Advantech SOM-ETX Design Guide
4.1.1 Four layer board stack-up
Figure 4.1 illustrates an example of a four-layer stack-up with 2 signal layers and 2
power planes. The two power planes are the power layer and the ground layer. The
layer sequence of component-ground-power-solder is the most common stack-up
arrangement from top to bottom.
L1 Signal Layer
Prepreg
L2 Ground Layer
Core
L3 Power Layer
Prepreg
L4 Signal Layer
Total
Thickness
62 mils
62
mil
s
Figure 4-1 Four-Layer Stack-up with 2 Signal Layers and 2 Power Planes
Layer Layer
Signal-End Signals
Differential Signals
Dielectric
Thickness
(mil)
No Type
Width
(mil)
Impedance
(ohm)
Width
(mil)
Impedance
(ohm)
Width
(mil)
Impedance
(ohm)
0.7 L1
Signals
6/6
55+/-10%
6/7/6 100+/-10% 6/5/6 90+/-10%
5
Prepreg
1.4 L2
Ground
47
Core
1.4 L3
Power
5
Prepreg
0.7 L4
Signals
6/7/6
90+/-10%
6/6
55+/-10%
100+/-10% 6/5/6
USB differential
Signals
Notes :
Target PCB Thickness totals 62mil+/-10%
58
Chapter 4 General Design Recommendations
