Image credit: E-Z-Hook; Lumberg Automation; Samtec Inc.
Flat cables are used in computers for internal connections to peripherals. They consist of highly stranded, individually-insulated conductors that are laid parallel and then fused in a flat, flexible ribbon form. Flat cables are also referred to as ribbon cables or FFCs (flexible flat cables).
Advantages of Flat Cables
Flat cables distribute the mechanical load over the total width of the cable, improving heat dissipation and eliminating the need for large conductors. Unlike conventional round wire cables, they do not require redundant insulating materials, fillers, and tapes. Because the conductor spacing is fixed and the geometry is constant, electrical characteristics such as impedance, capacitance, time delay, cross talk, and attenuation remain constant.
When selecting flat cables, it is important to consider specifications related to conductors, insulation material, pitch and cable shielding.
A cable conductor consists of a wire or combination of wires that are not insulated from each other, and facilitate the passage of electric current through the cable. Conductor-related specifications include material, size, and number of conductors.
Conductor material includes various conductive metals. Copper is the most widely used material, and features excellent corrosion resistance and high thermal conductivity, but relatively low strength-to-weight ratio. Aluminum is less dense than copper, and is often used as a power conductor.
Conductor size is measured in American Wire Gauge (AWG) in the United States. The higher the gauge number, the smaller the diameter and thinner the wire. Thicker wires have less resistance and are able to carry more current. Outside of the U.S., conductors are measured in mm2.
Number of conductors is usually determined by the cable's application or intended use.
Jacket and Insulation Material
Suppliers manufacture cable using a variety of jacket and insulation material in order to reduce the leakage of current from the conductor. The cable's application is an important consideration when selecting insulation material.
Neoprene is a synthetic rubber well-suited to chemical applications. It is resistant to oil, flames, and chemicals.
Silicon rubber provides superior flexibility but lacks toughness and fluid resistance.
Thermoplastic is an excellent insulating material. Polyethylene (PE), polypropylene, polyvinyl chloride (PVC), Teflon®, and Tefzel® are types of thermoplastic material. While each material has its own unique advantages and disadvantages, most are highly flexible and provide resistance to moisture or chemicals.
Cable pitch is a specification unique to flat cables. The pitch is defined as the distance between the cable's conductors. Cable pitch is almost always uniform, but some flat cables may feature varying distances between conductors. Common pitches include 0.5 mm, 1 mm, 1.25 mm and 2 mm.
Pitch is calculated by dividing the cable's width by the total number of conductors.
Flat cables may feature a type of electromagnetic shielding material, which is wrapped around the cable underneath the outer jacket. Shielding serves to prevent electrical noise from affecting the transmitted signal, and to reduce electromagnetic radiation emission from the cable itself. Shielding is usually comprised of metal braiding, metal tape or foil braiding.
Cutaway image of a shielded cable. Image credit: Tkgd2007
Related Products & Services
Computer cables are used to connect monitors, keyboards, printers, hard drives, and other peripherals to computers.
Electrical Power Wires
Electrical power wires are solid or stranded conductors surrounded by insulation, shielding, and a protective jacket.
Ethernet cables are designed to support Ethernet, a standard protocol for the connection of computers in a local area network (LAN). They use twisted pair cables and modular connectors, and are designed to run at 10 Mbps, 100 Mbps, or 1 Gbps.
Network cables are used in the transmission of data across networks. Choices include Fibre Channel, FireWire or IEEE 1394, GPIB, serial, parallel, patch, SCSI, Ethernet and USB.
Patch Cables and Cords
Patch cables and cords are flexible cables that are terminated at both ends with a plug and used to interconnect circuits on patch panels. They are used with patch panels, groups of ports that connect lines between communications and electronic devices.
SCSI cables are used for high-speed bus connections between small computers and intelligent peripherals such as hard disks, printers, and optical disks.
Video cables are used for the transmission of video signals, including monochrome, composite and component color video signals.