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June 2011

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Subject:
From:
Jim Carlson <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 8 Jun 2011 17:19:09 -0400
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Raye,

Do you receive legacy units, that have been subjected to this burn-in,
back for repair from your customers, or are they disposable or repaired
elsewhere?  If you get them back, do you monitor these customer returns
to determine any failure percentage, and time to failure calculations?  

In other words, you need to evaluate how well your present burn-in is
working, before making changes.  It may be sufficient for your design
and your customer use environment.

Have your products design fundamentally changed, or are using very
similar parts and construction?  What are the typical failure modes of
your components, and how would you precipitate those failure modes?
What is the rated temperature range of your products? 

Personally, I would say a stagnant burn-in at 50 C won't precipitate
many failures.  Temperature cycling while powering on/off is generally
used for ESS, as well as vibration if your products are used on the
move.

MIL-HDBK-344 may be good reading for you to see the military products
viewpoints.


Jim Carlson 
Quality/Configuration Manager 
L-3 Communications 
Applied Signal & Image Technology 
443-457-1111 Ext. 238



-----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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