Electroplating and Properties of SnBi and SnCu for Lead-Free Finishes

SUMMARYTin alloys such as Sn-0.7% Cu and Sn-2%Bi were identified as viable alternatives to tin-lead finishes. Electroplating of these alloys is challenging because of the great difference in reduction potentials of the individual elements and the usual problems associated with strong immersion deposition and poor alloy control. To overcome these problems we utilised metal-specific non-complexing organic additives, which can significantly slow down or completely inhibit deposition of the alloying element in a certain range of potentials. In this paper, we present the recent developments for SnBi and SnCu plating chemistries. The plating electrochemistry and materials properties of deposited alloys are discussed.