TWI882245B - Manufacturing method of conductive film for circuit board - Google Patents

Abstract

The present invention provides a thin-film copper layer that is not easily oxidized, prevents the resistance value of the thin-film copper layer from rising before electrolytic plating, and can easily remove the anti-rust layer with acid when manufacturing a conductive film for circuit boards. A conductive film for a substrate and a method for producing a conductive film for a circuit board. A conductive thin film for a circuit board comprising a substrate and a laminate provided on at least one side of the substrate, the laminate having a thin-film copper layer and an antirust layer in this order from the substrate side, the antirust layer containing copper The alloy with nickel, the ratio of copper in the alloy of copper and nickel is 35 to 70% by mass, and the average thickness of the antirust layer is 1 to 9 nm.

Description

Method for producing conductive film for circuit substrate

The present invention relates to a conductive film for a circuit substrate and a method for manufacturing a conductive film for a circuit substrate. More specifically, the present invention relates to a conductive film for a circuit substrate, wherein the thin film copper layer is not easily oxidized, the resistance value of the thin film copper layer can be prevented from increasing before electrolytic plating, and the anti-rust layer can be easily removed by acid when manufacturing the conductive film for a circuit substrate, and a method for manufacturing the conductive film for a circuit substrate.

Traditionally, laminated substrates are used in various fields. Japanese Patent Document 1 discloses a laminated substrate for a metal mesh touch screen.

[Patent Literature]

Patent document 1: Japanese Patent Publication No. 2017-64939

However, in the laminate substrate described in Japanese Patent Document 1, the metal is visually recognized as a grid due to the reflection of the conductive pattern. Therefore, the reflectivity of the low-reflectivity alloy layer on the outermost surface needs to be sufficiently reduced, and the thickness of the low-reflectivity alloy layer needs to be greater than or equal to 10nm.

However, when the known laminated substrate described in Japanese Patent Document 1 is used as a circuit substrate (e.g., FCCL, Flexible Copper Clad Laminate), the outermost low-reflectivity alloy layer must be removed by acid etching before the electroplated copper layer is provided in the copper plating step (electrolytic plating step). However, in the laminated substrate described in Japanese Patent Document 1, the low-reflectivity alloy layer is relatively thick and difficult to be fully removed by acid etching. As a result, in the laminate substrate described in Japanese Patent Document 1, since the electroplated copper layer is formed in a state where the low reflectivity alloy layer remains, the electroplated copper layer may not be well deposited or may be easily peeled off.

The present invention is made in view of the above-mentioned prior art, and its purpose is to provide a conductive film for circuit board, which is not easily oxidized, and the anti-rust layer can be easily removed by acid when manufacturing the conductive film for circuit board, and the resistance value of the thin film copper layer can be prevented from increasing before electrolytic plating, and a method for manufacturing the conductive film for circuit board.

As a result of in-depth research, the inventors of the present invention found that by providing a rust-proof layer containing a copper-nickel alloy of a predetermined ratio and an adjusted thickness on a thin-film copper layer, the oxidation of the thin-film copper layer can be prevented, and the increase in the resistance value of the thin-film copper layer can be prevented before electrolytic plating. Moreover, this rust-proof layer can be easily removed with acid during the manufacture of a conductive film for a circuit substrate, thereby completing the present invention. That is, the conductive film for a circuit substrate and the method for manufacturing a conductive film for a circuit substrate of the present invention, which are used to solve the above-mentioned problems, mainly include the following structure.

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

According to this structure, in the conductive film for circuit substrate, the anti-rust layer can prevent the oxidation of the thin film copper layer, and the increase of the resistance value of the thin film copper layer can be prevented during the period before electrolytic plating. In addition, the anti-rust layer can be easily removed by acid during the manufacturing of the conductive film for circuit substrate.

(2): In the conductive film for circuit substrate described in (1), an intermediate layer is provided between the substrate and the thin film copper layer.

According to this structure, the conductive film for circuit board has better adhesion between the base material and the thin film copper layer.

(3): In the conductive film for circuit substrate described in (2), the intermediate layer contains an alloy of copper and nickel.

According to this structure, when the conductive film for circuit substrate is used as a film for sputter-plated FCCL, for example, the adhesion between the substrate and the thin film copper layer is better.

(4): In the conductive film for circuit substrate described in (2), the intermediate layer contains at least one of melamine resin, fluororesin, polyurethane resin, silicon compound, acrylic resin, polyethylene wax or microcrystalline wax.

According to this structure, when a conductive film for a circuit board is used as a thin-film copper layer transfer film, for example, it is easy to peel off the base material after transfer.

(5): In the conductive film for circuit substrate described in any one of (1) to (4), when subjected to heat treatment at 250°C for 2.5 hours, the resistance value of the area separated by a gap of 10 cm on the outermost surface opposite to the substrate is less than or equal to 30Ω.

