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PCB clearance rules refer to the minimum spacing requirements between different elements on a PCB to ensure correct operation and avoid electrical problems such as short circuits, arcing, and electromagnetic interference. They are one of the critical aspects of PCB design.

These rules apply to different elements of the PCB:

Trace to Trace

The distance between adjacent traces is a crucial consideration to prevent short circuits and crosstalk. It will depend on factors such as the maximum operating voltage and the PCB's environment.

Trace to Pad

Traces must have a safe distance from pads not connected to them to prevent accidental bridging and short circuits during soldering.

Pad to Pad

Pads for different connections must be spaced apart appropriately to ensure that components can be soldered without causing shorts.

Via to Via, Trace, or Pad

Vias should be placed at a sufficient distance from each other and from traces and pads. The spacing helps avoid problems during the drilling process and helps prevent short circuits.

Component to Component

Components need to be placed at an adequate distance from each other to allow for thermal expansion, avoid mechanical interference, and prevent electrical interference.

Edge Clearance

Components, traces, and vias should be placed a safe distance from the edge of the PCB to avoid damage during fabrication and handling.

The specific clearance requirements can depend on several factors, including the maximum voltage that the PCB will handle, the type of signals (digital or analog), the frequency of operation, and safety regulations. The manufacturing process's limitations also play a role: different manufacturers may have different capabilities in terms of how closely they can reliably fabricate different elements.

 

Always consult your PCB manufacturer's design rules and any relevant safety standards or regulations to ensure your PCB design meets all the necessary requirements. It's better to be safe and design with more significant clearances when possible. However, in compact designs, you might have to balance between minimum clearance requirements and the available space.