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Finishing the Autorouter disconnects patches of polygon signal

Message 1 of 4
153 Views, 3 Replies

Finishing the Autorouter disconnects patches of polygon signal



I encountered a problem where I want to use the autorouter but it partly destroys the design. This only happened today after working in the past.


It happened after I created a polygon from the board outline to create a big GND layer. Then I used the Autorouter to trace the components. It finishes and all still looks fine (1st picture). But after clicking "End Job" it removes patches of the polygon/GND layer and displays an info which now says "(only) 97.2 % finished. Polygons may have become signal disconnected".


I didn't find a solution online or in this forum so any help is greatly appreciated.





Kind regards



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Message 2 of 4
in reply to: m_eckhard

Hi @m_eckhard,


So this is the nature of the beast in this case. You're fortunate you haven't run into this before but it was something that was an eventuality. When the autorouter runs it doesn't worry about the polygons since they can be recalculated at the end. Since the autorouter is just trying to get things connected there is a good chance that it will cut the polygons up and leave islands. At the end when the routing is done the polygons get recalculated and that's when islands can form. There is no way to control this.


What you would generally do is fix it by either connecting the islands using vias and manual traces or manually rerouting portions of the design so that the islands get resolved.


Let me know if there's anything else I can do for you.


Best Regards,

Jorge Garcia
​Product Support Specialist for Fusion 360 and EAGLE

Kudos are much appreciated if the information I have shared is helpful to you and/or others.

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Message 3 of 4
in reply to: jorge_garcia2

Hi @jorge.garcia,

thank you very much for your quick reply and clarification!

Kind regards
Message 4 of 4


I wonder if there is any work being done in the Autorouter code to make it possible to automatically reconnect polygon islands. We see the polygons getting chewed up a lot, and it ends up generating 10, 20 and even 30+ airwires sometimes. Certainly, it can calculate the airwires, so it should be able to see ways to connect, since that is what the Autorouter is all about, right?

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