According to this structure, the resistance value of the thin film copper layer of the conductive film used in the circuit board can be prevented from increasing.

(6): In the conductive film for circuit substrate described in any one of (1) to (5), when subjected to a heat and moisture treatment at 85°C and 85% RH (relative humidity) for 500 hours, the resistance value of the outermost surface of the area separated by a gap of 10 cm on the outermost surface opposite to the substrate is less than or equal to 4.0Ω.

According to this structure, the resistance value of the thin film copper layer of the conductive film used in the circuit board can be prevented from increasing.

(7): A method for manufacturing a conductive film for a circuit substrate, comprising: a step of preparing a substrate; a step of forming a layer stack having an intermediate layer, a thin film copper layer, and an anti-rust layer in sequence from the substrate side on at least one side of the substrate; a step of removing the anti-rust layer after forming the layer stack; and a step of removing the anti-rust layer. After the anti-rust layer is formed, a step of forming an electroplated copper layer on the thin film copper layer by electrolytic plating is performed. The anti-rust layer contains an alloy of copper and nickel, and the intermediate layer includes an alloy of copper and nickel. The proportion of copper in the copper and nickel alloy of the anti-rust layer is 35-70 mass %, and the average thickness of the anti-rust layer is 1-9 nm.

According to such a structure, in the conductive film for circuit substrate, the anti-rust layer can prevent the oxidation of the thin film copper layer, and the increase of the resistance value of the thin film copper layer can be prevented before electrolytic plating. In addition, the anti-rust layer of the conductive film for circuit substrate can be easily removed by the acid in the acid cleaning step before electrolytic plating.

(8) A method for manufacturing a conductive film for a circuit substrate, comprising: a step of preparing a substrate; a step of forming a layer stack having an intermediate layer, a thin film copper layer, and an anti-rust layer in sequence from the substrate side on at least one side of the substrate; a step of removing the anti-rust layer after forming the layer stack; and a step of applying an electric current to the thin film copper layer after removing the anti-rust layer. The step of forming an electroplated copper layer by electroplating, the anti-rust layer contains an alloy of copper and nickel, the intermediate layer contains at least one of melamine resin, fluorine resin, polyurethane resin, silicon compound, acrylic resin, polyethylene wax or microcrystalline wax, the proportion of copper in the alloy of copper and nickel is 35-70 mass%, and the average thickness of the anti-rust layer is 1-9nm.

According to such a structure, in the conductive film for circuit substrate, the anti-rust layer can prevent the oxidation of the thin film copper layer, and the increase of the resistance value of the thin film copper layer can be prevented before electrolytic plating, and the anti-rust layer of the conductive film for circuit substrate can be easily removed by the acid in the pickling step before electrolytic plating.

〔Invention Effect〕

According to the present invention, a thin film copper layer is not easily oxidized, the resistance value of the thin film copper layer can be prevented from increasing before electrolytic plating, and a conductive film for a circuit substrate can be easily removed by acid when manufacturing a conductive film for a circuit substrate, and a method for manufacturing a conductive film for a circuit substrate can be provided.

1a, 1b: Thin film

2: Base material

3a, 3b: middle layer

4: Thin film copper layer

5: Anti-rust layer

6: Electroplating copper layer

7: Adhesive layer

8: Transfer substrate

Figure 1 is a schematic cross-sectional view of a film according to one embodiment of the present invention.

Figure 2 is a schematic cross-sectional view of a film according to one embodiment of the present invention.

Figure 3 is a schematic cross-sectional view showing a state where the anti-rust layer is removed in a method for manufacturing a thin film according to one embodiment of the present invention.

Figure 4 is a schematic cross-sectional view showing a state in which an electroplated copper layer is formed in a thin film manufacturing method according to one embodiment of the present invention.

Figure 5 is a schematic cross-sectional view showing a state where the anti-rust layer is removed in a method for manufacturing a thin film according to one embodiment of the present invention.

Figure 6 is a schematic cross-sectional view showing a state where an electroplated copper layer is formed in a thin film manufacturing method according to one embodiment of the present invention.

Figure 7 is a cross-sectional schematic diagram showing a state in which the obtained film is transferred to the transferred substrate through an adhesive layer in a method for manufacturing a film according to one embodiment of the present invention, and then the substrate and the intermediate layer are peeled off.

<Conductive film for circuit substrate>

The conductive film for circuit substrate (hereinafter also referred to as film) of one embodiment of the present invention has a substrate and a layer stack provided on at least one side of the substrate. The layer stack has a thin film copper layer and an anti-rust layer in order from the substrate side. The anti-rust layer contains an alloy of copper and nickel. The proportion of copper in the alloy of copper and nickel is 35-70% by mass. The average thickness of the anti-rust layer is 1-9 nm. The following is a description of each.

