Effects of Minor Ni Doping on Microstructural Variations and Interfacial Reactions in Cu/Sn-3.0Ag-0.5Cu-xNi/Au/Ni Sandwich Structures

摘要

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.percent), were reflowed and isothermally aged at 150 deg 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.percent to 23.4 at.percent Ni and the other with 1.3 at.percent to 6.4 at.percent 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).