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===7.1.2 Electroless Plating===
Electroless plating is defined as a coating process which is performed without the use of an external current source. It allows a uniform metal coating independent of the geometrical shape of the parts to be coated. Because of the very good dispersion capability of the used electrolytes also cavities and the inside of drilled holes in parts can be coated for example. In principal two different mechanisms are employed for electroless plating: processes in which the carrier material serves as a reduction agent (Immersion processes) and those in which a reduction agent is added to the electrolyte (Electroless processes).
====7.1.2.2 Immersion Processes====
The immersion processes are usually applied in the plating of the metals gold, silver, and tin. If the material to be coated is less precious, i.e. exhibits a negative standard potential against the metal ions in the surrounding solution, it goes into solution releasing electrons while the more precious metal ions are reduced by absorbing electrons and being deposited on the electrode. This process can continue until the complete surface of the substrate is covered with a thin layer of the more precious metal. This limits the maximum achievable layer thickness to approx. 0.1 μm <xr id="tab:Immersion Gold Electrolytes"/> (Table 7.5).
