Method for producing copper foil from copper electrolytic deposition

Abstract

The invention relates to a method for producing copper foils by electrolytic deposition of copper metal on a rotating drum cathode and, in particular, a member for dissolving copper to be deposited in said method. In the method, copper is electrolytically deposited on a rotating drum cathode, which is partially immersed in an electrolyte solution contained in a plating bath; stripping the deposited copper layer from the part, which is not immersed in the electrolyte solution, of the drum cathode to obtain the copper foil; using an insoluble anode as a counter electrode of the drum cathode; the electrolyte solution contains copper ions, an organic additive and a Fe < 2 + > / Fe < 3 + > redox system; maintaining the concentration of copper ions in the electrolyte solution to be constant by passing the electrolyte solution through a copper dissolving unit; in the copper dissolving unit, the electrolyte solution is in contact with an auxiliary anode and an auxiliary cathode; introducing copper metal and an oxygen-containing gas into the copper dissolution unit; the auxiliary anode is in contact with the copper metal; the oxygen-containing gas contacts the surface of the copper metal; the copper metal is continuously dissolved in the electrolyte solution by oxidation of the Fe < 3 + > component through the Fe < 2 + > / Fe < 3 + > redox system.

Description

Technical Field

[0001] The present invention relates to a method for producing copper foil by electrolytically depositing copper metal on a rotating drum cathode and, in particular, to means for dissolving the copper to be deposited in said method. Background Art

[0002] It is known to produce copper foil by a continuous process in which copper is electrolytically deposited (plated) on a rotating drum cathode that is partially immersed in an electrolyte solution contained in a plating tank, the copper layer deposited on the drum cathode being stripped from the portion of the drum cathode not immersed in the electrolyte solution to obtain copper foil, and an insoluble anode is used as a counter electrode to the drum cathode. This process is described, for example, in US 2002 / 0064019 A1, which relates to cathode electrode materials and a rotating cathode drum for electrolytic copper foil production. US Pat. No. 11,050,050 B1 also shows a continuous process for producing copper foil on a rotating drum cathode immersed in an electrolyte solution contained in a plating tank.

[0003] In this process, the electrolyte solution usually contains copper sulfate, sulfuric acid, chloride and organic compounds. The current density is 50 to 80A / dm 2 The treatment time at 50° C. is about 60 seconds. The drum speed varies between 7 m / min (copper foil for lithium batteries) and 25 m / min (copper foil for printed circuit boards). Copper foils produced in this way can have lengths of several kilometers.

[0004] In this process, a MOX-coated titanium anode is typically used as an insoluble anode. During plating, oxygen forms at the anode surface and turns the electrolyte into a milky blue solution. Oxygen bubbles can cause plating defects and damage the anode.

[0005] The copper deposited from the electrolyte solution onto the drum cathode needs to be continuously replaced in order to keep the copper concentration in the electrolyte solution constant.

[0006] In a conventional process this is done by drawing off the electrolyte from the plating tank and transferring it to a copper dissolution tank as shown in Figure 1. The two tanks on the left hand side are copper dissolution tanks (sometimes up to 250,000 1 of electrolyte) where the solution is heated to a maximum of 80°C and air is blown into the electrolyte to enable / enhance dissolution of the copper metal.

[0007] Since oxygen is generated at the anode, the solution is heated to 80°C and air is blown into the dissolution tank, the organic compounds contained in the electrolyte solution are destroyed and there are unidentified organic compounds that need to be removed. Therefore, the third tank (about 5,000l) from the left (to the right of the two solution tanks) is responsible for processing the destroyed organic matter. Here, activated carbon is mixed into the solution. The activated carbon then absorbs the organic compounds and is subsequently removed by filtration. The spent activated carbon must then be disposed of. After filtering the activated carbon from the copper solution, the electrolyte is stored in another tank. Here, the electrolyte is cooled to about 50°C and the missing organic electrolyte compounds are added before the solution is transferred back to the plating tank of the equipment containing the drum cathode and the device for stripping the copper foil.

[0008] US 2001 / 0042686 A1 relates to the use of copper ions to replenish copper electrolyte in a copper dissolution tower and the use of filtering equipment to remove undesirably formed impurities from the used electrolyte generated during copper foil production.

