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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.
===Contact Rivets===
====Solid Contact Rivets====
Solid contact rivets are the oldest utilized contact parts. Their manufacturingrequires a ductile contact material and is done without scrap on fully automatedspecial cold heading machines. A wire slug is cut off and the rivet head isformed by pressing and hammering. This way contact rivets with various headconfigurations such as flat, domed, spherical, or pointed can be manufactureddepending on the final application and switch or relay design.<figure id="fig:Typical Contact Shapes of Solid Contact RivetsTypical_Contact_Shapes_of_Solid_Contact_Rivets">
[[File:Ty_pical_Contact_Shapes_of_Solid_Contact_Rivets.jpg|right|thumb|Typical Contact Shapes of Solid Contact Rivets]]
</figure>
*Typical Contact Shapes of Solid Contact Rivets (<xr id="fig:Typical Contact Shapes of Solid Contact RivetsTypical_Contact_Shapes_of_Solid_Contact_Rivets"/>)
*Contact Materials <br /> Au-, AgPd-, PdCu-Alloys, Ag, AgNi 0,15 (ARGODUR-Spezial), AgCu, AgCuNi (ARGODUR 27), Ag/Ni (SINIDUR), Ag/CdO (DODURIT CdO), Ag/SnO<sub>2</sub> SISTADOX), Ag/ZnO (DODURIT ZnO),Ag/C 97/3*, Cu<br /> <span class="small"><sup>*</sup> dimensionally very limited</span>
*Dimensional Ranges (<xr id="fig:Dimensional RangesDimensional_Ranges"/>) <br /> The respective parameters cannot be chosen independently of each other. They mainly depend on the ductility of the required contact material. Before a final decision on the dimensions we recommend to consult with the contact manufacturer. <br /><figure id="fig:Dimensional RangesDimensional_Ranges">
[[File:Dimensional Ranges.jpg|right|thumb|Dimensional Ranges]]
</figure>
*Qualitätsmerkmale und Toleranzen (<xr id="fig:Qualitaetsmerkmale und ToleranzenQualitaetsmerkmale_und_Toleranzen"/>)<figure id="fig:Qualitaetsmerkmale und ToleranzenQualitaetsmerkmale_und_Toleranzen">[[File:Qualitaetsmerkmale und Toleranzen.jpg|right|thumbleft|Qualitaetsmerkmale und Toleranzen]]
</figure>
Clad rivets for which only a part of the head (composite or bimetal rivets) or also the shank end (tri-metal rivets) are composed of contact material – with the balance of the body mostly being copper – have replaced for many applications solid rivet versions because of economical considerations. The cost savings depend on the contact material and its required volume for a specific application. These composite rivets are also produced scrap-less from wire material on special machinery with two process variations utilized.
During ''cold bonding'' and heading the bond between the contact material and the copper is achieved without external heat energy by high plastic deformation at the face surfaces of the two wire segments <xr id="fig:Cold_bonding_of_bimetall_rivets"/> <!--(Fig. 3.1)-->. <figure id="fig:Cold_bonding_of_bimetall_rivets">[[File:Cold_bonding_of_bimetall_rivets.jpg|right|thumb|Cold bonding of bimetall rivets (schematic)]]</figure> The bonding pressure must be high enough to move the lattice components of the two metals within a few atom radii so that the adhesion forces between atoms become effective.
Therefore the head to shank diameter ratio of 2:1 must be closely met for a strong bond between the two metals.
For composite rivets with AgPd alloys as well as alloys on the basis of Au, Pd, and Pt the above methods cannot be used because of the very different work hardening of these materials compared to the base material copper. The starting material for such composite rivets is clad strip material from which the contact rivets are formed in multiple steps of press-forming and stamping. Similar processes are used for larger contact rivets with head diameters > 8 mm and Ag-based contact materials.
