Thieving or Copper Thieving is a process of adding circular/square copper areas to large blank spaces on a layer to even out the copper distribution. The copper that is added is not connected to any nets on the board and should not affect the functionality.
Reasons to add copper thieving to a PCB:
- Even out the copper distribution across a layer
- Achieve consistent finished thickness of the PCB on all sides
- Minimize Bow and Twist
- Control dielectric thickness between layers
- Reduce cost due to excessive etching
Proper care should be taken to ensure that the copper thieving does not interfere with any impedance-controlled lines or RF-signal lines in the design. You can always provide fabrication notes to avoid copper thieving on certain areas of the design. Thieving can contribute to EMI problems. It would be much better for you to add copper pours and tie them to ground on the areas where thieving can cause problems.
The following options can be used while adding copper thieving on a PCB using Allegro PCB Editor:
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Cadence Design Systems