PCB design goals are smaller, faster and lower cost. And because the interconnection point is the weakest link in the circuit chain. In the RF design, the electromagnetic property at the interconnection point is the main problem facing the engineering design, and it is necessary to examine each interconnection point and solve the existing problems. The interconnection of circuit board systems includes three types of interconnects such as chip-to-board, PCB interconnect, and signal input / output between the PCB and external devices. This paper mainly introduces the practical techniques of high-frequency PCB design in PCB board interconnection, and it is believed that this paper will facilitate the future PCB design.
PCB design and chip interconnection in the PCB design is important, but the chip and PCB interconnection of the most important problem is the high density of interconnect will lead to the basic structure of the PCB material to limit the density of interconnection factors. This article shares the practical techniques of high frequency PCB design.
In terms of high-frequency applications, PCB board interconnection for high-frequency PCB design techniques are:
1, the transmission line corner to use 45 ° angle to reduce the return loss;
2, to use the insulation constant value strictly controlled by the level of high-performance insulation circuit board. This method is advantageous for the effective management of the electromagnetic field between the insulating material and the adjacent wiring.
3, to improve the high-precision etching of the PCB design specifications. Consider the specified line width total error of +/- 0.0007 inches, manage the undercut and cross section of the wiring shape and specify the wiring sidewall plating conditions. The overall management of the wiring (wire) geometry and the coating surface is important to address the skin effect associated with microwave frequencies and to implement these specifications.
4, highlight the existence of tap wire lead, to avoid the use of lead components. In high frequency environments, it is best to use surface mount components.
5. For signal vias, avoid using the via process (pth) on the sensitive plate, as this process results in lead inductance at the vias. If a vias on a 20-layer board are used to connect 1 to 3 layers, the lead inductance can affect layers 4 to 19.
6, to provide a rich ground layer. These ground layers are to be connected using molded holes to prevent the effect of 3-dimensional electromagnetic fields on the circuit board.
7, to choose non-electrolytic nickel plating or gold plating process, do not use HASL method for plating. This type of plating surface can provide a better skin effect for high frequency current. In addition, this high solderable coating requires fewer leads and helps reduce environmental pollution.
8, solder mask layer to prevent the flow of solder paste. However, due to the thickness of the uncertainty and the insulation properties of the unknown, the entire surface of the board are covered with solder mask material will lead to microstrip design of the electromagnetic energy in the larger changes. Generally use solder dam (solderdam) as a solder mask.
The above is for everyone to share the PCB board interconnection high-frequency PCB design techniques, if you are familiar with these methods, you can understand the use of the back of the copper coplanar microstrip design than the strip line design more economical and practical.