38
Board Layout Guidelines
NOTE:
Each interface sets the trace spacing based on its signal integrity of differential impedance
requirements. For the purposes of the building the transmission line models, it is assumed the artwork is
very accurate and therefore a constant. Thus, all the variability in the trace spacing is the result of the
tolerances of the trace width.
Stripline
4.0
2.5
5.5
Trace Spacing (mil)
Microstrip
15.0
-
-
Each interface sets the trace spacing based on its
signal integrity of differential impedance
requirements. For the purposes of the building the
transmission line models, it is assumed the artwork
is very accurate and therefore a constant. Thus, all
the variability in the trace spacing is the result of the
tolerances of the trace width.
Stripline
12.0
-
-
Total Thickness (mil)
FR4
62.0
56.0
68.0
Trace Velocity (ps/in)
Microstrip
-
135
141
Velocity varies based on variation in Er. It cannot be
controlled during the fab process.
Stripline
167
178
Trace Impedance
(ohms)
Microstrip
50
42.5
57.5
Stripline
50
45
55
Table 5.
Motherboard Stack Up, Stripline and Microstrip (Sheet 2 of 2)
Variable
Type
Nominal
(mils)
Minimum
(mils)
Maximum
(mils)
Notes
Figure 12.
Motherboard Stackup Recommendations
B 3 5 5 5 -0 1
L 1
L 2 ( G N D )
L 8
L 7 (G N D )
T r a c e W id th
Tot
a
l Thic
k
ens
s
T ra c e H e ig h t 1
P la n e T h ic k n e s s
S o ld e r M a s k T h ic k n e s s
L 1
L 6
L 4 ( V C C )
L 5 ( V C C )
T ra c e H e ig h t 3
L 3
T ra c e H e ig h t 2
L 3
L 6
M ic ro s tr ip
M ic ro s tr ip
S trip lin e
T ra c e W id th
T ra c e S p a c in g
S tr ip lin e
C o re T h ic k n e s s
M ic ro s tr ip T r a c e T h ic k n e s s
S tr ip lin e T ra c e T h ic k n e s s
T r a c e S p a c in g
Содержание 80331
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