<figure id="fig:Typical_contact_shapes_for_composite_rivets">
[[File:Typical_contact_shapes_for_composite_rivets.jpg|right|thumb|Typical contact shapes for composite rivets]]
*Base materials <br /> Cu <br />
*Dimensional ranges (<xr id="fig:Dimensional_ranges"/>) <br />These parameters cannot be chosen independently of each other. They depend mainly on the mechanical properties of the contact material. Before specifying the final dimensions we recommend to consult with the contact manufacturer. <br />
<figure id="fig:Dimensional_ranges">
[[File:Dimensional_ranges.jpg|right|thumb|Dimensional ranges]]
</figure>
*Quality criteria and tolerances (<xr id="fig:Quality_criteria_and_tolerances"/>)
<figure id="fig:Quality_criteria_and_tolerances">
[[File:Quality_criteria_and_tolerances.jpg|right|thumbleft|Quality criteria and tolerances]]
</figure>
<table class="twocolortable">
<tr><th><p class="s13">Criteria</p></th><th><p class="s13">Form B Form C</p><p class="s13">Trapezoidal head, Trapezoidal head radiused flat</p></th><th><p class="s13">Suggested test</p><p class="s13">equipment</p></th></tr><tr><td><p class="s13">a) Head diameter</p><p class="s13">d<span class="s14"><sub>1 </sub> </span>[mm]</p></td><td><p class="s13">During optical measurement disregard corner radius R<span class="s14"><sub>3</sub> </span><u>+</u> 0.1</p></td><td><p class="s13">Comparator, measu-</p><p class="s13">ring microscpope</p></td></tr><tr><td><p class="s13">b) Head thickness</p><p class="s13">k [mm]</p></td><td><p class="s13">+ 0.1</p></td><td><p class="s13">Micrometer,</p><p class="s13">Dial indicator</p></td></tr><tr><td><p class="s13">c) Shank diameter</p><p class="s13">d<span class="s14"><sub>2</sub> </span>[mm]</p></td><td><p class="s13">Deviation from roundness and conical shape of</p><p class="s13">shank only within allowed diameter tolerance d<span class="s14"><sub>2</sub> </span> <u><</u> 1.5 - 0.08</p><p class="s13">d<span class="s14"><sub>2</sub> </span>> 1.5 - 0.1</p></td><td><p class="s13">Micrometer</p></td></tr><tr><td><p class="s13">d) Shank length l</p><p class="s13">[mm]</p></td><td><p class="s13">+ 0.15</p></td><td><p class="s13">Micrometer, Dial indicator, Comparator</p></td></tr><tr><td><p class="s13">e) Radius at center</p><p class="s13">of contact surface</p><p class="s13">R<span class="s14"><sub>1</sub> </span>[mm]</p></td><td><p class="s13">Form B: <u>+</u> 10%, but not below</p><p class="s15">+<span class="s13"> 0.5 mm</span></p><p class="s13">Form C: Allowable deviation from flatness: convex: within head thickness tolerance concave: 0.005 d<span class="s14">1</span></p></td><td><p class="s13">Comparator, Comparator template, Radius gage, Profile template</p></td></tr><tr><td><p class="s13">f) Radius at edge</p><p class="s13">of contact surface</p><p class="s13">R<span class="s14"><sub>2</sub> </span>[mm]</p></td><td><p class="s13">per DIN 46240: Form B and C max. 0.5 without DIN:max. 1</p></td><td><p class="s13">Profile template,</p><p class="s13">Comparator, Radius gage</p></td></tr><tr><td><p class="s13">g) Radii</p><p class="s13">R<span class="s14"><sub>3</sub> </span>and R<span class="s14"><sub>5</sub> </span>[mm]</p></td><td><p class="s13">Sligth rounding allowed</p></td><td><p class="s13">Comparator</p></td></tr><tr><td><p class="s13">h) Transition radius</p><p class="s13">head underside to shank R<span class="s14"><sub>4</sub> </span>[mm]</p></td><td><p class="s13">d<span class="s14"><sub>2</sub> </span><u><</u> 2 R<span class="s14"><sub>4</sub> </span><u><</u> 0.08 d<span class="s14"><sub>2</sub> </span>> 2 R<span class="s14"><sub>4</sub> </span><u><</u> 0.1 d<span class="s14"><sub>2</sub> </span>> 3 R<span class="s14"><sub>4</sub> </span><u><</u> 0.2</p></td><td><p class="s13">Comparator, if in doubt: micro-section</p></td></tr><tr><td><p class="s13">i) Allowed deviation from cylindrical shape</p></td><td><p class="s13">d<span class="s14"><sub>1</sub> </span> <u><</u> 4 up to 7°30’ + 2°30’</p><p class="s13">d<span class="s14"><sub>1</sub> </span>> 4 up to 10° + 5°</p></td><td><p class="s13">Comparator, Measu- ring microscope, if in doubt: microsection</p></td></tr><tr><td><p class="s13">k) Concentricity bet-</p><p class="s13">ween head and shank center line [mm]</p></td><td><p class="s13">5% of d<span class="s14"><sub>1</sub></span></p></td><td><p class="s13">Comparator,</p><p class="s13">Measuring microscope, Special turn fixture</p></td></tr><tr><td><p class="s13">l) Contact layer</p><p class="s13">thickness [mm]</p></td><td><p class="s13">In center area of 0.5 d<span class="s14"><sub>1</sub> </span>s<u>></u> nominal thickness</p><p class="s13">Remaining head area must be covered</p></td><td><p class="s13">Measuring micros- cope, Microsection</p></td></tr></table>
