KB: Net Is Too Complex or Unrouted in SI Analyzer

Solution Details

Unrouted Net Warning Despite Valid Routing

The user experienced the warning “Net is too complex or unrouted” when running Signal Integrity analysis on a simple 2 cm point‑to‑point net. The routing looked correct in the PCB layout, but only certain nets were flagged by the analyzer. The issue appeared inconsistent, even though the affected nets were visually similar to others that passed analysis.

Analyzer Cannot Detect Pad Enter Connection

Although the trace overlaps the pad copper, it does not connect to the pad center when the trace width is significantly larger than the pad diameter. For example, a 0.475 mm‑wide trace may be too wide to snap to the pad’s center reference point. This results in a visual connection that is not recognized as a valid routed net by the Signal Integrity analyzer, causing it to report the net as unrouted.

Ensure Center-Aligned Electrical Connectivity

Route a short, narrow trace segment from the pad center to the main wide track. This guarantees that the pad‑to‑trace connection is electrically valid and properly recognized by the Signal Integrity analysis engine.

Step-by-Setp Routing Workaround

1. Select the affected net in your PCB design environment.
2. Zoom in closely on the pad‑to‑track connection.
3. Verify whether the main track snaps exactly to the pad center.
4. If the track only overlaps the pad copper edge, it is not a valid connection for SI analysis.
5. Check the current trace width (for example, 0.475 mm).
6. If the trace is too wide to snap to the pad center, this confirms the root cause.
7. Create a narrow trace segment (recommended width: 0.1 mm).
8. Route this narrow trace from the exact pad center to the main wide track.
9. Ensure the starting point is the pad center reference point.
10. Ensure the narrow trace endpoint touches and is electrically connected to the wide track.
11. Verify connectivity using:
    • Net highlight
    • Connectivity or DRC checks
    • Net extraction tools
12. Re‑run Signal Integrity analysis to confirm that the warning is resolved.

Additional Notes

• This issue commonly occurs when using very wide traces on small pads, such as power nets.
• Always verify pad‑center connectivity before running SI analysis to avoid false unrouted warnings.
• Using net highlight or DRC connectivity checks helps quickly confirm whether the net is fully connected.
• In some PCB tools, grid or snap settings may interfere with center snapping—reviewing these options can prevent recurrence.
• When multiple nets exhibit the same warning, review default routing widths and ensure they are compatible with associated pad sizes.
• If the design was imported or edited from legacy data, consider re‑running net extraction or cleaning up overlapping copper that may not be recognized as a valid connection.

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