Have you ever been all the way to the end of a pcb layout and realized that you forgot to setup and run the Design Rule Check (DRC) on your board? If this situation has happened to you then you have likely been greeted with a board that looks like this:
DRC issues everywhere! This is the point where you ask yourself, “why did I not set up and run the DRC earlier?”
When laying out a PCB, each item (components, holes, traces, vias) will have to adhere to a set of design requirements in order to prevent issues with the performance of the circuit and issues during manufacturing. Even simple layouts with a low part count can have a significant number of these requirements. Managing all the trace width, clearance, power, and drill rules in your head can quickly become a daunting task as the complexity of your designs increase. This is where the DRC steps in to actively handle and check all these rules as the PCB is routed. (Note: see our PCB trace width calculator for additional help.)
The DRC acts as a moderator, constantly checking your design for issues as you lay out your PCB. It will automatically review the decisions made by the designer and flag any issues. Identifying and fixing issues during the layout process instead of after the board is complete can save a lot of time (and headaches).
For any new PCB design, configuring the DRC should be the first step before any traces are laid down. Fortunately, configuring the DRC is simple and only takes a few minutes to setup. The image below shows an example of the DRC window in Diptrace:
In this window all of the design requirements are defined. MacroFab has a list of values to use for general PCB design at Assembly Capabilities. The design rule information on this link shows typical minimum values used for PCB design. These values will be sufficient for most layouts unless fine pitch parts (such as BGA chips) are used or the board has high voltage/power requirements.
The benefits of configuring the DRC are actually two-fold. First, the rules prevent electrical design issues resulting in compromised performance and second, they prevent added cost to manufacture the boards.
The design rules on the MacroFab help pages represent the minimum requirements for our standard PCBs. Deviating from these values is allowed, but will result in higher PCB costs. In general, it is best to design a board with these values.
Considering the DRC as a useful tool instead of a nuisance and configuring it before laying out your PCB are good habits to develop. Regardless of the complexity of the board, the DRC can prevent annoying (and potentially costly) issues from creeping into your design.
If the DRC is properly configured and all rules are followed, instead of a list of errors you will be greeted with the following image.