Effect of Crystal Boundary Character and Crystal Orientation on Electromigration in Lead-free Solder Interconnects with Cyclic Twinning Structure

This study mainly examined the intermetallic compounds (IMC) migration path in flip-chip (FC) solder bump with cyclic twinning structure under current stressing. Long grain boundary was formed across the bump because of the twinning structure. If the orientation of the long crystal boundary was nearly aligned to the electron flow, IMCs migrated largely from the cathode to the anode along the long crystal boundary. Oppositely, if the orientation of the long crystal boundary was roughly normal to the electron flow orientation, it was the crystal orientation on each side of the long crystal boundary that determined the migration path of IMC.