Micro-Coaxial/Twinax Connectors

I-PEX micro-coaxial connectors are ideal for connecting displays, camera modules, storage devices and other applications.

What is Coaxial Cable?

Play Micro-Coaxial Cable Assembly Capabilities video

1) Basic Structure of Cables

Cables that have a simple structure with a conductor covered with a jacket are called Discrete Cables. Whereas cables with a multi-layered structure with a center conductor covered with an insulator layer along with an outer conductor and jacket are called Coaxial Cables. The coaxial cable outer conductor plays the role of electromagnetic shield so the electrical signal transmitted through the center conductor is less susceptible to electromagnetic waves (electromagnetic noise) from the outside.

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2) What is Micro-Coaxial Cable?

The size of the center conductor used in the coaxial cable is described using an AWG (American Wire Gauge) Standard and the larger the AWG number, the smaller the size of the center conductor.
In general, coaxial cables with an outer cable diameter (O.D.) of ~1 mm or less are referred to as "micro-coaxial" cables. Micro-coaxial cable is widely used for signal transmission between module boards inside devices such as PCs, tablets and smartphones, as well as precision instruments used for medical, industrial, automotive, aviation, etc.

Note: Reference only (Cable size varies depending on the types of cable.)

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What is Micro-Coaxial Connector?

1) Micro-Coaxial Connectors (Micro-Coaxial Cable Connectors)

Micro-coaxial connectors are mainly used to connect digital signals between module boards by the differential transmission method using micro-coaxial cables. To perform appropriate signal transmission, the center conductor which transmits the signal, needs to be connected to the signal circuit on the board via the contacts of the connector. The outer conductor of the cable needs to be electrically connected on the board via metal parts of the connector referred to as the shell. The electrical connection of the outer conductor to board through the connector shell is called "grounding".

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2) Process of Plug Harness Preparation Using Micro-Coaxial Cables

Main Process of Plug Harness Preparation:

Prepare Cable Sub-Assembly
Set the Cable Sub-Assembly to the Plug Housing Assembly part and solder the exposed conductor to the plug signal terminal
Set Lock Bar Assembly (or Lock Bar) to Plug Housing Assembly parts
Cover the plug shell and solder the required area to complete the plug harness

First, pre-process the micro-coaxial cables for easy plug harness assembly. A pre-processed cable is called a "cable sub-assembly". This pre-processing simplifies the cable termination process to the connector and improves the stability of plug harness quality. This is done before terminating the cables to the connector.

Image of cable sub-assembly preparation process

The cable outer conductors are electrically connected to the board via connector by terminating the cable outer conductors to the connector shell to obtain good ground characteristics.

Image of plug harness assembly process
(Example: CABLINE®-CA II)

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3) Types of Cable Sub-Assembly

Generally, the following cable types are available for cable sub-assemblies (dependent on harness makers):

All micro-coaxial cable:
Only micro-coaxial cables are used. Cable sub-assemblies can be made with different cable diameters (diameter size range may be limited).

Micro-coaxial/discrete cable mixed:
Both micro-coaxial cables for signal transfer and discrete cables for power supply are used.

Ground bar with ground fingers:
The fingers formed on the ground bar are directly attached and soldered to the plug contacts, resulting in a reduction in the number of cables used and an expected improvement in the electrical characteristics performance of the harness.

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Why is Micro-Coaxial Cable Preferred for High-Speed Applications?

1) Features and Applications of Micro-Coaxial Cable

As high-speed Internet improves and the usage of large-capacity memory devices increases, high-quality images and videos can be enjoyed more easily on consumer products such as PCs, tablets and smartphones. The amount of information that needs to be processed on the device has dramatically increased and the signal speed (transmission standard) in the device has been getting faster and faster.

Cables and FPC/FFC are mainly used for jumper connections when transferring signals and power between module boards in devices. To some extent, the types of cables and FPC/FFC that can support are determined by the Signal speed (Signal transmission standard) and Transmission distance. In general, coaxial cables* are considered suitable for high-speed or long-distance signal transmission.

* Coaxial cable referenced above includes micro-coaxial cable and Twinax cable.

With the recent increase in signal transmission speed the usage of micro-coaxial cables for jumper connections in devices is expanding.

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2) Signal Transmission Advantages of Micro-Coaxial Cable

Signal transmission characteristics are affected by a variety of parameters such as characteristic impedance, insertion loss, return loss and crosstalk. Below are some of the main reasons why micro-coaxial cables are generally considered to have signal transmission advantages when a high-speed signal is transmitted.

Return Loss Reduction:
The center conductor, dielectric and outer conductor in micro-coaxial cables are suitable for matching and are stabilized at specific impedance.
Matched and stabilized impedance creates a low return loss.
Insertion Loss Reduction:
A micro-coaxial cable can secure a larger cross-sectional area of the center conductor compared to FPC/FFC when matching to specific impedance, which minimizes the reduction of insertion loss.
High Shielding Performance:
The outer conductor works as an electromagnetic shield so the electrical signal transmitted on the center conductor is less susceptible to electromagnetic waves (electromagnetic noise) from the outside. In addition, the shielding effect of the outer conductor also helps to reduce crosstalk between signal lines.

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3) Mechanical Advantages of Micro-Coaxial Cable

Oftentimes micro-coaxial cable is used because it has a higher degree of flexibility compared to shielded FPC / FFC and it can stabilize the electrical characteristics even if it is bent.

Flexible micro-coaxial cables are suitable for devices with hinges that require the cables to be moved and routed within the device, such as hinge on notebook PCs and rotating cameras on drones. With the number of applications that include high resolution cameras and panels on the rise, along with higher signal transfer speeds, micro-coaxial cables that combine high-speed signal characteristics and mechanical advantages are a preferred solution.

foldable phone

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Why are I-PEX Micro-Coaxial Connectors Widely Used?

1) Features of I-PEX Micro-Coaxial Connectors

I-PEX is a pioneer in the micro-coaxial connector industry with a wide array of products available for use in many different applications. I-PEX micro-coaxial connectors have the #1 market share in the notebook PC panel connector industry.
(CABLINE^®-VS Receptacle: VESA standard connector)
Article: History of Micro-Coaxial Connector

I-PEX connectors F20

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2) Features of I-PEX Shielded Connectors

As electronic devices are evolving to be more high-performance, power-saving, and compact, the high speed signal requirement in these devices increases, the number of electronic components operating at low voltage increases and the density of mounted electronic components becomes higher. If electromagnetic noise is added from the outside, unnecessary current may be induced to the circuits in the devices causing a malfunction or damage to high-performance electronic components which may also lead to electronic device breakage. In addition, in electronic devices with wireless communication functions (for example, notebook PCs, tablets and mobile phones) electromagnetic waves generated within the devices can add to the wireless communication circuit noise which could reduce antenna reception performance.
In such cases, in general, the measures against electromagnetic noise inside the device are implemented by incorporating electromagnetic noise filter components into the circuit and/or physically blocking the electromagnetic noise by adding a metal shield that covers the components.

With the introduction of smaller devices with a high density of mounted components, along with the high speed signal in these devices, it is imperative to take measures against electromagnetic noise at the jumper connections in devices. I-PEX has developed a high-performance EMC connector series (ZenShield^®) that solves electromagnetic noise in the connector by using an appropriate grounding structure and cover which includes the mounting position of the signal contact tails with metal shields. This solution is widely adopted by many customers to prevent electromagnetic interference, especially in high-performance devices equipped with wireless communication functions such as Wi-Fi, GPS, and LTE.