Inconsistent Bridging of Polygon Pours Near PAD - Need Help

[r_guptaK6E5R]

Hello AutoDesk Community,

I'm facing an issue where two polygon pours near a PAD sometimes bridge together, causing a short. The behavior isn't consistent—sometimes it works correctly with no bridging, but other times, the pours connect unexpectedly.

 I've attached the design files and included screenshots showing the behavior.

(Sometimes deleting Via's or Components fixes this issue, which does not make sense).

If anyone has encountered this before or has suggestions on how to resolve it, I would greatly appreciate your insights.

Thank you for your assistance!

Best regards,

Rituraj Das Gupta

[constantin.popescuXD3CL · Accepted solution]

Hi @r_guptaK6E5R Rituraj,

The reason for this erratic behaviour is the value assigned to the Thermal Width for you polygon pours. I have verified all 3 of them and you are using 254mil which is about 6.5mm. This value is 3 to 4 times bigger than your pads width / height and this is not correct (you would be better of just having the pads, vias direct connect to the copper pours). I am not sure how this value was put there but you need to keep in mind that the thermal width (spoke width) needs to be smaller than your pads smallest dimension otherwise this can always happen. I have changed the Thermal Width value to 24mil instead and there should be no issues anymore. This issue can happen when the thermal width is very big because the width of the thermal spoke becomes bigger than it's length and the spoke will potentially overflow the bounds of the pad, smd or via it connects to. Below is a snapshot with the copper pours after changing the Thermal Width:

In next update we have made some improvements that might aleviate this issue but you should still be mindful of the thermal width value and use a value that matches the pad, smd, vias you are using.

I hope this helps.

Please let me know if there is anything else I can help you with.

Kind Regards,

[r_guptaK6E5R]

Hi @constantin.popescuXD3CL ,

Thank you again for your help. You have nailed down the issue and your explanation makes the most sense. The software is not handling cases where thermal pad is larger than the pad size and have multiple pours as its neighbor. (Random Overflow issue).

The reason I initially set the Thermal Width to 254mil was to ensure that all the pads connected to the polygon pour would have the maximum possible thermal width. This was intended to optimize electrical connectivity while still providing some thermal relief for easier soldering, particularly for the inductor. This approach has worked well for me except for this case.

Given this goal, what would be the best approach to achieve the maximum thermal width for all the components using the software? Would you recommend adjusting the Thermal Width differently, or should I create separate polygon pours for each component to better control this?

I appreciate any further advice you can offer.

Best regards,
Rituraj

[jorge_garcia · Accepted solution]

Hello @r_guptaK6E5R,

If you need to very specifically control the thermal width then the easiest way to do that is to create a separate polygon for the components for which you want the larger thermal width.

With that said, a thermal width that large isn't providing much thermal relief. If you want try setting the thermal width to the smallest pad you are intending to connect to.

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

Best Regards,

[r_guptaK6E5R]

Thank you for the clarification and the support. I hope future updates improves/fixes this issue or at least flags an error.

Meantime I will use your suggestion as a workaround to minimize such occurrences.

Thank you again!

Kind Regards, 

Rituraj