Besides the selection of the most suitable contact materials , the design and typeof attachment is critical for the reliability and electrical life of contactcomponents for electromechanical switching devices. The materials most important factors here are the material-saving useof high cost precious metals and the most economic economical manufacturing method forcontact parts are most important factors..

There are two basic manufacturing solutions available: One can start with singlecontact parts , such as contact rivets or tips , which then are attachedmechanically or by brazing or welding resp. to carrier parts. In the second case, a base material coated or clad with the precious contact metal - for specialapplications also clad with another non-precious material – in the form of stripsor profiles is manufactured as a semi-finished pre-material from which thecontact components are then stamped and formed. Besides mechanicalcladding other processes such as electroplating and deposition from the gasphase are utilized.Which of the following manufacturing processes is finally chosen , depends onthe final application of the contact components in their respective switchingdevices or electromechanical components. Other considerations , such as therequired number of electrical operations, the most economical use of preciousmetals and the anticipated volumes of parts are also important for the processselection.

===3.1 Manufacturing of Single Contact Parts===The group of single contacts includes contact rivets, contact tips, and formedparts such as weld buttons. Contact spheres (or balls) are today rarely usedbecause of economical considerations.<br>Main Articel: [[Manufacturing of Single Contact Parts| Manufacturing of Single Contact Parts]]

==Manufacturing of Semi-Finished Materials=3=Semi-finished contact pre-materials can be manufactured from solid precious metals, precious metal alloys or precious metal containing composite materials.1.1 Contact Rivets===<br>Main Articel: [[Manufacturing of Semi-Finished Materials | Manufacturing of Semi-Finished Materials]]

==Attachment of Single Contact Parts==3.1The following segments give an overview of the usually applied attachment technologies for contact parts to carrier components.1They include mechanical, as well as brazing and welding methods used for electrical contact assemblies.1 Solid Contact Rivets===

*Typical Contact Shapes == Evaluation of Solid Contact RivetsBild*Contact MaterialsBild*Dimensional RangesBildBraze or Weld Joints==The respective parameters cannot be chosen independently switching properties of each other.They mainly depend brazed and welded contact assemblies is strongly dependent on the ductility quality of the required joint between the contact materialand the carrier. Before afinal decision on the dimensions we recommend to consult with the contactmanufacturerThe required high quality is evaluated through optical methods, continuous control of relevant process parameters and by sampling of finished products.

===3.1.1.2 Composite Stamped Contact Rivets=Parts==Clad rivets for Stamped electrical contact parts typically consist of a base carrier material to which only a part of the head contact material is attached by various methods (<xr id="fig:Plated and contact containing pre-stamped strips and stamped parts"/><!--(composite or bimetal rivetsFig. 3.17) or also-->). They serve as the shank end (tri-metal rivets) are composed important functional components in many switching and electromechanical devices for a broad range of contact material – with electrical and electronicapplications. On thebalance of one hand, they perform the body mostly being copper – have replaced for many applicationssolid rivet versions because loss-free electrical current transfer and the closing and opening of economical considerations. The cost savingsdepend electrical circuits, while on the other hand, the contact material and its required volume for a specificapplication. These composite rivets carriers are also produced scrap-less from wirematerial important mechanical design components, selected to meet the requirements on special machinery with two process variations utilizedelectrical, thermal, mechanical and magnetic properties.

During ''cold bonding'' and heading the bond between the contact material andthe copper is achieved without external heat energy by high plastic deformationat the face surfaces The increasing miniaturization of the two wire segments ''(Fig. 3.1)''electromechanical components requires ever smaller stamped parts with low dimensional tolerances. The bonding pressureSuch precisionmust be high enough to move stamped parts are needed in the lattice components of automotive technology for highly reliable switching and connector performance. In the two metals within ainformation and data processingfew atom radii so that technology, they transfer signals and control impulses with high reliability and serve as the adhesion forces interface between atoms become effectiveelectronic and electrical components.Therefore the head to shank diameter ratio of 2<figure id="fig:Plated and contact containing pre-stamped strips and stamped parts">[[File:Plated and contact containing pre-stamped strips and stamped parts.jpg|left|thumb|Figure 1 must be closely met : Plated and contact containing pre-stamped strips and stamped parts for adifferent applications]]strong bond between the two metals.</figure><br style="clear:both;"/>Main Articel: [[Stamped Contact Parts| Stamped Contact Parts]]

