PCB Design Rule Checks Demystified

Design Rule Check (DRC) in a PCB design is a process used to ensure that the design meets certain rules and guidelines for performance and manufacturability. DRC is typically done using specialized software tools, and it verifies the design against a set of predefined rules, such as minimum trace width, minimum clearances between traces, and minimum drill size for vias.

The DRC process checks for errors and inconsistencies in the PCB layout, such as overlapping traces, shorts, and incorrect component placement. The DRC process is an important step in the PCB design process, as it helps to identify and correct errors before the PCB is manufactured. This can save time and money by reducing the need for rework and preventing manufacturing defects. Using specialized software for DRC is an efficient and accurate way to ensure that the design meets the necessary guidelines and standards.

Dense PCB routing like this requires a full set of design rules and constraints

Allegro® Constraint Manager is a cross-platform, workbook- and worksheet-based application used to manage constraints across all tools in the Cadence PCB and IC Package design flow. Constraint Manager lets you define, view, and validate constraints at each step in the design flow, from design capture in Allegro System Capture to floorplanning and design realization in Allegro PCB Editor.

You can also use Constraint Manager with Topology Workbench to explore circuit topologies and derive electrical constraint sets (ECSets) which can include custom constraints, custom measurements, and custom stimulus.

Constraint Manager User Interface

In Constraint Manager, you work with objects and constraint sets (CSets), which capture your design requirements. Constraint Manager organizes constraints and CSets into:

• Electrical
• Physical
• Spacing
• Same Net Spacing
• Assembly
• Manufacturing

Constraint Manager is a spreadsheet-based application with an easy-to-use interface for entering constraints. Another advantage of using Constraint Manager is that it allows you to create generic constraints that you can apply to multiple nets or XNets at the same time. These reusable constraints are called CSets. At a later point in time, if your design requirements change, you can edit the generic rule. The updated rule will be automatically applied to the nets or XNets that refer to the rule. The existing routes will not modify, but may show DRCs.

Let us know your comments on the importance of DRC checks on PCB designs and any new DRCs that you feel might help PCB layout designers.