Air coils are actually inductors that do not contain a core, but instead use the surrounding air. Being classified as an air coil or an inductor means they are considered a passive electronic component.
Air coils are sometimes referred to as “self supporting” coils because there is no core to hold their shape. They are wound on a fixture or mandrel. Usually a special bondable wire must be used with either an electric current being passed through the wire to heat and cure the coating, or a solvent is used to activate it. These methods enable the wire to adhere to itself and thus hold its shape. In order for this to work, the heat or applied solvent must be applied while the winding is still on the metal mandrel. They are then removed once the wire “cures”.
Some air coils are wound by hand, but most are done on an automatic winding machine. This minimizes the about of direct labor and thus the component’s cost. This is one of the major benefits to using an air coil.
There are several other benefits to using an air coil in a design, if the electrical parameters allow for it. One of these benefits, as mentioned above, is the price. Not just because of the reduced labor, however, but a minimum amount of raw material as well helps to keep this product at a lower price than many of its counterparts.
A second advantage is that the inductance’s are unaffected by the current that is being carried. This benefit is due to the lack of an actual core.
A third benefit is the lack of iron or core losses. This, as one might imagine, is also due to the fact that there is not an actual core present to create these losses in the winding.
Finally, the fourth benefit is that they can operate at higher frequencies than those with a physical core. This ties back to the core losses, as they go higher in frequency the losses become greater. As electronics go higher and higher in the frequency spectrum, this becomes a tremendous advantage for using air coils in future circuit board designs.