Circuit Boards Example

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27 circuit boards were put in an accelerated life test, with temperature as the stress (or stimuli). The goal is to estimate the reliability of the circuit boards after 10 years when operating at 100ºC. The following data were obtained:


Test Chamber Temperature 463K
# of units Time, hr Observation
1 2,403 Failure
1 2,668 Unrelated Failure
1 3,669 Test Fixture Failure
1 3,863 Failure
2 4,400 Test Fixture Failure
2 4,767 Failure
1 5,219 Failure
4 5,276 Power Surge Failure
2 7,517 Failure
1 7,840 Failure
2 8,025 Failure
1 8,571 Removed - Test Terminated


Test Chamber Temperature 488K
# of units Time, hr Observation
2 346 Power Regulator Failure
1 1,416 Failure
1 2,197 Unrelated Failure
1 2,533 Failure
1 2,630 Failure
1 2,701 Test Fixture Failure
1 3,000 Failure
1 3,489 Failure
1 6,720 Removed - Test Terminated


The data were entered in the ALTA standard folio and analyzed with the Arrhenius-Weibull model. Note that all units that did not fail in the test, but failed for unrelated reasons, were entered as suspensions. The reliability after 10 years at 100ºC is estimated to be 45.67%, as shown in the following reliability plot. This reliability value can also be obtained via the Quick Calculation Pad (QCP).


Reliability plot at use stress level
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