15 credits at level HE7
Designing for thermal issues was once only a concern for those whose products worked in extreme environments. However, modern circuits operate at ever-higher frequencies and dissipate an increasing amount of heat, whilst end-user pressures are demanding smaller enclosures. In consequence, most design and electronic packaging engineers now need to take thermal issues into account in order to ensure that their products will meet the required performance and reliability, and will not fail either functionally at temperature extremes, or prematurely during operation, simply because they have overheated.
This module places emphasis on understanding the fundamental issues of heat transfer that lie behind recommended good practice, and on modelling the thermal aspects of a design as a means of ensuring reliable operation at affordable cost. It explores the issues progressively, first at component level, then at board level and finally at system level, concentrating on the application of analysis methods and simulation tools and on generating practical solutions.
Who can benefit?
Electronic system and circuit designers, layout designers, production engineers, mechanical engineers, quality engineers, and managers of professionals in all these disciplines, who need a broad picture of the thermal aspects of electronic layout and equipment practice, whether as current practitioners or newcomers to this field. The module can be studied on its own or as part of a programme leading to a formal qualification.
The aim of the module is to introduce the impact made on product performance by the external thermal environment and the heat dissipated within the system, and to enable the student to appreciate how best to use thermal analysis and modelling tools to quantify and manage the thermal aspects of a design and thus enhance the performance and reliability of the product.
Thermal aspects of circuit function
The need for thermal management; trends in power dissipation; thermal design strategies.
Sources of heat: mechanisms of heat generation in conductors, semiconductors, electrolytic capacitor and through high-frequency losses; heat from the environment.
The effects of heat: changes in device characteristics with temperature and over life; causes and mechanisms of thermal and thermo-mechanical failure; reliability implications of over-temperature
Thermal modelling and simulation
Mechanisms of heat transfer: conduction (thermal diffusivity); convection (heat transfer coefficient); radiation (simple treatment of grey bodies).
Basis of modelling heat flow: thermal resistance; spreading resistance; the thermal circuit.
Thermal models: detailed/compact; limitations of two-resistor models; development of DELPHI models; testing and verification of models; transient and steady-state analysis; thermal time constants.
Modelling heat at the component level; component construction; building a detailed component model; enhancing component thermal performance.
Modelling heat at the board and system levels; modelling fluid flow and convection.
Use of simulation software; validating the simulation; interpreting the simulation in the light of end use; choice of software for purpose
Parameters and their variation: linear and non-linear behaviour; sensitivity analysis.
Thermal properties of materials and their measurement: methods; limitations; sources of inaccuracy. Thermal management materials.
Thermal vias and heat spreaders: thermal design; impact of materials. Heat sinks: thermal design; impact of materials; location and mounting. Heat exchangers; heat pipes.
Free and forced convection; practical implementation of fan-cooled systems.
The equipment environment: environmental severity; the climatogram; environmental testing. Enclosure design for the environment.
Verifying performance: thermal testing; soak testing and high temperature endurance; temperature cycling; power cycling.
The module is expected to involve 150 hours learning time spread over 12 weeks. All study and assessment is carried out via the internet so there is no requirement to attend in person. The approach is substantially student-centred, with tutor support by email and telephone on a one-to-one basis, although peer discussion is encouraged. Typically the generality of a concept is introduced in the online text and the student is then directed to a variety of information sources to research and analyse the subject area further, reflect and draw appropriate conclusions. On-line simulation, exercises and self-assessment questions (SAQs) throughout the module reinforce concepts and help students to monitor their progress and the effectiveness of their study.
when you have successfully completed this module you will:
to demonstrate that you have achieved the learning outcome you will:
|1.||be able to relate the functional and reliability performance of representative components and electronic products to their operating environment and the heat that is generated internally.||analyse and interpret the thermal and environmental factors that influence the function and reliability of representative components and completed electronic products.|
|2.||be able to make judgements on the most appropriate techniques and levels of modelling for evaluating the thermal performance of components on a board.||compare and contrast the results from different modelling techniques, and assess their accuracy, validity and applicability to general cases.|
|3.||be able to make judgements on the most appropriate techniques and methodology for optimising the thermal performance of an item of electronic equipment in an enclosure.||compare and contrast the results from different techniques and ways of approaching the task, and assess their accuracy, validity and applicability to general cases.|
|4.||be able to exercise good practice in thermal management techniques and enclosure design.||interpret the results of thermal performance estimates and simulations for a representative assembly and make appropriate design decisions that will accommodate both environmental influences and internally generated heat.|
Your achievement of the learning outcomes for this module will be tested as follows:
|Description||Apply a range of thermal modelling approaches to a specific populated board (including building up a detailed model of a component), and use appropriate underpinning theory to substantiate the practical findings.|
Evaluate different approaches for optimising the thermal performance of components and board, and report on the implications of these for reliability and overall product function.
|Use CFD tools to analyse an equipment assembly containing several boards in an enclosure, and devise an optimal heat management regime.|
Report on the modelling experience and on the thermal challenges of the boards/system, relating these to good practice.
There are no prerequisites for this module.
No restrictions apply.
Jamnia, Practical Guide to the Packaging of Electronics, Marcel Dekker, 2002, ISBN 0-8247-0865-2
Kordyban, Hot air rises and heat sinks: Everything you know about cooling electronics is wrong, ASME, 1998, ISBN 0-7918-0074-1
Kraus, Design and analysis of heat sinks, John Wiley & Sons, 1996, ISBN 0-4710-1755-8
Remsburg, Thermal Design of Electronic Equipment, Interpharm/CRC, 2000, ISBN 0-8493-0082-7
Sergent, Thermal Management Handbook for Electronic Assemblies, McGraw-Hill, 1998, ISBN 0-0702-6699-9
Steinberg, Cooling Techniques for Electronic Equipment 2nd edition, John Wiley & Sons, 1991, ISBN 0-471-52451-4
|Host Subject Group:||Computing & Electronic Technology|
|User Name||Date Accessed||Action|