Metal plating film forming method and film forming device

Abstract

To provide a film forming method capable of stably coating a metal film of uniform film quality on an aluminum substrate, and a film forming device therefor.SOLUTION: The method of forming a metal film on an aluminum substrate comprising a zinc underlayer, comprises: arranging a solid electrolyte membrane between an anode and a cathode, i.e., the aluminum substrate; arranging a solution including a metal ion of metal to be plated on the aluminum substrate between the anode and the solid electrolyte membrane; and causing the solid electrolyte membrane to contact with the aluminum substrate, pressurizing the solution, and pressurizing the aluminum substrate via the solid electrolyte membrane being pressurized by the solution, while applying a voltage to the anode to precipitate the metal ion contained inside the solid electrolyte membrane onto the zinc underlayer of the aluminum substrate.SELECTED DRAWING: Figure 1B

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for forming a metal plating film (also referred to simply as a "film" or "metal film" in this specification, etc.). [Background technology]

[0002] Conventionally, when manufacturing an electronic circuit board or the like, a metal film is formed on the surface of the substrate to form a metal circuit pattern. For example, as a film formation technique for forming such a metal film, a film formation technique has been proposed in which a metal film is formed on the surface of a semiconductor substrate such as Si by a plating process such as electroless plating, or a PVD method such as sputtering.

[0003] However, when plating processes such as electroless plating are performed, rinsing with water is required after plating, and the rinsing wastewater must be treated. Also, when a film is formed on a substrate surface by a PVD method such as sputtering, internal stress occurs in the coated metal film, which limits how thick the film can be made. In particular, in the case of sputtering, film formation is sometimes only possible under high vacuum.

[0004] In view of these points, for example, a metal film forming apparatus has been proposed that uses an anode, a cathode, a solid electrolyte disposed between the anode and the cathode, and a power supply unit that applies a voltage between the anode and the cathode.

[0005] In this device, the anode is made of a metal material that forms the metal coating, and by applying a voltage to the anode and cathode from a power supply, a portion of the anode is ionized, and the metal ions pass through the solid electrolyte and are deposited on the substrate placed on the cathode side, coating the surface of the substrate with a metal coating.

[0006] Furthermore, as an example of a technique in which an insoluble anode can be used as the anode, Patent Document 1 discloses a method for forming a metal film, which comprises disposing a solid electrolyte membrane between an anode and a cathode, contacting the solid electrolyte membrane with a substrate, conducting the cathode to the substrate, applying a voltage between the anode and the cathode, and depositing metal ions contained in the solid electrolyte membrane on the cathode side, thereby forming a metal film made of the metal of the metal ions on the surface of the substrate, the method comprising disposing a solution containing the metal ions between the anode and the solid electrolyte membrane, and pressurizing the solution when the solid electrolyte membrane is brought into contact with the substrate, thereby forming the metal film while pressurizing the substrate via the solid electrolyte membrane with the hydraulic pressure of the solution.

[0007] Patent Document 2 discloses a metal film forming apparatus including an anode, a solid electrolyte membrane disposed between the anode and a substrate serving as a cathode, and a power supply unit that applies a voltage between the anode and the substrate, the apparatus contacting the solid electrolyte membrane with the surface of the substrate and applying a voltage between the anode and the substrate to deposit a metal from metal ions contained inside the solid electrolyte membrane onto the surface of the substrate, thereby forming a metal film made of the metal, the apparatus comprising: a mounting table on which the substrate is placed; and a suction unit that, when forming the metal film, sucks the solid electrolyte membrane from the substrate side so that the solid electrolyte membrane is in close contact with the surface of the substrate placed on the mounting table.

[0008] Patent Document 3 discloses a method for forming a nickel film, which includes arranging an anode, a metal substrate functioning as a cathode, and a solid electrolyte membrane containing a solution containing nickel ions and chloride ions so that the solid electrolyte membrane is located between the anode and the metal substrate and in contact with the surface of the metal substrate, and applying a voltage between the anode and the metal substrate to form a nickel film on the surface of the metal substrate in contact with the solid electrolyte membrane, wherein the solution contains at least one nickel salt as a nickel source, a solvent, and optionally a pH buffer, the at least one nickel salt being selected from the group consisting of nickel chloride, nickel sulfate, and nickel acetate, and the chloride ion concentration is 0.002 to 0.1 mol / L. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-051701 [Patent Document 2] International Publication No. 2015 / 072481 [Patent Document 3] Japanese Patent Application Laid-Open No. 2018-159120 Summary of the Invention [Problem to be solved by the invention]

[0010] In the solid-state electrodeposition (SED) method, which coats a metal film on a substrate surface, when metallic aluminum is used as the substrate, an oxide film forms on the surface of the aluminum substrate, and plating does not adhere to this oxide film. Therefore, the surface of the aluminum substrate to be plated is usually plated in advance with zinc or other metals.

