RETRACTED: Strengthening effects of ZrO2 nanoparticles on the microstructure and microhardness of Sn–3.5Ag lead-free solder

This article has been retracted at the request of the Editors. Please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).Reason: The Editors of Materials Science and Engineering A formally announce the retraction of this article due to duplicate publication in J. Electronic Mater., 35 (2006) 1672–1679.