At the connection point of power equipment, the exposed copper strip soft connector will gradually turn black and oxidize, causing the resistance to soar or even heat up and catch fire. The surface treatment process is designed to address these hidden dangers.
1. Combat natural corrosion
Copper reacts with oxygen and water vapor in the air to form basic copper carbonate (copper green), especially in humid or sulfur-containing environments such as coastal areas and chemical plants. After surface tin or silver plating, the dense metal layer can isolate air contact and reduce oxidation rate by more than 90%. The measured data of a certain substation shows that the resistance of untreated copper soft connectors increases by 15% after 3 months, while the change in tin plated copper strip during the same period is less than 2%.
2. Ensure smooth current flow
The oxide layer on the copper surface will form an insulation barrier, increasing the contact resistance. The tin plating layer not only has good conductivity (resistivity of about 0.012 Ω· mm ²/m), but also can fill micro gaps during bolt crimping. When current passes through, the treated surface can reduce contact loss by 15% -20%, which is crucial for temperature control of high current devices such as new energy battery packs.
3. Improve welding reliability
If the copper flexible connector needs to be welded for installation, surface grease or oxides may cause virtual welding. Copper strips treated with acid pickling and passivation can increase the tensile strength of solder joints by more than 30%. Especially in ultrasonic welding technology, a clean surface can increase the efficiency of sound wave energy transfer by 40%, avoiding the risk of "false welding".
4. Block electrochemical erosion
When copper comes into contact with other metals (such as aluminum terminals), it forms a primary battery in the electrolyte environment, accelerating the ionization and dissolution of copper. The surface coating acts as a "barrier" that can effectively block electron migration. The ten-year tracking report of tin plated copper strip in automotive electronic control units shows that its electrochemical corrosion rate is only 1/8 of that of bare copper.
When choosing the type of coating, it is necessary to weigh the scenarios: tin plating is used in conventional environments (high cost-effectiveness), nickel plating is used in highly corrosive environments (more acid and alkali resistant), and silver plating is recommended for high-precision instruments (with the lowest contact resistance).