[0011] However, the zinc coating (zinc underlayer) formed on the aluminum substrate is an amphoteric element that dissolves in acids and bases, and can easily be corroded by contact with a solution containing dissolved metals such as copper and nickel, which are to be further formed on the aluminum substrate.

[0012] The present invention has been made in view of the above points, and an object of the present invention is to provide a metal coating forming method and a film forming apparatus that can stably coat an aluminum substrate with a metal coating having uniform film quality. [Means for solving the problem]

[0013] The present inventors have investigated various means for solving the above-mentioned problems, and as a result, have found that a method for forming a metal coating comprising the metal comprises disposing a solid electrolyte membrane between an anode and an aluminum substrate having a zinc underlayer as a cathode, disposing a solution containing metal ions of the metal to be plated on the aluminum substrate between the anode and the solid electrolyte membrane, and bringing the solid electrolyte membrane into contact with the zinc underlayer of the aluminum substrate, thereby pressurizing the solution and depositing the metal ions contained in the solid electrolyte membrane onto the aluminum substrate using the hydraulic pressure of the solution to pressurize the aluminum substrate via the solid electrolyte membrane, thereby depositing the metal ions contained within the solid electrolyte membrane onto the aluminum substrate. In this method, the inventors have found that, by starting application of a voltage to the anode before contacting the aluminum substrate with the solid electrolyte membrane containing the solution, a metal coating having uniform film quality can be stably coated on the zinc underlayer of the aluminum substrate, thereby completing the present invention.

[0014] That is, the gist of the present invention is as follows. (1) A method for forming a metal coating on an aluminum substrate having a zinc underlayer, comprising: a solid electrolyte membrane is disposed between an anode and the aluminum substrate as a cathode; a solution containing metal ions of a metal to be plated onto the aluminum substrate is placed between the anode and the solid electrolyte membrane; While applying a voltage to the anode, the solid electrolyte membrane is brought into contact with the aluminum base material, and the solution is pressurized. In response to the pressurization, the aluminum base material is pressurized via the solid electrolyte membrane, thereby depositing the metal ions contained within the solid electrolyte membrane onto the zinc underlayer of the aluminum base material. The method. (2) The method according to (1), wherein the solution contains nickel ions. (3) A metal film forming apparatus comprising: an anode; a spare anode connected in parallel to the anode; a cathode that is an aluminum substrate having a zinc underlayer; a solution storage section that stores a solution containing metal ions and is disposed between the anode and the cathode; a pressurizing section that pressurizes the solution in the solution storage section; a solid electrolyte membrane provided in the solution storage section that is pressurized together with a surface of the cathode when the pressurizing section pressurizes the solution; and a power supply section that applies a voltage between the anode and / or the spare anode and the cathode, the spare anode is disposed in the solution storage section at a position such that the power supply section, the solution, the solid electrolyte membrane, and the cathode can be electrically connected to each other immediately after the solution is introduced into the solution storage section, the film-forming device introduces the solution while applying a voltage to the spare anode, thereby simultaneously establishing conduction between the power supply unit, the spare anode, the solid electrolyte membrane, the solution, and the cathode, thereby forming a metal film of the metal ions on the cathode; The film forming apparatus. (4) The film forming apparatus according to (3), wherein the spare anode is disposed directly above the solid electrolyte membrane below the solution storage section. (5) The film forming apparatus according to (3) or (4), wherein the solution contains nickel ions. [Effects of the Invention]

[0015] The present invention provides a method and apparatus for forming a metal film that can stably coat an aluminum substrate with a metal film having uniform film quality. [Brief explanation of the drawings]

