Pure Gold is besides Platinum the chemically most stable of all precious metals.
In its pure form it is not very suitable for use as a contact material in
electromechanical devices because of its tendency to stick and cold-weld at even
low contact forces. In addition it is not hard or strong enough to resist
mechanical wear and exhibits high materials losses under electrical arcing
loads. This limits its use in form of thin electroplated or vacuum deposited layers.
For Pure Gold is besides Platinum the chemically most electrical contact applications gold alloys are usedstable of all precious metals. Depending on thealloying metal the melting In its pure form it is performed either under in not very suitable for use as a reducing atmosphere orcontact material in a vacuum. The choice electromechanical devices because of alloying metals depends on the intended use of theresulting its tendency to stick and cold-weld at even low contact materialforces. The binary Au alloys with typically <10 wt% of otherprecious metals such as Pt, Pd, In addition it is not hard or Ag or non-precious metals like Ni, Co, strong enough to resist mechanical wear andCu are the more commonly used ones ''exhibits high material losses under electrical arcing loads (Table 2.2<xr id="tab:Contact_and_Switching_Properties_of_Gold_and_Gold_Alloys"/>)''. On one hand these alloyadditions improve the mechanical strength and electrical switching propertiesbut on the other hand reduce the electrical conductivity and chemical corrosionresistance <!--(FigTab. 2.24) to varying degrees-->. This limits its use in form of thin electroplated or vacuum deposited layers.
Under For most electrical contact applications, gold alloys are used. Depending on the aspect alloying metal, the melting is performed either under a reducing atmosphere or in a vacuum. The choice of alloying metals depends on the intended use of reducing the gold content ternary resulting contact material. The binary Au alloys with a gold contentof approximately 70 typically < 10 wt% and additions of other precious metals such as Pt, Pd, Ag and Cu or Ag and non-precious metals like Ni resp., forexample AuAg25Cu5 or AuAg20Cu10 Co and Cu are the more commonly used which exhibit for manyapplications good mechanical stability while at the same time have sufficientresistance against the formation ones (<xr id="tab:Physical Properties of corrosion layers ''Gold and Gold-Alloys"/>)<!--(Table Tab. 2.32)''-->. Other ternaryalloys based On one hand these alloy additions improve the mechanical strength and electrical switching properties but on the AuAg system are AuAg26Ni3 other hand reduce the electrical conductivity and AuAg25Pt6. These alloysare mechanically similar to the AuAgCu alloys but have significantly higheroxidation chemical corrosion resistance at elevated temperatures ''(Table <xr id="fig:Influence_of_1_10_atomic_of_different"/>)<!--(Fig. 2.42)''--> to varying degrees.
Caused by higher gold prices over Under the past years aspect of reducing the development of gold content, ternary alloys withfurther reduced a gold content had a high priority. The starting point has been theAuPd system which has continuous solubility of the two components. Besidesthe binary alloy of AuPd40 and the ternary one AuPd35Ag9 other multiplecomponent alloys were developed. These alloys typically have < 50 approximately 70 wt% Au andoften can be solution hardened in order to obtain even higher hardness additions of Ag and Cu or Ag andtensile strengthNi resp. They , for example AuAg25Cu5 or AuAg20Cu10 are mostly used in sliding contact , which exhibit for many applicationsgood mechanical stability, while at the same time have sufficient resistance against the formation of corrosion layers (<xr id="tab:Mechanical Properties of Gold and Gold-Alloys"/>)<!--(Table 2.3)-->.
