Active power cycling is a standardized and well-established method for reliability assessment and product qualification in power electronics technologies. Repetitive pulses of load current are applied to cause cyclic thermal swings in the p-n junction and in the whole semiconductor device. They induce thermo-mechanical stresses, which ultimately leads to the typical interconnect failure in the ‘devices under test’.

However, these tests are insensitive with respect to new automotive system architectures, in which power electronics devices are exposed to additional loads besides the intrinsic thermal swings. The trends in power electronics towards miniaturization, higher power density, heterogeneous system integration, and the deployment of power electronics in harsher environments combined with longer lifetime and higher uptime requirements strongly increase the reliability demands in general and the need for more improved reliability assessment methodologies in particular. The new testing methods shall be more comprehensive and more efficient, i.e., they shall simultaneously cover the real service conditions better and reduce testing time. One promising approach is the combination of loading factors — such as the superposition of active power cycling by passive thermal cycles. Both loading factors are well-known to cause most relevant failure mechanisms in power electronics. In reality, the power electronic devices are exposed to both factors simultaneously. Hence, this load case should also be replicated in the test.

The paper will report a systematic investigation of such superimposed test schemes, which cover the case of self-heating and passive heating (from neighboring elements) of the power electronics devices under real service conditions. Typical discrete power electronics components in TO-200 packages are selected as test vehicles as they are likewise relevant for the domains of consumer or automotive electronics. The paper details the test concept and discuss the quantitative and qualitative test results.

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