WO2025164402A1 - Plating composition and method for producing same - Google Patents

Abstract

Provided is a method for efficiently producing a plating composition usable for plating treatment from plating waste liquid. This method for producing a plating composition comprises: removing a portion of water from a first plating composition containing first metal ions and water via a separation membrane to obtain a first concentrated liquid; removing a portion of water from the first concentrated liquid under a low oxygen partial pressure environment to obtain a second concentrated liquid; introducing the second concentrated liquid into a working electrode chamber provided with a working electrode to reduce at least a portion of the first metal ions in the second concentrated liquid to metal, with the working electrode serving as a cathode, the working electrode chamber being separated from a counter electrode chamber provided with a counter electrode by at least one membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane; and oxidizing a metal of the same kind as the reduced metal into second metal ions having a lower oxidation number than the first metal ions, with the working electrode serving as an anode, to obtain a second plating composition containing the second metal ions and water.

Description

Plating composition and method of manufacturing the same

The present invention relates to a plating composition and a method for producing the same.

In relation to plating compositions used in metal plating, Japanese Patent Application Laid-Open No. 2003-213435 proposes a plating wastewater treatment system that consists of a wastewater storage tank for storing plating wastewater, an intermediate treatment device connected to the wastewater storage tank, a concentration and volume reduction device connected to the intermediate treatment device, and a recovery device for recovering concentrated fluid from the concentration and volume reduction device, and describes a method for concentrating plating wastewater under reduced pressure.

However, while the invention described in JP 2003-213435 A can concentrate and reduce the volume of plating wastewater, it cannot prevent the plating wastewater itself from being discharged. One aspect of the present invention aims to provide a method for efficiently producing a plating composition by efficiently reducing highly oxidized metal ions in plating wastewater to less oxidized metal ions.

A first aspect is a method for producing a plating composition, comprising: removing a portion of the water from the first plating composition containing first metal ions and water through a separation membrane to obtain a first concentrated solution; removing a portion of the water from the first concentrated solution in a low oxygen partial pressure environment to obtain a second concentrated solution; introducing the second concentrated solution into a working electrode chamber separated by a counter electrode chamber containing a counter electrode and at least one membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane and containing a working electrode, thereby reducing at least a portion of the first metal ions in the second concentrated solution to metal using the working electrode as the cathode; and oxidizing a metal of the same type as the reduced metal to a second metal ion having a lower oxidation number than the first metal ion using the working electrode as the anode to obtain a second plating composition containing the second metal ions and water.

The second aspect is a plating composition produced by the plating composition production method.

One aspect of the present invention provides a method for efficiently producing a plating composition by efficiently reducing highly oxidized metal ions in a plating wastewater solution to less oxidized metal ions.

1 is a flowchart showing an example of the order of steps in a method for producing a plating composition. 1A to 1C are schematic diagrams illustrating an example of a process for manufacturing an electronic component.

In this specification, the term "process" does not only refer to an independent process, but also includes processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. Furthermore, when multiple substances corresponding to each component are present in the composition, the content of each component in the composition refers to the total amount of those multiple substances present in the composition, unless otherwise specified. Furthermore, the upper and lower limits of the numerical ranges described in this specification can be arbitrarily selected and combined from the numerical values exemplified as numerical ranges. Below, embodiments of the present invention are described in detail. However, the embodiments described below are merely examples of plating compositions and methods for producing the same that embody the technical concept of the present invention, and the present invention is not limited to the plating compositions and methods for producing the same shown below.

A method for producing a plating composition includes a first concentration step of removing a portion of the water from a first plating composition containing first metal ions and water through a separation membrane to obtain a first concentrated solution, a second concentration step of removing a portion of the water from the first concentrated solution in a low-oxygen partial pressure environment to obtain a second concentrated solution, a first metal ion reduction step of introducing the second concentrated solution into a working electrode chamber separated by a counter electrode chamber containing a counter electrode and at least one diaphragm selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane and containing a working electrode, and reducing at least a portion of the first metal ions in the second concentrated solution to metal using the working electrode as a cathode, and a second metal ion oxidation step of oxidizing a metal similar to the reduced metal to a second metal ion having a lower oxidation number than the first metal ion using the working electrode as an anode to obtain a second plating composition containing the second metal ions and water. In one embodiment, the method for producing a plating composition may further include an impurity removal step of removing at least a portion of impurities from the first plating composition.

By removing a portion of the water from the first plating composition and concentrating it, the first metal ions can be reduced more efficiently by the metal. Furthermore, by removing water through a separation membrane, the first plating composition can be concentrated at high speed to obtain a first concentrated solution while suppressing oxidation of the metal ions. Furthermore, by removing water from the first concentrated solution in a low oxygen partial pressure environment, the oxidation of the low-oxidized metal ions contained in the first concentrated solution can be suppressed, while reducing the load on the reduction reaction in the first metal ion reduction step, allowing for more efficient production of the plating composition. The plating composition production method may also be a plating composition regeneration method that regenerates a plating composition (e.g., a second plating composition) that can be used in plating processing from a used plating composition or plating wastewater (e.g., a first plating composition).

One embodiment of a method for producing a plating composition will be described with reference to the drawings. Figure 1 is a flowchart showing an example of the process sequence of the method for producing a plating composition. The method for producing a plating composition may include an impurity removal step S101, a first concentration step S102, a second concentration step S103, a first metal ion reduction step S104, and a second metal ion oxidation step S105, which are included as necessary. In the impurity removal step S101, at least a portion of the impurities are removed from the first plating composition, which is the plating wastewater recovered from the plating tank or the water rinsing tank. In the first concentration step S102, a portion of the water is removed from the first plating composition after impurity removal through a separation membrane to obtain a first concentrated solution. In the second concentration step S103, a portion of the water is removed from the first concentrated solution in a low oxygen partial pressure environment to obtain a second concentrated solution. In the first metal ion reduction step S104, first metal ions (e.g., tin(IV) ions) with a high oxidation number (high oxidation state) contained in the second concentrated solution are reduced to a metal (e.g., metallic tin) using an electrochemical device. The electrochemical device is configured by separating a working electrode chamber containing a working electrode and a counter electrode chamber containing a counter electrode with a diaphragm. The first metal ions are reduced by introducing the second concentrated solution into the working electrode chamber and applying current to the working electrode as a cathode, resulting in metal deposition on the working electrode. In the second metal ion oxidation step S105, current is applied to a metal of the same type as the metal deposited on the working electrode as an anode, resulting in oxidization of the metal to second metal ions (e.g., tin(II) ions) with a low oxidation number (low oxidation state) and dissolving them in the second concentrated solution in the working electrode chamber, resulting in a second plating composition usable for plating processing.

