Abstract
Flip-chip interconnection technology plays a key role in today's electronics packaging. Understanding the interfacial reactions between the solder and under-bump metallization (UBM) is, thus, essential. In this study, different thicknesses of electroplated Ni were used to evaluate the phase transformation between Ni/Cu under-bump metallurgy and eutectic Sn-Pb solder in the 63Sn-37Pb/Ni/Cu/Ti/Si 3 N 4 /Si multilayer structure for the flip-chip technology. Interfacial reaction products varied with reflow times. After the first reflow, layered (Ni 1-x ,Cu x ) 3 Sn 4 was found between solder and Ni. However, there were two interfacial reaction products formed between solders and the UBM after three or more times reflow. The layered (Ni 1-x ,Cu x ) 3 Sn 4 was next to the Ni/Cu UBM. The islandlike (Cu 1-y ,Ni y ) 6 Sn 5 was formed between (Ni,Cu) 3 Sn 4 and solders. The amounts of (Cu 1-y ,Ni y ) 6 Sn 5 intermetallic compound (IMC) could be related to the Ni thickness and reflow times. In addition, the influence of Cu contents on phase transformation during reflow was also studied.