[0016] [Figure 1A] FIG. 1 is a schematic cross-sectional view of a film forming apparatus 1A. [Figure 1B] FIG. 1B is a diagram illustrating a process of forming a metal coating F on a surface (zinc underlayer) Ba of an aluminum substrate B using the film forming apparatus 1A of FIG. 1A. [Figure 2] 1 is a digital microscope image showing the state of the zinc underlayer of the aluminum substrate when a solution containing nickel ions is dropped onto the zinc underlayer of the aluminum substrate in Example I-1. Corrosion experiment of the zinc underlayer. [Figure 3] 1 is a graph showing the relationship between voltage application time and inter-electrode potential in Example 1. [Figure 4] 10 is a graph showing the relationship between voltage application time and inter-electrode potential in Comparative Example 1. [Figure 5] 1 shows digital microscope images (N=3) showing the state of a nickel coating plated on a zinc underlayer of an aluminum substrate in Example 1. [Figure 6] 1 shows digital microscope images (N=3) showing the state of a nickel coating plated on a zinc underlayer of an aluminum substrate in Comparative Example 1. [Figure 7] 1 is a digital microscope image (N=2) showing the state of a nickel coating plated on a zinc underlayer of an aluminum base material in Comparative Example 2. [Figure 8] FIG. 1 is a diagram comparing a conventional method for forming a metal film with a method for forming a metal film of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Preferred embodiments of the present invention will now be described in detail. In this specification, the features of the present invention will be described with reference to the drawings as appropriate. In the drawings, the dimensions and shapes of various parts are exaggerated for clarity and do not accurately depict the actual dimensions and shapes. Therefore, the technical scope of the present invention is not limited to the dimensions and shapes of various parts shown in these drawings. The metal plating film forming method and film forming apparatus of the present invention are not limited to the following embodiments, and can be embodied in various forms incorporating modifications and improvements that can be made by those skilled in the art without departing from the spirit of the present invention.

[0018] The present invention relates to a method for forming a metal coating on an aluminum substrate having a zinc underlayer, comprising: disposing a solid electrolyte membrane between an anode and the aluminum substrate as a cathode; disposing a solution containing metal ions of a metal to be plated on the aluminum substrate between the anode and the solid electrolyte membrane; applying a voltage to the anode while bringing the solid electrolyte membrane into contact with the aluminum substrate; pressurizing the solution and, in conjunction with the pressurization, pressurizing the aluminum substrate via the solid electrolyte membrane; and depositing the metal ions contained inside the solid electrolyte membrane on the zinc underlayer of the aluminum substrate.

[0019] According to the present invention, during film formation, with a solution containing metal ions disposed between the anode and the solid electrolyte membrane, a power supply disposed between the anode and the aluminum substrate having a zinc underlayer starts applying voltage to the anode, and then the solid electrolyte membrane is brought into contact with the aluminum substrate, thereby electrically connecting the power supply, the anode, the solution, the solid electrolyte membrane, and the aluminum substrate, and simultaneously energizing the anode. As a result, the metal ions contained in the solution migrate from the anode side to the cathode side and are incorporated into the solid electrolyte membrane, and these metal ions can be deposited on the cathode side of the solid electrolyte membrane, i.e., on the zinc underlayer of the aluminum substrate.

[0020] Solutions containing metal ions are often acidic or alkaline to dissolve the metal. When such solutions come into contact with a zinc underlayer on an aluminum substrate surface, they oxidize the zinc through a redox reaction, dissolving it as zinc ions in the solution and potentially generating hydrogen gas. Furthermore, in this reaction, electrons present in the substrate can also affect the dissolution of zinc and the generation of hydrogen gas (corrosion). In the present invention, simultaneous conduction and current application can provide a deposition potential for the reduction of metal ions to metal, i.e., the formation of a metal coating on the zinc underlayer, before the redox reaction occurs. The electrons present in the substrate can also be used for the formation of the metal coating, rather than for the corrosion of zinc. Therefore, the present invention can suppress the corrosion of a zinc underlayer on an aluminum substrate surface by a solution, specifically, the partial dissolution of zinc and the generation of hydrogen gas due to the redox reaction caused by contact between the solution (especially an acidic solution) and zinc.

[0021] In addition, in the present invention, when the solid electrolyte membrane is brought into contact with the aluminum substrate, a solution containing metal ions is pressurized, and the liquid pressure of the solution pressurizes the aluminum substrate via the solid electrolyte membrane, thereby forming a metal coating. As a result, according to Pascal's principle, the liquid pressure of the pressurized solution allows the solid electrolyte membrane to uniformly pressurize the surface of the aluminum substrate.

[0022] Here, the thickness of the metal coating increases as it is formed. If the thickness of the solid electrolyte membrane to be formed is thin and the solid electrolyte membrane is flexible, the distance between the solid electrolyte membrane and the aluminum substrate may be constant. However, in a more preferred embodiment, the distance between the solid electrolyte membrane and the aluminum substrate is increased in accordance with the increase in the thickness of the metal coating during deposition. According to this embodiment, the distance between the solid electrolyte membrane and the aluminum substrate is increased in accordance with the increase in the thickness of the metal coating to be formed. Therefore, the solid electrolyte membrane is hardly bent (deformed) due to the increase in the metal coating thickness, and a metal coating with excellent uniformity can be formed.

