HIGH-STRENGTH COPPER FOIL AND MANUFACTURING METHODS THEREFOR

Abstract

Manufacturing method of a high-strength copper foil, characterized in that it comprises the following steps: Heating and dissolving high-purity copper wire with a purity of over 99.95 percent in a sulfuric acid solution into a copper sulfate solution, adding electrolytic additive and tin ion solution, mixing uniformly to obtain copper electrolyte, putting copper electrolyte into an electrolytic cell to produce the foil by electrolysis, producing a copper foil by electrolysis in an electrolyzer, wherein copper foil is continuously crystallized on the surface of a cathode roller in the electrolyte and the electrolytic copper foil is then continuously peeled off from the cathode roller, and antioxidant treatment of the foil to obtain the high-strength copper foil; wherein The electrolytic additive consists of gelatin, cerium sulfate, hydroxyethylcellulose, and sodium chloride; the concentration of copper sulfate in the copper electrolyte is 100-250 g / l, gelatin 0.1-0.5 g / l, cerium sulfate 1-5 g / l, hydroxyethylcellulose 0.01-0.1 g / l, chloride ions 50-100 mg / l, sulfuric acid 50-150 g / l, and tin ions 10-50 mg / l; the electrolytic additive also consists of modified polyvinyl alcohol, and the concentration of modified polyvinyl alcohol in the electrolyte is 5-10 mg / l; the modified polyvinyl alcohol is sulfonic acid-modified polyvinyl alcohol, carboxylic acid-modified polyvinyl alcohol or phosphoric acid-modified polyvinyl alcohol; During the electrolysis of copper foil, new electrolyte is prepared to supplement the old electrolyte, from which copper ions are separated so that the concentration of the composition of the electrolyte remains the same.

Description

Field of the InventionThe invention relates to the technical field of copper foil production, preferably a high strength copper foil and production methods therefor.BACKGROUND OF THE INVENTIONElectrolytic copper foil is an important raw material for the electric industry, and is mainly used for the production of copper-clad laminates and circuit boards. As the electronic products have evolved toward miniaturization, multifunction, and high quality, the circuit boards also develop toward compactness, thinness, and flatness, which places high demands on physical and chemical properties such as tensile strength, elongation, anti-peel strength, and oxidation resistance, and homogeneity and fineness of the microstructure of the electrolytic copper foil. In the prior art, organic additives are normally introduced into the electrolysis process to improve the surface morphology and mechanical properties of the electrolytic copper foil because the organic additives contribute to good surface morphology and mechanical properties of the electrolytic copper foil in general; however, if the operating temperature of the electrolytic copper foil is too high, the atoms and voids in the copper foil are thermally activated so that the dislocation can overcome some obstacles and move. At this time, the resistance that the grain boundary must overcome upon sliding decreases, thereby lowering the tensile strength of the copper foil. For this reason, the urgent technical problem is how to improve the strength of copper foils at high temperatures.US 2020 / 0 350 620 A1 discloses a high strength copper foil produced by a special electrodeposition process in order to achieve an improved mechanical strength and conductivity.CN 1 12 144 084 A describes a method for producing a copper foil with high tensile strength, in which improved grain structure and higher mechanical stability are achieved by targeted adaptation of the process parameters.CN 1 298 458 A teaches an electrodeposition technique for producing a thin, high strength copper foil which is particularly suitable for high mechanical stress applications.US 2019 / 0 148 736 A1 discloses a copper foil with increased hardness and ductility, which is improved by an optimized heat treatment and a targeted alloy composition.CN 1 10 042 438 A describes a high-strength copper foil with a fine-grained microstructure which has an increased mechanical strength by a specific combination of rolling and heat treatment methods.CN 1 08 075 098 A discloses a manufacturing method for copper foils with high strength and improved corrosion resistance, which is realized by a modified electrolyte formulation and optimized process parameters.Content of the InventionIn order to solve the above technical problem, the invention provides a manufacturing method having the features