The reliability and electrical life of contact systems in switching devices as wellas in electromechanical and electronic components do not only depend on thecontact material. The selection of the most suitable carrier material also playsan important role.

The most frequently used ones are copper based materials. Depending on theapplication , also materials based on nickel or multi-layer composite materials,such as thermo bimetals for example, are frequently used. For specialapplications in the medium and high voltage technology, as well as for springsand snap discs for the information technology, iron or steel based materials areconsidered. These are however not included for the purpose of this data book.

Various requirements based on the enduse of the contact components have tobe met by carrier materials. Copper materials have to exhibit high electrical andthermal conductivity, good mechanical strength even at elevated temperatures,and in addition , a sufficient high resistance against corrosion. If used as springs, the carrier materials also must have good elastic spring properties. Besidesthese, the materials must, depending on the manufacturing processesemployed, also have good technological properties like ductility , to allow warmand cold forming, suitability for cutting and stamping, and be capable to bewelded, brazed or coated by electroplating.

===<!--5.1 -->Copper and Copper Alloys===

====5.1.1 Standards Overview====

Copper and copper alloys to be being used in electrical and electronic componentsare usually covered by national and international standards. DIN numbers thematerials by a prefix and/or a material number. The newer European standards(EN) refer to the material's usage products and also show a prefix and materialnumber. For reference , we also show in table 5.1 (<xr id="tab:MaterialDesignations"/>) the material designationaccording to UNS, the Unified Numbering System (USA). Other internationallyused standard and material numbers include, among others, those issued byCDA (Copper Development Association, USA), and GB (Guo Biao – China).

The most important EN as well as the US based and widely used ASTMstandards , covering the use of flat rolled copper and copper alloys in electricalcontacts , are:

!D e s c riptionDescription

====<!--5.1.2 -->Pure Copper====

Copper is used in electrical engineering , mostly because of its high electricalconductivity<ref>As units for electrical conductivity MS/m and m/Ω.mm² are commonly used. Frequently – and mostly in North America – the % IACS value (International Annealed Copper Standard) is also used, where 100% is equivalent to 58 MS/m or m/Ωmm² .For the description of mechanical strength properties the units of N/mm² or MPa are most commonly used:1 MS/m = 1 m/Ωmm² conductivity 1 MPa = 1 N/mm²</ref> which with 58 MS/m (or m/Ωmm²) is only slightly below that ofsilver. Other advantages of copper are its high thermal conductivity, corrosionresistance, and its good ductility. The work hardening properties of ETP copper is illustrated in (<xr id="fig:StrainHardeningStrain hardening of Cu-ETP by cold working" />). The increase in strength achieved by cold working can be reversed easily by subsequent annealing. The softening properties arestrongly dependent on the preceding cold working percentage(<xr id="fig:Softening of Cu-ETP after annealing for 3hrs after 25% cold working"/> and <xr id="fig:Softening of Cu-ETP after annealing for 3hrs after 50% cold working"/><!--5.3-->). The purity of technically pure and un-alloyed copper used for electrical applications depends on the type used and ranges between > 99.90 and 99.95wt%. The copper types are designated mainly by their oxygen content as oxygen containing, oxygen-free, and de-oxidized with phosphorus as''described in DIN EN 1652 (<xr id="figtab:SofteningOfCuMaterialDesignations"/> and <xr id="tab:Composition of Some Pure Copper Types"/><!--5.2-->). <xr id="tab:Physical Properties of Some Copper Types"/><!--Tables 5.3.--> and <xr id="tab:Mechanical Properties of Some Copper Types"/><!--5.4--> show the physical and mechanical properties of these copper materials. According to these, Cu-ETP, Cu-OFE and Cu-HCP are the types of copper for which minimum values for the electrical conductivity are guaranteed.  Cu-ETP is less suitable for welding or for brazing in reducing atmosphere because of the oxygen content (danger of hydrogen embrittlement)''. Cu-HCP, Cu-DLP, and Cu-DHP are oxygen free copper types, de-oxidized with different phosphorus contents. With increasing phosphorus content, theelectrical conductivity decreases. Cu-OFE, also called OFHC copper, is free of oxygen and also free of de-oxidizing compounds.

{|+ <caption>'''<!--Table 5.1:--> Material Designations of Some Copper Types'''</caption> <table class="twocolortable" border="1" cellspacing="0" style="border-collapse:collapse"> <tr><th>WerkstMaterialEN-Designation</th><th>EN-Number</th><th>DIN-Designation</th><th>DIN-Number</th><th>UNS</th></tr><tr><td>Cu-ETP</td><td>CW004A</td><td>E-Cu 58</td><td>2.0065</td><td>C11000</td></tr><tr><td>Cu-OF</td><td>CW008A</td><td>OF-Cu</td><td>2.0040</td><td>C10200</td></tr><tr><td>Cu-HCP</td><td>CW021A</td><td>SE-Cu</td><td>2.0070</td><td>C10300</td></tr><tr><td>Cu-DLP</td><td>CW023A</td><td>SW-Cu</td><td>2.0076</td><td>C12000</td></tr><tr><td>Cu-DHP</td><td>CW024A</td><td>F-Cu</td><td>2.0090</td><td>C12200</td></tr></table> </figtable> <div class="small">:Cu- ETP: electrolytic tough-pitch copper:Cu-OFE: Oxygen Free Electronic Copper:Cu-HCP: High Conductivity Phosphorus Deoxidized Copper:Cu-DLP: phosphorous-deoxidized copper:Cu-DHP: Phosphorous Deoxidized High Conductivity Copper</div>  <figtable id="tab:Composition of Some Pure Copper Types"><caption>'''<!--Table 5.2:-->Composition of Some Pure Copper Types'''</caption> {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Material!colspan="6" style="text-align:center"| Composition (wt%)|- !EN Designation!Cu!Bi!O!P!Pb!Others|ASTM B 534-07 |Cu-ETP|>99.90| Secbis 0. for CuCoBe0005|bis 0.040||up to 0.005|up to 0.03|-|Cu-OF|>99.95|bis 0.0005|||up to 0.005|up to 0.03|-Alloy and CuNiBe|Cu-Alloy Plate, Sheet, Strip, and Rolled BarHCP|>99.90|||ca. 0.003|||-|Cu-DLP|>99.90|bis 0.005||0.005-0.013|up to 0.005|up to 0.03|-|Cu-DHP|>99.90|||0.015-0.040||