<figtable id="tab:Commonly Used Grades of Gold alloys are used in the form "><caption>'''Commonly Used Grades of welded wire or profile Gold<!--(also called weldtapes2.1),segments, contact rivets, and stampings produced from clad stripmaterials. The selection of the bonding process is based on the cost for thejoining process, and most importantly on the economical aspect of using the-->'''</caption>least possible amount of the expensive precious metal component.<table class="twocolortable">
Besides being used as switching contacts in relays <tr><th><p class="s11">Designation</p></th><th><p class="s11">Composition Au</p><p class="s11">(min. content)</p></th><th><p class="s11">Impurites ppm</p></th><th><p class="s12">Remarks on forms and pushbuttonsapplication</p></th></tr><tr><td><p class="s11">Electronic Gold</p><p class="s11">Gold</p></td><td><p class="s11">99.999</p></td><td><p class="s11">Cu < 3</p><p class="s11">Ag < 3</p><p class="s11">Ca < 1</p><p class="s11">Mg <1</p><p class="s11">Fe < 1</p></td><td><p class="s12">Wires, strips, alloying metal for semiconductors, gold electronic components</p></td></tr><tr><td><p class="s11">Pure Gold</p></td><td><p class="s11">99.995</p></td><td><p class="s11">Cu < 10</p><p class="s11">Ag < 15</p><p class="s11">Ca < 20</p><p class="s11">Mg < 10</p><p class="s11">Fe < 3</p><p class="s11">Si < 10</p><p class="s11">Pb < 20</p></td><td><p class="s12">Granulate for high purity alloys are also applied in the design of connectors as well as sliding contacts forpotentiometers, sensorsstrips, tubing, slip ringsprofiles</p></td></tr><tr><td><p class="s11">Ingot Grade-Gold</p></td><td><p class="s11">99.95</p></td><td><p class="s11">Cu < 100</p><p class="s11">Ag < 150</p><p class="s11">Ca < 50</p><p class="s11">Mg < 50</p><p class="s11">Fe < 30</p><p class="s11">Si < 10</p></td><td><p class="s12">Alloys, and brushes in miniature DC motorscommonly used grade</p></td></tr></table></figtable><br/>''(Table 2.5)''.<br/>
[[File<figtable id="tab:Mechanical Physical Properties of Gold and Gold -Alloys.jpg|right|thumb|Mechanical "><caption>'''Physical Properties of Gold and Gold -Alloys]]'''</caption>
Table {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Material!Gold<br/>Content<br/>[wt.%]!Density<br/>[g/cm<sup>3</sup>]!Melting Point<br/>or Range<br/>[°C]!Electrical<br/>Resistivity<br/>[µΩ*cm]!Electrical<br/>Conductivity<br/>[MS/m]!Thermal<br/>Conductivity<br/>[W/(m*K)]!Temp. Coeff. of<br/>the electr. Resistance<br/>[10<sup>-3<sup/>/K]!Modulus of<br/>Elasticity<br/>[GPa]|-|Au (99,95)| >99,95|19,3|1064|2,32|43|317|4,0|79|-|AuAg8|92|18,1|1058|6,13|16,3|147|1,25|82|-|AuAg20|80|16,4|1035 - 1045|10,0|10|75|0,86|89|-|AuNi5|95|18,3|995 - 1018|13,5|7,4|53|0,71|83|-|AuCo5|95|18,2|1010 - 1015|55,6|1,8||0,68|88|-|AuCo5 (het.)|95|18,2|1010 - 1015|5,99|16,7||||-|AuAg25Cu5|70|15,2|950 - 980|12,2|8,2||0,75|89|-|AuAg20C10|70|15,1|865 - 895|13,3: Mechanical Properties of Gold and Gold|7,5|66|0,52|87|-|AuAg26Ni3|71|15,4|990 - 1020|11,0|9,1|59|0,88|114|-|AuPt10|90|19,5|1150 - 1190|12,5|8,0|54|||-|AuAg25Pt6|69|16,1|1060|15,9|6,3|46|0,54|93|-|AuCu14Pt9Ag4|73|16,0|955|14,3 - 25|4 - 7||||-Alloys|}</figtable>
