The prognostic technique for a power MOSFET presented
in this paper is based on accelerated aging of MOSFET
IRF520Npbf in a TO-220 package. 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. An Extended
Kalman filter is used as a model-based prognostics techniques
based on the Bayesian tracking framework.