Highly accelerated stress test

The highly accelerated stress test (HAST) method was invented by Nihal Sinnadurai while working as a Research Engineer at British Telecommunications Research Laboratories in 1968 in order to perform highly accelerated reliability testing of electronics components that are likely to encounter humid environments during normal (ambient) operation. The method uses the principle of a non-saturating autoclave designed and engineered with no moving parts, to deliver close temperature (<1°C) and humidity (<2%RH) control and a high reliability of the stress equipment. Nihal Sinnadurai and his team carried out many millions of device hours of reliability stress testing in HAST chambers, and arrived at a clear correlation with a humidity exponent as the stress accelerating agent. The generic Sinnadurai-HAST (SH) Model he developed by analysing the experimentally determined data, is:$t\_\{amb\}/t\_\{s\}\; =\; e^\{X\; [(RH\_s)^n-(RH\_\{amb\})^n]\; +(EA/k)(1/T\_\{amb\}-1/T\_s)\}$

When applied to semiconductor devices, the empirical SH Model expression is:$t\_s=175000/e^\{0.00044\; [(RH\_s)^2-(RH\_\{amb\})^2]\; +7000(1/T\_\{amb\}-1/T\_s)\}$

When applied to thick-film elements, the empirical SH Model is:$t\_s\; =\; 175000/e^\{0.025\; [(RH\_s)-(RH\_\{amb\})]\; +8120(1/T\_\{amb\}-1/T\_s)\}$

where 175000 is approximately 20 years and is the required lifetime (t_amb) at the ambient condition, RH_s is the applied humidity stress, RH_amb is the humidity at the application ambient, T_s is the applied stress absolute temperature and T_amb is the application ambient temperature.

References

# http://cat.inist.fr/?aModele=afficheN&cpsidt=1017026
# F. N. Sinnadurai, "The Accelerated Ageing of Semiconductor Devices in Environments Containing a High Vapour Pressure of Water", Microelectronics and Reliability, Vol. 13, pp 23-27, 1974.
# F. N. Sinnadurai, "Handbook of Microelectronics Packaging and Interconnection Technologies", Electrochemical Publications, 1985.
# N. Sinnadurai "Plastic Packaging is Highly Reliable", IEEE Trans. Reliability, Vol. 45, No. 2, pp 184-193, June 1996.
# N. Sinnadurai, “The Correct Model for, and Use of, HAST”, Proceedings of IEEE Accelerated Stress Workshop, Boston, Massachusetts, September 1999, and 33rd International Symposium on Microelectronics (IMAPS 2000), Boston, Massachusetts (USA), Sep 20-22, 2000, pp.733-736.