PCB Tech - Causes and troubleshooting of PCB nickel plating process failure

Ma Hang: Ma Hang 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 as pinholes. Poor pretreatment, metal impurities, too little boric acid content, and too low bath temperature will all produce pinholes. Plating bath maintenance and Process control is the key, and the anti-pinhole agent should be used as a process stabilizer to supplement it.

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Roughness and burrs: Roughness means that the solution is dirty, which can be corrected by adequate filtration (if the pH is too high, the precipitation of hydroxides should be controlled). If the current density is too high, the anode mud and the impurity of the supplementary water will bring in impurities, which will cause roughness and burrs in severe cases.

Low adhesion: If the PCB copper coating is not fully deoxidized, the coating will peel off, and the adhesion between copper and nickel will be poor. If the current is interrupted, it will cause the nickel plating itself to peel off at the interruption, and peeling will occur when the temperature is too low.

The coating is brittle and the solderability is poor: When the printed PCB coating is bent or worn to a certain degree, it will usually show that the coating is brittle. This indicates that there is organic or heavy metal contamination, excessive additives, entrained organics and electroplating resists are the main sources of organic contamination, which must be treated with activated carbon. Insufficient additives and high pH will also affect the brittleness of the coating.

Dark plating and uneven color: Dark plating and uneven color indicate 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 contamination in the tank, especially the copper removal solution should use a corrugated steel cathode. At a current density of 2 to 5 A/square inch, 5 amperes per gallon of solution is plated for one hour. Poor pretreatment, poor low plating, too small current density, too low main salt concentration, and poor contact of the electroplating power circuit will all affect the color of the plating.

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

Low deposition rate: Low pH or low current density will cause low deposition rate.

Blistering or peeling of the coating: poor pre-treatment of PCB plating, too long intermediate power-off time, organic impurities pollution, excessive current density, too low temperature, too high or too low pH, and serious influence of impurities will cause blistering or Peeling phenomenon.

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