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Manufacturing of Single Contact Parts

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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 Rivets~~Typical_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 Rivets~~Typical_Contact_Shapes_of_Solid_Contact_Rivets"/>)

*Contact Materials Au-, AgPd-, PdCu-Alloys, Ag, AgNi 0,15 (ARGODUR-Spezial), AgCu, AgCuNi (ARGODUR 27), Ag/Ni (SINIDUR), Ag/CdO (DODURIT CdO), Ag/SnO2 SISTADOX), Ag/ZnO (DODURIT ZnO),Ag/C 97/3*, Cu * dimensionally very limited

*Dimensional Ranges (<xr id="fig:~~Dimensional Ranges~~Dimensional_Ranges"/>) 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. <figure id="fig:~~Dimensional Ranges~~Dimensional_Ranges">

[[File:Dimensional Ranges.jpg|right|thumb|Dimensional Ranges]]

</figure>

*Qualitätsmerkmale und Toleranzen (<xr id="fig:~~Qualitaetsmerkmale und Toleranzen~~Qualitaetsmerkmale_und_Toleranzen"/>)<figure id="fig:~~Qualitaetsmerkmale und Toleranzen~~Qualitaetsmerkmale_und_Toleranzen">

[[File:Qualitaetsmerkmale und Toleranzen.jpg|left|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"/> . <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.

~~<figure id="fig:Cold_bonding_of_bimetall_rivets">[[File:Cold_bonding_of_bimetall_rivets.jpg|right|thumb|Cold bonding of bimetall rivets (schematic)]]</figure>~~During ''hot bonding'' the required heat energy is applied by a short term electrical current pulse <xr id="fig:Hot_bonding_of_bimetal_rivets"/> . <figure id="fig:Hot_bonding_of_bimetal_rivets">[[File:Hot_bonding_of_bimetal_rivets.jpg|right|thumb|Hot bonding of bimetall rivets (schematic)]]</figure> In the case of Ag and Cu a molten eutectic alloy of silver and copper is formed in the constriction area between the two wire ends. When using metal oxide containing contact materials the non-soluble oxide particles tend to coagulate and the bonding strength between the component materials is greatly reduced. Therefore the cold bonding technology is preferred for these contact materials. The during cold bonding required high surface deformation ratio can be reduced for the hot bonding process which allows the head to shank diameter ratio to be reduced below 2:1.

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:Hot_bonding_of_bimetal_rivets">[[File:Hot_bonding_of_bimetal_rivets.jpg|right|thumb|Hot bonding of bimetall rivets (schematic)]]</figure>~~*Typical contact shapes for composite rivets (<xr 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 Cu

*Dimensional ranges (<xr id="fig:Dimensional_ranges"/>) 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.

[[File:Dimensional_ranges.jpg|right|thumb|Dimensional ranges]]

</figure>

*Quality criteria and tolerances (<xr id="fig:Quality_criteria_and_tolerances"/>)

[[File:Quality_criteria_and_tolerances.jpg|left|Quality criteria and tolerances]]

<tr><th>Criteria</th><th>Form B Form CTrapezoidal head, Trapezoidal head radiused flat</th><th>Suggested testequipment</th></tr><tr><td>a) Head diameterd1 [mm]</td><td>During optical measurement disregard corner radius R3 + 0.1</td><td>Comparator, measu-ring microscpope</td></tr><tr><td>b) Head thicknessk [mm]</td><td>+ 0.1</td><td>Micrometer,Dial indicator</td></tr><tr><td>c) Shank diameterd2 [mm]</td><td>Deviation from roundness and conical shape ofshank only within allowed diameter tolerance d2 < 1.5 - 0.08d2 > 1.5 - 0.1</td><td>Micrometer</td></tr><tr><td>d) Shank length l[mm]</td><td>+ 0.15</td><td>Micrometer, Dial indicator, Comparator</td></tr><tr><td>e) Radius at centerof contact surfaceR1 [mm]</td><td>Form B: + 10%, but not below+ 0.5 mmForm C: Allowable deviation from flatness: convex: within head thickness tolerance concave: 0.005 d1</td><td>Comparator, Comparator template, Radius gage, Profile template</td></tr><tr><td>f) Radius at edgeof contact surfaceR2 [mm]</td><td>per DIN 46240: Form B and C max. 0.5 without DIN:max. 1</td><td>Profile template,Comparator, Radius gage</td></tr><tr><td>g) RadiiR3 and R5 [mm]</td><td>Sligth rounding allowed</td><td>Comparator</td></tr><tr><td>h) Transition radiushead underside to shank R4 [mm]</td><td>d2 < 2 R4 < 0.08 d2 > 2 R4 < 0.1 d2 > 3 R4 < 0.2</td><td>Comparator, if in doubt: micro-section</td></tr><tr><td>i) Allowed deviation from cylindrical shape</td><td>d1 < 4 up to 7°30’ + 2°30’d1 > 4 up to 10° + 5°</td><td>Comparator, Measu- ring microscope, if in doubt: microsection</td></tr><tr><td>k) Concentricity bet-ween head and shank center line [mm]</td><td>5% of d1</td><td>Comparator,Measuring microscope, Special turn fixture</td></tr><tr><td>l) Contact layerthickness [mm]</td><td>In center area of 0.5 d1 s> nominal thicknessRemaining head area must be covered</td><td>Measuring micros- cope, Microsection</td></tr></table>

*Typical contact shapes of tri-metal rivets (<xr 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]]

*Base materials Cu

*Dimensional ranges (<xr id="fig:Dimensional_ranges2"/>)

[[File:Dimensional_ranges2.jpg|right|thumb|Dimensional ranges]]

*Standard values for rivet dimension

==== 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 frequently used in switching devices for higher power technology. Depending on thecontact material and specified shapes these tips are produced by various manufacturing processes. The most frequently used ones are:

*Stamping from strips and profiles

*Contact materials Ag, AgNi 0,15 (ARGODUR Spezial), AgCu, AgCuNi (ARGODUR 27), Ag/Ni (SINIDUR), Ag/CdO (DODURIT CdO), Ag/SnO2 (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)

*Typical contact shapes of tips and formed contact parts (<xr 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]]

===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 buttons (<xr id="fig:Typical_contact_forms_of_weld_buttons"/>)

[[File:Typical_contact_forms_of_weld_buttons.jpg|right|thumb|Typical contact forms of weld buttons]]

*Carrier materials Ni, Fe, CuNi, CuNiZn et.al.

*Dimensional Ranges (<xr id="fig:13neuDimensional -Ranges"/>)

[[File:13neuDimensional -Ranges.jpg|right|thumb|Dimensional Ranges]]

</figure>

*Quality criteria of standard weld buttons (<xr id="fig:16Quality_criteria_-of_standard_weld_-buttonsneu"/>)

[[File:16Quality_criteria_-of_standard_weld_-buttonsneu.jpg|right|thumb|Quality criteria of standard weld buttons]]

</figure>

~~[[Category:Manufacturing Technologies for Contact Parts|Category]]~~

==References==

[[:Manufacturing Technologies for Contact Parts#References|Manufacturing Technologies for Contact Parts]]

[[de:Herstellung_von_Einzelkontakten]]

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