PCB Technical - High TG circuit board PCB design

Fast proofing of high-precision TG circuit boards With the advancement of electronic technology, the complexity and scope of application of PCBs (printed circuit boards) have been rapidly developed. Those who are engaged in high-frequency must have the corresponding basic theoretical knowledge, and at the same time should have a rich experience in high-frequency PCB manufacturing. In other words, whether it is PCB schematic drawing or PCB design, you should think about the high-frequency working environment in which it is located in order to design a more ideal PCB. This article mainly discusses some problems in high-frequency PCB design based on Protel 99 SE from the two aspects of manual planning and wiring of high-frequency PCB.

1. Planning and design
Although it has the function of automatic planning, it cannot completely meet the working requirements of high-frequency circuits. It is often necessary to rely on the experience of the PCB designer and according to the detailed situation, first use manual planning to optimize and adjust the location of local components, and then separate automatic planning. Complete the overall design of the PCB. Whether the planning is reasonable or not directly affects the life, stability, EMC (electromagnetic compatibility) of the product, etc. It must be based on the overall planning of the PCB board, the operability of the wiring and the manufacturability of the PCB, mechanical structure, heat dissipation, EMI (electromagnetic compatibility), etc. Comprehensive consideration in terms of interference), reliability, and signal integrity.
Generally, first place the components in a fixed position related to the mechanical size, then place the special and larger components, and finally place the small components. At the same time, it is necessary to coordinate the wiring requirements, the placement of high-frequency components should be as compact as possible, and the wiring of signal lines should be as short as possible, so as to reduce the interference of signal lines.
High-frequency circuits often have high integration and high wiring density. The use of multilayer boards is not only necessary for wiring, but also an effective means of reducing interference. Protel for Windows V1.5 can provide 16 copper wire layers and 4 power layers. A reasonable choice of the number of layers can greatly reduce the size of the printed board, and can adequately use the intermediate layer to set the shielding, which can better complete the nearby grounding and be effective Ground to reduce parasitic inductance, can effectively shorten the transmission length of the signal, can greatly reduce the interspersed interference between signals, and so on. All of these are beneficial to the reliable operation of high-frequency circuits. When the same materials are present, the noise of a four-layer board is 20dB lower than that of a double-sided board. However, the higher the number of layers, the more complicated the manufacturing process and the higher the cost. TG circuit board quick proofing

The less the lead bends between the pins of the high-speed circuit device, the better. The lead wire of high frequency circuit wiring is best to adopt a full straight line, and 45-degree broken line or circular arc can be used for turning machine. This kind of request is only used to improve the fixing strength of the steel foil in low-frequency circuits, while satisfying this request in high-frequency circuits can reduce the external emission and mutual coupling of high-frequency signals. There are two pre-settings when using Protel for routing: one is to schedule 45/90 Line or 90 ArcLine routing in the Track Mode submenu of the Options menu; the other is the RoutingPasses dialog opened in the Setup Autorouter item of the Auto menu Box When Add Arcs is selected, the corners will be rounded when the automatic routing is completed.