[0009] WO 95 / 18251 A1 describes a process and an apparatus for the electrolytic deposition of metal layers, in particular copper layers, wherein an insoluble anode is used for the electrolytic deposition of a uniform metal layer having defined physical and mechanical properties. In the process, a redox system (comprising, for example, Fe 2+ / Fe 3+ ) is added to the deposition solution and reacts at an insoluble anode during deposition. The resulting compound extracts new metal ions from a portion of the vessel containing the metal to be deposited, replacing the metal ions deposited from the solution. The additive compound is (largely) not destroyed in the process. EP 0 862 665 B1 also describes a process and apparatus for the electrolytic deposition of copper layers using a redox system and a copper dissolution unit.

[0010] WO 01 / 68953 A1 describes a process and apparatus for regulating the concentration of metal ions in an electrolyte for electrolytic metal deposition, the electrolyte containing an additional substance of an electrochemically reversible redox system. According to this process, at least a portion of the electrolyte is passed through an auxiliary cell comprising an insoluble auxiliary anode and at least one auxiliary cathode, between which an electric current is generated by applying a voltage. Excess oxidized material from the redox system is thus reduced at the auxiliary cathode, and the formation of ions of the metal to be deposited is avoided. According to this process, a sheet of the metal to be deposited is used as the auxiliary cathode.

[0011] The above conventional method of manufacturing copper foil is disadvantageous in that it consumes a large amount of energy, it consumes a large amount of activated carbon (which, when discarded, needs to be disposed of as industrial waste), and the apparatus is relatively complicated and thus requires a lot of maintenance work.

[0012] It is therefore an object of the present invention to provide a continuous process for producing copper foil in which copper is electrolytically deposited on a rotating drum cathode, which process avoids the disadvantages of the prior art, in particular consumes relatively low amounts of energy and does not require large amounts of activated carbon, while providing a large amount of copper ions to be deposited and which can be carried out with the aid of relatively simple equipment requiring reduced maintenance. Summary of the Invention

[0013] The present invention relates to a continuous process for producing copper foil by electrolytically depositing copper metal on a rotating drum cathode and, in particular, to a means for dissolving the copper to be deposited in the process; the process consumes a small amount of energy and does not require a large amount of activated carbon and can be implemented with the aid of relatively simple equipment requiring reduced maintenance. In the process, copper is electrolytically deposited on a rotating drum cathode that is partially immersed in an electrolyte solution contained in a plating tank; the copper layer deposited on the drum cathode is stripped from the portion of the drum cathode that is not immersed in the electrolyte solution to obtain copper foil; an insoluble anode is used as a counter electrode to the drum cathode; the electrolyte solution contains copper ions, an organic additive, and Fe 2+ / Fe 3+ The invention relates to a redox system; the concentration of copper ions in the electrolyte solution is maintained constant by passing the electrolyte solution through a copper dissolution unit; in the copper dissolution unit, the electrolyte solution is in contact with an auxiliary anode and an auxiliary cathode; copper metal and an oxygen-containing gas are introduced into the copper dissolution unit; the auxiliary anode is in contact with the copper metal; the oxygen-containing gas is introduced so that its bubbles contact the surface of the copper metal; the copper metal is dissolved in the electrolyte solution by the Fe 2+ / Fe 3+ Fe redox system 3+ The components and, if appropriate, the oxygen contained in the oxygen-containing gas are oxidized, causing copper metal to continuously dissolve in the electrolyte solution.

[0014] The object of the present invention is achieved by the method as described in Technical Solution 1; its preferred embodiments are defined in the accompanying technical solutions.

[0015] In the method according to the invention, a relatively large amount of copper is removed from the electrolyte solution per unit time due to deposition on the drum cathode. For example, when a drum having a diameter of 2.0 m and a width of 1.5 m and half thereof (i.e. 4.7 m) is drawn off, 2 When the drum cathode having a surface of 100 nm is immersed in the electrolyte and the current density at the drum cathode is 65 A / dm 2 In addition, at a relatively high rotation speed of typically 7 m / min, a large amount of electrolyte solution (typically 100 ml / m 2 ).

[0016] To maintain a constant copper ion concentration in the electrolyte solution, fresh copper metal is continuously dissolved in the electrolyte solution by passing the electrolyte solution through a dissolution unit into which copper metal is introduced.

[0017] Copper metal in the form of copper scrap can be introduced into the dissolution unit. The copper metal (e.g. scrap) can be placed in a basket made of an inert metal (e.g. titanium). The basket then serves as an auxiliary anode.

