Changes

==<!--6.1 --> Application Ranges for Switching Contacts==

===<!--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.

===<!--6.1.2 -->High Electrical Loads===At With high electric electrical loads that , as usually occur occuring in power engineering devices equipment, the switching phenomena are mostly related usually due to arc formationarcing. For most applications the management of the switching arc is the key problem. Depending on the device type , different require-ments 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.

==<!--6.2 -->Contact Materials and Design of Contact Components==The highest reliability and electrical life of electromechanical components and switching devices can only be achieved if both, the material selection and the design of the actual contact parts, are optimized. Economic Of course, economic considerations must of course also be applied when selecting the most suitable contact material and its way of application as an electrical contact. In the following <xr id="tab:Material Selection and Contact Component Design"/><!--Table 6.1 --> recommendations are made for selected application examples for contact materials and contact shape or configuration.

<figtable id="tab:Material Selection and Contact Component Design"><caption>'''<!--Table 6.1: -->Material Selection and Contact Component Design''' </caption>

|Brushes from flat rolled wire or stamped; collector hard gold electroplated or clad, or ; made from miniature profile segments

 Table 1: '''Table 6.1: Material Selection and Contact Component Design (Fortsetzung)'''

<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/SnO₂ 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 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.

<figtable id="tab:Design Technologies for Contacts"><caption>'''<!--Table 6.2: -->Design Technologies for Contacts'''</caption>

|All types of switches in the communications, automotive, or power distribution technology simple contact component, universally applied, selection through economic aspects

|All types of switches in the communications, automotive, or power engineering

|Contact parts for control functions and power engine- eringengineering; economical manufacturing at higher quantities

|Ag, Ag alloys, Ag/Ni, Ag/MeO on Cu and Cu alloy carriers, total width 10 ~ 100mm, carrier thickness 0.3 – 5 mm, Ag strip cross section from 0.3 x 3 mm2mm², strip thickn. to be < &le; carrier thickn.

|Low material transferMostly high precious contact materials, double or multi layer, Ni, Monel, or Cu alloy carrier; miniature-profile width 0.2 – 2 mm|Welded profile segments for contact parts in communication, measurement and control engineering|Manufacturing of cross-directional contact spots; most economical precious metal usage|}  Table 2: '''Design Technologies for Contacts (Fortsetzung)''' {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Contact Parts, Semi-finished Materials!Typical Contact Materials and Dimensions!Main Areas of Application!Remarks|-|Clad profiles|Ag, Ag alloys, Ag/Ni, Ag/MeO, on Cu or Cu alloy carriers, all cross-sectional areas that can be drawn or rolled; Profile width: 2 ~ 10 mm|Profile segments as contact areas for low and high voltage switching devices|More complex shapes require costly tooling|-|Sintered and infiltrated parts|W-, WC-, Mo-based materials, in almost any contact resistance, shapes|Contact parts for low and high voltage switching devices|Single parts pressing; mostly with weld resistanceprojec- tions and braze alloy coating on underside|-|Formed arc erosion parts|W/Cu infiltration materials, parts in almost any shapes|AgNi0Arcing contacts for extreme duty switching devices, i.15, Ag/SnOe. SF₂₆circuit breakers|Attachment to Cu carriers by cast-on, percussion welding, electron-beam welding; rarely by brazing|-|Low gas content contact parts|W/Cu-, WC/Ag-, CuCr-based materials, rings and discs in almost any shape|Shaped contact parts for vacuum switches (contactors, power switches, circuit breakers)|Brazing to Cu carriers requires special brazing alloys|-|Cast-on contact parts|W/NiCu cast on with Cu, shaped parts and rings up to 100 mm Ø|Arcing contacts in high voltage switchgear|Contact rivetsSeamless bond interface, carriers get hardened through subsequent forming|-|Electron-beam welded miniature profile (tape) segmentscontact parts|W/Cu on Cu or CuCrZr contact rods, tubes, tulips|Arcing contacts in high voltage circuit breakers|Seamless bond interface, withstands high mechanical and thermal stresses

|Flasher relays (automotive, > 3 Mio operations)Silver electroplating|Low material transferLayer thickness up to 20 μm, high arc erosion resistance, low contact resistancemostly on Cu and Cu alloys|PdCu15 Connecting areas and 40 (Anode) vs. AgNi0.15, AgCu3 (Cathode)no-load switching contacts in power engineering; rotary switches, Ag/ZnOsliding contacts, Ag/SnO₂connectors|Contact rivets, welded miniature profile (tape) and strip segmentsFor switching contacts only under very low loads

|Breaker points (automotive ignition)Gold electroplating|Very high arc erosion resistanceFlash plating 0.1 – 0.2 μm on Ag alloys, high switching frequencyand Cu alloys; contact layers 0.5 – 5 μm mostly with intermediate Ni layer|WContacts with low current and voltage loads, connectors, rotary and sliding switches, contact areas on printed circuit boards|Tips or discs welded to formed parts or Fe supportsFlash plating only limited effective as corrosion resistant layer on silver contacts

