-rust layer can be formed by a conventional physical vapor deposition method such as sputtering.

The thickness (average thickness) of the anti-rust layer may be 1 nm or more, preferably 3 nm or more, and more preferably 5 nm or more. The thickness of the anti-rust layer may be 9 nm or less, and more preferably 7 nm or less. If the thickness of the anti-rust layer is less than 1 nm, the film is less likely to prevent oxidation of the thin copper layer. On the other hand, if the thickness of the anti-rust layer is more than 9 nm, the film is less likely to have the anti-rust layer removed by acid, and if electrolytic plating is performed on it, the plated copper layer is less likely to deposit or is more likely to peel off.

In this embodiment, the anticorrosive layer has fine irregularities. Therefore, the thickness of the anticorrosive layer is an average thickness. In this embodiment, the average thickness of the anticorrosive layer can be measured using an X-ray fluorescence measurement device. Specifically, first, a substrate on which an anticorrosive layer of a predetermined thickness is formed is prepared, and the physical film thickness of the anticorrosive layer of the predetermined thickness is measured using a contact step gauge. In addition, the amount of the anticorrosive layer in the anticorrosive layer of the predetermined thickness is measured by quantitative analysis using an X-ray fluorescence measurement device (XRF, Primini (tabletop wavelength dispersive X-ray fluorescence analyzer), manufactured by Rigaku Corporation). A calibration curve is created from the film thickness measured by the contact step gauge and the amount of the anticorrosive layer material measured by quantitative analysis using XRF. Nickel and copper derived from the anticorrosive layer are detected by quantitative analysis using XRF on the film, and the average value of the measured values at 10 points is taken as the average thickness. The average thickness of the anticorrosive layer can be considered to be the average value in the fine irregularity profile.

Returning to the description of the laminate as a whole, the laminate is provided on at least one side of the substrate. The laminate may also be provided on both sides of the substrate.

As described above, the film of this embodiment has an anti-rust layer that prevents oxidation of the thin-film copper layer and prevents an increase in the resistance value of the thin-film copper layer until electrolytic plating is performed, and the anti-rust layer can be easily removed with acid during production of the film.

Specifically, when the film of this embodiment is subjected to a heat treatment in an atmosphere of 250°C for 2.5 hours, the electrical resistance value in a region spaced 10 cm apart on the outermost surface opposite the substrate is preferably 30 Ω or less, and more preferably 10 Ω or less. In this way, the film of this embodiment can prevent an increase in the resistance value of the thin-film copper layer.

In addition, when the film of this embodiment is subjected to a heating and humidifying treatment for 500 hours in an atmosphere of 85°C and 85% RH (relative humidity), it is preferable that the electrical resistance value of the outermost surface on the surface opposite the substrate in an area spaced 10 cm apart is 4.0 Ω or less. In this way, the film of this embodiment can prevent an increase in the resistance value of the thin-film copper layer.

The anti-rust layer is very thin compared to the thin-film copper layer. Therefore, the electrical resistance of the outermost surface represents the resistance between the anti-rust layer and the thin-film copper layer, and can essentially be considered as the electrical resistance of the thin-film copper layer. Therefore, an electrical resistance of the outermost surface of 30 Ω or less means that the electrical resistance of the thin-film copper layer is about that value, and it can be said that oxidation of the thin-film copper layer is suppressed.

<Method of manufacturing conductive film for circuit boards>
Below, a method for producing a conductive film for circuit boards according to one embodiment of the present invention (hereinafter also referred to as a film producing method) will be described for the cases where the film is used as a film for sputtered FCCL and where the film is used as a thin film copper layer transfer film.

(For sputtered FCCL film)
When the film is used as a film for sputtered FCCL, the method for producing the film of this embodiment includes the steps of preparing a substrate, forming a laminate having an intermediate layer, a thin-film copper layer, and an anti-rust layer in this order from the substrate side on at least one surface side of the substrate, removing the anti-rust layer after forming the laminate, and forming a plated copper layer on the thin-film copper layer by electrolytic plating after removing the anti-rust layer. The anti-rust layer contains an alloy of copper and nickel. The intermediate layer contains an alloy of copper and nickel. The proportion of copper in the alloy of copper and nickel in the anti-rust layer is 35 to 70 mass %. The average thickness of the anti-rust layer is 1 to 9 nm. Each of these will be described below. In the following description, the substrate, intermediate layer, and laminate are the same as those described above in the embodiment of the film.