[0018] Through Fe 2+ / Fe 3+ Fe redox system 3+ The copper metal is continuously dissolved in the electrolyte solution by oxidation of the components. This dissolution process is described by the following chemical equation:

[0019] Cu 0 +2Fe 3+ →Cu 2+ +2Fe 2+

[0020] Mainly by oxidation of Fe at the insoluble anode of the counter electrode used as drum cathode in the plating tank 2+ To generate Fe 3+ .

[0021] An oxygen-containing gas (e.g., air) is introduced into the dissolution cell so that its bubbles contact the surface of the copper metal, for example by bubbling the oxygen-containing gas into the dissolution cell at a position below a basket containing the copper metal in the form of copper scrap to generate appropriate gas agitation around the surface of the copper metal.

[0022] This has two effects. First, the disturbance at the copper metal surface is increased, so the dissolution reaction rate is accelerated. Second, the oxygen from the oxygen-containing gas acts as an additional oxidant (in addition to the anodic potential of the auxiliary anode in contact with the copper metal) to further oxidize the Fe 2+ Cheng Fe 3+ , which then dissolves additional copper metal.

[0023] However, excess Fe should be avoided 3+ (which does not react with the copper metal and which is then transferred to the plating tank) due to the Fe 3+ Therefore, after passing through the copper metal in the copper dissolution unit, all Fe 3+ should be converted into Fe 2+ .

[0024] To ensure this result, the copper metal in the dissolution cell (e.g., copper scrap) is in electrical contact with an auxiliary anode. As the cathode potential becomes higher during copper deposition, the anode potential increases during copper dissolution. When leaving the dissolution cell, the electrolyte solution passes through the auxiliary cathode (i.e., a metal device (e.g., a mesh) with a positive potential); this potential must be lower than the positive potential of the copper deposited in the dissolution tank. Both the copper metal at a negative potential and the auxiliary cathode with a positive potential will eliminate any existing Fe 3+ ions. The current efficiency at the drum cathode will therefore remain close to 100%.

[0025] The dissolution reaction of the copper metal is accelerated by both (i) the anode potential of the copper metal introduced into the dissolution cell and (ii) the gas agitation created by introducing oxygen-containing gas so that its bubbles contact the surface of the copper metal. Thus, the copper concentration in the electrolyte solution can be effectively controlled and thus maintained within the narrow and high concentration range required for efficient and consistent copper deposition on the drum cathode by (i) controlling the potential applied to the auxiliary anode (i.e., the voltage between the auxiliary anode and the auxiliary cathode) and (ii) to a lesser extent by controlling the intensity of the gas agitation.

[0026] In the method of the present invention, the electrolyte solution contains Fe 2+ / Fe 3+ Redox system (i.e. combination of ferrous and ferric compounds). Mainly by oxidizing Fe at the insoluble anode in the plating tank. 2+ To generate Fe 3+ ions and, after its transfer to the dissolution unit, then act as an oxidant to oxidize copper metal to Cu 2+ And thus dissolves copper metal in the electrolyte solution.

[0027] Thus, there is a continuous process in which the Fe 3+ The copper metal is oxidized and then transferred to the plating tank and reduced to copper metal at the drum cathode. At the same time, Fe 3+ Reduction to Fe 2+ Moreover, in Fe 2+ After being transferred to the plating tank, it is reoxidized to Fe 3+ .

[0028] Compared with the conventional process for manufacturing copper foil, the use of Fe 2+ / Fe 3+ Redox systems offer the following advantages as a means of dissolving copper metal in large quantities (required in the copper foil manufacturing process) and in a well-controlled manner:

[0029] First, at the insoluble anode, Fe 2+ Oxidized to Fe 3+The oxygen release at the anode and the organic additive combustion competition and therefore suppress the oxygen release at the anode and the organic additive combustion.Therefore, the consumption of organic additive (and the generation of polluting decomposition product subsequently) is only due to the copper deposition process at the drum cathode.Therefore, the total organic content (TOC) of electrolyte solution keeps lower and prolongs the plating bath life-span.In addition, owing to having avoided the oxygen at the anode to produce, the life-span of anode is greatly increased.

[0030] Second, due to the Fe 2+ Oxidized to Fe 3+ And Fe 3+ It is an efficient oxidant for copper metal, so there is no need to increase the temperature of the electrolyte solution for copper dissolution to about 80°C (which is necessary in the conventional process for manufacturing copper foil). 3+ Together with the oxygen-containing gas introduced into the dissolution unit, it will act as an oxidant and dissolve the copper metal.The temperature can be maintained at about 50°C, which is the same as the temperature in the plating tank.

