High Frequency High Speed PCB

What is a High Frequency High Speed PCB?

High frequency high speed PCB refers to printed circuit boards with a frequency above 1GHz. The physical properties, precision and technical parameters of high frequency high speed PCBs are very high. High frequency high speed PCBs are often used in communication systems, automotive ADAS systems, satellite communication systems, radio systems, etc.

What are the Parameters of High Frequency High Speed PCB?

The production process of high frequency high speed PCBs is basically the same as that of ordinary PCB boards. The key to realizing high frequency high speed PCBs lies in the properties of raw materials, that is, the characteristic parameters of raw materials. The main material of high frequency high speed PCB boards is high frequency high speed copper-clad laminates. The core requirements of high frequency high speed PCBs are low dielectric constant (Dk) and low dielectric loss factor (Df). In addition to ensuring lower Dk and Df, the consistency of Dk parameters is also one of the important factors to measure the quality of high frequency high speed PCBs. In addition, another important parameter is the impedance characteristics of high frequency high speeds and other physical characteristics.

The dielectric constant (Dk) of high frequency high speed PCB materials must be small and stable. Generally speaking, the smaller the better, the signal transmission rate is inversely proportional to the square root of the material dielectric constant. High dielectric constant can easily cause signal transmission delays.

The dielectric loss (Df) of high frequency high speed PCB substrate materials must be small, which mainly affects the quality of signal transmission. The smaller the dielectric loss, the smaller the signal loss.

Impedance of high frequency high speed PCB: actually refers to the parameters of resistance and reactance. Impedance control is the most basic principle for us to design high frequency high speed PCBs, because PCB lines should consider plugging and installing electronic components, and after plugging, consider electrical conductivity and signal transmission performance and other issues, so the lower the impedance, the better. Generally, PCB board factories will guarantee a certain degree of impedance error during high frequency high speed PCB processing.

High frequency  high speed PCB substrates should have low water absorption, and high water absorption will cause dielectric constant and dielectric loss when damp.

How to Measure the Parameters of High Frequency High Speed PCB Materials?

As we mentioned just now, the production process of high frequency high speed PCBs is basically the same as that of ordinary PCBs. The characteristic parameters of high frequency high speed PCBs mainly depend on the characteristic parameters of PCB materials. Therefore, in order to produce high frequency high speed PCB boards that meet the requirements, in addition to adopting corresponding processes, it is more important to use suitable synthetic materials for high frequency high speed PCBs.

Therefore, as a manufacturer of high frequency high speed PCBs, R&D designers must first test the materials of the PCB to confirm the characteristic parameters; the parameters are fitted to generate a prototype board of high frequency high speed PCB, and then the prototype board is verified and tested, and iterated continuously. After meeting the requirements, mass production is carried out. In the process of mass production, high frequency high speed PCBs are tested by random inspection or full inspection as required.

High frequency high speed PCB Material Testing

As a supplier of high frequency high speed PCB materials, it is necessary to understand the characteristics of its own materials, and make the characteristic parameter specifications of the materials provided to customers to confirm whether it can meet the requirements of high frequency high speed PCB characteristics. Therefore, it is necessary to test the raw materials themselves. These high frequency high speed PCB materials include various wave fiber cloth materials and various resin materials or synthesized copper clad laminates.

In order to meet the signal integrity requirements of different applications, in addition to analyzing the dielectric constant Dk and dielectric loss Df of the material itself to achieve effective high frequency high speed PCB design, it is also necessary to conduct S-parameter and high frequency  high speed PCB design. Tests such as TDR impedance involve many technical details, such as instrument calibration, fixture extraction and de-embedding (AFR) and transmission line simulation testing.

The difference between High Frequency PCB and High Speed PCB

Dielectric constant Dk and dielectric loss Df

When it comes to high frequency high speed PCBs, it is inevitable to talk about two concepts: "dielectric constant Dk" and "dielectric loss Df". The high frequency high speed PCB dielectric layer used for high-speed digital signal transmission not only acts as an insulating layer between conductors, but more importantly, it plays the role of "characteristic impedance", and also affects signal transmission speed, signal attenuation and heat generation.

The size of dielectric loss (Df) indicates the degree of attenuation of signal transmission. This attenuation of signal transmission is often consumed as heat. With the digital signal transmission of high frequency high speed PCB, signal attenuation and heat consumption will inevitably increase rapidly with the high frequency high speed digital signal transmission. For high frequency high speed digital signal transmission, the smaller the dielectric loss (Df), the better. In the development process of high frequency high speed PCB products, the dielectric constant (Dk) and dielectric loss (Df) of the board are required to develop in a smaller direction. However, there are still some differences in the demand for board materials for high frequency high speed PCB products.

High Speed PCB Material Properties

high speed PCB products pay more attention to the dielectric loss (Df) of the board. The grades of high speed PCB materials commonly used in the market are also divided according to the size of the dielectric loss (Df). Different high speed PCB materials are divided into conventional loss, medium loss, low loss, extremely low loss, and ultra-low loss according to the dielectric loss of the substrate. Five transmission signal loss corresponding grades.

High frequency PCB material characteristics Compared with high speed PCB materials, high frequency PCB materials pay more attention to the size and change of material dielectric constant (Dk). High frequency PCB products are very sensitive to changes in material dielectric constant (Dk). Therefore, the focus of high frequency PCB materials is the stability of the dielectric constant (Dk), as well as the thickness of the material medium, the temperature coefficient of the material, and the strobe performance of the material. There is no clear classification standard for high frequency PCB materials in the industry, but there are many types.

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