Prognostics Approach For Power Mosfet Under Thermal-Stress Aging

The methodology utilizes thermal and power cycling to accelerate the life of the devices. The major failure mechanism for the stress conditions is die attachment degradation, typical for discrete devices with lead free solder die attachment.

It has been determined that die attach degradation results in an increase in ON-state resistance due to its dependence on junction temperature. Increasing resistance, thus, can be used as a precursor of failure for the die-attach failure mechanism under thermal stress. A feature based on normalized ON-resistance is computed from in-situ measurements of the electro-thermal response.