The PCB is designed to be smaller, faster and cheaper.As the interconnection point is the weakest link in the circuit chain, in RF design, the electromagnetic property of the interconnection point is the main problem faced by engineering design. It is necessary to investigate each interconnection point and solve the existing problems.
The interconnection of the circuit board system includes three types of interconnection, namely chip to circuit board, interconnection within PCB board and signal input/output between PCB and external device.This paper mainly introduces the practical skills of high frequency PCB design for interconnection in PCB board, and I believe this paper will bring convenience to future PCB design.
The interconnection between chip and PCB in PCB design is important for design. However, the main problem of interconnection between chip and PCB is that too high interconnection density will lead to the basic structure of PCB material becoming the factor limiting the growth of interconnection density.This article shares practical tips for designing high frequency PCB.
For high frequency applications, PCB interconnection for high frequency PCB design techniques are:
1, the transmission line to the corner a 45 ° Angle, in order to reduce return loss;
2. High performance insulation board with strict control of insulation constant values should be adopted.This method can effectively manage the electromagnetic field between the insulation material and the adjacent wiring.
3. Perfect PCB design specifications for high-precision etching.Consider setting the total line width error to +/-0.0007 inches, managing undercuts and cross-sections of wiring shapes, and specifying lining plating conditions.The overall management of the wiring geometry and coating surface is very important for solving the skin effect problems related to microwave frequency and realizing these specifications.
4. There is tap inductance for protruding leads, and the components with leads should be avoided.In high frequency environments, it is best to use surface mount components.
5. For the signal via hole, it is necessary to avoid using the process of via hole processing (PTH) on the sensitive plate.Because this process will lead to lead inductance through the hole.A lead inductance can affect 4 to 19 layers if a through hole on a 20 - layer plate is used to connect 1 to 3 layers.
6. It should provide abundant ground.These layers are connected by moulded holes to prevent 3 - dimensional electromagnetic fields from affecting the circuit board.
7. Choose non-electrolytic nickel plating or dip plating process instead of HASL electroplating.This electroplating provides a better skin effect for high-frequency currents.In addition, this high solderable coating requires less lead, helping to reduce environmental pollution.
8. The resistance welding layer can prevent the flow of solder paste.However, due to the uncertainty of thickness and the uncertainty of insulation performance, the whole surface of the board is covered with resistance welding material, which will lead to great changes in electromagnetic energy in microstrip design.Solderdam is usually used as solder barrier layer.