(9) Nickel Plating
- Purpose: The nickel-plated layer acts as a barrier layer between the copper layer and the gold layer to prevent the diffusion of gold and copper, ensuring solderability and the board’s service life. Additionally, it enhances the mechanical strength of the gold layer.
- Relevant Process Parameters:
- Addition of nickel plating additives: Typically supplemented based on the method of thousand ampere hours or actual production board effect, with an approximate addition amount of 200ml/KAH.
- Current calculation of pattern nickel electroplating: Generally 2 ampere/square minutes multiplied by the plated area of the board in meters.
- Nickel cylinder temperature maintenance: Kept at 40-55 degrees, with a general temperature of approximately 50 degrees, requiring a heating and temperature control system.
(10) Gold Electroplating - Purpose: Gold provides excellent characteristics such as weldability, oxidation resistance, corrosion resistance, low contact resistance, and alloy wear resistance.
- Citric Acid Gold Bath: Widely used due to its simple maintenance and convenient operation.
- Control parameters: Gold content – about 1 g/L, pH value – about 4.5, temperature – 35 degrees, specific gravity – about 14 Baume degrees, and current density – about 1ASD.
- Main additives: Acid-type and basic-type adjustment salt for pH adjustment, conductive salt for specific gravity adjustment, and supplementary additives for gold plating and gold salt.
- Post-plating procedures: Use pure water wash as recovery water wash, supplement liquid level of gold vat due to evaporation, and employ a citric acid dip tank to reduce pollution and maintain stability.
- Anode material: Platinum-plated titanium mesh is recommended for the gold cylinder, preventing contamination and defects in the gold plating process.
- Maintenance: Continuous filtration by carbon core for organic pollution and timely supplementation of gold plating additives.
