Why ENIG Is the Default for Modern Smartphone PCBs
Pad flatness, gold thickness, and the black-pad failure mode — why every flagship phone you own ships ENIG.
Layer-Up Engineering·4/27/2026Open any flagship smartphone and you'll find ENIG (Electroless Nickel Immersion Gold). Here's why.
Pad flatness
HASL leaves a domed solder fillet that fights with 0.4 mm pitch BGAs. ENIG gives you a flat, planar pad — table-stakes for HDI assembly.
Gold thickness matters
The IPC-4552 spec is 2–4 µin gold over 120–240 µin nickel. Go thicker on gold and you risk gold embrittlement in the solder joint; thinner and you get black-pad corrosion.
The black-pad failure mode
Excess phosphorus in the nickel layer creates a brittle interface that fractures under thermal cycling. The fix is process control at the fab — which is why we vet our partners on this exact metric.