On the Investigation of Residual Stresses in Brush Plated Silver Coatings

Abstract

In this study residual stresses were determined in a silver coating deposited from a commercial SIFCO Dalic Solution (Silver Hard Heavy Build, Code SPS 3080, silver cyanide 15 % – 17 %, ethylene diamine 5 % – 9 %, pH 11.7) on a brass and on a copper unclosed ring substrate. The calculation formula is extended Stoney’s formula, which takes into consideration the real shape of the substrate, and the difference between the elasticity moduli and the coefficient of the thermal expansion of the coating and the substrate materials.
Substrate deformation depending on the coating thickness was examined. The sensitivity of the method was studied and the expanded uncertainties of the computed mean values of residual stresses are presented. Residual stresses in the coating depending on the current density and on the velocity of the cathode were investigated. Residual stresses in coatings represent tensile stresses and their values range from 49 N/mm2 to 117 N/mm2 after deposition. The values of residual stresses decrease markedly and they are many times smaller after three months than after deposition.