In electronic devices that send and receive signals like mobile uses High-frequency PCB, this PCB can be used for transmission of radio waves, microwaves.
The operating frequency for this board is from five hundred Mega-Hertz to two Gigahertz. To get a high value of frequency from this board such materials are used that fulfill the characteristic for a high-frequency generation.
So the strength of the transmitted signal can be varied if there is variation in the features of the material of this board like if there is a change in the value of Er (Dielectric Constant or Relative Permittivity its value for different PCB materials is 2.5 to 4.5 ) of board material will vary the impedance of this PCB.
Teflon can also be used for the production of this PCB it has a frequency value of five Gigahertz.
Some producers also used FR4 (flame resistant) for the production of this board but it also has a drawback that it can operate for one Gigahertz to Ten Gigahertz frequency range, with larger frequency value it creates problems.
If we do a comparison between Teflon and RF4 related to dielectric constant, dissipation factor then the Teflon is the best option for this PCB but its price is higher than RF4.