Step of Preparing Substrate and Step of Forming Laminate A laminate having an intermediate layer, a thin-film copper layer, and an anti-rust layer in this order from the substrate side is formed on at least one surface side of the prepared substrate.

There is no particular limitation on the method for laminating the intermediate layer onto the substrate. As an example, the intermediate layer can be laminated by sputtering or the like.

The method for forming the thin-film copper layer in the intermediate layer is not particularly limited. As an example, the thin-film copper layer can be formed by a conventionally known physical vapor deposition method such as a vacuum deposition method, a sputtering method, or an ion plating method, as described above in the embodiment of the film.

There is no particular limitation on the method for forming the anti-rust layer on the thin-film copper layer. As an example, the anti-rust layer can be formed by a conventional physical vapor deposition method such as sputtering, as described above in the embodiment of the film.

- Step of removing the anticorrosive layer The method of removing the anticorrosive layer is not particularly limited. For example, the anticorrosive layer can be removed by washing with an acid such as dilute sulfuric acid, hydrogen peroxide, or ferric chloride. In the film of this embodiment, the thickness of the anticorrosive layer is 1 to 9 nm. Therefore, the anticorrosive layer is easily removed sufficiently and is unlikely to remain on the thin-film copper layer. Figure 3 is a schematic cross-sectional view showing a state in which the anticorrosive layer 5 (see Figure 1) has been removed in the film manufacturing method of this embodiment.

Before cleaning with acid, the laminate may be heat-treated. Even in such a case, the film 1a of this embodiment has an anti-rust layer, which can prevent the thin-film copper layer 4 from being oxidized.

- Step of forming a plated copper layer After the anticorrosive layer is removed, a plated copper layer is formed on the exposed thin-film copper layer 4 by electrolytic plating. The conditions for the electrolytic plating are not particularly limited. For example, the electrolytic plating can be performed by immersing a film in a copper sulfate bath and an electrode in the copper sulfate bath or the like, applying a voltage between the film and the electrode, and causing a reduction reaction of copper ions in the copper sulfate bath on the thin-film copper layer of the film.

Figure 4 is a schematic cross-sectional view showing the state in which the plated copper layer 6 has been formed in the film manufacturing method of this embodiment.

The electrolytic plating method for forming the plated copper layer 6 on the thin-film copper layer 4 is not particularly limited. As an example, the electrolytic plating method may employ conditions in which a copper sulfate bath, a copper cyanide bath, a copper pyrophosphate bath, or the like is used as the electrolyte bath.

The thickness of the plated copper layer 6 is not particularly limited. As an example, the thickness of the plated copper layer 6 is preferably 1 μm or more, and more preferably 2 μm or more. The thickness of the plated copper layer 6 is preferably 50 μm or less, and more preferably 30 μm or less. By having the thickness of the plated copper layer 6 within the above range, the film has the advantage of being able to achieve both low resistance and productivity.

By carrying out the above steps, a film is produced in which the substrate, intermediate layer, thin-film copper layer, and plated copper layer are laminated in this order. In the obtained film, the thin-film copper layer is covered with an anti-rust layer during the manufacturing process. This prevents oxidation of the thin-film copper layer even when the film is heated before electrolytic plating is performed. Therefore, an increase in the resistance value of the thin-film copper layer is prevented until electrolytic plating is performed. In addition, the anti-rust layer is sufficiently removed before the plated copper layer is formed, and the surface of the thin-film copper layer is cleaned. In addition, the plated copper layer is formed on the thin-film copper layer. In this case, since the plated copper layer is formed on the thin-film copper layer made of copper, which is the same metal type, it is easy to accumulate.

(In the case of thin copper layer transfer film)
When the application of the film is a thin-film copper layer transfer film, the manufacturing method of the film of this embodiment includes the steps of preparing a substrate, forming a laminate having an intermediate layer, a thin-film copper layer, and an anti-rust layer in this order from the substrate side on at least one side of the substrate, removing the anti-rust layer after forming the laminate, and forming a plated copper layer on the thin-film copper layer by electrolytic plating after removing the anti-rust layer. The anti-rust layer includes an alloy of copper and nickel. The intermediate layer includes at least one of melamine resin, fluororesin, urethane resin, silicone compound, acrylic resin, polyethylene wax, and microcrystalline wax. The proportion of copper in the alloy of copper and nickel is 35 to 70 mass%. The average thickness of the anti-rust layer is 1 to 9 nm. Each of these will be described below. In the following description, the substrate, intermediate layer, and laminate are the same as those described above in the embodiment of the film.