(Base material)

The substrate is not particularly limited. For example, the substrate may be PI (polyimide), PET (polyethylene terephthalate), PEN (polyethylene naphthol), PMMA (methacrylate resin), PP (polypropylene), PE (polyethylene), COP (cycloolefin polymer resin), PPS (polyphenylene sulfide resin), PS (polystyrene resin), fluororesin (e.g., PTFE, PFA, ETFE, FEP), PEEK (polyetheretherketone resin), etc. By using such substrates, the film of this embodiment is easy to handle and easy to improve productivity.

There is no particular restriction on the thickness of the substrate. For example, the thickness of the substrate is preferably greater than or equal to 6μm, more preferably greater than or equal to 12μm, and more preferably greater than or equal to 25μm. In addition, the thickness of the substrate is preferably less than or equal to 300μm, more preferably less than or equal to 250μm, and more preferably less than or equal to 200μm. When the thickness of the substrate is within the above range, the film has good operability and bendability during processing. In addition, the film is easily applicable to applications for bendable circuit substrates. In addition, the average thickness of the substrate can be appropriately adjusted according to the application of the film. For example, in applications requiring thinner films and higher flexibility, the average thickness of the substrate can be selected to be close to 6μm. In addition, from the perspective of insulation, high reliability, and operability, the average thickness of the substrate can be selected to be close to 300μm.

(middle layer)

The intermediate layer is a layer appropriately disposed between the substrate and the thin film copper layer. In addition, the intermediate layer can be made of an appropriate material according to the purpose of the film (for example, a film for sputtering FCCL or a thin film copper layer transfer film, etc.). The following example is for illustrating the case where the film of this embodiment is a film for sputtering FCCL or a thin film copper layer transfer film.

<Using sputter-plated FCCL film>

FIG. 1 is a schematic cross-sectional view of the film 1a of this embodiment. When the film 1a of this embodiment is a sputter-plated FCCL film, the intermediate layer 3a is provided as a bonding layer for improving the adhesion between the substrate 2 and the thin film copper layer 4. In addition, the element symbol 5 is a rust-proof layer.

The intermediate layer 3a is preferably an alloy containing copper and nickel. This improves the adhesion between the thin film 1a, the substrate 2 and the thin film copper layer 4.

In the copper and nickel alloy, the copper content is preferably greater than or equal to 32 mass%, more preferably greater than or equal to 35 mass%, relative to the total amount of copper and nickel in the intermediate layer 3a. In addition, in the copper and nickel alloy, the copper content is preferably less than or equal to 70 mass%, more preferably less than or equal to 56 mass%, more preferably less than or equal to 45 mass%, and more preferably less than or equal to 40 mass%, relative to the total amount of copper and nickel in the intermediate layer 3a. When the copper content is within the above range, the alloy is no longer a ferromagnetic body at room temperature and can reduce the magnetic permeability. As a result, the alloy is easy to form a film by sputtering. In addition, the intermediate layer 3a can easily improve the adhesion of the interface with the substrate 2 and easily obtain excellent adhesion.

On the other hand, in the alloy of copper and nickel, the content of nickel is preferably greater than or equal to 30 mass%, more preferably greater than or equal to 44 mass%, more preferably greater than or equal to 55 mass%, and particularly preferably greater than or equal to 60 mass% relative to the total amount of copper and nickel in the intermediate layer 3a. In addition, in the alloy of copper and nickel, the content of nickel is preferably less than or equal to 68 mass% relative to the total amount of copper and nickel in the intermediate layer 3a.

The content of the alloy of copper and nickel relative to the total amount of the intermediate layer 3a is preferably greater than or equal to 90 mass%, more preferably greater than or equal to 95 mass%, and even more preferably greater than or equal to 99 mass%. As long as the effect of this embodiment can be exerted, the intermediate layer 3a can contain other components appropriately according to the purpose.

The thickness of the intermediate layer 3a is not particularly limited. For example, the thickness of the intermediate layer 3a is preferably greater than or equal to 3nm, more preferably greater than or equal to 4nm, and more preferably greater than or equal to 5nm. In addition, the thickness of the intermediate layer 3a is preferably less than or equal to 100nm, more preferably less than or equal to 50nm, and more preferably less than or equal to 25nm. When the thickness of the intermediate layer 3a is within the above range, the film 1a has excellent adhesion and excellent productivity.

<The situation of thin film 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 film copper layer transfer film, the intermediate layer 3b is provided as a peeling layer when the substrate 2 is peeled off after transfer. In addition, the element symbol 5 is a rust-proof layer.

The intermediate layer 3b preferably contains at least one of melamine resin, fluororesin, polyurethane resin, silicone compound, acrylic resin, polyethylene wax or microcrystalline wax. Thus, the film 1b can be easily peeled off the substrate 2 after transfer.

