Method for producing copper foil by electrolytic deposition of copper

Abstract

The present invention relates to a method for producing copper foil on a rotating drum cathode by electrolytic deposition of copper metal, and more particularly to a means for dissolving the copper deposited during the process. In this method, copper is electrolytically deposited on a rotating drum cathode partially immersed in an electrolyte solution contained in a plating bath; the deposited copper layer is peeled off from the portion of the drum cathode not immersed in the electrolyte solution to obtain a copper foil; an insoluble anode is used as a counter electrode for the drum cathode; the electrolyte solution contains copper ions, organic additives, and Fe. 2+ / Fe 3+ The electrolyte solution contains an oxidation-reduction 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 contacts an auxiliary anode and an auxiliary cathode; copper metal and an oxygen-containing gas are introduced into the copper dissolution unit; the auxiliary anode contacts the copper metal; the oxygen-containing gas contacts the surface of the copper metal; the copper metal is converted into Fe 2+ / Fe 3+ Fe in redox systems 3+ It is oxidized by the components and subsequently dissolves in the electrolyte solution.

Description

[Technical Field]

[0001] The present invention relates to a method for producing copper foil on a rotating drum cathode by electrolytic deposition of copper metal, and in particular to a means for dissolving the copper deposited during the process. [Background technology]

[0002] It is known to produce copper foil by a continuous method, in which copper is electrolytically deposited (plated) on a rotating drum cathode partially immersed in an electrolyte solution contained in a plating bath, the copper layer deposited on the drum cathode is peeled off from the portion of the cathode not immersed in the electrolyte solution to obtain a copper foil, and an insoluble anode is used as a counter electrode for the drum cathode. Such a method is described, for example, in US 2002 / 0064019 A1, which relates to a cathode electrode material and a rotating cathode drum for producing electrolytic copper foil. US 11,050,050 B1 also shows a continuous method for producing copper foil on a rotating drum cathode immersed in an electrolyte solution contained in a plating bath.

[0003] In such a method, the electrolyte solution typically contains copper sulfate, sulfuric acid, chlorides, and organic compounds. The current density is 50-80 A / dm 2 The processing time is approximately 60 seconds at 50°C. The drum speed varies between 7 m / min (for copper foils for lithium batteries) and 25 m / min (for copper foils for printed circuit boards). The copper foils produced in this way can have lengths of several kilometers.

[0004] In these processes, MOX-coated titanium anodes are typically used as inert anodes. During plating, oxygen is generated on the anode surface, turning the electrolyte into a milky blue solution. Oxygen bubbles can cause plating defects and damage the anode.

[0005] Copper deposited on the drum cathode from the electrolyte solution must be continually replaced to maintain a constant copper concentration in the electrolyte solution.

[0006] Traditionally, this is done by withdrawing the electrolyte from the plating tank and transferring it to a copper dissolving tank, as shown in Figure 1. The two tanks on the left are copper dissolving tanks (which can be up to 250,000 L of electrolyte), where the solution is heated to 80°C and air is bubbled through the electrolyte to allow / accelerate dissolution of the copper metal.

[0007] Due to oxygen generation at the anode, heating of the solution to 80°C, and blowing air into the dissolution tank, the organic compounds contained in the electrolyte solution are destroyed, resulting in the presence of undefined organic compounds that must be removed. Therefore, the third tank from the left (approximately 5,000 L) (to the right of the two solution tanks) processes the destroyed organic matter. Here, activated carbon is mixed into the solution. The activated carbon then absorbs the organic compounds, which are subsequently removed by filtration. The used activated carbon must then be discarded. After filtering the activated carbon from the copper solution, the electrolyte is stored in another tank. Here, the electrolyte is cooled to approximately 50°C, and missing organic electrolyte compounds are added before the solution is returned to the plating tank of the equipment, which contains the drum cathode and the copper foil stripping device.

[0008] US 2001 / 0042686 A1 relates to replenishing copper ions to a copper electrolyte in a copper dissolving tower and removing unwanted formed impurities produced during the production of copper foil from the spent electrolyte using a filtration device.