[0031] Third, as smaller amounts of organic compounds are destroyed, the use of activated carbon to remove decomposition products becomes redundant.

[0032] Fourth, there is no need for a separate step of recooling the electrolyte solution to about 50° C. Based on a simple on-line analysis, only the organic compounds consumed during copper deposition need to be replenished.

[0033] Fifth, add Fe 2+ / Fe 3+ Will achieve 50A / dm 2 The voltage required for the current density is reduced by more than 25% because no oxygen bubbles are formed at the insoluble anode. For example, in one experiment, 20g / lFe 2+ Add to contain 60g / lCu 2+ 、150g / lH2SO4、40mg / lCl - , 3ml / l conventional brightener, 11ml / l conventional carrier and 5ml / l conventional leveler plating solution; 2+ After that the battery voltage dropped from 3.2V to 2.4V. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a diagrammatic depiction of an apparatus for manufacturing copper foil by a conventional process (prior art).

[0035] Figure 2 is a diagrammatic representation of an apparatus for making copper foil by the process of the present invention. DETAILED DESCRIPTION

[0036] In the continuous process for making copper foil of the present invention, copper is electrolytically deposited on a rotating drum cathode partially immersed in an electrolyte solution containing copper ions, organic additives and Fe 2+ / Fe 3+ Redox system. Figure 2 The invention is illustrated using the apparatus shown therein which can be used with the process of the invention. Figure 2 The device in the embodiment can be regarded as an example. The device does not necessarily limit the process of the present invention.

[0037] As the electrolyte solution, preferably an aqueous acidic copper plating bath is used. Such baths are known from the prior art (for example from EP 0 690 934 A1). The basic composition of the electrolyte solution bath can vary within relatively large limits. In general, an aqueous solution of the following composition is used: copper ions: 5-65 g / L (e.g., copper sulfate (CuSO4.5H2O): 20-250 g / L, preferably 80-140 g / L or 180-220 g / L); concentrated sulfuric acid: 50-350 g / L, preferably 180-280 g / L or 50-90 g / L; iron(II) ions: 3-40 g / L (e.g., iron sulfate (FeSO4.7×H2O): 15-200 g / L, preferably 15-150 g / L, more preferably 20-120 g / L or 50-100 g / L); chloride ions (e.g., added in the form of NaCl): 0.01-0.18 g / L, preferably 0.03-0.1 g / L. Other copper salts can be used, at least partially, instead of copper sulfate. Sulfuric acid may even be partially or completely replaced by fluoroboric acid, methanesulfonic acid or other acids. In other words, the electrolyte solution may contain no or substantially no sulphuric acid and / or sulphate salts. In particular, the electrolyte solution may contain methanesulfonic acid and its iron and / or copper salts.

[0038] Chloride ions are added in the form of alkali chlorides (eg sodium chloride) or in the form of hydrochloric acid. If the feed already contains halide ions, the addition of sodium chloride can be completely or partially omitted.

[0039] The electrolyte solution contains Fe 2+ / Fe 3+ Redox system. Preferably, the electrolyte solution Fe 2+ / Fe 3+ The total concentration of Fe ions is 3-40 g / L, preferably 3-30 g / L, more preferably 4-24 g / L or 10-20 g / L. 2+ / Fe 3+The redox system can be formed from iron(II) sulfate heptahydrate. This is particularly suitable for regenerating copper ions in aqueous acidic copper baths. However, other water-soluble iron salts (e.g., iron salts of methanesulfonic acid and iron(III) sulfate nonahydrate) can also be used, provided that the salts do not contain non-biodegradable (hard) complexing agents in the compound, as these can cause problems during waste disposal (e.g., ferric ammonium sulfate).

[0040] The organic additives contained in the electrolyte solution include, in particular, at least one brightener (preferably an organic sulfur-containing compound), at least one leveler (preferably a nitrogen-containing compound) and at least one carrier. 2+ ions), Fe 2+ ions, acids, chloride ions, brighteners, levelers and carriers.

