David,
Very good observations!
Regarding MTBF:
1) Even military component MTBF is suspect; MIL-HDBK-217 is decomissioned;
its database is over a decade old; its algorithms for plastic and multi-lead
parts are obsolete. Telcordia SR-332 is more real-life, but component MTBF
is vendor- and stress related; HALT is sensitive to vendor differences.
2) Ranking the approaches to MTBF
Prediction - not very accurate but rapid turnaround
Laboratory test - more accurate, HALT is quicker than a life test
but requires FA and corrective action loop
Observed data - most accurate, but turnaround is too slow to
prevent field problems
An efficient approach is to HALT test new technology during the prototype
phase.
David
-----Original Message-----
From: David Sproul [mailto:[email protected]]
Sent: Thursday, August 01, 2002 6:22 AM
To: Brian O'Connell
Cc: EMC-PSTC
Subject: RE: HALT and HAAS
Hello group,
I would actually disagree that HALT is misnamed, as Brian suggests. I have
seen clients find mechanical and electronic weakness in their designs within
days of testing that may otherwise have taken many weeks of conventional
temperature and vibration testing, or even years in the field, before they
were discovered.
By fixing these problems these companies were able to strengthen their
product still further and greatly reduce, and in some cases eradicate,
repairs or returns from customers.
I may be wrong, but is it not the case that components destined for non
military use do not come with MTBF figures, thus making it impossible to
calculate accurate MTBF figures for products they are used in? I must
stress that I this is more supposition that known fact. If it is so, then
perhaps HALT could be seen as a commercial alternative to MTBF.
I think HAAS may actually be HASS, which stands for highly accelerated
stress screening. This I'm afraid I've had very little experience of, but
It seems to take the product lessons learned from your HALT testing and
apply them, in a less destructive manner, to the manufacturing process.
HALT and HASS are very expensive and must be weighed against perceived
potential savings from reduced field repairs or replacements. I know it is
not for all companies. I used to work for a large British manufacturer of
military electronics who made as much money (if not more) from spares and
repairs, as they did from the original product sales.
I hope this has helped.
Best regards,
David Sproul.
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Brian O'Connell
Sent: 31 July 2002 14:12
To: [email protected]
Subject: RE: HALT and HAAS
Geez, just jump to Google. HALT-> misnamed: Highly Accelerated Life Testing.
Actually has noting to do with Life-time or MTBF-type longevity analysis.
Look at the Calmer web site; they were one of the pioneers of HALT. Also, GM
has published an engineering standard, GMW8287, that provides a decent
overview of HALT and HASS/HASA processes.
There may be minimal ROI for simple digital stuff, but mixed-signal and/or
more complex mechanical constructions should be subject to HALT, and perhaps
HASS follow-up.
If your manufacturing and design engineers take the time to actually READ
your HALT report and take corrective action, you will probably find that RMA
problems are greatly reduced.
In any case, playing with liquid nitrogen is great fun...
Brian
-----Original Message-----
From: Peter Merguerian [mailto:[email protected]]
Sent: Wednesday, July 31, 2002 3:38 AM
To: "EMC-PSTC (E-mail)" <
Subject: HALT and HAAS
Dear All,
1. Has anyone heard of HALT and HAAS?
2. What are some overseas labs (in Europe, North America and Asia) testing
for HALT and HAAS?
3. What does a manufacturer testing to HALT and HAAS gain?
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