We commissioned a 'bad practice exemplar' by asking Plexus to modify a good design (provided by Valor) to demonstrate the most likely kinds of faults in each of the areas Design for Fabrication, Design for Assembly and Design for Test. The board is a 'fairly busy' real design, and is representative of a typical board of the 2000 vintage, so it deliberately does not operate at the state-of-the-art boundaries. It has been screened by the CAD system, so there are no gross errors, but the check was done against an minimal set of rules such as those that might be applied by an uninformed user, leaving a number of issues for you to spot.
Your task is to identify and evaluate the problems, and suggest ways in which they might be put right. In doing this you will have to apply the course material to this deliberately incorrect design, using the many sets of guidelines found in it and during your own research. Where necessary, you will need to create a solution that will be the 'least worst' compromise between competing objectives.
You will also have to meet the demands of your partners: preferences vary between different fabricators and assembly shops, which is why every company publishes these, often on their web site. To provide a level playing field for everyone, we have provided sets of model rules for both fabrication and assembly. However, you may well find from your own research that some aspects of these rules are unduly restrictive, and wish to suggest negotiation with (or even changing) your company's suppliers.
You first need to examine
- the Gerber files for the Bad practice exemplar
- our Model rules for fabrication and assembly
Compile a report summarising:
- your explanation of the areas of poor practice
- your suggestions for improving each of these three elements separately and the design as a whole
- your recommendations as to how the company should approach the design improvement task
- the other aspects of "design for excellence" that apply to this product.
You should assume that the members of your audience are designers, who have some knowledge of the basic processes but do not have detailed understanding of the manufacturing requirements.
As a guide, you are unlikely to include all the points we expect to find if your main report has fewer than 1,000 words..
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.