Related Topics:

Time-Dependent Stress Profiles

ALTA Single-Stress Example

ALTA Two-Stress Example

Stress Profile Example

A reliability engineer is asked to determine, with a confidence level of 90%, whether an electronic component has a B10 life of at least 350 hours under ordinary conditions.

To simplify the analysis, the engineer will assume the ordinary stress conditions for the component consist of a constant stress level of 2 V. However, because the ordinary stress conditions are known to involve escalating stress values, the component will be subjected to a time-varying voltage stress during testing. The following table describes the stress values will be applied during the test.

Starting Time (Hr) Ending Time (Hr) Stress Level (V)
0 250 2
250 350 3
350 370 4
370 380 5
380 390 6
390 400 7

 

All eleven units were tested to failure using the same stress profile. The following failure times were observed in the test.

Failure Time (Hr) Stress Level
280 Time-varying
310 Time-varying
330 Time-varying
352 Time-varying
360 Time-varying
366 Time-varying
371 Time-varying
374 Time-varying
378 Time-varying
381 Time-varying
385 Time-varying

 

The results show that the component's estimated B10 life is 507.9438 hours. The lower one-sided 90% confidence bound is shown to be 300.4821 hours. Thus, the test's results do not show with 90% confidence that the component's B10 life is at least 350 hours.

 

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