High Temperature Operating Life (HTOL) Test

The High Temperature Operating Life (HTOL) or steady-state life test is performed to determine the reliability of devices under operation at high temperature conditions over an extended period of time. It consists of subjecting the parts to a specified bias or electrical stressing, for a specified amount of time, and at a specified high temperature (essentially just a long-term burn-in).

Unlike production burn-in which accelerates early life failures, HTOL testing is applied to assess the potential operating lifetimes of the sample population (hence the term 'life test'). It is therefore more concerned with acceleration of wear-out failures. As such, life tests should have sufficient durations to assure that the results are not due to early life failures or infant mortality.

The test duration may be decreased by increasing the ambient temperature for conditions A to E (refer to Table I, Method 1005). Unless otherwise specified, all intermediate and end-point electrical tests must be performed on the parts within 96 hours (24 hours for Ta>=175 deg C) after their removal from the specified burn-in conditions. If not specified, an intermediate electrical testing shall be performed after 168 (+72,-0) hours and after 504 (+168,-0) hours.

Since HTOL is simply long-term burn-in, it is accomplished by utilizing any burn-in oven capable of operating continuously over long durations.

Failure mechanisms accelerated by HTOL include Time-Dependent Dielectric Breakdown (TDDB), electromigration, hot carrier effects, charge effects, mobile ionic contamination, etc.

Figure 1. Examples of Burn-in Ovens

Mil Std 883, Method 1005 Specs :

- generally 1000 hours min. at 125 deg C

- max. rated Tc or Ta < 200 deg C (Class B)

- max. rated Tc or Ta < 175 deg C (Class S)

- Condition A : steady-state, reverse bias

- Condition B : steady-state, forward bias

- Condition C : steady-state, power/reverse bias

- Condition D : steady-state, parallel excitation

- Condition E : steady-state, ring oscillator

- Condition F : steady-state, temp.-accelerated

Refer also to JEDEC JESD22-A108.

Other HTOL Conditions (depending on use) :

- Ta=125C, 1000H, max Pdis

- Ta=150C, 500H, max Pdis

- 125C<Tj<150C, 1000H, max Pdis

- 150<Tj<175C, 500H, max Pdis

- Ta=125C, 1000H, Dyn, max Pdis

- Ta=150C, 500 H, Dyn, max Pdis

- 125C<Tj<150C, 1000 H, Dyn, max Pdis

- 150<Tj<175C, 500 H, Dyn, max Pdis

- Ta=125C, 120H, max Pdis

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