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Professional Zinc Alloy Surface Finishing Solutions

Industrial Gold Plating

Industrial Gold Plating — Connectors, PCB Gold Fingers & Precision Contacts

Functional gold for electronics: hard gold vs. soft gold, selective plating, barrel vs. rack, and the critical salt spray / contact resistance specifications that govern electronic reliability.

Why Gold in Electronics?

Gold does not oxidize. One atomic layer of oxide on a copper contact = a failed connection. Gold guarantees < 10 mΩ contact resistance for the life of the product.

Gold Fingers

PCB edge connectors

Connector Pins

Miniature contacts

Barrel vs Rack

Choice by part geometry

Salt Spray

24–96 h requirement

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The Industrial Gold Plating Process

From base metal prep through hard/soft gold deposition to final QC

1Gold Thickness Selection (0.5–5.0 μm)

Contact resistance and wear life scale with thickness. 0.5–1.0 μm: low-cycle connectors (1K–5K mate cycles). 2.0–5.0 μm: high-reliability (10K+ cycles, MIL-spec). IPC-4552 defines gold finger thickness standards.

Key Parameters
Low-cycle: 0.5–1.0 μm
Standard: 1.0–2.0 μm
High-reliability: 2.0–5.0 μm
Standard: IPC-4552

2Hard Gold (Cobalt / Nickel Hardened)

Gold alloyed with 0.1–0.5% Co or Ni. Hardness 150–250 HV vs. 50–90 HV for soft gold. Much better wear resistance for repeated mating. Preferred for connector pins, edge card fingers, and relay contacts.

Key Parameters
Hardness: 150–250 HV
Alloy: Au + 0.1–0.5% Co/Ni
Wear: Excellent — 10K+ cycles
Best for: Connectors, relays

3Soft Gold (Pure, 99.9% Au)

Pure gold for thermal compression bonding and soldering. Soft gold deforms under thermode pressure for void-free bonds. Lower hardness (50–90 HV) but superior weldability. Used for semiconductor die attach and wire bonding.

Key Parameters
Purity: 99.9% Au
Hardness: 50–90 HV
Best for: Die attach, wire bonding
Thickness: 0.5–3.0 μm

4Barrel vs. Rack Plating Selection

Barrel plating (small parts in rotating drum): efficient for mass-production connector pins, terminals, and stampings. Rack plating (fixtured): for PCB panels, odd-shaped housings, and parts needing selective plating.

Key Parameters
Barrel: Small loose parts, 1000s per load
Rack: PCB panels, selective plating
Selective: Rack with masked areas
Cost: Barrel < Rack for small parts
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Hard Gold vs. Soft Gold — Selection Guide

Both have their place in electronics manufacturing

PropertyHard Gold (Co/Ni)Soft Gold (Pure)
Hardness (HV)150–25050–90
Wear cycles10,000–50,000+500–2,000
Contact resistance< 10 mΩ< 5 mΩ
SolderabilityGood (with flux)Excellent (no flux)
Wire bondingPossible (high force)Standard (low force)
Thickness typical1.0–5.0 μm0.5–3.0 μm
Cost (per μm)Same as soft + alloySame

📌 Industrial Gold Plating Quick Reference

Thickness range0.5–5.0 μm
Hard gold (Co/Ni)150–250 HV
Soft gold (pure)50–90 HV
Contact resistance< 10 mΩ
Barrel max loadup to 15 kg
IPC standardIPC-4552
💡 Selective gold plating saves costYou don't need gold on the whole part. Selective rack plating (masked areas) plates gold only on contact surfaces — the rest stays nickel or tin. Typical saving: 40–60% of gold cost. We offer precision mask tooling for custom patterns.

FAQ

What is the minimum gold thickness for reliable connectors?
IPC-4552 specifies minimum 0.5 μm for gold fingers (Class 1) and 1.27 μm for Class 3 (high-reliability). For connector pins with 10K+ mate cycles, we recommend 2.0–3.0 μm hard gold.
Can you plate gold on stainless steel contacts?
Yes — stainless steel needs an intermediate nickel strike to activate the surface before gold. Without it, gold adhesion on stainless is unreliable. Our process: Wood's nickel strike → sulfamate Ni → hard gold.
Barrel vs. rack — which gives better gold thickness distribution?
Rack plating gives ±10% thickness uniformity across the part. Barrel plating is ±25–30% due to random contact. For critical contact resistance (e.g. 0.5 μm minimum requirement), rack or selective rack is mandatory.
How is contact resistance tested?
4-wire Kelvin method at 10–100 mA, 20 mV max open circuit. Typical spec: < 10 mΩ initial, < 20 mΩ after environmental testing (heat/humidity). We test per batch on a Caltech CR-100 or equivalent.
What salt spray rating does industrial gold plating achieve?
Gold itself is inert. The corrosion resistance comes from the nickel underlayer. Our standard process: 2 μm Ni + 1 μm Au passes 48 h neutral salt spray. With thicker Ni (5 μm): 96+ h. MIL-G-45204 Type II requires 24 h minimum.

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