Findings: DRC and ERC

Every DRC and ERC rule name with its severity and one line on when it fires, and what makes a board orderable. The rule values these checks read and their overrides are in rules.md; how findings print is in cli.md.

DRC

DRC runs on every compile. Each finding has a rule, a severity, error, warning or info, the last never counting against a board, a message with the measured and required values, a position and usually a layer. cli.md shows how findings print.

Rule	Severity	Fires when
short	error	copper of two nets touches, or copper with no net touches other copper
clearance	error	copper of two nets is closer than the clearance of the pair, see rules.md Overrides; names an override that set it
track-width	error	a track is narrower than minTrackWidth, or a part's trackWidth
edge-clearance	error	copper other than zones is closer than edgeClearance to the outline
via-drill	error	a via drill is below minViaDrill
via-size	error	a via diameter is below minViaDiameter
annular-ring	error	a via ring is below minAnnularRing, or a plated pad ring below minPadAnnularRing
drill	error	a pad drill, or a via drill that passed via-drill, is below minDrill
hole-to-hole	error	two holes of any kind are closer than minHoleToHole, edge to edge
hole-to-copper	error	copper of another net or no net is closer than holeClearance to a hole edge
unconnected	error	a net is split into islands; one finding per missing connection, with both ends
route-failed	error	the autorouter could not route a leg, see autorouter.md
keepout	error	a track, via or pour fill of a kind a keepout forbids is inside it
pour-in-keepout	warning	a keepout that forbids pours leaves a pour with no fill; see layout.md Keepouts
pair-gap	error	a coupled section of a differential pair is more than 0.01 mm off the pair gap; see pairs.md
pair-skew	error	the two tracks of a pair differ in length by more than its skew tolerance, 0.1 mm by default, after tuning; see pairs.md
pair-uncoupled	warning	the uncoupled length of a pair exceeds the class uncoupled, 5 mm by default
length	error	a route with .length() is outside its range after tuning, see length.md
length-match	error	the routes of a .match() group spread wider than its tolerance after tuning, see length.md
silk-width	warning	a silkscreen graphic or text is thinner than silkMinWidth
silk-over-pad	warning	a silkscreen stroke runs into a mask opening on the same side
mask-web	warning	the solder mask between two pad openings is narrower than maskWeb, one finding per part for pads of one part, see rules.md Mask web
silk-over-edge	warning	silkscreen ink runs past the outline or into a cutout
edge-courtyard	error	the courtyard of a part is within the edge band, see rules.md Edge band
edge-silk	error	silkscreen ink is within the edge band
edge-pad	error	a pad is within the edge band
courtyard	warning	the courtyards of two footprints overlap by 10 µm or more; a shallower overlap passes, as in KiCad
outline	warning	Edge.Cuts does not form a closed outline
cutout-outside	error	an Edge.Cuts ring other than the outline, the largest ring, crosses it or lies off the board
reference-mate	error	a pad of a referenced board's mating connector lands more than 0.1 mm from every pad of the local part, see references.md
reference-net	error	with mate.nets, a pad of the local mating part meets a remote pad of another net than the mapping wants
reference-collision	warning	a body or the slab of a referenced board reaches more than 0.1 mm into this board's slab or a part body, or into another reference's slab or body, its height from height, else the model box
fab-mismatch	error	a copper or outline Gerber read back differs from the board; only from pcbjs build and check --fab, see fab-set.md
single-pad	warning	a net has only one pad
thermal-spokes	warning	a pad joins a pour through fewer than thermal.minSpokes spokes that reach its fill, after the other directions were tried, counting the tracks and vias of its net that join it on that layer; see pours.md Thermal reliefs
thermal-spoke-width	warning	a pour's thermal spokes are narrower than its min width; they are kept
teardrop-dropped	info	a teardrop would come within the clearance of other copper, a hole, the edge or a keepout even at half size, so it is left out; see routing.md Teardrops
net-loop	warning	the copper of a net, pours left out, closes a loop: a hole in a layer's copper or a cycle through vias and plated pads; names the net and the segments, with the source of a hand chain; .loop() on a route of the net or loops: true in its class silences it; a pin strap, a loop whose edges all lie in one part's courtyard and that meets no pad of another part, is not reported; see autorouter.md Joins and loops
trunk-narrow	info	a joining leg could not widen the thinner trunk it met without breaking a clearance, so it ran to its pad, or joined and left the trunk thin; see autorouter.md Joins and loops
stitch-empty	info	a stitch() call placed no via: the net has no fill on a listed layer, or no lattice point has room; see pours.md

• Connectivity is computed from copper overlap per layer: pads, tracks, vias, each piece of a zone fill, and copper graphics with a net; a thermal pad overlaps the fill only through its spokes. The missing connections are the ratsnest and the unconnected findings, counted in the summary.
• The clearance per pair of items is set as in rules.md Overrides; same-net copper needs none, and the autorouter and the zone fill keep it. Between the tracks and vias of a differential pair the pair gap replaces a larger class clearance, never below clearance, see pairs.md. itemClearance(board, a, b) in packages/compile/src/netclass.ts gives the value.
• DRC and connectivity use a spatial grid, so their time grows with the number of nearby pairs.

ERC

ERC runs on every compile, next to DRC, with findings of the same shape.

Rule	Severity	Fires when
unplaced-part	error	a part declared at module level, in a file that placed parts here, is never placed
unplaced-circuit	error	a circuit instance on this board has no layout and no part placed
unconnected-pin	warning	a pin of a placed part has no connection and no NC
single-pin-net	warning	a Net used on the board reaches fewer than two pins
net-class	warning	a net is declared with two classes, or its class is missing from a board that defines classes
impedance-width	warning	a width solved from an impedance is over twice the smaller side of the start pad, see stackup-and-rules.md
unsourced-part	warning	a BOM row has no part number, with requireSourcing: true
unsourced-target	warning	the board has sourcing tags and a BOM row has only MPN:<tag> keys for other tags
copper-weight	warning	a copper layer is heavier than 1 oz and clearance or minTrackWidth is below the fab's figure for that weight, COPPER_WEIGHT_RULES in @pcbjs/core/rules
silk-ref	warning	a part's silk ref has no clear spot within 3 mm of its courtyard and is left out, see layout.md Silk refs
silk-ref-hidden	info	silk refs of parts too small to hold their label found no spot round them and are left out; names the parts, see layout.md Silk refs
model-missing	warning	the STEP file of a footprint's model is not there, see 3d.md
sch-short, sch-missing-symbol, sch-unwired, sch-dangling, sch-overlap	error, warnings	the schematic drawing, layer: 'sch' and at in sheet mm, see schematic-graphic.md

Notes on the checks

• The silk checks look at graphics and at text strokes at their thickness. Silk text is raised to silkMinWidth when laid out, so silk-width is only a guard for it.
• silk-over-pad stops at the mask opening, which the fab clips silk off anyway; the wider silkToPad is listed in README-fab, not enforced.
• silk-over-edge measures how far silk ink runs past the outline or into a cutout; ink that only touches the edge passes.
• The zone fill and the router keep holeClearance around every hole of another net, so their copper passes hole-to-copper; routed vias also keep minHoleToHole from every hole.

Orderable

A board is orderable when it has no DRC errors, no ERC errors and nothing unconnected. README-fab then starts with STATUS: ORDERABLE. pcbjs build and pcbjs check exit with code 1 otherwise. Warnings do not block.