Definition

Electroless Nickel Immersion Gold (ENIG) is a two-layer surface finish: 3-6 µm of electroless nickel topped with 0.05-0.1 µm of immersion gold. The nickel acts as a diffusion barrier while the gold protects against oxidation and provides solderability. ENIG offers excellent pad flatness (critical for fine-pitch BGAs), long shelf life (>12 months), and good wire bondability. It's lead-free and RoHS compliant. The main limitation is potential black pad defect from phosphorus enrichment.