Effects of Ni thickness and reflow times on interfacial reactions between Ni/Cu under-bump metallization and eutectic Sn-Pb solder in flip-chip technology

Authors: Huang, Chien-Sheng; Duh, Jenq-Gong; Chen, Yen-Ming; Wang, Jyh-Hwa

Source: Journal of Electronic Materials, Volume 32, Number 2, February 2003 , pp. 89-94(6)

Publisher: Springer

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Flip-chip interconnection technology plays a key role in today’s electronics packaging. Understanding the interfacial reactions between the solder and under-bump metallization (UBM) is, thus, essential. In this study, different thicknesses of electroplated Ni were used to evaluate the phase transformation between Ni/Cu under-bump metallurgy and eutectic Sn-Pb solder in the 63Sn-37Pb/Ni/Cu/Ti/Si3N4/Si multilayer structure for the flip-chip technology. Interfacial reaction products varied with reflow times. After the first reflow, layered (Ni1−x,Cux)3Sn4 was found between solder and Ni. However, there were two interfacial reaction products formed between solders and the UBM after three or more times reflow. The layered (Ni1−x,Cux)3Sn4 was next to the Ni/Cu UBM. The islandlike (Cu1−y,Niy)6Sn5 intermetallic compound (IMC) could be related to the Ni thickness and reflow times. In addition, the influence of Cu contents on phase transformation during reflow was also studied.

Keywords: Flip chip; diffusion; intermetallic compound; phase transformation; under-bump metallization

Document Type: Research Article

DOI: http://dx.doi.org/10.1007/s11664-003-0241-9

Affiliations: Email: jgd@mse.nthu.edu.tw

Publication date: February 1, 2003

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