Fr4 Multilayer Impedance Control PCB

What is a controlled impedance?

High Quality Prototype PCB Fabrication and PCB design have undergone great changes in the past few years. The first cheap custom pcb fabrication and design are very simple, but new technologies have brought new performance requirements to the Characteristic impedance PCB world, design and custom The practice of circuit board cost manufacturing has become more complicated. One of these methods is controlled impedance in custom pcb fabrication, which aims to vary the amount of power in the circuit trace to the speed of the signal.
At low frequency (DC), the reactance becomes negligible, and the impedance is only formed by resistance, but for the high frequency board, reactance and impedance become very important factors.
What is controlled impedance
     Impedance mismatches in the system can cause malfunctions and reduce the performance level of the system. Ensuring that the impedance mismatch is within a tolerable range is a design feature commonly referred to as controlled impedance.
  Correspondingly, in the manufacturing of Characteristic impedance PCB, traces represent conductors, laminates represent insulators, and planes represent shields. Therefore, the impedance of the Characteristic impedance PCB depends on the size and materials used in the manufacturing process.
Why is controlling impedance so important?
     In the printed circuit board, the purpose of tracking is to transfer the maximum signal power from the source to the load, but this distribution can only be realized when the impedance value of the source matches the impedance value of the load, otherwise the energy of the signal will be reflected to the light source, reducing it quality. With today's fast rise time signals, circuit board designs with controllable impedance have become very popular.
How to do it?
     High Quality Prototype PCB Fabrication and impedance control in design are achieved in two ways: clearly defined PCB stacking and careful trace design. As we all know, impedance is proportional to the height of the laminate and inversely proportional to the width and thickness of the trace. Therefore, changing the size and spacing of a particular trace will adjust its impedance value.