Maintenance and control of acid copper baths during electroplating processes

Maintenance and Control of Acid Copper Plating Baths

Composition: Copper sulfate is the source of copper ions in the solution, as the cathode and anode current efficiency is normally close to 100%, so the anode copper supplement is quite stable. Sulphuric acid increases the conductivity of the solution, reduces the polarisation of the anode and cathode and prevents the precipitation of salts, and increases the throwing power. The ratio of copper to sulphuric acid in high uniformity baths should be maintained at 1:10, with current efficiency decreasing at sulphuric acid levels above 11 vol%. Chlorine ions in high uniformity and gloss baths reduce polarisation and eliminate striateddeposits at high current densities.

Temperature: too many baths are operated at room temperature, if the temperature is too low the current efficiency and plating range will be reduced. If gloss is not required, the bath temperature can be raised to 50°C to increase the plating range for applications such as electroforming, printed circuits or printed boards.

Stirring: Air, mechanical, solution jet (solution jet), or moving plated parts can be used for stirring, the better the stirring the greater the allowable current density.

Impurities: Organic impurities are the most common in acid baths and are derived from the decomposition of brighteners, tank liners, unfiltered anode bags, stop-offs, rust inhibitors (resists), and impurities of acids and salts. The green color of the bath indicates a considerable amount of organic contamination, which must be removed by activated carbon treatment.