During ''hot bonding'' the required heat energy is applied by a short term electricalcurrent pulse ''Vinaricky, E. (Fig. 3Hrsg.2)''. In the case of Ag and Cu a molten eutectic alloy ofsilver and copper is formed in the constriction area between the two wire ends: Elektrische Kontakte, Werkstoffe und Anwendungen.When using metal oxide containing contact materials the nonSpringer-soluble oxideparticles tend to coagulate and the bonding strength between the componentmaterials is greatly reduced. Therefore the cold bonding technology is preferredfor these contact materials. The during cold bonding required high surfacedeformation ratio can be reduced for the hot bonding process which allows thehead to shank diameter ratio to be reduced below 2:1.Verlag, Heidelberg, Berlin 2002

For composite rivets with AgPd alloys as well as alloys on the basis of AuWitter, PdG., J.; Horn,G.: Contact Design and Pt the above methods cannot be used because of the very different workAttachment in: Electrical Contacts.hardening of these materials compared to the base material copperHrg. Thestarting material for such composite rivets is clad strip material from which thecontact rivets are formed in multiple steps of press-forming and stamping: Slade, P., G.Similar processes are used for larger contact rivets with head diameters > 8 mmand Ag-based contact materials, Marcel Dekker, Inc.,New York, Basel, 1999

Fig 3Mürrle, U: Löten und Schweißen elektrischer Kontakte.2In: Werkstoffe fürelektrische Kontakte und ihre Anwendungen: Hrg. Hot bonding of bimetal rivets : Schröder K.-H. u. a.;Expert-Verlag, Band 366, (schematic1997), 146 - 175

*Dimensional rangesDorn, L.: Grundlagen der Löttechnik. in: Hartlöten Grundlagen undbildThese parameters cannot be chosen independently of each otherAnwendungen. Hrsg.: Dorn, L. They dependmainly on the mechanical properties of the contact materialu. Before specifyingthe final dimensions we recommend to consult with the contact manufacturera., Expert-Verlag, Band 146 (1985) 15-40

*Typical contact shapes of triDVS-metal rivetsMerkblatt 2813: Widerstandsschweißen von elektrischen Kontakten,bildDüsseldorf: DVS-Verlag 2009

