Changes

Semi-finished contact pre-materials can be manufactured from solid preciousmetals, precious metal alloys, or precious metal containing composite materials.They are made in wire, strip, and profile form by known processing technologiessuch as extrusion and subsequent annealing and drawing or roll-forming. Theyare supplied following the manufacturer's internal standards usually related toDIN EN specifications for copper based materials. The most important materialsare two – or multiple material layered semi-finished materials with the contactmaterial bonded in its solid phase to non-precious carriers by cladding, brazing,or welding. The contact material can also be deposited on the carrier from the

Clad materials consist of two or more layers of different materials, the contactmaterial and the carrier, which are firmly bonded to each other. Depending onthe electrical requirements the contact material is mainly an alloy of gold,palladium, or silver based while the carrier material are mainly copper alloys. Tobond these materials various technologies are utilized, the two most importantones being described in more detail below.

During ''hot cladding'', the classic process, the materials to be clad areassembled into a cladding package in block or plate form, heated to about800°C and clad (or “welded”"welded") together under high pressure ''<xr id="fig:Hot_cladding_of_pre_materials"/><!--(Fig. 3.3)''-->. At theinterface between the two materials a non-separable bond is formed by eitherdiffusion of the reaction partners or in liquid phase by forming a AgCu eutecticalloy when an additional brazing alloy foil is placed between the two materials.Further processing is done by rolling with required annealing steps betweensubsequent thickness reductions. The disadvantage of this process is theusually limited short length of final material strips. Fig. 3.3 Hot cladding of pre-materials (schematic)

In the ''<figure id="fig:Cold Rollroll-Cladding'' process the bond between the contact and carriermaterial is achieved by cold deformation cladding of > 50% in one rolling pass ''semi-finished strips (Fig. 3.4schematic)''.">The high plastic deformation causes cold welding in the boundary layer betweenthe two materials. To increase the quality and strength [[File:Cold roll-cladding of the bond a subsequentdiffusion annealing is performed in most cases. This process is most suitable forclad semi-finished strips with thin contact material layers (> 2 μm) and large striplength (> 100 mschematic). Fig. 3.4: jpg|right|thumb|Cold roll-cladding of semi-finished strips (schematic)]]</figure>

[[File:Cold roll-cladding *Typical configurations of semi-finished clad contact strips (schematic).jpg|right|thumb|Cold roll-cladding <xr id="fig:Typical configurations of semi-finished clad contact strips (schematic)]]"/>

*<figure id="fig:Typical configurations of clad contact strips">bild[[File:Typical configurations of clad contact strips.jpg|right|thumb|Typical configurations of clad contact strips]]</figure>

*Dimensions<xr id="fig:Dimensions"/>bild<figure id="fig:Dimensions">[[File:Dimensions.jpg|right|thumb|Dimensions]]</figure>When specifying the contact material layer thickness it is recommended to use theminimum required thickness.

Strength properties and dimensional tolerances of clad contact bi-metals arederived from the standards DIN EN 1652 and DIN EN 1654 for Cu alloys. Whenspecifying the width of the contact material layer it is recommended to use theminimum required value. All dimensions should be specified originating from onestrip edge.

The toplay process starts with a flat or profile – shaped contact material stripwhich is fed together with the wider non-precious carrier material and in mostcases an intermediate thin foil of brazing alloy into a induction brazing machine''<xr id="fig:Toplay brazing with an inductive heating inline equipment (schematic)"/><!--(Fig. 3.5)''-->. An evenly distributed and reliable braze joint can be achieved this waybetween contact and carrier materials. The combined material strip is rather softafter the brazing process and re-hardened during a subsequent profile rollingstep. In this way different shapes and configurations can easily be achieved.

