Understanding Ribbon & Flat Cable
Flat Cable: a broad term used to describe any cable that has a flat, planar design. This includes various configurations of conductors, such as twisted pairs or individually insulated wires arranged side by side.
Ribbon Cable: under the category of flat cable because of its distinct flat shape where multiple conductors are laid out side by side in a parallel and organized manner, like a ribbon. Its flat structure allows it to fit in spaces where height is a limitation, making it particularly suitable for use in internal electronic systems.
All ribbon cables are flat cables because of their flat configuration. However, not all flat cables are ribbon cables. Flat cables can be of many other types with different internal wire arrangements and intended uses.
| Feature | Ribbon Cable | Flat Cable |
| Structure | Parallel conductors with a uniform pitch | Flat arrangement, can include twisted pairs |
| Typical Applications | Internal connections, PCs, peripherals | Industrial, automotive, robotics |
| Connectors | IDC connectors | Various connectors (depending on design) |
| Flexibility | Limited flexibility | Highly flexible and durable |
| Shielding | Generally unshielded | Can be shielded for noise reduction |
The Cradle of Ribbon Cable
The original ribbon cable was a two-conductor 300-ohm twin lead used in radio and television. Modern ribbon cables, however, typically contain many more conductors.
Invented in 1956 by Cicoil Corporation, ribbon cables were made using silicone rubber to mold a flat design with multiple conductors, resembling a ribbon or duct tape. This innovation allowed companies like IBM to replace bulky round cables with flexible ribbon cables.
Initially used in mainframe computers and devices like card readers and tape machines, ribbon cables gained popularity due to their low profile, cost-effectiveness, and ease of termination with insulation-displacement connectors (IDC). They became widely used in computers, printers, and various electronic devices.
Conductor and Wire Gauge
Conductor Count: The number of wires (conductors) in a ribbon or flat cable can vary significantly. Commonly, ribbon cables may have 9, 15, 25, or more conductors.
Wire Gauge (AWG): These cables often range between 28 to 20 AWG. The wire gauge affects both flexibility and current-carrying capacity. Thinner wires (higher AWG) are typically used in data signals, while thicker wires (lower AWG) can handle more power.
Size of Ribbon Cable
Ribbon cables are defined by two main measurements: the spacing (or pitch) of the conductors and the number of conductors. The most common pitch is 0.05 inches (1.27 mm), which supports a two-row connector with a pin spacing of 0.1 inches (2.54 mm). These cables are widely used for internal connections in various equipment, particularly in personal computers for floppy disk drives and older Parallel ATA cables.
The number of conductors typically follows standard values, including 4, 6, 10, 20, 40, and 80. Larger cables can be stripped to the desired width, such as a 26-way IDC cable being modified to 25 ways. Conductors are usually stranded copper wire, sized at 0.32, 0.20, or 0.13 mm² (22, 24, or 26 AWG).
Finer and coarser pitch options are also available. For example, high-speed ATA cables use a 0.025-inch (0.64 mm) pitch, while portable devices may use pitches as small as 0.3 mm, often utilizing flexible flat cables (FFC) instead of traditional ribbon cables.
Popular Types of Connectors for Ribbon Cables
| Connector Type | Description | Common Uses |
| BT224 Connector | Known as IDC connectors; mate with plugs or 0.1 inch (2.54 mm) header pins. | ATA cables |
| D-Subminiature Connector | Used for serial and printer ports; IDC versions are less common. | Serial and printer ports |
| Micro Ribbon Connector | Used for 36-pin printer ports (IEEE 1284) and 50-pin SCSI ports. | Printer and SCSI connections |
| DIN 41612 Connector | Designed for Eurocard buses. | Eurocard applications |
| PCB Transition Headers | Two rows of pins matching BT244 spacings for direct PCB soldering. | Direct soldering to PCBs |
| DIL Headers | Pins have standard DIL IC spacing; allowing external device connections. | In-circuit emulators, PCB transition headers |
Benefits of Ribbon Cables
Ribbon cables are advantageous due to their flat construction, which allows for space-efficient installation, particularly in computers and tight environments. They can be discreetly laid under carpeting but must be used in straight runs as they cannot bend sideways. Measured by pitch (commonly 0.050 inches or 1.27 mm) and ways (typically between 4 and 80 conductors), ribbon cables are small, lightweight, and flexible, making them easy to separate and route within circuit boards. Additionally, standard off-the-shelf configurations simplify their use in various applications.
The Insights are based on online research; please let us know if you find any inaccuracies.
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