===3.1.1.3 Braze Alloy Clad Contact Rivets===For special cases, especially high surrounding temperatures with high thermaland mechanical stresses during switching operations, a full metallurgical bondbetween the contact rivet and the contact carrier may be required to prevent aloosening of the connection and early failures of the device. To accomplish thissuperior bond a thin layer of brazing alloy is added to the underside of the headand the rivet shank. During assembly a thermal treatment is added after themechanical staking. ===3.1.1.4 Contact Rivets with Brazed Contact Material Layers===For certain applications contact rivets with non-ductile or brittle materials suchas tungsten, silver–tungsten, or silver–graphite are required. Rivets with thesecontact materials can only be fabricated by brazing. Small round tips are brazedto pre-fabricated copper or steel bases using special brazing alloys in areducing atmosphere. ===3.1.2 Contact Tips===Flat or formed contact tips, welded or brazed to contact carriers, are frequentlyused in switching devices for higher power technology. Depending on thecontact material and specified shapes these tips are produced by variousmanufacturing processes. The most frequently used ones are[[de: *Stamping from strips and profiles*Cutting from extruded rods*Pressing, Sintering, and Infiltrating*Pressing, Sintering, and Re-Pressing*Pressing and Sintering For stamping sufficiently ductile semi-finished materials are needed. These aremainly silver, silver–alloys, silver–nickel, silver–metal oxide, and silver–graphite(with graphite particle orientation parallel to the switching surface). silver–metaloxides and silver–graphite need an additional well brazable or weldable silverlayer on the underside which can be bonded to the bulk of the contact materialby various processes. To further facilitate the final attachment process strips andprofiles are often coated on the brazing underside with an additional thin layer ofbrazing alloy such as L-Ag 15P (CP 102 or BCuP-5).For Ag/C with the graphite orientation perpendicular to the switching surface thebrazable underside is produced by cutting tips from extruded rods and burningout graphite in a defined thickness. The press-sinter-infiltrate process (PSI) is used mainly for Ag/W and Cu/Wmaterial tips with tungsten contents of > 50 wt%. A silver or copper surplus onthe underside of the tip later facilitates the brazing or welding during finalassembly. The press–sinter–re-press method (PSR) allows the economic manufacturing ofshaped contact parts with silver or copper contents > 70 wt%. This process alsoalloys parts pressed in two layers, with the upper being the contact material andthe bottom side consisting of pure Ag or Cu to support easy attachment. Press–sinter processes are limited to smaller Ag/W contact tips with a Agcontent of approximately 65 wt%. *Contact materialsbild *Typical contact shapes of tips and formed contact partsbild *Dimensional rangesbildBecause of the wide variety of shapes of contact tips and formed contact partsthe user and manufacturer usually develop special parts specific agreementson quality and tolerances. ===3.1.3 Weld Buttons=== For contacts used at higher temperatures, such as for example in controls forstove tops, the use of contact rivets or the direct welding of silver based contactmaterials on steel or thermo-bimetal carriers is usually not feasible. For suchapplications weld buttons are suitable contact components. Weld buttons are round or rectangular tips manufactured from clad contact bimetalor in some cases tri-metal semi-finished materials. The surface layer isproduced from the specified contact material, the bottom weldable layer from amaterial with higher electrical resistivity such as steel, nickel, or for example acopper-nickel alloy. For precious metal savings a third high conductive layer ofcopper may be inserted between the contact material and weld backing. Toimprove the welding process the underside often has an embossed pattern withone or more weld projections. The manufacturing of weld buttons from bi– or tri–metal strip requires a ductilecontact material. Weld buttons with tungsten contact layers are thereforeproduced by brazing of tungsten discs to a weldable pre-formed base. *Typical contact forms of weld buttonsbild *Contact materialsbild *Carrier materialsbild *Dimensional Rangesbild Equipment for the Production of Wires, Rivets and Miniature - Profilesbild *Quality criteria of standard weld buttonsbilder ===3.2 Manufacturing of Semi-Finished Materials===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 theliquid or vapor phase. ===3.2.1 Clad Semi-Finished Pre-Materials (Contact-Bimetals)===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”) together under high pressure ''(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 ''Cold Roll-Cladding'' process the bond between the contact and carriermaterial is achieved by cold deformation of > 50% in one rolling pass ''(Fig. 3.4)''.The high plastic deformation causes cold welding in the boundary layer betweenthe two materials. To increase the quality and strength 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 m). Fig. 3.4: Cold roll-cladding of semi-finished strips (schematic) *Typical configurations of clad contact stripsbild *Contact materialsbild *Carrier materialsbild? *DimensionsbildWhen specifying the contact material layer thickness it is recommended to use theminimum required thickness. *Quality criteria and tolerancesStrength 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. ===3.2.2 Brazed Semi-Finished Contact Materials (Toplay–Profiles)===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''(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. 3.5: Toplay brazing with an inductive heating inline equipment (schematic) *Typical configurations of toplay contact profilesbild *Contact materialsbild *Carrier materialsbild *Quality criteria, dimensions and tolerancesbild Strength properties and dimensional tolerances of toplay profiles are derivedfrom the standards DIN EN 1652 and DIN EN 1654 for Cu alloys. ===3.2.3 Seam–Welded Contact Strip Materials (FDR–Profiles)===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 ''(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 stripsand stamped partsbildFig. 3.6: Seam-welding process (schematic) *Contact materialsbild *Carrier materialsbild *Dimensionsbild *Quality criteria and tolerancesStrength properties and dimensional tolerances of toplay profiles are derived from thestandards DIN EN 1652 and DIN EN 1654 for Cu alloys.. ===3.2.4 Contact Profiles (Contact Weld Tapes)===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 profilesbild *Contact materialsbild *Carrier materialsbild *Brazing alloybild *Quality criteriaBeause of the variety of configurations of contact profiles usually the qualityissues are separately agreed upon between the manufacturer and the user. *Dimensions and tolerancesbildThe thickness of the Au top-layer, which is sputtered for example, is between 0.2and 5 μm, depending on the requirements. Tolerance of thickness is about + 10%. ===3.3 Attachment of Single Contact Parts===Technologien_für_die_Herstellung_von_Kontaktteilen]]