Accelerated mechanical fatigue interconnect testing method for heavy wire bonds in power modules

Every new development in device performance and
packaging design, due to new materials and design changes
can influence the device reliability drastically. High
performance and high reliability demands in power
electronics over several decades and a short time to market
development, raise the need for very fast reliability testing
methods. In this study a mechanical fatigue testing method
is presented for evaluating the interfacial fatigue resistance
of heavy Al wire bonded interconnects in high power
modules. By separating the concurrent thermal, mechanical
and environmental failure mechanisms a selective
investigation of the desired failure mode is possible. The
setup is designed to reproduce the thermo-mechanical shear
stresses by mechanical means, while provoking the same
lift-off failure mode as in power cycling tests. With a
frequency variable test setup of a few Hz up to several kHz,
measurements from 1E3 up to 1E8 and determining the
influence of the testing frequency on the fatigue life were
possible.