Step of Preparing Substrate and Step of Forming Laminate A laminate having an intermediate layer, a thin-film copper layer, and an anti-rust layer in this order from the substrate side is formed on at least one surface side of the prepared substrate.

There is no particular limitation on the method for laminating the intermediate layer onto the substrate. As an example, the intermediate layer may be laminated by sputtering.

The method for forming the thin-film copper layer in the intermediate layer is not particularly limited. As an example, the thin-film copper layer can be formed by a conventionally known physical vapor deposition method such as a vacuum deposition method, a sputtering method, or an ion plating method, as described above in the embodiment of the film.

There is no particular limitation on the method for forming the anti-rust layer on the thin-film copper layer. As an example, the anti-rust layer can be formed by a conventional physical vapor deposition method such as sputtering, as described above in the embodiment of the film.

The method for removing the anticorrosive layer is not particularly limited. For example, the anticorrosive layer may be removed by the method described above in the case of a film for sputtered FCCL. Fig. 5 is a schematic cross-sectional view showing a state in which the anticorrosive layer 5 (see Fig. 2) has been removed in the film manufacturing method of this embodiment.

The method for forming the plated copper layer is not particularly limited. For example, the plated copper layer may be formed by the method described above in the case of the film for sputtered FCCL.

Figure 6 is a schematic cross-sectional view showing the state in which the plated copper layer 6 has been formed in the film manufacturing method of this embodiment.

The electrolytic plating method for forming the plated copper layer 6 on the thin-film copper layer 4 is not particularly limited. As an example, the electrolytic plating method may employ conditions in which a copper sulfate bath, a copper cyanide bath, a copper pyrophosphate bath, or the like is used as the electrolyte bath.

The thickness of the plated copper layer 6 is not particularly limited. As an example, the thickness of the plated copper layer 6 is preferably 1 μm or more, and more preferably 2 μm or more. The thickness of the plated copper layer 6 is preferably 50 μm or less, and more preferably 30 μm or less. By having the thickness of the plated copper layer 6 within the above range, the film has the advantage of being able to achieve both low resistance and productivity.

By carrying out the above steps, a film is produced in which the substrate, intermediate layer, thin-film copper layer, and plated copper layer are laminated in this order. In the obtained film, the thin-film copper layer is covered with the anti-rust layer during the manufacturing process. As a result, even if the film is heated before electrolytic plating, oxidation of the thin-film copper layer is prevented. Therefore, an increase in the resistance value of the thin-film copper layer is prevented until electrolytic plating is performed. In addition, the anti-rust layer is sufficiently removed before the plated copper layer is formed, and the surface of the thin-film copper layer is cleaned. In addition, the plated copper layer is formed on the thin-film copper layer. At this time, since the plated copper layer is formed on the thin-film copper layer made of copper, which is the same metal species, it is easy to accumulate. The obtained film is transferred to the transfer substrate via the adhesive layer, and then the intermediate layer and the substrate are peeled off. FIG. 7 is a schematic cross-sectional view showing a state in which the obtained film is transferred to the transfer substrate 8 via the adhesive layer 7, and then the substrate 2 and the intermediate layer 3b are peeled off in the film manufacturing method of this embodiment.

The adhesive layer 7 is not particularly limited. For example, the adhesive layer 7 is made of a resin such as an acrylic resin, a urethane resin, a urethane-modified polyester resin, a polyester resin, an epoxy resin, an ethylene-vinyl acetate copolymer resin (EVA), a vinyl resin (vinyl chloride, vinyl acetate, vinyl chloride-vinyl acetate copolymer resin), a styrene-ethylene-butylene copolymer resin, a polyvinyl alcohol resin, a polyacrylamide resin, a bismaleimide resin, a cyanate monomer, an isobutylene rubber, an isoprene rubber, a natural rubber, an SBR, an NBR, a silicone rubber, a PPE, or an olefin. These resins may be dissolved in a solvent or used without a solvent, as appropriate.

The thickness of the adhesive layer 7 is not particularly limited. As an example, the thickness of the adhesive layer 7 is about 0.5 to 5 μm.

The method for forming the adhesive layer 7 is not particularly limited. As an example, the adhesive layer 7 can be formed by applying a resin solution that constitutes the adhesive layer 7 dissolved in an appropriate solvent onto the plated copper layer 6 using a roll coater or the like, and then drying the solution.

The substrate 8 is not particularly limited. For example, the substrate 8 may be a glass substrate, an epoxy substrate, a metal substrate, a ceramic substrate, a silicon substrate, a semiconductor sealing resin substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, a thermosetting polyphenylene ether substrate, etc.

