Abstract
The effects of Ni doping on microstructural variations and interfacial reactions in Cu/Sn-3.0Ag-0.5Cu-xNi/Au/Ni sandwich structures were investigated. The sandwich structures, i.e., Cu/Sn-3.0Ag-0.5Cu/Au/Ni and Cu/Sn-3.0Ag-0.5Cu-0. 1Ni/Au/Ni (wt.%), were reflowed and isothermally aged at 150°C for 500 h. The behavior of Ni and Cu migration in the solders before and after aging was investigated using field-emission electron probe microanalysis (FE-EPMA), and the microstructure evolution of the solders with Ni doping was investigated. It was observed that Ni migrated to the board Cu-side, while Cu tended to migrate toward the Ni/Au package side, and two different types of (Cu,Ni) 6 Sn 5 intermetallic compounds (IMCs), one with 19.8 at.% to 23.4 at.% Ni and the other with 1.3 at.% to 6.4 at.% Ni content, were found. Regarding interfacial reactions, it was identified that the local Ni and Cu concentrations affected the formation of (Cu,Ni) 6 Sn 5 . Redistribution of Ni and Cu was correlated with the formation mechanism of interfacial (Cu,Ni) 6 Sn 5 . © 2010 TMS.