Changes

Stamped electrical contact parts typically consist of a base carrier material towhich a contact material is attached by various methods ''<xr id="fig:Dimensional_ranges"/> (Fig. 3.17)''. They serveas the important functional components in many switching andelectromechanical devices for a broad range of electrical and electronicapplications. On the one hand they perform the mostly loss-free electricalcurrent transfer and the closing and opening of electrical circuits. In addition thecontact carriers are important mechanical design components selected to meetthe requirements on electrical, thermal, mechanical and magnetic properties.

The increasing miniaturization of electromechanical components requires eversmaller stamped parts with low dimensional tolerances. Such precisionstamped parts are needed in the automotive technology for highly reliableswitching and connector performance. In the information and data processingtechnology they transfer signals and control impulses with high reliability andserve as the interface between electronic and electrical components.

non-precious materials such as tin, nickel and copper ''<xr id="fig:Dimensional_ranges"/> (Fig. 3.17)''. For stamped parts in high volumes like those used as electrical components in automobiles the carrier material is mostly coated in a reel-to-reel process starting with either solid or pre-stamped strips (see also chapter 7.1.1.3). Frequently the prestamped strip will be used directly in further automated assembly of the finished functional component. As an alternative finished stamped parts can be electroplated using barrel and rack plating methods.

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 3.2.1). 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)''. 

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 3.3.1). 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.<figure id="fig:Examples of riveted stamped parts">

 Fig. 3.19:Examples of riveted stamped parts</figure>

material ''<xr id="fig:Examples of pre-mounted stamped component parts"/> (Fig. 3.2120?)''. 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.<figure id="fig:Examples of pre-mounted stamped component parts">

 Fig. 3.20:Examples of pre-mounted stampedcomponent parts</figure>

Modern stamping tools usually employ a modular design with integrateddimensional and functional controls ''<xr id="fig:Progressive die for stamped contact parts"/> (Fig. 3.21)''. <figure id="fig:Progressive die for stamped contact parts">

</figure>Depending on the requirements on the parts and the volumes they are built with steel or carbide (-steel) insertswhich are coated with a wear resistant material such as for example TiN forlonger life.

A special stamping process is precision stamping for contact parts made fromthin strip materials with thicknesses in the range of 0.05 – 2.5 mm. With highcapacity stamping technology up to 1400 strokes/min can be reached for highvolume parts. During the actual stamping operation frequently other processessuch as thread-forming, welding of contact segments and insertion and formingof contacts from wire segments are integrated. Depending on the productionvolumes these operations can also be performed in multiples.

The quality of the tools used for stamping, like progressive dies and stamp-formingtools is important for the final precision and consistency of the parts. During highspeed stamping the tools are exposed to extreme mechanical stresses which mustbe compensated for to ensure the highest precision over long production runs. Withsuch high quality progressive dies parts of high precision with a cutting width of lessthan the material thickness and with strict quality requirements for the cutting surfacescan be manufactured.To ensure the highest demands on the surface quality of precision contact parts quiteoften vanishing oils are used as tool lubricants. Cleaning and degreasing operationscan also be integrated into the stamping process. Additionally most stamping linesare also equipped with test stations for a 100% dimensional and surface qualitycontrol.During the design of stamping tools for electrical contacts minimizing of processscrap and the possibility to separate the precious metal containing scrap must beconsidered.