Materials
ENIG
In plain English
A thin gold-over-nickel coating on the copper pads that keeps them flat and rust-free so parts attach cleanly — like a protective topcoat that never tarnishes.
The technical version
ENIG (Electroless Nickel Immersion Gold) is a surface finish consisting of a nickel barrier layer capped with a thin immersion gold layer. It provides an exceptionally flat, solderable surface ideal for fine-pitch BGAs and HDI, with good shelf life. It costs more than HASL but avoids HASL's uneven coplanarity.