Maintenance of Plating Solution
a) Temperature
- Different nickel processes have specific bath temperature requirements.
- Higher temperatures promote low internal stress and enhance the ductility of the nickel coating.
- Internal stress stabilizes at 50°C, with the general operating temperature maintained between 55–60 degrees C.
- Excessive temperature can lead to hydrolysis of nickel salt, causing pinholes in the coating.
- Control and maintain the temperature within the specified range using a normal temperature controller.
b) PH Value
- The PH value of the nickel plating electrolyte significantly impacts coating and electrolyte performance.
- Maintaining the PCB nickel plating electrolyte PH value between 3-4 is crucial.
- Higher PH values improve dispersion power and cathode current efficiency, but excessive levels can lead to pinholes and increased brittleness.
- Regular PH checks and adjustments are necessary during the process.
c) Anode
- Conventional nickel plating of PCBs utilizes soluble anodes, usually titanium baskets with nickel corners.
- Maintain anodes by placing them in polypropylene bags to prevent contamination and conduct regular cleaning and checks.
d) Purification
- Treat organic contamination with activated carbon, replenishing any removed additives.
- Purification involves heating, aeration, and the use of filter powder.
- Regular maintenance procedures like anode hanger cleaning and cathode plating are essential.
e) Analysis
- Regularly analyze plating solution components and conduct Hull cell testing for production adjustments.
f) Stirring
- Stirring aids mass transfer, reduces concentration changes, and increases current density.
- It is crucial in preventing pinholes in the nickel plating layer.
- Various methods like compressed air and forced circulation can be used for stirring.
g) Cathode Current Density
- Cathode current density directly affects deposition rate and coating quality.
- Select density based on solution composition, temperature, and stirring conditions.
- Adjust current density for high and low current areas on the PCB board, typically around 2A/dm2.