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→Brazing Alloys
For the joining of contact materials with carrier substrates brazing alloys with working temperatures > 600 °C are used exclusively. The working temperature is defined as the lowest surface temperature by which the brazing material wets the materials to be joined. This temperature is within the melting range and between the solidus (temperature at which melting starts) and liquidus (temperature at complete liquid state) point of the brazing alloy. Silver-based brazing alloys have good electrical conductivity and a sufficient mechanical strength which allows a bonding process without significant changes in the 4 microstructure of the material to be joined.
For electrical contacts usually low-melting alloys with a minimum of 20 wt-% silver and additions of cadmium, zinc or tin to lower the melting point are used <xr id="figtab:Commonly Used Brazing Alloys for Electrical Contacts"/> (Table 4.1). Because of the toxicity of cadmium most cadmium containing brazing alloys have been replaced by zinc and tin containing brazing alloys. For higher requirements on corrosion resistance or for easier wetting of stainless steel nickel and manganese containing alloys are also used. Using any of these brazing alloys in an air environment is only possible with the addition of oxide reducing fluxes.
<figure figtable id="figtab:Commonly Used Brazing Alloys for Electrical Contacts">
[[File:Commonly Used Brazing Alloys for Electrical Contacts.jpg|right|thumb|Commonly Used Brazing Alloys for Electrical Contacts]]
</figurefigtable>
For high temperature brazing in vacuum or protective atmosphere vacuum melted silver-copper eutectic brazing alloys are used. These also allow subsequent forming operations due to their higher ductility.