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layout-checklist.md

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Layout review checklist

General

  • Schematic review complete and signed off, including pin swaps done during layout
  • Layout DRC 100% clean

Decoupling

  • Decoupling caps as close to power pins as possible
  • Low inductance mounting used for decoupling (prefer ViP if available, otherwise "[]8" shaped side vias

DFM / yield enhancement

  • All design rules within manufacturer's capability
  • Minimize use of vias/traces that push fab limits
  • Controlled impedance specified in fab notes if applicable
  • Confirm impedance calculations include soldermask, or mask removed from RF traces
  • Stackup verified with manufacturer and specified in fab notes
  • Board finish specified in fab notes
  • If panelizing, add panel location indicators for identifying location-specific reflow issues
  • (recommended) Layer number markers specified to ensure correct assembly
  • Fiducials present (on both sides of board) if targeting automated assembly
  • Fiducial pattern asymmetric to detect rotated or flipped boards
  • Soldermask/copper clearance on fiducials respected
  • Panelization specified if required

Footprints

  • Confirm components are available in the selected package
  • Confirm components (especially connectors and power regulators) are capable of desired current in the selected package
  • Verify schematic symbol matches the selected package
  • Confirm pinout diagram is from top vs bottom of package
  • (recommended) PCB printed 1:1 on paper and checked against physical parts
  • 3D models obtained (if available) and checked against footprints
  • Soldermask apertures on all SMT lands and PTH pads

Differential pairs

  • Routed differentially
  • Skew matched
  • Correct clearance to non-coupled nets

High-speed signals

  • Sufficient clearance to potential aggressors
  • Length matched if required
  • Minimize crossing reference plane splits/slots or changing layers, use caps/stitching vias if unavoidable
  • Confirm fab can do copper to edge of PCB for edge launch connectors
  • Double-check pad width on connectors and add plane cutouts if needed to minimize impedance discontinuities

Power

  • Minimal slots in planes from via antipads
  • Sufficient width for planes/traces for required current

Sensitive analog

  • Guard ring / EMI cages provided if needed
  • Physically separated from high current SMPS or other noise sources
  • Consider microphone effect on MLCCs if near strong sound sources

Mechanical

  • Confirm all connectors to other systems comply with the appropriate mechanical standard (connector orientation, key position, etc)
  • LEDs, buttons, and other UI elements on outward-facing side of board
  • Keep-outs around PCB perimeter, card guides, panelization mouse-bites, etc respected
  • Stress-sensitive components (MLCC) sufficiently clear from V-score or mouse bite locations, and oriented to reduce bending stress
  • Clearance around large ICs for heatsinks/fans if required
  • Clearance around pluggable connectors for mating cable/connector
  • Clearance around mounting holes for screws
  • Plane keepouts and clearance provided for shielded connectors, magnetics, etc
  • Confirm PCB dimensions and mounting hole size/placement against enclosure or card rack design
  • Verify mounting hole connection/isolation
  • Components not physically overlapping/colliding
  • Clearance provided around solder-in test points for probe tips

Thermal

  • Thermal reliefs used for plane connections (unless via is used for heatsinking)
  • Solid connections used to planes if heatsinking
  • Ensure thermal balance on SMT chip components to minimize risk of tombstoning

Solder paste

  • No uncapped vias in pads (except low-power QFNs where some voiding is acceptable)
  • QFN paste prints segmented
  • Small pads 100% size, larger pads reduced to avoid excessive solder volume
  • No paste apertures on card edge connectors or test points

Solder mask

  • Confirm SMD vs NSMD pad geometry
  • Adequate clearance around pads (typ. 50 um)

Silkscreen

  • Text size within fab limits
  • Text not overlapping drills or component pads
  • Text removed entirely in, or moved outside of, high component/via density areas
  • Traceability markings (rev, date, name, etc) provided
  • Silkscreen box provided for writing/sticking serial number
  • Text mirrored properly on bottom layer
  • Test points labeled if space permits

Flex specific

  • Components oriented to reduce bending forces
  • Teardrops on all wire-to-pad connections

CAM production

  • KiCAD specific: rerun DRC and zone fills before exporting CAM files to ensure proper results
  • Export gerber/drill files at the same time to ensure consistency
  • Visually verify final CAM files to ensure no obvious misalignments