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Development of Simple Electrolytes for the Electrodeposition of Pb-Free, Sn-Based Alloy Solder Films

Published online by Cambridge University Press:  01 February 2011

Chunfen Han ,
Qi Liu  and
Douglas G. Ivey
Chunfen Han
Affiliation:
chunfen@ualberta.ca, University of Alberta, Chemical and Materials Engineering, Edmonton, T6G 2G6, Canada
Qi Liu
Affiliation:
qi.liu@ualberta.ca, University of Alberta, Chemical and Materials Engineering, Edmonton, T6G 2G6, Canada
Douglas G. Ivey
Affiliation:
doug.ivey@ualberta.ca, University of Alberta, Chemical and Materials Engineering, Room 536 CME, Edmonton, T6G 2G6, Canada, 780-492-2957, 780-492-2881
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Abstract

A simple, cyanide-free, slightly acidic, chloride-based solution has been developed for the electrodeposition of Sn-0.7wt%Cu solder films. The solution contains only one additive (tri-ammonium citrate) other than the metal salts and is stable for more than 36 days. The optimum citrate concentration is 0.30 mol/L for 0.22 mol/L of SnCl2•2H2O. The addition of 0.003 mol/L of CuCl2•2H2O to this solution can produce near eutectic (Sn-0.7 wt% Cu) deposits, on Au, Ni or Cu substrates, at current densities of 10-12.5 mA/cm2. Plating rates are in the 20-27.5 μm/hr range at room temperature. Copper is evenly distributed (~0.7wt%Cu) through most of the thickness, with slightly higher Cu levels at the solder/Ni interface. After solder reflow at 260°C, two phases are present, Sn plus either Cu6Sn5 for Cu substrates or (Cu,Ni)6Sn5 for Ni substrates.

Keywords

solderingelectrodepositionpackaging
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 993: Symposium E – Pb-Free and RoHS-Compliant Materials and Processes for Microelectronics , 2007 , 0993-E04-07
Copyright
Copyright © Materials Research Society 2007

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