<div class="multiple-images"><figure id="fig:Influence_of_1_10_atomic_of_different">[[File:Commonly Used Grades Influence of 1-10 atomic of Golddifferent.jpg|rightleft|thumb|Mechanical Commonly Used Grades <caption>Fig 2.2 Influence of Gold1-10 atomic% of different alloying metals on the electrical resistivity of gold (according to J. O. Linde)</caption>]]</figure></div><div class="clear"></div>
Table 2.1: Commonly Used Grades of Gold
[[File<figtable id="tab:Physical Mechanical Properties of Gold and Gold-Alloys"><caption>'''<!--Tab.jpg|right|thumb|Physical 2.3:-->Mechanical Properties of Gold and Gold-Alloys'''</caption>{| class="twocolortable" style="text-align: left; font-size: 12px"|-!Material !Hardness Condition!Tensile Strength Rm [MPa]min.!Elongation A<sub>10</sub> [%]min.!Vickers Hardness HV|-|Au|R 140<br />R 170<br />R 200<br />R 240|140<br />170<br />200<br />240|30<br />3<br />2<br />1|20<br />50<br />60<br />70|- |AuAg20|R 190<br />R 250<br />R 320<br />R 390|190<br />250<br />320<br />390|25<br />2<br />1<br />1|38<br />70<br />95<br />115|-|AuAg30|R 220<br />R 260<br />R 320<br />R 380|220<br />260<br />320<br />380|25<br />3<br />1<br />1|45<br />75<br />95<br />110|-|AuAg25Cu5|R 400<br />R 470<br />R 570<br />R 700|400<br />470<br />570<br />700|25<br />4<br />2<br />2|90<br />120<br />160<br />185|-|AuAg20Cu10|R 480<br />R 560<br />R 720<br />R 820|480<br />560<br />720<br />820|20<br />3<br />1<br />1|125<br />145<br />190<br />230|-|AuAg26Ni3|R 350<br />R 420<br />R 500<br />R 570|350<br />420<br />500<br />570|20<br />2<br />1<br />1|85<br />110<br />135<br />155|-|AuAg25Pt6|R 280<br />R 330<br />R 410<br />R 480|280<br />330<br />410<br />480|18<br />2<br />1<br />1|60<br />90<br />105<br />125|-|AuCo5|R 340<br />R 390<br />R 450<br />R 530|340<br />390<br />450<br />530|10<br />2<br />1<br />1|95<br />105<br />120<br />150|-|AuCo5 prec.hardened|heterogeneous|360|3|110-130|-|AuNi5|R 380<br />R 450<br />R 560<br />R 640|380<br />450<br />560<br />640|25<br />3<br />2<br />1|115<br />135<br />160<br />190|-|AuPt10|R 260<br />R 310<br />R 370<br />R 410|260<br />310<br />370<br />410|20<br />2<br />1<br />1|80<br />90<br />100<br />105|-|AuCu14Pt9Ag4|R 620<br />R 700<br />R 850<br />R 950<br />prec.hardened|620<br />700<br />850<br />950<br />900|20<br />3<br />2<br />1<br />3|190<br />225<br />260<br />270<br />280|}</figtable>
Other ternary alloys based on the AuAg system are AuAg26Ni3 and AuAg25Pt6. These alloys are mechanically similar to the AuAgCu alloys but have significantly higher oxidation resistance at elevated temperatures (<xr id="tab:Contact_and_Switching_Properties_of_Gold_and_Gold_Alloys"/>)<!--(Table 2.2: Physical Properties of Gold and Gold4)--Alloys>.