[0041] The organic sulfur-containing compound as the brightener compound is preferably one or more compounds selected from the group consisting of organic mercaptans, sulfides, disulfides and polysulfides, preferably selected from the group consisting of 3-(benzothiazolyl-2-thio)-propanesulfonic acid, 3-mercaptopropane-1-sulfonic acid, ethylenedisulfidedipropylsulfonic acid, bis-(p-sulfophenyl)-disulfide, bis-(ω-sulfobutyl)-disulfide, bis-(ω-sulfohydroxypropyl)-disulfide, bis-(ω-sulfobutyl)-disulfide In some embodiments, the brightener compounds include methyl-(ω-sulfopropyl)-disulfide, bis-(ω-sulfopropyl)-sulfide, methyl-(ω-sulfopropyl)-disulfide, methyl-(ω-sulfopropyl)-trisulfide, O-ethyl-dithiocarbonic acid S-(ω-sulfopropyl) ester, thioglycolic acid, thiophosphate O-ethyl-bis-(ω-sulfopropyl) ester, 3-N,N-dimethylaminodithiocarbamoyl-1-propylsulfonic acid, 3,3'-thio-bis(1-propylsulfonic acid), thiophosphate tris-(ω-sulfopropyl)-ester and their corresponding salts. The concentration of all brightener compounds (total) present in the electrolyte solution is preferably in the range of 0.01 mg / l to 100 mg / l, more preferably 0.05 mg / l to 10 mg / l, and still more preferably 0.1 to 5 mg / l.

[0042] The nitrogen-containing compound as the leveler compound is preferably one or more compounds selected from the group consisting of urea-based polymers, polyethyleneimine, alkoxylated polyethyleneimine, alkoxylated lactams and polymers thereof, diethylenetriamine and hexamethylenetetramine, peptides with polyethyleneimine, amino acids with polyethyleneimine, peptides with polyvinyl alcohol, amino acids with polyvinyl alcohol, peptides with polyalkylene glycol, amino acids with polyalkylene glycol, pyrroles with aminoalkylene groups, pyridines with aminoalkylene groups, organic dyes (e.g., Janus Green B, Bismarck Brown Y, and Acid Violet 7), sulfur-containing amino acids (e.g., cysteine), and phenazinium salts. The concentration of the leveler compound (total) added to the electrolyte solution is in the range of 0.5 mg / l to 400 mg / l, preferably 0.1 mg / l to 100 mg / l.

[0043] The oxygen-containing compound as the carrier compound is preferably selected from one or more compounds in the group consisting of polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, polypropylene glycol, stearic acid polyglycol ester, alkoxylated naphthol, oleic acid polyglycol ester, stearyl alcohol polyglycol ether, nonylphenol polyglycol ether, octanol polyalkylene glycol ether, octanol-bis-(polyalkylene glycol ether), poly(ethylene glycol-random-propylene glycol), poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), and poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol). The concentration of the carrier compound (total) added to the electrolyte solution is in the range of 0.005 g / l to 20 g / l, more preferably 0.01 g / l to 20 g / l, and even more preferably 0.01 g / l to 5 g / l.

[0044] The process of the present invention can be implemented in an apparatus such as Figure 2 The apparatus shown in FIG. 1 comprises a plating device 1 having a plating tank (having an electrolyte solution 4 and a rotating drum cathode 3), a stripping device 2, and a Cu dissolving unit 5. In the process for producing copper foil of the present invention, copper is electrolytically deposited on a rotating drum cathode 3, which is partially immersed in the electrolyte solution 4 contained in the plating tank. The drum cathode typically has a diameter of 0.5 to 4.0 m, preferably 1.5 to 2.5 m. The drum cathode typically has a width of 0.5 to 3.0 m, preferably 1.0 to 2.0 m. The current density at the drum cathode is typically 20 to 100 A / dm 2 , preferably 30 to 80A / sm 2 , more preferably 40 to 70 A / dm 2The rotation speed of the drum cathode is generally 1 to 15 m / min, preferably 5 to 10 m / min. The amount of copper deposited on the drum cathode is generally 10 to 50 kg / min, preferably 30 to 40 kg / min. The thickness of the copper foil produced by the process of the present invention is generally 2 to 30 μm, preferably 5 to 20 μm, and more preferably 7 to 12 μm.

[0045] In the process of the present invention for making copper foil, an insoluble anode is used as the counter electrode to the drum cathode. The current density at the insoluble anode is typically >20 A / dm 2 .

[0046] In the process for making copper foil of the present invention, copper is electrolytically deposited on a rotating drum cathode, typically at a temperature of 15 to 70°C, preferably 25 to 60°C, more preferably 40 to 50°C.