of the main claim. Advantageous embodiments are the subject matter of the dependent claims. According to the present invention, tin ions are introduced into the electrolyte to produce SnO 2 in the electrolysis process; SnO 2 as ultrafine particles is dispersible in the electrolytic copper foil to reinforce the copper foil. In addition, SnO 2 does not decompose at high temperatures, whereby the electrolytic copper foil still has high tensile strength even at high temperatures.According to a technical scheme of the invention, manufacturing methods of a high strength copper foil comprises the steps of: heating and dissolving high purity copper wire having a purity of over 99.95 percent in a sulfuric acid solution into a copper sulfate solution, adding electrolytic additive and tin ion solution, uniformly mixing to obtain copper electrolyte, adding copper electrolyte to electrolytic cell to manufacture the foil by electrolysis, and antioxidantally treating the foil to obtain the high strength copper foil.Preferably, the electrolytic additive is gelatin, cerium sulfate, hydroxyethyl cellulose and sodium chloride; the concentration of copper sulfate in the copper electrolyte is 100-250 g / l, gelatin is 0.1-0.5 g / l, cerium sulfate is 1-5 g / l, hydroxyethyl cellulose is 0.01-0.1 g / l, chloride ions is 50-100 mg / l, sulfuric acid is 50-150 g / l and tin ions is 10-50 mg / l.A few gelatin is added to the electrolyte, while during the electrolysis process the gelatin is adsorbed to the active center of the electrode surface and forms an adsorption layer. The adsorption layer prevents the initial nucleation and further inhibits the reduction of copper ions on the electrode surface, contributing to the refinement of crystal grains.Cerium sulfate is adsorbed in the vicinity of the electrode surface, and is capable of effectively increasing the cathode polarization, changing the grain size of the crystal on the coating, refining the grain size, and improving the hardness of the copper foil.Hydroxyethyl cellulose is a nonionic surfactant having moisturizing effect, and is capable of eliminating the holes in the copper foil and improving the mechanical properties of the copper foil.Chloride ions are capable of increasing the concentration of copper ions on the electrode surface, reducing the activation and polarization, serving to grow crystal nuclei, and promoting the reduction of copper. At the same time, chloride ions can react with copper(II) ions to produce copper(II) chloride; and the insoluble layer of copper(II) chloride is adsorbed on the electrode surface to prevent the discharge of copper ions, increase the cathode polarization, and improve the crystallization. In addition, when sufficient chloride ions are present, the complex chemistry can be formed by bridging chloride ions with Cu 2+ or additive, which can increase cathode polarization and improve crystallization.In the present invention, the electrolytic additive is also made of modified polyvinyl alcohol, and the concentration of the modified polyvinyl alcohol in the electrolyte is 5-10 mg / l.In the present invention, the modified polyvinyl alcohol is sulfonic acid-modified polyvinyl alcohol, carboxylic acid-modified polyvinyl alcohol or phosphoric acid-modified polyvinyl alcohol.The modified polyvinyl alcohol can improve the solubility of polyvinyl alcohol in water, further the modified polyvinyl alcohol has the property of polyelectrolytes, and plays a role in the dispersion and protection of SnO 2- particles formed by electrolysis in the electrolyte, thereby preventing electrolysis failure and SnO 2- particles are uniformly dispersed in the copper foil and improving the mechanical properties of the copper foil; the introduction of modified groups into the modified polyvinyl alcohol contributes to increase the decomposition temperature of the polyvinyl alcohol, thereby preventing the dislocation of crystal lattice of the copper foil caused by the decomposition of the polyvinyl alcohol at high temperatures when polyvinyl alcohol is doped into the copper foil as a crystalline polymer.Preferably, the electrolysis parameters are as follows: the temperature is 30-60 degrees, current density 5-30 A / dm 2.Preferably, oxygen is continuously injected into the electrolyte during electrolysis.Preferably, the oxygen concentration in the electrolyte is 100-500 ppm by the injection of oxygen.Preferably, the electrolysis is carried out under ultrasound and the ultrasound power is 100-500 W.The oxygen supply by inflation contributes to rapid generation of SnO 2 and uniform