The Principle of Impedance Interference of PCB Board

The Principle of Impedance Interference of PCB Board

Why does PCB board form impedance interference?

Because in the printed circuit board copy board manufacturing, the wire is generally copper wire, and copper the physical properties of this metal determines its conductive process must exist in a certain impedance, the inductance component in the wire will affect the voltage signal Of the transmission, the resistance component will affect the current signal transmission, in the high-frequency line inductance effect is particularly prominent.

In the printed circuit board on a section of wire can be seen as a regular rectangular copper, we have a long 10CM, wide 1. 5 mm, 50 microns thick wire, for example, by calculating the size of the impedance can be seen.

The wire resistance can be calculated by the formula:

R = ρL / s (Ω)

Where L is the length of the wire (m), s is the cross-sectional area of the conductor (mm), ρ is the resistivity ρ = 0. 02. It is calculated that the wire resistance is about zero. 026Ω.

The length of the conductor is 0 when the length of the conductor is far greater than the width of the conductor. 8μH / m, then 10 cm long wire with 0. 08μH inductance and then we can by the following formula to find out the copy board leads to the sense of resistance:

XL = 2πfL

Where π is a constant, f is the frequency (Hz) of the signal passing through the signal, and L is the self-inductance (H) of the length of the conductor. Which we can calculate the wire in the low frequency and high frequency of the sense of resistance:

When F = 10KHz, XL = 6. 28 × 10 × 103 × 0. 08 × 10-6 ≈ 0. 005Ω;

When F = 30MHz, XL = 6. 28 × 30 × 106 × 0. 08 × 10-6 ≈ 16Ω

Through the above formula we can calculate that in the low-frequency signal transmission wire resistance is greater than the wire inductance, and in the high-frequency signal in the wire inductance is much greater than the wire resistance.