Power line and ground wire processing technology in PCB
In the PCB layout, the handling of the power and ground wires is very important. The noise interference generated by the power cables and ground wires should be minimized to ensure the quality of the products.
The wiring rules for the power and ground wires are as follows.
· Add a decoupling capacitor between the power supply and ground.
· Try to widen the power line and ground line width. It is better to make the ground line wider than the power line.
· The PCB of a digital circuit can be formed into a loop by using a wide ground wire, that is, a ground net is used, and the ground of the analog circuit cannot be used in this way.
· Use a large area of copper as the ground wire, connect the unused area on the printed board to the ground as a ground wire, or make a multi-layer board, each of which is occupied by a power supply and a ground wire.
After the wiring design is completed, it is necessary to carefully check whether the wiring design meets the rules set by the designer, and also to confirm whether the established rules meet the requirements of the printed board production process, and generally check the following aspects.
· Whether the distance between the wire and the wire, the wire and the component pad, the wire and the through hole, the component pad and the through hole, the through hole and the through hole are reasonable, and whether the production requirement is satisfied.
· Is the width of the power and ground wires appropriate? Is there a tight coupling between the power supply and the ground (low wave impedance)? Is there a place in the PCB that allows the ground to be widened?
· Whether the best measures are taken for the critical signal line, such as the shortest length, the added protection line, the input line and the output line are clearly separated.
· Whether the analog circuit and the digital circuit part have separate ground lines.
· Whether the graphics (such as icons, markers) added to the PCB will cause a signal short circuit.
· Modify some ideal line shapes.
· Whether the process line is added on the PCB, whether the solder mask meets the requirements of the production process, whether the solder mask size is appropriate, and whether the character mark is pressed on the device pad.
· Whether the outer frame of the power supply ground in the multi-layer board is reduced, for example, the copper foil of the power supply ground layer is likely to cause a short circuit outside the exposed board.