Impedance Calculation Tools; Testing Board Impedance; Microstrip And Stripline Cross-Section For 28 Ω Trace; D Field Solver Vs Zcalc - Intel VC820 - Desktop Board Motherboard Design Manual

System Manufacturing
Figure 5-2. (a,b) Microstrip and Stripline Cross-section for 28 Ω Trace
Note: Don't forget ground floods and stitching
5.3.7

Impedance Calculation Tools

The 3D Field Solvers (e.g., those by HP, Ansoft, Sonnet, and Polar) are the most accurate for
calculating impedance. Z calculators based on equations (zcalc) are also fairly accurate. The
differences are shown in
Table 5-2. 3D Field Solver vs ZCALC
H
W
W1
T
ε
r
Z0(3D)
Z0(zcalc)
5.3.8

Testing Board Impedance

The Intel Impedance Test Methodology Document should be used to ensure boards are within the
28 Ω ±10% requirement. This document can be found at: http://developer.intel.com.
5-4
a) Microstrip Cross-Section for 28 Ohm trace
10 mils
6 mils
G
4.5 mils
b) Stripline Cross-Section for 28 Ohm trace
6 mils
5 mils
G
5 mils
Table 5-2.
#1 #2
4.5 4.5
18 18
18.1 18.1
1.4 2.8
4.5 4.5
29.0 28.4
29.1 28.7
18 mils
S
13.5 mils
S
1.2 mils
#3 #4
4.2 4.8
18 18
18.1 18.1
1.4 1.4
4.5 4.5
27.6 30.4
27.7 30.4
2.1 mils
G
1.2 mils
7 mils
G
1.2 mils
#5 #6
4.5 4.5
17 19
17.1 19.1
1.4 1.4
4.5 4.5
30.2 27.9
30.2 28.0
®
Intel 820 Chipset Design Guide