[0009] WO 95 / 18251 A1 describes a method and an apparatus for the electrolytic deposition of metal layers, in which an insoluble anode is used for the electrolytic deposition of uniform metal layers, in particular copper layers, with defined physical-mechanical properties. 2+ / Fe 3+A compound of a redox system containing is added to the deposition solution and reacts at an insoluble anode during deposition. The resulting compound draws new metal ions from a portion of the reservoir containing the metal to be deposited to replace those deposited from the solution. In this way, the additive compound is not destroyed (to a greater extent). EP 0 862 665 B1 also describes a method 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 method and an apparatus for adjusting the metal ion concentration in an electrolyte for electrolytic deposition of metals, the electrolyte containing an additional substance of an electrochemically reversible redox system. According to this method, 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 a current is generated by applying a voltage. The excess amount of oxidized material from the redox system is thus reduced at the auxiliary cathode, preventing the formation of ions of the metal to be deposited. According to this method, a piece of the metal to be deposited is used as the auxiliary cathode.

[0011] The above-mentioned conventional methods for producing copper foil are disadvantageous in that they consume a large amount of energy, consume a large amount of activated carbon which, if used, must be disposed of as industrial waste, and the equipment is relatively complicated and therefore requires a large amount of maintenance. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] US 2002 / 0064019 A1 [Patent Document 2] US 11,050,050 B1 [Patent Document 3] US 2001 / 0042686 A1 [Patent Document 4] WO 95 / 18251 A1 [Patent Document 5] EP 0 862 665 B1 [Patent Document 6] WO 01 / 68953 A1 [Patent Document 7] EP 0 690 934 A1 Summary of the Invention [Problem to be solved by the invention]

[0013] It is therefore an object of the present invention to provide a continuous process for the production of copper foil, in which copper is electrolytically deposited on a rotating drum cathode, which process avoids the drawbacks of the prior art, in particular, it consumes lower amounts of energy, does not consume significant amounts of activated carbon, and can be carried out with relatively simple equipment requiring reduced maintenance while providing a large amount of copper ions to be deposited. [Means for solving the problem]

[0014] The present invention relates to a continuous method for producing copper foil on a rotating drum cathode by electrolytic deposition of copper metal, and more particularly to a means for dissolving the copper deposited during the process; the method requires low energy consumption, does not consume significant amounts of activated carbon, and can be carried out with relatively simple equipment requiring reduced maintenance. In this method, copper is electrolytically deposited on a rotating drum cathode partially immersed in an electrolyte solution contained in a plating bath; the copper layer deposited on the drum cathode is stripped from the portion of the drum cathode not immersed in the electrolyte solution to obtain a copper foil; an insoluble anode is used as a counter electrode for the drum cathode; the electrolyte solution contains copper ions, organic additives, and Fe. 2+ / Fe 3+ The electrolyte solution contains an oxidation-reduction 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 contacts an auxiliary anode and an auxiliary cathode; copper metal and an oxygen-containing gas are introduced into the copper dissolution unit; the auxiliary anode contacts the copper metal; the oxygen-containing gas is introduced so that its bubbles contact the surface of the copper metal; the copper metal is converted into Fe 2+ / Fe3+ Fe in redox systems 3+ The components and optionally the oxygen contained in the oxygen-containing gas are oxidized and thereby continuously dissolved in the electrolyte solution.

[0015] The object of the invention is achieved by a method according to claim 1; preferred embodiments thereof are defined in the dependent claims.

[0016] 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 and withdrawal onto the drum cathode. For example, if the drum cathode has a diameter of 2.0 m and a width of 1.5 m, half of that, i.e., 4.7 m, 2 The surface of the drum cathode is immersed in the electrolyte, and the current density at the drum cathode is 65 A / dm 2 , approximately 35.5 kg of copper is deposited per minute; moreover, at relatively high rotation speeds, typically 7 m / min, a significant amount of electrolyte solution is drawn out of the plating bath due to adhesion to the drum cathode (typically 100 mL / m 2 ).