In FIG. 1, the first concentration step S102 and the second concentration step S103 are performed after the impurity removal step S101, but the impurity removal step S101 may be performed after the first concentration step S102 or the second concentration step S103, and then the first metal ion reduction step S104 may be performed. Also, the impurity removal step S101 may not be performed.

Impurity Removal Step In the impurity removal step, at least some of the impurities are removed from a first plating composition containing first metal ions and water. The plating composition from which at least some of the impurities have been removed is concentrated by removing some of the water, and the first metal ions are then electrochemically reduced using an electrochemical device including a counter electrode chamber and a working electrode chamber separated by a membrane, such as an ion exchange membrane, that is impermeable to the first metal ions. This can be explained, for example, as follows: Removing at least some of the impurities contained in the first plating composition is thought to suppress inhibition of the reduction of the first metal ions due to interactions between the impurities and the cathode, thereby further improving the reduction efficiency of the first metal ions at the cathode. Furthermore, for example, it is thought that inhibition of reduction due to impurities adhering to or damaging the ion exchange membrane or the like is suppressed, thereby further improving the reduction efficiency of the first metal ions at the cathode. Furthermore, for example, it is thought that impurities clog or damage the separation membrane in the first concentration step, reducing the concentration efficiency. However, removing at least some of the impurities is thought to suppress this decrease in concentration efficiency.

The first plating composition may be, for example, plating wastewater used in metal plating, or plating wastewater obtained by rinsing a metal-plated article with water. The first plating composition may contain impurities. Impurities refer to substances that may inhibit the reduction of the first metal ions in the first metal ion reduction step described below, substances that may inhibit concentration in the first concentration step described below, etc. Specific examples of impurities include additives such as surfactants, leveling agents, brighteners, and antioxidants, metal components other than the first metal ions, dust, precipitates, etc.

The first plating composition may contain a surfactant as at least a portion of the impurities. The surfactant contained in the first plating composition may be any of a nonionic surfactant, a cationic surfactant, an anionic surfactant, an amphoteric surfactant, etc. The surfactant may also function as a brightener, leveler, etc. in the plating composition. From the viewpoint of the reduction efficiency of the first metal ion, the surfactant may contain at least one type selected from the group consisting of a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant. The first plating composition may contain only one type of surfactant, or a combination of two or more types.

Nonionic surfactants include, for example, ester surfactants in which a polyhydric alcohol such as glycerin, sorbitol, or sucrose is ester-bonded to a fatty acid; ether surfactants formed by adding ethylene oxide, propylene oxide, etc. to a compound having a hydroxyl group such as a higher alcohol or alkylphenol; and ester-ether surfactants formed by adding ethylene oxide, propylene oxide, etc. to an ester surfactant. Specific examples of nonionic surfactants include polyethylene glycol, polypropylene glycol, polyoxyethylene octylphenol, polyoxyethylene β-naphthyl ether, polyoxyethylene alkylamine, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, glycerin fatty acid ester and its ethylene oxide adduct, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid monoethanolamide and its ethylene oxide adduct, fatty acid N-methylmonoethanolamide and its ethylene oxide adduct, fatty acid diethanolamide and its ethylene oxide adduct, sucrose fatty acid ester, alkyl (poly)glycerin ether, polyglycerin fatty acid ester, polyethylene glycol fatty acid ester, fatty acid methyl ester ethoxylate, and N-long-chain alkyldimethylamine oxide. Nonionic surfactants may also have fluorine atoms substituted into their structures.

Examples of cationic surfactants include amine salts and quaternary ammonium salts. Specific examples of cationic surfactants include alkyl (or alkenyl) trimethyl ammonium salts, alkyl (or alkenyl) triethyl ammonium salts, dialkyl (or alkenyl) dimethyl ammonium salts, alkyl (or alkenyl) quaternary ammonium salts, mono- or dialkyl (or alkenyl) quaternary ammonium salts containing ether groups, ester groups, or amide groups, alkyl (or alkenyl) pyridinium salts, alkyl (or alkenyl) dimethyl benzyl ammonium salts, alkyl (or alkenyl) isoquinolinium salts, dialkyl (or alkenyl) morphonium salts, polyoxyethylene alkyl (or alkenyl) amines, alkyl (or alkenyl) amine salts, polyamine fatty acid derivatives, amyl alcohol fatty acid derivatives, benzalkonium chloride, and benzethonium chloride. Fluorine atoms may be substituted into the structure of these cationic surfactants.

Amphoteric surfactants exhibit the properties of anionic surfactants in the alkaline range and cationic surfactants in the acidic range. Examples of amphoteric surfactants include carboxylates and sulfonates, and may be either amino acid or betaine types. Specific examples of amphoteric surfactants include alkyldimethylaminoacetic acid betaine, alkyldimethylacetic acid betaine, alkyldimethylcarboxybetaine, alkyldimethylcarboxymethyleneammonium betaine, alkyldimethylammonioacetate, fatty acid amidopropyldimethylamino acid betaine, alkyloylamidopropyldimethylglycine, 2-alkyl-1-(2-hydroxyethyl)imidazolium-1-acetate, alkyldiaminoethylglycine, dialkyldiaminoethylglycine, and alkyldimethylamine oxide.

Anionic surfactants include carboxylates, sulfonates, sulfates, and phosphates.

If the first plating composition contains a surfactant, the surfactant content in the first plating composition may be, for example, 0.01 g/L or more and 10 g/L or less, and preferably 0.1 g/L or more or 5 g/L or less. The surfactant content in the plating composition after the impurities have been removed in the impurity removal step may be, for example, 0.005 g/L or more. The surfactant content can be measured using surface tension as an index. Specifically, it can be measured using a drop meter, surface tensiometer, etc.

