Failure in time

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The English Failure in Time (abbr .: FIT / German  failures per time ) is a failure rate based on the time interval “one billion hours” (ie failures every 10 9  hours). In addition to the FIT , reference can also be made to the time interval “one million hours” (10 6  h each ). In order to avoid misunderstandings regarding the reference interval, the definition is often given.

application

The numerical value of FIT represents the average number of components that fail within one billion hours. It applies to the respective reference condition and can be converted to the specific operating conditions by applying appropriate factors. Depending on the data collection method, the details of different component libraries for the same components differ. Mixing is possible to a certain extent.

Examples of appropriate FIT information in accordance with the SN 29500 standard are:

Component FIT source
Carbon film resistance ≤ 100kOhm 0.3 SN 29500-4
Universal diode 1 SN 29500-3
Ceramic capacitor (X7R) 2 SN 29500-4
Bipolar transistor 3 SN 29500-2
Quartz Oscillators (XO) 30th SN 29500-4

Norms

The FIT unit is explicitly mentioned in the following standards and norms :

source description
JEDEC JESD85 Describes methods for collecting FIT values.
SN 29500-1 Defines the unit FIT "as failure number in 10 9 component hours" and states values ​​for various components in its following parts. The standard provides information on calculation models for deviations from the reference conditions.
DIN EN 61709 Does not deal centrally with the FIT unit , but contains a reference to this in Appendix B.4.1. Basically, calculation models for failure rates in the event of deviations from reference conditions are described.
ISO 26262 Defines permissible FIT rates for achieving a certain ASIL ( automotive safety integrity level ).

Individual evidence

  1. ↑ a b JEDEC standard: JESD85. Methods for Calculating Failure Rates in Units of FITs. July 2001.
  2. ↑ US MIL Specification: MIL-HDBK-217F: Military Handbook - Reliability Prediction of Electronic Equipment. December 1991.
  3. ↑ a b c Standard DIN EN 61709: Electrical components - Reliability - Reference conditions for failure rates and stress models for conversion. July 2012. Chapter B.4.1: General consideration of the failure rate - general .
  4. ↑ Texas Instruments; NE555 Online Specification ( Memento from April 4, 2011 in the Internet Archive ); accessed on April 9, 2018.
  5. ↑ a b Siemens Standard SN 29500-1: Failure rates of components - expected values, general ; January 2004.
  6. ↑ a b c Siemens Standard SN 29500-4: Failure rates of components - Expected values ​​for passive components ; March 2004.
  7. ↑ Siemens Standard SN 29500-3: Failure rates of components - Expected values ​​of discrete semiconductors ; June 2009.
  8. ↑ Siemens Standard SN 29500-2: Failure Rates of Components - Expected Values of Integrated Circuits ; Sep 2010.