Changes

Various requirements based on the enduse of the contact components have to be met by carrier materials. Copper materials have to exhibit high electrical and thermal 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. Besides these, the materials must, depending on the manufacturing processes employed, also have good technological properties like ductility, to allow warm and cold forming, suitability for cutting and stamping, and be capable to be welded, brazed or coated by electroplating.

materials 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 material number. For reference, we also show in (<xr id="tab:MaterialDesignations"/> ) the material designation according to UNS, the Unified Numbering System (USA). Other internationally used standard and material numbers include, among others, those issued by CDA (Copper Development Association, USA), and GB (Guo Biao – China).

The most important EN as well as the US based and widely used ASTM standards , covering the use of flat rolled copper and copper alloys in electrical contacts , are:

Copper is used in electrical engineering , mostly because of its high electrical conductivity<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 MPa = 1 N/mm²</ref> which with 58 MS/m (or m/Ωmm²) is only slightly below that of silver. Other advantages of copper are its high thermal conductivity, corrosion resistance, and its good ductility. The work hardening properties of ETP copper is illustrated in (<xr id="fig:Strain 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 are strongly 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-->).