If you have ever peeked inside the workings of your computer, you have likely seen a ribbon cable (or two) connecting your hard drive and other storage drives to the motherboard. The ribbon cable has been a staple in the data communications industry for decades, but like all enduring computer components, the ribbon cable has had to evolve to avoid becoming obsolete in the digital era.
As you might guess, ribbon cable got its name from its design— a wide, flat molded construction featuring many conducting wires running parallel to each other. Because the conductors lie in the same plane, the product is also sometimes called multi-wire planar cable, or simply flat cable.
A Brief History
Invented in 1956 by the Cicoil Corporation, the ribbon cable’s flat design was engineered to replace large, awkward, and inflexible round cables in computer systems. They were first put to work in mainframe computer devices like card readers and punching machines.
By the 1960s, NASA was using ribbon cable in milestone aerospace applications, like the first lunar landing. Ribbon cable’s speedy rise to popularity can be attributed, in large part, to its convenience. Because the cable lies flat, it takes up little room and can even be run under carpeting.
The design also lends itself to easy mass termination with Insulation Displacement Connectors (IDC). Growing competition between flat cable manufacturers created a push for standardization that would achieve higher quality, easier installation, and lower costs across the board.
Ribbon cables are called out by the number of conductors, often termed “ways,” and the spacing between them, known as “pitch.” While they can still be made in all sizes and variations, the most common pitch is 0.050 inches.
Common conductor counts range from 4 to 80 conductors. A standard flat cable, like a gray PVC ribbon cable, is often marked with a red polarity stripe along one edge that indicates which conductor should be matched to Pin 1 on the connector. This prevents component damage by discouraging reverse connections.
Some applications benefit from a “rainbow” ribbon cable, which identifies each conductor with a different color. For some time, ribbon cable was used for both internal and external computer connections in computers like the Apple II.
However, some of the same characteristics that make flat cable ideal for tight spaces inside computers make it less suited to connecting outside devices. The wide flat shape that makes ribbon cable so convenient in some places can also impede computer cooling by blocking airflow. In addition to that, the construction offers no sideways flex and can make a cable bunch unmanageably awkward.
In the 1980s, the FCC discovered an unintended quality to ribbon cable. It made an excellent antenna and broadcasted signals that interfered with analog TV reception. A variety of workarounds were developed, but the stand-out solution was the round-to-flat ribbon cable.
In a round-to-flat cable, a ribbon cable is twisted into a round shape before being taped but left flat at the ends so that it can still be terminated with IDC connectors. It offers the best of both worlds. While flat ribbon cable has remained popular for internal computer wiring, round cables have replaced flat data cables in external connections.
Identifying Ribbon Cables
As it so often happens in the wire and cable industry, the differing cable constructions and standards converged, becoming compatible but leaving behind a variety of names to confuse wire buyers.
In addition to “flat cable” and “multi-wire planar cable”, ribbon cable can also be called out as ATA cable, because it falls under the ATA (Advanced Technology Attachment) interface standard. You may also see it called PATA (Parallel ATA) cable, a name developed to differentiate from the more recent and smaller SATA (Serial ATA) cable. The ATA interface evolved out of the IDE (Integrated Drive Electronics) interface, so it is not uncommon to see ribbon cable referred to as IDE cable.
Ribbon Cable Today
Today, ribbon cable comes in all different shapes, sizes, and colors, and can be referred to by many names. It can be used in a huge range of applications, from high-speed computer connections with a coaxial ribbon cable to rainbow ribbon cable in Ghostbusters’ proton packs!
Have more questions? Check out our Ribbon Cable FAQ page.