[0047] In the process for producing copper foil of the present invention, the concentration of copper ions in the electrolyte solution is maintained constant by passing the electrolyte solution through the copper dissolution unit. Therefore, the concentration of copper ions in the electrolyte solution present in the plating tank is typically 80 to 90 g / l.

[0048] In other words, a portion of the electrolyte solution present in the plating tank is continuously or periodically withdrawn from the plating tank and transferred to the dissolution unit.

[0049] Preferably, this operation is performed so that the auxiliary cathode 6 in the form of a cathode mesh is located closer to the auxiliary anode 7 in the form of an anode mesh. Figure 2 A portion of the electrolyte solution withdrawn from the plating tank is introduced into the Cu (copper) dissolution unit 5, whereby the withdrawn portion first contacts the auxiliary cathode. During copper dissolution in the Cu dissolution unit 5, copper deposits, particularly in the form of copper dendrites, can be observed on the cathode surface of the auxiliary cathode without the need for copper plating.

[0050] Fe is a portion of the electrolyte solution drawn from the plating tank and introduced into the copper dissolution unit. 3+ The ion concentration is higher than that of Fe 3+ ion concentration. In other words, the 3+ The concentration of ions is relatively low (low Fe 3+ Solution 9) and Fe 2+ Compared with the electrolyte solution in which the ions are at a relatively high concentration, a portion of the electrolyte solution extracted from the plating tank contains a relatively high concentration of Fe 3+ ions (Fe-rich 3+ Solution 8) and relatively low concentrations of Fe 2+ ions. Preferably, Fe 3+The concentration of ions is less than 30% of the total iron ion concentration, preferably less than 25% of the total iron ion concentration or preferably in the range of 0.25-25% of the total iron ion concentration.

[0051] For example: In the experiment explained at the beginning of the article, 20g / lFe 2+ ions are added to the electrolyte plating solution. When the electrolyte plating solution is generated, Fe 3+ The concentration of ions is zero, where Fe 2+ / Fe 3+ Fe redox system 2+ / Fe 3+ The total iron ion concentration of the ions is therefore 20 g / L. During the plating process in the plating tank and during the dissolution of Cu in the Cu dissolution unit, Fe 2+ ions and Fe 3+ The concentration of ions changes while the total concentration remains constant. If the Fe 3+ The concentration of Fe ions is 3-12 g / L and the Fe 3+ With a concentration of 0.5-5 g / L of ions, good results are achieved with regard to the plating quality of the produced copper foil, time and energy consumption for copper deposition and dissolution.

[0052] By reducing the Fe 3+ The ion-assisted cathode 6 slightly increases the Fe content in the extracted electrolyte solution. 2+ The concentration of ions helps reduce the burning of organic additives at the anode in the Cu dissolution unit 5. The potential is adjusted to avoid copper deposition at the cathode mesh 6.

[0053] In the Cu dissolution unit, Fe 3+ The ions promote the oxidation of copper metal (which therefore dissolves) and thus its reduction to Fe 2+ ions. Therefore, after passing through the Cu dissolution unit, the electrolyte solution contains a relatively low concentration of Fe 3+ ions and relatively high concentrations of Fe 2+ ions (Fe-rich 2+ Solution 9).

[0054] In the copper dissolution cell 5, the electrolyte solution 4 is in contact with an auxiliary anode 7 and an auxiliary cathode 6. A voltage is applied between the auxiliary anode and the auxiliary cathode. This voltage is typically 1 to 9 V, preferably 2 to 4 V. The auxiliary anode is in contact with copper metal 10. The application of this voltage and the copper metal in contact with the auxiliary anode promote the dissolution of the copper metal introduced into the dissolution cell, allowing a relatively large amount of copper to be dissolved per unit time. This dissolution is further promoted by introducing an oxygen-containing gas into the Cu dissolution cell so that its bubbles 11 contact the surface of the copper metal. The oxygen-containing gas can be air, preferably air, and more preferably hot air bubbles. The air can be introduced by a blower 12.

[0055] In accordance with Figure 2 In one embodiment, the Cu dissolution unit 5 includes an additional auxiliary cathode in the form of an additional cathode mesh close to the location where the electrolyte solution leaves the Cu dissolution unit (not shown) to further reduce Fe 3+ ion concentration. This voltage is usually likewise 1 to 9 V, preferably 2 to 4 V. The voltage of the additional auxiliary cathode is preferably lower than the voltage of the auxiliary cathode (6), preferably at most 50% lower.

