NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.

Independent NASA Test of
Actel SX-A, SX-S, and SX-SU
Field Programmable Gate Arrays (FPGAs)

KM1 Anomalies

• S/N 37887: Functional Failure at Cold Temperature Test

• S/N 37858: Failed functional array testing.

• S/N 38061: Out of Specification V_IH

• S/N 38057: V_IH anomaly.

• S/N 37990: t_PD anomaly

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S/N 37887: Functional Failure at Cold Temperature Test

Summary:

After being successfully programmed, S/N 37887 exhibited functional failure at the cold temperature test.  This was the first test of the device, room temperature ATE test was not conducted first.

The unit was pulled from the test population and was submitted to failure analysis for evaluation.  The failure is attributed to a damaged K antifuse.

Analysis Results

• Failed functional tests during initial testing (-55 ºC)

  • Failed on array_monitor and array_out signals

  • Unit failed both 1 MHz and 50 MHz functional tests

• Bench Testing

  • Using Silicon Explorer, the failure was isolated to occur between net C2_17 and C2_18 in the array shift register

    • For reference unit, the two nets show a 1 clock cycle delay between output transitions

      • External reset edge transition used for reference point

    • For S/N 37887, the two nets show effectively no delay between output transitions, which is a signature of a hold time violation.

  • This type of failing signature suggests K-antifuse anomaly

• Performed Manual antifuse check on the suspected K-antifuse for module C2_18

  • Check indicated a higher resistance in the programming path

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S/N 37858: Failed functional array testing.

Summary

After being successfully programmed, S/N 37858 proceeded through step KM1-1A, 50 hours of HTOL testing.  The conditions were T = 125 °C, V_CCA = 2.75V, and V_CCI = 4.0V.  The device proceeded through step KM1-1B, identical environmental and electrical conditions to step KM1-1A.  The duration of step KM1-1B was 200 hours.  Subsequent ATE testing indicated a failure for functional array testing.  The device passed all other tests, including the propagation delay test.

The failure is attributed to a damaged K antifuse.

Additional information.

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S/N 38061: Out of Specification V_IH

Summary

S/N 38061, at the conclusion of KM1-2, 500 hours of operation at 125 ºC exposure, exhibited an out of specification V_IH measurement of approximately 3.7 volts.  The subject device was returned to the population and it's performance will be monitored to observe any trends in the parametric measurements, prior to destructive physical analysis.

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S/N 38057: V_IH anomaly.

Summary

S/N 38057 failed V_IH (CMOS) after KM1-3, 750 hours of +125 ºC operation.

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S/N 37990: t_PD anomaly

Summary

S/N 37990 was observed to have a t_PD anomaly at the conclusion of KM1-5 (-55 ºC).  Previously, the device had been subjected to 1,000 hours of +125 ºC testing.

The failure is attributed to a damaged F antifuse.

Additional Data

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