The first metal ion contained in the first plating composition may be a metal ion in a more highly oxidized state than the second metal ion, or may be formed by the oxidation of the second metal ion constituting the plating composition prior to use. Examples of first metal ions include tin(IV) ions and iron(III) ions. The first metal ion contained in the first plating composition may be a simple metal ion or a complex ion. Examples of complexing agents that form complex ions include carboxylic acids including gluconic acid (including gluconolactone), citric acid, glutaric acid, succinic acid, malic acid, tartaric acid, lactic acid, and their salts or derivatives; phosphoric acids including tripolyphosphate, hydroxyethanediphosphonic acid, and their salts; sugars including sorbitol, mannitol, and their salts; amino acids including phenylalanine, glutamic acid, aspartic acid, alanine, glycine, and their salts; HEDTA, EDTA, etc. The complexing agent may contain at least one selected from the group consisting of these, and may contain at least gluconic acid. The complexing agents may be used alone or in combination of two or more. When the first metal ion is a complex ion, the pH of the plating composition used for plating can be set to a weakly acidic to weakly alkaline range, thereby suppressing corrosion of objects to be plated that are sensitive to strong acids or strong alkalis (for example, objects that use oxides as components, such as ceramic capacitors).

The content of the first metal ion in the first plating composition may be, for example, 0.1 g/L or more and 100 g/L or less, and preferably 1 g/L or more. The content of the complexing agent in the plating composition may be, for example, equimolar to 20 times the molar amount of the first metal ion, and preferably 10 times the molar amount. The content of the first metal ion in the plating composition is measured, for example, using inductively coupled plasma atomic emission spectroscopy (ICP-AES) or oxidation-reduction titration with potassium iodate after reduction with iron powder.

The first plating composition may contain a second metal ion in addition to the first metal ion. Specific examples of the second metal ion include tin(II) ions when the first metal ion is tin(IV) ions. Furthermore, specific examples of the second metal ion include iron(II) ions when the first metal ion is iron(III) ions. The second metal ion may be a simple metal ion or a complex ion. The complexing agent that forms the complex ion is the same as for the first metal ion. When the first plating composition contains a second metal ion, the content of the second metal ion contained in the first plating composition may be, for example, 100 g/L or less, and preferably 20 g/L or less. The content of the second metal ion contained in the plating composition is measured in the same manner as for the first metal ion.

The second metal ion that constitutes the plating composition before use may be derived from a water-soluble metal salt. Specific examples of water-soluble metal salts include sulfates, chlorides, boron fluorides, alkanesulfonates, alkanolsulfonates, and aromatic sulfonates. The composition may contain at least one selected from the group consisting of these, and may contain at least an alkane sulfonate. Examples of alkane sulfonic acids in alkane sulfonates include alkanesulfonic acids having 1 to 3 carbon atoms, such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and 2-propanesulfonic acid.

The first plating composition may further contain alkali metal ions, ammonium ions, etc. The inclusion of alkali metal ions, ammonium ions, etc. increases conductivity, suppresses heat generation due to solution resistance during electroplating, and tends to improve electrodeposition uniformity. Examples of alkali metal ions include lithium ions, sodium ions, potassium ions, rubidium, and cesium. Alkali metal ions, ammonium ions, etc. may be added to the first plating composition, for example, as a salt with an acid component. The inclusion of an acid component in the first plating composition, for example, further improves the stability of the first plating composition. Examples of acid components include sulfuric acid, hydrochloric acid, alkanesulfonic acid, alkanolsulfonic acid, aromatic sulfonic acid, phosphoric acid, alkylcarboxylic acid, and arylcarboxylic acid, and the first plating composition may contain at least one selected from the group consisting of these. These acids may be used alone or in combination of two or more.

The pH of the first plating composition may be, for example, 1 or more and 13 or less, preferably 3 or more or 4 or more, and preferably 11 or less or 9 or less. When the pH of the first plating composition is within this range, the first metal ions tend to be reduced more efficiently. The pH of the first plating composition may be adjusted to the desired range, for example, with a pH adjuster. Examples of pH adjusters include alkali metal hydroxides, ammonia, etc. in addition to the acid components described above.

The first plating composition may further contain an antioxidant. The inclusion of an antioxidant can, for example, improve the stability of the first plating composition and extend the bath life. Examples of antioxidants include hydroquinone, ascorbic acid, catechol, hypophosphorous acid, and erythorbic acid. When the first plating composition contains an antioxidant, the content of the antioxidant in the first plating composition may be, for example, 0.01 g/L or more and 20 g/L or less, and preferably 0.1 g/L or more or 5 g/L or less.

If the first plating composition contains an antioxidant, the impurity removal step may include removing at least a portion of the antioxidant. The antioxidant may be removed by activated carbon treatment.

The first plating composition contains water as a solvent. The total concentration of solutes in the first plating composition may be, for example, 150 g/L or less, preferably 100 g/L or less, or 80 g/L or less. The total concentration of solutes in the first plating composition may be, for example, 1 g/L or more.

Methods for removing impurities in the impurity removal step include, for example, thread-wound filter treatment, activated carbon treatment, microfiltration treatment, ultrafiltration treatment, and gel filtration treatment. The method for removing impurities in the impurity removal step may preferably include activated carbon treatment. A method for removing impurities using activated carbon treatment may, for example, include contacting the plating composition with activated carbon. By using activated carbon, at least a portion of the impurities can be more efficiently removed from the first plating composition. In the impurity removal step, a method for electrostatically adsorbing impurities (for example, a method for contacting with an ion exchange resin) may be combined with activated carbon treatment.

Activated carbon is a porous material whose main component is carbon and which has been subjected to a chemical or physical activation process. The activated carbon used in activated carbon treatment may be chemically activated or gas activated. Activated carbon may also be powdered activated carbon, granular activated carbon, or a combination of these.

The specific surface area of the activated carbon may be, for example, 200 m ² /g or more and 1500 ^{m 2} /g or less, preferably 300 m ² /g or more or 700 m ² /g or less. The specific surface area is measured based on the BET (Brunauer Emmett Teller) theory using nitrogen gas after pretreatment at 200°C for 6 hours. The average pore diameter of the activated carbon may be, for example, 1.5 nm or more and 3.5 nm or less, preferably 2.0 nm or more and 3.0 nm or less. The mesopore shape of the activated carbon may be, for example, such that the average pore width on the adsorption side measured by the INNES method is, for example, 2 nm or more and 30 nm or less, preferably 4 nm or more and 10 nm or less. The average pore width on the desorption side measured by the INNES method may be, for example, 2 nm or more and 5 nm or less, preferably 2 nm or more and 3.5 nm or less.

