Problems and Solutions of PCB Nickel Plating
1. Coating Burn
Possible reasons for coating burns: insufficient boric acid, low metal salt concentration, too low operating temperature, too high current density, too high pH value or insufficient stirring.
2. Low Deposition Rate
Low pH or low current density will cause low deposition rate.
If the copper plating layer is not activated to remove the oxide layer, the adhesion between copper and nickel will be poor, and the plating layer will peel off. If the current is interrupted, it may cause the nickel coating to peel off. If the temperature is too low, peeling will also occur.
3. The coating is brittle and with poor solderability.
When the coating is bent or worn to a certain degree, the brittleness of the coating is usually revealed, which indicates the presence of organic or heavy metal contamination. Too many additives increase the organic matter and decomposition products entrained in the coating, which is the main source of organic pollution, which can be treated with activated carbon. Heavy metal impurities can be removed by electrolysis and other methods.
4. Darkening of the coating and uneven color
The coating is dark and uneven in color, indicating that there is metal contamination. Because copper is generally plated first and then nickel is plated, the copper solution brought in is the main source of pollution. It is important to reduce the copper solution on the hanger to a minimum. In order to remove the metal pollution in the tank, corrugated steel plate is used as the cathode, and electrolytic treatment is performed at a current density of 0.12～0.50A/dm2. Poor pretreatment, poor bottom coating, too small current density, too low main salt concentration, and poor conductive contact will all affect the color of the coating.
5. The coating is blistering or peeling.
Poor pre-plating treatment, excessively long intermediate power-off time, organic impurities pollution, excessive current density, too low temperature, too high or too low pH value, and serious influence of impurities will cause blistering or skinning.
6. Anode Passivation
The anode activator is insufficient, and the anode area is too small and the current density is too high.
Pinhole is the result of organic pollution. Large pits usually indicate oil pollution. If the stirring is not good, the air bubbles cannot be expelled, which will form pits. Wetting agents can be used to reduce its impact. We usually call small pits pinholes. Poor pretreatment, metal impurities, too little boric acid content, and too low bath temperature will all produce pinholes, so the bath is maintained and strict control of the process is the key.
8. Rough (burr)
Roughness means that the solution is dirty, which can be corrected by adequate filtration. Too high PH can easily form hydroxide precipitation and should be controlled. The current density is too high, the anode mud and the impure addition of water will bring impurities, and severely will produce roughness (burr).
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