Ruggedization at the Application-Ready Platform Level

Justin Moll, Director of Marketing
VadaTech, Inc.

An important part of electronics protection is ruggedization for extreme environments. Take avionics applications, where the system needs to handle several challenging elements. These include, to name a few:

  • High altitudes
  • Shock and vibration
  • EMC considerations
  • Environmental (humidity, salty air/salt fog, condensation, etc)
  • Airflow and power restrictions
  • Mission-critical demands

Figure 1.

On the chassis side, the ATR (Air Transport Rack) is a proven, reliable form factor, helping to ensure interoperability. With a thick aluminum (or other material) frame, the unit helps provide inherent shock and vibration protection. But, ATRs are not just used in commercial or military avionics; they are increasingly used in ground-based mobile transports, such as Humvees, tanks, etc, and some subsea systems. Although typically used in Defense apps, these enclosures are by no means limited to that arena. They are incorporated into commercial applications that require extreme mobile processing, mobile broadcast, and other rugged demands. Weather monitoring systems, energy exploration, or systems where the racks are mounted in a vehicle or mobile trailer such as border control and remote mobile broadcasting are a few examples.

Figure 2.

At the board level, the modules can de designed to handle extreme environments. In the MicroTCA.2 and MicroTCA.3 specifications, ruggedization is specifically addressed for the modules. In some applications, having a fan to cool the chassis is not desirable or practical.  Thus, conduction-cooled boards (and enclosures) can be utilized. The machined clamshell design slides efficiently into wedge locks, which transfer the heat to the outside of the chassis fins (maximizing surface area for heat dissipation). On the board, the conduction-cooled design has the dual benefit of acting as a heatsink, and transferring heat away, while the clamshell design provides mechanical and shock/vibration protection. See Figure 1 of conduction-cooled boards.  The boards shown are the power supply and the management/switch hub card (MicroTCA Carrier Hub or MCH) for the MicroTCA architecture. Figure 2 shows the lightweight aluminum conduction-cooled ATR that these boards are plugged into. The enclosure design of the boards/chassis ensures EMC protection. To handle issues such as humidity and condensation, the backplane and modules can be conformal coated.

Figure 3.

The MicroTCA.3 specification (Hardened Conduction-Cooled MicroTCA) has this wedge-lock configuration, where the board connector is stabilized by the clamshell, reducing the effects of shock and vibration. In MicroTCA.2 (Hardened Hybrid Air/Conduction-Cooled MicroTCA), they utilized an open clamshell (that accepts airflow), but provides the same stabilizing effect. The MicroTCA committee did extensive testing to compare to other open architectures (such as OpenVPX) and ensure that the architecture was on par or exceeded the other specifications. See Figure 3 for a table from PICMG’s MicroTCA Application Guide showing the degrees of shock/vibration testing for the types of MicroTCA chassis.

By instituting system-level protections on the modules and the chassis, this open-standard MicroTCA ATR example can provide tremendous reliability and performance for the embedded computing requirement. The ATR shown, with dimensions of 238.76 mm by 123.95 mm by 320.5 mm deep offers mission-critical, managed computing using x8 PCIe Gen 3. By doubling up on the PCIe signals, you can have 20G lanes of PCIe across the modules. With significant bandwidth, system management, versatility of options, and reliability in an open architecture, MicroTCA is a cost-effective and powerful option for rugged computing demands.

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