How Can 2-layer PCB Board Be Designed Well?
Ⅰ. The 2 layer PCB design and wiring principles
The 2 layer board ground wire is designed to form a grid-like enclosure, that is, more parallel ground wires are laid on one side of the printed board, and the other side is the vertical ground wire of the copy board, and then they are connected by metalized vias at their intersections ( The via resistance should be small).
Considering that there should be a ground wire near each IC chip, one ground wire is often laid out every 1-115cm. Such dense ground wires make the area of the signal loop smaller, which is beneficial to reduce radiation. The ground network design method should be before the signal line, otherwise it will be difficult to implement.
Ⅱ. The operation steps of 2 layer PCB design
1. Prepare the schematic diagram of the circuit;
2. Create a new PCB file and load the component package library;
3. Plan the circuit board;
4. Load the network table and components;
5. Automatic layout of components;
6. Layout adjustment;
7. Network density analysis;
8. Wiring rule setting;
9. Automatic wiring;
10. Adjust the wiring manually.
Ⅲ. 2 layer PCB design experience (embedded hardware experience)
1. The clearance pitch is generally at least 10 mils, and at least 5 mils for high-density wiring;
2. The wire coming out of the soldering socket should be routed at least 10mil before changing its direction. Don't go out obliquely, it will produce sharp angles and be unsightly;
3. The vias of the main power line (the current is relatively large) adopt a double-hole parallel method to prevent a via failure circuit from not working;
4. The power inlet capacitor adopts 100uf and 104 ceramic method, and the outlet capacitor capacity must be large enough to meet the circuit requirements (the voltage will not be pulled down instantaneously when the current is large). The closer the shutdown diode is to the output pin of the power chip, the better;
5. The resistance and capacitance of the power supply part of 2 layer PCB board design must be calculated for power, and the package must meet the power requirements;
6. With multiple radio frequency circuits, radio frequencies can be cross-distributed on different layers to reduce interference;
7. Pay attention to the position of the lead wire and meet the schematic diagram. It can not be led out at any position with the same signal;
8. When wiring signal lines with the same characteristics, the signal characteristics should be the same, the wiring distance should be the same as much as possible, and the number of vias should be the same;
9. The decoupling capacitors and filter capacitors of some power supplies can be placed on the reverse side of the pins, saving space and shortening the wiring distance;
10. The wiring of 2 layer PCB design adopts longitude and latitude wiring, and the upper and lower layers are clear, which can also reduce vias and interference;
11. When drawing the schematic diagram, it is necessary to strictly calculate the rated current and rated power of the power chip to meet the actual load requirements;
12. When wiring, put in-line components around, not in the core wiring area, as this will cause interleaving and affect the longitude and weft routing. Prevent interpenetration, because the welding layer of the circuit may be scratched during welding, so that the welding pins may be stuck;
13. It is forbidden to lay copper under the network chip of 2 layer PCB design;
14. The crystal oscillator is rigorously anti-drop during welding, because excessive vibration will affect its performance;
15. The four corners of the board are best to be rounded to prevent scratches.