topic Re: Feature Request: Layer-Specific Custom PCB Rules for Differential Pairs in Fusion Electronics Forum

Feature Request: Layer-Specific Custom PCB Rules for Differential Pairs

paullevene — Mon, 18 Aug 2025 17:50:29 GMT

Currently in Fusion 360, when creating Custom PCB Rules, there is no way to assign a rule to a specific layer. This becomes a limitation in real-world PCB design scenarios.

Example use case:
When routing a differential pair, the required isolation between the pair signals depends on the stack-up and the nearest reference plane.

On the top layer, the pair may require one spacing to achieve the correct impedance.
On an internal layer, the same signals may need a completely different spacing to achieve the same impedance, due to the different dielectric thickness and reference plane proximity.

Because of this, a single global rule is insufficient. The correct design practice is to vary gap widths and track sizes per layer, but Fusion currently doesn’t allow this level of rule assignment.

Feature request:

Add the ability to assign rules to specific layers (or groups of layers).
Provide an easy way to define differential pair rules (track width and spacing) that are layer-dependent, so impedance-controlled routing can be set up correctly without manual overrides.

This would make Fusion’s PCB tool more robust for high-speed and impedance-controlled design, and reduce the chance of errors during routing.

Re: Feature Request: Layer-Specific Custom PCB Rules for Differential Pairs

jorge_garcia — Wed, 27 Aug 2025 11:57:52 GMT

Hi @paullevene ,

I hope you're doing well. This is in fact possible already see the image below, the key is to scope it properly.

The clearance rules can also be scoped to the specific layer.

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

Best Regards,

Re: Feature Request: Layer-Specific Custom PCB Rules for Differential Pairs

paullevene — Mon, 01 Sep 2025 16:47:18 GMT

Hi @jorge_garcia,

Ah I think the issue I faced is that you can't tell that the selection box is in fact scrollable - the scrollbars are hidden. Normally for this type of interface the whole menu should open if there is enough space of the screen to display - why is there a scroll box and why are the scrollbars hidden? See image attached.

Re: Feature Request: Layer-Specific Custom PCB Rules for Differential Pairs

jorge_garcia — Tue, 02 Sep 2025 21:10:35 GMT

Hello @paullevene ,

I hope you're doing well. That is a valid point, I'll share it with our XD team so that they can address it.

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

Best Regards,