In PCB sampling, nickel is used as a substrate coating for precious and base metals. For some surfaces with heavy load wear, using nickel as the gold substrate coating can greatly improve wear resistance. When used as a barrier layer, nickel can effectively prevent the diffusion between copper and other metals. Next, CITIC Huawei will explain the causes and solutions of PCB nickel plating process faults:

1、 Ma Keng: Ma Keng is the result of organic pollution; If the stirring is poor, bubbles cannot be expelled and pits will form. Large pits usually indicate oil contamination, and wetting agents can be used to reduce their impact. Small pits are called pinholes, which can be caused by poor treatment, metal impurities, low boric acid content, and low plating temperature. Bath maintenance and process control are key, and anti pinhole agents should be used as process stabilizers to supplement.

2、 Roughness and burrs: Roughness indicates that the solution is dirty, which can be corrected by sufficient filtration (high pH can easily form hydroxide precipitates and should be controlled). When the current density is too high, the anode mud and added water are impure, and in severe cases, roughness and burrs can occur.

3、 Low adhesion: If the copper coating is not fully removed from the oxide layer, the coating will peel off and the adhesion between copper and nickel is poor.

4、 Brittleness and poor weldability of the coating: When the coating is bent or subjected to some degree of wear, it usually shows brittleness of the coating. This indicates the presence of organic or heavy metal contamination, which must be treated with activated carbon. In addition, insufficient addition and high pH can also affect the brittleness of the coating.

5、 Darkness and uneven color of the coating: Darkness and uneven color of the coating indicate metal contamination. Because copper plating is usually followed by nickel plating, the copper solution brought in is the main source of pollution. In order to remove metal contamination from the tank, especially the copper removal solution, a corrugated steel cathode should be used, with a current density of 2-5 amperes per square foot, and the solution should be empty plated with 5 amperes per gallon for one hour.

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