Causes of pinholes in vacuum silver-plated nickel layer

Causes of pinholes in vacuum silver-plated nickel layer

There are too many oil or organic impurities in the plating solution, solid particles in the plating solution, too little anti-pinhole agent, too much heavy metal impurities such as iron in the plating solution, too high pH of the plating solution or too high operating current density. Too little boric acid in the bath and too low bath temperature will cause pinholes in the nickel layer.

The pinhole phenomenon caused by different reasons is slightly different, so when analyzing the fault, the first thing to observe is the phenomenon.

For example, poor pre-plating treatment only makes the oil or rust on the partial surface of the workpiece not completely removed, causing the gas to stay in these parts easily and generate pinholes. The pinhole phenomenon caused by this factor is locally dense and irregular.

There are many pinholes caused by oil in the plating solution that appear on the lower part of the part and the parts on the upper part of the hook. The suspended matter with smaller density and finer is often easily adsorbed on the downward surface of the workpiece, causing this part to be hydrophobic, so that the gas is easy to stay in this part and cause pitting or pinholes.

When there are too many organic impurities in the plating solution, there are more pinholes and pits, and the distribution is more uniform. For oil and organic impurities, it can be removed by activated carbon adsorption.

There are pinholes or pits on the upper coating of the workpiece, which are usually caused by the sedimentation of non-conductive suspended solids with high density there. For solid particles, filtration can be used to remove them.

There are pinholes in all parts of the parts, and the pinholes and pits are small and evenly distributed. When the foam of the stirring bath is also small, it indicates that the content of anti-pinhole agent in the bath is insufficient, and the surface tension of the bath is not adjusted. It is caused by the fact that the bubbles generated or adsorbed on the interface between the workpiece and the solution are not easily released.

Pinholes and pitting are ringworm-like, and most of them appear under the plating parts. If the plating layer is foggy and brittle, it indicates that there are too many iron impurities in the plating solution and the pH value is too high. The plating solution should be filtered and adjusted with 10% sulfuric acid solution. The pH value of the bath is to the normal process specification.

There are pinholes or pockmarks on the protruding parts of the workpiece or the coating on the edges, which may be caused by too many foreign metal impurities, too little boric acid, too high pH value of the plating solution or too high current density, and the high current density part of the workpiece in the cathode film. The pH value is too high, which leads to the formation of hydroxides or basic salts of different metal impurities easily attached to the coating.

In actual production, it is possible to determine which factor is the result of the influence of the factors according to the shape of the pinholes and pits in the nickel-plated layer, the degree of dispersion, and the location of the plated parts, and then the right medicine can be dealt with.

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