Use of Ultrasound to Modified Electrodeposited Silver and Silver-Tin Microstructures and Composition without Chemical Additives

Silver coatings structures identified by XRD vs. current density reveal two main behaviours: one barely structured and the other with a preferential [110] orientation. Changing from quiet to mechanically stirred conditions, the current density threshold moves from 2.5mA/cm² to 5mA/cm². The threshold shift to 15 mA/cm² under sonication (575 kHz or 20 kHz), while agitation check with calibration is kept constant. Using ultrasound, it is possible to modify significantly the coatings without relying on chemical additives. In the case of silver-tin alloys, the current density variations coupled to the use of ultrasound lead to significant variations (color, crystalline composition and alloy composition). For an equivalent hydrodynamic agitation, silver is predominant at low current density and tin prevails at higher ones. If low frequency ultrasound is applied, Ag3Sn replaces the tin, and for high frequency, the coating is formed by an intermetallic compound of tin and silver irrespective of the current density.