Sn-Zn/Ni-Co Interfacial Reactions at 250 degrees C

摘要

This study examines interfacial reactions of Sn-xZn/Ni-yCo (x = 2 wt.%, 5 wt.%, 9 wt.%, y = 5-10 wt.%) carried out at 250A degrees C. Sn-Zn solders are promising lead-free solders, and Ni-Co alloys are potential alternative diffusion barrier layer materials for use in flip chip packaging of Cu/low-k integrated circuits. Sn-Zn/Ni-Co interfacial reactions depend on the competition between Co and Zn. When Co addition is 5-9 wt.%, the effect is less than that of Zn. Sn-Co intermetallics are not formed, and the reaction phase is Ni3Sn4 or the gamma-Ni5Zn21 phase. On the other hand, when Co is added at 10 wt.%, the effect is greater than that of Zn, and Co dominates the interfacial reaction. The reaction phase is then CoSn2 or the beta-Co5Zn21 phase. Similar to Sn-Zn/Ni interfacial reactions, Zn-Ni and Zn-Co intermetallics are not formed as the Zn content is 2 wt.%. When Zn addition exceeds 5 wt.%, the species affects the Sn-Zn/Ni-Co interfacial reactions. The reaction phase is the gamma-Ni5Zn21 or the beta-Co5Zn21 phase.