EFFECT OF THE CROSS-INTERACTION ON THE FORMATION AND EVOLUTION OF INTERMETALLIC COMPOUNDS IN Cu(Ni)/Sn-Ag-Cu/Cu(Ni) BGA STRUCTURE SOLDER JOINTS
LI Xunping, ZHOU Minbo, XIA Jianmin, MA Xiao, ZHANG Xinping
School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640
Cite this article:
LI Xunping ZHOU Minbo XIA Jianmin MA Xiao ZHANG Xinping. EFFECT OF THE CROSS-INTERACTION ON THE FORMATION AND EVOLUTION OF INTERMETALLIC COMPOUNDS IN Cu(Ni)/Sn-Ag-Cu/Cu(Ni) BGA STRUCTURE SOLDER JOINTS. Acta Metall Sin, 2011, 47(5): 611-619.
Abstract The formation and evolution of interfacial intermetallic compounds (IMCs) in Cu(Ni)/Sn-3.0Ag-0.5Cu/Cu(Ni) BGA (Ball Grid Array) structure solder joints both in the as-reflowed state and undergoing isothermal aging at 125℃ were investigated. The results show that there exists a significant cross-interaction effect of the solder pad/under bump metal (UBM) on the composition, morphology and growth kinetics of interfacial IMCs in solder joints. The reactions of solder/Ni UBM strongly depends on the Cu content of the solder, for a high Cu content, a continuous (Cu, Ni)6Sn5 layer forms at the interface, while for a low Cu content, a continuous (Ni, Cu)3Sn4 layer appears at the interface. The cross-interaction of Cu and Ni in Cu/Sn-3.0Ag-0.5Cu(SAC)/Ni solder joints has obvious influence on the composition and morphology of the interfacial IMC; and the IMC spalling phenomenon occurs at the interface of Ni side. During isothermal aging at 125℃, the growth rate constant of the interfacial IMC layer in SAC/Cu and Cu/SAC/Cu joints increases with the Cu concentration, and the cross-interaction of Cu and Cu decreases the interfacial IMC growth rate constant at once-reflowed Cu side. However, both of the cross-interactions of Cu-Ni and Ni-Ni increase the growth rate constant of the interfacial IMC at once-reflowed Ni side and Ni has a greater influence than Cu. The cross-interaction of Cu and Ni is beneficial for suppression of growth of Cu3Sn and reduction the growth rate of IMC at Cu side, while having no significant influence on the porosity of Kirkendall voids in Cu3Sn layer at Cu side of the joint.
Supported by Program of New Century Excellent Talents in University (No.NCET-04-0824) and Science and Technology Major Project of Guangdong Province (No.2009A080204005)
