IEEE Electrification Magazine - June 2014 - 49

environments), temperature cycling, moisture, and noise/
vibration/harshness create a harsh environment for the
power electronics and the electric motors.
reliability concerns increase with the trend toward
higher-temperature operation using Wbg power electronic
devices. Wbg devices can operate at temperatures more
than double those of conventional silicon devices. using the full potential
of Wbg devices requires packaging
materials, associated electronics (e.g.,
dc link capacitor), electrical interconnects, and bonded interface attach
materials (at the die-attach interface
and the metalized substrate to base
plate interface) that are capable of
withstanding higher temperatures
but are low in cost.
nrel researchers are currently
working to characterize the thermal
performance and reliability of large-area bonded interfaces based on novel/emerging materials such as thermoplastics with embedded carbon fibers and sintered silver
materials. these large-area attachments represent the
bonding mechanism between the metalized substrate and
the base plate. thermal cycling tests of the bonded samples have demonstrated excellent reliability of the thermoplastic materials and have shown that sintered silver is
more reliable than solder (figure 10). the work will support future power electronics designs using Wbg devices
for higher temperature operation (>200 °c). Work is also
underway to develop predictive lifetime models that can
help in time-and-cost-effective design, thereby cutting
down on expensive and time-consuming experiments.

r. s. taylor. (2012). development, test and demonstration
of a cost-effective, compact, light-weight, and scalable high
temperature inverter for hevs, Phevs, and fcvs. [online].
u.s. department of energy vehicle technologies office,
advanced Power electronics and electric machines Program, 2012 annual Progress report 2012. available: http://
energy.gov/eere/vehicles/downloads/
vehicle-technologies-office-2012-advanced-power-electronics-and-electric
Y. sakai, h. ishiyama, and t. Kikuchi,
"Power control unit for high power
hybrid system," in Proc. SAE 2007 World
Congr., detroit, mi, apr. 16-19, 2007, sae
Paper 2007-01-0271.
K. bennion and J. cousineau, "sensitivity analysis of traction drive
machine cooling," in Proc. 2012 IEEE

WBG devices
can operate at
temperatures more
than double those
of conventional
silicon devices.

enabling Widespread Deployment of eDVs
the thermal management system is a critical component
of the etds. improved thermal management makes it possible to increase system power density, reliability, and efficiency while reducing cost. the push toward
high-temperature operation using Wbg devices and reducing rare-earth material in electric motors further emphasizes the need for cost-effective thermal management
strategies. only with innovations in this field will widespread market penetration of edvs become a reality.

For Further Reading
u.s. department of energy. (2012). President obama launches ev-everywhere challenge as part of energy department's
clean energy grand challenges. [online]. available: http://
energy.gov/articles/president-obama-launches-eveverywhere-challenge-part-energy-department-s-cleanenergy
usdrive. (2013, June). electrical and electronics technical team roadmap. [online]. mi: southfield. available:
www1.eere.energy.gov/vehiclesandfuels/pdfs/program/
eett_roadmap_june2013.pdf

Transportation Electrification Conf.
Exposition (ITEC), 2012, pp. 1-6.
r. W. Johnson, J. l. evans, P. Jacobsen, J. r. thompson, and
m. christopher, "the changing automotive environment:
high-temperature electronics," IEEE Trans. Electron. Packaging
Manuf., vol. 27, no. 3, pp. 164-176, July 2004.

Biographies
Gilberto Moreno (gilbert.moreno@nrel.gov) is an engineer at the
national renewable energy laboratory conducting research on
cooling technologies for power electronics and electric motors.
Previously, he was a mechanical engineer at lockheed martin.
Sreekant Narumanchi (sreekant.narumanchi@nrel.gov) is a
senior engineer and section supervisor of the advanced Power
electronics and electric motors (aPeem) team at the national
renewable energy laboratory. he leads r&d focused on
aPeem thermal management and reliability, and he has published more than 45 peer-reviewed papers and book chapters.
Kevin Bennion (kevin.bennion@nrel.gov) is a senior engineer at the national renewable energy laboratory (nrel),
conducting research on thermal management of power electronics and electric motors for advanced vehicles. he came
to nrel from ford motor company, where he worked on
electric-drive components and power electronics for hybrid
electric vehicles.
Scot Waye (scot.waye@nrel.gov) is an engineer at the
national renewable energy laboratory (nrel), focusing on
heat-transfer and fluid-dynamics problems using computational modeling and experimental methods. before joining
nrel, he conducted research involving wind loads on solar
energy systems, pollution dispersion, ventilation, indoor air
quality, energy efficiency, and turbine engine cooling.
Douglas DeVoto (doug.devoto@nrel.gov) is an engineer at
the national renewable energy laboratory, conducting r&d
on thermal stress analysis and reliability for vehicle power
electronics. Previously, he was a graduate researcher at the
university of maryland, where he evaluated power electronics in wind turbines.

IEEE Electrific ation Magazine / j une 2 0 1 4

http://http:// http://www.energy.gov/eere/vehicles/downloads/ http://http:// http://www.energy.gov/articles/president-obama-launches-ev http://www1.eere.energy.gov/vehiclesandfuels/pdfs/program/

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