How to adapt interconnects to harsh environments ?

20 Apr 2022

Optimizing Ethernet links

Ethernet cable assemblies are typically insulated with low-temperature thermoplastics (80°C) and terminated with RJ45 connectors. Their quality is sufficient for traditional IT networks including Local Area Networks. To use the Ethernet protocol for challenging applications, including onboard devices for avionics or defense equipment, components must be optimized in terms of several characteristics. Weight savings and reliability are especially important considerations in the design of cables and
connectors used in these environments. Depending on the application, resistance to high temperatures up to 150°C may be requested, which may require the incorporation of insulating materials into the cable.

Better electrical performance
Electromagnetic interference (EMI) protection is another important issue for defense or avionics applications. In this case, plastic connectors do not offer adequate protection against electromagnetic interference. A metal connector with a backshell and 360° shield termination is a very efficient alternative. Electrical performance and signal integrity are key issues for challenging applications. Crosstalk occurs in any system with two or more conductors. Each wire segment acts individually as an inductor and a capacitor. Consequently, a signal transmitted through one circuit or transmission line creates an
undesired effect in another circuit or transmission line. An optimized connector will avoid crosstalk and reflection.

Resistance to high temperatures

Adapting cables or connectors to challenging operating conditions is also a concern for high volume products. For example, flat flexible cables (FFC) used for board-to-board connections are commonly used in many electronic devices. They are typically
insulated with polyester materials that are rated to resist temperatures up to 105°C, but manufacturing processes used to connect FFC to PCBs can require a higher temperature resistance. This is the case with reflow soldering, a process during which flat flexible cables must resist temperatures up to 260°C for a few seconds. In this case, using a polyimide tape instead of polyester is highly recommended.

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