|Automotive horn contactsSelectively electroplated strips|High arc erosion resistance at extremely high number of switching operations|WStripe coatings: Tin plating 1- 10 μm, Ag/SnO<subplating 1 – 20 μm, Au plating 0.2 – 5 μm; stripe width 2 mm min, stripe distance >2</sub>mm; carrier material: Cu and Cu alloys, Ni alloys, stainless steel; strip thickness: 0.1 ~ 1 mm; strip width: 5 ~ 100 mm|Contact rivetsparts for connectors, W weld buttonskeyboard switches, springs or formed rotary and sliding switches; bondable areas (Au) for electronic components|Economic manufacturing for partially plated parts ; hard gold with brazed or welded tipsNi intermediate layer possible but has limited formability

|Appliance switchesSelectively electroplated pre-stamped strips, Spot gold plating|Low Continuous partial electroplating of pre-stamped and coined contact resistancespots; allprecious metals; intermediate layers of Cu or Ni; selective tinning of connector contact areas and terminal ends; carrier materials up to 1 mm thick, reasonable arc erosion and weld resistancestrip width up to ~ 80 mm|AgNi0.15Precious metal plating of switching contacts, Ag/Niconnector parts, Ag/SnO₂, (Ag/CdO)and terminal pins in the communication technology|Contact rivets, welded Crack-free and wear resistant layers possible since contact partsareas are already formed to final shape

|Temperature controllers (Thermostats)Sputtered profiles|Defined contacting point even at slow motion makeAu, high operating temperaturesAu alloys in any composition; layer thickness 0.1 – 5 μm|AgNi0.15, Ag/Ni, Ag/SnO₂Contact profiles for relays, (Ag/CdO)switches and keyboard contacts in the information and measuring technology|Contact rivets, welded High purity contact parts, weld buttonslayers for high reliability

|Wiring devices (Light switches)Hot-dip tinned strips|All around or stripe tinning 1 ~ 15 μm|Low contact resistance, reasonable arc erosion Connectors for automotive and weld resistanceconsumer technology; screw and crimp connectors|AgNi0.15, AgCu, Ag/Ni, with make peaks also Ag/ZnO, Economic coating method; does not form (Ag/CdOSn)|Contact rivets, welded contact partswhiskers

'''Table ==<!--6.2: 4-->Formulas and Design Technologies for Contacts (Fortsetzung)'''Rules==

==6.4 Formulas and Design Rules== ===<!--6.4.1 -->Definition of Terms and Symbols===

===<!--6.4.2 -->Contact Physics – Formulas===

===<!--6.4.3 -->Closed Contacts===

Fig<div class="multiple-images"> <figure id="fig:Rough flat surface">[[File:Rough flat surface. 6.5jpg|left|thumb|Figure1: Rough flat surface. a) before and b) during making contact with an ideally

contact areas (not to scale; dashed lines are elevation lines)]]</figure>

Fig. 6<figure id="fig:Contact-resistance-of-crossed-rods">[[File:Contact-resistance-of-crossed-rods.6jpg|right|thumb|Figure 2:Contact resistance of crossed rodsas a function of the contact force for gold, silverand silver-palladium alloys]]</figure></div><div class="clear"></div>

<figtable id="tab:Thermo-electrical Voltage of Contact Materials (against Copper)"><caption>'''<!--Table 6.3:-->Thermo-electrical Voltage of Contact Materials (against Copper)'''</caption> {| class="twocolortable" style="text-align: left; font-size: 12px"|-!!Contact Materials!Thermo-electric Voltage (0 - 100°C) [mV]|-|Pure metals|Ag<br />Au<br />Pt<br />Ir<br />Pd<br />Rh<br />Re<br />Cu<br />W<br />Mo| + 0.04<br />+ 0.06<br />+ 0.78<br />+ 0.13<br />+ 1.35<br />+ 0.08<br />+ 0.78<br />0<br />- 0.46<br />- 0.73|-|Alloys/Composite materials|AgCu 3<br />AgPd 30<br />AgPd 40<br />AgPd 50<br />AgPd 60<br />Ag/Ni 10<br />Ag/Ni 20<br />Ag/W 65<br />AuNi 5<br />AuAg 20<br />AuPt 10<br />PtW 5<br />Ptlr 10<br />Ptlr 20<br />PtRu 5<br />PtRu 10<br />PdCu 15<br />PdCu 40| + 0.026<br />+ 0.125<br />+ 0.198<br />+ 0.321<br />+ 0.412<br />+ 0.23<br />+ 0.27<br />+ 0.01<br />+ 4.7<br />+ 2.76<br />+ 1.11<br />+ 0.67<br />+ 0.56<br />+ 0.60<br />+ 0.32<br />+ 0.13<br />+ 0.180<br />+ 0.247|}</figtable> ===<!--6.4.4 -->Switching Contacts===

===<!--6.4.5 -->Physical Effects in Sliding and Connector Contacts===

===<!--6.4.6 -->General Rules for Dimensioning of Contacts===

===<!--6.4.7 -->Contact Spring Calculations===