[0056] In the process of dissolving copper metal in the Cu dissolution unit, the electrolyte solution in the Cu dissolution unit is generally at a temperature of 15 to 70° C., preferably 25 to 60° C., more preferably 40 to 50° C. Preferably, the temperature of the electrolyte solution is the same as the temperature in the plating tank and the Cu dissolution unit.

[0057] The auxiliary cathode and anode may be made of any kind of electrically conductive and dimensionally stable material.The size of the dissolution unit is not particularly limited and may be adapted to the requirements of the process for producing the copper foil, in particular the amount of copper foil to be produced per unit time.

Claims

1. A continuous process for producing copper foil, wherein electrolytically depositing copper on a rotating drum cathode (3) which is partially immersed in an electrolyte solution (4) contained in a plating tank; peeling off the copper layer deposited on the drum cathode (3) from the portion of the drum cathode (3) not immersed in the electrolyte solution (4) to obtain the copper foil; using an insoluble anode as a counter electrode to the drum cathode (3); The electrolyte solution (4) contains copper ions, organic additives and Fe 2+ / Fe 3+ Redox systems; maintaining a constant concentration of copper ions in the electrolyte solution (4) by passing the electrolyte solution (4) through a copper dissolution unit (5); In the copper dissolution unit (5), the electrolyte solution (4) is in contact with an auxiliary anode (7) and an auxiliary cathode (6); introducing copper metal and oxygen-containing gas into the copper dissolution unit (5); The auxiliary anode (7) is in contact with the copper metal; introducing the oxygen-containing gas so that its bubbles (11) contact the surface of the copper metal; By the Fe 2+ / Fe 3+ Fe redox system 3+ The copper metal is continuously dissolved in the electrolyte solution (4) by oxidizing the oxygen contained in the oxygen-containing gas and the oxygen contained in the oxygen-containing gas as appropriate.

2. The method according to claim 1, wherein the organic additive contained in the electrolyte solution comprises at least one organic sulfur-containing compound as a brightener, at least one nitrogen-containing compound as a leveler, and at least one oxygen-containing compound as a carrier.

3. The method according to claim 1, wherein the electrolyte solution contains 20-250 g / l copper sulfate pentahydrate, 50-350 g / l sulfuric acid, 15-200 g / l iron (II) sulfate heptahydrate, 0.01-0.18 g / l chloride ions.

4. The method according to claim 1, wherein the electrolyte solution contains methanesulfonic acid and its iron and / or copper salts.

5. The method of any one of claims 1, 2 or 4, wherein the electrolyte solution is substantially free of sulfuric acid and / or sulfate salts.

6. The method of claim 2, wherein the total concentration of brightener compounds present in the electrolyte solution is 0.01 mg / l to 100 mg / l.

7. The method of claim 2, wherein the total concentration of the leveler compounds present in the electrolyte solution is 0.5 mg / l to 400 mg / l.

8. The method of claim 2, wherein the total concentration of the carrier compound present in the electrolyte solution is 0.005 g / l to 20 g / l.

9. The method according to claim 1 , wherein the current density at the drum cathode is 20 to 100 A / dm 2 .

10. A method according to any one of the preceding claims, wherein the amount of copper deposited on the drum cathode is from 10 to 50 kg / min.

11. A method according to any one of the preceding claims, wherein copper is deposited on the rotating drum cathode at a temperature of 15 to 70°C.

12. The method according to any one of the preceding claims, wherein the concentration of copper ions in the electrolyte solution present in the plating tank is 80 to 90 g / l.

13. The method according to any one of the preceding claims, wherein a portion of the electrolyte solution withdrawn from the plating tank is introduced into the copper dissolving unit (5) at a position closer to the auxiliary cathode (6) than the auxiliary anode (7) so that the withdrawn portion first contacts the auxiliary cathode (6).

14. The method according to any one of the preceding claims, wherein a portion of the electrolyte solution withdrawn from the plating tank is introduced into the copper dissolution unit (5), the Fe 3+ The ion concentration is higher than that of Fe 3+ The concentration of ions.

15. The method according to any of the preceding claims, wherein the voltage applied between the auxiliary anode (7) and the auxiliary cathode (6) is 1 to 9 V.

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