Changes

Very thin coating layers with tight tolerances are deposited by electroplating. For many applications, the high mechanical wear resistance is advantageous. Since even, very thin layers are mostly pore-free. These coatings also act as an effective corrosion inhibitor. The type of coatings, the sequence of multiple layers and the coating thickness, for example for connectors, are chosen according to the requirements for the end application.

For many applications, thicker precious metal surfaces or AlSi layers are necessary. These cannot be deposited by electroplating. Besides meltmetallurgically produced materials on the basis of gold, palladium and silver, also powder-metallurgical materials are required frequently. The metallurgical bond between these contact materials and the mostly copper based substrates is achieved through various mechanical cladding methods (see also chapter [[Manufacturing of Semi-Finished Materials#Clad Semi-Finished Pre-Materials (Contact-Bimetals)| Clad Semi-Finished Pre-Materials (Contact-Bimetals)]]). In this way, also aluminum clad strips are manufactured in which the aluminum layer serves as the bondable surface in the interface between electromechanical connections and electronic circuits. These clad semifinished materials can be further fabricated into pre-stamped strips, in comb form or single stamped parts (<xr id="fig:Examples of clad stamped parts"/><!--(Fig. 3.18)-->).

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Welded stamped parts can be fabricated by various methods (see also chapter [[Attachment of Single Contact Parts#Welding Processes| Welding Processes]]). Single contact pieces can be attached to pre-stamped or finished stamped strips as weld buttons and wire or profile segments by electrical resistance welding. Contact parts can also be stamped from seam-welded, semi-finished strip. Fitting the end application contact materials based on gold, palladium and silver. Depending on the contact material and the design of the finished contact component, the contact bottom surface may be consist of a weldable backing material.

Brazed stamped contact assemblies are manufactured by two joining methods (see also chapter [[Attachment of Single Contact Parts#Brazing Processes| Brazing Processes]]). The contact material is either attached by resistance or induction brazing to base metal carriers as prefabricated contact tip or they are stamped from brazed semi-finished toplay strip. It is typical for brazed contact parts, that the contact material consists of silver based contact material and a good conducting copper base material with larger cross-sectional area for the usually higher current carrying capacity.

Riveted stamped contact parts are manufactured with the use of contact rivets, which are transferred over suitable feed mechanisms correctly oriented into holes punched into the carrier (<xr id="fig:Examples of riveted stamped parts"/><!--(Fig. 3.19)-->). Frequently; also wire or wire segments resp. are used which are subsequently coined and formed into the desired contact shape (see also chapter [[Attachment of Single Contact Parts#Mechanical Attachment Processes| Mechanical Attachment Processes]]). Both attachment methods have their distinct advantages. Using composite or tri-metal rivets allows limiting the use of precious metal custom tailored to the volume needed for specific switching requirements. For wire staking, the precious metal usage is usually higher but the staking can be performed at significantly higher production rates and the additional rivet making step is eliminated.

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Components stamped parts consist of a minimum of two carrier parts which differ in their material composition and geometrical form and the contact

material (<xr id="fig:Examples of pre-mounted stamped component parts"/><!--(Fig. 3.20?)-->). The assembly of these components as single pieces or stamping progressions is performed in a stamping die by riveting or coining. To increase the current carrying capacity at the joining area, an additional welding step can be added. Depending on the requirements, the different properties of the two carrier components can be combined. As an example: the high electrical conductivity of a contact carrier blade is joined with the thermal or mechanical spring properties of a second material to form a functional component. For this process, both carrier base materials can also be coated with additional layers of other functional materials.

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