[0023] In an even more preferred embodiment, the solution is placed in a sealed space, the solution in the sealed space is pressurized, and a metal coating is formed while the solution is maintained in a pressurized state, and the increase in the thickness of the metal coating is estimated by measuring the liquid pressure of the solution.

[0024] According to this aspect, as the film thickness increases, the pressurized solution in the sealed space is further pressurized via the solid electrolyte membrane, and the film thickness itself of the metal film can be controlled based on the increase in the liquid pressure of the solution. Here, by using this estimated increase in the film thickness of the metal film, it is possible to easily increase the distance between the solid electrolyte membrane and the aluminum base material in accordance with the increase in film thickness, as in the above-mentioned aspect.

[0025] In a more preferred embodiment, the metal coating is formed using an anode having a shape corresponding to the deposition region on the surface of the aluminum substrate where the metal coating is to be formed. According to this embodiment, by using an anode having a shape corresponding to the deposition region, the electric field lines directed from the anode to the aluminum substrate can be made uniform. This allows a metal coating with excellent uniformity to be formed in the desired deposition region.

[0026] The present invention further discloses a metal film forming apparatus more suitable for carrying out the above-mentioned metal film forming method. The metal film forming apparatus according to the present invention includes an anode, a spare anode, a cathode, a solution storage unit, a pressurizing unit, a solid electrolyte membrane, and a power supply unit. The cathode is an aluminum substrate having a zinc underlayer. The solution storage unit is for storing a solution containing metal ions and disposed between the anode and the cathode. The pressurizing unit is for pressurizing the solution in the solution storage unit. The power supply unit is for applying a voltage between the anode and / or the spare anode and the cathode. The solid electrolyte membrane is disposed in the solution storage unit between the anode and the cathode at a position such that the liquid pressure of the solution pressurized by the pressurizing unit pressurizes the solid electrolyte membrane and the surface of the cathode. The spare anode is arranged in the solution storage section at a position where, immediately after the solution is introduced into the solution storage section, the power supply section, the solution, the solid electrolyte membrane, and the cathode can be electrically connected, for example, below the solution storage section, i.e., directly above the solid electrolyte membrane, so as to be connected in parallel with the anode. In the metal coating deposition apparatus of the present invention, by introducing the solution while applying a voltage to the spare anode, electrical conduction occurs between the power supply section, the spare anode, the solid electrolyte membrane, the solution contained inside the solid electrolyte membrane, and the cathode, and at the same time, electrical conduction occurs, and a metal coating made of the metal of the metal ions is deposited on the cathode.

[0027] According to the film-forming apparatus of the present invention, during film formation, an anode, a solution container for containing a metal ion-containing solution, a solid electrolyte membrane, and an aluminum substrate having a zinc underlayer as a cathode are arranged in a state in which a power supply unit arranged between the anode and the aluminum substrate begins to apply voltage to a spare anode connected in parallel to the anode. As soon as the metal ion-containing solution is then introduced into the solution container, electrical conduction occurs among the power supply unit, the spare anode, the solution, the solid electrolyte membrane, and the aluminum substrate, and current is passed through. As a result, the metal ions contained in the solution migrate from the spare anode side toward the cathode side and are incorporated into the solid electrolyte membrane. These metal ions can then be deposited on the cathode side of the solid electrolyte membrane, i.e., on the zinc underlayer of the aluminum substrate.

[0028] Solutions containing metal ions are often acidic or alkaline to dissolve the metal. When such solutions come into contact with a zinc underlayer on an aluminum substrate, they oxidize the zinc through a redox reaction, dissolving it as zinc ions in the solution and potentially generating hydrogen gas. Furthermore, in this reaction, electrons present in the substrate can also affect the dissolution of zinc and the generation of hydrogen gas (corrosion). In the present invention, simultaneous conduction and current application can provide a deposition potential for reducing metal ions to metal, i.e., for forming a metal coating on the zinc underlayer, before the redox reaction occurs. The electrons present in the substrate can also be used for forming the metal coating, rather than for corroding the zinc. Therefore, the present invention can suppress corrosion of the zinc underlayer on the aluminum substrate surface by the solution, specifically, the partial dissolution of zinc and the generation of hydrogen gas due to the redox reaction caused by contact between the solution (especially an acidic solution) and zinc, particularly in large-scale film formation processes where it may take a long time to fill the solution container with the solution. Note that after the solution container is filled to the extent that the solution contacts the anode, the voltage application can be switched from the auxiliary anode to the anode.