In addition, the film 1b of this embodiment is a thin film copper layer transfer film. When the substrate 2 is a fluororesin or an olefin resin, the intermediate layer 3b can also be omitted.

The thickness of the intermediate layer 3b is not particularly limited. For example, the thickness of the intermediate layer 3b is preferably greater than or equal to 10nm, more preferably greater than or equal to 50nm, and more preferably greater than or equal to 100nm. In addition, the thickness of the intermediate layer 3b is preferably greater than or equal to 10μm, more preferably less than or equal to 5μm, and more preferably less than or equal to 1μm. When the thickness of the intermediate layer 3b is within the above range, the film 1b has excellent releasability and excellent productivity.

(Layer)

The layer stack is disposed on at least one side of the substrate. The layer stack has a thin film copper layer and an anti-rust layer in sequence from the substrate side.

<Thin film copper layer>

The thin film copper layer is provided as a base for forming the electrodes of the circuit board. Copper is cheaper and has a lower resistivity than other metals used for the circuit board, so it is suitable as a metal species for forming a conductive pattern for the circuit board. In addition, by providing a thin film copper layer, copper is easily accumulated when the electroplated copper layer is formed later. The thin film copper layer, together with the above-mentioned intermediate layer, is etched into the desired pattern using a photolithography step when the FPC (Flexible Printed Circuit) is formed.

There is no particular limitation on the method of forming a thin film copper layer. For example, the thin film copper layer can be formed by conventional physical evaporation methods such as vacuum evaporation, sputtering, and ion plating. Among them, in the thin film of this embodiment, it is preferred to use sputtering to set the thin film copper layer because the film quality after film formation is good. The sputtering conditions can be appropriately adopted according to the required thickness of the thin film copper layer.

There is no particular restriction on the thickness of the thin film copper layer. For example, the thickness of the thin film copper layer is preferably greater than or equal to 50nm, more preferably greater than or equal to 60nm, and more preferably greater than or equal to 70nm. When the thickness of the thin film copper layer is within the above range, the thin film is easily thickened by copper electrolytic plating. In addition, the thickness of the thin film copper layer is preferably less than or equal to 5μm, more preferably less than or equal to 3μm, and more preferably less than or equal to 2μm. When the thickness of the thin film copper layer is within the above range, the productivity of the thin film is good.

<Anti-rust layer>

The anti-rust layer is provided on the thin-film copper layer. The anti-rust layer is preferentially oxidized (corroded) by oxygen in the air, thereby preventing the oxidation of the thin-film copper layer.

The anti-rust layer includes an alloy of copper and nickel. In the alloy of copper and nickel, the content of copper may be greater than or equal to 32 mass %, preferably greater than or equal to 35 mass %, relative to the total amount of copper and nickel in the anti-rust layer. In addition, in the alloy of copper and nickel, the content of copper may be less than or equal to 70 mass %, preferably less than or equal to 55 mass %, and more preferably less than or equal to 45 mass %. When the content of copper is less than 32 mass % relative to the total amount of copper and nickel in the anti-rust layer, it is difficult to form a film by sputtering because the alloy becomes a ferromagnetic body at room temperature and the magnetic permeability cannot be reduced. On the other hand, when the copper content exceeds 70% by mass relative to the total amount of copper and nickel in the anti-rust layer, the anti-oxidation performance of the thin film anti-rust layer will decrease and the resistance value of the thin film copper layer will easily increase.

On the other hand, in the alloy of copper and nickel, the content of nickel relative to the total amount of copper and nickel in the anti-rust layer is greater than or equal to 30 mass%, preferably greater than or equal to 45 mass%, and more preferably greater than or equal to 55 mass%. When the nickel content is within the above range, the anti-rust layer has better anti-oxidation performance and can suppress the increase in the resistance value of the thin film copper layer. In addition, in the alloy of copper and nickel, the content of nickel relative to the total amount of copper and nickel in the anti-rust layer is less than or equal to 68 mass%, preferably less than or equal to 65 mass%. When the nickel content is within the above range, the alloy of copper and nickel is non-magnetic at room temperature and is easy to form a film of anti-rust layer by sputtering.

The content of the copper and nickel alloy relative to the total amount of the anti-rust layer is preferably greater than or equal to 90 mass%, more preferably greater than or equal to 95 mass%, and even more preferably greater than or equal to 99 mass%. As long as the anti-rust layer can exert the effect of this embodiment, it can contain other components appropriately according to the purpose.

The method for forming the anti-rust layer is not particularly limited. For example, the anti-rust layer can be formed using a conventionally known physical evaporation method such as a sputtering method.