The present invention will be described in more detail below with reference to examples. The present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass."

Example 1
A substrate (thickness 25 μm) made of PI was prepared. An intermediate layer containing an alloy of copper and nickel was formed on the substrate using a sputtering device so that the film thickness was 10 nm. Next, a thin-film copper layer was formed on the intermediate layer using a sputtering device so that the film thickness was 120 nm. Thereafter, a rust-proof layer was formed on the thin-film copper layer using a sputtering device so that the film thickness was 1 nm, thereby producing a conductive film for circuit boards.

<Examples 2 to 15 and Comparative Examples 1 to 6>
A conductive film for circuit boards was produced in the same manner as in Example 1, except that the type and thickness of each layer were adjusted according to the recipe shown in Table 1. In Table 1, "Ni-35Cu" indicates that a sputtering target of Ni-Cu alloy containing 35 mass% Cu and 65 mass% Ni was used. "Ni-55Cu" indicates that a sputtering target of Ni-Cu alloy containing 55 mass% Cu (copper) and 45 mass% Ni (nickel) was used. "Ni-70Cu" indicates that a sputtering target of Ni-Cu alloy containing 70 mass% Cu (copper) and 30 mass% Ni (nickel) was used. In this case, the composition ratio of the Ni-Cu alloy in the intermediate layer and the anticorrosive layer of the FCCL formed using the Ni-35Cu target was analyzed by XPS, and it was confirmed that there was no substantial difference between the composition ratio of the target and the composition ratio of the film itself formed by sputtering. Therefore, the composition ratio of the film and the composition ratio of the target can be regarded as the same. Similarly, the composition ratio of the Ni-Cu alloy in the anticorrosive layer formed using the Ni-55Cu and Ni-70Cu targets can be regarded as having no substantial difference between the composition ratio of the target and the composition ratio of the film itself formed by sputtering. In Comparative Example 4, no anticorrosive layer was provided.

The films obtained in Examples 1 to 15 and Comparative Examples 1 to 6 were evaluated according to the following methods for "electrical resistance value of the outermost surface in a region spaced 10 cm apart on the surface opposite the substrate when heat treatment was performed for 2.5 hours in an atmosphere of 250°C", "electrical resistance value of the outermost surface in a region spaced 10 cm apart on the surface opposite the substrate when heat and humidification treatment was performed for 500 hours in an atmosphere of 85°C and 85% RH (relative humidity)", and "etchability of the anticorrosive layer". The results are shown in Table 1.

<Electrical resistance value in a region spaced 10 cm apart on the outermost surface opposite to the substrate when heat treatment is performed for 2.5 hours in an atmosphere at 250° C.>
The film was subjected to a heat treatment in an atmosphere of 250° C. for 2.5 hours. Thereafter, the electrical resistance value in a region spaced 10 cm apart on the outermost surface opposite the substrate was measured using a commercially available tester (digital multimeter, Hioki E.E. Corporation, DT4222). Specifically, on the outermost surface opposite the substrate, two terminals of the tester were measured at an interval of about 10 cm. The initial electrical resistance value of the outermost surface was 0.8 to 0.9 Ω for all samples.

<Electrical resistance value of the outermost surface in a region spaced 10 cm apart from the outermost surface opposite the substrate when heat and humidification treatment is performed for 500 hours in an atmosphere of 85° C. and 85% RH (relative humidity)>
The film was subjected to a heating and humidifying treatment for 500 hours in an atmosphere of 85°C and 85% RH (relative humidity). Thereafter, the electrical resistance value in a region spaced 10 cm apart on the outermost surface opposite the substrate was measured using a commercially available tester (digital multimeter, Hioki E.E. Corporation, DT4222). Specifically, on the outermost surface opposite the substrate, the two terminals of the tester were measured at an interval of about 10 cm. The initial electrical resistance value of the outermost surface was 0.8 to 0.9 Ω for all samples.

