The highly accelerated stress test (HAST) method was first proposed by Jeffrey E. Gunn, Sushil K. Malik, and Purabi M. Mazumdar of IBM. The acceleration factor for elevated humidity is empirically derived to be :

AF_\text = e^,

\text

is a value which normally goes from 0.1 to 0.15 where ''RH''_s is the stressed humidity, ''RH''_o 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 :

AF_T = e^,

where ''E''_a is the activation energy for the temperature-induced failure (most often 0.7 eV for electronics), ''k'' is the

Boltzmann constant The Boltzmann constant ( or ) is the proportionality factor that relates the average relative kinetic energy of particles in a gas with the thermodynamic temperature of the gas. It occurs in the definitions of the kelvin and the gas constant, ...

, ''T''_o is the

operating temperature An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the de ...

kelvin The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phys ...

s, and ''T''_s is the stressed temperature. Therefore the total acceleration factor for unbiased HAST testing is :

AF_\text = AF_\text \cdot AF_T =
 e^
 e^.

References

{{DEFAULTSORT:Highly Accelerated Stress Test Reliability engineering