[[File<figtable id="tab:Influence of 1Contact_and_Switching_Properties_of_Gold_and_Gold_Alloys"><caption>'''<!--10 atomic of differentTable 2.jpg|right|thumb|Influence of 14:--10 atomic% >Contact and Switching Properties of different alloying metals on the electrical resistivity of gold (according Gold and Gold Alloys'''</caption><table class="twocolortable"> <tr><th><p class="s11">Material</p></th><th><p class="s12">Properties<th colspan="2"></p></th></tr><tr><td><p class="s11">Au</p></td><td><p class="s12">Highest corrosion resistance, low</p><p class="s12">hardness</p></td><td><p class="s12">High electr. conductivity,</p><p class="s12">strong tendency to Jcold welding</p></td></tr><tr><td><p class="s11">AuAg8</p></td><td><p class="s12">High corrosion resistance, low thermo</p><p class="s12">e. Om. Linde)]]f.</p></td><td><p class="s12">Low contact resistance</p></td></tr><tr><td><p class="s11">AuPt10</p><p class="s11">AuPd5</p></td><td><p class="s12">Very high corrosion resistance</p></td><td><p class="s12">High hardness</p></td></tr><tr><td><p class="s11">AuAg10 - 30</p></td><td><p class="s12">Mostly corrosion resistant</p></td><td><p class="s12">Higher hardness</p></td></tr><tr><td><p class="s11">AuNi5</p><p class="s11">AuCo5</p></td><td><p class="s12">High corrosion resistance, low</p><p class="s12">tendency to material transfer</p></td><td><p class="s12">High hardness</p></td></tr><tr><td><p class="s11">AuAg25Pt6</p></td><td><p class="s12">High corrosion resistance, low contact resistance</p></td><td><p class="s12">High hardness</p></td></tr><tr><td><p class="s11">AuAg26Ni3</p><p class="s11">AuAg25Cu5</p><p class="s11">AuAg20Cu10</p></td><td><p class="s12">Limited corrosion resistance</p></td><td><p class="s12">High hardness</p></td></tr><tr><td><p class="s11">AuPd40</p><p class="s11">AuPd35Ag10</p><p class="s11">AuCu14Pt9Ag4</p></td><td><p class="s12">High corrosion resistance</p></td><td><p class="s12">High hardness and mechanical</p><p class="s12">wear resistance</p></td></tr></table></figtable>
FigCaused by higher gold prices over the past years, the development of alloys with further reduced gold content had a high priority. 2The starting point has been the AuPd system, which has continuous solubility of the two components.2:Influence Besides the binary alloy of 1-10 atomicAuPd40 and the ternary one AuPd35Ag9, other multiple component alloys were developed. These alloys typically have < 50 wt% of differentalloying metals on the electrical resistivity of gold(according Au and often can be solution hardened in order to Jobtain even higher hardness and tensile strength. OThey are mostly used in sliding contact applications. Linde)
[[File:Phase diagram Gold alloys are used in the form of goldplatinumwelded wire or profile (also called weldtapes), segments, contact rivets and stampings produced from clad stripmaterials.jpg|right|thumb|Phase diagram The selection of goldplatinum]]the bonding process is based on the cost for the joining process and most importantly on the economical aspect of using the least possible amount of the expensive precious metal component.
FigBesides being used as switching contacts in relays and pushbuttons, gold alloys are also applied in the design of connectors as well as sliding contacts for potentiometers, sensors, slip rings and brushes in miniature DC motors (<xr id="tab:Application Examples and Forms of Gold and Gold Alloys"/>)<!--(Table 2. 25)-->.3:Phase diagramof goldplatinum
Fig. <figtable id="tab:Application Examples and Forms of Gold and Gold Alloys"><caption>'''<!--Table 2.45:Phase diagram-->Application Examples and Forms of gold-silverGold and Gold Alloys'''</caption>