Fig<figure id="fig:Toplay brazing with an inductive heating inline equipment (schematic)">[[File:Toplay brazing with an inductive heating inline equipment (schematic). 3.5: jpg|right|thumb|Toplay brazing with an inductive heating inline equipment (schematic)]]</figure>

*Typical configurations of toplay contact profilesbild<xr id="fig:Typical configurations of toplay contact profiles2"/>

*Quality criteria, dimensions and tolerancesbild<xr id="fig:Quality criteria dimensions and tolerances"/>

<figure id="fig:Quality criteria dimensions and tolerances">[[File:Quality criteria dimensions and tolerances.jpg|right|thumb|Quality criteria dimensions and tolerances]]</figure>Strength properties and dimensional tolerances of toplay profiles are derivedfrom the standards DIN EN 1652 and DIN EN 1654 for Cu alloys.

Seam–welding is the process by which the contact material in the form of a solidwire, narrow clad strip, or profile is attached to the carrier strip by overlapping orcontinuous weld pulses between rolling electrodes ''<xr id="fig:Seam-welding process (schematic)"/><!--(Fig. 3.6)''-->. The weld joint iscreated by simultaneous effects of heat and pressure. Except for the very smallactual weld joint area the original hardness of the carrier strip is maintainedbecause of the limited short time of the heat supply. Therefore also spring-hardbase materials can be used without loss of their mechanical strength. The use ofclad contact pre-materials and profiles allows to minimize the use of the costlyprecious metal component tailored to the need for optimum reliability over theexpected electrical life of the contact components.

*Typical configurations of seam–welded contact strips and stamped parts<xr id="fig:Typical configurations of seam-welded contact strips"/>bild<figure id="fig:Typical configurations of seam-welded contact strips">Fig[[File:Typical configurations of seam-welded contact strips. 3jpg|right|thumb|Typical configurations of seam-welded contact strips]]</figure> <figure id="fig:Seam-welding process (schematic)">[[File:Seam-welding process (schematic).6: jpg|right|thumb|Seam-welding process (schematic)]]</figure>

*Dimensions<xr id="fig:Contact Profiles Dimensions"/>bild<figure id="fig:Contact Profiles Dimensions">[[File:Contact Profiles Dimensions.jpg|right|thumb|Contact Profiles Dimensions]]</figure>

Strength properties and dimensional tolerances of toplay profiles are derived from thestandards DIN EN 1652 and DIN EN 1654 for Cu alloys..

Contact profiles span a broad range of dimensions. Width and thickness are typicallybetween 0.8 – 8.0 mm and 0.2 – 3.0 mm resp. Special configurations, often definedas miniature-profiles or even micro–profiles can have awidth < 2.0 mm.

Miniature–profiles are mostly composed of a contact-bimetal material with the contactmaterial being a precious metal alloy or composite material clad, welded or coated byelectroplating or vacuum-deposition (sputtered) onto a weldable base material. Sincethese profiles are attached to carrier strip materials usually by segment– or seam–welding to the base materials, materials with good welding properties such as nickel,copper-nickel, copper-tin, as well as copper-nickel-zinc alloys are used. The bottomsurface of the profiles usually has formed weld rails or similar patterns to ensure asolid continuous metallurgical weld joint between the profile and the contact carrier.

Contact profiles in larger sizes are often used for switching devices in the low voltagetechnology. For these the contact layer mostly consists of arc erosion resistantmaterials such as silver–nickel, silver–metal oxides or the weld resistant silver–graphite. The brazable or weldable underside of the metal oxide or silver–graphitematerials is usually pure silver with also quite often a thin layer of a phosphorouscontaining brazing alloy applied to aid the welding process.

*Typical configurations of multi-layer contact profiles<xr id="fig:Typical configurations of multi-layer contact profiles"/>bild<figure id="fig:Typical configurations of multi-layer contact profiles">[[File:Typical configurations of multi-layer contact profiles.jpg|right|thumb|Typical configurations of multi-layer contact profiles]]</figure>

*Dimensions and tolerances <br xr id="fig:Contact Profiles Dimensions and tolerances"/><figure id="fig:Contact Profiles Dimensions and tolerances">[[File:Contact Profiles Dimensions and tolerances.jpg|right|thumb|Contact Profiles Dimensions and tolerances]]</figure>The thickness of the Au top-layer, which is sputtered for example, is between 0.2 and 5 μm, depending on the requirements. Tolerance of thickness is about + &plusmn; 10%.<br />bild[[Category:Manufacturing Technologies for Contact Parts|Category]]