   <figtable id="tab:Physical Properties of Some Copper Types"><caption>'''<!--Table 5.3:-->Physical Properties of Some Copper Types'''</caption> <table class="twocolortable"><tr><th><p class="s3">Material</p></th><th ><p class="s3">Density</p></th><th colspan="2"><p class="s3">Electrical</p><p class="s3">Conductivityt</p></th><th ><p class="s3">Electrical Conductivity</p></th><th><p class="s3">Thermal</p><p class="s3">Conductivity</p></th><th><p class="s3">Coeff. of</p><p class="s3">Linear Thermal Expansion</p></th><th><p class="s3">Modulus</p><p class="s3">of</p><p class="s3">Elasticity</p></th><th><p class="s3">Softening</p><p class="s3">Temperatur (approx.</p>10% loss in strength)</th><th><p class="s3">Melting</p><p class="s3">Temperature</p></th></tr><tr><th><p class="s3">EN- Designation</p></th><th >[g/cm³]</th><th>[MS/m]</th><th>[% IACS]</th><th>[μΩ· cm]</th><th>[W/(m· K)]</th><th>[10^-6/K]</th><th>[GPa]</th><th>[°C]</th><th>[°C]</th></tr><tr><td><p class="s3">Cu-ETP</p></td><td><p class="s3">8.94</p></td><td>&ge;58</td><td><p class="s3">100</p></td><td><p class="s3">1.72</p></td><td><p class="s3">390</p></td><td><p class="s3">17.7</p></td><td><p class="s3">127</p></td><td><p class="s3">ca. 220</p></td><td><p class="s3">1083</p></td></tr><tr><td><p class="s3">Cu-OF</p></td><td><p class="s3">8.94</p></td><td>&ge;58</td><td><p class="s3">100</p></td><td><p class="s3">1.72</p></td><td><p class="s3">394</p></td><td><p class="s3">17.7</p></td><td><p class="s3">127</p></td><td><p class="s3">ca. 220</p></td><td><p class="s3">1083</p></td></tr><tr><td><p class="s3">Cu-HCP</p></td><td><p class="s3">8.94</p></td><td>&ge;54</td><td><p class="s3">93</p></td><td><p class="s3">1.85</p></td><td><p class="s3">380</p></td><td><p class="s3">17.7</p></td><td><p class="s3">127</p></td><td><p class="s3">ca. 220</p></td><td><p class="s3">1083</p></td></tr><tr><td><p class="s3">Cu-DLP</p></td><td><p class="s3">8.94</p></td><td><p class="s3">52</p></td><td><p class="s3">90</p></td><td><p class="s3">1.92</p></td><td><p class="s3">350</p></td><td><p class="s3">17.7</p></td><td><p class="s3">132</p></td><td><p class="s3">ca. 220</p></td><td><p class="s3">1083</p></td></tr><tr><td><p class="s3">Cu-DHP</p></td><td><p class="s3">8.94</p></td><td>&ge;46</td><td><p class="s3">80</p></td><td><p class="s3">2.17</p></td><td><p class="s3">310</p></td><td><p class="s3">17.6</p></td><td><p class="s3">132</p></td><td><p class="s3">ca. 220</p></td><td><p class="s3">1083</p></td></tr></table></figtable>   <figtable id="tab:Mechanical Properties of Some Copper Types"><caption>'''<!--Table 5.4:-->Mechanical Properties of Some Copper Types'''</caption><table class="twocolortable" border="1" cellspacing="0" style="border-collapse:collapse"> <tr> <th><p class="s3">Material</p></th><th><p class="s3">Condition</p></th><th><p class="s3">Tensile Strength</p><p class="s3">R<span class="s11">m</span></p><p class="s3">[MPa]</p></th><th><p class="s3">0,2% Yield</p><p class="s3">Strength R<span class="s11">p0,2</span></p><p class="s3">[MPa]</p></th><th><p class="s3">Elongation</p><p class="s3">A<span class="s11">50</span></p><p class="s3">[ %]</p></th><th><p class="s3">Hardness</p><p class="s3">HV</p></th></tr><tr><td class="multirow" rowspan="4">Cu-ETP<br> Cu-OF <br> Cu-HCP <br>Cu-DLP<br> Cu-DHP</td><td>R220</td><td>220 - 260</td><td>&le;140</td><td>&ge;33</td><td>40 - 65</td></tr><tr><td>R240</td><td>240 - 300</td><td>&ge;180</td><td>&ge;8</td><td>65 - 95</td></tr><tr><td>R290</td><td>290 - 360</td><td>&ge;250</td><td>&ge;4</td><td>90 - 110</td></tr><tr><td>R360</td><td>&ge;360</td><td>&ge;320</td><td>&ge;2</td><td>&ge;110</td></tr></table></figtable> <div class="multiple-images"> <figure id="fig:StrainHardeningStrain hardening of Cu-ETP by cold working">[[File:Strain_harderingStrain hardening of Cu ETP by cold working.pngjpg|rightleft|thumb|<caption>Strain_hardening Strain hardening of Cu-ETP by cold working</caption>]]

 <figure id="fig:SofteningOfCuSoftening of Cu-ETP after annealing for 3hrs after 25% cold working">[[File:SofteningOfCuETPafterAnnealingSoftening of Cu ETP after annealing.pngjpg|rightleft|thumb|<caption>Softening of Cu-ETP after annealing for 3hrs after 25% cold working</caption>]]