[0017] To maintain a constant copper ion concentration in the electrolyte solution, the electrolyte solution passes through a dissolution unit and copper metal is introduced into the dissolution unit so that new copper metal is continuously dissolved in the electrolyte solution.

[0018] Copper metal may be introduced into the melting unit in the form of copper scrap. The copper metal (e.g., scrap) may be placed in a basket made of an inert metal, such as titanium. The basket then acts as an auxiliary anode.

[0019] Copper metal is Fe 2+ / Fe 3+ Fe in redox systems 3+ It dissolves continuously in the electrolyte solution by being oxidized by the components. This dissolution process is represented by the following chemical equation: Cu 0 +2Fe 3+ →Cu 2+ +2Fe 2+ This is explained by:

[0020] Fe 3+ is the Fe insoluble anode used as the counter electrode to the drum cathode in the plating bath. 2+ It is mainly produced by the oxidation of

[0021] An oxygen-containing gas, such as air, is introduced into the melting unit, for example, by bubbling the oxygen-containing gas into the melting unit so that the bubbles contact the surface of the copper metal, creating moderate gas agitation around the surface of the copper metal at a location below a basket containing the copper metal in the form of copper scrap.

[0022] This has two effects. First, it increases turbulence at the copper metal surface, thereby increasing the rate of the dissolution reaction. Second, 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), increasing the rate of dissolution of the Fe 2+ Fe 3+ and then dissolves additional copper metal.

[0023] However, excess Fe that does not react with copper metal and is then transferred to the plating bath 3+ The formation of Fe in contact with the drum cathode 3+ must be avoided because it reduces the copper deposition efficiency. 3+ After copper metal passes through the copper melting unit, Fe 2+ must be converted to

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

[0025] Both (i) the anodic potential of the copper metal introduced into the dissolution unit and (ii) the gas agitation generated by introducing an oxygen-containing gas and contacting its bubbles with the surface of the copper metal enhance the rate of the copper metal dissolution reaction. Thus, 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, controlling the intensity of the gas agitation, the copper concentration in the electrolyte solution can be effectively controlled and thereby maintained within the narrow, high concentration range required for efficient and consistent deposition of copper onto the drum cathode.

[0026] In the method according to the invention, the electrolyte solution contains Fe 2+ / Fe 3+ Contains a redox system, i.e., a combination of ferrous and ferric compounds. Fe 3+ The ions are transferred to the insoluble anode in the plating bath. 2+ After being transported to the melting unit, copper metal is then converted to Cu 2+ The copper acts as an oxidizing agent to oxidize the copper metal, thereby dissolving it in the electrolyte solution.

[0027] Therefore, copper metal is dissolved in the melting unit. 3+ and then transferred to a plating bath where it is reduced again to copper metal at a drum cathode, while simultaneously 3+ is the Fe by copper metal, similar to the auxiliary cathode in the melting unit. 2+ is reduced to Fe 2+ After being transferred to the plating tank, Fe 2+ Fe again 3+ There are continuous methods by which hydroxybenzoates can be oxidized to

[0028] Fe as a means of dissolving the large amounts of copper metal required for the copper foil manufacturing process, and in a well-controlled manner. 2+ / Fe 3+This use of a redox system has the following advantages over conventional methods for producing copper foil:

[0029] First, Fe in the insoluble anode 2+ Fe 3+ The oxidation of HCl to HCl competes with and thus inhibits oxygen evolution and organic additive combustion at the anode. Therefore, the consumption of organic additives (and the subsequent generation of polluting decomposition products) is solely due to the copper deposition process at the drum cathode. This keeps the total organic content (TOC) of the electrolyte solution low, extending the life of the plating bath. In addition, due to the avoidance of oxygen evolution at the anode, the life of the anode is significantly extended.

[0030] Second, Fe in the insoluble anode 2+ Fe 3+ oxidation to Fe 3+ Because Fe is an efficient oxidizer for copper metal, there is no need to raise the temperature of the electrolyte solution to about 80°C to dissolve the copper, as is required in conventional methods for producing copper foil. 3+ The oxygen-containing gas acts as an oxidizing agent in conjunction with the oxygen-containing gas introduced into the melting unit to melt the copper metal. The temperature may be maintained at about 50°C, i.e., the same temperature as in the plating bath.

