Crack suppression in electrodeposited brass film through controlling growth stresses by co-depositing with Bi

Abstract

The role of Bi in suppressing crack formation in the electrodeposited brass film is methodically examined by growing brass films from cyanide-free alkaline baths with and without Bi. Electrodeposition of the brass film with Bi produces crack-free films, whereas the brass film without Bi contains several cracks. In-situ film stress measurements by the cantilever curvature technique during the film deposition process reveal that compressive stresses are commonly generated in the film deposited with Bi, while tensile stresses are present in the brass film deposited without Bi. Both the compressive and tensile growth stresses grow with the increasing layer thickness for Bi-co-deposited and Bi-free films, respectively. Additionally, at large layer thicknesses, the growing stress in Bi-co-deposited film is highly compressive compared to the highly tensile stress developed in the Bi-free brass film. The obtained results indicate that such a change in film stress from tensile to compressive is essentially caused by grain size coarsening and stacking fault formation in the Bi-co-deposited films, because co-deposition with Bi alters the nucleation and growth of Cu-Zn grains in the electrodeposition process and the incorporation of Bi reduces the stacking fault energy of Cu-Zn alloy. This study provides a pathway to suppressing crack formation by controlling film stresses through Bi-co-deposition, thus growing crack-free brass films from environmentally friendly solutions.