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Thermocouple
Whitepaper

V. 2010, Issue 1
> PCB Layout Checklist

PCB Layout
Checklist

Here is a great checklist for printed circuit board (PCB) layout
design. It has been updated from a checklist put together by Hank
Wallace. See http://www.aqdi.com/check.htm
for the complete original list. When we do a design we check all of
these things and more. Some of the items in the list are general
guidelines. Often we need to use our engineering judgment on the
tradeoff between size, cost, testability, and manufacturability of
the board

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

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