PCB Technical - Design skills of high frequency circuit board

Design skills of high frequency circuit board

1. Improve the PCB design specification for high precision etching. Consider specifying a total line width error of + / - 0.0007 inches, managing undercut and cross sections of wiring shapes, and specifying plating conditions for wiring side walls. The overall management of wiring (conductor) geometry and coating surface is important to solve the skin effect problem related to microwave frequency and realize these specifications.

2. Protruding leads have tapped inductors, avoid using components with leads. In high frequency environments, surface mount components are preferred.

3. 45 ° angle should be adopted at the corner of transmission line to reduce back loss.

4. The high performance insulation circuit board with insulation constant value strictly controlled by layers is used to manage the electromagnetic field between insulation material and adjacent wiring.

5. Choose non electrolytic nickel plating or gold immersion plating process, do not use HASL method for electroplating. The electroplated surface can provide better skin effect for high frequency current. In addition, the high solderability coating requires less leads, which helps to reduce environmental pollution.

6. The solder mask prevents solder paste from flowing. However, due to the uncertainty of the thickness and the unknown insulation properties, the whole board surface is covered with solder mask, which will lead to a great change of electromagnetic energy in microstrip design. Generally, the solder dam is used as the solder mask. The electromagnetic field. In this case, we manage the transition from microstrip to coaxial cable. In a coaxial cable, the ground wire layers are circular and evenly spaced. In microstrip, the ground plane is below the active line. This introduces some edge effects, which need to be understood, predicted and considered in the design. Of course, this mismatch will also lead to back loss, which must be minimized to avoid noise and signal interference.

7. For signal vias, avoid using the via processing (PTH) process on the sensitive board, because this process will lead to lead inductance at the via.

8. Provide rich grounding layers, which are connected by moulded holes to prevent the influence of 3D electromagnetic field on the circuit board