EoW September 2010

technical article Sustainability in the development and production of alloys

By Ralf Hojda, Dr Michael Köhler, James Schraml

1 Introduction The increasing scarcity of resources is steadily impacting on economic success in the private and industrial spheres. Energy supply and raw materials are equally affected. Manufacturers of copper-alloy semi- finished products have experienced price rises in the three-figure percentage range, so that in recent years the ratio of the value added to the metal value, which was in balance just a few years ago, is now one to three. Although mechanical and technological factors were once the primary criteria for selecting a suitable alloy, the significance of the value of the metal has increased. This also has consequences for the development and manufacture of alloys. concerned about the recyclability of new alloys and composites as about using stronger alloys to reduce wall thicknesses, and thus conserve resources by using less material. This article uses two developments to illustrate good recyclability and reduced use of materials. In the first case the described material is a new high-conductivity alloy that can be recycled without any limitations, even when tin coated. The second concerns a high-strength bronze, which can readily be fed back into the material cycle and, above all, is potentially suitable for use in numerous miniaturisation applications, thus facili- tating the conservation of resources. Developers are equally

Although components such as nickel and chromium improve a copper alloy’s corrosion resistance, they simultaneously bring about a considerable reduction in its conductivity (see Figure 1). Composites are a frequently adopted solution to this problem, primarily in the form of coatings based on pure tin applied to the surface of copper alloy. With just a few exceptions the RoHS

Mechanical strength, electrical con- ductivity and corrosion resistance are key criteria for the reliable functioning of components during the total lifetime of the whole system. In many cases the required properties are mutually incompatible, as when a combination of good conductivity and excellent resistance to corrosion is specified.

Figure 1 ▼ ▼ : Influence of alloying elements on the electrical conductivity of copper

Electric conductivity in m/Ω mm 2

2 Examples 2.1 Development 1

Electric conductivity in % IACS (International Annealed Copper Standard)

Connecting elements used in the electrical engineering and electronics sectors have to satisfy numerous requirements.

Additions in mass %

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EuroWire – September 2010