Effect of Ni-W alloy barrier layer on copper pillar/Sn IMCs evolution

In this paper, the effect of Ni-W alloy barrier layer on copper pillar/Sn IMCs evolution has been investigated. Additive W weight content of Ni-W alloy ranged from 16 to 18 at. %. Controlled thickness of barrier layer was prepared on Cu substrate. Then, excessive matte Sn electroplated on as-deposited Ni-W layer. Ni-W had compact microstructure in state of FCC solid solution, which means it had good diffusion buffering potential for copper pillar consisting of Cu/Ni-W/Sn Summarized from BSE pictures of samples done by High Temperature Storage, it can be observed that no Sn atoms can be found in Cu Phase during the whole of High Temperature Storage while “bright” layer appeared and grew linearly over time. Besides, Cu atoms permeated throughout the entire Ni₃Sn₄ IMC layer with storage time prolonged from 72h to 132h.