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→6.2 Contact Materials and Design of Contact Components
Table 6.1: Material Selection and Contact Component Design (Fortsetzung - 2 Teile!)
{| class="twocolortable" style="text-align: left; font-size: 12px"
|-
!Type of Contacts or Devices
!Characteristic Requirements for Contacts
!Contact Material
!Design Form of Contacts
|-
|Contacts for dry circuits
|Reliable contacting at very low currents and voltages and mostly at also<br />low contact forces
|AuAg alloys, (AuPt), Au
|Contact rivets, welded miniature profiles (tapes), electroplated Au, sputtered Au layers
|-
|Switching contacts in measuring devices
|Reliable switching at low voltages and currents at low contact forces
|Au and Pt alloys, (AgPd alloys)
|Contact rivets, welded tips, clad parts
|-
|Keyboard contacts
|Defined contacting, close to bounce-free make, high reliability at low switching loads
|Au alloys, (AgPd), Au on Ni substrate
|Au plated snap discs, Au clad wires and stamped parts, hard gold electroplated contact spots on printed circuit boards
|-
|Rotary switches on printed circuit boards
|Good frictional wear resistance, low contact résistance
|Sliding track: hard gold on Ni substrate Slider: AgPd alloy, (Hard silver)
|Electroplated coatings on slide tracks; clad, welded, or riveted stamping parts
|-
|Slip rings with high reliability
|Low and consistent contact resistance at low contact forces
|Brushes: Au alloys, AgPd, AgPdCu; Slip rings: Au alloys, Ag alloys (Rh); For higher currents: Ag/C brushes against Ag slip rings
|Brush wires, stamped brushes; solid, clad, or electroplated slip rings, Ag/C formed parts
|-
|Sliding contacts in miniature motors
|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
|Little shape changes, defined contacting at very low contact forces and high frequency of operation
|Pd alloys
|Contact rivets, contact screws, welded parts
|-
|Connectors
|Low contact resistance, corrosion resistance, sufficient frictional wear resistance, good sliding capabilities
|Ag and Au alloys, Pd, PdNi; For automotive and consumer electronic at low operation numbers: Sn and Sn alloys
|Electroplated layers or clad, often Au flash plated, mostly with Ni substrate layer, stamped parts from hot tin dipped strip
|-
|Telecommunication relays
|Reliable contacting even at high operational frequency
|Ag, AgPd, Au alloys, PdRu
|Rivets, welded profile segments
|-
|Reed relay contacts
|High reliability at low currents independent of atmospheric environment
|Au, (Rh)
|Switch paddles FeNi with partially diffused Au, (electroplated Rh)
|-
|Relays in electronic circuits
|High reliability at low switching loads and compact device design
|Au alloys, AgPd, Ag alloys
|Stamped springs from seam-welded profiles, welded miniature profile (tape) segments, contact rivets
|-
|GP relais (Elementary relays)
|Low arc erosion, high weld resistance, low and consistent contact resistance
|Ag/Ni, Ag/SnO2, (Ag/CdO), Ag/ZnO,AgNi0.15, (Ag)
|Solid and composite contact rivets, welded miniature profile (tape) segments
|-
|Automotive relays
|Low material transfer, low contact resistance, high weld resistance
|AgNi0.15, Ag/SnO2, Ag/Ni
|Contact rivets, welded miniature profile (tape) segments
|-
|Flasher relays (automotive, > 3 Mio operations)
|Low material transfer, high arc erosion resistance, low contact resistance
|PdCu15 and 40 (Anode) vs. AgNi0.15, AgCu3 (Cathode), Ag/ZnO, Ag/SnO2
|Contact rivets, welded miniature profile (tape) and strip segments
|-
|Breaker points (automotive ignition)
|Very high arc erosion resistance, high switching frequency
|W
|Tips or discs welded to formed parts or Fe supports
|-
|Automotive horn contacts
|High arc erosion resistance at extremely high number of switching operations
|W, Ag/SnO2
|Contact rivets, W weld buttons, springs or formed parts with brazed or welded tips
|-
|Appliance switches
|Low contact resistance, reasonable arc erosion and weld resistance
|AgNi0.15, Ag/Ni, Ag/SnO2, (Ag/CdO)
|Contact rivets, welded contact parts
|-
|Temperature controllers (Thermostats)
|Defined contacting point even at slow motion make, high operating temperatures
|AgNi0.15, Ag/Ni, Ag/SnO2, (Ag/CdO)
|Contact rivets, welded contact parts, weld buttons
|-
|Wiring devices (Light switches)
|Low contact resistance, reasonable arc erosion and weld resistance
|AgNi0.15, AgCu, Ag/Ni, with make peaks also Ag/ZnO, (Ag/CdO)
|Contact rivets, welded contact parts
|}
'''Notes:'''
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.
