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1. PCB wiring direction: from the soldering surface, the arrangement of the components should be consistent with the schematic diagram as much as possible, and the wiring direction should be consistent with the wiring direction of the circuit diagram.

2. The components are arranged and distributed reasonably and evenly, and strive to be neat, beautiful, and rigorous in structure.

3. Resistor, diode placement: divided into two types: horizontal and vertical

1) Flat placement: When the number of circuit components is not large, and the size of the circuit board is large, it is generally better to use flat placement; For the resistance below 1 4W, the distance between the two pads is generally 4 10 inches, and when the resistance of 1 2W is flat, the distance between the two pads is generally 5 10 inches; When the diode is placed flat, the 1N400X series rectifier tube is generally 3 10 inches; 1N540X series rectifier tube, generally take 4 5 10 inches.

2) Vertical: When the number of circuit components is large, and the size of the circuit board is not large, it is generally vertical, and the spacing between the two pads is generally 1 2 10 inches.

4 Potentiometer: the principle of placing the IC socket.

1) Potentiometer: It is used to adjust the output voltage in the voltage regulator, so the output voltage of the design potentiometer should increase when it is adjusted clockwise when it is full, and the output voltage decreases when the counterclockwise regulator is adjusted; In the adjustable constant current charger, the potentiometer is used to adjust the size of the charging current, and the current increases when the potentiometer is designed to be adjusted clockwise in the middle of the full.

The potentiometer should be placed on the edge of the board as much as possible, and the rotating handle should be facing outward.

2) IC seat: When designing the printing board diagram, in the case of using the IC seat, we must pay special attention to whether the orientation of the positioning groove on the IC seat is correct, and pay attention to whether the position of each IC pin is correct, for example, the first foot of the potato board can only be located in the lower right corner line or the upper left corner of the IC block, and the number of Linglet and close to the positioning groove (from the welding surface).

5 Arrangement of inlet and outlet terminals.

1) The distance between the two lead ends should not be too large, generally about 2 3 10 inches is more appropriate.

2) The inlet and outlet ends should be concentrated on 1 to 2 sides as much as possible, and should not be too discrete.

6. When designing the wiring diagram, pay attention to the order of the pins, and the spacing of the component pins should be reasonable.

7. On the premise of ensuring the performance requirements of the circuit, the design should strive to be reasonable, less external cross-wires, and according to certain shunchong requirements, and strive to be intuitive, easy to install, height and maintenance.

8. When designing the wiring diagram, the wiring should be routed with as few turns as possible, and the lines should be simple and clear.

9. The width of the wiring and the spacing of the lines should be moderate, and the spacing between the two pads of the capacitor should be consistent with the spacing of the capacitor leads as much as possible;

10. The design should be carried out in a certain sequential direction, for example, from left to right and from top to bottom.

Let's talk about it briefly;

Signal quality involves the flow direction of the signal, for the current is the need to form a loop to achieve, such as the transmission section of the signal, from the transmitting pin to the receiving pin is actually only one of the segments, and the receiving end through a certain path back to the transmitter to form a complete loop, and the loop may have a variety of options, but the current is to choose the path with low impedance, so the plane has become the best choice, so the ground plane needs to be well preserved, so many PCB designers understand how to divide the power layer, I also try not to move the ground plane, although many people don't know why.

That's why! I don't know if you understand.

The answer can be found in signal integrity and high-speed signals.

To put it simply, the power supply takes the path of least impedance, and the current takes the path of the least inductance. In PCB design, the reflow path of the current is changed due to the parasitic capacitance and parasitic inductance generated by the plane division, traces, vias, etc., and if there is a complete ground plane as a reference, the shortest path will be taken, thereby reducing crosstalk on the line. Otherwise, the long cable routing mode does not have a complete ground plane as a reference, because of the power supply noise and the influence of ground bombs, etc., the reference plane is inconsistent, which makes the crosstalk very large.

Controlling the impedance, generally to control the width of the trace (because the thickness has basically been determined, and the thickness of the plate and the number of layers are related), the trace layer and the adjacent stratum can get the spacing d, so the impedance matching control can play a good role.

Under normal circumstances, the key traces still need to have GND as a reference, and some other traces can be without. Consider cost and plate thickness, etc.