Black pad is a failure of ENIG finish in which the nickel is excessively attacked during the immersion gold step, leaving a phosphorus-rich, corroded surface. Solder wets the gold but forms a weak bond to the damaged nickel beneath, so joints fracture under stress and reveal a dark, mud-cracked pad. It traces back to poor bath control at the fabricator, which is why critical buyers audit ENIG lines or switch to ENEPIG.
BGA popped off and the pads underneath are black and mud-cracked, that's black pad, quarantine the lot.
Also heard as
- nickel hyper-corrosion
Related terms
ENIG
Electroless nickel immersion gold: flat surface finish of nickel topped with a very thin layer of gold.
Surface finish
Final coating on exposed copper pads that stops them oxidising and decides how well they solder.
Head-in-pillow
BGA defect where a solder ball rests in melted paste but never fuses with it, leaving a hidden weak joint.