Design Rule Check Using OrCAD X

Key Takeaways

• OrCAD X performs real-time and batch Design Rule Checks (DRC) to detect violations in trace widths, spacing, vias, and component placements before fabrication.

• Electrical Rule Checks (ERC) in OrCAD X identify connectivity issues like short circuits and floating nodes, ensuring electrical integrity alongside physical design compliance.

• OrCAD X provides visual DRC and ERC error identification with interactive debugging tools, allowing designers to efficiently resolve violations and optimize PCB layouts.

A Design Rule Check (DRC) is a critical verification process in printed circuit board (PCB) and integrated circuit (IC) design that ensures a layout complies with manufacturing and performance constraints. By analyzing key design parameters such as trace widths, clearances, via sizes, and component placements, DRC helps eliminate costly errors that could lead to defective products or manufacturing inefficiencies.

In OrCAD X, design rule checks can be performed at multiple stages of the PCB design process, including schematic capture and PCB layout. These rules include constraints on trace-to-trace spacing, minimum feature sizes, copper-to-board edge distances, and via tolerances. 

During the schematic capture phase, DRC ensures that the electrical design follows defined constraints and uses Electrical Rule Checks (ERC) to verify the electrical integrity of a design, reducing the risk of incorrect net connections or voltage mismatches. Once the layout is completed, physical DRC checks validate critical parameters such as trace width, spacing, and via configurations.

Advantages of Using OrCAD X for Design Rule Checks

Design Rule Check in OrCAD X

OrCAD X provides an extensive set of DRC capabilities to ensure that PCB layouts comply with manufacturing constraints and industry standards.

Design Rule Check Features in OrCAD X

OrCAD X offers both online and batch DRC, enabling real-time feedback during design as well as comprehensive error reporting for final verification. The tool includes the following interactive features:

Finding Design Rule Check Errors in OrCAD X

OrCAD X Presto PCB Editor will give you an indication of your design’s DRC status within the properties panel. The DRC errors can be found by clicking on the hyperlink, while an overview of the errors and their types are presented in the pie chart. If you click on a section of the chart, it will then focus on the errors of the given type:

Spacing Errors

Spacing errors occur when traces or other design elements are placed too close together, violating predefined spacing constraints. By selecting the spacing portion of the pie chart, the search panel will automatically open to display all detected spacing errors. Users can further refine the view by selecting specific types of spacing violations. For example:

• Line to Line Violations: These errors indicate that traces are placed too close to each other, failing to meet the required spacing constraints. To fix them, users can enter Slide Mode, attach a trace to the cursor, and reposition it to increase spacing. The system will highlight any remaining violations with a red DRC marker. Once adjustments are complete and constraints are satisfied, the error is removed from the search panel.

Physical Errors

Physical errors are related to constraints on individual trace dimensions and their layout properties. Upon selecting Physical in the DRC pie chart, the system updates to show specific types of physical violations. A common example is:

• Minimum Neck Width Violations: These occur when a trace becomes too narrow at a particular point, violating the minimum width constraint. To correct this, users can select the affected trace in the PCB canvas and adjust its width in the Properties Panel (e.g., increasing it to 15 mils). Once the trace width meets the required specification, the violation is resolved, and the error is removed from the search panel.

Electrical Errors

Electrical errors involve violations of signal integrity and differential pair constraints. Selecting Electrical in the DRC pie chart reveals sub-categories such as:

• Differential Pair Maximum Uncoupled Length: This error occurs when the separation between traces in a differential pair exceeds the allowed length, which can degrade signal integrity. Users can filter the search panel to locate these violations and correct them by adjusting the traces to bring them closer together.

• Differential Pair Phase Tolerance Violations: These errors indicate that the length of differential pair traces is mismatched beyond the allowed phase tolerance. To fix this, users need to adjust the trace routing to ensure both traces are of equal length. Filtering options in the search panel allow users to isolate and address this specific violation efficiently.

Ensure your PCB layout meets manufacturing and performance standards with a design rule check in OrCAD X. By leveraging the powerful DRC and ERC tools, designers can detect and correct violations in trace widths, spacing, and electrical integrity before fabrication. Explore how OrCAD X and Cadence’s PCB Design and Analysis Software can help streamline your design process and improve product reliability.