This is one of the stranger bugs I’ve encountered, if it is a bug. I have completed my first design in V5.0.1. It is a microwave board; single sided with an unbroken ground plane on the back. I am using a co-planar format, which means the top is mostly ground plane as well. It’s finished and looks good, but one part has programming pins on the bottom, so the ground plane must be relieved under it. Following the docs, I right-click on the border (zone limit), select Add Cutout Area, and draw the cutout. I always have problems when closing a zone. A double-click will close the zone, but the cursor still is attached and wants to continue drawing. I’ve found that a second double click will release the cursor, and a B will fill the zone. The cutout area is as I drew it. Works fine - but…
I discovered that the overall zones on the entire board, both sides, have relieved back from the edge by .016". Why is it doing this? There is nothing in DRC that uses that .016 dimension. It’s a mystery. If this was a multilayer board, I would draw the zone relieved from the edge, but on this board, I want it right to the edge, and it was fine that way until I drew the cutout. Any ideas?
The clearance from the outline of the board is the same clearance as between the zone and other nets.
Click on a zone boundary to select it / "E"dit / Settings: Clearance.
Just set it (temporarily) to something big (like 1mm) and see what happens.
Distance from the edge is governed by two things:
- Zone clearance
- Width of the Edge.Cuts line
So, if you want your zone right to the edge, you can set your zone clearance to 0 and your Edge.Cuts width to a similarly small (but non-zero in this case) number. Note that this will affect the clearance to other elements in your design, so you’ll need to adjust their spacing if you depended on the zone clearance for minimum spacing.
I think I have it figured out. This board is part of an overall larger board. We wanted to get it into test before the rest of the board is finished. I had defined the size of shielding I wanted to use and placed parts and wiring within that area. The overall board outline was drawn with EdgeCuts. I moved the entire circuit as a block outside the outline and worked on it independently. I did not have an EdgeCuts bounding box around it. Thus, my overall zones on both sides went right to the dimensions I had used to draw it. The overall spacing used on the board is defined by the specifications of co-planar waveguide for the specific substrate I am using. After I finished the overall design, I drew an EdgeCuts box around it. The zones still formed right up to the edge, so apparently it pays attention to the order in which things are drawn. But when I added the internal cutout, somehow it reverted to the design rules and relieved the zone from the edge, by 16 mils. I had no idea that the line thickness used to draw the EdgeCuts layer was taken into account. My internal global spacing is `13 mils, and the border was drawn with 6 mils, so half of that added to the 13 is 16 mils. That explains that part.
The answer is to delete the EdgeCuts border; then draw my cutout. The zone no longer shrinks when filled. If I now draw a new border on EdgeCuts, it will again shrink - but I can see no reason to do the outline on that layer. I drew one on the Dwgs.User layer, and the zone no longer shrinks. Problem solved!
Thanks for the suggestions.
You might need to communicate this intent to your boardhouse. I think they usually expect only substrate on the edge cuts and exposed copper can cause problems with routing the margin as they use a different milling bit/speed - small features can get damaged. A big plane is probably ok.
John, thanks for the reminder. I know that, but this is a somewhat different situation due to the need of soldering the shield. I can slightly increase the size of the substrate enough to keep the fab shop happy. Still tweaking this thing.
This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.