Design Rules

PCB design is no longer a matter of placing tracks to create connections. High speed logic combined with smaller and more complex packaging technologies place new demands on the PCB Designer. It is not possible to satisfy all the requirements of the design by only considering the clearance between tracks, pads and vias. Designs today can also require that you apply specific requirements to individual nets, components or regions of the board as well as considering such issues as crosstalk, reflections and net lengths. Altium Designer's PCB Editor allows you to define design rules that monitor and test for these and other requirements.

Design rules collectively form an instruction set for the PCB Editor to follow. Each rule represents a requirement of your design and many of the rules, eg. clearance and width constraints, can be monitored as you work by the online Design Rule Checker (DRC). Certain rules are monitored when using additional features of the software, for example routing-based rules when using the Situs Autorouter to route a design, or signal integrity-based rules used by the Signal Integrity Analyzer when performing a detailed signal integrity analysis of a design.

Rule Categories

The PCB Editor provides a powerful interface from where you can define the various design rules as required. The rules themselves are divided into various categories - for more information on these categories and the types of rules therein, see:

With a well-defined set of design rules, you can successfully complete board designs with varying and often stringent design requirements. This is further enhanced by the fact that the PCB Editor allows you to export and import rule sets, enabling you to store and retrieve your favorite design rule configurations, depending on the job at hand.

Resolving Design Violations

DRC reports can appear quite daunting to the new PCB designer. The secret to keeping the process manageable is to develop a strategy. One strategy is to limit the number of violations that are reported. When setting up the report options in the Design Rule Checker dialog, set the Stop When Found feature to a small number. Another strategy is to run the DRC in a number of stages. If you find that the design contains a large number of violations, begin by enabling the rules one at a time. With experience you will develop a preferred approach to testing the various design rules.

Further Advice

To successfully complete a PCB design using Altium Designer's PCB Editor, the constraints of the design should be thought out and implemented as a well-honed set of design rules. Remember that the PCB Editor is rules-driven - taking the time to set up the rules at the outset of the design will enable you to effectively get on with the job of designing, safe in the knowledge that the rules system is working hard to ensure success.
Verify your scopes! Too often a myriad of violations will result from a poorly scoped design rule. Checking individual rule scopes and priority levels can save much wasted effort - and more importantly time - later on.
Also, check your design at regular stages - not just at the end of the design process and five minutes before the Fab House requires the artwork. Using a combination of the Online and Batch DRC tools periodically will help to keep any violations to a more manageable number.

Working with Rules

Read the following articles to learn more about working with design rules: