Werner,

 This is Nancy. Part of my dumb ( dump) question I ask Warren  in a note to Guenter was what is HASS. 
Oh and thanks for ESS.
Nancy T.

>>> [log in to unmask] 03/12/02 01:07PM >>>
Hi Warren,
You are the victim of the sloppy language/terminology use that has recently
become really bad.
You are asking which is the "best" test for relilability screening of PWAs
with uBGA product:
>1) HASS type test with temp change >30C/min with vibration (20-30 GRMs) for a
>period of 2-4 hours (great for mechanical stressing)
>2) ESS slow temp change 5C/min but a longer test time of 72-100 hours this
>might allow chemical reactions to happen.

A: HASS is NOT a procedure suitable for screening purposes of product; it has
some value for testing the 'robustness' of design prototypes but has no place
in product testing.
ESS, by its very name 'Environmental Stress Screening' indicates its use;
there is no  reason why ESS should be at  slow temp change of 5C/min--in fact
many ESS procedures include T-shock above 30C/min.
There is no such thing as a generic ESS--the design of an ESS procedure
depends on its purpose

Werner Engelmaier

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