PCB Design Rule Checks in OrCAD X

May 21, 2024

Cadence PCB Solutions

Key Takeaways

DRCs are crucial for validating PCB designs against set constraints like trace width and clearance, preventing manufacturing errors and enhancing reliability.
OrCAD X Presto PCB Editor provides instant feedback during routing, highlighting deviations from set rules and allowing for immediate correction.
The Constraint Manager in OrCAD X integrates seamlessly with both schematic and PCB layout stages.

DRC status is reported in the pie chart within the OrCAD X Presto PCB Editor properties panel.

PCB design rule checks are essential to validate whether your circuit board layout adheres to predefined constraints, such as trace width, clearances, hole sizes, and annular ring dimensions. It identifies design errors that could lead to manufacturing defects and affect the reliability of your board. A DRC enables you to verify that your schematic and layout accurately reflect the design margins you intended to adhere to. If any are violated, the DRC tool will notify you by flagging issues.

Common PCB Design Rule Check Types

The rules can be tailored to meet specific design needs. When you run a Design Rule Check (DRC), it identifies problems, but does not resolve them. As the designer, it is your responsibility to evaluate any discrepancies and determine whether adjustments are needed.

Design Rule Check Types
DRC Type	DRC Description
Ensure PDN Integrity	Validates stability of power and ground connections within PDNs.
Detect Electrical Errors	Identifies short circuits, open circuits, and unconnected pins.
Verify Net Connectivity	Ensures all nets are connected without floating pins.
Check Current-Carrying Capacity	Validates trace widths and copper pours for adequate current capacity.
EnsureSignal Integrity	Rules set within the constraint manager help constrain your design to avoid signal integrity issues like impedance violations.

Component Spacing	Components are placed at a minimum distance from the design outline and other components.
Pin and Via Spacing	Pins and vias have sufficient spacing to allow for the proper application of the solder mask.
Line Width	Line width must balance manufacturability and impedance control.
Fine Pitch Devices	Ensures sufficient space for connections with fine pitch devices within limited areas.
Via In Pad	Adjusts pad-to-pad connect value to properly place vias in pads for space maximization.
Blind/Buried/Micro Vias	Checks proximity of blind, buried, and micro vias, suggesting staggered vias or constraint adjustments.
Annular Ring Checks	Validates if the capture pad is large enough for laser drills; modifies design padstack if needed.
Floating Nodes	Circuit points without a definite voltage level due to lack of connection to a voltage reference.

OrCAD X PCB Design Rule Checks

OrCAD X allows for various constraint categories; including physical, electrical, spacing, manufacturing, rigid-flex designs, 3D clearances, and more. The constraints must be activated to be checked during PCB layout. DRCs are run to ensure that all set rules are adhered to during the design. Any violations or mismatches are flagged.

DRC violation highlighted and markedwhile routing

OrCAD X Presto PCB Layout DRCs

During routing, if constraints are assigned, any deviations from the set rules are highlighted. OrCAD X Presto PCB Editor provides real-time feedback on adherence to constraints and flags design rule violations. DRC errors can be viewed, filtered, and analyzed directly within the canvas. Errors are displayed in a pie chart, and you can navigate to specific errors for review and correction. After making adjustments, a refresh of the DRC is necessary to ensure all changes comply with the set rules. The system updates to reflect that all errors have been resolved, confirming the design’s compliance with the defined constraints.

You can double-click a DRC error in the search bar to immediately be brought to where it is in the layout

Setting up Physical Constraints in OrCAD X

The Constraint Manager is accessible in both the schematic and PCB layout environments, allowing for PCB design rules to be established within the schematic design.

How to Set Up Physical Constraints in OrCAD X
Step	Action	Details
1	Open Constraint Manager	Choose Tools → Constraint Manager. The Constraint Manager window opens.
2	Access Physical Constraints	Click "Physical" and choose the "All Layers" worksheet in the Physical Constraint Set folder.
3	Create a new Physical Constraint Set (CSet)	In the worksheet, select the default physical constraint set, right-click, and choose Create → Physical CSet.
4	Name the new CSet	Specify the name as "POWER_NET_CSET" and click OK.
5	Modify Constraints for Layers	Change the value of Min Line Width to 15 mil from 5 mil and Max Neck Length to 100 mil for both the TOP and BOTTOM layers.
6	Select Net Constraints	Select the "Net – All Layers" folder.
7	Apply Physical CSet to a Specific Net	In the All Layers worksheet, select the net "5V".
8	Set Referenced Physical CSet	Set the Referenced Physical CSet to "POWER_NET_CSET".
9	Apply Physical CSet to Other Nets	Similarly, select the nets "3V3" and "0" and set Referenced Physical CSet to "POWER_NET_CSET".
10	Close Constraint Manager	Select File → Close, or click X, to close Constraint Manager.

OrCAD X Constraint Manager

Elevate your PCB designs using PCB design rule checks in OrCAD X. Try OrCAD X today and harness the power of advanced tools to ensure your projects meet all necessary design requirements.

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