What Are The Material Factors That Influence High-Speed/Frequency Transmitting?

More and more designs of PCB is having high speed/frequency transmitting demands. It seems that this is the trend of electronic products and future. Following this trend, do you know what the material factors that influence the signal transmission are?

1) The flatness of copper – It says that better flatness of copper can help decreasing signal loss of transmission.
2) Dielectric constant (DK) – The main factor of determining how fast of the speed and how less of the signal transmission loss, the lower the better.
3) Dissipation factor (DF) – The main factor of signal loss to the near conductor of the transmitting route, the lower the better.

Five levels of signal transmission loss.

	Standard loss	Middle loss	Low loss	Very low loss	Ultra low loss
DK	3.9 ~ 4.5	3.6 ~ 4.4	3.2 ~ 3.8	3.1 ~ 3.6	2.5 ~ 3.2
DF	≧ 0.02	0.01 ~ 0.02	0.01 ~ 0.006	0.003 ~ 0.006	≦ 0.003