Working with the Width Design Rule on a PCB in Altium Designer

Rule category: Routing

Rule classification: Unary

Summary

This rule defines the width of tracks placed on the copper (signal) layers.

Constraints

Constraints for the Width rule, which apply to all layers. Enter layer-specific values in the grid (hover the cursor over to show).

• Preferred Width - specifies the preferred width to be used for tracks when routing the board.
• Min Width - specifies the minimum permissible width to be used for tracks when routing the board.
• Max Width - specifies the maximum permissible width to be used for tracks when routing the board.

• Check Tracks/Arcs Min/Max Width Individually - checks individual widths of tracks and arcs fall within the minimum and maximum range.
• Check Min/Max Width for Physically Connected - checks the width of routed copper formed by a combination of tracks, arcs, fills, pads, and vias falls within the minimum and maximum range.
• Use Impedance Profile - this option becomes available when there is at least one impedance profile defined in the Layer Stack Manager. When enabled, use the drop-down to select the impedance profile desired. When the rule is configured in this mode, the Preferred Width required on each routing layer is calculated as part of the specified impedance profile. Once the rule is defined, as you route a net that falls under the scope of the rule, the track width will automatically be set to the width required to meet the specified impedance for that layer. When this option is enabled the Preferred Width cannot be edited in the rule, but the Min Width and Max Width values can.
  ► Learn more about Configuring the Layer Stack for Controlled Impedance Routing
• Show values for layer stack - this option appears in the dialog when there are multiple layer stacks defined in the Layer Stack Manager. If the board includes multiple layer stacks then the Width Constraints must be configured for each of the layer stacks, using either the all-layer fields above the image or the layer-specific fields in the Layer Attributes Table.
  ► Learn more about Defining and Configuring Substacks

Configure the Constraints for each layer stack in the design (hover the cursor over the image to show a different stack).

• Layer Attributes Table - the grid region at the bottom of the dialog displays all signal layers defined in the layer stack, unless the Use Impedance Profile option is enabled. If this option is enabled, then only the layers available as part of the selected impedance profile will be displayed. The minimum, maximum and preferred routing widths are displayed, as well as other layer-specific information. The routing width fields can be set globally by defining the values in the constraint fields above the image, or individually by typing values directly into the table. When the Use Impedance Profile option is enabled, the required width entries will be automatically calculated and entered for each layer in the table. In this mode the Preferred Width values cannot be edited, but the Min Width and Max Width values can.

How Duplicate Rule Contentions are Resolved

All rules are resolved by the priority setting. The system goes through the rules from highest to lowest priority and picks the first one whose scope expression matches the object(s) being checked.

Rule Application

The Preferred Width setting is obeyed by the Autorouter.

The Min Width and Max Width settings are obeyed by the Online DRC and Batch DRC. They also determine the range of permissible values that can be used during interactive routing (press Tab key while routing to change the trace width within the defined range, through the Properties panel). If a value is entered outside of this range, it will automatically be clipped.

Note

The width of each net in a differential pair is monitored by the applicable Differential Pairs Routing rule.