Current induced segregation of intermetallic compounds in three-dimensional integrated circuit microbumps

Electromigration will induce polarity effects on the formation and dissolution of intermetallic compounds (IMCs) at the electrodes in conventional solder joints. However, the entire solder joint of a microbump may convert to intermetallic compounds after prolonged current stressing. The present study investigated the growth behavior of intermetallic compounds in a 30 μm height Sn1.8Ag microbump plated on a Cu pillar with or without an intermediate Ni layer when the substrate metallization was either Organic Solderability Preservative-Cu (OSP-Cu) or Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG). The progress of the growth of the intermetallic compounds under a current density of 1.0 × 104 A/cm2 was investigated for up to 300 h. The segregation and growth of the intermetallic compounds revealed by a three-dimensional cross section during current stressing was observed and discussed.