Changes

A tin coating by ion exchange is usually not possible, since copper is the more precious metal. By adding thio-urea the electro-chemical potential of copper is reduced to a level (approx. 450 mV, significantly lower than tin) that allows the exchange reaction. Using a suitable electrolyte composition and enhancer solutions like within the DODUSTAN process (<xr id="fig:Process flow for electroless tin deposition using the DODUSTAN process"/><!--(Fig. 7.4)-->) . The tin coatings produced in that way, even under usually unfavorable conditions of copper concentrations of 7 g/l in the electrolyte, are well solderable.