Tab 5<figure id="fig:Softening of Cu-ETP after annealing for 3hrs after 50% cold working">[[File:Softening of Cu ETP after annealing 50.2jpg|left|thumb|<caption>Softening of Cu-ETP after annealing for 3hrs after 50% cold working</caption>]]</figure></div><div class="clear"></div>

Table ===<!--5.1.3: Physical Properties of Some -->High Cu Content Copper TypesAlloys===

Table The high Cu content alloy materials are closest in their properties to pure copper materials. By defined addition of small amounts of alloying elements, it is possible to increase the mechanical strength and especially the softening temperature of copper and at the same time decrease the electrical conductivity only insignificantly (<xr id="fig:Influence of small additions on the electrical conductivity of copper"/><!--(Fig. 5.4: Mechanical Properties )-->). Silver, iron, tin, zinc, nickel, chromium, zirconium, silicon and titanium are used. Usually, the additive amounts are significantly below 3 wt%. This group of materials consists of Some Copper Typesmixed crystal as well as precipitation hardening alloys. The precipitation hardening copper-beryllium and copper-chromium-zirconium materials are decribed later in a separate section.

Fig<figure id="fig:Influence of small additions on the electrical conductivity of copper">[[File:Influence of small additions on the electrical conductivity of copper. 5.1jpg|right|thumb|Figure 4:Influence of small additions on the electrical conductivity of copper]]Strain hardeningof Cu-ETP by cold working</figure>

FigFrom the large number of high-Cu alloys, only the properties of selected ones are covered here (<xr id="tab:Physical Properties of Selected High Cu Content Copper Alloys"/><!--(Tab. 5.25)--> and <xr id="tab:Softening Mechanical Properties of Selected High CuContent Copper Alloys"/><!--(Tab. 5.6)-ETPafter annealing for 3hrsafter 25% cold working->). Some of these materials are not included in the EN standards system.

FigThe low alloyed materials CuAg0. 51 and CuCd1 are mostly used as overhead drive cables, where they have to meet sustained loads at elevated temperatures without softening.3:Softening of Cu-ETPafter annealing for 3hrsafter 50% cold working

====5The materials CuFe0.1and CuSn0.15 have a high electrical conductivity. The mechanical strength of both is relatively low but stays almost constant at temperatures up to 400°C. They are used as substrates for power semiconductors and also as carriers for stationary contacts in higher energy switchgear.3 High Cu Content Copper Alloys====

The CuFe2 is a material exhibiting high Cu content alloy materials electrical conductivity and good formability. During an annealing process, Fe-rich precipitations are closest formed in their properties to pure copper materials. By defined addition of small amounts of alloying elements it is possible to increase the Cu matrix, which changes the mechanical strength and especially the softening temperature of copper and at the same time decrease properties very little but increases the electrical conductivity only insignificantly ''(Figsignificantly. 5.4)''. Silver, iron, tin, zinc, nickel, chromium, zirconium, siliconBesides being used as a contact carrier material in switching devices, this material has broader applications in automotive connectors and titanium are used. Usually the additive amounts are significantly below 3 wt%. This group of materials consists of mixed crystal as well as precipitation hardening alloys. The precipiytion hardening copper-beryllium and copper-chromium-zirconium materials are decribed later a substrate in a separate sectionthe semiconductor technology.

From CuNi2Si has high mechanical strength, good formability and at the large number same time high electrical conductivity. This combination of high-Cu alloys only the advantageous properties is achieved by a defined finely dispersed precipitation of selected ones are covered here ''(Tables 5nickel silicides.5 CuNi2Si is used mainly in the form of stamped and 5.6)''. Some of these materials are not included formed parts in the EN standards systemthermally stressed electromechanical components for automotive applications.

CuSn1CrNiTi and CuCrSiTi are advanced developments of the Cu-Cr-Ti precipitation materials with fine intermetallic dispersions. The materialCuNi1Co1Si also belongs into this family and has properties similar to the low alloyed CuBe materials CuAg0.1 and CuCd1 are mostly used as overhead drive cables where they have to meet sustained loads at elevated temperatures without softening.

The materials CuFe0.1 and CuSn0.15 have a high electrical conductivity. The mechanical strength of <br style="clear:both is relatively low but stays almost constant at temperatures up to 400°C. The are used as substrates for power semiconductors and also as carriers for stationary contacts in higher energyswitchgear.;"/>

CuFe2 is a material exhibiting high electrical conductivity and good formability<figtable id="tab:Physical Properties of Selected High Cu Content Copper Alloys"><caption>'''<!--Tab. During an annealing process Fe5.5-rich precipitations are formed in the " ->Physical Properties of Selected High Cu matrix which change the mechanical properties very little but increase the electrical conductivity significantly. Besides being used as a contact carrier material in switching devices, this material has broader applications in automotive connectors and as a substrate in the semiconductor technology.Content Copper Alloys'''</caption>

