# Burn-In Arrhenius Acceleration Factor and FIT Rate Calculator

> Source: https://netray.co/tools/burn-in-arrhenius-acceleration-factor-fit-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Calculate the Arrhenius temperature acceleration factor, equivalent use time and a point-estimate FIT rate for burn-in or HTOL results.

## Category

electronics

## Industry

Semiconductors

## Audience

- Reliability engineer
- Product engineer
- Quality engineer

## Tool

**Kind:** calculator

**Inputs:**

#### Activation energy

**Key:** ea

**Type:** slider

**Default:** 0.7

**Min:** 0.2

**Max:** 1.4

**Step:** 0.05

**Unit:** eV

**Help:** Depends on the failure mechanism. 0.7 eV is a common default for generic assessments; use your qualified value if you have it.

#### Use junction temperature

**Key:** t_use

**Type:** number

**Default:** 55

**Min:** -40

**Max:** 150

**Step:** 1

**Unit:** C

#### Stress junction temperature

**Key:** t_stress

**Type:** number

**Default:** 125

**Min:** 25

**Max:** 200

**Step:** 1

**Unit:** C

**Help:** Junction, not oven ambient. Include self-heating.

#### Devices on test

**Key:** devices

**Type:** number

**Default:** 231

**Min:** 1

**Step:** 1

**Unit:** units

#### Stress duration

**Key:** hours

**Type:** number

**Default:** 1000

**Min:** 1

**Step:** 1

**Unit:** hours

#### Failures observed

**Key:** failures

**Type:** number

**Default:** 0

**Min:** 0

**Step:** 1

**Unit:** fails

**Outputs:**

#### Use temperature

**Key:** t_use_k

**Expr:** t_use + 273.15

**Format:** decimal

**Description:** Kelvin.

#### Stress temperature

**Key:** t_stress_k

**Expr:** t_stress + 273.15

**Format:** decimal

**Description:** Kelvin.

#### Acceleration factor

**Key:** af

**Expr:** exp(ea / 0.00008617333 * (1 / t_use_k - 1 / t_stress_k))

**Format:** decimal

**Primary:** true

**Description:** Arrhenius: exp(Ea/k times (1/Tuse minus 1/Tstress)), with k in eV per kelvin.

#### Equivalent device hours at use

**Key:** equiv_hours

**Expr:** devices * hours * af

**Format:** number

#### Equivalent use time per device

**Key:** equiv_years

**Expr:** hours * af / 8760

**Format:** years

**Description:** Using 8760 power-on hours per year.

#### Point-estimate FIT

**Key:** fit

**Expr:** failures / (devices * hours * af) * 1000000000

**Format:** decimal

**Primary:** true

**Description:** Failures per billion device hours. With zero fails, quote an upper confidence bound instead.

**Chart:**

#### Acceleration factor vs activation energy

**Type:** line

**X:** ea

**From:** 0.3

**To:** 1.2

**Steps:** 19

**Series:**

- af

**Disclaimer:** Arrhenius acceleration covers thermally activated mechanisms only. Voltage, humidity and thermal cycling need other models. A point estimate is not a reliability claim: use a chi-square upper confidence bound and your qualification standard (for example JEDEC JESD47 and JESD85) for customer FIT reporting.

## Content

**Intro:** Burn-in and HTOL turn a few weeks at high temperature into years of equivalent field life. This calculator applies the Arrhenius model so you can see the acceleration factor, the equivalent use time and the FIT from your results.

**Sections:**

#### How to use the calculator

**Body:** Enter the activation energy for the mechanism you are screening, the junction temperature in use and under stress, the device count, stress hours and observed failures. The tool returns the acceleration factor, total equivalent device hours, equivalent years per device and a point-estimate FIT. Move the activation energy slider to see how sensitive the result is: a small change in Ea makes a large change in acceleration, which is the main uncertainty in any burn-in claim.

**Bullets:**

- Use junction temperature, including self-heating from power.
- Use the Ea your qualification data supports for the mechanism.
- Do not combine mechanisms with different Ea in one run.

#### The Arrhenius model

**Body:** The acceleration factor is AF = exp[(Ea/k) x (1/Tuse minus 1/Tstress)], where k is Boltzmann's constant, 8.617 times 10 to the minus 5 electron volts per kelvin, and temperatures are in kelvin. FIT is failures per 10 to the 9 device hours, so FIT = failures / (devices x hours x AF) x 10 to the 9. For a zero-failure result, the point estimate is zero, so use a chi-square-based upper bound at your chosen confidence level for any customer commitment.

#### Worked example

**Body:** With Ea of 0.7 eV, 55 C use and 125 C stress, the acceleration factor is about 78. A 1000 hour stress on 231 devices gives roughly 18 million equivalent device hours, or about 8.9 years of use per device. One failure would give a point FIT of about 55. With zero failures, the 60% confidence upper bound is commonly computed with a chi-square of 1.83 for two degrees of freedom, but check the factor required by your standard.

#### Common mistakes

**Body:** Using oven ambient instead of junction temperature will understate the stress. Using the same Ea for every failure type overstates acceleration for low-Ea mechanisms. Reporting zero FIT from a zero-failure test is another error. Finally, check that the hours you enter are actual powered stress hours, not the calendar duration including loading, cooldown and readpoint downtime.

**Cta:** If your reliability results live in spreadsheets and test systems, Netray can help build a private reporting layer that links lots, stress conditions and FIT calculations to your ERP and quality records.

**Faq:**

#### Which activation energy should I use?

**Answer:** Use the value that your qualification data or the relevant standard supports for the specific failure mechanism. Many generic assessments use 0.7 eV, but oxide, metallization and contamination mechanisms have different values, so a single number is a simplification.

#### Why is junction temperature required?

**Answer:** Failure mechanisms respond to the temperature at the die, not the oven air. At high power the junction can be many degrees above ambient. Using ambient understates stress and overstates the time the test represents.

#### What is FIT?

**Answer:** FIT means failures in time: one failure per billion device hours. A part with 50 FIT is expected to fail at a rate of 50 per billion hours of operation under the stated conditions.

#### Can I use this for thermal cycling or humidity tests?

**Answer:** No. Those use different acceleration models, such as Coffin-Manson for cycling and Peck for temperature, humidity and bias. This tool covers Arrhenius temperature acceleration only.

## Search terms

arrhenius acceleration factor calculator, htol acceleration factor, burn-in acceleration factor, fit rate calculator, activation energy calculator reliability, semiconductor reliability calculator, equivalent device hours, jedec htol calculator

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