Ionic liquid based electroless silver plating bath for Printable circuit boards (PCBs) finishing

Immersion silver-plating technique is typically used for uniform coating on printed circuit boards (PCB) for finishing. Herein, we report an unconventional protocol for preparation of non-toxic immersion silver-plating solution/bath. The solution was prepared through electrolysis using ionic liquid (1, 3-disulfonic acid imidazolium hydrogen sulfate [Dsim] [HSO4]) as electrolyte, metallic silver (Ag) as anode and copper as cathode. As a result of electrolysis, IL-capped aqueous charged silver ion (Ag+) solution [colloidal Ag-IL adduct solution] is obtained. Presence of Ag+ in solution was verified by cyclic voltammetry (CV) experiments. Chemical reduction of Ag+ with Hydrazine Hydrate (NH2-NH2·H2O) yielded AgNPs. The AgNPs analyzed through dynamic light scattering (DLS) exhibiting 269.99 ± 14.2 nm size with Polydispersity Index (PDI) 0.126. The metallic copper strip immersed into the solution and a shiny silver plated surface obtained within 1–5 min at room temperature. Film thickness can be controlled by varying time of immersion. The corrosion rate was found to be 0.0012 mm/a by Tafel fitting. The solution is stable for the months without losing efficiency whereas the recovered IL used five times without significant loss in efficiency.