PCB Tech - PCB impedance control technology

PCB impedance control technology, we must distinguish the two different concepts of wire resistance and impedance. Resistance refers to the impedance of the wire to the current in the DC state, and impedance refers to the impedance of the wire to the current in the AC state. This impedance is mainly caused by the inductance of the wire. Any wire has inductance. When the frequency is high, the impedance of the wire is much greater than the DC resistance.

PCB impedance technology is especially important in high speed PCB design. Impedance control technology includes the following two aspects:

The impedance control PCB signal line means that the impedance is continuous everywhere along the high speed PCB signal line, which means that the impedance on the same network is a constant.

The impedance control PCB board means that the impedance of all networks on the PCB board is controlled within a certain range, such as 40 120Ω.

Design engineers need to use transmission line theory or use EDA tools to achieve impedance control. The IPCB processing plant relies on advanced technology and high performance instruments and testing techniques to ensure the accuracy of impedance control technology. Therefore, the IPCB factory may need to change the size and spacing in the design to achieve impedance control. IPCB factory can provide 2 40 layer high speed impedance board simulation design.

Analysis and measurement are a very important part of impedance control technology, and light board testing is especially important and accurate. Therefore, PCB design engineers must formulate the impedance of key signal lines and allowable errors in the design, and closely coordinate the work of the IPCB processing plant to ensure compliance with all design specifications.

There are many PCB signal technologies for impedance control: embedded microstrip line, asymmetrical stripline, symmetrical stripline, edge coupled coated microstrip line, edge coupled asymmetrical stripline, radiation coupled stripline Wait. From the perspective of the circuit and PCB design engineer, it is necessary to strictly calculate the impedance according to the system design requirements, control the geometric size of the signal line, and control the impedance and error requirements of the signal line with these key impedances, and clearly submit it in the form of a document To the IPCB processing factory, and request the IPCB processing factory to submit a detailed report to achieve the processing test. For the specific requirements of design engineers, IPCB processing manufacturers usually add test card bars to the periphery of the PCB design puzzle, and use advanced test technology to adjust the geometric size and spacing of key signal lines according to the processing technology.