Main Articel: [[Electroless Plating| Electroless Plating]]
====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 ''(Table 7.5)''.
Table 7.5: Immersion Gold Electrolytes
<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s8">Type of Electrolyte</p></td><td><p class="s8">pH-Range</p></td><td><p class="s8">Coating Properties</p></td><td><p class="s8">Application Ranges</p></td></tr><tr><td><p class="s8">Type of Electrolyte</p></td><td><p class="s8">pH-Range</p></td><td><p class="s8">Hardness</p><p class="s8">HV 0.025</p></td><td><p class="s8">Punity</p></td><td><p class="s8">Application Ranges</p></td></tr><tr><td><p class="s8">Immersion Gold electrolytes</p></td><td/><td/><td/><td/></tr><tr><td><p class="s8">AUROL 4</p><p class="s8">AUROL 16</p><p class="s8">AUROL 20</p></td><td><p class="s8">3.8 - 4.2</p><p class="s8">5.8 - 6.2</p><p class="s8">5.8 - 6.2</p><p class="s8">5.8 - 6.2</p></td><td><p class="s8">60 - 80</p><p class="s8">60 - 80</p><p class="s8">60 - 80</p><p class="s8">60 - 80</p></td><td><p class="s8">99.99% Au</p><p class="s8">99.99% Au</p><p class="s8">99.99% Au</p><p class="s8">99.99% Au</p></td><td><p class="s8">Thin gold layers on Ni, Ni alloys,</p><p class="s8">Fe and Fe alloys for PCB technology and technical applications</p></td></tr></table>
====7.1.2.3 Electroless Processes====