[0029] Furthermore, in the present invention, when the solid electrolyte membrane is brought into contact with the aluminum substrate, the solution in the solution container is pressurized by the pressurizing unit, so that the aluminum substrate is pressurized via the solid electrolyte membrane by the hydraulic pressure of the solution, thereby forming a metal coating. As a result, according to Pascal's principle, the solid electrolyte membrane in the solution container can uniformly pressurize the surface of the aluminum substrate by the hydraulic pressure of the pressurized solution.

[0030] Here, the thickness of the metal coating increases as it is formed. Here, if the thickness of the solid electrolyte membrane to be formed is thin and the solid electrolyte membrane is flexible, the distance between the solid electrolyte membrane and the aluminum substrate may be constant. However, in a more preferred embodiment, the distance between the solid electrolyte membrane and the aluminum substrate is increased in accordance with the increase in the thickness of the metal coating during deposition. According to this embodiment, the distance between the solid electrolyte membrane and the aluminum substrate is increased in accordance with the increase in the thickness of the metal coating to be formed. Therefore, the solid electrolyte membrane is hardly bent (deformed) due to the increase in the metal coating thickness, and a metal coating with excellent uniformity can be formed.

[0031] In a preferred embodiment, the anode and / or spare anode has a shape corresponding to the film-forming region on the surface of the aluminum base where the metal coating is to be formed. According to this embodiment, by using an anode and / or spare anode shaped according to the film-forming region, the electric field lines directed from the anode and / or spare anode to the aluminum base can be made uniform. This allows a metal coating with excellent uniformity to be formed in the desired film-forming region.

[0032] A film forming apparatus that can suitably carry out the metal film forming method according to the embodiment of the present invention will be described below.

[0033] 1A is a schematic cross-sectional view of a film formation apparatus 1A. The film formation apparatus 1A includes an anode 11, an aluminum substrate B having a zinc underlayer on its surface Ba as a cathode, a solid electrolyte membrane 13 disposed between the anode 11 and the aluminum substrate B, and a power supply unit 16 that applies a voltage between the anode 11 and / or a spare anode 12 and the aluminum substrate B.

[0034] The film forming apparatus 1A further includes a housing 20. The housing 20 is formed with a solution storage section 21 for storing a solution L containing metal ions so that the solution L containing metal ions can be placed between the anode 11 and the solid electrolyte membrane 13.

[0035] An opening 22 larger than the surface (zinc underlayer) Ba of the aluminum substrate B is formed in the solution storage section 21. The opening 22 is covered with a solid electrolyte membrane 13. A solution L containing metal ions is stored in a tank T in a state in which it can flow into the solution storage section 21, i.e., in a state in which it can be introduced and / or discharged by a pump P and, if necessary, an on-off valve (not shown). Note that, although the introduction and / or discharge of the solution L containing metal ions is performed in one tank T in FIG. 1A, the introduction and / or discharge may be performed in two or more separate tanks.

[0036] Furthermore, the solution storage section 21 of the housing 20 is provided with a spare anode 12 below, that is, directly above the solid electrolyte membrane 13 .

[0037] The film forming apparatus 1A further includes a mounting table 40 on which the substrate B is placed.

[0038] The film forming apparatus 1A further includes a pressure applying unit 30A on the upper part of the housing 20.

[0039] FIG. 1B illustrates a process for forming a metal coating F on a surface Ba of an aluminum substrate B using the film forming apparatus 1A of FIG. 1A.

[0040] As shown in FIG. 1B , with a voltage applied to the spare anode 12 by the power supply unit 16, the aluminum base material B is placed on the mounting table 40 so that the zinc underlayer Ba and the solid electrolyte membrane 13 are in contact with each other, and the mounting table 40 and the housing 20 are moved relative to each other to sandwich the aluminum base material B between the solid electrolyte membrane 13 and the mounting table 40. Then, a solution L containing metal ions is introduced into the solution storage unit 21, and the solution L containing metal ions is placed on the surface Ba of the aluminum base material B via the solid electrolyte membrane 13.

[0041] 1B, a voltage has been applied to the spare anode 12 in advance, and thus, electrical conduction is established among the power supply unit 16, the spare anode 12, the solution L containing metal ions, the solid electrolyte membrane 13, and the aluminum substrate B, and electricity flows simultaneously, whereby the metal ions contained in the solid electrolyte membrane 13 are reduced on the surface Ba of the aluminum substrate B, causing the metal to deposit on the surface Ba, thereby forming a metal coating F.

