Gold Finger Plating Technology: Electrolytic Hard Gold Process Parameters

This white paper details the electroplating process for hard gold fingers, from surface preparation to final thickness validation. It explains how current density, bath temperature, and additive chemistry control grain structure, hardness (150–200 HV), and internal stress. The focus is on process variables that engineers must specify to achieve consistent wear life and contact resistance, not on general plating theory.

Core Content 

1. Electroplating Fundamentals

• Electrolytic deposition of gold over nickel underlayer.
• Hard gold alloyed with Co or Ni (0.1–0.3%) for hardness.

2. Process Parameter Control

• Current density: 0.5–2.0 A/dm² (affects grain size and hardness).
• Temperature: 50–65°C (kinetics and grain refinement).
• pH: 4.0–5.5 (bath stability).
• Plating time: thickness ∝ current × time × efficiency.

3. Uniformity Challenges

• Edge effect: higher current density at edges → overplating.
• Solutions: shielding plates, auxiliary cathodes, optimized rack design.

4. Grain Structure & Hardness

• Fine grains (refined by additives) → higher hardness (150–200 HV).
• Coarse grains → lower hardness, higher wear rate.
• Internal stress control to avoid microcracking.

5. Post-Plating Processes

• Beveling before plating (20–45°) for insertion smoothness.
• Polishing to control surface roughness (not mirror finish).