Design Rule Check Demystified

Missing pins, power ground shorts, and misaligned vias—there’s nothing worse than having to scrap product on the production line due to a simple error that should have been caught early in the design phase.

Modern PCB design is like putting together a complex 3D puzzle, and when you have to manage thousands of components and connections across a multi-layer board, mistakes are bound to occur.

Fortunately there is something really simple you can do early in the PCB design process that can ensure manufacturability before you send your designs to the fabrication house: perform a design rule check (DRC).

What follows is a crash course on DRC, and how it can help you improve your acceptable manufacturing yield.

What is a Design Rule Check?

A design rule check (DRC) is simply a set of rules a designer can use to ensure their schematic matches all the dimensional tolerances and manufacturing considerations they set for a board.

Variation is a natural part of any production process. A fabrication house’s ability to control process variation is directly tied to the quality of your product. It’s important to account for these natural variations in production by adding enough margin to your design to ensure you are receiving an acceptable yield of functioning parts.

A DRC lets you verify that your schematic and layout in fact reflects the design margins you wished to incorporate in your design. When one of these design margins is violated, the DRC tool will let you know by flagging the missing pin number, miswire, short or other error on your schematic or layout.

For example, Cadence’s OrCAD gives you the ability to perform a DRC as early in the design process as schematic capture:

During the layout stage, DRCs will also check physical parameters such as:

• Trace width and spacing

• Via size and spacing

• Drill to board aspect ratio

• Outline to all pin pads

Beyond DRC

DRC only checks the validity of your initial schematic, and whether it can be manufactured with a good yield. Electrical Rule Checks (ERC) are used at both the schematic and layout levels to ensure the device satisfies electronic design rules such as floating devices, nets, and pins, power domain crossing, and maximum allowed series pass gates.

Conclusion

Incorporating DRC into your EDA process can prevent issues during production, saving you time and money. We’ve only scratched the surface of the types of checks you can run to ensure manufacturability of your design before it hits the assembly lines. Fortunately, modern PCB design software walks you through many of the checks you can run on your designs. Check out Cadence’s suite of PCB design and analysis tools today.