CuNi2Si has high mechanical {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Material/<br />Designation<br />EN UNS !Composition!Density<br />[g/cm³]!colspan="2" style="text-align:center"|Electrical<br />Conductivity !Electrical<br />Resistivity<br />[μΩ·cm]!Thermal<br />Conductivity<br />[W/(m·K)]!Coeff. of Linear<br />Thermal<br />Expansion<br />[10^-6/K]!Modulus of<br />Elasticity<br />[GPa]!Softening Temperature<br />(approx. 10% loss in<br />strength)<br />[°C]!Melting<br />Temp Range<br />[°C]|-!!!![MS/m] ![% IACS]!!!!!!|-|CuAg 0, good formability1<br />CW 013A|Ag 0.08-0.12<br />Cu Rest|8.89|56|97|1.8|380|17.7|126||1082|-|CuFe0, and at the same time high electrical conductivity1P<br />not standardized<br />C19210|Fe 0.05-0.015<br />P 0.025-0.04<br />Cu Rest|8.89|53|91|1.9|350|17.0|130|ca. 280|1080|-|CuSn0,15<br />CW117C<br />C14415|Sn 0.1-0.15<br />Zn 0.1<br />Cu Rest|8.93|51|88|2.0|350|18.0|130|ca. 280|1060|-|CuFe2P<br />CW107C<br />C19400|Fe 2.1-2.6<br />P 0.015-0.15<br />Zn 0.05-0.2<br />Cu Rest|8.91|37|64|2.7|260|17. This combination of advantageous properties is achieved by a defined finely dispersed precipitation of nickel silicides6|125|ca. 380|1084 - 1090|-|CuNi2Si is used mainly in the form of stamped and formed parts in thermally stressed electromechanical components for automotive applications<br />CW111C<br />C70260|Ni 1.6-2.5<br />Si 0.4-0.8<br />Fe 0.2<br />Cu Rest|8.80|23|40|4.3|200|17.0|130|ca. 430||-|CuSn1CrNiTi<br />not standardized<br />C18090|Sn 0.6<br />Ni 0.4<br />Cr 0.3<br />Ti 0.3<br />Cu Rest|8.87|35|60|2.9|240|17.6|133|ca. 480|1025 - 1074|-|CuNi1Co1Si<br />not standardized<br />C70350|Ni 1.5<br />Co 1.1<br />Si 0.6<br />Cu Rest|8.82|29|50|3.4|200|17.6|131|ca. 400||-|CuCrSiTi<br />not standardized<br />C18070|Cr 0.3<br />Ti 0.1<br />Si 0.02<br />Cu Rest|8.88|45|78|2.2|310|18.0|138|ca.430||}</figtable>

<figtable id="tab:Mechanical Properties of Selected High Cu Content Copper Alloys"><caption>'''<!--Table 5.6; :-->Mechanical Properties of Selected High Cu Content Copper Alloys (2 teile!)'''</caption>

These newer copper based materials optimize properties such as electrical conductivity{| class="twocolortable" style="text-align: left; font-size: 12px"|-!Material!Hardness<br />Condition!Tensile Strength R_m<br />[MPa]!0, mechanical strength2% YieldStrength<br />R_p02<br />[MPa]!Elongation<br />A₅₀<br />[%]!Vickers<br />Hardness<br />HV!Bend Radius¹⁾<br />perpendicular to<br />rolling direction!Bend Radius¹⁾<br />parallel to<br />rolling direction!Spring Bending<br />Limit σ_FB<br />[MPa]!Spring Fatigue<br />Limit σ_BW<br />[MPa]|-|CuAg0, and relaxation10|R 200<br />R 360|200 - 250<br />360|120<br />320|> 40<br />> 3|40<br />90|0 x t<br />0.5 x t|0 x t<br />0.5 x t|240|120|-|CuFe0, which are custom tailored to specific applications1P|R 300<br />R 360<br />R 420|300 - 380<br />360 - 440<br />420 - 500|> 260<br />> 300<br />> 350|> 10<br />> 3<br />> 2|80 - 110<br />110 - 130<br />120 - 150|0 x t<br />0.5 x t<br />1.5 x t|0 x t<br />0.5 x t<br />1. Typical uses include contact springs for relays5 x t|250|160|-|CuSn0, switches, and connectors15|R 250<br />R 300<br />R 360<br />R 420|250 - 320<br />300 - 370<br />360 - 430<br />420 - 490|> 200<br />> 250<br />> 300<br />> 350|> 9<br />> 4<br />> 3<br />> 2|60 - 90<br />85 - 110<br />105 - 130<br />120 - 140|0 x t<br />0 x t<br />0 x t<br />1 x t|0 x t<br />0 x t<br />0 x t<br />1 x t|250|160|-|CuFe2P|R 370<br />R 420<br />R 470<br />R 520|370 - 430<br />420 - 480<br />470 - 530<br />520 - 580|> 300<br />> 380<br />> 430<br />> 470|> 6<br />> 4<br />> 4<br />> 3|115 - 135<br />130 - 150<br />140 - 160<br />150 - 170|0 x t<br />0.5 x t<br />0.5 x t<br />1 x t|0 x t<br />0.5 x t<br />0.5 x t<br />1 x t|340|200|-|CuNi2Si|R 430<br />R 510<br />R 600|430 - 520<br />510 - 600<br />600 - 680|> 350<br />> 450<br />> 550|> 10<br />> 7<br />> 5|125 - 155<br />150 - 180<br />180 - 210|0 x t<br />0 x t<br />1 x t|0 x t<br />0 x t<br />1 x t|500|230|-|CuSn1CrNiTi|R 450<br />R 540<br />R 620|450 - 550<br />540 - 620<br />620 - 700|> 350<br />> 450<br />> 520|> 9<br />> 6<br />> 3|130 - 170<br />160 - 200<br />180 - 220|0.5 x t<br />1 x t<br />3 x t|0.5 x t<br />2 x t<br />6 x t|530|250|-|CuNi1Co1Si|R 800<br />R 850|> 800<br />> 850|> 760<br />> 830|> 4<br />> 1|> 260<br />> 275|0.5 x t<br />1.5 x t|1.5 x t<br />2.5 x t|||-|CuCrSiTi|R 400<br />R 460<br />R 530|400 - 480<br />460 - 540<br />530 - 610|> 300<br />> 370<br />> 460|> 8<br />> 5<br />> 2|120 - 150<br />140 - 170<br />150 - 190|0 x t<br />0.5 x t<br />1 x t|0 x t<br />0.5 x t<br />1 x t|400|220|}</figtable>¹⁾ t: Strip thickness max. 0.5 mm

FigThese newer copper based materials optimize properties, such as electrical conductivity, mechanical strength and relaxation, which are custom tailored to specific applications. 5Typical uses include contact springs for relays, switches and connectors.4:Influence of small additions on the electrical conductivity of copper

====<!--5.1.4 -->Naturally Hard Copper Alloys====

Alloys like brasses (CuZn), tin bronzes (CuSN), and German silver (CuNiZn), for which the required hardness is achieved by cold working , are defined as naturally hard alloys. Included in this group are also the silver bronzes (CuAg) with 2 – 6 wt% of Ag.

