I’m designing a breakout board for a 400MHz RF tuner using a PCB mill that doesn’t remove excess copper during etching. I’ve planned to allocate the ground plane on the top layer and the traces on the bottom layer. The traces will be enclosed by excess copper resulting from the milling process but not part of the circuit. Would it be advisable to connect this top ground plane (leftover copper) to the bottom ground plane to aid in noise reduction? Or could having ground planes on both the top and bottom layers pose any issues?
Connecting the leftover copper from the top GND plane to the bottom GND can sure help in noise reduction as it provides additional shielding and a low-impedance return path. Stitching vias can help create a continuous GND plane and minimize signal interference.
However it’s essential to consider potential issues that may arise from having GND planes on both top and bottom. One concern is the possibility of creating unintended signal paths or coupling between different portions of the circuit due to the close proximity of the GND planes. This could lead to signal distortion or interference.
I would carefully plan the placement of stitching vias to ensure they create a uniform GND plane without introducing unintended signal paths. Additionally, consider using vias with smaller diameters and strategic placement to minimize any adverse effects on SI.
Hope that helps!
2 Likes
I would certainly make sure the ground planes are connected. Perhaps more important are the questions related to using the mill. Can you reliably get 50 ohm traces cut (I’m assuming the tuner is a 50 ohm device), and will enough clearance be created to be sure the ground areas don’t “load” the signal traces?
2 Likes
Thank you both for the replies.
Certainly, ensure they’re connected. It’s crucial to avoid leaving any unconnected copper, as it could inadvertently create a patch antenna. Additionally, note that grounding copper on the trace layer might slightly reduce the trace impedance.
For optimal performance at 400 MHz, incorporate numerous stitch vias to ensure that any copper islands on the trace layer are effectively grounded to the plane with minimal impedance. If there are any islands that cannot be connected to the main ground plane through vias, consider milling them out entirely or removing them manually with appropriate hand tools.
1 Like