What are the methods for producing copper foil? What is the process flow of copper foil production? What are the problems in copper foil production? Let's first understand what copper foil is. Copper foil is a crucial conductive material in lithium-ion batteries and printed circuit boards. Copper foil is a type of anionic electrolytic material, which is a thin, continuous layer of metal foil deposited on the substrate layer of a circuit board. Copper foil can be divided into many types according to different methods. Copper foil can be divided into: thick copper foil (greater than 70 μ m) Regular thickness copper foil (greater than 18 μ M but less than 70 μ m) Thin copper foil (greater than 12 μ M but less than 18 μ m) Ultra thin copper foil (less than 12 μ m) Wait. Copper foil can also be classified according to surface conditions, including single-sided treated copper foil (single-sided rough), double-sided treated copper foil (double-sided rough), glossy treated copper foil (double-sided rough), double-sided glossy copper foil (double-sided smooth), and very low profile copper foil (VLP copper foil) copper foil. Finally, copper foil is divided into electrolytic copper foil and rolled copper foil according to different production methods. So today we will focus on the production methods of electrolytic copper foil and rolled copper foil.
Copper foil
Before discussing 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 the electrolyte on a smooth rotating stainless steel plate (or titanium plate) circular cathode drum. The surface of the copper foil that is close to the cathode drum is called the smooth surface, and the other side is called the rough surface.
The production method of electrolytic copper foil: Currently, roller cathode and insoluble anode are commonly used in China to produce electrolytic copper foil by continuous method.
The specific steps for producing electrolytic copper foil using roller continuous electrolysis method:
1. Electrolytic dissolution of copper. Using electrolytic copper or wire return materials of equivalent purity as raw materials, dissolve them in a solution containing copper sulfate, and electrolyze them in an electrolytic cell with an insoluble material as the anode and a cathode roller immersed in copper sulfate electrolyte at a constant speed as the cathode. The copper in the solution deposits on the surface of the cathode roller to form copper foil, and the thickness of the copper foil is controlled by the cathode current density and the speed of the cathode roller. After the copper foil is rotated out of the liquid surface with the roller, it is continuously peeled off from the cathode roller, washed, dried, and rolled to generate the original foil.
2. The surface treatment process is still mainly based on electrochemical reactions. The process is divided into three stages: the first stage is to maintain the coarsening layer of the dendritic crystalline structure composed of copper and copper oxide. The second stage brass or zinc serves as a barrier layer. Copper foil with a barrier layer is essential in the production of printed circuits to ensure the absence of substrate contamination such as particle migration. In the third stage, in order to prevent oxidation during handling, storage, or lamination, galvanized, nickel, tin, and other metals or alloys are used as anti oxidation coatings on the surface of copper foil.
3. Cut and package separately. Due to the built-in control device of the cutting and packaging equipment, we will not consider it here. The entire production process can be divided into four parts: electrolytic copper dissolution, surface copper dissolution, 10 air conditioning units, and 300000 air conditioning units.

The copper dissolution process in the production of electrolytic copper foil:
1. Principle: Add the processed copper material into the copper dissolution tank. The larger the surface area of the copper material, the better. There should be small gaps between the copper materials to increase the reaction area. After adding a certain amount of pure water and sulfuric acid, compressed air is introduced for oxidation reaction to generate a copper sulfate solution. The chemical reaction formula is: 2Cu+2H2SO4+O2=2CuSO4+2H2O. This reaction belongs to solid-liquid, solid-gas, and liquid-gas multiphase reactions. The reaction rate is related to the total surface area of the copper material in the tank, and the larger the surface area, the faster the reaction rate. Secondly, it is related to the air volume, as an increase in air volume accelerates the reaction speed.
2. Foil material requirements: The thinner the copper foil thickness, the higher the quality grade, and the lower the impurity content in the electrolyte. To ensure the quality of copper foil, the purity of copper material must be greater than 99.9%.
Equipment and principle for foil making:
1. Cathode roller: With the improvement of customer requirements and the development of technology, the diameter of the cathode roller has increased from 1m and 1.5m to 2.2m and 2.7m, with a width of 1400mm~1500mm. The material is now mostly pure titanium. The cathode roller has good corrosion resistance, and its surface quality directly affects the surface quality and visual effect of the raw (original) foil, so the roller surface roughness Ra<0.3 μ M< P="">
2. Anode holder: It is an insoluble anode and currently uses materials such as lead antimony alloy (or lead silver alloy) and titanium. As the usage time of the former increases, the alloy corrodes more and more, resulting in an increase in pole distance, an increase in slot voltage, and an increase in power consumption; Meanwhile, due to uneven corrosion, it also affects the consistency of pole spacing, resulting in poor uniformity of copper foil. The latter is composed of a titanium matrix and a coating. The coating is a mixture of iridium (56%) and tantalum (44%), and this anode has good corrosion resistance. Within a certain limit, the slot voltage will not increase significantly, so the thickness uniformity of the foil is good, but the one-time investment is relatively large. Even if the coating is damaged and thinned, it can be repaired by re coating.
3. Raw foil manufacturing: Copper sulfate is used as the electrolyte, and its main components are Cu2+and H+. Under the action of direct current, cations move towards the cathode and anions move towards the anode. Cu2+is reduced to Cu by two electrons on the cathode, and crystallizes on the cathode roller to form a green foil. After the electrolysis process, the Cu2+content of the electrolyte decreases and the H2SO4 content increases. The electrolyte returns to the copper dissolution tank for adjustment, causing an increase in Cu2+in the electrolyte and a decrease in H2SO4 content. Through two processes of electrolysis and copper dissolution, the content of Cu2+and H2SO4 in the electrolyte is maintained in equilibrium.