Solutions to common problems of copper strips

Solutions to the discoloration of copper strips

(1) Control the concentration of the acid solution during pickling. When the oxide layer on the surface of the annealed copper strip is washed off, a high acid concentration is of no significance. On the contrary, if the concentration is too high, the residual acid adhering to the surface of the copper strip is difficult to wash off and accelerates the pollution of the cleaning water, resulting in an excessively high concentration of residual acid in the cleaning water. This makes the copper strip more prone to discoloration after cleaning. Therefore, when determining the concentration of the pickling solution, the following principle should be followed: under the premise that the oxide layer on the surface of the copper strip can be cleaned off, its concentration should be reduced as much as possible.

(2) Control the conductivity of pure water. Controlling the electrical conductivity of pure water, that is, controlling the content of harmful substances such as chloride ions in pure water. It is generally safe to keep the conductivity below 50μS/cm.

(3) Control the electrical conductivity of the hot cleaning water and the passivator. The increase in the conductivity of hot cleaning water and passivator mainly results from the residual acid carried in by the running copper strip. Therefore, while ensuring the quality of the pure water used for cleaning, control the conductivity, that is, control the amount of residual acid. Based on multiple experiments, it is safe to keep the electrical conductivity of the hot cleaning water and the passivator below 200μS/cm respectively.

(4) Ensure that the copper strip is dry. Local sealing is carried out at the winding outlet of the air cushion furnace, and a dehumidifier and air conditioner are used in the local sealing device to control the humidity and temperature during the winding of the copper strip within a certain range

(5) Passivate with a passivator. Nowadays, most copper processing plants use benzotriazole, or BTA(with the molecular formula C6H5N3), as a passivator. Practice has proved that it is a convenient, economical and practical passivator to use. When the copper strip passes through the BTA solution, the oxide film on the surface undergoes a complexation reaction with BTA, forming a dense complex that protects the copper substrate.

2. Solutions for cutting and indentation of copper strips

To prevent the formation of cutting edge indentations, it is mainly necessary to select a reasonable difference in the outer diameter of the circular knife and the rubber stripping ring based on the thickness and hardness of the strip material. The hardness of the rubber stripping ring meets the usage requirements of the cut strip material. When the width of the strip to be cut is relatively small, the thickness of the circular knife should be reasonably selected to increase the width of the rubber stripping ring.