IDC Cable Assembly: Ribbon Cable Connections for Signal and Data Transfer

Electronic device manufacturers usually use IDC cable assembly to connect two or more PCBs installed far apart. But they have other applications.

This assembly consists of two IDC connectors and a ribbon cable type in between. Let’s define it further, including its benefits and the typical connector layouts below.

Table of Contents

• What Is an IDC Cable Assembly?
  • IDC or Crimp: What Is the Difference Between IDC and Crimp?
• How The IDC Connector Works
• IDC Connector Configuration
• Typical IDC Cable Assembly Layouts
• Advantages of IDC Cable Assemblies
• Disadvantages of IDC Connectors and Cable Assemblies
• IDC Cable Assembly Considerations
• Wrap Up

What Is an IDC Cable Assembly?

IDC is an acronym for Insulation Displacement Contact. Also known as an IPC (Insulation Piercing Contact), an IDC connector gives the IDC cable assembly its name.

This connector has a piercing mechanism consisting of sharpened blades that cut through a wire’s insulation to connect to the copper conductor inside. 

The insulation displacement mechanism eliminates the need to strip the wire before linking it to the connector.

Two 10-pin (2×5) 2.54mm pitch IDC connectors

Although it can connect to a single cable, an IDC connector usually has multiple piercing mechanisms aligned in parallel. 

This layout lets you connect a flat ribbon cable, creating a gas-tight cold weld.

The multi-wire connection is suitable for data and signal transmission, and most computer manufacturers use these assemblies to connect hard drives to motherboards.

IDC or Crimp: What Is the Difference Between IDC and Crimp?

Both are solderless, but IDC joins multiple conductors to the connector concurrently. Crimping joins one conductor to the connector plug or socket.

Also, IDC does not require wire stripping because the connector slices through the insulation. But you must strip the cable before crimping.

How The IDC Connector Works

As the name suggests, an insulation displacement or piercing contact pierces and displaces a wire’s outer jacket to get to the conductor inside.

The front side of this cable connector has multiple sockets that connect to mating header pins on the motherboard. These sockets attach to piercing contacts on the rear side where you connect the ribbon cable.

A pin header for connecting an IDC cable connector

The piercing connector contacts are sharp U-shaped blades laid out in two rows. 

These rows have an offset of half the pitch, meaning a 1.28mm pitch connector has the rows offset by 0.64mm.

 Therefore, you can only connect a 0.64mm pitch ribbon cable to such a connector.

To make the cold weld joint, you must push the multi-colored flat ribbon cable into the connector, making the individual cables slide into the U-shaped blade.

These blades displace the insulated cable’s outer jacket from each wire as you push down the cable to touch the copper. 

The blades push firmly together on each side to create a reliable cold weld electrical contact with the conductor.

Manufacturers don’t design these conductors to be reusable, but you can reuse them if you remove the ribbon cable carefully.

IDC Connector Configuration

IDC connectors usually have two rows of pins numbered from pin one.

 They have odd-numbered pins on one row and even-numbered pins on the other. 

Therefore, you only have to know the location of the first pin to understand the connector’s orientation.

Most connectors have a red mark or a raised V next to the first pin to indicate it is the first one, and this mark should correspond with the ribbon cable’s red-colored wire.

A ribbon cable attached to a 2-row IDC connector

Once you identify this first pin, the second pin is on the other row (opposite side). Pin three is next to pin one on the same row.

 This layout places the odd number pins on one side and even number pins on the other.

If the ribbon cable lacks a red coloration, look for markings printed on the insulation or a raised molded ridge. 

These indicators should align with the first pin’s marking.

Typical IDC Cable Assembly Layouts

IDC connectors fall into different categories depending on their pitch (pin spacing in mm) and number of pins. 

All have two rows, making this property a non-differentiating factor. The typical layouts used in computers include the following.

• Two rows of 20 pins each (40 pins) with a 2.54mm connector pitch for 3.5-inch desktop PC hard drive connections
• 2×22 pins (44 pins) with a 2mm pitch for 2.5-inch laptop/notebook hard drives

Outdated IDE cables (ribbon cables with IDC connectors)

• 50 pins (2×25) with a 2.54mm pitch for 8-bit SCSI connections
• 68 pins (2×34) with a 1.27mm pitch for 16-bit SCSI connections
• 26 pins (2×13) with a 2.54mm pitch for parallel DB-25 D-Sub ports
• 34 pins (2×17) with a 2.54mm pitch floppy disk connections
• 2×5 (ten pins) at a 2.54mm pitch for serial DE-9 D-Sub links
• Ten pins (2×5) with a 2.54mm pitch for USB 2.0

All IDCs are female connectors that attach to pin or box PCB headers on the motherboard.

Advantages of IDC Cable Assemblies

• Quick installation: Connecting ribbon cables to IDC connectors reduces the installation or assembly time by up to 50% because there’s no wire stripping, screwing, and twisting.
• Lower assembly costs: The quick population and installation of IDC connectors reduce assembly costs. Time is money.
• Reliable connections: IDC connectors have strain-relief mechanisms that clamp and hold the ribbon cable, creating reliable and durable electrical joints.
• Creates multiple connections: This component lets you connect several conductors in one go. IDC connectors have a bar that helps push the ribbon cable through the U blades. And if the cable has multiple contacts, you can use an IDC crimp tool to install the cable.

A punch-down IDC tool

Disadvantages of IDC Connectors and Cable Assemblies

• Fewer connector options due to design difficulties and sizing issues
• Ribbon cables take more space when routing
• All connector connections must have the same wire size

IDC Cable Assembly Considerations

• Ensure the ribbon cable has the correct sizing (pitch) as the IDC connector for precise cable alignment.
• Each cable’s thickness must fit inside the U channel and match the stranded or solid core specification.
• All connections in the IDC connector must be from the same ribbon cable.

Ribbon cable connectors plugged into a motherboard

• The number of individual conductors in the ribbon cable should match the U-channels in the connector.
• Wires in ribbon cables usually max out at 22 AWG, meaning they are unsuitable for high-current rating applications.
• Although flexible, ribbon cables require more space for cabling.

Wrap Up

As you can see, the multi-channel IDC cable assembly unlocks multiple possibilities in parallel and serial data/signal communication. 

This design makes IDC cables ideal for computing, automotive, consumer electronics, and telecommunications applications.

Should you need this cable assembly for any of these applications, contact us. We’ll reach out with recommendations.