What is high-frequency PCB board?

High-frequency circuit boards are special circuit boards with higher electromagnetic frequencies. In general, high-frequency circuits can be defined as frequencies above 1 GHz. Its physical performance, precision and technical parameters are very high. It is commonly used in automotive anti-collision systems, satellite systems, radio systems and other fields.
 
At the present stage, three types of high-frequency CCL materials such as epoxy resin, PPO resin, and fluorine-based resin are used, and the epoxy resin is the cheapest, and the fluorine-based resin is the most expensive. Considering the dielectric constant, dielectric loss, water absorption and frequency characteristics, the fluorine resin is the best and the epoxy resin is poor. When the frequency of product application is higher than 10 GHz, only the fluorine-based resin printed board can be applied. Obviously, the high-frequency performance of fluorine-based resin is much higher than that of other CCL materials, but its disadvantages are poor rigidity and high coefficient of thermal expansion, in addition to high cost. For Poly tetra fluoroethylene (PTFE), a large amount of inorganic material (such as Silicon dioxide SiO₂) or a glass cloth is used as a reinforcing filler material to improve the rigidity of the CCL and reduce the thermal expansion thereof for the purpose of improving the performance. In addition, due to the molecular inertness of the PTFE resin itself, it is not easy to combine with the copper foil. Therefore, special surface treatment with the copper foil is required.
 

The high frequency of electronic equipment is a development trend, especially in the growing development of wireless networks and satellite communications, information products are moving towards high speed and high frequency, and communications products are moving toward the standardization of voice, video, and data for wireless transmissions with large capacity and high speed. Therefore, the development of a new generation of products require high-frequency CCL, satellite systems, mobile phone receiving base stations and other communications products must use high-frequency circuit boards, in the next few years will inevitably develop rapidly, high-frequency substrates will be a lot of demand.
 
The basic characteristics of high-frequency PCB materials require the following:
 
1) The dielectric constant (Dk) must be small and stable. Usually, the smaller the signal, the better the transmission rate of the signal is inversely proportional to the square root of the dielectric constant of the material. High dielectric constant can easily cause signal transmission delay.
 
(2) The dielectric loss (Df) must be small, which mainly affects the quality of signal transmission. The smaller the dielectric loss, the smaller the signal loss.
 
(3) The coefficient of thermal expansion of the copper foil is as consistent as possible, because the inconsistency will cause copper foil separation in the cold and hot changes.
 
(4) Low water absorption, high water absorption will affect the dielectric constant and dielectric loss when exposed to moisture.
 
(5) Other heat resistance, chemical resistance, impact strength, peel strength, etc. must also be good.