Copper-clad aluminum wire

Copper-clad aluminum wire, commonly abbreviated as CCAW, is a conductor composed of an inner aluminum core and outer copper cladding.

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Uses

The primary application of this conductor is for high-quality coils where weight is an issue, such as the voice coils in headphones, portable loudspeakers or mobile coils in other applications.

CCA was also used in mains cable for domestic and commercial premises. The copper/aluminium construction was adopted to avoid some of the problems with aluminium wire, yet retain some of the cost advantage. It is not used today in domestic 240v installation wiring.

Properties

The properties of copper-clad aluminum wire include:

• Lighter than pure copper
• Higher conductivity than pure aluminum
• Higher strength than aluminum
• Better solderability than aluminum, due to the lack of the oxide layer which prevents solder adhesion when soldering bare aluminum.
• More expensive than a pure aluminum wire; cost relative to pure copper may be hard to establish due to the volatility of copper prices.

Skin Effect

Although the skin effect causes alternating current to concentrate on the more-conductive copper cladding of the conductor, causing the resistance of the wire to approach that of a pure copper wire at sufficiently high frequency, the skin effect is too weak at audio frequencies to be of importance in typical applications of copper-clad aluminum wire, the skin depth generally being greater than the radius of the wire (about 0.6 mm at 20 kHz in both Cu and Al). The primary benefits of cladding aluminum with copper rather than vice versa are solderability, as described above, and manufacturability, copper being a metal that can be electroplated with ease, unlike aluminum.

The skin effect is of greater importance in copper clad steel, due to its use in high frequency applications such as coaxial cable, the lower skin depth in steel, and the greater difference in conductivity between the core and the cladding.