[0042] The film forming apparatus is equipped with a moving unit (pressure applying unit) that moves the solid electrolyte membrane and the aluminum substrate relatively so as to increase the distance between them in accordance with the increase in the thickness of the metal coating during the formation of the metal coating. According to the present invention, the moving unit can increase the distance between the solid electrolyte membrane and the aluminum substrate in accordance with the increase in the thickness of the metal coating to be formed, so that there is almost no deformation of the solid electrolyte membrane due to the increase in the thickness of the metal coating, and a metal coating with excellent uniformity can be formed.

[0043] The film forming apparatus may also be provided with a pressure gauge (liquid pressure measuring unit) (not shown) that measures the liquid pressure of the solution L containing metal ions contained in the sealed space of the housing 20.

[0044] Furthermore, the film forming apparatus may be provided with a control device (controller) (not shown) that estimates an increase in the thickness of the metal film during film formation based on the hydraulic pressure of the solution measured by the hydraulic pressure measuring unit, and controls the relative movement amount of the solid electrolyte film and the aluminum base material by the moving unit based on the estimated increase in the thickness of the metal film.

[0045] The pressure gauge is preferably electrically connected to the control unit so that the pressure value of the metal ion-containing solution L measured by the pressure gauge is input as a signal to the control unit, which controls the pressurizing unit 30A, the piping, the pump P, etc. According to this embodiment, the metal ion-containing solution L is contained in an enclosed space, the solution in the enclosed space is pressurized by the pressurizing unit 30A, and a metal coating is formed while maintaining the solution in a pressurized state. Therefore, the liquid pressure of the solution also increases according to the increase in the metal coating thickness. This allows the increase in the thickness of the metal coating to be estimated by measuring the liquid pressure of the solution, and the thickness of the metal coating can be controlled. The control unit can control the distance between the solid electrolyte membrane and the aluminum substrate based on this estimated increase in the thickness of the metal coating, resulting in the automatic formation of a metal coating with superior uniformity.

[0046] In the present invention, the anode may be, but is not limited to, a metal coated on an aluminum substrate, such as nickel, oxygen-free copper, or a metal nobler than the metal of the metal ion that is insoluble in the solution containing the metal ion, such as gold. Therefore, the anode may be a soluble anode or an insoluble anode.

[0047] The spare anode may have the same structure as the anode described above, i.e., may be a metal coated on an aluminum substrate, such as nickel, oxygen-free copper, or a metal nobler than the metal of the metal ion that is insoluble in the metal ion-containing solution, such as gold, although the spare anode is not limited thereto. The spare anode may be a soluble or insoluble spare anode.

[0048] In the present invention, a zinc underlayer is formed on the surface of an aluminum substrate (cathode). The zinc underlayer on the surface of the aluminum substrate may be present on the surface of the aluminum substrate to be plated. The zinc underlayer may be formed by a method known in the art, for example, by a double zincate method. The aluminum substrate on which the zinc underlayer is formed may be a substrate made of a metal material such as aluminum, or a substrate on which aluminum metal is formed as an underlayer on the treatment surface of a resin or silicon substrate.

[0049] In the present invention, the solid electrolyte membrane is not limited as long as it can be impregnated with metal ions by contacting it with a solution containing metal ions and can precipitate metal derived from the metal ions on the zinc underlayer on the surface of the aluminum substrate when an electric current is applied. Examples of materials for the solid electrolyte membrane include fluorine-based resins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon-based resins, polyamic acid resins, and resins with ion exchange function such as Selemion (CMV, CMD, CMF series) manufactured by Asahi Glass Co., Ltd.

[0050] In the present invention, the thickness of the solid electrolyte membrane is, for example, usually 1 μm to 400 μm, and preferably 3 μm to 100 μm.

[0051] In the present invention, examples of the metal coating to be applied to the zinc underlayer of the aluminum substrate include nickel, copper, and gold coatings. When preparing a solution containing metal ions, examples of metal compounds to be added and dissolved include halogen compounds such as chlorides and bromides, inorganic salts such as sulfates, sulfamate, and nitrates, and organic salts such as acetates and citrates of the metal. Specific examples of nickel compounds include nickel chloride, nickel sulfate, nickel sulfamate, nickel nitrate, and nickel acetate. Examples of copper compounds include copper chloride, copper sulfate, and copper acetate. These compounds can be used alone or in combination. The concentration of the metal ions is not limited to, but is, for example, 0.1 mol / L to 2.0 mol / L, more preferably 0.8 mol / L to 1.2 mol / L. A solution containing nickel ions is preferred.

