Thermals short polygons when thermal width is at least double the polygon width, no DRC error detected.

[Anonymous]

In this board, the VCC polygon (rank 2) on the right is nested within the PGND polygon (rank 6, width 6, thermal width 6). Everything is OK and there are no DRC errors. The Pad that I am concerned with is the big VCC pad, in the middle of both polygons. 

However, once I increase the thermal width to 12, the thermal shorts out both polygons. No DRC error is raised and re-filling the polygons has no effect. 

Changing the polygon width to 12, to match the thermal width, resolves the problem. 

If, now the thermal width is increased to 16, there is no issue. But when it is increased to 24, the same issue occurs: 

Unfortunately, I only discovered this after manufacturing my board, and wondering why there was a short between power and ground. Not looking forward to the hours of rework 😞 Looking forward to the issue being fixed though 🙂

Details: 

2.0.10806
Active Plan: Fusion 360, Student
Windows 10 (19043)

[Anonymous]

This is quite a serious bug as it can cause manufactured PCB boards to be unusable! Hope it gets fixed soon

[edwin.robledo]

Hi vicgdmQVSSJ,
Thank you for the detailed post, we have shared it with our team of developers and they are looking into it. 

Thanks again!

Ed 

[panpan_fan]

Hi @Anonymous 

I hope you are doing well!

The polygon issue has been fixed in Fusion 360 V2.0.11183+.

Please have a try, thanks!

Regards,

Panpan Fan