ENIG, electroless nickel immersion gold, deposits about 3 to 6 micrometres of nickel-phosphorus and then a thin immersion gold layer, roughly 0.05 to 0.1 micrometres, that protects the nickel until soldering. It gives a flat, long-lived, solderable surface suited to fine-pitch parts and BGAs, and the joint actually forms on the nickel as the gold dissolves into the solder. Its known weakness is black pad, a corroded nickel surface that leads to brittle joints.
Go ENIG on this one, the 0.4 mm BGA needs flat pads and the boards will sit on the shelf for a year.
Also heard as
- electroless nickel immersion gold
- immersion gold
- nickel-gold
Related terms
Surface finish
Final coating on exposed copper pads that stops them oxidising and decides how well they solder.
Black pad
ENIG defect where corroded nickel under the gold produces dark, brittle solder joints that crack off.
HASL
Hot air solder leveling: finish made by dipping a board in molten solder and blowing off the excess.
Gold fingers
Hard-gold-plated contacts along a board edge that plug into a slot, as on a memory module.