[0052] In the present invention, the pH of the solution containing metal ions is not limited. In the present invention, current is applied simultaneously when the power supply, anode (spare anode), solution, solid electrolyte membrane, and aluminum substrate are electrically connected, thereby suppressing corrosion of the zinc underlayer due to the pH of the solution. Therefore, the pH of the solution containing metal ions may be particularly acidic, e.g., pH 1 to 4, or basic, e.g., pH 8 to 11. The pH of the solution containing metal ions is preferably 2.0 to 5.0, and more preferably 2.5 to 4.5. Setting the pH within this range can improve the metal deposition current efficiency and facilitate rapid formation of a metal film. The deposition rate of the metal film can be adjusted by conditions other than pH, such as the metal ions in the solution, current value, anode material, anode area, and temperature.

[0053] In the present invention, the solution containing metal ions may contain any other components in addition to the metal ions. The solution containing metal ions may contain, for example, a solvent and a pH buffer. Examples of the solvent include water or ethanol. Examples of the pH buffer include an acetate buffer or a succinate buffer. [Example]

[0054] The present invention will be described in more detail below using examples and comparative examples, but the technical scope of the present invention is not limited to these examples.

[0055] I-1. Corrosion experiment of zinc substrate (1) A zinc undercoat was plated on the surface of an aluminum substrate by the double zincate method. (2) The aluminum substrate with the zinc underlayer prepared in (1) was heated to 60°C on a hot plate. (3) In (2), a few drops of a solution containing nickel ions (Top Sedona BN (nickel sulfamate), manufactured by Okuno Chemical Industries Co., Ltd., pH 4) were dropped onto the zinc undercoat layer of the aluminum substrate heated to 60°C. (4) The state of the zinc underlayer on the surface of the aluminum substrate onto which the solution was dropped in (3) was observed using a digital microscope (VHX-1000, manufactured by Keyence Corporation) immediately after dropping the solution (0 seconds), 10 seconds, 20 seconds, 30 seconds, and 3 minutes later.

[0056] I-2. Results The results are shown in Figure 2. Figure 2 shows that the zinc underlayer on the surface of the aluminum substrate begins to corrode (dissolve and generate hydrogen gas) approximately 10 to 20 seconds after the solution containing nickel ions is dropped onto it, forming uneven corrosion.

[0057] II-1. Plating experiment on aluminum substrate [Example 1] (1) A nickel anode as an anode, a solution container for filling with a solution containing metal ions of the metal to be plated and placed in contact with the anode, and a solid electrolyte membrane (Nafion NRE212, manufactured by DuPont) placed so as to cover the opening of the solution container were prepared in a housing, and an anode unit including the anode, solution container, and solid electrolyte membrane was assembled. (2) The solution containing the anode prepared in (1) was filled with a solution containing nickel ions (Top Sedona BN (nickel sulfamate), manufactured by Okuno Chemical Industries Co., Ltd., pH 4). (3) A voltage was applied to the anode of the anode part filled with the solution containing nickel ions in (2) using a power source connected to the anode. (4) In (3), while applying a voltage to the anode, the solid electrolyte membrane was brought into contact with an aluminum substrate (aluminum plate (A1050), 50 mm x 50 mm x 2 mm) having a zinc underlayer formed by the double zincate method as the cathode, thereby conducting electricity between the power source, anode, solution, solid electrolyte membrane, and aluminum substrate. The temperature was 55°C, and the current density was 48.8 mA / cm. 2 The aluminum substrate was masked with PI tape to leave an opening of 20 mm x 10 mm, and the film was formed only on the opening. (5) In the circuit energized in (4), pressurization of the solution was started, and the liquid pressure of the solution pressurized the solid electrolyte membrane and further the aluminum substrate through the solid electrolyte membrane. (6) In (5), a nickel coating was deposited on the zinc underlayer of the aluminum substrate by applying a pressure of 1 MPa for 300 seconds.

