Reaction of Au/Pd/Cu and Au/Pd/Au/Cu multilayers with Sn-Ag-Cu alloy.

Abstract The requirements of low resistivity and small magnetic permeability in the high-frequency signal delivery applications have driven the development of Ni-free surface finishes, such as Au/Pd (EPIG) or Au/Pd/Au (IGEPIG), over the Cu conducting lines. The compatibility of these newly developed surface finish techniques with microelectronic packages and their long-term, high temperature reliability still require investigations in the current state. We conducted a solderability evaluation on the Au/Pd/Cu and Au/Pd/Au/Cu multilayers and found no noticeable differences of the intermetallic compound species (i.e., (Cu,Pd) 6 Sn 5 and Cu 3 Sn) in the joint interfaces between the two examined cases. However, numerous bump voids might be formed in the vicinity of the solder/Cu interface of the EPIG case, degrading the shear resistance of solder joints. The formation mechanism of the bump voids and the evolution kinetics were proposed in this study. Highlights • A comparative study between Au/Pd/Cu (EPIG) and Au/Pd/Au/Cu (IGEPIG). • Au nanolayer (10 nm) inhibited the bump void formation. • Bump voids merged as larger ones upon soldering. • Bump voids degraded the LSBS resistance of solder joints. • IGEPIG surface finish possesses better solderability than EPIG. [ABSTRACT FROM AUTHOR]