*Typical contact shapes of tri-metal rivets (s. Picture <xr id="Typical contact shapes of trifig:Typical_contact_shapes_of_tri-metal rivetsmetal_rivets")/><figure id="fig:Typical_contact_shapes_of_tri-metal_rivets">
[[File:Typical_contact_shapes_of_tri-metal_rivets.jpg|right|thumb|Typical contact shapes of tri-metal rivets]]
</figure>
*Contact materials <br /> Ag, AgNi 0,15 (ARGODUR), AgCu, AgCuNi (ARGODUR 27), Ag/Ni (SINIDUR), Ag/CdO (DODURIT CDO), Ag/SnO (SISTADOX), Ag/ZnO (DODURIT ZNO)<br />
*Base materials <br /> Cu <br />
*Dimensional ranges (s. Picture <xr id="Dimensional rangesfig:Dimensional_ranges2")/><figure id="fig:Dimensional_ranges2">
[[File:Dimensional_ranges2.jpg|right|thumb|Dimensional ranges]]
</figure>
*Standard values for rivet dimension
<table class="twocolortable" style="width:75%">
<tr><th>d<sub>1</sub></th><th><p class="s13">k</p></th><th><p class="s13">1</p></th><th><p class="s13">d<sub>2</sub></p></th><th><p class="s13">α</p></th><th><p class="s13">r<sub>1</sub></p></th><th><p class="s13">s<sub>1</sub></p></th><th><p class="s13">s<sub>2</sub></p></th></tr><tr><td><p class="s13">3.0</p></td><td><p class="s13">0.8</p></td><td><p class="s13">2.0</p></td><td><p class="s13">1.5</p></td><td><p class="s13">7.5°</p></td><td><p class="s13">4.0</p></td><td><p class="s13">0.4</p></td><td><p class="s13">1.0</p></td></tr><tr><td><p class="s13">4.0</p></td><td><p class="s13">1.0</p></td><td><p class="s13">2.5</p></td><td><p class="s13">2.0</p></td><td><p class="s13">7.5°</p></td><td><p class="s13">8.0</p></td><td><p class="s13">0.5</p></td><td><p class="s13">1.2</p></td></tr><tr><td><p class="s13">5.0</p></td><td><p class="s13">1.2</p></td><td><p class="s13">3.0</p></td><td><p class="s13">2.5</p></td><td><p class="s13">10°</p></td><td><p class="s13">12.0</p></td><td><p class="s13">0.6</p></td><td><p class="s13">1.4</p></td></tr></table>
==== 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.
====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.
=== 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:
*Stamping from strips and profiles
*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–metalSilver–metal oxides 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 materials <br /> Ag, AgNi 0,15 (ARGODUR Spezial), AgCu, AgCuNi (ARGODUR 27), Ag/Ni (SINIDUR), Ag/CdO (DODURIT CdO), Ag/SnO<sub>2</sub> (SISTADOX), Ag/ZnO (DODURIT ZnO), Ag/C (GRAPHOR), Ag/W (SIWODUR), Ag/WC (SIWODUR C), Ag/WC/C (SIWODUR C/C), Ag/Mo (SILMODUR), Cu/W (CUWODUR)<br />
*Typical contact shapes of tips and formed contact parts (s. Picture <xr id="Typical contact shapes of tips and formed contact partsfig:Typical_contact_shapes_of_tips_and_formed_contact_parts")/><figure id="fig:Typical_contact_shapes_of_tips_and_formed_contact_parts">
[[File:Typical_contact_shapes_of_tips_and_formed_contact_parts.jpg|right|thumb|Typical contact shapes of tips and formed contact parts]]
</figure>
*Dimensional ranges<br />Attachment Method: Welding <br />Bonding Area: approx. 5 – 25 mm<sup>2</sup><br />Attachment Method: Brazing <br />Bonding Area: > 25 mm<sup>2</sup> <br />
Because 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.
===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.
*Typical contact forms of weld buttons <xr id="fig:Typical_contact_forms_of_weld_buttons"/>
<figure id="fig:Typical_contact_forms_of_weld_buttons">
[[File:Typical_contact_forms_of_weld_buttons.jpg|right|thumb|Typical contact forms of weld buttons]]
</figure>
*Contact materials <br /> Ag, AgNi 0,15 (ARGODUR-Spezial), AgCu, AgCuNi (ARGODUR 27), Ag/Ni (SINIDUR), Ag/CdO (DODURIT CdO), Ag/SnO<sub>2</sub> (SISTADOX), Ag/ZnO (DODURIT ZnO) <br />
*Carrier materials <br />Ni, Fe, CuNi, CuNiZn et.al.<br />
*Dimensional Ranges (s. Picture <xr id="Dimensional fig:13neuDimensional -Ranges")/><figure id="fig:13neuDimensional -Ranges">
[[File:13neuDimensional -Ranges.jpg|right|thumb|Dimensional Ranges]]
</figure>*Quality criteria of standard weld buttons (s. Picture <xr id="Quality criteria of standard weld buttonsfig:16Quality_criteria_-of_standard_weld_-buttonsneu")/><figure id="fig:16Quality_criteria_-of_standard_weld_-buttonsneu">
[[File:16Quality_criteria_-of_standard_weld_-buttonsneu.jpg|right|thumb|Quality criteria of standard weld buttons]]
==References==
[[:Manufacturing Technologies for Contact Parts#References|Manufacturing Technologies for Contact Parts]]
[[de:Herstellung_von_Einzelkontakten]]
