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Old 29th April, 2004, 09:00 PM
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Originally Posted by cadaveca
MTBF= Manufacturer Tested Before Fail.. I don't know where you go that from, but in engineering land, MTBF = Mean Time Between Failures. It is a method of determining the reliability of a part.

There are two types of MTBF, predicted and actual or demonstrated.

Predicted MTBF is done by operating the device under extreme conditions (i.e. beyond design limits), and then seeing how long it takes to fail. This is how you take a brand new device and claim that it has a MTBF of 100,000 hours (roughly 10 years). There is a lot of statistical data that goes into modeling the failure modes and rates, so this is not just a wild guess. It is backed up by solid mathematics.

Demonstrated MTBF is done by operating the device at maximum stress until it dies (this is also called 'Life Testing'). You only get this with devices that have been in production for at least as long as the demonstrated MTBF figure.

Most companies will take a few products from each batch and subject them to reliability testing to help ensure that their manufacturing process is producing the quality of product they thing it is. SOME companies will also take a few products from each batch and put them through life testing. If you want to know how good a product you are getting, one of the first questions out of your mouth should be 'Is that MTBF predicted or demonstrated'?

This is one of the reasons that many mass-produced cpus make the transition to the embedded market only after they are obsolete in the mass market: it takes that long to build the body of data necessary to demonstrate the device's reliability. Engineers for embedded applications tend to be a rather conservative bunch to start with. Most of them will run a sales guy out of town on a rail if his MTBF is predicted rather than demonstrated.

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