Net Class
What Is a Net Class in PCB Design?
A net class is a categorization mechanism in PCB design that groups nets with similar electrical requirements together, allowing engineers to define design rules once for the entire group rather than individually for each net. Common net class definitions include power nets (wider traces, larger clearances), high-speed signals (controlled impedance, specific clearance requirements), analog signals (isolated routing, guard traces), and general-purpose digital signals (standard width and clearance). Net classes simplify constraint management and ensure consistent rule application across all nets in a given category.
Net class assignments are typically defined during schematic capture or in the constraint manager of the EDA tool and are carried through to the layout environment via the netlist. When a designer routes a trace belonging to a specific net class, the EDA tool automatically enforces the associated width, clearance, and via rules. Well-defined net classes reduce the likelihood of design rule violations and make it easier for layout engineers — especially those who did not create the schematic — to understand and respect the designer's intent for each signal category.
Net Class-Aware Constraint Enforcement
Physics-driven AI layout tools consume net class definitions as part of their input constraint set, applying the correct trace width, spacing, impedance targets, and via rules for every net based on its assigned class. This automated enforcement ensures that the distinct electrical requirements of power delivery, high-speed signaling, and sensitive analog circuits are all respected throughout the generated layout without requiring the manual vigilance that traditional layout demands. When net class assignments change during design iteration, the AI engine can regenerate affected routing to comply with the updated rules.