distribution in the electrolytic solution, and ultrasonic contributes to conversion of the generated SnO 2 into ultrafine ions of small size, further preventing the conductivity of the copper foil from being lowered due to the oversized particle size of the SnO 2.Preferably, the antioxidant treatment is as follows: Wash→Rau→Wash→ Aushärten→Wash→ Passiv→Wash→Coating of silane coupling agent.The invention also provides the high strength copper foil produced by the method for producing the high strength copper foil.Effect of the InventionAccording to the present invention, tin ions are introduced into the electrolyte to produce SnO 2 in the electrolysis process; SnO 2 as ultrafine particles is dispersible in the electrolytic copper foil to reinforce the copper foil. SnO 2 does not decompose at high temperatures and further does not change the crystal structure of the copper foil, so that the electrolytic copper foil still has high tensile strength at 300°C as well. In addition, other additives are added, further contribute to smoothing and lubricating electrolytic copper foil, thereby improving the performance of electrolytic copper foil.DETAILED DESCRIPTION OF THE INVENTIONAlthough the invention has been described with reference to certain embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made without departing from the scope thereof. Accordingly, the invention is not intended to be limited to the disclosed embodiments, but is intended to include all embodiments falling within the scope of the appended claims. In particular, the invention also claims protection for the subject matter and the features of the subclaims independently of the related claims.It is to be understood that the terms used in this invention are used to describe specific embodiments only and are not intended to limit the invention. Moreover, it should be understood for the numerical range in the present invention that any intermediate value between the upper limit and the lower limit of the range is also expressly disclosed. Any value or intermediate value within the range indicated and any other value or smaller range between intermediate values within the range indicated are also included in the present invention. The upper and lower limits of these smaller ranges may be included in or excluded from the range independently of each other.Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as understood by one of ordinary skill in the art to which this invention pertains. Although only the preferred methods and materials are described in the present invention, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of contradiction to the documents involved, the content of the present specification is key.Without departing from the scope or spirit of the present invention, it will be apparent to those skilled in the art that many modifications and changes may be made to the specific embodiments of the present invention. Other embodiments that will become apparent from the description of the present invention will be apparent to those skilled in the art. The description and examples in this application are merely exemplary.As used herein, the terms "consisting of", "including", "comprising", and "containing" are all open ended terms, i.e., those mean including, but not limited to.Embodiment 1(1) Production of copper electrolyte: dissolving high purity copper wire having a purity of 99.97% in sulfuric acid solution having a volume fraction of 50% in copper sulfate solution, adding gelatin, cerium sulfate, hydroxyethyl cellulose, sodium chloride, tin (IV) chloride and sulfonic acid-modified polyvinyl alcohol, and adjusting concentrations of copper sulfate solution 200 g / L, gelatin 0.1 g / L, cerium sulfate 3 g / L, hydroxyethyl cellulose 0.05 g / L, chloride ions 80 mg / L, sulfuric acid 100 g / L, tin ions 30 mg / L, and sulfonic acid-modified polyvinyl alcohol 8 mg / L in copper electrolyte.(2) When copper electrolyte is supplied from the copper electrolyte in electrolytic cell for producing the foil by electrolysis, namely, turning on the electrolyser and starting the cathode roll; at the surface of the cathode roll in the electrolyte, the copper foil crystallizes continuously, then the electrolytic copper foil is continuously peeled off from the cathode roll and collected by the collecting device in the electrolyser; while the cathode roll deposits copper foil, the electrolyser also continuously prepares new electrolyte to replenish the old electrolytes which deposit copper ions so that the concentration of the composition of the electrolytes remains the same. Electrolytic parameters are as follows: Temperature is 45°C, current density is 25 A / dm 2; then the linear running speed of the cathode roll is adjusted to make the thickness of the copper foil 6.5-7.5 μm.