PCB News - High frequency PCB technology

As high-frequency PCB technology and products occupy a more and more important position, high-speed development of high-frequency PCB board has also appeared. One of the more important aspects is the selection of materials with low dielectric constant and low dielectric loss factor, which is an important performance project to realize high-speed and high-frequency PCB board.In this paper, the relationship between dielectric constant and dielectric loss of substrate materials is discussed, and the relationship between them and external environment is explained accordingly, so that all kinds of substrate materials can be reasonably and correctly evaluated and used in PCB manufacturing.

At present, there are three main types of high frequency plates that have been commercialized.Polytetrafluoroethylene (PTFE) sheet;Thermosetting PPO (Polyphenyl Oxide)Crosslinked polybutadiene substrate and epoxy resin composite substrate.PTFE substrate has the advantages of small dielectric loss, small dielectric constant and small change with temperature and frequency, close to the thermal expansion coefficient of copper foil, etc.,so it has been widely used.The substrate prepared by PTFE with glass fiber and ceramic, such as RO3200, RO3210 and RO4003 series, has been able to meet the requirements of dielectric constant 2.2~10.8 and operating frequency range of 30 MHz~30 GHz.Although PTFE microwave plate manufacturing is developing rapidly, the technology adapted to PTFE microwave plate manufacturing is improved from the traditional FR-4 printed circuit manufacturing process .

At present, the rapid development of electronic information products, especially microwave devices, and the great improvement of integration and the requirements of digitization, high-frequency,multifunctional and application in special environments have posed challenges to the general PTFE high frequency plates and manufacturing processes.For the characteristics of high speed and high frequency of microwave PCB, two technical approaches are mainly adopted: on the one hand, the development is to make the high density wiring micro wire and spacing, micro aperture, thin shape and high reliability of conduction and insulation.In this way, the signal transmission distance can be further shortened to reduce its loss in transmission.

On the other hand, the substrate material with high speed and high frequency characteristics should be used.The realization of the latter requires the industry to carry out a deeper understanding of such substrate materials, research work to find out and master the accurate control of the process method, so as to achieve the choice of substrate materials and manufacturing process, performance and cost requirements can achieve a reasonable match purpose.