A Guide to ENIG (Electroless Nickel Immersion Gold) in PCBs

Printed Circuit Boards (PCBs) are the backbone of modern electronics, and ensuring their durability and performance often comes down to the type of surface finish applied. One of the most popular options in the electronics industry is ENIG — Electroless Nickel Immersion Gold.

In this article, we’ll explore what ENIG is, how it works, and why it’s a preferred finishing process for high-performance PCBs.

What is ENIG in PCB Manufacturing?

ENIG is a two-layer metallic surface finish commonly applied to PCBs. It consists of:

  • A nickel layer deposited through an electroless process, which acts as a barrier and provides mechanical strength.
  • A thin layer of gold, applied via immersion, which protects the nickel and enhances solderability.

This combination offers both durability and excellent electrical performance.

The ENIG Process: Step by Step

The ENIG finishing process follows a precise chemical sequence:

  1. Surface Preparation – The copper surface of the PCB is cleaned and activated.
  2. Electroless Nickel Deposition – A uniform layer of nickel is chemically plated onto the copper pads.
  3. Immersion Gold Plating – A thin layer of gold is deposited over nickel through an exchange reaction.

This process ensures a smooth, oxidation-resistant, and solderable finish.

Benefits of ENIG Surface Finish

ENIG is widely used due to its range of advantages:

  • Excellent Flatness – Ideal for fine-pitch components and BGA (Ball Grid Array) packages.
  • Corrosion Resistance – Gold prevents oxidation, ensuring long-term performance.
  • Good Shelf Life – PCBs with ENIG finish can be stored longer without losing solderability.
  • Compatibility with Lead-Free Soldering – Suitable for modern RoHS-compliant electronics.

 

ENIG vs Other PCB Finishes

Finish

Pros

Cons

ENIG

Excellent flatness, corrosion resistance, good for high-density designs

Higher cost

HASL (Hot Air Solder Levelling)

Cost-effective, widely used

Poor flatness, not suitable for fine-pitch components

OSP (Organic Solderability Preservative)

Low cost, environmentally friendly

Limited shelf life

Immersion Silver

Good conductivity, smooth surface

Prone to tarnishing

 

Clearly, ENIG offers a balance of quality and performance, especially in advanced electronics.

 

Applications of ENIG in Electronics

ENIG is particularly valuable in industries where precision and reliability are critical, such as:

  • Consumer electronics (smartphones, laptops, wearables)
  • Automotive electronics (sensors, control systems)
  • Telecommunications (network devices, 5G equipment)
  • Medical devices (life-support systems, diagnostic equipment)

 

ENIG remains a leading PCB finish thanks to its balance of performance, durability, and compatibility with modern assembly techniques.

If you’re in the electronics industry and seeking specialist plating solutions and photosensitive chemicals, explore the wide range of PCB and semiconductor solutions offered by A-Gas Electronic Materials. Our expert team provides not only advanced products but also technical support and consultancy to help optimise your manufacturing process.

Location: Rugby CV21 1TW, UK

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