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Material selection for PCB manufacturing

2019-08-23 16:38:13 459

PCB board manufacturing requirements for materials

In today's wireless communication devices, the radio frequency portion tends to adopt a miniaturized outdoor unit structure, while the radio frequency portion, the intermediate frequency portion of the outdoor unit, and the low frequency circuit portion that monitors the outdoor unit are often deployed on the same PCB board pair material. Therefore, there is a high demand for PCB material on how to prevent interference between RF, IF and low frequency circuits.


The circuit design of the hybrid circuit is a big problem and it is difficult to have a perfect solution. In general, the RF circuit is laid out as a separate board in the system, and even there is a special shielding cavity. Moreover, the RF circuit is generally single-sided or double-sided, and the circuit is relatively simple, all of which are designed to reduce the influence on the distribution parameters of the RF circuit and improve the consistency of the RF system. Compared with the general FR4 material, the RF circuit board tends to be a substrate with a high Q value. The dielectric constant of this material is relatively small, the transmission line distribution capacitance is small, the impedance is high, and the signal transmission delay is small.


In the hybrid circuit board design, although the RF and digital circuits are on the same PCB, they are generally divided into a RF circuit area and a digital circuit area, and are respectively arranged and routed. Shielded between grounded vias and shielded boxes.


Crosstalk interference is of particular concern in high-speed, high-density PCB designs because it has a large impact on timing and signal integrity.


Here are a few caveats:

Choose the appropriate termination method. The continuity and matching of the trace characteristic impedance control.


The size of the trace spacing of the board manufacturing. The spacing commonly seen is twice the line width. The simulation can be used to know the influence of the trace spacing on timing and signal integrity, and to find the minimum tolerance that can be tolerated. The results of different chip signals may vary.


Board manufacturing materials generally have FR-4, high frequency material (CCL), Rogers, HTG, MTG, NTG, HF and other plates.


Circuit board manufacturing is generally based on the customer's final product requirements, that is, what board is used for formal board production.

Therefore, the materials used in the manufacture of circuit boards are various.


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