Introduction to the dielectric constant of FR4 board

Introduction of circuit board dielectric constant:

The dielectric constant of PCB is generally 4.2-4.7 relative to air at room temperature, but this value usually changes with temperature changes. Generally speaking, the maximum change value can be in the temperature range of 0-70 degrees. Reach between 20%. The change of the dielectric constant will cause the delay of the line to change, reaching about 10%, and the higher the temperature, the greater the delay. And it also changes with the frequency, the higher the frequency, the lower the dielectric constant.

 Impedance calculation parameter table 1 (new)

1. Different media thickness and different combinations

No. Theoretical thickness (MM) Theoretical thickness (MIL) Combination method Dielectric constant

1 0.05 1.97 106*1 3.9

2 0.07 2.76 1081*1 4.2

3 0.08 3.2 LPP1080*1 4.2

4 0.1 4 106*2 3.9

5 0.12 4.72 106+1080 4.2

6 0.12 4.72 2116*1 4.2

7 0.14 5.5 1080*2 4.2

8 0.15 6 106*3 3.9

9 0.17 6.7 2116+106 4.2

10 0.17 6.7 1080+106*2 4.2

11 0.19 7.5 1080+2116 4.2

12 0.19 7.5 7628*1 4.5

13 0.21 8.27 1080*3 4.2

14 0.22 9 106*2+2116 4.2

15 0.24 9.45 7628+106 4.5

16 0.24 9.45 2116*2 4.2

17 0.26 10.24 7628+1080 4.5

18 0.26 10.24 1080*2+2116 4.2

19 0.29 11.42 7628+106*2 4.5

20 0.29 11.42 2116*2+106 4.2

21 0.31 12.2 7628+2116 4.5

22 0.31 12.2 2116*2+1080 4.5

23 0.33 13 7628+1080*2 4.5

24 0.38 15 7628*2 4.5

25 0.43 16.93 7628+2116*2 4.5

26 0.43 16.93 7628*2+106 4.5

27 0.45 17.72 7628*2+1080 4.5

28 0.5 19.69 7628*2+2116 4.5

29 0.57 22.44 7628*3 4.5