Engineering:Highly accelerated stress test
From HandWiki
The highly accelerated stress test (HAST) method was first proposed by Jeffrey E. Gunn, Sushil K. Malik, and Purabi M. Mazumdar of IBM.[1] The acceleration factor for elevated humidity is empirically derived to be
- [math]\displaystyle{ AF_\text{H} = e^{\text{const} \cdot (RH_\text{s}^n - RH_\text{o}^n)}, }[/math]
- [math]\displaystyle{ \text{const} }[/math] is a value which normally goes from 0.1 to 0.15
where RHs is the stressed humidity, RHo is the operating-environment humidity, and n is an empirically derived constant (usually 1 < n < 5).
The acceleration factor for elevated temperature is derived to be
- [math]\displaystyle{ AF_T = e^{(E_\text{a}/k)(1/T_\text{o} - 1/T_\text{s})}, }[/math]
where Ea is the activation energy for the temperature-induced failure (most often 0.7 eV for electronics), k is the Boltzmann constant, To is the operating temperature in kelvins, and Ts is the stressed temperature.
Therefore the total acceleration factor for unbiased HAST testing is
- [math]\displaystyle{ AF_\text{HAST} = AF_\text{H} \cdot AF_T = e^{\text{const} \cdot (RH_\text{s}^n - RH_\text{o}^n)} e^{(E_\text{a}/k)(1/T_\text{o} - 1/T_\text{s})}. }[/math]
References
- ↑ Gunn, Jeffrey E.; Malik, Sushil K.; Mazumdar, Purabi M. (April 7–9, 1981). "Highly Accelerated Temperature and Humidity Stress Test Technique (HAST)". 19th International Reliability Physics Symposium. Las Vegas: IEEE. pp. 48–51. doi:10.1109/IRPS.1981.362972.
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