The thickness (average thickness) of the anti-rust layer can be greater than or equal to 1nm, preferably greater than or equal to 3nm, and more preferably greater than or equal to 5nm. In addition, the thickness of the anti-rust layer can be less than or equal to 9nm, and more preferably less than or equal to 7nm. When the thickness of the anti-rust layer is less than 1nm, it is difficult for the thin film to prevent the thin film copper layer from being oxidized. On the other hand, when the thickness of the anti-rust layer exceeds 9nm, the thin film anti-rust layer is difficult to be removed by acid, and when electrolytic plating is performed on it, it is difficult to accumulate the electroplated copper layer or the electroplated copper layer is easily peeled off.

In the present embodiment, the anti-rust layer has fine irregularities. Therefore, the above-mentioned thickness of the anti-rust layer is an average thickness. In the present embodiment, the average thickness of the anti-rust layer can be measured using a fluorescent X-ray measuring device. Specifically, first, a substrate on which a plurality of levels of anti-rust layers of predetermined thickness are formed is prepared, and the physical film thickness of the anti-rust layers of predetermined thicknesses of the plurality of levels is measured using a contact-type step gauge. In addition, a fluorescent X-ray measuring device (XRF, Primini (desktop dispersed fluorescent X-ray analysis device), manufactured by Regaku Co., Ltd. of Japan) is used, and quantitative analysis is used to measure the amount of the anti-rust layer in the plurality of levels of predetermined thickness of the anti-rust layer. A calibration curve is created from the film thickness measured using a contact type step gauge and the amount of anti-rust layer material measured using quantitative analysis of XRF. The film is quantitatively analyzed using XRF to detect nickel and copper from the anti-rust layer, and the average value of the measured values at 10 locations is taken as the average thickness. The average thickness of the anti-rust layer can be considered to be the average value of the above-mentioned fine uneven contours.

Returning to the overall description of the layer stack, the layer stack is disposed on at least one side of the substrate. The layer stack may be disposed on both sides of the substrate.

As described above, in the film of this embodiment, the anti-rust layer can prevent the oxidation of the thin film copper layer, prevent the increase of the resistance value of the thin film copper layer before electrolytic plating, and the anti-rust layer can be easily removed by acid when manufacturing the thin film.

Specifically, when the film of this embodiment is heat treated for 2.5 hours at 250°C, the resistance value of the area separated by a distance of 10 cm on the outermost surface opposite to the substrate is less than or equal to 30Ω, and preferably less than or equal to 10Ω. In this way, the film of this embodiment can prevent the resistance value of the film copper layer from increasing.

In addition, when the film of this embodiment is subjected to a heating and humidification treatment for 500 hours in an environment of 85°C 85% RH (relative humidity), the resistance value of the outermost surface of the area separated by a length of 10 cm on the outermost surface opposite to the substrate is preferably less than or equal to 4.0Ω. In this way, the film of this embodiment can prevent the resistance value of the thin film copper layer from increasing.

In addition, the anti-rust layer is much thinner than the thin-film copper layer. Therefore, the resistance value at the outermost surface represents the resistance value of the anti-rust layer and the thin-film copper layer, and can actually be understood as the resistance value of the thin-film copper layer. Therefore, the outermost resistance value is less than or equal to 30Ω, which means that the resistance value of the thin-film copper layer is of this degree, and it can be said that the oxidation of the thin-film copper layer has been suppressed.

<Method for manufacturing conductive film for circuit substrate>

The following is a method for manufacturing a conductive film for a circuit substrate (hereinafter also referred to as a film manufacturing method) of one embodiment of the present invention, and describes the respective manufacturing methods based on the use of the film as a film for sputtering FCCL and the use of the film as a thin film copper layer transfer film.

(When using sputter-plated FCCL film)

When the film is used as a sputter-plated FCCL film, the film manufacturing method of this embodiment has the following steps: a step of preparing a substrate; a step of forming a layer stack having an intermediate layer, a thin film copper layer, and an anti-rust layer in order from the substrate side on at least one side of the substrate; a step of removing the anti-rust layer after forming the layer stack; and a step of forming an electroplated 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 an alloy of copper and nickel. In the alloy of copper and nickel in the anti-rust layer, the proportion of copper is 35-70 mass %, and the average thickness of the anti-rust layer is 1-9 nm. The following will be described separately. In addition, in the following description, the substrate, the intermediate layer and the stack are the same as those described in the thin film embodiment.

<Steps for preparing a substrate and forming a layer stack>

On at least one side of the prepared substrate, starting from the substrate side, a stacked body having an intermediate layer, a thin film copper layer, and an anti-rust layer is formed in sequence.

There is no particular limitation on the method of laminating the intermediate layer on the substrate. For example, the intermediate layer may be laminated by sputtering or the like.

The method for forming the thin film copper layer on the intermediate layer is not particularly limited. For example, as described above, the thin film copper layer can be formed using a conventionally known physical vapor deposition method such as vacuum evaporation, sputtering, or ion plating.

