Wire and Cable Conductor Materials
A conductor is at the center of any wire and cable. They are mostly made of metal due to metal's high conductivity. Some metals, however, are more conductive than others. Aluminum, copper, and high-strength alloys are the main materials you'll find at the center of your wire and cable. Each of these has different properties, though, so it's important to know how they could affect your next application.
Aluminum is lightweight, affordable, and can be used in diverse applications. It is less expensive than copper and metal alloys, but it is also less conductive.
Copper can move electricity efficiently and is both inexpensive and versatile. Bare copper is used often, but a copper conductor can also be tinned or silver-coated to improve performance. To learn more, see “types of tinning” below.
Steel may also be used as a conductor. However, it isn't as common as aluminum or copper because it doesn't conduct electricity as well. Copper-clad steel is a popular choice for grounding conductors or in cables requiring exceptional mechanical strength.
Alloys are solutions made with one or more metallic elements. They are generally stronger than the elements used alone. Though high-strength alloys are common conductor materials, they are generally silver-plated or nickel-plated as well.
Types of Coating
Conductors can be coated with other metals to improve performance and other characteristics. See below for information on tinning and other coatings.
Silver is the most conductive metal, but it is very expensive so it is rarely used to construct an entire conductor. Silver plating is much more common. It improves conductivity and widens the wire’s operating temperature range. A silver-plated wire can usually perform from temperatures of -65°C to 200°C. This coating is a common choice for many aerospace applications.
A coating of nickel can be applied to increase corrosion resistance and to expand the operating temperature range of a wire or cable. If the nickel is thick, a wire may be able to withstand temperatures of up to 750°C. Nickel-plating also adds a layer of mechanical toughness for cables that must withstand extreme conditions.
Conductors can be tinned to improve water resistance, increase conductivity, and to allow for easy soldering. Tinned conductors are more expensive than bare metal conductors, but can last up to ten times longer than non-tinned conductors. Generally, tinned conductors are used in electrical and electronic equipment in a wide range of industries. There are different types of tinning designed to meet the various needs of different applications. The types of tinning are:
- Tinned: With basic tinning, individual strands are coated with tin. This is the least expensive method of tinning. It is accepted under UL, CSA, ASTM, and Mil-Spec standards.
- Heavy Tinned: This is similar to basic tinning, but it uses a much thicker coating of tin. It is commonly used in high-frequency induction heaters because it can bond on stripped areas while the rest of the cable remains flexible.
- Prefused or Pre-bond:In prefused or pre-bond tinning, heavy tinned copper strands are twisted and then fused along their entire length. This type of tinned conductor shares the characteristics of a solid conductor but is less likely to break or work-harden in flex applications. Prefused or pre-bond conductors are usually accepted under UL and CSA guidelines, but not by Mil-W-16878 cable specifications.
- Overcoat: This type of tinning involves covering tinned, twisted copper strands with an overall coating of tin. Its advantages are the same as those of prefused or pre-bond tinning. It is accepted by the UL and the CSA, but not the Mil-Spec standards.
- Topcoat: With topcoat tinning, bare copper strands are twisted together and then given an overall coating of tin. Like overcoat tinning, it is accepted by UL and CSA specifications, but not Mil-Spec.
When designing a difficult or abusive application, consider tinning as an option for your cables' conductors. It may improve the overall function of the cable and increase its longevity.