What is Rugged MicroTCA?

MicroTCA was defined for the telecommunications market and as such for the ambient conditions that prevail there. Rugged MicroTCA (divided into 3 secondary MicroTCA specifications) describes the ambient conditions in other market sectors, such as industry or military.

What is MicroTCA.1?

MicroTCA.1 (Air Cooled Rugged MicroTCA) is a secondary specification of MicroTCA; it describes rugged air-cooled systems for industrial applications.

What is MicroTCA.2?

MicroTCA.2 (Hardened Air Cooled MicroTCA) a secondary specification of MicroTCA; it describes rugged air-cooled systems for military applications.

What is MicroTCA.3?

MicroTCA.3 (Hardened Conduction Cooled MicroTCA) is a secondary specification of MicroTCA; it describes rugged conduction-cooled systems for military applications.

What is Conduction Cooled?

If forced air cooling cannot be used in a system, the heat generated has to be dissipated via an alternative route. Heat is transported to the enclosure via a frame (CCA), which is clamped firmly to the Wedge-LOK; when it reaches the frame, it is dissipated via either cooling fins or cold plates.

VME card with CCA

Wedge-LOK

System with cold plates (blue)

When should MicroTCA.1 systems be used?

The basic specification MicroTCA.0 defines shock and vibration values compliant with performance level DL1 of IEC 61587-1. This means acceleration rates of 7 g for shock impact and an acceleration amplitude of 0.5 g in the case of vibration loads. If the requirements prevailing in the application location are more stringent, MicroTCA.1 should be used.

What is the difference between MicroTCA and Rugged MicroTCA?

A distinction needs to be made here between the 3 different secondary specifications for Rugged MicroTCA:

MicroTCA.1:
The only difference is the front panel on the AdvancedMC modules used. At the top and bottom there is a flange with screw interlock. The system might also have to be made more durable.

MicroTCA.2:
Specification work has not yet got underway. As such, it is not clear what form the solution will take.

MicroTCA.3:
The specification is currently under development but work is not yet complete. Therefore, differences between it and MicroTCA.0 cannot yet be described in detail. It seems certain that the AdvancedMC modules will be fastened to the system using Wedge-LOKs and this specification will provide the basis for applications in the area of defense.

What shock and vibration values have been defined for MicroTCA.1?

Vibration sinusoidal

• Frequency 2 Hz to 200 Hz
• Amplitude 10 mm
• Acceleration 30 m/s
• 1 octave/min
• 3 axes/10 cycles per axis

Mechanical shock

• 25 g/18 ms half sine
• 3 shocks in 2 directions in all 3 axes

What shock and vibration values have been defined for MicroTCA.3 (preliminary)?

Test 1: (random vibration)

• 50 Hz to 100 Hz increasing at 6 dB/octave
• 100 Hz to 1000 Hz PSD = 0.2 g²/Hz
• 1000 Hz to 2000 Hz decreasing at 6 dB/octave
• 60 min each in all 3 axes

Mechanical shock

• 40 g/11 ms half sine
• 3 shocks in 2 directions in all 3 axes

Test 2: (random vibration)

• 50 Hz to 100 Hz increasing at 6 dB/octave
• 100 Hz to 1000 Hz PSD = 1.5 g²/Hz
• 1000 Hz to 2000 Hz decreasing at 6 dB/octave
• 60 min each in all 3 axes

Mechanical shock

• 50 g/11 ms half sine
• 3 shocks in 2 directions in all 3 axes

How is the shock and vibration test carried out?

The first thing stipulated by the Rugged MicroTCA specifications MicroTCA.1 and .3 is the test for the connector. A test AdvancedMC module is connected firmly to the connector in a test mount. During the shock and vibration test, 8 pairs of contacts on the connector are checked for discontinuity. Discontinuity is defined as an increase in resistance of >10 ohm over a period of >10 ns. If such discontinuity is detected, the test is failed.

The specifications also define a test for the rack or system. This simply checks whether the mechanism is able to withstand these acceleration rates.

Schroff goes a step further, testing the MicroTCA rack (the basis of all Schroff MicroTCA systems) for the electrical discontinuity referred to above during shock and vibration testing.

Why does Rugged MicroTCA require a different screw connection than VME or CompactPCI?

With VME and CompactPCI, a pair of connectors is inserted between the daughterboard and the backplane, permitting some tolerance in the connection depth. In other words, when connected, the daughterboard connector does not sit fully on the connector base of the backplane connector and the pair of connectors absorbs the tolerances of the mechanism.

In the case of the direct connector (card-edge) used with MicroTCA, the daughterboard is pushed into the backplane connector as far as the stop and held in this position by the interlock on the front panel. Tolerances in the mechanism mean that a gap of up to 1.6 mm can develop between the front of the rack and the front panel. If the front panel is then screwed into place, force is exerted on the PCB and the base of the backplane connector; in the case of high rates of acceleration, this can damage the connector or the electronics beyond repair.

Do different AdvancedMC modules have to be used for MicroTCA.1?

AdvancedMC modules for MicroTCA.1 simply have to have a different front panel with an upper and lower flange and the interlock screws. The front panels can be replaced easily. Many AdvancedMC manufacturers offer their AdvancedMC modules with both types of front panel as standard. Schroff can also manufacture customer-specific rugged MicroTCA front panels for AdvancedMC modules.

Do different AdvancedMC carriers have to be used for rugged AdvancedMC modules?

The additional interlock screws on the AdvancedMC modules mean that compatible AdvancedMC carriers must also be used. These support the connection of rugged modules. These carriers are available in mid-size and full-size. A maximum of 3 single modules can be installed in the carrier (or 2 single modules and 1 double module). These carriers are usually defined on a customer-specific basis.