[0031] Third, lower amounts of organic compounds are destroyed, making the use of activated carbon to remove decomposition products unnecessary.

[0032] Fourth, a separate step of cooling the electrolyte solution again to about 50° C. is not required. Based on simple online analysis, the organic compounds consumed during copper deposition only need to be replenished.

[0033] Fifth, Fe 2+ / Fe 3+ With the addition of 50A / dm, oxygen bubbles are not generated at the insoluble anode. 2The voltage required to achieve a current density of 20 g / L Fe is reduced by over 25%. 2+ At 50°C and a cell current of 40 A, 60 g / L of Cu 2+ , 150g / L H2SO4, 40mg / L Cl - , added to a plating solution containing 3 mL / L of a conventional brightener, 11 mL / L of a conventional carrier, and 5 mL / L of a conventional leveling agent; the cell voltage was measured using a 2+ After the addition, the voltage dropped from 3.2V to 2.4V. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a diagrammatic representation of an apparatus for producing copper foil by conventional methods (prior art). [Figure 2] 1 is a diagrammatic representation of an apparatus for producing copper foil by a method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] In a continuous process for producing copper foil according to the present invention, copper is electrolytically deposited onto a rotating drum cathode partially immersed in an electrolyte solution; the electrolyte solution contains copper ions, organic additives, and Fe. 2+ / Fe 3+ The present invention will be described with reference to the apparatus shown in Figure 2, which may be used in the method of the present invention. The apparatus of Figure 2 may be considered as an example, and is not necessarily limiting of the method of the present invention.

[0036] As the electrolyte solution, an aqueous acid copper plating bath is preferably used. Such plating 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 wide limits. Generally, an aqueous solution having the following composition is used: copper ions: 5 to 65 g / L (e.g., as copper sulfate (CuSO4·5H2O): 20 to 250 g / L, preferably 80 to 140 g / L or 180 to 220 g / L); concentrated sulfuric acid: 50 to 350 g / L, preferably 180 to 280 g / L or 50 to 90 g / L; iron (II) ions: 3 to 40 g / L (e.g., as iron sulfate (FeSO4·7H2O): 15 to 200 g / L, preferably 15 to 150 g / L, more preferably 20 to 120 g / L or 50 to 100 g / L); chloride ions (e.g., added as NaCl): 0.01 to 0.18 g / L, preferably 0.03 to 0.1 g / L. Instead of copper sulfate, other copper salts may be used, at least in part. Even sulfuric acid may be partially or totally replaced by fluoroboric acid, methanesulfonic acid, or other acids. That is, the electrolyte solution may be free or substantially free of sulfuric acid and / or sulfate salts. Specifically, the electrolyte solution may contain methanesulfonic acid and its iron and / or copper salts.

[0037] The chloride ions are added as alkali chlorides, such as sodium chloride, or in the form of hydrochloric acid. If additional halogen ions are already present, the addition of sodium chloride may be wholly or partially omitted.

[0038] The electrolyte solution contains Fe 2+ / Fe 3+ The electrolyte solution preferably contains Fe. 2+ / Fe 3+ The total concentration of Fe ions is 3 to 40 g / L, preferably 3 to 30 g / L, more preferably 4 to 24 g / L or 10 to 20 g / L. 2+ / Fe 3+The redox system can be formed from iron(II) sulfate heptahydrate, which is particularly suitable for regenerating copper ions in aqueous acidic copper baths. However, other water-soluble iron salts, such as iron methanesulfonate and iron(III) sulfate nonahydrate, can also be used, as long as they do not contain non-biodegradable (hard) complexing agents in the compound, as the latter would cause problems during waste disposal (e.g., ferric ammonium alum).

