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# SN751177: DPPM/FIT/MTBF estimator & Temperature Change FIT

Part Number: SN751177

Hi,

In Temperature Change FIT,

Q1. What is Application Temperature?

Q2. What is Qualification Temperature?

Q3. How we can use FIT at Activation Energy, 0.3 eV, 0.7eV and 1.0eV? It would be helpful to give me some examples.

In DPPM/FIT/MTBF estimator,

Q4. MTBF / FIT shows MTBF=1.44*10^9、FIT=0.7. Are these value at 55C temperature?

If the question for Temperature Change FIT is not in this thread, please let me know where I should ask these questions.

Best regards,

Hide

• Hello Hide-san,

The application temperature is the ambient operating temperature used in the end application.  The qualification temperature is the temperature at which the stress test is performed.  This is found on the DPPM/FIT/MTBF estimator table (see below value of 125 C): The activation energies can vary depending on the process technology used and the type of defects targeted for the FIT/DPPM estimate.  (For example, a given process technology an oxide defect may have an activation energy of 0.3 - 0.5 eV while electromigration of a contact/via may have an activation energy of 0.9 eV.)

You are correct that the data provided in the DPPM/FIT/MTBF estimator table assumes an ambient temperature of 55 C.

For further reference, you may find this app note on calculating FIT useful: .

If you have any further questions please let me know.

Regards,
Max Robertson

• In reply to Max Robertson:

Hi Max,

In application note (SPRABY3) you attached, I would like to know the relation between DPPM and MTBF(FIT).

Formula (1) & (2) in application note (SPRABY3), how DPPM relate to FIT value? In this Formula, "f = number of failures" means DPPM?

Best Regards,

Hide

• In reply to Hideyuki Takisawa:

Max,

In addition, in Temperature change FIT, if the following parameters put the each item, FIT is calculated, my understanding correct?

The result of MTTF at 0.7 eV was 1.43e+9 compare with 1.44 e+9 by DPPM/FIT/MTBF estimator. Is the difference from simulation accuracy?

・Application Temperature   = +55℃

・Qualification Temperature = +125℃

・DPPM = 56

Best regards,

Hide

• In reply to Hideyuki Takisawa:

Hello Hide-san,

You can find the definitions for FIT and DPPM and how they relate to one another on this page:

www.ti.com/.../reliability-terminology.html

(It explains it better than I can, although if you have any questions on it please let me know.)

You are correct about the usage of the "Temperature change FIT" website. The differences between the result you see on it and the DPPM/FIT/MTBF estimator table should be due to rounding differences. In both cases the MTBF should be calculated as 1E9 / FIT.

Best regards,
Max
• In reply to Max Robertson:

Max,

I'm sorry for my late response.
Let me ask you the followings.

1. We would like to know SN751177N DPPM at 85C application temperature. Which tool give us that value?
2. In DPPM sample size calculator, Conf level (%) option has 60% and 90%. What is 90% for? Space device?
3. In case of SN751177N MTBF, Sample size is 37070. Fails is 1. Once put these numbers in DPPM sample size calculator, predicted DPPM is 54.55. Is this ELFR-DPPM? In MTBF estimator, it says ELFR-DPPM=56.
4. In case of SN751177N DPPM/FIT/MTBF estimator, what’s the Sample size difference in ELFR supporting data (36407) and MTBF / FIT supporting data (37070)?

Best regards,
Hide
• In reply to Hideyuki Takisawa:

Hide-san,

1.)    The temperature change FIT calculator should be used:  http://www.ti.com/support-quality/reliability/temperature-change-FIT.html

Reference the data in DPPM / FIT / MTBF estimator for SN751177N at 125 C test temperature and usage temperature 55 C: Enter values 85 C for application temperature, 125 C for qualification temperature, and 56 for DPPM. This will output the below FIT rates at different activation energies: The DPPM (defective parts per million) would depend on the FIT as well as the number of operating hours (t). Use above FIT values to calculate DPPM per the application operating hours in the below formula:

DPPM = FIT * t / 1000

2.)    Typical value used for confidence level is 60 percent. The 90 percent is provided as a reference for calculating higher statistical significance.

3.)    No, the ELFR-DPPM (Early Life Failure Rate) uses the sample size 36407 and 1 fail to calculate DPPM = 56

4.)    ELFR sample size is used specifically to calculate the ELFR-DPPM.  This is a different reliability test condition specifically for calculating “early life fails”.  The reliability data for MTBF/FIT calculations use a different sample size because different reliability test data is used to calculate the “Normal Life” reliability.  More information on the terminology can be found here:  http://www.ti.com/support-quality/reliability/reliability-terminology.html

Regards,
Max

• In reply to Max Robertson:

Hi Max,