Jeff,
Just to add a bit to this thread. The purpose of your 11 hour test is to
prevent early failures from the going to the field. Look at the percent of
failures discovered during burn-in. What would be the effect of having the
failed units become warranty claims? This will answer to your question.
The sampling method used by Richard's company will detect any change in the
reliability of the product. It does not prevent premature failures from
going to customers for 80 to 97% of the units manufactured. Another part of
the equation is whether the level of field failures under the present system
is acceptable. An analysis of these failures may show that other types of
stress screening might be appropriate in your circumstances.
The real answer to this question is economics. Does the cost of stress
screening exceed the cost of increased warranty claims and increased
customer disatisfaction, and is there a more economical way of eliminating
those defects? There is an obivous difference in the costs of failure for
the company making the voice circuits that go into stuffed animals versus a
company making flight critical hardware.
Don Vischulis
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Richard van Beveren
Sent: Monday, April 08, 2002 8:47 PM
To: [log in to unmask]
Subject: Re: [TN] Powered up burn- in test
Jeff,
We're in the lighting controls game and subject a percentage of all our
products to a "burn in" or, to use a better term, "stress screening" test.
For us it is our primary source of reliability information. It's function
in terms of catching systemtic problems in manufacture is secondary (99% of
those should be picked up at MDA and functional testing)
We do not test 100% - we start at 20% and reduce it as historical data
indicates is reasonable (for some products (for which we have a lot of
data), we are only screening 3%). As for temperature, we aim to get as
close as possible to (but not exceed) maximum operating temperature of the
product. Our test duration is typically 48 hours.
So, yep, I think it certainly has a place, but regular assessment to ensure
it is still providing useful information is not such a bad thing either.
I guess it depends on the product and Class, but "burning in" or "screening"
100% sounds excessive to someone producing Class 2 - you could probably
reduce the percentage greatly without a huge drop in data quality.
Richard van Beveren
NEWTRONICS PTY LTD
-----Original Message-----
From: Landes, Jeff [mailto:[log in to unmask]]
Sent: Tuesday, 9 April 2002 06:46
To: [log in to unmask]
Subject: [TN] Powered up burn- in test
Hi all,
Historically we've subjected our units to a "power on" 11hr "burn-in" at
125F (prior to final testing). This burn-in costs very little to perform,
since a hot room is already set up.
There has been talk of discontinuing this practice -- In fact the subject
comes up at least once a year.
Question.... Is it not just good practice to have a unit powered up for a
period of time before shipping it to an end user? Otherwise it has only a
minute, or so, of history (during test) under power. Is it not "better than
nothing"?
Any feedback would be appreciated. What are others doing out there?
Jeff
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