Reasons and Solutions for PCB Nickel Electroplating Process Failures

In PCB proofing, nickel is used as a substrate coating for precious and base metals. For some surfaces with heavy load wear, the use of nickel as a backing layer of gold can greatly improve the wear resistance. When used as a barrier, nickel is effective in preventing diffusion between copper and other metals. The following explains the causes and solutions of PCB nickel electroplating process failures:

1. Hemp pits: The hemp pits are the result of organic pollution; if the agitation is poor, the air bubbles cannot be expelled, and the pits will be formed. Large hemp pits usually indicate oil contamination, and a wetting agent can be used to reduce its effect. Small pits are called pinholes. Poor handling, poor metal quality, too little boric acid content, and too low bath temperature will cause pinholes. Bath maintenance and process control are the keys, and anti-pinhole agents should be added as process stabilizers.

2. Roughness and burrs: Roughness means that the solution is dirty and can be corrected by full filtration (the PH is too high to form hydroxide precipitation, which should be controlled). If the current density is too high, the anode slime and the added water are impure, roughness and burrs will be produced in severe cases.

3. Low bonding force: If the copper coating is not fully deoxidized, the coating will peel off, and the adhesion between copper and nickel is poor.

4. The coating is brittle and has poor weldability: when the coating is bent or worn to a certain extent, the coating is usually brittle. This indicates that there is organic or heavy metal pollution, which must be treated with activated carbon. In addition, insufficient addition and high pH will also affect the brittleness of the coating.

5. The coating is dark and the color is uneven: the coating is dark and the color is uneven, which means there is metal pollution. Because copper is usually plated first and then nickel is plated, the copper solution brought in is the main source of pollution. To remove metal contamination in the tank, especially copper removal solutions, corrugated steel cathodes should be used, with 5 amps per gallon of solution empty for one hour at a current density of 2 to 5 amps per square foot.

6. Coating burns: Possible causes of coating burns: insufficient boric acid, low concentration of metal salts, too low working temperature, too high current density, too high pH or insufficient stirring.

7. Low deposition rate: low PH value or low current density will cause low deposition rate.

8. Foaming or peeling of the coating: poor pre-plating treatment, excessively long interruption time, organic impurity pollution, excessive current density, too low temperature, too high or too low PH, and serious influence of impurities will cause blistering or peeling phenomenon.

9. Anode passivation: The anode activator is insufficient, the anode area is too small, and the current density is too high.