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PCBD-May2016

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30 The PCB Design Magazine • May 2016 Dack: Great question and I can stick with the same met- aphor. Like my sister had the vision to see her garage roof quickly finished using an automated tool, I'd love to be able to slam out board designs using more automa- tion. But as my sister needed to pull out the compressor, order special nails, run the hoses and replace equipment before ever star- ing the job, the PCB design automation strategy for a particular job may not be worth the ef- fort. Just because we have automation tools we should not be obligated to use them unless they really improve the task at hand. Shaughnessy: In what areas of design do you usu- ally favor more automation? Dack: Repetitive processes and processes prone to human error. The CAM output routine is a simple example. The software I use allows me to set up a CAM output file routine and hit start. The two-layer, four-layer, and six-layer jobs I do usually have consistent stackups so pre-programmed routine works well. Unless it doesn't. But because my process is consistent it is easy to find where the process the error occurred. I find that output errors usually oc - cur with something inconsistent in the design; unique patterns of associated copper that must be switched on, etc. To facilitate automation I find myself striving to be more consistent in my design methodologies. Shaughnessy: For what tasks do you prefer having more manual control? Dack: Just to be clear, any preference for manual control is based on a deficiency or performance problem in automatic mode. Also, when I route. In fact, always while routing. Did I mention that I like manual control while I'm routing? Also, library part manipulation. I prefer the types of tools that allow the user to edit a part decal on a board interdependently of the library—without having to save it to the library. This allows for the odd times when the legend really needs to stand out or one land needs to be modified to adapt to a custom processing situation. Shaughnessy: In one survey we did, about 15% of designers said their EDA tools take away too much control. Do you understand their position? Dack: It would be interesting to see how those stats match up to percentage of designers laying out simple designs vs. complex designs. Work- ing recently with a busy PCB fabricator in Se- attle and a now a high-quality electronics con- tract manufacturer, I have seen quite a variety of designs that are very good but need minor manipulations to optimize them for manufac- turing. The edits should be able to be performed in a matter of minutes. But if the layout tool requires hand-shaking with the schematic in or- der to move forward without "breaking," well, the layout won't move forward until the sche- matic is in synch. Makes sense, except when the schematic responsibility and deliverables are owned by the EE or the part decal is owned by a component librarian and are required to be fully checked and approved before being passed to the designer for use. This has the potential to slow the prototype design cycle and time-to- market down considerably. Shaughnessy: How often do you use an autorout- er? If not, why not? Dack: Never! Are you surprised? This question has been asked of the design community for a long time. It is only the designers who are doing layouts with repetitive circuitry that will benefit from the time that it takes to set up the autorout- er's constraints. I recall using autorouters in the late '80s and early '90s when DIP style IC mem- ory boards were large and low speed. These were the golden years of the autorouting. The boards were consistent and very predictable. Today, I use the heck out of "dynamic" routers. Tools that allow the designer to interactively route a line or group of lines while steering the cursor in the preferred direction. Interactive modes will auto - matically push and shove and plow the selected lines adhering to set design rules constraints. If a problem arises, the DRC can be interactively manipulated to ease the constraint if required. DESIGN AUTOMATION TOOLS, TODAY AND IN THE FUTURE Kelly Dack

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