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Besides manufacturing contact materials from the solid phase, i.e. by melt or powder metallurgy, the production starting in the liquid or gaseous phase is generally preferred when thin layers in the μm range are required which cannot be obtained economically by conventional cladding methods <xr id="tab:Overview_of_Important_Properties_of_Electroplated_Coatings_and_their_Applications"/> <!--(Tab. 7.1)-->. Such coatings fulfill different requirements depending on their composition and thickness.
They can serve as corrosion or wear protection or can fulfill the need for thin contact layers for certain technical applications. In addition they serve for decorative purposes as a pleasing and wear resistant surface coating.
<figtable id="tab:Overview_of_Important_Properties_of_Electroplated_Coatings_and_their_Applications">
<caption>'''<!--Table 7.1: -->Overview of Important Properties of Electroplated Coatings and their Applications'''</caption>
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Main Articel: [[Electroplating (or Galvanic Deposition)| Electroplating (or Galvanic Deposition)]]
===<!--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.
Main Articel: [[Electroless Plating| Electroless Plating]]
==<!--7.2 -->Coatings from the Gaseous Phase (Vacuum Deposition)==The term PVD (physical vapor deposition) defines processes of metal, metal alloys, and chemical compounds deposition in a vacuum by adding thermal and kinetic energy through particle bombardment. The main processes are the following four coating variations <xr id="tab:Characteristics of the Most Important PVD Processes"/> <!--(Table 7.6)-->:
*Vapor deposition
<figtable id="tab:Characteristics of the Most Important PVD Processes">
<caption>'''<!--Table 7.6: -->Characteristics of the Most Important PVD Processes'''</caption>
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The sputtering process has gained the economically most significant usage. Its process principle is illustrated in <xr id="fig:Principle of sputtering"/> <!--(Fig. 7.5)-->.
<figure id="fig:Principle of sputtering">
These quality tests are performed according to industry standards, internal standards, and customer specifications resp.
==<!--7.3 -->Comparison of Deposition Processes==The individual deposition processes have in part different performance characteristics. For each end application the optimal process has to be chosen considering all technical and economical factors. The main selection criteria should be based on the electrical and mechanical requirements for the contact layer and on the design characteristics of the contact component. <xr id="tab:Comparison of different coating processes"/> <!--Table 7.7 --> gives some indications for a comparative evaluation of the different coating processes.
The electroless metal coating is not covered here because of the low thickness of deposits which makes them in most cases not suitable for contact
<figtable id="tab:Comparison of different coating processes">
<caption>'''<!--Table 7.7: -->Comparison of different coating processes'''</caption>
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The properties of the coatings are closely related to the coating process. Starting materials for cladding and sputtering targets precious metals and their alloys which in the case of gold and palladium based materials are vacuum melted and therefore exhibit a very high purity. During electroplating, depending on the type of electrolytes and the deposition parameters, some electrolyte components such as carbon and organic compounds are incorporated into the precious metal coating. Layers deposited from the gaseous phase however are very pure.
==<!--7.4 -->Hot (-Dipped) Tin Coated Strip Materials==
During hot-dip tinning pre-treated strip materials are coated with pure tin or tin alloys from a liquid solder metal. During overall (or all-around) tinning the stripsthrough a liquid metal melt. For strip tinning rotating rolls are partially immersed into a liquid tin melt and transport the liquid onto the strip which is guided above them. Through special wiping and gas blowing procedures the deposited tin layer can be held within tight tolerances. Hot tinning is performed directly onto the base substrate material without any pre-coating with either copper or nickel. Special cast-on processes or the melting of solder foils onto the carrier strip allow also the production of thicker solder layers ( > 15 μm).
Quality criteria for the actual tin coatings are usually agreed upon separately.
==<!--7.5 -->Contact Lubricants==
By using suitable lubricants the mechanical wear and frictional oxidation of sliding and connector contacts can be substantially reduced. In the electrical contact technology solid, as well as high and low viscosity liquid lubricants are used.
<tr><td><p class="s8">DODUCONTA B5</p></td><td><p class="s8">Current collectors, connectors, slider switches</p></td></tr><tr><td><p class="s8">DODUCONTA B9</p></td><td><p class="s8">Wire potentiometers, slip rings, slider switches, measuring range selectors, miniature connectors</p></td></tr><tr><td><p class="s8">DODUCONTA B10</p></td><td><p class="s8">Precision wire potentiometers, miniature slip rings</p></td></tr><tr><td><p class="s8">DODUCONTA B12K</p></td><td><p class="s8">Wire potentiometers, slider switches, miniature slip rings, connectors</p></td></tr><tr><td><p class="s8">DODUCONTA B25</p></td><td><p class="s8">Current collectors, measuring range selectors, connectors</p></td></tr></table>
==<!--7.6 -->Passivation of Silver Surfaces==
The formation of silver sulfide during the shelf life of components with silver surface in sulfur containing environments can be significantly eliminated by coating them with an additional protective film layer (Passivation layer). For electrical contact use such thin layers should be chemically inert and sufficiently conductive, or be easily broken by the applied contact force.
<figure id="fig:Typical process flow for the SILVERBRITE W ATPS process">