2,808
edits
Changes
→6.3 Design Technologies for Contacts
|Manufacturing of cross-directional contact spots; most economical precious metal usage
|}
'''Table 6.2: 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 shapes
|Contact parts for low and high voltage switching devices
|Single parts pressing; mostly with weld projec- tions and braze alloy coating on underside
|-
|Formed arc erosion parts
|W/Cu infiltration materials, parts in almost any shapes
|Arcing contacts for extreme duty switching devices, i.e. SF6 circuit 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/Cu cast on with Cu, shaped parts and rings up to 100 mm Ø
|Arcing contacts in high voltage switchgear
|Seamless bond interface, carriers get hardened through subsequent forming
|-
|Electron-beam welded contact 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
|-
|Silver electroplating
|Layer thickness up to 20 μm, mostly on Cu and Cu alloys
|Connecting areas and no-load switching contacts in power engineering; rotary switches, sliding contacts, connectors
|For switching contacts only under very low loads
|-
|Gold electroplating
|Flash plating 0.1 – 0.2 μm on Ag alloys, and Cu alloys; contact layers 0.5 – 5 μm mostly with intermediate Ni layer
|Contacts with low current and voltage loads, connectors, rotary and sliding switches, contact areas on printed circuit boards
|Flash plating only limited effective as corrosion resistant layer on silver contacts
|-
|Selectively electroplated strips
|Stripe coatings: Tin plating 1- 10 μm, Ag plating 1 – 20 μm, Au plating 0.2 – 5 μm; stripe width 2 mm min, stripe distance > 2 mm; carrier material: Cu and Cu alloys, Ni alloys, stainless steel; strip thickness: 0.1 ~ 1 mm; strip width: 5 ~ 100 mm
|Contact parts for connectors, keyboard switches, rotary and sliding switches; bondable areas (Au) for electronic components
|Economic manufacturing for partially plated parts; hard gold with Ni intermediate layer possible but has limited formability
|-
|Clad contact materials (Contact Bimetals), totally covered or with inlayed strips
|Ductile precious metals on Cu and Cu alloys, minimum precious metal layer 2% of total strip thickness for Ag and Ag alloys, 0.5% of total strip thickness for Au alloys (with Ni intermediate layer), max. inlayed thickness 50% of total, strip width starting at 2 mm
|Clad contact springs; stamped and formed parts for communications and power engineering; aluminum clad for bonding capability
|Metallurgical bond; inlayed strip stamped perpendicular or at angle to strip direction; avoid bends at the cladding edges
|-
|Strips or profiles with brazed contact material layers (Toplay material)
|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 mm<sup>2</sup>, strip thickn. to be ≤ carrier thickn.
|Stationary and moving contact bridges for power engineering switching devices
|Contact layers brazed with Ag brazing alloys; strips re-hardened during profile rolling
|-
|Seam-welded contact strips or profiles
|Wire, strip, miniature profiles (solid or clad) welded to Cu alloy carrier strip (0.3 – 3 mm Ø or up to 5 mm width)
|Switches, pushbuttons, relays, auxiliary contactors, sliding contacts
|Broad usability, highly economical, thin spring hard carriers can be used
|-
|Miniature profiles (Weld tapes)
|Mostly 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
|}
==6.4 Formulas and Design Rules==