1 Introduction

Surface finishing is critical for printed circuit board PCB reliability and performance. Electroplated gold hard gold and immersion gold ENIG Electroless Nickel Immersion Gold are two widely used gold deposition techniques. This report evaluates their technical characteristics, advantages, limitations, and application suitability.

2 Process Overview

A Electroplated Gold

Method. Electrochemical deposition using an external current source.
Layers. Typically requires a nickel underlayer 25 μm followed by gold plating 005025 μm.
Key Features.
High durability due to thicker gold layer.
Ideal for highwear applications eg edge connectors.
Requires complex masking for selective plating.

B Immersion Gold ENIG

Method. Autocatalytic chemical displacement reaction without external current.
Layers. Nickelphosphorus layer 36 μm thin gold layer 00301 μm.
Key Features.
Uniform deposition on all exposed copper surfaces.
Flat surface ideal for finepitch components.
Susceptible to black pad defect if process control fails.

3 Key Parameter Comparison

Parameter Electroplated Gold Immersion Gold ENIG
Thickness Control. Precise adjustable via currenttime. Limited selfterminating reaction.
Surface Hardness. High hard gold 130200 HV. Low soft gold 7090 HV.
Cost. Higher equipmentenergy. Lower simplified process.
Solderability. Good requires flux. Excellent oxidationresistant.
Wire Bonding. Excellent. Poor thin Au layer.
Process Complexity. High masking current control. Moderate phtemp control.
Environmental Impact. Higher cyanidebased baths. Lower ROHScompliant baths.

4 Advantages Limitations

Electroplated Gold

Pros.
Superior wear resistance for mating contacts.
Thicker Au layer enables repeated pluggingunplugging.
Compatible with wire bonding.
Cons.
Higher materialenergy consumption.
Risk of overplating or dendrite formation.

Immersion Gold

Pros.
Costeffective for complex geometries.
Flat surface for SMT assembly.
ROHScompliant process.
Cons.
Thin Au layer limits durability.
Nickel corrosion risks black pad defect.
Unsuitable for highfrequency signals Ni layer skin effect.

5 Application Recommendations

Electroplated Gold.
Highreliability connectors militaryaerospace PCBs.
Applications requiring wire bonding eg IC substrates.
Immersion Gold.
Consumer electronics finepitch BGAQFN components.
Costsensitive projects with moderate durability needs.

6 Conclusion

Electroplated gold excels in mechanical durability and specialized applications but incurs higher costs. Immersion gold offers a balanced solution for most commercial PCB designs while minimizing process complexity. Selection depends on performance requirements, budget, and enduse environment. Hybrid approaches eg selective electroplating ENIG are increasingly adopted to optimize costperformance ratios.