3-D thermal modelling of power device packaging
Swan, I. R. (Ian R.) (2010) 3-D thermal modelling of power device packaging. PhD thesis, University of Warwick.
WRAP_THESIS_Swan_2010.pdf - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Official URL: http://webcat.warwick.ac.uk/record=b2491721~S15
Power converters enable e±cient conversion of electric power, thereby reducing power
consumption and cost. The key enabling technologies inside power converters, typically
used in hybrid electric vehicles, are the semiconductor devices. Device reliability is of high
priority because they generate heat from the dissipation of electric power which can lead
to failure if the device maximum junction temperature is exceeded. Furthermore, device
temperatures can vary largely in switching applications, leading to thermal-mechanical
fatigue failure. As electronic designers are pushed to deliver smaller and more powerful
packages, they are finding thermal issues increasingly di±cult to solve. The primary goal
of this thesis is to develop a fast and accurate thermal simulation design tool which is
capable of simulating realistic power converter operation.
Most commercial thermal simulators use finite-element software. Despite their perceived accuracy, they suffer from severe computational requirements and offer limited
ability to explore power converter packaging converter designs during realistic converter
operation. Traditional approaches using R-C networks as thermal equivalent circuits are
of little use as a design tool since for every geometrical layout of the packaging structure which is tested, the designer must return to the starting point which is either a
time-consuming FE simulation or a practical experiment.
The Fourier thermal model presented in this thesis is a purely conductive model requiring no parameter extraction or use of a FE simulator. The starting point for the Fourier
model is the heat equation. The Fourier thermal model yields solutions to the heat
equation by carrying out spatial discretisation using a truncated Fourier series and using
MATLAB/Simulink to perform temporal discretisation using a dynamic ODE solver.
Validation using the finite volume thermal simulator FLOTHERM showed that the
transient Fourier model could accurately simulate 3-D heat conduction through a wide
range of power converter packaging structures. The Fourier thermal model is an excellent
early stage design tool because its simulation speed is far superior to FLOTHERM, even
though both models operate with a similar accuracy.
The use of MATLAB/Simulink as the simulation environment enabled the Fourier
thermal model to operate within the framework of an electro-thermal simulator and therefore simulate realistic load conditions. This is major advantage over existing approaches
which fail to simulate electro-thermal interaction. Experimental validation of the fast
electro-thermal converter simulator was achieved by utilising an inverter back-to-back rig
and recording transient device temperatures using an infrared camera. The similarity
between the experimental and simulated results indicated that the Fourier thermal model
was sufficiently accurate. The electro-thermal simulator operated at a simulation speed
which was ten times real time, which is extremely fast compared to existing approaches
which can take up to two days to simulate a 60 second drive cycle. 'Ten times real time'
represents a significant step forward for power converter packaging design.
In the future device reliability can be accurately predicted if the electro-thermal simulator model is combined with a reliability model. The potential of the Fourier thermal
model to aid numerical optimisation of the whole power converter is exciting.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||T Technology > TK Electrical engineering. Electronics Nuclear engineering|
|Library of Congress Subject Headings (LCSH):||Electric current converters -- Computer simulation, Electric current converters -- Thermal properties, Heat -- Conduction -- Computer simulation, Heat -- Conduction -- Mathematical models|
|Official Date:||September 2010|
|Institution:||University of Warwick|
|Theses Department:||School of Engineering|
|Extent:||xxi, 245 leaves : ill., charts|
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