Low Temperature Operating Life (LTOL) Test

The Low Temperature Operating Life (LTOL) test is a test performed to determine the reliability of devices under low 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 low temperature.

The LTOL test is basically just the low temperature equivalent of the HTOL test. In fact, both tests are documented by JEDEC in a single standards spec, JEDEC JESD22-A108.

There are several requirements when powering up a device during LTOL. As in HTOL, the device must not be overstressed nor should it go to thermal runaway. The datasheet limits of the manufacturer must not be exceeded. The stressing must also be continuous, and should only be interrupted at interim readpoints if required. The biasing configuration may be static, pulsed, or even dynamic.

Unless otherwise specified, the ambient temperature for LTOL test shall not exceed the maximum limit of -10 deg C.

Fig. 1. Example of a Low Temperature Burn-in Oven

As in HTOL, electrical testing must be performed within 96 hours after the bias to the device has been removed. A device is considered an LTOL failure if it fails to meet the applicable procurement specification.

The LTOL test is usually performed to check for hot carrier effects, a commonly encountered failure mechanism accelerated by high voltages and low temperatures.

Reliability Tests: Autoclave Test or PCT; Temperature Cycling; Thermal Shock; THB; HAST; HTOL; LTOL; HTS; Solder Heat Resistance Test (SHRT); Other Reliability Tests

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