Copper (Cu) has been known for more than 10,000 years, with its discovery dating back as far as the Neolithic period. In addition to gold and silver, it was one of the first materials people worked with and processed. There are a lot of regions where it became so widespread and widely used between 5000BC and 3000BC that this period has been labeled “Copper Age” there (people used it to make tools, weapons, jewellery, goods, works of art and a lot more). Triggered by the discovery and growing use of electricity, it gained additional importance in the 19th century due to its being the second best metallic conductor after silver, which it outprices because it can be found in much higher quantities.
Today, two different types of copper are used for electrical conductors:
Oxygen-free copper (CU-OF1) for special applications
Copper containing oxygen (CU-ETP1)
Basic properties of copper
| Material | Copper | Oxygen free Copper | |
|---|---|---|---|
| Symbol | Cu-ETP1 (E-Cu) | Cu-OF1 (OF-Cu) | |
| Material number | CW003A | CW007A | |
| Standard | EN 1977 | EN 1977 | |
| Composition | %-by-weight | Cu ≥ 99.90**Oxygen max. 0.040 | Cu 99.95 |
| Density | g/cm³ at 20°C | 8.9 | 8.9 |
| Melting point | °C | 1083 | 1083 |
| % IACS min.* | 101 | 101 | |
| Electrical conductivity | m/Ωmm² at 20°C | ≥ 58.58 (in annealed condition)** | ≥ 58.58 (in annealed condition)** |
| Thermal conductivity | W/(m*K) | 400 | 400 |
| Manufacturing methods | Contirod or Southwire (casting wheel) The molten copper is poured on a casting wheel (Southwire) or a conveyor belt (Contirod) thus taking on the form of an endless strand. While still maintaining its melting heat, it is fed through a multi-stage hot-rolling mill where it is reshaped into continuous cast wire rod, which is the starting product for the production of cables, strands and ultra-fine wires. There is, however, one drawback to using CU-ETP: while the hot copper is being poured on the casting wheel or the conveyor belt, it is exposed to the ambient air. As a consequence, the copper absorbs small quantities of oxygen from it. This poses no problem for a great deal of applications, but in particular areas even this minuscule amount of oxygen absorbed provokes the contraction of the so-called “hydrogen disease”.®® | Dipforming and UpcastingDipforming: a so-called „mother rod“ with a purified and scraped surface is run through molten copper. The latter settles down on the mother rod, prompting the diameter of the wire to increase significantly. Using a hot-rolling mill it will be calibrated to its final diameter afterwards. Upcasting: having reached its final sub-assembly diameter, the wire is hoisted through a cooled ingot mold and wound up without further treatment. | |
| Notes on properties and use | Precious metalChemical element, pure (as opposed to alloys like bronze, brass or steel)Very high thermal conductivity (400 W/(m*K))The good thermal conductivity is in line with the good electrical conductivityStrength in recrystallized condition < 200 N/mm²High ductilityResistant to corrosion from most environmental impacts Exceptions: oxidizing acids, hydrous ammonia and halogenated gases, hydrogen sulfide, seawaterGood solderabilityAnti-bacterial agentElongation > 15 % (dependent on diameter) | ||
| containing less impurities and trace elements which evaporate in a vacuumsuitable for semi-finished products that require resistance to hydrogen as in ISO 2626***ultrasonic welding and hard soldering (brazing)for use in fields of vacuum technology and electronics | |||
