ENIG (Electroless Nickel / Immersion Gold) is one of the most widely used PCB surface finishes in high-reliability and high-density electronic products. When customers choose ENIG for surface treatment, they often wonder why a layer of nickel must be plated before the gold layer.
To help you better understand, here’s how PCBasic explains the ENIG process:
ENIG Process Overview
The ENIG process includes two key steps:
1. Chemical Nickel Plating
A thin layer of electroless nickel is uniformly deposited on all exposed copper surfaces of the PCB. This nickel layer provides strong corrosion protection and an extremely flat surface, making it ideal for fine-pitch and high-density assembly.
2. Immersion Gold
A very thin layer of gold is then deposited on top of the nickel. The gold layer mainly protects the nickel from oxidation, ensuring excellent conductivity, long-term solderability, and superior corrosion resistance — especially in areas such as solder pads, connectors, and gold fingers.
Why Nickel Plating Is Necessary
• Protecting the Base Copper:
The nickel layer acts as a barrier to prevent the underlying copper from oxidation and environmental corrosion.
• Improving Solderability:
Nickel provides a better soldering surface than gold and ensures consistent, reliable solder joints.
• Preventing Copper Ion Migration:
If gold were plated directly on copper, copper ions would diffuse into the gold layer, leading to discoloration or oxidation streaks that degrade both appearance and performance. The nickel layer effectively blocks this migration, maintaining the stability and reliability of the surface finish.
At PCBasic, we adopt strict ENIG plating control — ensuring uniform nickel thickness, smooth surface, and strong adhesion between nickel and gold layers — to deliver stable performance and excellent solderability for your advanced electronic assemblies.
