What are the production methods of copper foil? What is the technological process of copper foil production? What are the problems in copper foil production? Let's first understand what copper foil is. Copper foil is a key conductive material in lithium ion batteries and printed circuit boards. Copper foil is a kind of negative electrolytic material. It is a thin, continuous metal foil deposited on the substrate of circuit board. Copper foil can be divided into many kinds according to different classifications. Copper foil can be divided into thick copper foil (more than 70 μ m) Regular thickness copper foil (more than 18 μ M but less than 70 μ m) Thin copper foil (more than 12 μ M but less than 18 μ m) Ultra thin copper foil (less than 12 μ m) Etc. Copper foil can also be divided into: single-sided treated copper foil (single-sided hair), double-sided treated copper foil (double-sided thick), smooth treated copper foil (double-sided hair), double-sided glossy copper foil (double-sided hair) and very low profile copper foil (VLP copper foil) according to the surface condition. Finally, copper foil can be divided into: Electrolytic copper foil and Calendered copper foil 。 So today we will focus on the production methods of electrolytic copper foil and calendered copper foil.

Before talking about the production method of copper foil, let's first understand the definition of electrolytic copper foil: it is formed by the deposition of copper ions in electrolyte on the round cathode roller of smooth rotating stainless steel plate (or titanium plate). The surface of copper foil close to the cathode roller is called smooth surface, and the other surface is called rough surface.

　　 Electrolytic copper foil production Methods: At present, roll cathode and insoluble anode are widely used in the continuous production of electrolytic copper foil in China.

The specific steps for producing electrolytic copper foil by roller type continuous electrolysis method are as follows:

1. Electrolysis of copper. With electrolytic copper or wire return material of equal purity as raw material, it is dissolved in the solution containing copper sulfate. Electrolysis is carried out in an electrolytic cell with insoluble material as anode and cathode roller immersed in copper sulfate electrolyte at constant speed as cathode. Copper in the solution is deposited on the surface of cathode roller to form copper foil. The thickness of copper foil is controlled by cathode current density and cathode roller speed. After the copper foil is rotated out of the liquid level with the roller, it is continuously stripped from the cathode roll, washed, dried, and rolled to generate the original foil.

2. The surface treatment process is still based on electrochemical reaction. This process is divided into three stages: the first stage is to maintain the coarsening layer of dendritic crystal structure composed of copper and copper oxide. The second order brass or zinc is used as the barrier layer. Copper foil with barrier layer can ensure that there is no substrate pollution such as particle migration during the production of printed circuit. In the third stage, in order to prevent oxidation during handling, storage or lamination, zinc, nickel, tin and other metals or alloys are used as anti oxidation coatings on the surface of copper foil.

3. That is, cutting and packaging. Since some equipment for cutting and packaging has its own control device, we will not consider it here. Thus, the whole production process can be divided into four parts: electrolytic copper dissolving, surface copper dissolving, 10 air conditioning units and 300000 air conditioning units.

Copper dissolution process in the method of electrolytic copper foil production:

1. Principle: add the processed copper material into the copper dissolving tank. The larger the surface area of the copper material, the better. There should be a small gap between the copper materials to increase the reaction area. After a certain amount of pure water and sulfuric acid are added, compressed air is introduced for oxidation reaction to generate copper sulfate solution. The chemical reaction formula is: 2Cu+2H2SO4+O2=2CuSO4+2H2O. The reaction belongs to solid liquid, solid gas and liquid gas multiphase reactions. The reaction speed is related to the total surface area of copper in the tank. The larger the surface area is, the faster the reaction speed will be. Secondly, it is related to the air volume, which increases the reaction speed.

2. Foil making raw material requirements: the thinner the copper foil is, the higher the quality grade is, and the lower the impurity content in the electrolyte is required. In order to ensure the quality of copper foil, the purity of copper must be greater than 99.9%.

Foil making equipment and principle:

1. Cathode roll: With the improvement of customer requirements and the development of technology, the diameter of the cathode roll has increased from 1m and 1.5m to 2.2m and 2.7m, and the width is 1400mm~1500mm. The material is now mostly pure titanium. The cathode roll has good corrosion resistance, and its surface quality directly affects the surface quality and visual effect of raw (original) foil, so the roll surface roughness Ra<0.3 μ m。< p="">

2. Anode seat: insoluble anode, currently used materials, one is lead antimony alloy (or lead silver alloy), the other is titanium. However, with the extension of service time, the alloy corrosion of the former is more and more, resulting in the continuous increase of pole distance, the rise of cell voltage and the increase of power consumption; At the same time, because the corrosion is not very uniform, it also affects the consistency of the pole distance, so that the uniformity of the copper foil is also poor. The latter consists of titanium matrix and coating. The coating is a mixture of iridium (56%) and tantalum (44%). This anode has good corrosion resistance, and the cell voltage will not increase within a certain limit. Therefore, the thickness of raw foil is uniform, but the one-time investment is large. Even if the coating is damaged and thinned, it can be repaired by recoating.

3. Green foil manufacturing: copper sulfate is used as electrolyte, and its main components are Cu2+and H+. Under the action of direct current, cations move to the cathode and anions move to the anode. Cu2+is reduced to Cu by two electrons on the cathode and crystallizes on the cathode roller to form green foil. After electrolytic process, the content of Cu2+in electrolyte decreases and the content of H2SO4 increases. The electrolyte returns to the copper dissolving tank for adjustment, so that the electrolyte Cu2+increases and the H2SO4 content decreases. The contents of Cu2+and H2SO4 in the electrolyte are kept in balance by electrolysis and copper dissolution.