[0039] The organic additives contained in the electrolyte solution specifically include at least one brightener, preferably an organic sulfur-containing compound, at least one leveling agent, preferably a nitrogen-containing compound, and at least one carrier. Thus, the electrolyte solution generally contains copper ions (preferably Cu 2+ ion), Fe 2+ It contains ions, acids, chloride ions, brighteners, leveling agents and carriers.

[0040] The organic sulfur-containing compound as the brightener compound is preferably selected from one or more compounds selected from the group consisting of organic thiol, sulfide, disulfide and polysulfide compounds, and preferably 3-(benzthiazolyl-2-thio)-propylsulfonic acid, 3-mercaptopropane-1-sulfonic acid, ethylenedithiodipropylsulfonic acid, bis-(p-sulfophenyl)-disulfide, bis-(ω-sulfobutyl)-disulfide, bis-(ω-sulfohydroxypropyl)-disulfide, bis-(ω-sulfopropyl)-disulfide. The brightener compounds are selected from the group consisting of methyl-(ω-sulfopropyl)-sulfide, bis-(ω-sulfopropyl)-sulfide, methyl-(ω-sulfopropyl)-disulfide, methyl-(ω-sulfopropyl)-trisulfide, S-(ω-sulfopropyl)O-ethyl-dithiocarbonate, thioglycolic acid, O-ethyl-bis-(ω-sulfopropyl)thiophosphate, 3-N,N-dimethylaminodithiocarbamoyl-1-propanesulfonic acid, 3,3'-thio-bis(1-propanesulfonic acid), tris-(ω-sulfopropyl)thiophosphate, 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 even more preferably 0.1 to 5 mg / L.

[0041] The nitrogen-containing compound as the leveling agent compound is preferably one or more compounds selected from the group consisting of ureylene polymers, polyethyleneimine, alkoxylated polyethyleneimine, alkoxylated lactams and polymers thereof, diethylenetriamine and hexamethylenetetramine, polyethyleneimine-containing peptides, polyethyleneimine-containing amino acids, polyvinyl alcohol-containing peptides, polyvinyl alcohol-containing amino acids, polyalkylene glycol-containing peptides, polyalkylene glycol-containing amino acids, aminoalkylene-containing pyrroles and aminoalkylene-containing pyridines, organic dyes such as Janus Green B, Bismarck Brown Y, and Acid Violet 7, sulfur-containing amino acids such as cysteine, and phenazinium salts. The concentration of the leveling agent compounds (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.

[0042] The oxygen-containing compound as the carrier compound is preferably one or more compounds selected from the group consisting of polyvinyl alcohol, carboxymethylcellulose, polyethylene glycol, polypropylene glycol, polyglycol stearic acid ester, alkoxylated naphthol, polyglycol oleic acid ester, stearyl alcohol polyglycol ether, nonylphenol polyglycol ether, octanol polyalkylene glycol ether, octanediol-bis-(polyalkylene glycol ether), poly(ethylene glycol-ran-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.

[0043] The method of the present invention can be carried out in an apparatus comprising a plating apparatus 1 having a plating tank containing an electrolyte solution 4 together with a rotating drum cathode 3 and a peeling tool 2, and a Cu dissolution unit 5, as shown in FIG. 2. In the method for producing copper foil according to the present invention, copper is electrolytically deposited on the rotating drum cathode 3 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 80 A / dm 2 , more preferably 40 to 70 A / dm 2 The rotation speed of the drum cathode is typically 1 to 15 m / min, preferably 5 to 10 m / min. The amount of copper deposited on the drum cathode is typically 10 to 50 kg / min, preferably 30 to 40 kg / min. The thickness of the copper foil produced by the method according to the present invention is typically 2 to 30 μm, preferably 5 to 20 μm, more preferably 7 to 12 μm.

[0044] In the method for producing copper foil according to the present invention, an insoluble anode is used as a counter electrode to a drum cathode. The current density at the insoluble anode is typically >20 A / dm 2 is.

[0045] In the method for producing copper foil according to the present invention, copper is electrolytically deposited onto a rotating drum cathode, typically at a temperature of 15 to 70°C, preferably 25 to 60°C, more preferably 40 to 50°C.

