PCB Layout Checklist - Voler Systems

Written by Walt Maclay | Jul 11, 2009 8:00:00 AM

When we do printed circuit board (PCB) design we check all of the items in this PCB Layout Checklist and more. Some of the items in the list are general guidelines and we often need to use engineering judgment on the trade-off between the size, cost, testability, and manufacturability of the board. Note: This checklist was influenced by an earlier checklist put together by Hank Wallace. See http://aqdi.com/articles/electronics-design-checklist-3/ for his current version.

PCB Layout Checklist
Part Placement SMD component orientation consistent clearance for IC extraction tools all polarized components checked place thruhole components on 50 mil grid check the orientation of all connectors minimum component body spacing bypass capacitors located close to IC power pins verify that all series terminators are located near the source I/O drivers near where their signals leave the board PCB has ground turrets, power rail test points, and test points for important signals, all labeled EMI and RFI filtering as close as possible to exit and entry points in shielded areas layout PCB so that any rework or repair of a component does not require removal of other components potentiometers should increase controlled quantity clockwise mounting holes electrically isolated or not proper mounting hole clearance for hardware SMD pad shapes checked tooling holes for automated assembly sufficient clearance for socketed ICs Routing digital and analog signal commons joined at only one point check for traces running under noisy or sensitive components no vias under metal-film resistors and similar poorly insulated parts check for traces which may be susceptible to solder bridging check for dead-end traces, unless used on purpose ensure schematic software did / did not separate Vcc from Vdd, Vss from GND as needed provide multiple vias for high current and/or low impedance traces component and trace keepout areas observed ground planes where possible Dimensions hole diameter on drawing are finished sizes, after plating. finished hole sizes are >=10 mils larger than lead silkscreen legend text weight >=10 mils pads >=15 mils larger than finished hole sizes components >=0.2″ from edge of PCB test pads 200 mils from edge of board		Dimensions cont. traces >= 20 mils from edge of PCB thru-hole drill tolerance noted thru-hole soldermask tolerance noted thru-hole route tolerance noted thru-hole silkscreen legend tolerance noted trace width sufficient for current carried sufficient clearance for high voltage traces Silk Screen no silkscreen legend text over vias (if vias not soldermasked) or holes all legend text reads in one or two directions company logo in silkscreen legend company logo in foil copyright notice on PCB date code on PCB PCB part number on PCB assembly part number on PCB PCB revision on silkscreen legend assembly revision blank on silkscreen legend serial number blank on silkscreen legend all silkscreen text located to be readable when the board is populated all ICs have pin one clearly marked, visible even when chip is installed high pin count ICs and connectors have corner pins numbered for ease of location silk screen tick marks for every 5th or 10th pin on high pin count ICs and connectors Other CAD design rule checking must be turned on high frequency circuitry precautions observed extra connector and IC pins accessible on prototype boards, just in case check hole diameters for odd components: rectangular pins, spring pins soldermask does or does not cover vias no acute inside angles in foil soldermask swell checked manual netlist check check netlist for nodes with only one connection drill origin is a tooling hole PCB thickness, material, copper weight noted thermal reliefs for internal power layers solder paste mask openings are proper size blind and buried vias allowed on multilayer PCB PCB layout panelized correctly high frequency crystal cases should be flush to the PCB and grounded

PCB Layout Checklist

Part Placement

SMD component orientation consistent
clearance for IC extraction tools
all polarized components checked
place thruhole components on 50 mil grid
check the orientation of all connectors
minimum component body spacing
bypass capacitors located close to IC power pins
verify that all series terminators are located near the source
I/O drivers near where their signals leave the board
PCB has ground turrets, power rail test points, and test points for important signals, all labeled
EMI and RFI filtering as close as possible to exit and entry points in shielded areas
layout PCB so that any rework or repair of a component does not require removal of other components
potentiometers should increase controlled quantity clockwise
mounting holes electrically isolated or not
proper mounting hole clearance for hardware
SMD pad shapes checked
tooling holes for automated assembly
sufficient clearance for socketed ICs

Routing

digital and analog signal commons joined at only one point
check for traces running under noisy or sensitive components
no vias under metal-film resistors and similar poorly insulated parts
check for traces which may be susceptible to solder bridging
check for dead-end traces, unless used on purpose
ensure schematic software did / did not separate Vcc from Vdd, Vss from GND as needed
provide multiple vias for high current and/or low impedance traces
component and trace keepout areas observed
ground planes where possible

Dimensions

hole diameter on drawing are finished sizes, after plating.
finished hole sizes are >=10 mils larger than lead
silkscreen legend text weight >=10 mils
pads >=15 mils larger than finished hole sizes
components >=0.2″ from edge of PCB
test pads 200 mils from edge of board

Dimensions cont.

traces >= 20 mils from edge of PCB
thru-hole drill tolerance noted
thru-hole soldermask tolerance noted
thru-hole route tolerance noted
thru-hole silkscreen legend tolerance noted
trace width sufficient for current carried
sufficient clearance for high voltage traces

Silk Screen

no silkscreen legend text over vias (if vias not soldermasked) or holes
all legend text reads in one or two directions
company logo in silkscreen legend
company logo in foil
copyright notice on PCB
date code on PCB
PCB part number on PCB
assembly part number on PCB
PCB revision on silkscreen legend
assembly revision blank on silkscreen legend
serial number blank on silkscreen legend
all silkscreen text located to be readable when the board is populated
all ICs have pin one clearly marked, visible even when chip is installed
high pin count ICs and connectors have corner pins numbered for ease of location
silk screen tick marks for every 5th or 10th pin on high pin count ICs and connectors

Other

CAD design rule checking must be turned on
high frequency circuitry precautions observed
extra connector and IC pins accessible on prototype boards, just in case
check hole diameters for odd components: rectangular pins, spring pins
soldermask does or does not cover vias
no acute inside angles in foil
soldermask swell checked
manual netlist check
check netlist for nodes with only one connection
drill origin is a tooling hole
PCB thickness, material, copper weight noted
thermal reliefs for internal power layers
solder paste mask openings are proper size
blind and buried vias allowed on multilayer PCB
PCB layout panelized correctly
high frequency crystal cases should be flush to the PCB and grounded

Other Useful PCB Layout Checklist Tools and Documents

Christian Kuhlmann has created an interactive version of Hank Wallace’s PCB Layout Checklist at http://aqdi.com/wordpress/PCBChecklistLive.htm
Xilinx offers a good PCB Layout Checklist that focuses on signal integrity issues
Electronic Design Magazine offers a good overview of PCB design considerations in “Engineer’s Guide to High Quality PCB Design“

Other Voler Checklists and Design Guides

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