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] ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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