Properties of Electroplated Sn-Ag Alloy Films as Pb-Free Solderable Coating Obtained by Composite Plating.

概要

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The compositions of the Sn-Ag alloy films obtained by the Sn/Ag-nanoparticle composite plating were near the eutectic composition, Sn-3.5wt%Ag, and were uniform over a wide current density range from 2 to 30mA/cm<SUP>2</SUP>. Hardness of the electroplated Sn-Ag alloy films was higher than that of the thermally prepared alloys, and increased by the rapid cooling after melting. This hardness change was attributed to the change in the microstructure, that is, Ag<SUB>3</SUB>Sn particles were more uniformly distributed when rapidly cooled. The bond strength of the solder ball onto the Sn-Ag alloy plated Cu was slightly smaller than that onto the Cu substrate when substrate surface was clean. However, the solder bond strength of the Sn-Ag alloy plated Cu was not decreased after the exposure to the humid environment, and somewhat increased by the Ni underlayer.
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