After gold plating, PCB should be promptly cleaned with hot water to ensure water-free printing and meet customer appearance requirements.
Avoid storing in an acidic environment to prevent discoloration of the gold surface.
Remove pad paper and address hidden dangers that could impact upstream process quality.
Solder Mask Quality and Ink Selection:
Quality of the solder mask ink is critical, with the general ink able to minimize severity if process parameters are well controlled.
Use of specific inks like TARUM TT-9G ink for gold plating yielded no solder mask discoloration, while other inks showed varying degrees of whitening.
Timing and parameters of text baking boards were adjusted, resulting in reduced solder resist whitening.
Dew Copper Issue:
Plate density during wet film development and washing after baking affected the occurrence of dew copper.
Backwashing, increased micro-etching time, and improved wet film process were effective solutions. Common Problems and Solutions:
Color Difference:
Pollution in the nickel tank, excessive nickel ions in the gold tank, and insufficient palladium concentration in the activation tank can cause color differences.
Solutions include changing the nickel tank, analyzing nickel content in the gold tank, and increasing palladium concentration.
Rough Coating:
Strong activity of the nickel tank, inadequate filtration, and poor pretreatment can lead to rough coating.
Solutions involve adjusting temperature, concentration, and pH, improving filtration, and strengthening pretreatment.
Exposed Copper:
Foreign matter, unclean wet film development, insufficient palladium adhesion, overwashing, and imbalanced nickel tank potion can expose copper.
Solutions include heavy brushing, process review and improvement, controlling degreasing tank content, shortening washing time, and adjusting nickel tank potion.
Gold Peeling:
High phosphorus content in the nickel layer and nickel layer passivation can cause gold peeling.
Solutions involve analyzing phosphorus content, reducing reducing agent adding range, and avoiding prolonged exposure of the nickel layer.
Nickel and Copper Bonding:
Unclean copper surface and pretreatment failure may lead to poor nickel and copper bonding.
Solutions include strengthening pretreatment and monitoring and replacing chemical solution with excessive Cu+ content. Conclusion:
Quality control of the chemical nickel-gold process requires strict adherence to standard operations to reduce potential problems and hidden dangers.