[0046] In the method for producing copper foil according to the present invention, the concentration of copper ions in the electrolyte solution is maintained constant by passing the electrolyte solution through a copper dissolution unit, and the concentration of copper ions in the electrolyte solution present in the plating bath is typically 80 to 90 g / L.

[0047] That is, a portion of the electrolyte solution present in the plating tank is continuously or periodically withdrawn from the plating tank and transferred to the dissolving unit.

[0048] 2, a portion of the electrolyte solution recovered from the plating bath is introduced into the Cu (copper) dissolution unit 5 at a position closer to the auxiliary cathode as cathode mesh 6 than to the auxiliary anode as anode mesh 7, so that the recovered portion first comes into contact with the auxiliary cathode. Unwanted copper plating, in particular in the form of copper dendrites, may be found to deposit on the cathode surface of the auxiliary cathode during copper dissolution in the Cu dissolution unit 5.

[0049] A part of the electrolyte solution recovered from the plating tank and introduced into the copper dissolution unit is the Fe 3+ Fe ion concentration higher 3+ In other words, a portion of the electrolyte solution recovered from the plating bath contains a relatively high concentration of Fe. 3+ ions (Fe 3+ 8), and Fe at a relatively low concentration compared to the electrolyte solution leaving the Cu dissolution unit 5. 2+ In the electrolyte solution leaving the Cu dissolution unit, which contains ions, Fe 3+ The ion concentration is relatively low (Fe 3+ It is a solution with low Fe 2+ ions are in relatively high concentration. Preferably, the Fe ions leaving the copper dissolution unit 3+ The concentration of the ions is less than 30% of the total iron ion concentration, preferably less than 25%, or preferably in the range of 0.25 to 25% of the total iron ion concentration.

[0050] For example: In the first experiment described above, 20 g / L Fe 2+ ions were added to the electrolytic plating solution. At this point in the electrolytic plating solution formation, Fe 3+ The concentration of Fe ions is zero. 2+ / Fe 3+ Fe in redox systems 2+ / Fe3+ The total iron ion concentration is 20 g / L. During the plating process in the plating bath and during Cu dissolution in the Cu dissolution unit, Fe 2+ ions and Fe 3+ The concentration of Fe ions in the electrolyte solution withdrawn from the plating bath and introduced into the Cu dissolution unit varies, while the overall concentration remains constant. In terms of the plating quality of the produced copper foil, the time and energy consumption for copper deposition and dissolution, 3+ Fe in the electrolyte solution leaving the Cu dissolution unit with an ion concentration of 3-12 g / L 3+ Good results were achieved when the ion concentration was 0.5-5 g / L.

[0051] The auxiliary cathode 6 is used to dissolve Fe in the Cu melting unit 5. 3+ The Fe in the recovered electrolyte solution was removed by reduction of the ions. 2+ The ion concentration is increased slightly, which helps to reduce organic additive combustion at the anode in the Cu dissolution unit 5. The potential is adjusted to avoid copper deposition at the cathode mesh 6.

[0052] In the Cu dissolution unit, Fe 3+ ions contribute to the oxidation of copper metal (thereby dissolving it), thereby 2+ Therefore, after passing through the Cu dissolution unit, the electrolyte solution contains a relatively low concentration of Fe 3+ ions, with relatively high concentrations of Fe 2+ containing ions (Fe 2+ Rich solution9).

[0053] In the copper dissolution unit 5, the electrolyte solution 4 contacts 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 contacts copper metal 10. The application of this voltage and the contact of the copper metal with the auxiliary anode promote dissolution of the copper metal introduced into the dissolution unit, resulting in a relatively large amount of copper being dissolved per unit time. This dissolution is also promoted by introducing an oxygen-containing gas into the Cu dissolution unit and bringing its bubbles 11 into contact with the surface of the copper metal. The oxygen-containing gas may be air, preferably air, and more preferably warm air bubbles. The air may be introduced by a blower 12.

