Kontron COMe Starterkit Eval T2 - Manual (Page 181)

Carrier Board PCB Layout Guidelines
In order to determine the necessary trace width, trace height and spacing needed to fulfill the
requirements of the interface specification, it's necessary to use an impedance calculator.
PICMG ® COM Express ® Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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Ground or power
plane
Ground or power
plane
Low speed, non
periodic signal
High speed,
periodic signal
Avoid 90° turns,
use 135° turns
instead
Avoid stubs
Don't cross plane splits
and avoid crossing
over anti-etch
Length difference
must be matched
Maintain
parallelism
s
50
W
W
S
All dimensions given in
mils
Avoid vias
20
Differential pair
Differential pair