Changes

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 material losses under electrical arcing loads <xr id="tab:Contact_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_Alloys"/><!--(Tab. 2.2)-->.

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)-->.

Caused by higher gold prices over the past years , the development of alloys with further reduced gold content had a high priority. The starting point has been the AuPd system , which has continuous solubility of the two components. Besides the binary alloy of AuPd40 and the ternary one AuPd35Ag9 , other multiple component alloys were developed. These alloys typically have < 50 wt% Au and often can be solution hardened in order to obtain even higher hardness and tensile strength. They are mostly used in sliding contact applications.

Gold alloys are used in the form of welded wire or profile (also called weldtapes), segments, contact rivets, and stampings produced from clad stripmaterials. The selection of 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.

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)-->.