 ====<!--5.1.5 -->Other Naturally Hard Copper Alloys====

====<!--5.1.6 -->Precipitation Hardening Copper Alloys====

Besides the naturally hard copper materials , precipitation hardening copper alloys play also an important role as carrier materials for electrical contacts. By means of a suitable heat treatment , finely dispersed precipitations of a second phase can be achieved , which increase increases the mechanical strength of these copper alloys significantly.

====<!--5.1.7 Application Properties 8-->Selection Criteria for the Selection of Copper Alloys=-Based Materials===

Important for The selection of copper-based materials from the usage as spring contact components are besides mechanical strength and electrical conductivity mainly broad spectrum of available materials must be based on the typical spring properties such as requirements of the maximum spring bending limit and application. First, an application profile should be established which can be used to define the fatigue strength as well as material properties. Usually there is however no single material that can fulfill all requirements to the bendabilitysame degree. During severe thermal stressing the behavior of A compromise must be found as for example between electrical conductivity and spring materials is determined by their softening and relaxation. The following briefly describes these material properties.

Main Articel: [[Application Properties If current carrying capability is the key requirement, mechanical strength may have to be sacrificed as for example in carrier parts for stationary contacts. In this case, depending on the Selection of Copper Alloys| Application Properties current level, pure copper or low alloyed copper materials such as CuSn0.15, or for the Selection of Copper Alloys]]economic reasons CuZn30, may be suitable.

====5The increasing requirements on spring components in connectors, especially for use in automotive applications, such as higher surrounding temperatures, increased reliability and the trend towards miniaturization led to a change of materials from traditionally CuZn30 and CuSn4 to CuNiSi alloys, for example.1These CuNiSi alloys and the newer heavy duty copper alloys like CuNi1Co1, are significantly improved with regards to mechanical strength, relaxation behavior and electrical conductivity.8 Selection Criteria for Copper-Based Materials====

The selection of copper==<!-based materials from the broad spectrum of available materials must be based on the requirements of the application-5. First anapplication profile should be established which can be used to define the material properties. Usually there is however no single material that can fulfill all requirements to the same degree. A compromise must be found as for example between electrical conductivity 2-->Nickel and spring properties.Nickel Alloys==

If current carrying capability is the key requirement, mechanical strength may have to be sacrificed as for example in carrier parts for stationary contacts===<!--5. In this case, depending on the current level, pure copper or low alloyed copper materials such as CuSn0.15, or for economic reasons CuZn30, may be suitable2.1-->Technical Grade Pure Nickel===

For spring contact components the interdependent relations between electrical conductivity Technical grade pure nickel commonly contains 99.0 to 99.8 wt% Ni and fatigue strength, or electrical conductivity up to 1 wt% Co. Other ingredients are iron and relaxation behavior are manganese (<xr id="tab:Physical Properties of main importanceNickel and Nickel Alloys"/><!--(Tab. The first case is critical for higher load relay springs5. CuAg2 plays an important role for these applications21)--> and <xr id="tab:Mechanical Properties of Nickel and Nickel Alloys"/><!--(Tab. The latter is critical for components that are exposed to continuing high mechanical stresses like for example in connectors5. The spring force must stay close to constant over the expected life time of the parts even at elevated temperatures from the environment or current carrying22)-->). In this case the relaxation Work hardening and softening behavior of the copper materials which may cause a decrease nickel are shown in spring force over time must be considered[[#figures11|(Figs. 5 – 6)]]<!--Figs. 5.45 and 5. Besides this easy forming during manufacturing must be possible; this means that bending operations can also be performed at high mechanical strength values46-->.

The increasing requirements on spring components in connectorsOne of the significant properties of nickel is its modulus of elasticity, especially for use in automotive applications, such which is almost twice as high as higher surrounding that of copper. At temperaturesup to 345°C nickel is ferro-magnetic.Nickel has a high corrosion resistance, increased reliability, is very ductile and the trend towards miniaturization led easy to weld and clad. It is of great importance as a change of materials from traditionally CuZn30 and CuSn4 to CuNiSi alloys, backing material for examplemultiple layer weld profiles. These CuNiSi alloys and the newer heavy duty copper alloys like CuNi1Co1 are significantly improved with regards to mechanical strengthIn addition, relaxation behaviornickel is used as an intermediate layer for thin claddings, acting as an effective diffusion barrier between copper containing carrier materials and electrical conductivitygold or palladium-based contact materials.

<div class="multiple-images"><figure id==="fig:Strain hardening of technical pure nickel by cold working"> [[File:Strain hardening of technical pure nickel by cold working.jpg|right|thumb|Figure 5.2.1 Technical Grade Pure Nickel====: Strain hardening of technical pure nickel by cold working]]</figure>

Technical grade pure <figure id="fig:Softening of technical grad nickel after annealing for 3 hrs"> [[File:Softening of technical grad nickel commonly contains 99.0 to 99.8 wt% Ni and up to 1 wt% Coafter annealing for 3 hrs. Other ingredients are iron and manganese ''(Tables 5.21 and 5.22)''. Work hardening and softening behavior jpg|right|thumb|Figure 6: Softening of technical grad nickel are shown in Figs. 5.45 and 5.46.after annealing for 3 hrs after 50% cold working]]</figure></div><div class="clear"></div>

One of the significant properties of nickel is its modulus of elasticity which is almost twice as high as that of copper. At temperatures up to 345°C nickel is ferro===<!--magnetic5.Nickel has a high corrosion resistance, is very ductile, and easy to weld and clad2. It is of great importance as a backing material for multiple layer weld profiles. In addition nickel is used as an intermediate layers for thin claddings, acting as an effective diffusion barrier between copper containing carrier materials and goldand palladium2--based contact materials.>Nickel Alloys===

Because of the always present thin oxide layer on its surfacelow electrical conductivity, nickel NiCu30Fe is not suitable as a contact besides pure Ni and CuNi alloys the most widely used backing material for switching contactsweldable contact components. With 1 – 2 wt% additives of Fe as well as 0.5 – 1 wt% Mn and Co, the mechanical strength of the binary alloy NiCu30 can be increased.

