Introduction For The Advantages Of Laying Copper In PCB

Usually, after we finish all the wiring work in the layout, the idle space on the PCB will be used as the datum surface for copper laying. This is common knowledge of almost all PCB engineers, but few have been able to say what it means. What are the advantages of laying copper in PCB? The answer might be:

1. There are a lot of peak pulse currents in digital circuits, and the interference energy of ground network U=I*R, so it is particularly important to reduce the ground impedance. A large part of the so-called anti-interference is achieved by reducing the ground impedance, so a large number of laying copper or a complete ground plane can reduce the ground impedance to enhance the system’s anti-interference ability.
2. For the power supply, the transmission path includes the power supply path and the backflow path. The voltage drop of the whole transmission path U=I*R, and the lower the DC resistance R on the path, the lower the voltage drop. Therefore, a large amount of copper laying can reduce the DC resistance on the power transmission path, thereby reducing its voltage drop and improving the transmission efficiency of the power supply.
3. For the backflow of the power supply, the ground wire is connected with the copper laying, which can maximize the power supply to find the shortest backflow path, thus reducing the area of the power loop and improving the anti-interference ability of the system.
4. Protect and isolate important signals and high-speed signals by paving the ground.
5. Copper skin is able to transmit heat, a large number of paving copper skin combined with the ground through the hole can greatly improve the system heat dissipation. The processing of chip hot pads is a good reflection of heat dissipation through copper and holes.

Theoretically, for digital systems, the more copper sheets are laid, the more favorable the effect on the impedance of the ground wire, DC resistance, power supply loop, heat dissipation, etc. However, often a multilayer plate will have more than one ground plane, these ground planes should be enough to meet these problems such as impedance, resistance, loop, heat dissipation, etc. Whether or not the copper in the spare area of the signal layer is laid?

In fact, the above meaning for laying copper is based on the consideration of electrical performance, from the point of view of the process,  to ensure the effect of electroplating, or lamination is not deformation, in the blank place of the line layer is also to lay copper.

The theoretical lamination thickness is calculated based on the residual copper rate of 100%. However, if the trace layer has less trace and no copper laying, the residual copper rate of the trace layer will be relatively small, and the final lamination thickness will deviate more from the theoretical thickness.

Therefore, in order not to deform the lamination or to make our theoretical calculation including impedance calculation and plate thickness calculation as close as possible to the actual value of the finished product, we should make the copper residue rate of the inner layer close to 100%. I’ll put the copper on the space.