IEEE Electrification Magazine - June 2014 - 48

Terminal
Wire/Ribbon
Bonds

Enclosure
Device
Encapsulant

Die Attach
Substrate
Attach

Acoustic Microscope Image of
Thermoplastic Bonded
Interface with No Defects

Metalized Substrate
Base Plate
(a)

Image of Sintered Silver
Bonded Interface with Edge
Fracture Defect
(b)
Figure 10. (a) A schematic of a typical power module package showing metalized substrate to base plate interface and (b) scanning acoustic
microscopy images of the thermoplastic and sintered silver-bonded interfaces after thermal cycling. The dark regions indicate good bonding,
while the white regions indicate air gaps, fracture defects, or delaminations.

between cooling performance and the internal heat
spreading performance within the motor. if the effective
thermal conductivities within the motor improve, then
fluid cooling performance improvements have a larger
impact on overall heat removal.
the heat generated within the
motor is typically dissipated by either
a Weg cooling jacket pressed against
the stator case or atf jets impinged
onto the end windings or rotor. the
use of atf fluid as a coolant is practical because atf fluid is a dielectric and
because, in some cases, the electric
motors are housed within the vehicle's
transaxle, where atf fluid is readily
available. although this cooling method is common, currently there is minimal publicly available information
regarding the jet impingement performance of atf fluids.
nrel has experimentally measured the heat transfer coefficients for impinging atf
jets at various fluid temperatures and jet velocities. an
image of an atf jet impinging on a heated surface is
shown in figure 9. fluid temperatures were varied from

50  to 90  °c to encompass potential operating temperatures within an automotive transaxle environment. tests
were conducted to simulate atf jets cooling motor endwindings by using test samples with wire-bundlelike features. the results show that heat
transfer coefficients increase with
increasing jet velocity except at higher velocities and higher fluid temperatures when fluid splatter, on the
wire-bundlelike samples can degrade
thermal performance. in addition to
motor cooling applications, these
results may also be applicable to
potential atf cooling strategies for
automotive power electronics components to support situations where
the power electronics are integrated
with the electric motor.

Improved thermal
management makes
it possible to
increase system
power density,
reliability, and
efficiency while
reducing cost.

48

I E E E E l e c t r i f i c ati o n M agaz ine / j un e 2014

ensuring eDV Reliability
in addition to a competitive cost, an
assurance of reliability is essential to increase edv market
penetration. today's vehicles are expected to have a
15-year reliable operating lifetime. conditions of temperature extremes (-40 to 140  °c ambient underhood



Table of Contents for the Digital Edition of IEEE Electrification Magazine - June 2014

IEEE Electrification Magazine - June 2014 - Cover1
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IEEE Electrification Magazine - June 2014 - Cover3
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https://www.nxtbook.com/nxtbooks/pes/electrification_december2022
https://www.nxtbook.com/nxtbooks/pes/electrification_september2022
https://www.nxtbook.com/nxtbooks/pes/electrification_june2022
https://www.nxtbook.com/nxtbooks/pes/electrification_march2022
https://www.nxtbook.com/nxtbooks/pes/electrification_december2021
https://www.nxtbook.com/nxtbooks/pes/electrification_september2021
https://www.nxtbook.com/nxtbooks/pes/electrification_june2021
https://www.nxtbook.com/nxtbooks/pes/electrification_march2021
https://www.nxtbook.com/nxtbooks/pes/electrification_december2020
https://www.nxtbook.com/nxtbooks/pes/electrification_september2020
https://www.nxtbook.com/nxtbooks/pes/electrification_june2020
https://www.nxtbook.com/nxtbooks/pes/electrification_march2020
https://www.nxtbook.com/nxtbooks/pes/electrification_december2019
https://www.nxtbook.com/nxtbooks/pes/electrification_september2019
https://www.nxtbook.com/nxtbooks/pes/electrification_june2019
https://www.nxtbook.com/nxtbooks/pes/electrification_march2019
https://www.nxtbook.com/nxtbooks/pes/electrification_december2018
https://www.nxtbook.com/nxtbooks/pes/electrification_september2018
https://www.nxtbook.com/nxtbooks/pes/electrification_june2018
https://www.nxtbook.com/nxtbooks/pes/electrification_december2017
https://www.nxtbook.com/nxtbooks/pes/electrification_september2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2018
https://www.nxtbook.com/nxtbooks/pes/electrification_june2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2017
https://www.nxtbook.com/nxtbooks/pes/electrification_june2016
https://www.nxtbook.com/nxtbooks/pes/electrification_december2016
https://www.nxtbook.com/nxtbooks/pes/electrification_september2016
https://www.nxtbook.com/nxtbooks/pes/electrification_december2015
https://www.nxtbook.com/nxtbooks/pes/electrification_march2016
https://www.nxtbook.com/nxtbooks/pes/electrification_march2015
https://www.nxtbook.com/nxtbooks/pes/electrification_june2015
https://www.nxtbook.com/nxtbooks/pes/electrification_september2015
https://www.nxtbook.com/nxtbooks/pes/electrification_march2014
https://www.nxtbook.com/nxtbooks/pes/electrification_june2014
https://www.nxtbook.com/nxtbooks/pes/electrification_september2014
https://www.nxtbook.com/nxtbooks/pes/electrification_december2014
https://www.nxtbook.com/nxtbooks/pes/electrification_december2013
https://www.nxtbook.com/nxtbooks/pes/electrification_september2013
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