Do I Specify IDC Ribbon Cables or Discrete Cables?

Despite the rise of wireless, cables are still vitally important in modern electronics, and necessary within equipment enclosures. Both ribbon cabling and individual (discrete) wires are common, and both IDC and single crimp connections give reliable connectivity. So how do you choose?

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IDC is an acronym for Insulation Displacement Contact or Connector. That name also describes the way the contact makes connection to the cable conductor.

The rear of the connector, where the cable connection is located, has two rows of twin fork shapes. Each of these shapes has sharp points and a U channel between. The two rows of forks are offset by half a pitch – for instance a 1.27mm pitch connector has the rows offset by 0.635mm, ready for a 0.635mm pitch ribbon cable.

When you push the ribbon cable onto the rows of contacts, the sharp points pierce through the insulating rubber material, pushing it out the way (displacing it). As you push the cable further down, the sides of the center conductor are now in contact with the inside faces of the U channel. The conductor is squeezed slightly, ensuring a good connection joint between the cable and the contact.

This is where the name comes from – the insulation is displaced by the contact beams.

To make sure we’re comparing like-for-like, we’ll quickly define discrete cabling. This is a connection method that involves single cables with a single conductor (stranded or solid). These are often called equipment wires. You would attach them to single contacts, one at a time – whether that’s by crimping or soldering. Solder cup contacts may be pre-assembled into the connector, but crimp contacts will also need assembling to the housing.

It’s a really big advantage in terms of assembly processes – with IDC and ribbon cables, you’ll connect all your conductors in one action.

An IDC connector has a bar that goes over the back of the connections. This bar helps push the ribbon down into the right position. It also makes sure that in use, the cable stays on the contacts, and that the sharp beam ends are covered up.

If you’ve only got a few contacts in your connector, it might be possible to do this assembly just by hand. But the more contacts you have the more force you’ll need, so tooling is available to help. This tool works like a vice or clamp and helps push the contact, cable, and bar together.

Clearly, this process is much quicker than discrete single cables, where every single contact must be (a) stripped, (b) crimped or soldered, (c) inspected and (d) assembled into the housing (depending on contact type).

This is a big saving in time, which means saving in costs. So why are aren’t all cable assemblies using IDC and ribbon cables?

Finally, it’s not generally a good design choice for high reliability connectors that need to withstand the extremes of vibration, shock and temperature.

The performance of the contact design for IDC contacts often doesn’t match the more rugged and capable contact design we use on connectors like Datamate and Gecko.

So how do you choose? Consider that your options will often be dictated by the connector performance you need. Make sure you first know what specifications you need from the connector, as that may eliminate one or other connector type.

If you still have a cabling choice, consider if it’s a one off, whether you have cable routing restrictions, and whether there are ready-made cables available. If you’re making cable assemblies in house, do you have the tooling or training for a particular type already?

Harwin’s Experts are ready to help guide you through the variety of cable connection styles and can eliminate the problems of in-house limitations with ready-made cable assemblies – contact us today.

If you would like to talk to someone about which product would be the right fit for your requirements, contact one of our Experts for assistance.

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