The amount of activated carbon used for contact with the first plating composition may be selected appropriately depending on the type of activated carbon. The amount of activated carbon used should be an amount that is sufficient to remove at least a portion of the impurities (e.g., surfactants) contained in the first plating composition, and is preferably an amount sufficient to remove 50% by mass or more, 70% by mass or more, or 90% by mass or more of the surfactants. The amount of activated carbon used may also be selected depending on the method of contact with the first plating composition. For example, when contacting in a single pass, a larger amount of activated carbon may be required than when contacting by circulating the first plating composition.

The first plating composition may be brought into contact with the activated carbon by, for example, mixing the first plating composition with the activated carbon followed by solid-liquid separation, or by passing the plating composition through activated carbon held in a filter, cartridge, or the like. The contact temperature between the first plating composition and the activated carbon may be, for example, 0°C or higher or 70°C or lower.

First Concentration Step In the first concentration step, a first concentrated solution is obtained by removing a portion of the water from a first plating composition containing first metal ions and water through a separation membrane. Generally, when concentrating a plating composition containing oxidizable metal ions by removing a portion of the water, the lower the metal ion concentration and the higher the temperature, the more likely the oxidation of the metal ions will proceed. By using a separation membrane to concentrate the first plating composition, the first plating composition can be concentrated quickly and in large quantities while suppressing the oxidation of the metal ions. The separation membrane may be a filtration membrane that can preferentially separate water from the first plating composition, and is preferably a filtration membrane that can selectively separate water.

In one embodiment, the separation membrane may be a filtration membrane known as a reverse osmosis membrane. A reverse osmosis membrane (hereinafter also referred to as an RO membrane) is a type of filtration membrane that allows water molecules to pass through while blocking substances other than water molecules, such as ions. A reverse osmosis membrane separates a solution A with a high salt concentration (e.g., a first plating composition) from a solution B with a low salt concentration (e.g., water). When a pressure greater than the difference in osmotic pressure between solutions A and B is applied to the side of solution A with a high salt concentration, only water molecules move from solution A to solution B. This removes a portion of the water from the first plating composition to obtain a first concentrated solution, and water can be obtained as reverse osmosis membrane-treated water.

Examples of materials for the separation membrane include polyamide, polysulfone, and cellulose acetate, and preferably polyamides including aromatic polyamides or crosslinked aromatic polyamides. To concentrate the first plating composition using a separation membrane, for example, a tubular module or a spiral module equipped with a separation membrane can be used.

The liquid feed pressure when concentrating the first plating composition using a separation membrane may be selected appropriately depending on the type of separation membrane used. The liquid feed pressure during concentration may be, for example, 0.1 MPa or more, and preferably 0.5 MPa or more, 1 MPa or more, or 2 MPa or more. The liquid feed pressure may be, for example, 10 MPa or less. The temperature during concentration may be, for example, 0°C or more and 50°C or less, and preferably 10°C or more and 40°C or less.

The first plating composition subjected to concentration using a separation membrane may be the first plating composition from which at least some of the impurities have been removed in the impurity removal step, or it may be the first plating composition from which the impurities have not been removed. Preferably, it may be the first plating composition from which at least some of the impurities have been removed in the impurity removal step.

The ratio of the volume of the first plating composition to the volume of the first concentrated solution from which some of the water has been removed via the separation membrane (concentration factor) may be, for example, 2 or more, and preferably 3 or more.

In the second concentration step, a portion of the water is removed from the first concentrate in a low-oxygen partial pressure environment to obtain a second concentrate. By removing a portion of the water from the first concentrate in a low-oxygen partial pressure environment, a second concentrate from which a portion of the water has been further removed can be obtained while effectively suppressing oxidation of metal ions contained in the first concentrate.

The low oxygen partial pressure environment in the second concentration step is an environment in which the oxygen partial pressure is lower than that of the atmosphere, and can be achieved by replacing the atmosphere with an inert gas, reducing the pressure, etc. Specifically, the oxygen partial pressure in the low oxygen partial pressure environment may be, for example, 10 kPa or less, and preferably 2 kPa or less, or 1 kPa or less.

The low oxygen partial pressure environment in the second concentration step can be achieved as an inert gas atmosphere by replacing the atmosphere with an inert gas. Examples of inert gases in the inert gas atmosphere include rare gases such as argon, and nitrogen gas. The concentration of the inert gas in the inert gas atmosphere may be, for example, 80% by volume or more, and preferably 90% by volume or more, 95% by volume or more, 98% by volume or more, or 99% by volume or more. The pressure in the inert gas atmosphere may be normal pressure or may be reduced below atmospheric pressure. An inert gas atmosphere under reduced pressure may be reduced after replacement with an inert gas, or an inert gas atmosphere may be created by supplying an inert gas when adjusting the degree of vacuum.

The low oxygen partial pressure environment in the second concentration step may be a low-pressure environment. A low-pressure environment may be an environment under reduced pressure lower than atmospheric pressure. Specifically, the air pressure in a low-pressure environment may be, for example, 50 hPa or less, and preferably 10 hPa or less, or 1 hPa or less.

In one embodiment, the second concentration step may be a step of removing a portion of the water from the first concentrated liquid in a low oxygen partial pressure environment to obtain a second concentrated liquid. The low oxygen partial pressure environment may be, for example, an oxygen partial pressure of 10 kPa or an oxygen concentration of 10% by volume or less, and preferably an oxygen partial pressure of 2 kPa or less or an oxygen concentration of 2% by volume or less, or an oxygen partial pressure of 1 kPa or less or an oxygen concentration of 1% by volume or less.

Methods for removing water in the second concentration step include a first concentration method in which a portion of the water is removed from the first concentrated liquid under reduced pressure, a second concentration method in which the first concentrated liquid is frozen and then a portion of the water is removed from the frozen first concentrated liquid under reduced pressure, and a third concentration method in which a mist containing water is generated from the first concentrated liquid under an inert gas atmosphere or reduced pressure and at least a portion of the generated mist is removed.

In the first concentration method, a portion of the water is removed from the first concentrated liquid under reduced pressure. The degree of vacuum in the first concentration method can be, for example, 500 hPa or less, preferably 200 hPa or less, or 100 hPa or less. The degree of vacuum can also be, for example, 1 hPa or more, or 100 hPa or more. In the first concentration method, a portion of the water can be removed while the first concentrated liquid is heated under reduced pressure. When the first concentrated liquid is heated, the temperature can be, for example, 30°C or more and 80°C or less, preferably 35°C or more or 38°C or more, and preferably 70°C or less or 60°C or less. In the first concentration method, the first concentrated liquid can also be stirred. The stirring method can be appropriately selected from commonly used stirring methods. Examples of stirring methods include a method of rotating a container containing the first concentrated liquid to stir, a method of stirring the first concentrated liquid in a container using a rotor or the like, and a method of pouring the first concentrated liquid into a container while spraying it. In the first concentration method, some of the water can be removed under an inert gas atmosphere by replacing the atmosphere inside the container with an inert gas before reducing the pressure.

