Growth of Cu-Sn intermetallic compounds during isothermal aging processing in electroplated Cu/Sn/Cu system

Microstructure evolutions of as-reflowed and aged electroplated Cu/Sn/Cu sandwich structure with 20 or 40μm Sn layer have been investigated. Cu₃Sn was observed at lower side of Cu/Sn/Cu structure with 40μm Sn layer after isothermal aging treatment for 24 hours, as for that structure with 20μm Sn layer, Cu₃Sn appeared after aging for 48 hours. Regardless of Sn volume, the thickness of the blanket Cu₆Sn₅ and total intermetallic compounds (Cu₆Sn₅+Cu₃Sn) increased linearly with the increasing aging time. After long-time aging processing, the layers of blanket Cu₆Sn₅ and Cu₃Sn in the the Cu/Sn/Cu structure with 20μm Sn layer are both thicker. Volume of Sn layer has significant effect on the growth of Cu-Sn IMCs in the electroplated Cu/Sn/Cu system.