Fig. 2.5:Phase diagram<table class="twocolortable"><tr><th><p class="s11">Material</p></th><th><p class="s12">Application Examples</p></th><th><p class="s12">Form of goldApplication</p></th></tr><tr><td><p class="s11">Pure Gold</p><p class="s11">(electroplated)</p></td><td><p class="s12">Corrosion protection layer for contact parts, stationary contacts, bonding surfaces</p></td><td><p class="s12">Electroplated coatings, bond surface layers</p></td></tr><tr><td><p class="s11">Hard Gold</p><p class="s11">(sputtered)</p></td><td><p class="s12">Contact parts for connectors and switches, sliding contact tracks, bonding surfaces</p></td><td><p class="s12">Electroplated coatings on contact rivets and stamped parts</p></td></tr><tr><td><p class="s11">Hard Gold</p><p class="s11">(sputtered)</p></td><td><p class="s12">Contacts in switches and relays for low loads, electronic signal relays</p></td><td><p class="s12">Contact surface layer on miniature</p><p class="s12">profiles (weld tapes)</p></td></tr><tr><td><p class="s11">AuAg8</p></td><td><p class="s12">Dry circuit switching contacts, electronic</p><p class="s12">signal relays</p></td><td><p class="s12">Contact rivets, welded contact</p><p class="s12">parts</p></td></tr><tr><td><p class="s11">AuAg20</p></td><td><p class="s12">Switching contacts for low loads, electronic</p><p class="s12">signal relays</p></td><td><p class="s12">Contact rivets, welded contact</p><p class="s12">parts</p></td></tr><tr><td><p class="s11">AuAg25Cu5</p><p class="s11">AuAg25Cu10</p><p class="s11">AuAg26Ni3</p></td><td><p class="s12">Contact parts for connectors, switches and relays</p></td><td><p class="s12">Claddings on Cu alloys, contact rivets, contact layer on micro profiles (weld tapes)</p></td></tr><tr><td><p class="s11">AuNi5</p><p class="s11">AuCo5 (heterogen)</p></td><td><p class="s12">Contacts in switches and relays for low and medium loads, material transfer resistant contacts</p></td><td><p class="s12">Contact rivets, welded contact parts, contact layer on miniature profiles (weld tapes)</p></td></tr><tr><td><p class="s11">AuPt10</p><p class="s11">AuAg25Pt6</p></td><td><p class="s12">Contacts for highest chemical corrosion resistance in switches and relays</p></td><td><p class="s12">Contact rivets, contact layer on micro profiles (weld tapes)</p></td></tr><tr><td><p class="s11">AuCu14Pt9Ag4</p></td><td><p class="s12">Sliding contacts for measurement data transfer</p></td><td><p class="s12">Wire-copperformed parts</p></td></tr></table></figtable>
Fig. 2.6: Phase diagram of gold-nickel
Fig. 2<div class="multiple-images"><figure id="fig:Phase diagram of goldplatinum">[[File:Phase diagram of goldplatinum.7: jpg|left|thumb|<caption>Phase diagram of gold-cobaltgoldplatinum</caption>]]</figure>
Fig. 2.8<figure id="fig:Phase diagram of gold-silver">Strain hardening[[File:Phase diagram of gold-silver.jpg|left|thumb|<caption>Phase diagram of gold-silver</caption>]]of Au by cold working</figure>
Fig. 2.9<figure id="fig:Phase diagram of gold-copper">Softening [[File:Phase diagram of Au after annealingfor 0gold-copper.5 hrs after 80%jpg|left|thumb|<caption>Phase diagram of gold-copper</caption>]]cold working</figure>
Fig. 2.10<figure id="fig:Phase diagram of gold-nickel">Strain hardening [[File:Phase diagram of gold-nickel.jpg|left|thumb|<caption>Phase diagram ofgold-nickel</caption>]]AuPt10 by cold working</figure>
Fig. 2.11<figure id="fig:Phase diagram of gold-cobalt">Strain hardening[[File:Phase diagram of gold-cobalt.jpg|left|thumb|<caption>Phase diagram of gold-cobalt</caption>]]of AuAg20 by cold working</figure>
Fig. 2.12<figure id="fig:Strain hardening of Au by cold working">[[File:Strain hardening ofAuAg30 Au by cold working.jpg|left|thumb|<caption>Strain hardening of Au by cold working</caption>]]</figure>
Fig<figure id="fig:Softening of Au after annealing for 0.5 hrs">[[File:Softening of Au after annealing for 0. 25 hrs.13:Strain hardening jpg|left|thumb|<caption>Softening of AuNi5by Au after annealing for 0.5 hrs after 80% cold working</caption>]]</figure>