There is no particular limitation on the method of forming the anti-rust layer on the thin film copper layer. For example, as described above, the anti-rust layer can be formed using a conventionally known physical vapor deposition method such as sputtering.

<Steps to remove the anti-rust layer>

There is no particular limitation on the method of removing the anti-rust layer. For example, the anti-rust layer can be removed by cleaning with an acid such as dilute sulfuric acid, hydrogen peroxide, or ferric chloride. In the film of this embodiment, the thickness of the anti-rust layer is 1 to 9 nm. Therefore, the anti-rust layer is easily and fully removed and is difficult to remain on the copper layer of the film. FIG3 is a cross-sectional schematic diagram showing the state of removing the anti-rust layer 5 (as shown in FIG1 ) in the film manufacturing method of this embodiment.

In addition, before using acid for cleaning, the stack is sometimes subjected to heat treatment. Even in this case, the thin film 1a of this embodiment can prevent the thin film copper layer 4 from being oxidized by providing an anti-rust layer.

<Steps for forming electroplated copper layer>

On the thin film copper layer 4 exposed after removing the anti-rust layer, an electroplated copper layer is formed by electrolytic plating. The conditions of the electrolytic plating method are not particularly limited. For example, the electrolytic plating method can immerse the film in a copper sulfate bath, immerse the electrode in a copper sulfate bath, etc., and then apply a voltage between the film and the electrode, so that the copper ions in the copper sulfate bath can be used to perform a reduction reaction on the thin film copper layer of the film.

FIG. 4 is a schematic cross-sectional view showing a state where an electroplated copper layer 6 is formed in the thin film manufacturing method of this embodiment.

The electrolytic plating method for forming the electroplated copper layer 6 on the thin film copper layer 4 is not particularly limited. For example, the electrolytic plating method can adopt the conditions of using a copper sulfate bath, a copper cyanide bath, a copper pyrophosphate bath, etc. as an electrolytic bath.

The thickness of the electroplated copper layer 6 is not particularly limited. For example, the thickness of the electroplated copper layer 6 is preferably greater than or equal to 1 μm, and more preferably greater than or equal to 2 μm. In addition, the thickness of the electroplated copper layer 6 is preferably less than or equal to 50 μm, and more preferably less than or equal to 30 μm. When the thickness of the electroplated copper layer 6 is within the above range, the film can have the advantages of low resistance and productivity.

By performing the above steps, a thin film having a substrate, an intermediate layer, a thin film copper layer and an electroplated copper layer stacked in sequence is produced. The obtained thin film is covered with a thin film copper layer by a rust-proof layer during its production process. Thus, oxidation of the thin film copper layer is prevented even if the thin film copper layer is heated before electroplating. Therefore, the resistance value of the thin film copper layer can be prevented from increasing before electrolytic plating. In addition, the rust-proof layer is fully removed before forming the electroplated copper layer, and the surface of the thin film copper layer is cleaned. In addition, the electroplated copper layer is formed on the thin film copper layer. At this time, since the electroplated copper layer is formed on a thin film copper layer composed of copper of the same metal species, it is easy to accumulate.

(The case of thin film copper layer transfer film)

When the film is used as a thin film copper layer transfer film, the film manufacturing method of this embodiment has: a step of preparing a substrate; a step of forming a layer stack having an intermediate layer, a thin film copper layer, and an anti-rust layer in sequence from the substrate side on at least one side of the substrate; a step of removing the anti-rust layer after forming the layer stack; and a step of forming an electroplated 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, polyurethane resin, silicone compound, acrylic resin, polyethylene wax, or microcrystalline wax. In the alloy of copper and nickel, the proportion of copper is 35~70 mass%. The average thickness of the anti-rust layer is 1~9nm. The following will be described separately. In the following description, the substrate, the intermediate layer and the stack are the same as those described in the above-mentioned thin film embodiment.

(Process of preparing substrate and forming layer stack)

On at least one side of the prepared substrate, starting from the substrate side, a stacked body having an intermediate layer, a thin film copper layer, and an anti-rust layer is formed in sequence.

There is no particular limitation on the method of laminating the intermediate layer on the substrate. For example, the intermediate layer may be laminated by sputtering.

The method of forming the thin film copper layer on the intermediate layer is not particularly limited. For example, as described above, the thin film copper layer can be formed using conventionally known physical vapor deposition methods such as vacuum evaporation, sputtering, or ion plating.

There is no particular limitation on the method of forming the anti-rust layer on the thin film copper layer. For example, as described above, the anti-rust layer can be formed using a conventionally known physical vapor deposition method such as sputtering.

(Steps to remove the anti-rust layer)

There is no particular limitation on the method of removing the anti-rust layer. For example, when the anti-rust layer is a thin film for sputtering FCCL, it can be removed by the above method. FIG. 5 is a cross-sectional schematic diagram showing the state in which the anti-rust layer 5 (as shown in FIG. 2 ) is removed in the thin film manufacturing method of this embodiment.

