BoardSurfers: Going Beyond Just Correct - Improving and Optimizing Design and Routing

PCB layout editors provide many checks in the form of constraints and rules to ensure your design is correct. You even have the DFM rules to prevent fabrication or manufacturing issues. Then you have automatic routing to ensure an errorless board with the right connections and traces. But are you satisfied only with 'just a correct' board? Or, do you want to optimize it further? And what about 'quality' (Merriam Webster defines it as a degree of excellence)?  

I think that a little bit of tweaking - the final touches - is what makes something excellent compared to the mundane. We all cook, for instance, but the master chef puts that bit of extra something into the dishes that make us swoon. Why master chefs, we all have that aunt or uncle (or one or both of our parents) whom we remember for their culinary skills - the cakes that Uncle Freddy bakes or Aunt Martha's puddings. Most often, we ask them the recipe and try ourselves (or one of our cousins does) but cannot get the same taste or relish into it. I think that is excellence - they just don't add the exact ounces and pounds of sugar and flour or the right number of spoons of spices and salt, it is their last-minute touch - that pinch of cardamom or that sprig of sage or sometimes, just the garnish - the aroma, the colors. So it is with our printed circuit boards. The optimization of the board. Taking it beyond just 'correct'.

So, what do we do to be Uncle Freddy or Aunt Martha of the PCB electronics world? We can garnish and tweak our boards to add that flair - go beyond being just correct. We can improve design quality by identifying and fixing "optimizations" - issues beyond the scope of traditional DRCs. These are issues that can and do go unnoticed - may or may not be caught by post-layout software, like CAM (computer-aided manufacturing) systems.

Which brings us to the next question, how do you go about it? Uncle Freddy uses the toothpick test to check the consistency and doneness of his cakes and Aunt Martha tastes a spoonful of her pudding. You might be using your eyes, looking at the board in the canvas of the layout editor to detect physical geometries of routes or, maybe, you are using some complex DRCs. But that's not reliable and is tiresome. And, most important, you are never sure.

That's where Allegro layout editors make it easy for you with Route Vision. You can use Route Vision both during and after design to improve quality, manufacturibility, and performance of routing. The way the checks are performed and displayed is intuitive and visual - all cline segments that meet specified criteria (the checks you selected)  are highlighted till you are in Route Vision or till you have fixed the issues. You can, of course, decide to ignore the issues. Unlike DFM or DRC, Route Vision does not force you to fix all issues. Remember, you are optimizing and not correcting.

What all can you check in Route Vision? There are nine different checks in all. For example, you might want to spread out traces to reduce crosstalk and increase manufacturability. You have DRC spacing rules, of course, but you might want to go beyond those rules and identify traces with space less than a preferred value. For that, you have the Parallel Gap Less Than Preferred check.  Or, you might simply want to identify the 90-degree corners in your board using the 90 Degree Corners check. 

You can try the checks right away. Just choose View – Vision Manager and then select Route Vision in the Visions window. Click Configure to select the checks listed. Pointing to a check will tell you more about it. But if you are not satisfied with the description and want to know in-depth about each check try the Route Vision Rapid Action Kit (RAK) on Cadence Online Support. This RAK has two sample databases that you can use to run through the steps to specify the checks and view results.