| Electrolytic Copper |
This is a pure form of copper, suitable for use in cyanide copper plating solutions. |
| Phosphorous De-Oxidised (PDO) |
These anodes contain low traces of phosphorous, typically 0.05% Phosphorous (0.04 - 0.08%). They are essential for use in proprietary acid copper plating solutions that use organic additives. During plating, the anode should form a dark grey / black film consisting of cuprous oxide (CuO).
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Causes of Anode Passivation in Acid Copper Electrolytes
Anode passivity in acid copper electrolytes can be caused by any of the following conditions:-
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High chloride levels - This normally results in a light grey to white anode film. Confirm by solution analysis.
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Over concentrated solution i.e. high levels of copper sulphate or sulphuric acid. Once again, confirm by analysis.
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Excessive anode current density. Depending on the degree of solution movement around the anode, anodic current density should not exceed 0.05amp per cm2 plating Rate 0.02 to 0.05 amp per cm2 Check anode area and all electrical contacts.
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Blocked Anode Bags. This will cause the solution within the bag to become supersaturated.
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Incorrect / Poor quality anodes. Insufficient phosphorous content normally results in a reddish brown film being formed on the anodes.
Low Solution Temperature.
In all cases of anode passivation, once the cause has been identified, the passive film must be removed. With bar/oval anodes, this can be done by scrubbing. With anode baskets, this is usually done by soaking in a mild copper etch such as sodium persulphate. The use of nitric acid is not recommended due to hazardous fumes being produced and severe risk of contaminating the copper plating solution.
