|Covers|| Learning outcomes 1 & 2
|Notional workload||25 hours|
|Comments||For information on submitting assignments, please refer to the AMI home page under Students, Assignments|
|Submission date||Midnight at the end of study week 8
Please refer to the module planning chart for the date
As described in the Module Descriptor, this module is assessed by two assignments, the first of which focuses at the component/board level; the second assignment will extend your use of simulation to evaluating an enclosure with multiple boards.
As part of this first assignment, you are asked:
To supplement your report on this work, we will be looking both for a critical evaluation of the different approaches used, and for an analysis of how the thermal characteristics of the original design might be expected to affect the reliability and overall function of the product.
An organisation sub-contracted to CISCO systems has developed a new fibre-optic/copper router, part of which is a 12-layer PCB assembly. As head of the thermal analysis team for this organisation, you are required to undertake an evaluation of this assembly in order to:
This link describes the thermal environment for the router PCB assembly and the components used, including a preliminary layout for the assembly.
The elements of the task are:
The first five of these need to be tackled in sequence, elements 6 and 7 can be tackled in either order, and you are recommended to start work on element 8 before completing the simulations.
Throughout the task, don’t forget to apply common sense! Is your result within the limits of what you might expect? This is especially true in element 1, where we expect a reasoned engineering estimate based on your knowledge of the thermal environment and your study of the module, and some explanation of (or at least comment on) any unexpected results.
For element 2 of the task, we are expecting you to try to refine your estimates by building more detailed spreadsheet models. For example, the 144-lead device that in element 1 would be modelled as just one or two thermal resistances, in element 2 might be modelled by calculating appropriate values for the more detailed set of interfaces indicated by Figure 1.
For element 7 of the task, you will find that FLO/PCB does not support transient analysis (for which you would need to use FLOTHERM). However, simple calculation based on the thermal mass of the assembly and the heat input will scope the thermal time constants of the board and give you sufficient information on which to base your comments in the second part of element 8.
In element 8, we expect you to demonstrate some understanding of failure rate issues as they affect the whole range of likely components (not just semiconductors), under both steady state and power-cycling conditions.
Your submission should be a report to the design management team within your organisation covering the following elements:
You can assume that the members of your audience are aware of the components used and of the functional features of the design, but have only a partial understanding of thermal matters.
As a guide, you are unlikely to include all the points we expect to find if your main report has fewer than 2,000 words. There is no maximum word count as such, but excessive length may be penalised.
In order to keep your script concise and well-argued, and its structure clear, you may find it helpful to provide relevant supporting material in appendices to the main report. This applies particularly to detailed calculations and information collected during the analysis and simulation elements of the task.
As always, you are strongly recommended to re-examine your draft report and conclusions to check that you have covered all the elements required in the report.
The maximum marks available for each element of the report are as shown in the table below:
|Modelling the assembly using a range of approaches||
|Critical evaluation of modelling approaches||
|Optimising thermal performance||
|Analysis and recommendations concerning moving the power supply||
|Analysis of reliability and performance impact of thermal characteristics||
|Analysis of reliability and performance impact of duty cycle reduction||
|Quality of presentation (including introduction and conclusions)||
For information on grades, please refer to the AMI home page under Students, Assignments, Marks and Grades.