Backplanes and connectors for Rugged MicroTCA

In addition to the mechanical durability of the system, its electrical function does of course also need to be assured in the changed ambient conditions. The card-edge connector with 170 contacts used for MicroTCA was considered to be a particular weakness with regard to shock and vibration. An analysis was, therefore, carried out in advance, to test the connector against the requirements of Rugged MicroTCA. The test conditions are outlined in the MTCA.1 specification.

During the test, measurements were carried out on 8 pairs of contacts distributed across the connector to detect contact discontinuity lasting more than 10 ns. Contact discontinuity is defined as an increase in resistance of > 10 ohm. The test was passed together with the mechanical interlock described above. The connector has also since been tested to MicroTCA.3, and passed.

The test cadidates: 3 double mid-size AdvancedMC modules with weights attached (700 g), standard Schroff guide rails, and a special test backplane

A measuring card developed specifically by Schroff to detect electrical discontinuity < 10 ns

The Rugged MicroTCA specification stipulates that the connector test may only be carried out on a fixed AdvancedMC module and to have the rack or system undergo only mechanical shock and vibration testing. However, Schroff goes a step further here, testing a fully populated MicroTCA rack (the basis for all Schroff MicroTCA systems) for shock and vibration and checking the connector for contact discontinuity at the same time. This is the only way to obtain realistic information about the operational reliability of a MicroTCA.1-compatible system.

Test setup for shock and vibration testing to MicroTCA.1

Shock and vibration values for MicroTCA.1 and MicroTCA.3

MicroTCA.1

Vibration sinusoidal - Frequency 2 Hz to 200 Hz - Amplitude 10 mm - Acceleration 30 m/s2 - 1 Octave/min - 3 axes/10 cycles each axis No contact discontinuity >10 Ω longer than 10 ns

Mechanical shock - 25 g/18 ms half sine - 3 shocks in 2 directions on all 3 axes No contact discontinuity >10 Ω longer than 10 ns

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 on all 3 axes No contact discontinuity >10 Ω longer than 10 ns

Mechanical shock - 40 g/11 ms half sine - 3 shocks in 2 directions on all 3 axes No contact discontinuity >10 Ω longer than 10 ns

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 on all 3 axes No contact discontinuity >10 Ω longer than 10 ns

Mechanical shock - 50 g/11 ms half sine - 3 shocks in 2 directions on all 3 axes No contact discontinuity >10 Ω longer than 10 ns