A review of developments in the electrodeposition of tin-copper alloys

The deposition of Sn–Cu binary alloys, mainly from aqueous electrolytes, is considered. The importance of tin–copper electrodeposits is summarised and the scope for plating them is highlighted. Sn–Cu (bronze) deposits are important in corrosion protection, decorative finishes, electronics and tribology. The past 20 years have seen a series of developments in the science and technology of bronze plating, including nanostructured deposits, environmentally friendly baths, such as methanesulfonic acid ones, and more ambitious coatings including multi-layers and composites. Among non-aqueous baths, room temperature ionic liquid electrolytes have received increasing attention. Our ability to realise controlled deposit morphology, composition and structure has been improved by newer electrolytes, improved electrolyte additives and pulse plating. The diversity of Sn–Cu deposit applications has extended to lithium batteries by newer layer structures such as composites, multi-layers and nanostructures), electrical control and relative bath/electrode movement. Electrochemical aspects of modern tin and bronze alloy deposition are illustrated by data from the authors' laboratory and elsewhere, which highlights the use of methanesulfonic acid electrolytes in tin alloy deposition due to their versatility and lack of environmental impact. A wide range of deposit composition, colour and surface finish are possible using suitable addition agents and by control of electrolyte flow and operating conditions. This review focuses on electrochemical voltammetry techniques together with morphological information from SEM imaging. Subject areas deserving further research and development are identified.