ENIG Surface Finish (Electroless Nickel Immersion Gold)
CAS Number: 7440-02-0
ENIG (Electroless Nickel Immersion Gold) is a two-layer PCB surface finish consisting of a 3–6 µm electroless nickel layer topped with a thin 0.05–0.15 µm immersion gold layer. The nickel provides a flat, solderable surface and a diffusion barrier, while the gold protects the nickel from oxidation and ensures excellent solderability. ENIG is the most widely used surface finish for fine-pitch SMT and wire bonding applications.
Technical Specifications
| flatness | <5 µm across pad |
| standard | IPC-4552 |
| goldThickness | 0.05–0.15 µm |
| solderability | Passes J-STD-003 Cat 3 |
| nickelThickness | 3–6 µm |
| phosphorusContent | 6–10 wt% (mid-phosphorus Ni) |
Applications
- Fine-pitch SMT assembly
- BGA pad surface finish
- Wire bonding pad finish
- High-reliability PCB surface protection
- RF and microwave PCB pads
Key Features
- Flat surface ideal for fine-pitch and BGA components
- Long shelf life — no oxidation of gold surface
- Compatible with lead-free soldering and wire bonding
- Meets IPC-4552 industry standard