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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 <xr id="tab:Contact and Switching Properties of Gold and Gold AlloysContact_and_Switching_Properties_of_Gold_and_Gold_Alloys"/> <!--(Tab. 2.4)-->. This limits its use in form of thin electroplated or vacuum deposited layers.
For most electrical contact applications gold alloys are used. Depending on the alloying metal the melting is performed either under in a reducing atmosphere or in a vacuum. The choice of alloying metals depends on the intended use of the resulting contact material. The binary Au alloys with typically <10 wt% of other precious metals such as Pt, Pd, or Ag or non-precious metals like Ni, Co, and Cu are the more commonly used ones <xr id="tab:Physical Properties of Gold and Gold-AlloysPhysical_Properties_of_Gold_and_Gold_Alloys"/> ''<!--(Tab. 2.2)''-->.On one hand these alloy additions improve the mechanical strength and electrical switching properties but on the other hand reduce the electrical conductivity and chemical corrosion resistance <xr id="fig:Influence of 1-10 atomic of differentInfluence_of_1_10_atomic_of_different"/> ''<!--(Fig. 2.2)'' --> to varying degrees.
Under the aspect of reducing the gold content ternary alloys with a gold content of approximately 70 wt% and additions of Ag and Cu or Ag and Ni resp., for example AuAg25Cu5 or AuAg20Cu10 are used which exhibit for many applications good 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)''-->. '''Table 2.1: Commonly Used Grades of Gold'''
<figtable id="tab:Commonly Used Grades of Gold">
<caption>'''Commonly Used Grades of Gold<!--(2.1)-->'''</caption>
<table class="twocolortable">
<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 application</p></th></tr><tr><td><p class="s11">Electronic Glod</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, 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, strips, tubing, profiles</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, commonly used grade</p></td></tr></table>
</figtable>
<div class="multiple-images">
<figtable id="tab:Physical Properties of Gold and Gold-AlloysPhysical_Properties_of_Gold_and_Gold_Alloys">
[[File:Physical Properties of Gold and Gold-Alloys.jpg|left|thumb|<caption>Tab 2.2 Physical Properties of Gold and Gold-Alloys</caption>]]
</figtable>
<figure id="fig:Influence of 1-10 atomic of differentInfluence_of_1_10_atomic_of_different">
[[File:Influence of 1-10 atomic of different.jpg|left|thumb|<caption>Fig 2.2 Influence of 1-10 atomic% of different alloying metals on the electrical resistivity of gold (according to J. O. Linde)</caption>]]
</figure>
<figtable id="tab:Mechanical Properties of Gold and Gold-Alloys">
<caption>'''<!--Tab.2.3: -->Mechanical Properties of Gold and Gold-Alloys'''</caption>
{| class="twocolortable" style="text-align: left; font-size: 12px"
|-
</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 AlloysContact_and_Switching_Properties_of_Gold_and_Gold_Alloys"/>''<!--(Table 2.4)''-->.
<figtable id="tab:Contact and Switching Properties of Gold and Gold AlloysContact_and_Switching_Properties_of_Gold_and_Gold_Alloys"><caption>'''<!--Table 2.4: -->Contact and Switching Properties of 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 cold 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.m.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>
Gold alloys are used in the form of welded wire or profile (also called weldtapes), segments, contact rivets, and stampings produced from clad strip
materials. The selection of the bonding process is based on the cost for the joining process, and most importantly on the economical aspect of using theleast possible amount of the expensive precious metal component.
Besides 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 2.5)''-->.
<figtable id="tab:Application Examples and Forms of Gold and Gold Alloys">
<caption>'''<!--Table 2.5: -->Application Examples and Forms of Gold and Gold Alloys'''</caption>
<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 Application</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-formed parts</p></td></tr></table>
</figtable>
==References==
[[Contact Materials for Electrical Engineering#References|References]]
[[de:Werkstoffe_auf_Gold-Basis]]
