In the PCB design, the interconnection of the chip and the PCB is important for the design. However, the main problem of the interconnection between the chip and the PCB 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 the 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 a via processing (pth) process on sensitive boards, because this process will cause lead inductance at the vias. 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. To provide a rich ground plane. Use molded holes to connect these ground planes to prevent the 3D electromagnetic field from affecting the circuit board.
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 is used as the solder mask.
The above are the techniques for high-frequency PCB design for the interconnection in the PCB board shared by you today. If you are familiar with these methods, you can understand that the back-side copper-clad coplanar microstrip design is more economical and practical than the stripline design.
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