MTBF calculation with Telcordia SR 332

MTBF-Calculation acc. to Standards        Mil-HDBK-217F      →  Telcordia SR 332        IEC-TR-62380        Siemens SN 29500        FIDES 2009        217Plus        GJB/Z 299C

Telcordia SR-332 was the second electronic reliability prediction standard (after Mil-HDBK-217) and is still the second most popular of all current electronic reliability prediction standards. With its latest edition (issue 4) from 2016, Telcordia SR 332 has undergone by far the most revisions and is therefore the longest maintained electronic reliability prediction standard; it has been consistently kept up to date for many decades: Originally named Bellcore issue 1,2,3,4,5 and 6, then Telcordia SR 332 issue 1,2 3 and 4.

The first picture shows Telcordia SR-332 failure rates versus temperature for a comprehensive electronic system. The graph for the latest issue (issue 4, 2016) is not included. It would be below the issue 3 (2011) curve (a little, but not substantially).

The general methodology of Telcordia SR 332 is quite similar to the Mil-HDBK-217 , however it uses less parameters. In contrast to Mil-HDBK-217, Telcordia SR 332 uses only up to 2 component specific parameters per component type. Aditionally, these 2 parameters are easier to determine (with the # of transistors or gates in ICs being the only exception).
These similar methodologies make it quite easy to transform Mil-HDBK-217 MTBF figures into Telcordia MTBF figures (and vice versa), provided that a reliability prediction software is used.

Telcordia shares the same environment types with Mil-HDBK-217, however, the latter offers even more environment types. The same is true for component coverage: Telcordia uses the same component categories like Mil-HDBK-217, but Mil-HDBK-217 offers more component categories.

Telcordia has some unique differentiators:

• Calculated MTBFs can be improved (or impaired) using laboratory test data and field failure data
  
• same for Burn-In data
  
• Telcordia uses the gamma distribution with standard deviations for all component failure rates.
  
• Therefore Telcordia SR 332 MTBFs can be featured with confidence bounds, resulting in sligthly lower MTBFs but with higher statistical certainty. 
• This makes the Telcordia SR 332 standard quite complex (however, the french standard IEC-TR-62380 is even more complex, in a different way).
  
• Some Telcordia SR 332 software don't offer this feature, and many analysts aren't even aware of it.
  

Taking into consideration every aspect discussed so far, Telcordia SR 332 is probably the best available standard of all electronic reliability prediction standards.
A comprehensive MTBF comparison between Siemens SN 29500, Telcordia SR 332 and Mil-HDBK-217F using real electronic equipment is shown in the picture below.
The Excel file from which all pictures on this page have been generated can be obtained on request.