The requirements for high-frequency and high-speed materials mainly include the following points:

1、 Low dielectric constant (Low Dk)

The dielectric constant (Dk or Er) represents the amount of electrostatic energy that can be stored per unit volume of insulating material under each unit of potential gradient. The smaller the dielectric constant (or permeability) of insulating materials, the better. Low dielectric constant can improve signal transmission speed. At present, among all the boards, PTFE has the lowest dielectric constant, with a dielectric constant of 2.5 at a frequency of 1MHz, while FR-4 has a dielectric constant of about 4.7. The circuit board can be regarded as a capacitive device. When there is signal transmission in the wires, some energy is accumulated by the circuit board, causing delays in transmission. The higher the frequency, the more obvious the delay.

2、 Low dissipation factor (Df)

The dissipation factor (Df) is a measure of the functional loss of alternating current and is a characteristic of insulating materials (resins). As the frequency increases, the loss of intensity also increases, so high-frequency high-speed communication is often designed and manufactured using low dissipation factor materials. The dissipation factor is directly proportional to the observed power loss, and inversely proportional to the periodic frequency (f), the square of the potential gradient (E2), and the unit volume.

3、 Surface roughness of conductor

The surface roughness and morphology of conductors have an impact on the signal energy loss caused by resistance heating, namely conductor loss. The higher the frequency, the shorter the wavelength, and the more concentrated the signal is on the surface of the conductor when traveling between conductors, known as the "skin effect". The flatter the surface roughness, the more advantageous it is for signal transmission. In addition, the bonding strength between PCB layers is also affected by the surface roughness of the conductor. The higher the surface roughness of the conductor, the larger the bonding area between the resin and the conductor, and the higher the bonding strength.

In summary, high-frequency and high-speed materials need to have characteristics such as low dielectric constant, low dissipation factor, and flat conductor surface roughness to meet the requirements of high-frequency and high-speed signal transmission