The second concentration method includes freezing the first concentrated liquid and removing a portion of the water from the frozen first concentrated liquid under reduced pressure. The first concentrated liquid can be frozen by lowering the liquid temperature to, for example, -15°C or below, preferably -25°C or below. It is preferable to replace the atmosphere inside the container with an inert gas before freezing. In the second concentration method, the container containing the frozen first concentrated liquid is depressurized, and a portion of the water contained in the first concentrated liquid is removed by freeze-drying, which sublimes the solid state. The degree of vacuum in the second concentration method may be, for example, 10 hPa or below, preferably 1 hPa or below. The second concentration method can be performed using, for example, a freeze dryer. The second concentration method allows water to be removed at low temperatures under highly reduced pressure, thereby more effectively suppressing the oxidation of metal ions. In the second concentration method, the container can be purged with an inert gas before depressurizing, thereby removing a portion of the water under an inert gas atmosphere.

The third concentration method involves generating a mist containing water from the first concentrated liquid (hereinafter also referred to as "atomization") and removing at least a portion of the generated mist. One method for generating a mist containing water from the first concentrated liquid is ultrasonic atomization, in which ultrasonic vibrations are applied to the first concentrated liquid. Ultrasonic atomization is a phenomenon in which, when ultrasonic vibrations are applied to a liquid, the vibrations create a fountain-like liquid column on the liquid surface, and fine droplets (mist), mainly measuring a few microns, are generated from the sides of the liquid column. By using ultrasonic atomization to turn a liquid into mist without heating it, substances can be separated at the molecular cluster level. Separation of substances by ultrasonic atomization is possible, for example, by taking advantage of the fact that molecules of the same substance tend to cluster in liquid, and the fact that clusters vary in size depending on the substance. The third concentration method can be performed, for example, using an atomization separation device (e.g., manufactured by NanoMist Technologies, Inc.).

Specifically, a portion of the water can be removed from the first concentrated liquid as follows. Ultrasonic vibrations are applied to the first concentrated liquid to generate a mist consisting of water clusters and a mist containing water and other components contained in the first concentrated liquid. A classification device such as a cyclone is used to separate the generated mist, with the "light mist" consisting of water clusters rising and the "heavy mist" containing components other than water falling. The light mist, consisting of water, is liquefied by condensation through cooling or other means and removed from the first concentrated liquid. Meanwhile, the heavy mist is allowed to fall under its own weight and be liquefied, allowing it to be recovered. In the third concentration method, ultrasonic atomization is performed in an inert gas atmosphere, and an inert gas is used in the airflow used in the cyclone, thereby removing a portion of the water in an inert gas atmosphere. According to the third concentration method, a portion of the water can be removed in an inert gas atmosphere without heating the first concentrated liquid, thereby more effectively suppressing the oxidation of metal ions.

In the third concentration method, ultrasonic atomization may be performed while heating the first concentrated liquid. When ultrasonic atomization is performed while heating, the liquid temperature of the first concentrated liquid may be, for example, 20°C or higher and 80°C or lower, preferably 20°C or higher or 30°C or higher, and preferably 70°C or lower.

The total concentration of solutes in the second concentrated liquid obtained by removing a portion of the water from the first concentrated liquid may be, for example, 30 g/L or more, and preferably 50 g/L or more, or 80 g/L or more. The total concentration of solutes in the second concentrated liquid may be, for example, 500 g/L or less. In the first concentration step, the ratio of the volume of the first concentrated liquid to the volume of the second concentrated liquid (concentration factor) may be, for example, 2 or more and 20 or less, and preferably 3 or more, or 10 or less. By controlling the concentration factor of the first concentrated liquid in the first concentration step within the above range, the first metal ions can be reduced more efficiently in the first metal ion reduction step.

First Metal Ion Reduction Step In the first metal ion reduction step, the first metal ions contained in the second concentrated solution are reduced using the working electrode of the electrochemical device as the cathode to obtain a metal element formed by the reduction of the first metal ions. The first metal ion reduction step may be performed using an electrochemical device including a working electrode chamber having a working electrode and a counter electrode chamber having a counter electrode, the working electrode chamber and the counter electrode chamber being separated by at least one diaphragm selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane. The second concentrated solution is introduced into the working electrode chamber of the electrochemical device. An aqueous solution containing conductive ions may be placed in the counter electrode chamber of the electrochemical device. Placing the aqueous solution containing conductive ions in the counter electrode chamber enables more efficient reduction of the first metal ions.

Examples of materials for the working electrode provided in the working electrode chamber include gold, platinum, platinum-coated titanium, silver, nickel, graphite, tin, titanium, iridium oxide, and ruthenium oxide. Examples of materials for the counter electrode include platinum, platinum-coated titanium, gold, nickel, iridium oxide, ruthenium oxide, titanium, graphite, and palladium. The working electrode chamber and the counter electrode chamber are separated, for example, by an ion exchange membrane. This allows for more efficient reduction of the first metal ion. The ion exchange membrane may be a cation exchange membrane, an anion exchange membrane, or a combination of both. The ion exchange membrane can be appropriately selected from commercially available ion exchange membranes. The ion exchange membrane may include at least a cation exchange membrane from the perspective of the reduction efficiency of the first metal ion. For example, the cation exchange membrane may include a fluororesin copolymer based on sulfonated tetrafluoroethylene. In addition, instead of an ion exchange membrane, a membrane that is difficult for the first metal ions to pass through, such as a reverse osmosis membrane (RO membrane) or a nanofiltration membrane (NF membrane, loose RO membrane), may be used.

When a conductive ion-containing aqueous solution is placed in the counter electrode chamber, the conductive ion-containing aqueous solution may contain at least water and a water-soluble metal salt. The water-soluble metal salt may contain metal ions such as alkali metal ions and alkaline earth metal ions. The water-soluble metal salt may also contain anions such as sulfate ions, nitrate ions, and phosphate ions.

