Electrochemical co-deposition of ternary Sn-Bi-Cu films for solder bumping applications

This paper reports the co-deposition of Sn-Bi-Cu films using stannic salt bath which has good stability for up to a week. The effect of current density and bath stirring on the film composition and microstructure has been studied. The deposited films are rich in the more noble metal Bi at current de...

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Bibliographic Details
Published in:Journal of applied electrochemistry 2006-08, Vol.36 (8), p.907-912
Main Authors: JOSEPH, Shany, PHATAK, Girish J, GURUNATHAN, K, SETH, Tanay, AMALNERKAR, D. P, KUTTY, T. R. N
Format: Article
Language:English
Subjects:
Chemistry
Electrochemistry
Electrodeposition
Exact sciences and technology
General and physical chemistry
Study of interfaces
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Summary:This paper reports the co-deposition of Sn-Bi-Cu films using stannic salt bath which has good stability for up to a week. The effect of current density and bath stirring on the film composition and microstructure has been studied. The deposited films are rich in the more noble metal Bi at current densities up to 5 mA cm but stabilize to about 49 wt. % Bi, 47 wt. % Sn and 4 wt. % Cu at 10 mA cm and beyond, indicating the effect of limiting current density. There is improvement in the microstructure with stirring or aeration, but the film composition reverts to the Bi rich state, with close to 90 wt. % Bi for deposition at 5 mA cm. This is attributed to the dispersion of Sn ions generated at the cathode during the two-step reduction of Sn ions, due to stirring. The bath is suitable for near eutectic compositions of Sn-Bi with
ISSN:0021-891X
1572-8838
DOI:10.1007/s10800-006-9164-5