What Is Ribbon Cable?
A ribbon cable is a flat multicore cable with conductors running parallel, side by side. It's commonly used in electronic equipment and computers where you need multiple connections. Conductor spacing varies, but the most common standard is for the conductors to be exactly 0.05 inches apart. Ribbon cables, also known as planar cables, generally use an IDC connector at either end, although other options are possible. The number of conductors in each ribbon follows the same pattern as the number of ways of corresponding IDC connectors.The Cicoil Corporation invented ribbon cables in 1956 for use in computers, where their compact dimensions simplified computer design.
Types of Ribbon Cable
Allied Wire and Cable sells coaxial ribbon cables in different widths from 6-way up to 80-way, and in three configurations: gray, rainbow and shielded.
Gray Ribbon Cable
As the name suggests, this type of cable has a uniform color, which in most instances is gray. There's usually some type of edge marking to signify the first conductor that’s terminated in pin 1 of an IDC connector. This form of cable complies with UL style 2651 and is suitable for use at voltages up to 300 volts.
Rainbow Ribbon Cable
Rainbow ribbon cables have colored conductors, so it's easy to identify individual cores. Manufacturers use 10 standard colors, which repeat for ribbon cables with more than 10 conductors. The standard colors are brown, red, orange, yellow, green, blue, violet, gray, white and black. Rainbow ribbon cable complies with UL 20932 and is suitable for use up to 300 volts.
Shielded Ribbon Cable
Electromechanical interference (EMI) is one of the disadvantages of running multiple conductors in parallel and, consequently, the FCC banned the use of standard ribbon cables unless users shielded the EMI by using a metallic enclosure. Shielded ribbon cable overcomes this limitation by having a shield manufactured from aluminum tape or wire braid. The shielded ribbon cable conforms to the UL 2912 standard, and its maximum voltage rating is 150 volts.
Ribbon Cable Construction
The conductor is pure stranded copper wire, although standards permit a solid conductor. The number of strands is generally seven.
AWC ribbon cables use extruded or heat laminated polyvinyl chloride (PVC) insulation. Insulation thickness varies from 0.035 to 0.036 inches.
The shielded ribbon cable has a continuous aluminum tape shield connected to ground by a special connector. Some types use a copper braided shield. Working With Ribbon Cables
Terminating ribbon cables with an IDC connector is easy as the connector has small blades that cut through the insulation forming a semi-permanent connection. Ribbon cables have a fairly rigid structure that only permits bending perpendicular to the plane of the wire. You can't bend the cable in the horizontal plane except by folding the cable or, if it is long enough, by gently twisting the cable. To prevent damage when folding, the fold radius should be always greater than 3 wire diameters.
General Ribbon Cable Specifications
|Conductors:||Stranded copper wire|
|Wire Size:||28 AWG, although standards allow sizes from 14AWG - 36AWG|
|Voltage:||150 volts and 300 volts, depending on type|
|Characteristic Impedance of Shielded Cable:||70 ohms|
|Characteristic Impedamce of Other Cables:||135 ohms - 145 ohms|
Ribbon Cable Approvals
AWC ribbon cables conform to the following standards:
- CSA: AWM I A/B
- Gray Ribbon Cable: UL 2651
- Rainbow Ribbon Cable: UL 20932
- Shielded Ribbon Cable: UL 2912