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→Contact Materials and Design of Contact Components
===<!--6.1.1 -->Low and Medium Electrical Loads===
Switching processes at low and medium electrical loads are experienced for example in relays and switches for the measuring technology, telecommunications, automotive usage, and appliances. The switching voltage ranges from μV to 400V with currents between μA and about 100A.
Main Article: [[Low and Medium Electrical Loads| Low and Medium Electrical Loads]]
===<!--6.1.2-->High Electrical Loads===
With high electrical loads, as usually occur occuring in power engineering equipment, the switching phenomena are usually due to arcing. For most applications the management of the switching arc is the key problem. Depending on the device type, different requirements are dominant, which influence the selection of the contact material. Similar to those in communications engineering, issues related to the switching characteristics and current path have to be considered.
Main Article: [[High Electrical Loads| High Electrical Loads]]
|Very high frictional wear resistance, sure contacting even at very low contact forces
|Ag and Au alloys, Pd alloys, Au multi component alloys
|Brushes from flat rolled wire or stamped; collector hard gold electroplated or clad, or ; made from miniature profile segments
|-
|Centrifugal controllers for small motors
|}
'''Notes:'''
<xr id="tab:Material Selection and Contact Component Design"/><!--Table 6.1--> is meant to give suggestions for the use of contact materials for the specified devices. For most of the contact materials , we deliberately did not indicate the exact composition and, as for Ag/SnO<sub>2</sub> and AgZnO, did also not include specific additives. The final material composition depends on specific design parameters of the electrical device. Advise on the special properties of specific contact materials can be found in chapter 2 [[Contact Materials for Electrical Engineering| Contact Materials for Electrical Engineering ]].
==<!--6.3-->Design Technologies for Contacts==
A multitude of technologies is available and used for the actual manufacturing of contact components (see chapter 3 [[Manufacturing Technologies for Contact Parts|Manufacturing Technologies for Contact Parts]]). The desired contact shape however , requires specific material properties like for example formability and weldability , which cannot be fulfilled by all materials in the same way. In addition , the design of the contact part must be compatible with the stresses and requirements of each switching device. The following <xr id="tab:Design Technologies for Contacts"/><!--table 6.2--> combines contact design, contact material, and specific applications.
|Contact rivets solid, inserted wire segments
|Ag, Ag alloys, Au alloys, Pd alloys, Ag/Ni, Ag/C97/3, Ag/MeO (1.2 – 8 mm Ø)
|All types of switches in the communications, automotive, or power distribution technology simple contact component, universally applied, selection through economic aspects
|Secure rivet attachment only with sufficiently thick shank (shank Ø = 1⁄2 head Ø); change-over contacts by forming secondary head from longer shanks
|-
|Contact rivets, clad (Composite Rivets)
|Ag, Ag alloys, Ag/Ni, Ag/MeO on Cu base (2 ~ 10 mm Ø)
|All types of switches in the communications, automotive, or power engineering
|Secure rivet attachment only with sufficiently thick shank (shank Ø = 1⁄2 head Ø)
|-
|Vertically welded wire segments
|Ag, Ag alloys, Ag/Ni, AgPd, Au alloys (wire 0.6 ~ 5 mm Ø)
|Contact parts for control functions and power engine- eringengineering; economical manufacturing at higher quantities
|Welding and subsequently heading or orbital forming of head shape
|-
Main Article: [[Contact Physics – Formulas| Contact Physics – Formulas]]
===<!--6.4.3-->Closed Contacts=== <xr id="fig:Rough flat surface"/><!--Fig. 6.5:--> Rough flat surface a) before and b) during making contact with an ideallysmooth flat surface; c) Schematic of the apparent, load bearing and effectivecontact areas (not to scale; dashed lines are elevation lines) <xr id="fig:Contact-resistance-of-crossed-rods"/><!--Fig. 6.6:--> Contact resistance of crossed rods as a function of the contact force for gold, silver and silver-palladium alloys
<div class="multiple-images">
<figure id="fig:Rough flat surface">
[[File:Rough flat surface.jpg|left|thumb|Figure1: Rough flat surface. a) before and b) during making contact with an ideally
smooth flat surface; c) Schematic of the apparent, load bearing and effective
contact areas (not to scale; dashed lines are elevation lines)]]
<figure id="fig:Contact-resistance-of-crossed-rods">
[[File:Contact-resistance-of-crossed-rods.jpg|leftright|thumb|Figure 2: Contact resistance of crossed rods as a function of the contact force for gold, silver and silver-palladium alloys]]
</figure>
</div>
