Impedance Controlled PCB Boards

Dated:2017-10-13      Popularity:1247

Printed Circuit Board

To understand the impedance controlled PCB better, you need to briefly know what the impedance is and how it affects the circuit.

The impedance is the effective resistance of the circuit to the alternating current caused by the combined effect of resistance and reactance. The transmission line is used for signal transmission in the PCB, and its impedance depends on the length and width of the line and the insulating substrate material called the substrate.

In the case of a DC circuit, the impedance is negligible, only the ohmic resistance is considered. However, in the AC circuit, the inherent capacitance and inductance of the conductor in the circuit are considered to correspond to the abrupt changes in voltage and current. As a result, signal delivery may present some critical issues. The efficiency of power transmission and signal integrity will be affected by changes in the impedance of the transmission line from the transmitter to the receiver.

Now that we understand the impedance and its effect on the PCB, we are close to the impedance controlled PCB. The impedance of the transmitter to the receiver in the transmission line is the sum of the output impedance of the transmitter, the input impedance of the receiver, and the impedance of the transmission line itself. The trace acts as a higher frequency transmission line.

In impedance controlled PCBs, the impedance values are controlled within an acceptable impedance range (tolerance). The design considerations for required tolerances are signal strength, circuit frequency, and signal timing. Once the required tolerance is found, tolerance of our truce is calculated by softwares like Microstrip by providing dielectric constant (Er) and height (H) of the substrate along with the thickness (T), spacing between traces (S) and width (W) of the trace. For materials with some variations, the dielectric constants are approximately the same, and the other parameters will be adjusted to achieve the required tolerances. After using these parameters to manufacture PCB, it is tested for tolerance and required adjustments are made accordingly.

EPCB is a UL certified company and we provide impedance controlled PCB as per the client requirements. Feel free to contact us for any query or requirements for PCB prototype and bulk PCB fabrication

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