Lead Frame Metal Migration in an Encapsulated IC Package

This case study details a latent integrated circuit (IC) failure mechanism caused by the migration of silver (Ag) inside the encapsulated package of a CMOS (complementary metal-oxide-silicon) device. The plating of the lead frame was the source of the migrated silver, which was redeposited along the interface between the die attach epoxy and the plastic encapsulate. The resulting metallic ‘stringers’ bridged adjacent lead frame legs over distances greater than 150 μm and created relatively low-resistance paths capable of carrying 100’s of micro-amps.