On the PCB, nickel is used as a substrate coating for precious and base metals. PCB low-stress nickel deposits are usually plated with modified Watt nickel plating solutions and some sulfamate nickel plating solutions with additives that reduce stress. Let the professional manufacturers analyze for you what problems the PCB nickel plating solution usually encounters when using it?

1. Nickel process. With different temperature, the bath temperature used is also different. In the nickel plating solution with higher temperature, the nickel plating layer obtained has low internal stress and good ductility. The general operating temperature is maintained at 55~60 degrees. If the temperature is too high, nickel saline hydrolysis will occur, resulting in pinholes in the coating and at the same time reducing the cathode polarization.

2. PH value. The PH value of the nickel-plated electrolyte has a great influence on the coating performance and electrolyte performance. Generally, the pH value of the nickel plating electrolyte of PCB is maintained between 3 and 4. Nickel plating solution with higher PH value has higher dispersion force and cathode current efficiency. But the PH is too high, because the cathode continuously evolves hydrogen during the electroplating process, when it is greater than 6, it will cause pinholes in the plating layer. Nickel plating solution with lower PH has better anode dissolution and can increase the content of nickel salt in the electrolyte. However, if the pH is too low, the temperature range for obtaining a bright plating layer will be narrowed. Adding nickel carbonate or basic nickel carbonate increases the PH value; adding sulfamic acid or sulfuric acid decreases the pH value, and checks and adjusts the PH value every four hours during the work.

3. Anode. The conventional nickel plating of PCBs that can be seen at present all uses soluble anodes, and it is quite common to use titanium baskets as anodes for the internal nickel angle. The titanium basket should be placed in an anode bag woven of polypropylene material to prevent the anode mud from falling into the plating solution, and should be cleaned regularly and checked whether the eyelet is smooth.

4. Purification. When there is organic contamination in the plating solution, it should be treated with activated carbon. But this method usually removes part of the stress-relieving agent (additive), which must be supplemented.

5. Analysis. The plating solution should use the main points of the process regulations specified in the process control. Periodically analyze the composition of the plating solution and the Hull cell test, and guide the production department to adjust the parameters of the plating solution according to the obtained parameters.

6. Stirring. The nickel plating process is the same as other electroplating processes. The purpose of stirring is to accelerate the mass transfer process to reduce the concentration change and increase the upper limit of the allowed current density. There is also a very important effect of stirring the plating solution, which is to reduce or prevent pinholes in the nickel plating layer. Commonly used compressed air, cathode movement and forced circulation (combined with carbon core and cotton core filtration) stirring.

7. Cathode current density.  Cathode current density has an effect on cathode current efficiency, deposition rate and coating quality. When using an electrolyte with a low PH for nickel plating, in the low current density area, the cathode current efficiency increases with increasing current density; in the high current density area, the cathode current efficiency is independent of the current density; while when using a higher PH When electroplating liquid nickel, the relationship between cathode current efficiency and current density is not significant. As with other plating species, the range of cathode current density selected for nickel plating should also depend on the composition, temperature and stirring conditions of the plating solution.