Ni segregation in the interfacial (Cu,Ni)_6Sn_5 intermetallic layer of Sn-0.7Cu-0.05Ni/Cu ball grid array (BGA) joints

摘要

Ni segregation in the interfacial (Cu,Ni)_6Sn_5 intermetallic layer of Sn-0.7Cu-0.05Ni/Cu BGA solder joints was investigated by using synchrotron micro X-ray fluorescence (XRF) analysis and synchrotron X-ray diffraction (XRD). Compared to Sn-0.7Cu/Cu BGA joints, Ni containing solder show suppressed Cu_3Sn growth in both reflow and annealed conditions. In as-reflowed Sn-0.7Cu-0.05Ni/Cu BGA joints, Ni was relatively homogenously distributed within interfacial (Cu,Ni)_6Sn_5. During subsequent annealing, the diffusion of Ni in Cu_6Sn_5 was limited and it remained concentrated adjacent the Cu substrate where it contributes to the suppression of Cu_3Sn formation at the interface between the Cu substrate and Cu_6Sn_5 intermetallics.