Failed: reduce the live PCB from 20 to 19 airwires. The sole HOST_SPI_SCK routing attempt timed out without adding copper; final count is 20.
Completed, then reverted: one structural placement candidate, C24 only. No second component or alternate placement was attempted.
Completed: check both C24 connections in the same pass; both remained physically connected after moving.
Completed: atomic rollback of the entire unsuccessful experiment to checkpoint #26b178b7, followed by fresh routing-state and scoped DRC inspection.
Unattempted, by scope: unrelated-net routing, broad cleanup, rule changes, new components, and further structural candidates.
Geometry and exact placement
Live geometry identified C24 as a 0402 VCCAUX decoupler in the specified north-side area. Its original Top-side bounds were approximately x −6.91…−6.11 mm and y 11.62…13.20 mm. Adjacent features include the 3V3 diagonal to the north, the FPGA_CLK_25M routing to the east, and HEARTBEAT routing at x −7.4 mm to the west. The move opened space immediately north of C24 and brought the capacitor closer to the FPGA; the failed route means C24 was not established as the sole routing blocker.
Table
Property
Original/final restored
Temporary experiment
Component
C24
C24
Center X
−6.5067 mm
−6.5067 mm
Center Y
12.4089 mm
11.9089 mm
Rotation
97°
unchanged
Side
Top
unchanged
Translation
—
0.5000 mm south
U1, R19, and all other components stayed fixed. The placement tool reported zero overlaps, keepout violations, or out-of-bounds components for the temporary move.
C24 copper and connection reconstruction
Before moving, removed only C24's obsolete upper P1 landing segment to prevent proximity to its shifted ground pad:
This was a 0.5 mm-wide Top segment from (−6.448202, 11.932478) to (−6.448202, 11.443552) mm. Its lower adjoining segment and the existing 2V5 via were retained.
P1 / 2V5: routing call from C24:P1 to retained trace ending 74371716f09fe0fa1d695b06dd5cb3ca, requested width 0.5 mm, returned already-connected, one copper island, no unconnected pairs. The shifted P1 directly reached the retained landing copper, so no new trace was necessary.
P2 / GND: routing call from C24:P2 to C23:P2, requested width 0.15 mm, returned already-connected, one copper island, no unconnected pairs. Existing ground copper connectivity remained; no new trace was necessary.
Airwire count after each connection check was 20.
Rollback restored both C24's original position and the deleted P1 segment. No schematic wiring changed.
Router reported source landing: trace at (9.250, 8.930) mm.
Requested trace width: 0.15 mm.
Search limit: 120 seconds, one attempt only.
Result: time-limit, two islands remaining, zero connected pairs, one unconnected pair.
Added SCK traces/vias: none. Consequently there is no successful route layer/length/via count to report.
Verification and preservation
Atomic revert returned success and undid exactly the two mutation commits: the C24 movement and its P1 segment deletion. Fresh scene-tree inspection confirmed C24 restored to (−6.5067, 12.4089) mm, Top, 97°.
Fresh routing-state inspection confirmed 20 airwires, including the unchanged HOST_SPI_SCK target, and the baseline 90 redundant traces in 29 groups. Existing unrelated routing and protected USB copper were untouched; no broad redundant-copper cleanup was performed.
Final DRC query reviewed at 2026-09-18T16:49:35.403Z, requesting airwires, overlapping copper, overlapping traces, invalid layers, under-connected vias, protected intrusions, component-body overlaps, and keepouts. It returned only the 20 airwire Errors, with no other findings in those requested checks. This is not a claim that the overall board is complete or manufacturing-ready.
Preflight also reported an existing Warning that the 2V5 width exceeds U1:VCCAUX_F15 pad size, and an Info via-at-SMD advisory for EP. Those were outside this repair's scope and were not changed.
The bounded experiment is finished; the requested 19-airwire goal remains unmet. No further routing or placement retries were made.