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Understanding Rules And Constraints

September 27, 2018 David Haboud

This webinar will discuss how Altium Designer supports your design process with hierarchical rules and constraints. Knowing how to define design guidelines enables you to create first pass designs without having to memorize every requirement.


Why use Rules and Constraints?

Every logical schematic design defines requirements for your physical PCB. Satisfying these requirements requires understanding and consistency throughout the entire design process. How do you validate every requirement while maintaining accuracy?

There are many challenges to requirement adherence, but we will focus on three challenges and how we will be able to overcome them with Altium Designer.


1. Requirement Interactions​​


Schematic/Logical Requirements

PCB/Physical Requirements





Rule Hierarchy

Conflicting Scope


2. Error Resolution


Seeing Errors Early


Associated Design Aspects


Fixing Errors While Avoiding New Ones


3. Validation and Proof


Requirement Compliance


Requirement Visibility




Overview of Rules and Constraints Key Benefits and Capabilities


  1. Define scope, category, and prioritization of design constraints.​
  2. Validate and report logical and physical design requirements​​.
  3. Automate and resolve DFM and electrical checks.

Electrical and Design Rules

Rules and Constraint Hierarchy

Rule Wizard

Real-time Design Guidance

Electrical/Design Rule Check (ERC/DRC)

Validation Reports


Questions and Answers

Below are the top asked questions for the webinar. Questions focusing on specific support questions and feature requests are omitted.

Q: What type of rules and constraints exist?

A: See the full list of categories and constraint types supported by Altium Designer on our documentation page, PCB Rules and Constraints. The following are some of the most commonly used rules and constraints:


Electrical - Matched Length and Impedance.

Routing - Width, Routing Via Style, Fanout Control, and Differential Pairs Routing.

Mask - Solder and Paste Mask Expansion.

Manufacturing - Minimum Annular Ring, Hole To Hole Clearance, Minimum Solder Mask Sliver, Silk To Solder Mask Clearance, Silk To Silk Clearance, and Board Outline Clearance.

Placement - Component Clearance and Orientation.



Q: Can we create rule templates?

A: You can import and export RUL files and share them with your team to ensure everyone is using the same rules and constraints. You can save them with Altium Vault and Altium NEXUS Server to ensure your rules are in a centralized location for everyone.

Q: What are the filters other than 'room' that can be used for localized rules?
A: You can define the scope of rules with pad name, net, classes, and just about any design aspect.

Q: Where can we get access to the Query functions?
A: You can find the Query Language Reference on our documentation page following the link: https://www.altium.com/documentation/18.1/display/ADES/((Query+Language+Reference))_AD

Q: Did you have to do anything to get the trace to neck down when it entered the room?

A: The rule hierarchy and scope I created in the webinar allow automatic neck-down of the trace as it enters the room with the custom query: TouchesRoom(‘BGA_Area’).


We discussed the requirement adherence challenges and how rules and constraints help resolve those challenges. You can review below the functionality in Altium Designer and the challenges they address in turn. Properly using rules and constraints allows you to meet and validate all requirements easily without having to manually keep track of everything necessary for a successful design. You are able to prevent, navigate, and correct errors in real-time and benefit from design automation to give you a helping hand.

Requirement Interactions

Define scope, category, and prioritization of design constraints.

Electrical and Design Rules

Rules and Constraint Hierarchy

Rule Wizard


Error Resolution

Automate and resolve DFM and electrical checks.

Real-time Design Guidance

Electrical/Design Rule Check (ERC/DRC)


Validation and Proof

Validate and report logical and physical design requirements.

Validation Reports


About the Author

David Haboud

David Haboud is a Product Marketing Engineer at Altium. He studied electrical engineering with an emphasis in computer architecture and hardware/software design at the University of Southern California. David began his career as an embedded software engineer in the aerospace industry and has always strived to make it easier for hardware and software engineers to communicate. During his tenure as an embedded software engineer, he focused on firmware development and data acquisition for auxiliary power units. In his spare time, David hosts and performs in improvisational and stand-up comedy nights in San Diego, California.

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