[0058] [Comparative Example 1] (1) A nickel anode as an anode, a solution container for filling with a solution containing metal ions of the metal to be plated and placed in contact with the anode, and a solid electrolyte membrane (Nafion NRE212, manufactured by DuPont) placed so as to cover the opening of the solution container were prepared in a housing, and an anode unit including the anode, solution container, and solid electrolyte membrane was assembled. (2) The solution containing the anode prepared in (1) was filled with a solution containing nickel ions (Top Sedona BN (nickel sulfamate), manufactured by Okuno Chemical Industries Co., Ltd., pH 4). (3) The solid electrolyte membrane in the anode part filled with the solution in (2) was brought into contact with an aluminum substrate (aluminum plate (A1050), 50 mm × 50 mm × 2 mm) having a zinc underlayer formed by the double zincate method as a cathode. The aluminum substrate was masked with PI tape to leave an opening of 20 mm × 10 mm, and the film was formed only on the opening. (4) With the anode and cathode in contact as in (3), the solution was pressurized, and the liquid pressure of the solution applied pressure to the solid electrolyte membrane and, through the solid electrolyte membrane, to the aluminum substrate, stabilizing the pressure between the solid electrolyte membrane and the zinc underlayer on the surface of the aluminum substrate. The pressure was applied to improve the conformability of the solid electrolyte membrane in the anode to the substrate (including minute irregularities on the surface) and to ensure uniform contact between the substrate and the solid electrolyte membrane. (5) After stabilization for about 30 seconds to about 1 minute in (4), a voltage is applied to the anode using a power supply, and the power supply, anode, solution, solid electrolyte membrane, and aluminum substrate are electrically connected. The temperature is 55°C, and the current density is 48.8 mA / cm. 2 The power was turned on. (6) In (5), a nickel coating was deposited on the zinc underlayer of the aluminum substrate by applying a pressure of 1 MPa for 300 seconds.

[0059] Comparative Example 2 A nickel coating was deposited in the same manner as in Comparative Example 1, except that the pressure stabilization time in steps (4) and (5) was changed to about 5 seconds to about 10 seconds.

[0060] II-2.Results Figure 3 shows the relationship between the voltage application time and the inter-electrode potential in Example 1. Figure 4 shows the relationship between the voltage application time and the inter-electrode potential in Comparative Example 1. Figures 3 and 4 reveal that in Comparative Example 1, a potential difference occurs due to zinc corrosion before the voltage is applied to the anode.

[0061] FIG. 5 shows images (N=3) of the nickel coating plated on the zinc underlayer of the aluminum substrate in Example 1, observed with a digital microscope. FIG. 6 shows images (N=3) of the nickel coating plated on the zinc underlayer of the aluminum substrate in Comparative Example 1, observed with a digital microscope. FIG. 7 shows images (N=2) of the nickel coating plated on the zinc underlayer of the aluminum substrate in Comparative Example 2, observed with a digital microscope. From FIGS. 5 to 7, it was found that applying a voltage to the anode before contacting the solid electrolyte membrane with the aluminum substrate having the zinc underlayer as the cathode can stably coat the aluminum substrate with a uniform nickel coating. Furthermore, from FIGS. 6 and 7, it was found that even if a voltage is applied to the anode within 10 seconds of contacting the solid electrolyte membrane with the aluminum substrate having the zinc underlayer as the cathode, corrosion occurs in the zinc underlayer on the aluminum substrate surface, resulting in uneven deposition in the formed nickel coating.

[0062] As a result of the experiments described above, as shown in Figure 8, by changing the conventional process in which a solution containing metal ions is delivered and then an electric current is applied to form a film, to the process of the present invention in which a solution containing metal ions is delivered after a voltage is applied to the anode, and then an electric current is applied and a film is formed at the same time as the delivery, it is possible to stably form a metal coating with uniform film quality on the zinc underlayer of an aluminum substrate. [Explanation of symbols]

[0063] 1A film deposition equipment 11 Anode 12 Spare anode 13 Solid electrolyte membrane 16 Power supply section 20. Housing 21 Solution storage section 22 Opening 30A pressure section 40 Mounting table L Solution containing metal ions T Tank P pump B. Aluminum substrate (cathode) Ba: Surface of aluminum substrate (zinc underlayer) F Metallic film

Claims

1. a solution containing section for containing a solution containing metal ions and disposed between the anode and the cathode; a pressurizing section for pressurizing the solution in the solution containing section; a solid electrolyte membrane provided in the solution containing section, which is pressurized together with a surface of the cathode when the pressurizing section pressurizes the solution; and a power supply section for applying a voltage between the anode and / or the spare anode and the cathode, the spare anode is disposed in the solution storage section at a position such that the power supply section, the solution, the solid electrolyte membrane, and the cathode can be electrically connected to each other immediately after the solution is introduced into the solution storage section, the film-forming device introduces the solution while applying a voltage to the spare anode, thereby simultaneously establishing conduction between the power supply unit, the spare anode, the solid electrolyte membrane, the solution, and the cathode, thereby forming a metal film of the metal ions on the cathode; The film forming apparatus.

2. The film forming apparatus according to claim 1 , wherein the spare anode is disposed immediately above the solid electrolyte membrane below the solution containing portion.

3. 3. The film forming apparatus according to claim 1, wherein the solution contains nickel ions.

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