1. The content of insoluble particulate impurities in the electrolyte exceeds the standard. Pure, impurity free, uniform and stable electrolyte is of high quality Electrolytic copper foil Preconditions for. In actual production, some impurities inevitably enter the electrolyte through the addition of raw copper, waste foil, water and acid, as well as the wear and corrosion of equipment itself. Therefore, the electrolyte often contains various impurities such as metal impurity ions, molecular groups, organic substances, insoluble particles (such as silicon dioxide, silicate, carbon), and most of these impurities have a negative impact on the quality of copper foil, Effective methods shall be adopted to control impurities within reasonable concentration range as far as possible. Metal impurity ions are mainly controlled from raw materials, and organic matters are mainly removed by activated carbon adsorption. The electrolyte impurities described in this paper mainly refer to insoluble particles, which are mainly removed by diatomite filter and fine filter.

Statistically, it is found that the content of insoluble particles in electrolyte is 0.45 μ M microporous membrane suction filtration, calculated according to the quality difference before and after the suction filtration) When it exceeds 0.2 mg/L, no matter how other parameters are adjusted, the burr cannot be eliminated, and the higher the impurity content, the more obvious the burr. It can be seen that the excessive impurity content is one of the reasons for the burr. This is mainly because the copper powder suspended in the electrolyte is easy to be adsorbed around the impurity aggregates and adsorbed on the cathode roll under the action of the current when it is transported to the electrolytic cell. With the thickening of the copper deposit layer, the copper powder is mixed on the copper foil and forms a burr like tumor.

2. Copper acid content in copper dissolving tank is out of balance. The copper acid content in the copper dissolving tank is an important copper dissolving parameter, which directly affects the stability of the solution from the source. The change of copper content in the copper dissolving tank is generally inversely proportional to the change of acid content, that is, the increase of copper content is accompanied by the decrease of acid content, and the decrease of copper content is accompanied by the increase of acid content. According to the field production experience, the higher the copper content in the copper dissolving tank, the lower the acid content, and the more obvious the burr. Generally, when the acid content is lower than 20 g/L, burr defects are easy to appear. This is mainly because when there is too much copper material and insufficient acid in the copper dissolving tank, when the temperature in the tank is high (generally the temperature of immersion type copper dissolving is 80~90 ° C, and the temperature of spray type copper dissolving is 65~75 ° C), the air in the copper dissolving tank is very slightly dissolved, and the solution is oxygen deficient, which leads to the insufficient oxidation of copper material and the inability to fully react with sulfuric acid. A large amount of copper powder and Cu+[4] are easily generated in the copper dissolving tank. On the one hand, with the thickening of the copper foil deposition layer, the copper powder attached to the cathode surface is mixed in the copper layer to form copper spikes; On the other hand, the cuprous chloride precipitate generated by the combination of Cu+and Cl − is also easily mixed in the copper foil to form burrs.

3. The content of chloride ion in electrolyte is too high. The statistical results show that there is a certain correlation between chloride ion content and burr. The higher the chloride ion content, the more obvious the burr. Cl − is a common additive for the production of electrolytic copper foil. A small amount of Cl − can work together with other additives to enhance cathodic polarization, thus improving the surface brightness of electrolytic copper. However, too much Cl − in the electrolyte will weaken the effect of other additives, weaken the leveling effect, and cause depolarization. In addition, Cl − will combine with Cu+in the electrolyte to form cuprous chloride precipitation and inclusion in the coating to form burrs. The formation of cuprous chloride will also reduce the concentration of copper ions at the cathode interface, cause hydrogen evolution at the cathode, affect the migration and deposition of copper ions, and cause copper ion electrodeposition to form dendritic crystals, thus causing roughness and even burrs on the surface of copper foil. The content of chloride ion is generally controlled at 20~50 mg/L. If the content is too high, it will not only produce burrs, but also corrode the cathode roll and copper dissolving tank. If the content is too low, it will directly affect the internal structure and mechanical properties of copper foil.

4. Copper foil thickness. In production practice, it is found that the thicker the copper foil is, the more obvious the burr is. This is because the thicker the copper deposition layer is, the easier it is to coat the copper powder adsorbed on the surface of the cathode roll.

5. Current density. Under the condition of fixed equipment working conditions and other process parameters, the current density directly affects the production efficiency. Generally, production pursues high current density, but high current density will directly affect production stability and product quality. The statistical results show that the higher the current density, the more obvious the burr. This is because the higher the current density, the more copper powder adsorbed on the surface of the cathode roll, and the faster the speed of the cathode roll (on the same train, the higher the current density means the greater the current, and for copper foil with the same thickness and specification, the faster the speed of the cathode roll), the easier it is to coat copper powder.