BackToBasics: MTBF in Electronics

MTBF stands for Mean Time Between Failures. MTBF is a statistical measure of the average time between failures for a repairable system during normal operation. Essentially, it helps predict the period when a system will function without failure. It’s critical for reliability engineering.
MTBF is calculated by taking the total operational time of all units and dividing it by the number of failures observed. It becomes valid only if you have a large sample size of parts tested. You can’t just run a single part for X hrs and claim the MTBF to be the time, when that part fails. Larger the sample size, better the result. MTBF provides an estimate of the reliability and performance of electronic components. This information is crucial for industries where reliability is critical, such as aerospace, automotive, and medical devices. It also helps engineers identify weak points in their designs, allowing them to make necessary improvements to enhance reliability because overall reliability still depends on its weakest link.



There are other related reliability terms similar to MTBF like

FIT (Failures in Time): Indicates the number of failures per billion hours of operation.
DPPM (Defective Parts Per Million): Number of defective parts in a million shipped parts.
MTTF (Mean Time To Fail): Average time to failure for non-repairable systems.

Personally in electronics, I have used MTBF values only for LEDs and relay parts to see how long I can reliably drive them. For these parts, values come with the datasheet. Never really used them for ICs. Seems like high-end PCB CAD software like Cadence has built-in modules for these.
I do see its merits in system design as a whole though. Can anyone senior from the industry comment if you use MTBF values while designing and do you follow that safety protocol like designing? Would appreciate some industry insights on this.

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