(Steps for forming electroplated copper layer)

There is no particular limitation on the method of forming the electroplated copper layer. For example, when the electroplated copper layer is a thin film for sputtering FCCL, it can be formed using the above method.

FIG6 is a schematic cross-sectional view showing the state in which the electroplated copper layer 6 is formed in the thin film manufacturing method of this embodiment.

There is no particular limitation on the electrolytic plating method for forming the electroplated copper layer 6 on the thin film copper layer 4. For example, the electrolytic plating method can use a copper sulfate tank, a copper cyanide tank, a copper pyrophosphate tank, etc. as the electrolyte tank.

The thickness of the electroplated copper layer 6 is not particularly limited. For example, the thickness of the electroplated copper layer 6 is preferably greater than or equal to 1 μm, and more preferably greater than or equal to 2 μm. In addition, the thickness of the electroplated copper layer 6 is preferably less than or equal to 50 μm, and more preferably less than or equal to 30 μm. When the thickness of the electroplated copper layer 6 is within the above range, the film can have the advantages of low resistance and productivity.

By performing the above steps, a thin film is produced in which a substrate, an intermediate layer, a thin film copper layer and an electroplated copper layer are stacked in sequence. During the manufacturing process of the obtained thin film, the thin film copper layer is covered with a rust-proof layer. Thereby, oxidation of the thin film copper layer is prevented even if the thin film copper layer is heated before electroplating. Therefore, the resistance value of the thin film copper layer can be prevented from increasing before electrolytic plating. In addition, the rust-proof layer is fully removed before forming the electroplated copper layer, and the surface of the thin film copper layer is cleaned. In addition, the electroplated copper layer is formed on the thin film copper layer. At this time, since the electroplated copper layer is formed on a thin film copper layer composed of the same metal species of copper, it is easy to accumulate. The obtained thin film is transferred to the transferred substrate through the adhesive layer, and then the intermediate layer and the substrate are peeled off. Figure 7 is a cross-sectional schematic diagram showing the state in which the obtained thin film is transferred to the transferred substrate 8 through the adhesive layer 7 in the thin film manufacturing method of this embodiment, and then the substrate 2 and the intermediate layer 3b are peeled off.

The adhesive layer 7 is not particularly limited. For example, the adhesive layer 7 is composed of acrylic resins, polyurethane resins, polyurethane-modified polyester resins, polyester resins, epoxy resins, ethylene-vinyl acetate copolymers (EVA), vinyl resins (vinyl chloride, acetate, vinyl chloride-acetate copolymers), styrene-ethylene-butylene copolymers, polyvinyl alcohol resins, polyacrylamide resins, polyacrylamide resins, dimaleimide resins, cyanate monomers, isobutylene rubber, isopentyl rubber, natural rubber, SBR, NBR, silicone rubber, PPE, olefins, etc. These resins can be appropriately dissolved in a solvent for use, or can be used without a solvent.

There is no particular restriction on the thickness of the adhesive layer 7. For example, the thickness of the adhesive layer 7 is about 0.5 to 5 μm.

There is no particular limitation on the method of forming the adhesive layer 7. For example, the adhesive layer 7 can be formed by applying a resin solution appropriately dissolved in a solvent constituting the adhesive layer 7 onto the electroplated copper layer 6 using a roller coater or the like and drying it.

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

[Implementation example]

The present invention is described in more detail below by way of examples. The present invention is not limited to these examples. In addition, unless otherwise specified, "%" means "mass %" and "parts" means "mass parts".

<Implementation Example 1>

A substrate (thickness 25μm) made of PI was prepared. A middle layer containing an alloy of copper and nickel was formed on the substrate with a film thickness of 10nm using a sputtering device. Then, a thin film copper layer was formed on the middle layer with a film thickness of 120nm using a sputtering device. After that, a rust-proof layer was formed on the thin film copper layer with a film thickness of 1nm using a sputtering device to produce a conductive thin film for a circuit board.

<Implementation Examples 2 to 15, Comparative Examples 1 to 6>

According to the formula shown in Table 1, except for adjusting the type and thickness of each layer, the conductive film for circuit substrate is produced in the same manner as in Example 1. In addition, in Table 1, "Ni-35 Cu" means that a Ni-Cu alloy sputtering target with 35% Cu and 65% Ni is used. "Ni-55Cu" means that a Ni-Cu alloy sputtering target with 55% Cu (copper) and 45% Ni (nickel) is used. "Ni-70Cu" means that a Ni-Cu alloy sputtering target with 70% Cu (copper) and 30% Ni (nickel) is used. At this time, XPS analysis was performed on the composition ratio of the Ni-Cu alloy in the intermediate layer and the anti-rust layer of the FCCL formed using the Ni-35Cu target, and it was confirmed that there was no substantial difference between the composition ratio of the target and the composition ratio of the thin film itself formed by sputtering. Therefore, it can be considered that the composition ratio of the thin film is the same as the composition ratio of the target. Similarly, the composition ratio of the Ni-Cu alloy in the anti-rust layer formed using the Ni-55Cu and Ni-70Cu targets can be considered to have no substantial difference between the composition ratio of the target and the composition ratio of the thin film itself formed by sputtering. In addition, in Comparative Example 4, no anti-rust layer was set.

