CONDUCTORS

Conductors

The central component of any cable, the conductor is the term for the metallic wire or wires that carry the signal and/or power through the cable.

Metals

There is a wide range of metals that can be used as a conductor, however Copper (Cu) is by far the most common due to its relative low cost and availability. Other common options such as aluminium, steel or tinsel wire (mixed strands of copper and cotton) may offer advantages in strength, weight or flex-life, however they almost always come at the cost of reduced conductivity. Plated copper such as Tin Plated Copper (TPC), Silver Plated Copper (SPC) and Nickel Plated Copper (NPC) offer additional features such as elevated temperatures and improved conductivity or solderability. Purer conductors such as Oxygen Free High Conductivity (OFHC) plated copper can improve the signal performance, and are often used for audio frequencies, whilst High Strengh Copper Alloy (HSA) conductors can provide a much improved dynamic performance over standard copper conductors.
A variety of other metals and alloys are often used for their unique conducting properties when exposed to heat. Commonly known as Resistance Wires, they are used in Thermocouple cables where combinations of resistance wires can be used to detect variations in temperature. Some of the most commonly used are Nickel-Chromium (NiCr), Copper-Nickel (CuNi) and Iron (Fe).

Strandings

The simplest form of conductor is a single, solid strand, however although this offers the smallest diameter, the purest signal and the largest cross-sectional area, this is also the weakest option and solid conductors are prone to breaking after just a few bending cycles. To improve the durability and flexibility of a conductor it is common to strand multiple wires together, the more wires that are stranded together to make a given size, the more flexible the conductor will be. Metric sizes categorise the number of strands into Classes, the higher the class, the more strands in the conductor:
- Class 1 Solid, round.
- Class 2 Stranded conductor, 7 strands (larger sizes will be 19 strands).
- Class 5 Multi-stranded conductor for flexible ‘general purpose’ installations.
- Class 6 Extra-multi-stranded conductor for improved flexibility / flex-life.

Sizes

There are many different national and international standards for identifying the size of a conductor, and terminology such as BWG, SWG and Cmils can still be found. However most parties now standardise on either American Wire Gauge (AWG) or Metric (mm2) which is also referred to as Cross Sectional Area (CSA). It is also quite common to use both of these methods as they indicate subtly different sizes (see Habia’s AWG / Metric conversion table for details).
One important note regarding AWG sizes is that the higher the number, the smaller the wire. For example: AWG 2 is a large conductor with a diameter of 8,64mm. AWG 20 by contrast is a small conductor with a diameter of just 0,96mm.

Other factors

The intended use of the cable is the key reason for selecting one type of conductor over another. Whilst the applications are as varied as the custom design cables made to meet them, some examples might include:
- Crimp terminations Use as few strands as possible and avoid rope-lay or bunched conductors.
- Soldered terminations Use tin or silver plated copper for best results and avoid nickel plated copper.
- Data/signal use Use solid, smooth-surfaced conductors and SPC or steel for best results.
- Dynamic use Use as many strands as possible and high strength copper alloy for best results.
- High temperature use Use silver plated (+200oC) or nickel plated (+260oC) for best results.