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Cross interactions on interfacial compound formation of solder bumps and metallization layers during reflow

Published online by Cambridge University Press:  01 December 2004

T.L. Shao ,
T.S. Chen ,
Y.M. Huang  and
Chih Chen
T.L. Shao
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 300 Taiwan, Republic of China
T.S. Chen
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 300 Taiwan, Republic of China
Y.M. Huang
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 300 Taiwan, Republic of China
Chih Chen*
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 300 Taiwan, Republic of China
*
a) Address all correspondence to this author. e-mail: chih@cc.nctu.edu.tw
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Abstract

While the dimension of solder bumps keeps shrinking to meet higher performance requirements, the formation of interfacial compounds may be affected more profoundly by the other side of metallization layer due to a smaller bump height. In this study, cross interactions on the formation of intermetallic compounds (IMCs) were investigated in eutectic SnPb, SnAg3.5, SnAg3.8Cu0.7, and SnSb5 solders jointed to Cu/Cr–Cu/Ti on the chip side and Au/Ni metallization on the substrate side. It is found that the Cu atoms on the chip side diffused to the substrate side to form (Cux,Ni1−x)6Sn5 or (Niy,Cu1−y)3Sn4 for the four solders during the reflow for joining flip chip packages. For the SnPb solder, Au atoms were observed on the chip side after the reflow, yet few Ni atoms were detected on the chip side. In addition, for SnAg3.5 and SnSn5 solders, the Ni atoms on the substrate side migrated to the chip side during the reflow to change binary Cu6Sn5 into ternary (Cux,Ni1−x)6Sn5 IMCs, in which the Ni weighed approximately 21%. Furthermore, it is intriguing that no Ni atoms were detected on the chip side of the SnAg3.8Cu0.7 joint. The possible driving forces responsible for the diffusion of Au, Ni, and Cu atoms are discussed in this paper.

Keywords

PackagingPhase transformationDiffusion
Type
Articles
Information
Journal of Materials Research , Volume 19 , Issue 12 , December 2004 , pp. 3654 - 3664
Copyright
Copyright © Materials Research Society 2004

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