FigThe strength values of NiCu30Fe are significantly higher than those of the copper rich CuNi alloys [[#figures12|(Figs. 7 – 8)]]<!--(Figs. 5.45:Strain hardening47 and 5.48)-->. The good spring properties and thermal stability of technical purenickel bycold workingNiCu30Fe make it a suitable material for the use as thermally stressed contact springs.

Fig. 5.46;<div class="multiple-images">Softening <figure id="fig:Strain hardening of technicalNiCu30Fe by cold working"> grad nickel after annealingfor 3 hrs after 50% [[File:Strain hardening of NiCu30Fe by cold working.jpg|right|thumb|Figure 7: Strain hardening of NiCu30Fe by cold working]]</figure>

Because <figtable id="tab:Physical Properties of its low electrical conductivity NiCu30Fe is besides pure Ni Nickel and CuNi alloys the most widely used backing material for weldable contact componentsNickel Alloys"><caption>'''<!--Table 5. With 1 – 2 wt% additives 21:-->Physical Properties of Fe as well as 0.5 – 1 wt% Mn Nickel and Co the mechanical strength of the binary alloy NiCu30 can be increased.Nickel Alloys'''</caption>

The strength values {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Material<br />Designation<br />WST-Nr.<br />EN UNS !Composition<br />[wt%]!Density<br />[g/cm³]!colspan="2" style="text-align:center"|Electrical<br />Conductivity !Electrical<br />Resistivity<br />[μΩ·cm]!Thermal<br />Conductivity<br />[W/(m·K)]!Coeff. of NiCu30Fe are significantly higher than those Linear<br />Thermal<br />Expansion<br />[10^-6/K]!Modulus of the copper rich CuNi alloys ''<br />Elasticity<br />[GPa]!Softening Temperature<br />(Figsapprox. 10% loss in<br />strength)<br />[°C]!Melting<br />Temp Range<br />[°C]|-! !!![MS/m] ![% IACS]!!!!!!|-|Ni 99,2<br />2.4066<br />17740<br />N02200<br /> <br />|Mn < 0.35<br />Cu < 0.25<br />Si < 0.25<br />Fe < 0.4<br />C < 0.01<br />Ni > 99.2|8. 9|11|19|9.0|70,5|13.0|207|ca. 450|1140|-|NiCu30Fe<br />2.4360<br />17743<br />N04400|Cu 28 - 34<br />Fe 1 - 2.47 and 5<br />Ni Rest<br />Be 1.85 - 2.05|8.8|2.1|3.6|48)''. The good spring properties and thermal stability of NiCu30Fe make it 0|22|14.0|185|ca. 420|1300 - 1350|-|NiBe2<br /> <br />N03360|Ti 0.4 - 0.6<br />Ni Rest|8.3|5.0^a|8.6|0.2^{a suitable material for the use as thermally stressed contact springs}|48|14.4|210||1380|}</figtable>

<figtable id="tab:Mechanical Properties of Nickel and Nickel Alloys"><caption>'''<!--Table 5.22: -->Mechanical Properties of Nickel and Nickel Alloys (2 Teile!)'''</caption>

Because of decreasing solubility of beryllium in nickel with decreasing temperature NiBe can be precipitation hardened similar to CuBe ''(Fig. ===<!--5.49)''. The maximum soluble amount of Be in Ni is 2.7 wt% at the eutectic temperature of 1150°C. to achieve a high hardness by precipitation hardening NiBe, similar to CuBe, is annealed at 970 3-->Nickel- 1030°C and rapidly quenched to room temperature. Soft annealed material is easily cold formed and after stamping and forming an hardening anneal is performed at 480 to 500°C for 1 to 2 hours.Beryllium Alloys===

Commercial Because of decreasing solubility of beryllium in nickel-beryllium alloys contain 2 wt% Be. Compared with decreasing temperature, NiBe can be precipitation hardened similar to CuBe2 the NiBe2 materials have a significantly higher modulus CuBe (<xr id="fig:Phase diagram of elasticity but a much lower electrical conductivity. The mechanical strength is higher than that of CuBe2 ''nickel beryllium"/><!--(Fig. 5.4049)'', -->). The maximum soluble amount of Be in Ni is 2.7 wt% at the spring bending force limit can exceed values eutectic temperature of over 1400 MPa 1150°C. To achieve a high hardness by precipitation hardening, NiBe similar to CuBe, is annealed at 970 - 1030°C and rapidly quenched to room temperature. Soft annealed material is easily cold formed and after stamping and the fatigue strength reaches approximately 400 MPaforming a hardening anneal is performed at 480 to 500°C for 1 to 2 hours.

A further advantage <figure id="fig:Phase diagram of NiBe2 is its high temperature stabilitynickel beryllium">[[File:Phase diagram of nickel beryllium. Cold worked and subsequently precipitation hardened NiBe2 can withstand sustainedtemperatures jpg|right|thumb|Figure 9: Phase diagram of 400 nickel- 650°C, depending on ist pre-treatment.beryllium]]</figure>

Similar Commercial nickel-beryllium alloys contain 2 wt% Be. Compared to CuBe CuBe2 the NiBe2 materialshave a significantly higher modulus of elasticity but a much lower electrical conductivity. The mechanical strength is higher than that of CuBe2 (<xr id="fig:Precipitation hardening of NiBe2 soft at 480C"/><!--(Fig. 5.50)-->), NiBe alloys are available in mill hardened in various conditions or also already precipitation hardened at the manufacturerspring bending force limit can exceed values of over 1400 MPa and the fatigue strength reaches approximately 400 MPa.

