HI,
Also, when doing the temp soak also do a "4 corner" test. By 4 corner I
mean vary internal supply voltages just above and just below ( 2 cases)
max and min specification at both high and low temperatures. (2 x 2 = 4)
This help flush out design errors and component issues.
It is a pain doing this but wow do you sleep easier at night! :-)
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rivera, Raye
Sent: Wednesday, June 08, 2011 8:43 PM
To: [log in to unmask]
Subject: Re: [TN] How to determine Burn In duration?
Hi Robert,
Thanks for the reply. Those are some good ideas. I've never heard of the
approach of soaking at high temp, then doing a quick test before. That
sounds promising. We do some shake and bake testing on new products to
evaluate reliability much as you suggest.
The burn in process I am looking at is not so much a reliability test as an
attempt to force out any infant failures before the product leaves the
factory. The theory is that the right burn in duration will force out infant
failures but not significantly decrease the life of the unit.
Best regards,
Raye Rivera
QA Manager * Canoga Perkins * 818-678-3872 * [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Wednesday, June 08, 2011 2:21 PM
To: [log in to unmask]
Subject: Re: [TN] How to determine Burn In duration?
Hi,
This is more of a 2 cent version of help I pulled from my own experience.
You want to test for the failure types you expect to dominate. I generally
think of two failures types, design and implementation.
Thermal cycling and shake on a small number of units will probably give you
more data on reliability than setting up 100 units and running them for 48
hours at 50 C. You mention smaller number of units so I would verify design
margin and mechanical assembly to insure a solid design and process.
You want to attempt to excite any failure modes, either mechanical or
electrical. I like to take a powered down unit, soak it at 90C, then turn it
on for a short functional test. Repeat this at higher temps until the unit
fails. The idea is to find where electrical parameters shift with temp.
Soaking at high temp followed with a quick test allows elevated temp testing
of all components without frying key power components.
Many years ago I used this to check boards using 64K Bit DRAMS. (Yes it was
a while back.) But wow did it screen out bad components, you could see
major differences from lot to lot.
Also, test at low temps. Al caps really change value at low temps.
Do you have any existing failure data? What does it look like?
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rivera, Raye
Sent: Wednesday, June 08, 2011 5:00 PM
To: [log in to unmask]
Subject: [TN] How to determine Burn In duration?
Hello Technetters,
Does anyone know of a good reference on how to reasonably set the duration
for burn in of products? I haven't been able to locate much information on
this topic.
Our products are primarily fiber optic telecom equipment. We burn them in at
50 degrees C for 48 hours. This procedure was set up before my time and I do
not know how it was arrived at.
Lacking any better approach, I would probably put 10 or so units into a long
term burn in experiment and measure time to failure. Then, attempt to fit to
a Weibull distribution and see if I can get a theoretical model for what
percentage will fail after X hours of burn in. I'm not sure if this is
reasonable because the sample is small and the time to failure may be quite
long.
Does anyone know of a better approach? Thanks all!
Best regards,
Raye Rivera
QA Manager * Canoga Perkins
20600 Prairie Street * Chatsworth * CA 91311-6008
818-678-3872 * [log in to unmask]
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