- Jul 25, 2017 -
Multi - layer PCB circuit board layout and routing principles
Multi-layer PCB circuit board layout and wiring of the general principles of PCB designers in the circuit board wiring process to follow the general principles are as follows:
(1) The principle of setting the spacing of the printed wiring of the components. The spacing between different networks is the principle of setting the spacing of the printed wiring of the components by electrical insulation, fabrication processes and components. Size and other factors. For example, if the pin spacing of a chip component is 8mil, the chip's ClearanceConstraint can not be set to 10mil. The PCB designer needs to set up a 6mil PCB design rule for the chip. At the same time, the spacing of the set also take into account the manufacturer's production capacity.
In addition, the impact of components is an important factor in electrical insulation, if the two components or network potential difference is large, we need to consider the electrical insulation problem. The general environment of the gap safe voltage of 200V / mm, which is 5.08V / mil. So when the same piece of circuit board so that when the same circuit board on both high-voltage circuit and low-voltage circuit, you need to pay special attention to adequate safety spacing. There are high-voltage circuit and low-voltage circuit, you need to pay special attention to adequate safety spacing.
(2) the choice of line corner traces. In order to make the circuit board easy to manufacture and beautiful, in the PCB design need to set the corner of the line mode, the choice of the direction of the line corner. You can select 45 °, 90 ° and arc. PCB Generally do not use sharp corners, it is best to use a circular transition or 45 ° transition, to avoid the use of 90 ° or more sharp corner transition.
The connection between the wire and the pad should be as smooth as possible to avoid a small tip, you can use the method to solve the tears. When the center distance between the pads is less than the outer diameter D of one pad, the width of the wire may be the same as the diameter of the pad; if the center distance between the pads is greater than D, the width of the wire should not be greater than the pad diameter. When the wires pass between the two pads and do not communicate with them, they should be kept at the maximum and equal spacing, and the wires of the wires and wires pass through the two pads without being connected to them. And the spacing between the same, the spacing should also be equal and maintain the maximum. The spacing should also be equal and maintain the maximum.
(3) method of determining the width of the printed wiring. The width of the trace is determined by the current level and anti-jamming of the conductor. PCB The greater the current through the current, the wider the trace should be. The power cord should be wider than the signal line. In order to ensure the stability of the ground potential (by the ground current size of the larger flow, the alignment should be wider.General power line should be more than the signal line width of the power line should be greater than the signal line widening effect), ground should also be more Wide ground should also be wide. Experiments show that: when the printed wire copper film thickness of 0.05mm, the printed wire load current should also be wider according to 20A / mm2 calculation, that is 0.05mm thick, 1mm wide wire can flow through the 1A Current. So the general width for the general can meet the requirements; high voltage high voltage, signal line 10 ~ 30mil width can meet the requirements of the high voltage, high current signal line width is greater than or equal to 40mil, Line spacing greater than 30mil. PCB In order to ensure the anti-stripping strength and reliability of the wire, within the allowable range of board area and density, the wideest wire should be used to reduce the line impedance and improve the anti-jamming performance.