Fig. 2.14<figure id="fig:Strain hardening of AuPt10 by cold working">Softening[[File:Strain hardening of AuNi5 after annealingfor 0AuPt10 by cold working.5 hrs after 80%jpg|left|thumb|<caption>Strain hardening of AuPt10 by cold working</caption>]]</figure>
Fig. 2.15<figure id="fig:Strain hardening of AuAg20 by cold working">[[File:Strain hardening of AuAg20 by cold working.jpg|left|thumb|<caption>Strain hardeningof AuCo5 AuAg20 by cold working</caption>]]</figure>
Fig. 2.16<figure id="fig:Strain hardening of AuAg30 by cold working">Precipitation [[File:Strain hardening ofAuCo5 at 400°C AuAg30 by cold working.jpg|left|thumb|<caption>Strain hardeningof AuAg30 by cold working</caption>]]temperature</figure>
Fig. 2.17<figure id="fig:Strain hardening of AuNi5 by cold working">[[File:Strain hardening of AuNi5 by cold working.jpg|left|thumb|<caption>Strain hardeningof AuAg25Pt6 AuNi5 by cold working</caption>]]</figure>
Fig<figure id="fig:Softening of AuNi5 after annealing for 0.5 hrs">[[File:Softening of AuNi5 after annealing for 0. 25 hrs.18:Strain hardeningjpg|left|thumb|<caption>Softening of AuAg26Ni3 by AuNi5 after annealing for 0.5 hrs after 80% cold working</caption>]]</figure>
Fig. 2.19<figure id="fig:Strain hardening of AuCo5 by cold working">Softening[[File:Strain hardening of AuAg26Ni3 afterannealing for 0AuCo5 by cold working.5 hrsafter 80% jpg|left|thumb|<caption>Strain hardening of AuCo5 by coldworking</caption>]]working</figure>
Fig. 2.20<figure id="fig:Precipitation hardening of AuCo5 at">Strain [[File:Precipitation hardening ofAuCo5 at.jpg|left|thumb|<caption>Precipitation hardening of AuCo5 at 400°C hardening temperature</caption>]]AuAg25Cu5by cold working</figure>
Fig. 2.21<figure id="fig:Strain hardening of AuAg25Pt6 by cold working">[[File:Strain hardening ofAuAg20Cu10AuAg25Pt6 by cold working.jpg|left|thumb|<caption>Strain hardening of AuAg25Pt6 by cold working</caption>]]</figure>
Fig. 2.22<figure id="fig:Strain hardening of AuAg26Ni3 by cold working">Softening[[File:Strain hardening of AuAg20Cu10 afterannealing for 0AuAg26Ni3 by cold working.5 hrsafter 80% jpg|left|thumb|<caption>Strain hardening of AuAg26Ni3 by cold working</caption>]]</figure>
Fig<figure id="fig:Softening of AuAg26Ni3 after annealing for 0.5-hrs">[[File:Softening of AuAg26Ni3 after annealing for 0. 25-hrs.23:Strain hardening jpg|left|thumb|<caption>Softening ofAuCu14Pt9Ag4by AuAg26Ni3 after annealing for 0.5 hrs after 80% cold working</caption>]]</figure>
Fig. 2.24<figure id="fig:Strain hardening of AuAg25Cu5 by cold working">Precipitation[[File:Strain hardening ofAuCu14Pt9Ag4at differentAuAg25Cu5 by cold working.jpg|left|thumb|<caption>Strain hardeningtemperaturesafter 50%of AuAg25Cu5 by cold working</caption>]]</figure>
Table 2<figure id="fig:Strain hardening of AuAg20Cu10 by cold working">[[File:Strain hardening of AuAg20Cu10 by cold working.4: Contact and Switching Properties jpg|left|thumb|<caption>Strain hardening of Gold and Gold AlloysAuAg20Cu10 by cold working</caption>]]</figure>
Table 2<figure id="fig:Softening of AuAg20Cu10 after annealing for 0.5 hrs">[[File:Softening of AuAg20Cu10 after annealing for 0.5 hrs.jpg|left|thumb|<caption>Softening of AuAg20Cu10 after annealing for 0.5hrs after 80% cold working</caption>]]</figure> <figure id="fig:Strain hardening of AuCu14Pt9Ag4 by cold working">[[File:Strain hardening of AuCu14Pt9Ag4 by cold working.jpg|left|thumb|<caption>Strain hardening of AuCu14Pt9Ag4 by cold working</caption>]]</figure> <figure id="fig: Application Examples and Forms Precipitation hardening of AuCu14Pt9Ag4">[[File:Precipitation hardening of AuCu14Pt9Ag4.jpg|left|thumb|<caption>Precipitation hardening of Gold and Gold AlloysAuCu14Pt9Ag4 at different hardening temperatures after 50% cold working</caption>]]</figure></div><div class="clear"></div>
==References==
[[Contact Materials for Electrical Engineering#References|References]]
[[de:Werkstoffe_auf_Gold-Basis]]