In the first metal ion reduction step, at least a portion of the first metal ions in the second concentrate introduced into the working electrode chamber are reduced to elemental metals by a first electrolysis process using the working electrode as a cathode. The elemental metals produced by the reduction may be deposited on the working electrode, for example. The current density in the electrolysis of the first metal ions may be appropriately selected depending on the type of first metal ions. The current density may be, for example, 0.05 A/dm2 or ^more and 10 A/dm2 or less, and preferably 0.1 A/ ^dm2 or ^more or 5 A/dm2 or ^less . The temperature in the electrolysis may be, for example, 20°C or more and 80°C or less, and preferably 30°C or more or 75°C or less. The time required for the electrolysis may be, for example, 10 minutes to 200 hours.

Second Metal Ion Oxidation Step In the second metal ion oxidation step, a metal of the same type as the metal produced by reduction in the first metal ion reduction step is oxidized to second metal ions by a second electrolysis process using the working electrode as the anode. In the second metal ion oxidation step, a metal of the same type as the metal deposited on the working electrode in the first metal ion reduction step may be oxidized to second metal ions by electrolysis using the working electrode as the anode. The second metal ion oxidation step may be performed using the same electrochemical device subsequent to the reduction of the first metal ions in the first metal ion reduction step. That is, the metal deposited on the working electrode in the first metal ion reduction step may be oxidized to second metal ions by electrolysis using the working electrode as the anode.

The current density in the electrolysis of a metal may be appropriately selected depending on the type of metal. The current density may be, for example, 0.5 A/dm2 or ^more and 100 A/dm2 or ^less . The temperature in the electrolysis of a metal may be, for example, 10°C or more and 80°C or less, preferably 15°C or more or 75°C or less. The time required for the electrolysis may be, for example, 0.2 hours or more and 10 hours or less.

If the method for producing a plating composition includes an impurity removal step and the removed impurities include a surfactant, the method for producing a plating composition may further include a step of adding a surfactant to the second plating composition obtained in the second metal ion oxidation step. By performing a plating process using a plating composition to which a surfactant has been added, a plating having a better surface is formed. The surfactant added may be the same type as the surfactant removed in the impurity removal step. Furthermore, the amount of surfactant added may be approximately the same as the amount of surfactant removed in the impurity removal step.

The method for producing a plating composition according to this embodiment may be used in combination with a plating method or a method for producing electronic components that includes a plating step. By using the method for producing a plating composition in combination, it is possible to reduce the discharge of plating wastewater in the plating method or the method for producing electronic components.

Plating Method The plating method includes a plating composition production step and a plating step of contacting an object to be plated with a plating solution containing at least a portion of the plating composition obtained in the production step to form a plating layer on the surface of the object to be plated. The plating composition production step is the same as the plating composition production method described above. By using a plating solution containing the plating composition obtained by the plating composition production method described above, a plating layer of excellent quality equivalent to that formed when a plating solution prepared immediately before use is used can be formed on the object to be plated.

In the plating process, a plating solution is brought into contact with the object to be plated to form a plating layer on the surface of the object to be plated. The plating layer may be, for example, a tin plating layer. The plating process may be electrolytic plating or electroless plating, preferably electrolytic plating. The plating solution may be a commonly used tin plating solution, except that it contains at least a portion of the plating composition produced in the manufacturing process. The plating solution may be composed of, for example, tin (II) ions, a surfactant, a complexing agent, etc. In addition to the plating composition produced, the plating solution may further contain surfactants, etc. that may be removed in the manufacturing process, as needed.

There are no particular restrictions on the object to be plated to which the plating method can be applied, as long as it is an item on whose surface a plating layer can be formed. Examples of objects to be plated include ceramic bodies with a conductive layer on their surface, composite bodies containing resin and metal magnetic powder, substrates, and electrodes attached to base materials.

The thickness of the plating layer formed in the plating process is not particularly limited and may be selected appropriately depending on the purpose, etc. The thickness of the plating layer may be, for example, 0.01 μm or more and 100 μm or less, preferably 0.1 μm or more and 50 μm or less, more preferably 0.3 μm or more and 10 μm or less, for example, 0.3 μm or more and 3 μm or less, or 1 μm or more and 5 μm or less.

The plating process can be carried out using known plating methods, such as barrel plating, centrifugal plating, and rack plating.

2. Method for Manufacturing Electronic Components The method for manufacturing electronic components includes a step of manufacturing a plating composition, and a step of contacting a substrate having a conductive layer on its surface with a plating solution containing at least a portion of the plating composition obtained in the manufacturing step, to form an electrode layer including a plating layer on the surface of the conductive layer. The manufacturing step of the plating composition is the same as in the manufacturing method of the plating composition described above. By using a plating solution containing the plating composition obtained by the manufacturing method of the plating composition described above, it is possible to form external electrodes including an electrode layer of excellent quality equivalent to that obtained by using a plating solution prepared just before use, and it is possible to manufacture highly reliable electronic components.

For details of electronic components manufactured using the electronic component manufacturing method, please refer to, for example, JP 2021-027195 A, WO 2023/171394, WO 2020/218218 (the disclosures of these documents are incorporated herein by reference in their entirety).

In the electrode formation process, a plating solution is brought into contact with an element having a conductive layer on its surface to form an electrode layer including a plating layer. The plating method in the electrode formation process may be electrolytic plating or electroless plating, and preferably electrolytic plating. The plating solution may be a commonly used plating solution, except that it contains at least a portion of the plating composition obtained in the plating composition production process. The plating solution may be composed of, for example, tin (II) ions, a surfactant, a complexing agent, etc. In addition to the produced plating composition, the plating solution may further contain, as necessary, surfactants and the like that may be removed in the production process.

The element body subjected to the electrode formation process may be the component body of an electronic component. The component body is not particularly limited, and may be, for example, a multilayer ceramic capacitor, an inductor, a resistor, an LC composite component, a thermistor, etc. In one embodiment, the component body may be a multilayer ceramic capacitor. The component body may be constructed using a method commonly used depending on the type of component body. The material of the component body is not particularly limited, and may be a material commonly used depending on the type of component body. Examples of materials include ceramic, resin, metal, and composites of these. In one embodiment, the material of the component body may be ceramic.

