Qualities of copper

Qualities of unalloyed copper:

Oxygen free copper
Oxygen containing copper
Deoxidized copper

Oxygen free copper
Oxygen free copper Cu-OF is cast in protective gas atmophere to prevent oxygen dissolving to copper melt. Oxygen is kept away from melt for example by covering the surface with coal or using a vacuum furnace for melting. Oxygen free copper has the best conductivity of all copper qualities. Its conductivity is at least 100 % I.A.C.S, but in general it varies between 101 - 101,8 % I.A.C.S. The purity of OF copper has to be at least 99,95 %, because its conductivity of electricity and heat are extremely sensitive to impurities.

For electronics industry has been developed even more pure so called certificate quality Cu-OFE (oxygen-free copper, electronic grade), Which has at least 99,99 % purity.

Oxygen containing copper
The most common copper quality is oxygen containing copper, Cu-ETP, tough pitch copper. Oxygen dissolved to melt form lens formed stuctures in solidified copper. Oxygen copper is not as sensitive to impurities as oxygen free copper because oxygen lenses bind effectively impurities. On the other hand its conductivity is lower and it can’t be used in reducing atmosphere.

Deoxidized copper
Deoxidized coppers are generally not used for electrical applications. They are produced by adding small amounts of deoxidizing agents, typically phosphorus to remove oxygen from melt. The amount of phosphorus varies between 0,002…0,050 %. Phosphorus can prevent copper grain growth, thus copper can be annealed freely without fear for too large grain growth. In European standards there are several phosphorus coppers. Most important are phosphorus-deoxidized copper – high residual phosphorus, Cu-DHP, which has phosphorus content 0,015…0,040 % and phosphorus-deoxidized copper – low residual phosphorus, Cu-DLP, phosphorus 0, 005…0,013 %.

Low alloyed coppers
Copper's conductivity is in general decreased if alloying elements are added, but nevertheless sometimes some special properties are achieved by adding small amounts of alloy metals without changing the basic character of the metal. These properties are for example higher strength, improved machinability, or higher softening temperature along with better creep resistance.

Copper alloys
Copper – zinc alloys: brasses
Brass - nickel alloys: nickel silvers
Copper – tin/aluminium alloys: bronzes and red metals
Copper – nickel alloys: copper nickels
Other special alloys