# Eight classic Q & A to explain PCB cabling (1)

Eight classic Q & A to explain clearly PCB cabling （1）

1.Q: the resistance of a very short copper wire in a small signal circuit must not be important, right?

A: the conductive tape of the printed PCB circuit board is made wider and the gain error will be reduced. In analog circuits, it is usually better to use a wider conductive band. But many PCB designers (and PCB design procedures) prefer to use a minimum width of conductive tape to facilitate the layout of signal lines. It is very important to calculate the resistance of the conductive tape and analyze its function.

2.Q: I have described the problem of simple resistance, there must be some resistors, its performance is completely in line with our expectations. May I ask what the resistance of a section of wire will be?

A: it's different. You're referring to a section of a conductor or a section of a PCB circuit board that acts as a conductor. Since room temperature superconductors have not yet been invented, So any piece of metal wire acts as a low resistance resistor (it also acts as a capacitor and inductor, so its effect on the circuit must be considered.

3.Q: is there a problem with the capacitance between the oversized conductive tape and the metal layer on the back of the printed circuit board?

A: the problem is small. Although the capacitance made up of the conductive tape of the printed circuit board is important, it should always be estimated first. If the above situation does not exist, Even if a wide conductive band forms a large capacitance, there will be no problem. If the problem arises, the area of a small grounding plane can be removed to reduce the capacitance to the ground.

4.Q: what is an electrical grounding plane?

A: if the entire side of a printed circuit board (or the entire interlayer of a multilayer printed circuit board) is used for grounding, So this is what we call the grounding plane. Any ground wire is arranged so that it has as little resistance and inductance as possible. If a system uses a grounding plane, So it is less likely to be affected by earthing noise, and the grounding plane has the function of shielding and heat dissipation.