Altium NEXUS Documentation

Working with the SMD Entry Design Rule on a PCB in Altium NEXUS

Created: November 29, 2021 | Updated: November 29, 2021
All Contents

Rule category: SMT

Rule classification: Unary

Summary

This rule specifies the direction(s) a track can enter, or exit, an SMD pad.

All design rules are created and managed within the PCB Rules and Constraints Editor dialog. For a high-level view of working with the design rules system, see Defining, Scoping & Managing PCB Design Rules.

Constraints

Default constraints for the SMD Entry rule.
Default constraints for the SMD Entry rule.

  • Any Angle – if enabled, the track can enter/exit the pad at any angle, and at any point along its edge.
  • Corner – if enabled, the track can enter/exit through a pad corner.
  • Side – if enabled, the track can enter/exit at 90 degrees on either side of the pad. The longer edge of the pad is considered the side, note that the side option is only applied if the Side length > 2x End length. For example, if the pad is 2mm x 1mm then the side option is ignored (all sides are treated as ends). If the pad is 2.1mm x 1mm then the side option is applied.

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

Online DRC, Batch DRC, and Interactive Routing.

Notes

  • The rule applies to surface mount pads only, that is, a pad defined on a single copper layer.
  • The end of the pad is determined from the pad dimensions, the ends are the shorter edges.
  • Pads can always be entered from either end (the shorter edge)
  • The rule is applied on both routing out of the pad (exit) and into the pad (entry).
  • The rule works in harmony with the SMD To Corner design rule, configure both to ensure neat SMD routing.

    The SMD Entry rule specifies where the route is allowed to enter/exit the SMD pad, all rule checkboxes are cleared in this example animation. Use the SMD to Corner rule to define the distance to the first corner.
    The SMD Entry rule specifies where the route is allowed to enter/exit the SMD pad, all rule checkboxes are cleared in this example animation. Use the SMD to Corner rule to define the distance to the first corner.

  • Once the pad has been exited, the route is kept away from the pad. The software does not allow the route to re-enter the pad and then re-exit without regard to the SMD rules.
  • SMD rules are ignored if the pad exit is blocked (they are already ignored during pad entry in this situation). Note that if there is a pad exit available that does not violate the SMD to corner rule, that exit will be used.
  • Miters are not created in violation of SMD rules. The software favors the SMD to corner rule over the miter, allowing the miter to collapse to zero if required.
  • Stubs that follow the SMD rules are created in Any Angle routing mode. In this mode, once the first track segment has been placed arcs will be included in the corners. If you need an arc in the first corner, place the exit stub before attempting to create a corner.
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