Abstract
Flip-chip technology with the layout of ball grid array has been widely used in today's microelectronics industry. The elemental distribution in the edge of the solder bump is crucial for its correlation with the bump strength. In this study, Ni/Cu under-bump metallization (UBM) was used to evaluate the intermetallic compound (IMC) formation in the edge of the solder bump between the UBM and eutectic Sn-Pb solder in the 63Sn-37Pb/Ni/Cu/Ti/Si 3 N 4 /Si multilayer structure. During reflows, layered-type (Ni 1-x Cu x ) 3 Sn 4 and island-like (Cu 1-y Ni y ) 6 Sn 5 IMCs formed in the interface between the solder and UBM, while only the (Cu 1-y Ni y ) 6 Sn 5 IMC was observed in the sideway of the Ni/Cu UBM. After high-temperature storage (HTS) at 150°C for 1,000 h, both (Cu 1-y Ni y ) 6 Sn 5 and (Cu 1-z Ni z ) 3 Sn were found in the sideway of the Ni/Cu UBM. Two other IMCs, (Ni 1-x Cu x ) 3 Sn 4 and (Cu 1-y Ni y ) 6 Sn 5 , formed in the interface between the solder and UBM. The growth of the (Cu 1-y Ni y ) 6 Sn 5 IMC was relatively fast during HTS.