Nickel-beryllium alloys are recommended for mechanically and thermally highly stressed spring components. For some applications their ferro-magnetic properties can also be advantageous<figure id="fig:Precipitation hardening of NiBe2 soft at 480C">[[File:Precipitation hardening of NiBe2 soft at 480C.jpg|right|thumb|Figure 10: Precipitation hardening of NiBe2 (soft) at 480°C]]</figure>

Fig. 5A further advantage of NiBe2 is its high temperature stability.49:Cold worked and subsequently precipitation hardened, NiBe2 can withstand sustainedPhase diagram temperatures of nickel400 - 650°C, depending on ist pre-berylliumtreatment.

FigSimilar to CuBe materials, NiBe alloys are available in various mill hardened conditions or also already precipitation hardened by the manufacturer. 5.50:Precipitationhardening of NiBe2(soft) at 480°C

===<!--5.3 -->Triple-Layer Carrier Materials===

Depending on the intended application , the following layer systems are utilized:

The high electrical conductivity and good arc mobility properties of copper are combined with the mechanical strength and magnetic properties of iron or steel. The thickness and width range of material strips are the same of the ones as those for Cu – Invar – Cu system.

===5Thermostatic bimetals are composite materials, consisting of two or three layers of materials, with different coefficients of thermal expansion. They are usually bonded together by cladding. If such a material part is heated, either directly through current flow or indirectly through heat conduction or radiation, the different expansion between the active (strong expansion) and passive (low expansion) layer causes bending of the component part.4 Thermostatic Bimetals===

Thermostatic bimetals are composite materials consisting of two Directional or three layers force effects on the free end of materials with different coefficients of thermal expansion. They are usually bonded together by cladding. If such a material the thermostatic bimetal part is heated either directly through current flow then used as a trigger or indirectly through heat conduction control mechanism in thermostats, protective switches or radiation, the different expansion between in control circuits. Depending on the active (strong expansion) and passive (low expansion) layer causes bending required function of the thermostatic bimetal component part.different design shapes are used:

