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:
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.
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