Gold Finger PCB Manufacturing: Hard Gold Plating Process Control

This document defines the manufacturing capability limits for gold finger PCBs, focusing on selective hard gold electroplating. It provides engineers with design rules for nickel underlayer thickness (3–6 µm), hard gold thickness (0.5–5 µm), bevel angle control (20–45°), and surface finish requirements. The intent is to provide DFM guidelines that ensure consistent wear life and stable contact resistance across production volumes, not to describe general PCB fabrication.

Core Content
1. Plating Structure & Material Selection

• Copper base + Nickel barrier + Hard gold top layer.
• Nickel prevents copper diffusion and provides mechanical support.
• Hard gold (Co/Ni alloyed) provides wear resistance and low contact resistance.

2. Critical Manufacturing Parameters

• Nickel thickness: 3–6 µm (diffusion barrier & support).
• Hard gold thickness: 0.5–1 µm (low-cycle), 2–5 µm (high-cycle).
• Bevel angle: 20°–45° for insertion force control.
• Surface roughness: controlled for stable asperity contact.

3. Process Control for Uniformity

• Selective plating using dry film or tape masking.
• Current density control to avoid edge overplating.
• XRF thickness measurement (Au/Ni) per IPC-4552.

4. Inspection & Validation

• Visual inspection for nodules, pits, scratches.
• AOI for pattern alignment and bevel geometry.
• Cross-section analysis for layer adhesion.

5. Failure Modes Addressed

• Gold wear-through → nickel exposure → oxidation.
• Poor Ni-Au adhesion → delamination under cycling.
• Uneven thickness → localized premature wear.