[0054] In one embodiment according to FIG. 2, the Cu dissolving unit 5 comprises an additional auxiliary cathode as an additional cathode mesh, which is located close to the location where the electrolyte solution leaves the Cu dissolving unit (not shown) and which is connected to the Fe 3+ This voltage is again typically between 1 and 9 V, preferably between 2 and 4 V. The voltage of the additional auxiliary cathode is preferably lower than the voltage of the auxiliary cathode (6), preferably up to 50 percent lower.

[0055] In the process of dissolving copper metal in the Cu dissolving unit, the electrolyte solution in the Cu dissolving unit is typically 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 bath and the Cu dissolving unit.

[0056] The auxiliary cathode and auxiliary anode can be made of any kind of conductive and dimensionally stable material. The size of the melting unit is not particularly limited and can be adapted to the requirements of the method for producing copper foil, in particular the amount of copper foil produced per unit time. [Explanation of symbols]

[0057] 1. Plating equipment 2 Peeling instruments 3 Rotating drum cathode 4 Electrolyte solution 5 Cu dissolving unit 6 Auxiliary Cathode 7 Auxiliary Anode 8 Fe 3+ Rich solution 9 Fe 3+ A solution with low 10 copper metal 11 Bubbles 12 Air blower

Claims

1. 1. A continuous method for producing copper foil, comprising: Copper is electrolytically deposited on a rotating drum cathode (3) partially immersed in an electrolyte solution (4) contained in a plating bath; The copper layer deposited on the drum cathode (3) is peeled off from the portion of the drum cathode (3) that is not immersed in the electrolyte solution (4), thereby obtaining a copper foil; An insoluble anode is used as a counter electrode to the drum cathode (3); The electrolyte solution (4) contains copper ions, organic additives, and Fe 2+ / Fe 3+ Contains a redox system; The concentration of copper ions in the electrolyte solution (4) is kept constant 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); Copper metal and oxygen-containing gas are introduced into a copper melting unit (5); the auxiliary anode (7) in contact with the copper metal; The oxygen-containing gas is introduced so that its bubbles (11) contact the surface of the copper metal; The copper metal is Fe 2+ / Fe 3+ Fe in redox systems 3+ components and, optionally, by being oxidized by the oxygen contained in the oxygen-containing gas, dissolve continuously in the electrolyte solution (4), method.

2. 2. The method of claim 1, wherein the organic additives contained in the electrolyte solution include at least one organic sulfur-containing compound as a brightener, at least one nitrogen-containing compound as a leveling agent, and at least one oxygen-containing compound as a carrier.

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

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

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

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

7. 3. The method of claim 2, wherein the total concentration of the leveling agent compounds present in the electrolyte solution is from 0.5 mg / L to 400 mg / L.

8. 3. The method of claim 2, wherein the total concentration of carrier compounds present in the electrolyte solution is from 0.005 g / L to 20 g / L.

9. The current density in the drum cathode is 20 to 100 A / dm 2 9. The method according to any one of claims 1 to 8, wherein

10. 10. The method according to any one of claims 1 to 9, wherein the amount of copper deposited on the drum cathode is 10 to 50 kg / min.

11. 11. The method of any one of claims 1 to 10, wherein copper is deposited on the rotating drum cathode at a temperature of from 15 to 70°C.

12. 12. The method according to claim 1, wherein the concentration of copper ions in the electrolyte solution present in the plating bath is 80 to 90 g / L.

13. 13. The method according to any one of claims 1 to 12, wherein a portion of the electrolyte solution recovered from the plating tank is introduced into the copper dissolution unit (5) at a position closer to the auxiliary cathode (6) than to the auxiliary anode (7) so that the recovered portion first contacts the auxiliary cathode (6).

14. A part of the electrolyte solution recovered from the plating tank is introduced into the copper dissolution unit (5), and the Fe 3+ Fe ion concentration higher 3+ 14. The method of claim 1, having an ionic concentration.

15. 15. The method according to any one of claims 1 to 14, wherein the voltage applied between the auxiliary anode (7) and the auxiliary cathode (6) is 1 to 9 V.

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