Nancy,

I disagree with Werner's statement about HASS. HASS is the acronym for
Highly Accelerated Stress Screening and is best described as a very
accelerated ESS test and thus its place is in product testing. HASS is
always preceded by a HALT test. HALT is the acronym for Highly Accelerated
Life Testing, which unfortunately is a misleading name since it is not at
all a life test. A better name is Accelerated Stress Test. HALT is a test
for testing the 'robustness' of design prototypes. If you want to learn more
about HALT and HASS, I can recommend the paper written by Neill Doertenbach
that you can find on the following webpage
http://www.qualmark.com/content/OurLibrary_TechnicalPapers.html

Per-Erik Tegehall
IVF
Sweden

-----Ursprungligt meddelande-----
Från: Nancy Trumbull [mailto:[log in to unmask]]
Skickat: den 12 mars 2002 20:45
Till: [log in to unmask]
Ämne: Re: [TN] Thermal Shock


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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