(3) Antioxidant treatment: placing the copper foil in the antioxidant treatment system of hexavalent chromium and glucose, wherein the concentration of hexavalent chromium ion is 0.5 g / L and pH 4; chromium-plating the copper foil at 25° C. and a current density of 2 A / dm 2 for 30 s; then cleaning and drying to obtain high strength copper foil.Embodiment 2Everything is given as in Embodiment 1, except that the concentration of copper sulfate in the copper electrolyte is 250 g / l, gelatin is 0.2 g / l, cerium sulfate is 5 g / l, hydroxyethyl cellulose is 0.01 g / l, chloride ions is 50 mg / l, sulfuric acid is 50 g / l, tin ions is 10 mg / l and sulfonic acid-modified polyvinyl alcohol is 8 mg / l.Embodiment 3Everything is given as in Embodiment 1, except that the concentration of copper sulfate in the copper electrolyte is 100 g / l, gelatin is 0.1 g / l, cerium sulfate is 1 g / l, hydroxyethyl cellulose is 0.1 g / l, chloride ions is 100 mg / l, sulfuric acid is 150 g / l, tin ions is 50 mg / l and sulfonic acid-modified polyvinyl alcohol is 10 mg / l.Embodiment 4Everything is the same as Embodiment 1, except that electrolytic parameters are as follows: temperature is 30° C., current density is 30 A / dm 2.Embodiment 5Everything is the same as Embodiment 1, except that electrolytic parameters are as follows: temperature is 60° C., current density is 5 A / dm 2.Embodiment 6Everything is the same as Working Example 1, except that no addition of tin(IV) chloride is made.Embodiment 7Everything is the same as Working Example 1, except that no addition of modified polyvinyl alcohol is made.Embodiment 8Everything is the same as in Embodiment 1, except that the oxygen concentration in the electrolyte is maintained at 300 ppm by the injection of oxygen, and the electrolytes are treated by ultrasound with ultrasonic power of 300 W.Embodiment 9Everything is the same as Embodiment 1, except that modified polyvinyl alcohol is replaced by polyvinyl alcohol.Embodiment 10Everything is the same as Embodiment 1, except that antioxidant treatment is as follows:(1) Roughening: Placing electrolytic copper foil in a roughening solution (The concentration of copper sulfate is 50 g / L, sulfuric acid is 100 g / L, sodium phosphorus tungstate is 100 mg / L, polyethylene glycol is 100 mg / L, sodium polysulfide dipropanesulfonate is 100 mg / L) after surface cleaning to electro-plate microcrystals and then washing with water; in the roughening, the temperature is 30°C, the current density is 25 A / dm 2, and the time is 25 sec.(2) Curing: placing the roughened copper foil in a curing solution, electroplating and curing the roughened microcrystal layer, and washing with water; in the curing solution, the concentration of copper sulfate is 200 g / L, and concentrated sulfuric acid is 100 g / L; in the curing, the temperature is 30° C., the current density is 25 A / dm 2, the time is 25 s;(3) Passivation: Placing the hardened and water-washed copper foil in a passivation solution, wherein the concentration of sodium molybdate is 8 g / l, sodium phosphate is 3 g / l, zinc oxide is 3 g / l, retinoic acid is 1 ml / l and pH is 3.5, electroplating and passivation for 10 seconds at a current density of 1 A / dm 2, removal and washing.(4) Coating with silane coupling agent: Laying the passivated copper foil in 0.2% γ-(2,3-epoxypropyloxy)propyltrimethoxysilane solution at 20° C. for 5 s, then removing, washing with water and drying at 160° C.;The performances of the high strength copper foils produced in Working Examples 1-10 are tested, and the results are as shown in Table 1. Table 1 Table 1Embodiment 16504583755,24,53,9Embodiment 26424473515,84,74,0Embodiment 36554673845,34,54,2Embodiment 46354183274,94,23,8Embodiment 56474283315,23,93,5Embodiment 66153432594,52,61,8Embodiment 76474092945,03,52,9Embodiment 86694704055,54,84,2Embodiment 96354323255,04,23,4Embodiment 106654603825,44,64,0Note that after the heat treatment at 300° C. for 1 hour, the surface of the copper foil produced in Working Example 10 does not have discoloration and defects, while the surfaces of the copper foils produced in Working Examples 1-9 are easily blackened.The copper foils prepared in Working Examples 1-10 are subjected to a salt spray test: the concentration of the sodium chloride solution is 5 wt%, the temperature is 35±2°C, and the pH is 6.5-7.2. During