The thickness of the plating layer included in the electrode layer formed in the electrode formation process is not particularly limited and may be selected appropriately depending on the purpose, etc. The thickness of the electrode layer may be, for example, 0.01 μm or more and 100 μm or less, preferably 0.1 μm or more and 50 μm or less, more preferably 0.3 μm or more and 10 μm or less, for example, 0.3 μm or more and 3 μm or less, or 1 μm or more and 5 μm or less.

The electrode formation process can be performed using known plating methods, such as barrel plating, centrifugal plating, and rack plating.

An example of the steps included in a method for manufacturing electronic components will be described with reference to the drawings. Figure 2 is a schematic diagram showing part of the steps of a method for manufacturing electronic components, which is one aspect of this embodiment. In this method for manufacturing electronic components, element bodies having a conductive layer on their surface are introduced into a tin plating tank 10 using an introduction means 12, and an electrode layer including a tin plating layer is formed on the conductive layer of the element body introduced into the tin plating tank 10. Water evaporates 16 from the tin plating tank 10. Next, the element bodies with the electrode layer formed thereon are pumped out of the tin plating tank by an extraction means 14 into a water rinsing tank 20 using a pump. The water rinsing tank 20 may be, for example, a countercurrent multi-stage water rinsing tank. The element bodies are pumped downstream of the countercurrent multi-stage water rinsing tank and move upstream. The element bodies with the electrode layer formed thereon are separated from the countercurrent multi-stage water rinsing tank in the most upstream tank by a separation means 24. The element bodies with the separated electrode layer formed thereon are subjected to a drying process. In the countercurrent multi-stage rinsing tank (20), water is supplied from the upstream side by a water supply means 22, and the rinsing water moves downstream. The rinsing water (first plating composition) 26 extracted from the most downstream tank is introduced into the plating composition manufacturing apparatus 30.

In the plating composition manufacturing apparatus 30, at least some impurities (e.g., surfactants) are removed from the tin-containing wash water using an impurity removal means 32 that uses activated carbon. A first concentrator 36 using a separation membrane removes some of the water from the wash water, yielding a first concentrated solution. The water 36a removed from the wash water is supplied to the wash tank 20 as reclaimed water 26. The first concentrated solution, from which some of the water has been removed via the separation membrane, is further removed by a second concentrator 37 in a low-oxygen partial pressure environment, yielding a second concentrated solution. The water 37a removed from the second concentrated solution is supplied to the wash tank 20 as reclaimed water 26, along with the water 36a removed from the wash water. The second concentrated solution is introduced into an electrochemical device 34 that includes a working electrode chamber and a counter electrode chamber separated by a membrane. The second concentrated solution may contain tin(IV) ions as the first metal ions and may further contain tin(II) ions as the second metal ions. In the electrochemical device 34, at least a portion of the tin(IV) ions in the rinse water are reduced to metallic tin using the working electrode as the cathode. If the second concentrate contains tin(II) ions, at least a portion of the tin(II) ions in the second concentrate may be reduced to metallic tin using the working electrode as the cathode. Next, at least a portion of the reduced metallic tin or the tin substrate is oxidized to tin(II) ions using the working electrode as the anode to produce a second plating composition 38 that can be reused in plating processes. The produced second plating composition 36 is optionally supplemented with additives such as surfactants and introduced into the tin plating tank 10 for reuse. According to one aspect of this embodiment, tin-containing rinse water that would previously have been discarded can be reused as a regenerated plating composition, contributing to waste reduction.

The invention according to the present disclosure may include, for example, the following aspects.
[1] A method for producing a plating composition, comprising: removing at least a portion of impurities from a first plating composition containing first metal ions and water; removing a portion of the water from the first plating composition through a separation membrane to obtain a first concentrated solution; removing a portion of the water from the first concentrated solution in a low oxygen partial pressure environment to obtain a second concentrated solution; introducing the second concentrated solution into a working electrode chamber separated by a counter electrode chamber having a counter electrode and at least one membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane and having a working electrode, and reducing at least a portion of the first metal ions in the second concentrated solution to metal using the working electrode as a cathode; and oxidizing a metal similar to the reduced metal to a second metal ion having a lower oxidation number than the first metal ion using the working electrode as an anode to obtain a second plating composition containing the second metal ions and water.

[2] The manufacturing method described in [1], wherein the first plating composition further contains a surfactant.

[3] The manufacturing method described in [2], further comprising removing at least a portion of the surfactant from the first plating composition.

[4] The manufacturing method described in any one of [1] to [3], wherein the separation membrane includes a reverse osmosis membrane.

[5] The manufacturing method described in any one of [1] to [4], wherein obtaining the second concentrated liquid includes removing a portion of the water from the first concentrated liquid under reduced pressure.

[6] The manufacturing method described in any one of [1] to [5], wherein obtaining the second concentrated liquid includes freezing the first concentrated liquid and removing a portion of the water from the frozen first concentrated liquid under reduced pressure.

[7] A manufacturing method according to any one of [1] to [4], wherein obtaining the second concentrated liquid includes generating a mist containing water from the first concentrated liquid and removing at least a portion of the generated mist.

[8] The manufacturing method described in any one of [1] to [7], wherein the first plating composition has a total solute concentration of 150 g/L or less.

[9] The manufacturing method described in any one of [1] to [8], wherein the second concentrated solution has a total solute concentration of 30 g/L or more.

[10] The manufacturing method described in any one of [1] to [9], wherein the first metal ions include tin(IV) ions and the second metal ions include tin(II) ions.

[11] A plating composition obtained by the manufacturing method described in any one of [1] to [10].

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

Preparation of Plating Composition A plating composition having the composition shown below was prepared using purified water, potassium stannate (IV) as a tin (IV) ion source, tin (II) methanesulfonate as a tin (II) ion source, gluconic acid, a cationic surfactant containing decyltrimethylammonium chloride, hydroquinone, and sodium methanesulfonate.

Composition Tin (IV) ion: 0.16 mol/L
Tin (II) ion: 0.04 mol/L
Gluconic acid: 0.8 mol/L
Methanesulfonic acid: 1.2 mol/L
Surfactant: 1 g/L
Hydroquinone: 1g/L
Sodium ion: 1.4 mol/L

Example 1
The plating composition prepared above was diluted 30 times with purified water to prepare a first plating composition, which was then passed through an activated carbon filter (FCC-S, manufactured by Nippon Filter Co., Ltd.) at a feed pressure of 0.1 MPa to remove the surfactant and obtain a filtered solution. The filtered solution was then passed through a reverse osmosis membrane (RO membrane; DRA991C, manufactured by Daisen Membrane Systems Co., Ltd.) at a feed pressure of 2 MPa to remove a portion of the water and concentrate the solution, thereby obtaining a first concentrated solution concentrated to a concentration of approximately 1/5 of the target concentration. The resulting first concentrated solution was then purged with nitrogen gas and then concentrated using a rotary evaporator (N-2110, manufactured by Tokyo Rikakikai Co., Ltd.) under a nitrogen atmosphere at 100 hPa, 60°C, and 60 rpm to obtain a second concentrated solution with component concentrations equal to those of the prepared plating composition.