[Table 1]

The films obtained in Examples 1 to 15 and Comparative Examples 1 to 6 were evaluated in accordance with the following methods: "The resistance value of the area separated by a length of 10 cm on the outermost surface opposite to the substrate when subjected to a heat treatment at 250°C for 2.5 hours", "The resistance value of the area separated by a length of 10 cm on the outermost surface opposite to the substrate when subjected to a heat and humidification treatment at 85°C 85%RH (relative humidity) for 500 hours", and "The etching property of the anti-rust layer". The results are shown in Table 1.

<The resistance value of the area separated by a 10cm length on the outermost surface opposite to the substrate when heat treated for 2.5 hours at 250°C>

The film was heat treated for 2.5 hours at 250°C. Afterwards, the resistance of the area separated by 10 cm was measured using a commercially available tester (Digital Multimeter, DT4222, manufactured by Hioki Electric Co., Ltd., Japan). Specifically, the two terminals of the tester were separated by about 10 cm from each other on the outermost surface on the opposite side of the substrate. In addition, the initial outermost resistance value was 0.8~0.9Ω for all samples.

<The resistance value of the outermost surface in an area with a length of 10 cm on the outermost surface opposite to the substrate after 500 hours of heating and humidification treatment at 85°C 85%RH (relative humidity)>

The film was heated and humidified for 500 hours in an environment of 85°C 85%RH (relative humidity). Afterwards, the resistance value of the area separated by 10cm was measured on the outermost surface opposite to the substrate using a commercially available tester (Digital Multimeter, DT4222, manufactured by Hioki Electric Co., Ltd., Japan). Specifically, the two terminals of the tester were separated by about 10cm from each other on the outermost surface opposite to the substrate for measurement. In addition, the initial outermost resistance value was 0.8~0.9Ω for all samples.

<Etching properties of the anti-rust layer>

On a PET film of 5 cm × about 10 cm, only the various anti-rust layers used in the above-mentioned examples and comparative examples were sputter-coated. The sputter-coated sample was placed in a beaker filled with a 10-fold diluted solution of dilute sulfuric acid (acid degreasing agent (DP-320 Clean)) of Okuno Pharmaceutical Co., Ltd., Japan, and about half of it was dipped with a small tweezer for about 10 minutes. The anti-rust layer was visually observed to see if it was corroded, and the evaluation was performed according to the following evaluation criteria. In addition, for the sample with Ni-20Cr as the anti-rust layer, about half of the sample formed by sputter-coating only the anti-rust layer on the transparent PI film was dipped in the same dilute sulfuric acid as above, and the etching property was visually observed. In addition, in this evaluation method, in order to facilitate visual observation, only the anti-rust layer was sputter-plated on a single transparent PET film to form a sample, but when compared with the sample made with the actual structure, there was no difference in the etching property of the anti-rust layer by visual observation, so even when using the film made in the above-mentioned embodiment and comparative example, the same result can be obtained.

(Evaluation criteria)

○: The anti-rust layer is completely removed.

△: The anti-rust layer is not completely removed, but there is no problem in actual use.

×: The anti-rust layer is not removed and remains.

As shown in Table 1, the films of Examples 1 to 15 of the present invention can suppress the increase in resistance value and the anti-rust layer can be easily removed.

1a: Thin film 2: Substrate 3a: Intermediate layer 4: Thin film copper layer 5: Anti-rust layer

Claims (1)

A method for manufacturing a conductive film for a circuit substrate comprises: a step of preparing a substrate; a step of forming a layer stack having an intermediate layer, a thin film copper layer, and an anti-rust layer in sequence from the substrate side on at least one side of the substrate; a step of removing the anti-rust layer after forming the layer stack; a step of forming an electroplated copper layer on the thin film copper layer by electrolytic plating after removing the anti-rust layer; and a step of transferring the layer stack to a transferred substrate after forming the electroplated copper layer, and removing the substrate and the intermediate layer; the anti-rust layer contains an alloy of copper and nickel, The intermediate layer contains at least one of melamine resin, fluorine resin, polyurethane resin, silicon compound, acrylic resin, polyethylene wax or microcrystalline wax. In the alloy of copper and nickel, the proportion of copper is 35 to 70 mass %. The average thickness of the anti-rust layer is 1 to 9 nm.