The wide variety of thermostatic bimetal types is specified mostly through DIN 1715 and/or applicable ASTM standards (<xr id="tab:Partial Selection from the Wide Range of Available Thermo-Bimetals"/><!--(Table 5.23)-->). The different types have varying material compositions for the active and passive side of the materials. The mostly used alloys are iron-nickel and manganese-copper-nickel. Mainly used in circuit protection switches (i.e. circuit breakers) , some thermo-bimetals include an intermediate layer of copper or nickel which allows to design parts with a closely controlled electrical resistance.  <figtable id="tab:Partial Selection from the Wide Range of Available Thermo-Bimetals"><caption>'''<!--Table 5.23:-->Partial Selection from the Wide Range of Available Thermo-Bimetals'''</caption> {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Designation<br />DIN 1715 !Designation<br />ASTM!Specific Thermal Deflection<br />[10⁶/K]!Sprecific<br />Electrical<br />Resistance k [μΩ·m]!Typical<br />Application Range [°C]!Application<br />Limit [°C]!Composition|-|TB 20110<br /> <br />TB 1577A<br /> <br />TB1170A<br /> <br /> <br />|TM 2<br />TM 8<br /> <br />TM 1<br /> <br />TM 3<br />TM 4|21.1<br />15.3<br />15.5<br />14.2<br />11.7<br />10.6<br />8.5|1.12<br />1.41<br />0.79<br />0.78<br />0.70<br />0.71<br />0.66| - 70 – + 260<br /> - 70 – + 260<br /> - 70 – + 370<br /> - 70 – + 370<br /> - 70 – + 425<br /> - 70 – + 480<br /> - 70 – + 425|350<br />350<br />450<br />450<br />480<br />540<br />540|Two components|-|TB 1517<br />TB 1511<br /> <br /> <br />TB 1303<br /> <br />TB 1109 | <br /> <br />TM 28<br />TM 26<br />TM 25<br />TM 24<br /> <br />|14.9<br />14.9<br />14.3<br />13.9<br />13.2<br />13.1<br />12.3<br />11.5|0.17<br />0.11<br />0.15<br />0.08<br />0.03<br />0.05<br />0.03<br />0.09| - 70 – + 260<br /> - 70 – + 260<br /> - 70 – + 315<br /> - 70 – + 315<br /> - 70 – + 260<br /> - 70 – + 315<br /> - 70 – + 315<br /> - 70 – + 380|400<br />400<br />350<br />350<br />300<br />350<br />350<br />400|Three components with Cu intermediale layer|-|TB 1555<br />TB 1435<br /> <br /> <br />TB 1425<br /> <br /> <br /> <br />| <br /> <br />TM 17<br />TM 15<br /> <br />TM 13<br />TM 11<br />TM 9|15.0<br />14.8<br />14.2<br />14.1<br />14.0<br />13.6<br />12.8<br />10.7|0.55<br />0.40<br />0.66<br />0.50<br />0.25<br />0.33<br />0.25<br />0.17| - 70 – + 260<br /> - 70 – + 260<br /> - 70 – + 370<br /> - 70 – + 370<br /> - 70 – + 260<br /> - 70 – + 370<br /> - 70 – + 370<br /> - 70 – + 370|450<br />450<br />480<br />480<br />450<br />480<br />480<br />480|Three components with Ni intermediale layer |}</figtable> ===<!--5.4.1-->Design Formulas=== For the design and calculation of the most important thermostatic-bimetal parts, formulas are given in (<xr id="tab:Design Formulas for Thermostatic Bimetal Components"/><!--Table 5.24-->). The necessary properties can be extracted for the most common materials from (<xr id="tab:Partial Selection from the Wide Range of Available Thermo-Bimetals"/><!--Table 5.23-->). The values given are valid only for a temperature range up to approximately 150°C. For higher temperatures; data can be obtained from the materials manufacturer.  <figtable id="tab:Design Formulas for Thermostatic Bimetal Components"><caption>'''<!--Table 5.24:-->Design Formulas for Thermostatic Bimetal Components'''</caption> {| class="twocolortable" style="font-size:1em;"|-||Shape of the Thermostatic Bimetal|Deflection|Mechanical Action Force|Thermal Action Force|-|Cantilevered strip |[[File:Contilevered strip.jpg|left|234px|]] |<math>A = \frac {\alpha \Delta TL^2}{s} </math>|<math>P = \frac {cA Bs^3}{L^3} </math>|<math>P = \frac {b \Delta T Bs^3}{L} </math>|-|Dual supported strip|[[File:Dual supported strip.jpg|left|234px|]] |<math>A = \frac {\alpha \Delta T L^2}{4s} </math>|<math>P = \frac {16c AB s^3}{L^3} </math>|<math>P = \frac {4b \Delta TB s^2}{L} </math>|-|U-shaped element |[[File:U shaped element.jpg|left|220px|]] |<math>A = \frac {\alpha \Delta T L^2}{2s} </math>|<math>P = \frac {4c AB s^3}{L^3} </math>|<math>P = \frac {2b \Delta TB s^2}{L} </math>|-|Spiral|[[File:Spiral.jpg|left|220px|]] |colspan="3" style="text-align:center"|<math>A = \frac {\alpha \Delta T}{s} (f^2 - e^2 + 4 r^2 + 2 e f + 2 \pi r f) </math>|-|Helical spring|[[File:Helical spring.jpg|left|220px|]] |<math>\alpha = \frac {\alpha_{1} \Delta TL}{s} </math>|<math>P = \frac {c_{1} \alpha Bs^3}{L \cdot r} </math>|<math>P = \frac {b_{1} \Delta TBs^2}{r} </math>|-|Disc |[[File:Disc.jpg|left|220px|]] |<math>A = \frac {\alpha \Delta T (D^2 - d^2)}{5s} </math>|<math>P = \frac {16c A s^3}{D^2 - d^2} </math>|<math>P = 3,2 b \Delta T s^2 </math>|-|Reversed strip |[[File:Reversed strip.jpg|left|240px|]] |<math>A = \frac {\alpha \Delta T}{s} (y^2 - 2xy - x^2) </math>|<math>P = \frac {c ABs^2}{L^3} </math>|<math>P = \frac {b \Delta T Bs^2}{L^3} (y^2 - 2xy - x^2) </math>|-|Reversed U-shaped element|[[File:Reserved u shaped element.jpg|left|228px|]] |colspan="3" style="text-align:center"|<math>A = \frac {\alpha \Delta T}{s} [f^2 + 4 r^2 + 2 \pi r f - (e^2 - 2ex^2 - x^2) + 2f (e - x)] </math>|}</figtable> {| style="border-spacing: 20px"|<math>A</math> || Deflection in mm |<math>B</math> || Width in mm | rowspan="2" |<math>a_{1} = \frac {360}{\pi} \cdot a</math>|- |<math>\alpha</math> || Turn angle in ° |<math>D,d</math> || Diameter in mm |-|<math>P</math> || Force in N |<math>r</math> || Radius in mm | rowspan="2" |<math>b_{1} = \frac {2}{3} \cdot b</math> |-|<math>\Delta T</math> || Temperature difference in K |<math>a</math> || Specific therm. Deflection in 1/K |-|<math>s</math> ||Thickness in mm |<math>b=ac</math> ||Thermal action force constant<math> N/(mm^2 \cdot K)</math>| rowspan="2" | <math>c_{1} = \frac {\pi}{540} \cdot c</math> |-|<math>L</math> || Free moving length in mm|<math>c</math> || Mechan. action force constant in <math>N/mm^2</math>|} ===<!--5.4.2-->Stress Force Limitations=== For all calculations according to the formulas in (<xr id="tab:Design Formulas for Thermostatic Bimetal Components"/><!--Table 5.24-->) one should check if the thermally or mechanically induced stress forces stay below the allowed bending force limit. The following formulas are applicable for calculating the allowable load (Force P_max or momentum M_max):  <table class="twocolortable" style="text-align: left; font-size:12px;width:60%"><tr><td>Single side fixed strip</td> <td><math>P_{max} < \frac {\sigma Bs^2}{6L} </math> </td></tr><tr><td>Both sides fixed strip</td><td><math>P_{max} < \frac {\sigma Bs^2}{1,5L} </math></td></tr><tr><td>Spiral or filament </td><td><math>M_{max} < \frac {\sigma Bs^2}{6} </math></td></tr><tr><td>Disc </td><td><math>P_{max} < \frac {2 \sigma s^2}{3} </math></td></tr></table> <math>\sigma</math> = bending stress ==Comments==<references/>==References== ASM Handbuch Volume 2, 10th Edition: Properties and Selection of Nonferrous Alloys and Special Purpose Materials, ASM International, Cleveland OH, USA 1990 Wieland-Kupferwerkstoffe. Wieland-Werke AG, Ulm 1999 Rau, G.: Metallische Verbundwerkstoffe. Werkstofftechnische Verlagsgesellschaft, Karlsruhe 1977 Kayser, O., Pawlek, F., Reichel, K.: Die Beeinflussung der Leitfähigkeit reinsten

Table 5Kupfers durch Beimengungen.23: Partial Selection from the Wide Range of Available ThermoMetall 8 (1954) 532-Bimetals537

====5Gerlach,U.4; Kreye, H.1 Design Formulas====: Gefüge und mechanische Eigenschaften der Legierung

For the design and calculation of the most important thermostaticCuNi9Sn2. Metall 32 (1978) 1112-bimetal parts formulas are given in Table 5.24. The necessary properties can be extracted for the most common materials from Table 5.23. The values given are valid only for a temperature range up to approximately 150°C. For higher temperatures data can be obtained from the materials manufacturer.1115

For all calculations according to the formulas in Table 5Kreye, H.24 one should check ifthe thermally or mechanically induced stress forces stay below the allowedbending force limit; Nöcker, H. The following formulas are applicable for calculating theallowable load ; Terlinde, G.: Schrumpfung und Verzug beim Aushärten von Kupfer-Beryllium-Legierungen. Metall 29 (Force P_max or momentum M_max1975):1118-1121