<Etching ability of anti-rust layer>
Only the various anticorrosive layers employed in the above examples and comparative examples were sputtered on a PET film of 5 cm x about 10 cm. The sample after sputtering was immersed about halfway for about 10 minutes in a beaker containing a 10-fold diluted solution of dilute sulfuric acid (acidic degreaser (DP-320 Clean)) manufactured by Okuno Chemical Industries Co., Ltd., using tweezers, and visually observed whether the anticorrosive layer was etched or not, and evaluated according to the following evaluation criteria. For samples in which the anticorrosive layer is Ni-20Cr, a sample formed by sputtering only the anticorrosive layer on a transparent PI film was immersed about halfway in the same dilute sulfuric acid as above, and the etching property was visually observed. In this evaluation method, in order to make it easier to observe visually, a sample was formed by sputtering only the anticorrosive layer on a transparent PET film alone, but compared to a sample created with an actual configuration, there was no difference in the etching property of the anticorrosive layer by visual observation, so even when the film created in the above examples and comparative examples is used, similar results can be obtained.
(Evaluation Criteria)
◯: The rust-preventive layer was completely removed.
Δ: The rust-preventive layer was not completely removed, but this did not cause any problems in practical use.
×: The rust-preventive layer was not removed and remained.

As shown in Table 1, the films of Examples 1 to 15 of the present invention were able to suppress the increase in electrical resistance value and the anti-corrosive layer was easily removed.

Reference Signs List 1a, 1b Film 2 Substrate 3a, 3b Intermediate layer 4 Thin copper layer 5 Anti-rust layer 6 Plated copper layer 7 Adhesive layer 8 Transfer substrate

Claims (6)

A substrate and a laminate provided on at least one surface of the substrate,
The laminate has, from the base material side, a thin film copper layer and an anticorrosive layer in this order,
The anticorrosive layer includes an alloy of copper and nickel,
The proportion of copper in the copper-nickel alloy in the anticorrosive layer is 35 to 55 mass %,
An intermediate layer is provided between the substrate and the thin-film copper layer;
the intermediate layer comprises an alloy of copper and nickel;
The proportion of the copper in the alloy of copper and nickel in the intermediate layer is 32 to 56 mass %,
The thickness of the intermediate layer is 5 nm or more and 50 nm or less,
The thickness of the thin copper layer is 70 nm or more and 2 μm or less,
The conductive film for circuit boards for copper electrolytic plating , wherein the anticorrosive layer has an average thickness of 1 to 9 nm. A substrate and a laminate provided on at least one surface of the substrate,
The laminate has, from the base material side, a thin film copper layer and an anticorrosive layer in this order,
The anticorrosive layer includes an alloy of copper and nickel,
In the alloy of copper and nickel, the proportion of copper is 35 to 70 mass %,
The average thickness of the anticorrosive layer is 1 to 9 nm;
An intermediate layer is provided between the substrate and the thin-film copper layer;
The conductive film for circuit boards, wherein the intermediate layer contains at least one of a melamine resin, a fluororesin, a urethane resin, a silicone compound, an acrylic resin, a polyethylene wax, and a microcrystalline wax. 3. The conductive film for circuit boards according to claim 1 or 2 , wherein when heat treatment is carried out for 2.5 hours in an atmosphere of 250° C., the electrical resistance value in a region spaced 10 cm apart on the outermost surface opposite the substrate is 30 Ω or less. 3. The conductive film for circuit boards according to claim 1 or 2, wherein when a heating and humidifying treatment is carried out for 500 hours in an atmosphere of 85°C and 85% RH (relative humidity), the electrical resistance of the outermost surface on the outermost surface opposite the substrate is 4.0 Ω or less in an area spaced 10 cm apart. Providing a substrate;
forming a laminate having an intermediate layer, a thin-film copper layer, and an anticorrosive layer in this order from the substrate side on at least one surface side of the substrate;
removing the anticorrosive layer after forming the laminate;
and forming a plated copper layer on the thin-film copper layer by electrolytic plating after removing the rust-proof layer.
The anticorrosive layer includes an alloy of copper and nickel,
the intermediate layer comprises an alloy of copper and nickel;
In the copper-nickel alloy in the anticorrosive layer, the proportion of the copper is 35 to 70 mass %,
The method for producing a conductive film for circuit boards, wherein the anticorrosive layer has an average thickness of 1 to 9 nm. Providing a substrate;
forming a laminate having an intermediate layer, a thin-film copper layer, and an anticorrosive layer in this order from the substrate side on at least one surface side of the substrate;
removing the anticorrosive layer after forming the laminate;
and forming a plated copper layer on the thin-film copper layer by electrolytic plating after removing the rust-proof layer.
The anticorrosive layer includes an alloy of copper and nickel,
the intermediate layer contains at least one of a melamine resin, a fluororesin, a urethane resin, a silicone compound, an acrylic resin, a polyethylene wax, and a microcrystalline wax;
In the alloy of copper and nickel, the proportion of copper is 35 to 70 mass %,
The method for producing a conductive film for circuit boards, wherein the anticorrosive layer has an average thickness of 1 to 9 nm.

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