Prevention of spalling by the self-formed reaction barrier layer on controlled collapse chip connections under bump metallization

C. Y. Liu, S. J. Wang

研究成果: 雜誌貢獻期刊論文同行評審

22 引文 斯高帕斯(Scopus)

摘要

The spalling phenomenon on under bump metallization (UBM) is one of the current urgent reliability issues for the Pb-free solder implementation in flip chip technology. In this paper, we report that spalling of Ni thin UBM can be prevented during the soldering reaction, if a Cu reservoir is introduced into the structure of controlled collapse chip connections (C4) solder joints. Once molten Sn-3.5Ag solder was saturated with Cu atoms, Cu precipitated out as a layer of Cu-Sn compound on Ni thin UBM. The Cu-Sn compound layer served as a reaction barrier to retard the consumption of Ni thin UBM. So, spalling was retarded. After prolonged reflowing, Ni thin UBM was converted to ternary Cu-Sn-Ni compounds. Unlike interfaces of the Ni-Sn compound/Cr, the interface of the Cu-Sn-Ni compound/Cr was very stable and no spalling was found.

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期刊Journal of Electronic Materials
32
發行號1
DOIs
出版狀態已出版 - 1月 2003

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