EDA PCB Skill

PCB layout, component placement, and routing.

Auto-Activation Triggers

This skill activates when:

• User asks to "layout PCB", "place components", "route traces"
• User is working with .kicad_pcb files
• User asks about placement, routing, copper pours, vias
• Project has schematic but no PCB layout
• User mentions DFM, trace width, or clearance

Context Requirements

Requires:

• hardware/*.kicad_sch - Completed schematic with netlist
• docs/component-selections.md - Component details
• docs/design-constraints.json - Board size, layer count, etc.
• datasheets/ - For placement/routing recommendations

Produces:

• hardware/*.kicad_pcb - KiCad PCB file
• docs/pcb-status.md - Layout progress tracking

Workflow

1. Load Context

@docs/design-constraints.json
@docs/component-selections.md
@docs/schematic-status.md
@datasheets/ (for placement guidance)

1.5 Pre-Layout Validation

Before starting layout, verify:

Extract key constraints:

{
  "board": {
    "layers": 4,
    "thickness": 1.6,
    "dimensions": {"width": 50, "height": 40}
  },
  "dfmTargets": {
    "manufacturer": "JLCPCB",
    "minTraceWidth": 0.15,
    "minClearance": 0.15,
    "impedanceControl": true
  },
  "interfaces": {
    "usb": true,
    "highSpeedSpi": false
  },
  "thermal": {
    "maxPowerDissipation": 2.5
  }
}

Architecture Validation Warnings:

2. Initialize PCB

1. Create PCB file or open existing
2. Import netlist from schematic
3. Set board outline per constraints
4. Configure layer stackup
5. Set design rules

3. Configure Design Rules

Set rules appropriate for manufacturer:

JLCPCB standard:
- Min trace width: 0.127mm (5mil)
- Min clearance: 0.127mm (5mil)
- Min via drill: 0.3mm
- Min via annular ring: 0.13mm

4. Place Components

Priority order:

1. Fixed position items - Connectors (edge), mounting holes
2. MCU/Main IC - Central location
3. Crystal/oscillator - Within 5mm of MCU
4. Power components - Near input, thermal considerations
5. Decoupling capacitors - Adjacent to IC power pins
6. Sensitive analog - Away from noisy digital
7. Remaining components - Grouped by function

See reference/PLACEMENT-STRATEGY.md for detailed guidelines.

5. Route Critical Signals First

Priority:

1. Power delivery (wide traces, pours)
2. Crystal/oscillator (short, guarded)
3. USB differential pairs (90Ω impedance)
4. High-speed signals (length matching)
5. Sensitive analog (away from digital)
6. General signals

See reference/ROUTING-RULES.md for trace width and clearance guidelines.

6. Create Copper Pours

• GND pour on bottom layer (2-layer)
• Or GND on layer 2, power on layer 3 (4-layer)
• Thermal relief on pads
• Stitch vias for plane continuity

7. Route Remaining Signals

• Follow schematic groupings
• Minimize vias
• Avoid acute angles (use 45°)
• Keep trace lengths reasonable

8. DRC Check

• Run design rule check
• Fix violations
• Document intentional exceptions

9. Visual Review

• Generate board images
• Check silkscreen readability
• Verify component orientation marks
• Review for manufacturing issues

10. Pre-Manufacturing Review

Validation checklist before ordering:

Thermal verification:

• Power components have thermal relief
• Thermal vias under QFN/thermal pads
• Heat sink areas connected to copper pour
• No thermal bottlenecks (narrow traces for high current)

Signal integrity verification:

• High-speed signals over solid ground
• Return paths not broken by splits
• Crystal area guarded, no traces crossing
• Antenna keep-out respected (if applicable)

Output Format

pcb-status.md

# PCB Layout Status

Project: [name]
Updated: [date]

## Board Specifications
- Size: X × Y mm
- Layers: N
- Thickness: 1.6mm

## Progress
- [x] Board outline defined
- [x] Mounting holes placed
- [x] Critical components placed
- [x] All components placed
- [ ] Power routing complete
- [ ] Signal routing complete
- [ ] Copper pours added
- [ ] DRC clean

## Layer Usage
| Layer | Usage |
|-------|-------|
| F.Cu | Signals, components |
| B.Cu | GND pour, some signals |

## DRC Status
- Errors: X
- Warnings: Y
- Unrouted nets: Z

## Design Rules
- Trace width: 0.2mm (signals), 0.5mm (power)
- Clearance: 0.2mm
- Via: 0.3mm drill, 0.6mm pad

## Notes
- [Any special considerations]

## Next Steps
- [What remains to be done]

Guidelines

• Always check datasheets for recommended layouts
• Keep high-current paths short and wide
• Maintain ground plane integrity under sensitive signals
• Consider thermal management early
• Use the DRC frequently during layout

Reference Documents

Upstream documents:

Next Steps

After PCB layout is complete:

1. Run /eda-check for comprehensive validation
2. Update design-constraints.json stage to "validation"