Microwave Tech - What are some practical skills in high-frequency PCB design

The goal of PCB design is smaller, faster and lower cost. And because the interconnection point is the weakest link in the circuit chain, in the RF design, the electromagnetic properties at the interconnection point are the main problems faced by the engineering design. Each interconnection point must be investigated and the existing problems must be solved.
The interconnection of the circuit board system includes three types of interconnection: chip to circuit board, PCB circuit board interconnection, and signal input/output between PCB and external devices. This article mainly introduces a summary of practical techniques for high-frequency PCB board design with interconnections within the PCB board. I believe that understanding this article will bring convenience to future PCB design.

What are some practical skills in high-frequency PCB design
In PCB design, the chip-PCB interconnection is important to the design. However, the main problem of the chip-PCB interconnection is that the interconnection density is too high, which will cause the basic structure of the PCB material to become a factor limiting the growth of interconnection density. This article shares practical tips for high-frequency PCB design.
As far as high-frequency applications are concerned, the techniques for high-frequency PCB design with interconnections within the PCB are as follows:
1. The corner of the transmission line should be 45° to reduce the return loss;
2. Use high-performance insulated circuit boards whose insulation constant values are strictly controlled by level. This method is conducive to effective management of the electromagnetic field between the insulating material and the adjacent wiring.
3. To improve the PCB design specifications related to high-precision etching. It is necessary to consider that the total error of the specified line width is +/-0.0007 inches, the undercut and cross-section of the wiring shape should be managed, and the plating conditions of the wiring side wall should be specified. The overall management of wiring (wire) geometry and coating surface is very important to solve the skin effect problem related to microwave frequency and realize these specifications.
4. The protruding leads have tap inductance, so avoid using components with leads. In high frequency environments, it is best to use surface mount components.
5. For signal vias, avoid using via processing (pth) processes on sensitive boards. Because this process will lead to lead inductance at the via. For example, when a via on a 20-layer board is used to connect layers 1 to 3, the lead inductance can affect layers 4 to 19.
6. Provide abundant ground planes. Use molded holes to connect these ground planes to prevent the 3D electromagnetic field from affecting high-frequency circuit boards.
7. To choose electroless nickel plating or immersion gold plating process, do not use HASL method for electroplating. This kind of electroplated surface can provide better skin effect for high frequency current. In addition, this highly solderable coating requires fewer leads, which helps reduce environmental pollution.
8. The solder mask can prevent the flow of solder paste. However, due to the uncertainty of the thickness and the unknown of the insulation performance, the entire surface of the board is covered with solder mask material, which will cause a large change in the electromagnetic energy in the microstrip design. Generally, a solder dam (solderdam) is used as the solder mask.