Analysis of ENEPIG bond pad peel-off after wire bonding

Peel-off phenomena of ENEPIG (electroless nickel electroless palladium immersion gold) after wire bonding process was analyzed. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were conducted on peel-off regions. Peel-off was observed to be occurring at interface between electroless palladium and immersion gold layers. Further focus ion beam (FIB) and transmission electron microscopy (TEM) analyses indicates that the peel off of palladium layer from gold layer could have been caused by localized corrosion occurred during plating process. Depletion of nickel and oxidation of nickel phosphorous was observed in corrosion region. Corrosion mechanism of plating layer and strengths of plating adhesion and wire bonding were discussed.