Metallic tin was reductively deposited from the second concentrated solution as follows. An electrochemical device was prepared, equipped with a Pt plate as the working electrode and a Pt/Ti mesh plate as the counter electrode, with the working electrode chamber and the counter electrode chamber separated by a cation exchange membrane (Nafion ^™ 424). The second concentrated solution was introduced into the working electrode chamber of the electrochemical device, and a methanesulfonic acid solution was introduced into the counter electrode chamber. A reduction reaction of tin ions was carried out at a current density of 1 A/ ^dm² , with the working electrode as the cathode and the counter electrode as the anode. The solution temperature was kept at 65°C or lower. Next, an oxidation reaction of the deposited metallic tin was carried out at a current density of 1 A/ ^dm² , with the working electrode as the anode and the counter electrode as the cathode, to obtain a second plating composition.

After confirming the components of the resulting second plating composition through analysis, it was confirmed that it could be reused as a tin plating solution by adding any missing components in the plating composition.

Comparative Example 1
A second concentrated liquid was obtained in the same manner as in Example 1, except that the first concentrated liquid was concentrated in the air.

Evaluation of Tin(II) Ion Concentration The tin(II) ion concentrations of the second concentrated solutions obtained in Example 1 and Comparative Example 1 were evaluated as follows. The results are shown in Table 1. The first plating composition before concentration was designated Reference Example 0, a sample that was left for 8 hours at room temperature (27°C) in a nitrogen atmosphere without being concentrated using a rotary evaporator was designated Reference Example 1, and a sample that was left for 8 hours at room temperature (27°C) in an air atmosphere without being concentrated using a rotary evaporator was designated Reference Example 2. Table 1 shows the relative concentrations, with the tin(II) ion concentration in Reference Example 0 set to 100%.

The concentrations of tin(IV) ions and tin(II) ions were evaluated using a combination of redox titration and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Specifically, the redox titration was performed using starch as an indicator in 2M hydrochloric acid with an iodine standard solution to calculate the concentration of tin(II) ions. Additionally, the total concentration of tin ions was calculated using ICP-AES, and the concentration of tin(IV) ions was calculated by subtracting the concentration of tin(II) ions.

Table 1 shows that concentrating under a nitrogen atmosphere suppresses the oxidation of tin(II) ions.

Example 2
Instead of concentration using a rotary evaporator, a freeze dryer (freeze dryer FDU-1110 manufactured by Tokyo Rikakikai Co., Ltd.) was used to carry out concentration as follows: 1500 mL of the first concentrate was placed in a container, frozen in a freezer set to -30°C, and set in the freeze dryer. The freeze dryer was set to -40°C and the degree of vacuum was 10 Pa. The atmosphere inside the device was replaced with nitrogen before reducing the pressure. After processing in the freeze dryer for about one day, the concentrate was concentrated to 300 mL.

The tin(II) ion concentration in the second concentrate after concentration by freeze-drying was five times that of the first concentrate before concentration. Considering the concentration ratio, it is believed that there was no oxidation of tin(II) ions during freeze-drying.

Example 3
Instead of concentration using a rotary evaporator, concentration was carried out using an atomization separation device (NanoMist Technologies Inc., USA-L5 atomization separation device) that removes water by misting using ultrasonic vibrations, as follows. 1500 mL of the first concentrated liquid was placed in a container connected to the device. The inside of the device was purged with nitrogen gas to replace the nitrogen atmosphere. The bath was heated to a liquid temperature of 60°C, and the liquid was concentrated to 300 mL by treating for approximately 8 hours.

The tin (II) ion concentration in the second concentrate after concentration using the atomization separation device was five times that of the first concentrate before concentration. Considering the concentration ratio, it is believed that there was no oxidation of tin (II) ions in the atomization separation device.

The disclosure of Japanese Patent Application No. 2024-012029 (filing date: January 30, 2024) is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims (11)

removing a portion of the water from a first plating composition containing first metal ions and water through a separation membrane to obtain a first concentrated solution;
removing a portion of the water from the first concentrated solution in a low oxygen partial pressure environment to obtain a second concentrated solution;
introducing the second concentrated solution into a counter electrode chamber having a counter electrode and a working electrode chamber having a working electrode, the counter electrode chamber being separated by at least one membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane, and reducing at least a portion of the first metal ions in the second concentrated solution to a metal using the working electrode as a cathode;
oxidizing a metal of the same type as the reduced metal to a second metal ion having a lower oxidation number than the first metal ion, using the working electrode as an anode, to obtain a second plating composition containing the second metal ion and water. The manufacturing method described in claim 1, wherein the first plating composition further contains a surfactant. The manufacturing method described in claim 2, further comprising removing at least a portion of the surfactant from the first plating composition. The manufacturing method described in any one of claims 1 to 3, wherein the separation membrane comprises a reverse osmosis membrane. The manufacturing method described in any one of claims 1 to 4, wherein obtaining the second concentrated liquid includes removing a portion of the water from the first concentrated liquid by vaporizing the water under reduced pressure. The manufacturing method described in any one of claims 1 to 5, wherein obtaining the second concentrated liquid includes freezing the first concentrated liquid and removing a portion of the water from the frozen first concentrated liquid under reduced pressure. The manufacturing method described in any one of claims 1 to 4, wherein obtaining the second concentrated liquid includes generating a mist containing water from the first concentrated liquid and removing at least a portion of the generated mist. The manufacturing method described in any one of claims 1 to 7, wherein the first plating composition has a total solute concentration of 150 g/L or less. The manufacturing method described in any one of claims 1 to 8, wherein the second concentrated solution has a total solute concentration of 30 g/L or more. The manufacturing method described in any one of claims 1 to 9, wherein the first metal ions include tin(IV) ions and the second metal ions include tin(II) ions. A plating composition obtained by the manufacturing method described in any one of claims 1 to 10.