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

Joseph, Shany and Phatak, Girish J and Gurunathan, K and Seth, Tanay and Amalnerkar, Dinesh P and Kutty, TRN (2006) Electrochemical co-deposition of ternary Sn-Bi-Cu films for solder bumping applications. In: Journal Of Applied Electrochemistry, 36 (8). pp. 907-912.

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Abstract

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(-2) but stabilize to about 49 wt.% Bi, 47 wt. % Sn and 4 wt. % Cu at 10 mA cm(-2) 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(-2). This is attributed to the dispersion of Sn2+ ions generated at the cathode during the two-step reduction of Sn4+ ions, due to stirring. The bath is suitable for near eutectic compositions of Sn-Bi with < 5 wt.% Cu content.

Item Type:	Journal Article
Publication:	Journal Of Applied Electrochemistry
Publisher:	Springer
Additional Information:	Copyright of this article belongs to Springer.
Keywords:	solder bumping;co-deposition;electroplating;lead-free solders;electronic packaging.
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	23 Mar 2009 08:57
Last Modified:	21 Feb 2019 05:22
URI:	http://eprints.iisc.ac.in/id/eprint/17101

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