Hard Gold PCB

What is Hard Gold Plating (Electrolytic Gold)?

Hard gold is an electrolytically deposited gold layer (typically 5-50µ") over a nickel barrier, providing superior abrasion resistance compared to soft gold (ENIG).

Key Features

✔ Exceptional wear resistance – Withstands thousands of insertion cycles
✔ Excellent conductivity – Low contact resistance for high-frequency signals
✔ Nickel underlayer (3-6µm) – Prevents copper diffusion & improves corrosion resistance
✔ RoHS compliant – Lead-free for modern electronic devices

Best Applications

• Edge connectors & card guides

• Switch contacts & test points

• High-reliability military/aerospace PCBs

• Medical devices with repeated mating cycles

Why Choose Hard Gold Plating for PCBs?

✔ Durability – 10X longer lifespan than ENIG for sliding contacts
✔ Stable contact resistance – No degradation over time
✔ Wire-bondable – Unlike immersion finishes
✔ Solderable – Though typically used for non-solderable contacts
✔ Resists environmental corrosion – Ideal for harsh conditions

Limitations

• Higher cost than ENIG/immersion finishes

• Thickness impacts flexibility (too thick = brittle)

• Not suitable for fine-pitch SMT soldering (better for edge contacts)

H2: How Hard Gold Plating is Applied

Step-by-Step Process

• Copper cleaning & activation – Removes oxides and ensures adhesion

• Nickel plating (3-6µm) – Forms a barrier layer against copper diffusion

• Gold electroplating (5-50µ") – Deposited via electrolytic process for hardness

• Post-plating rinse & inspection – Ensures thickness uniformity

Critical Parameters

• Gold thickness (5-50µ") – Thicker plating = more wear cycles

• Nickel underlayer (3-6µm) – Essential for durability

• Cobalt/nickel hardening agents – Increases hardness (150-200 HK)

Hard Gold vs ENIG vs Electrolytic Soft Gold

Best Use Cases

✓ Hard Gold: Edge connectors, test points, high-wear contacts
✓ ENIG: General-purpose soldering applications
✓ Soft Gold: Wire bonding, high-frequency IC substrates