The forming principle of PCB factory, circuit board lead impedance interference

In PCB factory at present the manufacture of PCB copy board, wire to wire, the physical properties of copper itself determines that it must exist in the process of conducting certain impedance, lead the inductance component affects the transmission of voltage signal, the resistance components will affect the current signal transmission, the influence of high frequency circuit inductance is particularly prominent. On the printed circuit board for a wire can be regarded as very regular rectangular copper bar, we take a long 10 cm wide, 1. 5 mm, thickness of 50 microns wires, for example, can be seen by calculating the size of the impedance. Conductor resistance can be calculated by formula: R = rho L/s ( Ω) Type of L for the wire length ( M. ) S for the conductor cross-sectional area ( Square millimeters) Rho for resistivity rho = 0. 02. Calculated the conductor resistance is about 0. 026Ω。 When a away from other conductor wire, its length is greater than the width, the self inductance of the wire is 0. Eight mu H/m, 10 cm long wire is 0. 08 mu H inductance. Then can be calculated with the formulas below the PCB factory copy plate conductor is presented by the impedance: XL = 2 PI PI for constant fL type, for wire through the signal frequency (f Hz) And for the self inductance per unit length of wires (L H) 。 So we can respectively calculate the wire under the low frequency and high frequency impedance: when f = 10 KHZ, XL = 6. 28×10×103×0. 08×10- 6≈0. 005Ω; When f = 30 MHZ, XL = 6. 28×30×106×0. 08×10- June 16 Ω material by the above formula calculation we can see that in low frequency signal transmission wire resistance is greater than the line impedance, and in the high frequency signal conductor inductance is far greater than the wire resistance. Rocket PCB as a professional supplier of PCB circuit boards, focus on high-precision double-sided/multi-layer circuit board, HDI board, thick copper, blind hole buried plate proofing and small batch, high frequency circuit boards and PCB board production.
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