igbt失效率fit和平均无故障时间mtbf的定义.pdfVIP

APPLICATION NOTE Page 1 von 2 Definition of FIT and MTBF A failure rate λ=is defined by the number of failures r during a specific test time t of n components: r λ = n ⋅t The unit for failure rates is 1 fit (failures in time) = 1*10-9h-1, meaning one failure in 109 operation hours of the device. A component specified with 100 fit is therefore expected to operate 107 hours. Example: Testing 4000 components for 5000 hours with 2 failures in this time leads to a failure rate of 2 −7 −1 λ = = 1⋅10 h 4000 *5000h or expressed in fit: 10−7 = −9 −1 fit = 100fit 10 h The failure rate or fit value is used to calculate the MTBF (mean time between failures) of a complete equipment existing of i separate components with individual failure rates λ : i MTBF = 1 / Σ λi Example: An equipment is built of 50 components with 250 fit each, which adds up to a MTBF of 1 / (50×250fit) = 80.000 h. The equipment is operated 18 hours a day and 300 days a year under the specified operating conditions. The expected lifetime is therefore: 80.000 h / (300*18 h) = 14.8 years. eupec GmbH + Co KG Max-Planck-Straße 5