the test, the copper foils prepared in Working Examples 1-9 are observed every 2 hours. The results are as follows: The copper foils produced in Working Examples 1-9 are oxidized and corroded to some extent in 5-6 hours, while the copper foils produced in Working Example 10 are not oxidized and corroded within 8 hours, however. The reason is that the passivation method in Embodiment 10 uses the mixture of sodium phosphotungstate, polyethylene glycol and sodium polysulfide dipropanesulfonate for decompression. Since phosphotungstic acid is an ionic complexing agent, the phosphotungstic acid radical is obtained by adding sodium phosphotungsticate for hydrolysis; the electrode reaction is accelerated by complexing phosphotungstic acid, which improves the deep plating ability and the uniformity of surface crystallization in the roughening process, so that the surface structure of the copper foil is refined, the surface is glossy, and the oxidation resistance of the copper foil at high temperature is also improved. The surface of copper foil is passivated by a passivation solution of the sodium molybdates and retinoic acid. Sodium molybdate and retinoic acid contribute to zinc ions forming a nanostructured crystal layer on the copper foil which has a good depth effect and an extremely low porosity of the coating, and to the dense and uniform coating having excellent corrosion resistance. According to the present invention, in Embodiment 10, as compared with Embodiments 1-9, hexavalent chromium ions which contaminate the environment are not used, which meets the requirements of environmental protection and sustainable development.What is described above is only the preferred embodiment of the invention, and it is not intended to limit the invention. Any change, equivalent substitution, and improvement that corresponds to the spirit and principle of the invention should be included within the scope of the invention.

Claims

A production method of a high strength copper foil, characterized by comprising the steps of: heating and dissolving high purity copper wire having a purity of over 99.95 percent in a sulfuric acid solution into a copper sulfate solution; adding electrolytic additive and tin ion solution, uniformly mixing to obtain copper electrolyte; placing copper electrolyte in electrolytic cell to produce the foil by electrolysis; producing copper foil by electrolysis in an electrolyser, wherein copper foil is continuously crystallized at the surface of a cathode roll in the electrolyte and the electrolytic copper foil is then continuously peeled off from the cathode roll; and antioxidant treatment of the foil to obtain the high strength copper foil; wherein the electrolytic additive is made of gelatin, cerium sulfate, hydroxyethyl cellulose and sodium chloride; The concentration of copper sulfate in the copper electrolyte is 100-250 g / l, gelatin is 0.1-0.5 g / l, cerium sulfate is 1-5 g / l, hydroxyethyl cellulose is 0.01-0.1 g / l, chloride ions is 50-100 mg / l, sulfuric acid is 50-150 g / l, and tin ions is 10-50 mg / l; the electrolytic additive is also modified polyvinyl alcohol, and the concentration of the modified polyvinyl alcohol in the electrolyte is 5-10 mg / l; the modified polyvinyl alcohol is sulfonic acid-modified polyvinyl alcohol, carboxylic acid-modified polyvinyl alcohol, or phosphoric acid-modified polyvinyl alcohol; in electrolysis of copper foil, new electrolyte is prepared to supplement the old electrolyte from which copper ions are deposited, so that the concentration of the composition of the electrolyte remains the same.The production method of a high strength copper foil according to claim 1, characterized in that the electrolysis parameters are as follows: the temperature is 30-60°C, and the current density is 5-30 A / dm 2.The production method of a high strength copper foil according to claim 1, characterized in that oxygen is continuously blown into the electrolyte during electrolysis.The production method of a high strength copper foil according to claim 3, characterized in that by the oxygen injection, an oxygen concentration in the electrolyte is 100-500 ppm.The production method of a high strength copper foil according to claim 1, characterized in that the electrolysis is performed under ultrasonic and the ultrasonic power is 100-500 W.The production method of a high strength copper foil according to claim 1, characterized in that the antioxidant treatment is as follows: washing → roughening → washing → curing → washing → passivating → washing → coating silane coupling agent.