AR0111 Specifying the PCB Design Rules and Resolving Violations

Specifying the PCB Design
Rules and Resolving Violations
Summary
Article
AR0111 (v1.1) April 26, 2005
This article introduces the PCB Design Rules System, in
particular how rules are created and applied to objects in a
design. It also describes how defined rules are checked
using online or batch DRC tools and discusses navigating
and resolving violations.


PCB design is no longer a matter of simply placing tracks to create connections. In fact, many complex
designs can be a minefield of conflicting requirements. High speed logic combined with smaller and
more complex packaging technologies place extreme 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 net impedance, crosstalk,
signal reflections and path lengths. Altium Designer's rules-driven 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, for example 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 routing a design –
either interactively or using the Situs Autorouter – or signal integrity-based rules used by the Signal
Integrity Analyzer when performing a detailed signal integrity analysis of a design.
Armed with a well-defined set of design rules and the PCB Editor’s variety of features for checking and
interrogating violations of these rules, you can successfully complete board designs with varying and
often stringent design requirements.
The PCB Rules System – Fundamentals
The rules system built-in to Altium Designer’s PCB Editor has several fundamental features that set it
apart from most other design rule systems employed by other PCB editing environments:
? Rules are separate from the objects – the defined design rules are separate from the design
objects to which they are applied. A rule is not added as an attribute of a design object, but is rather
added to the overall rule set and then scoped to apply to that obje ct. In this way, rules can be
applied to multiple design objects, modified, or applied to different objects. This would otherwise
prove very cumbersome to do if having to change rule attributes of design objects on an individual
basis.
AR0111 (v1.1) April 26, 2005 1