It is recommended that beginners follow the following basic principles one by one while routing the PCB. After the wiring is completed, check it again with these rules.
1: The schematic diagram is based on the principle of convenient wiring and troubleshooting. The bus is used reasonably and the real pin distribution is used.
2: All the components of the raw device should be hand-made before the PCB is generated, and the triode package is prepared in advance.
3: Manual sketching should be done before wiring, and the layout should be roughly based on the principle of performance priority.
4: Do not parallel the axis of the component, carefully set the ground wire, and use the full or mesh copper.
5: The ground wire in the digital circuit should be netted, and the signal clock line should use the snake walking wire reasonably. The pad should be appropriate.
6: Manual wiring should be wired according to the network or components, and then the docking and arrangement between the blocks.
7: When the layout is urgently modified, it must be calm, generally only need to change individual components or one or two networks.
8: When making the PCB, leave at least five solder holes, four corners and center in the blank space for the hole.
9: It is best to brush the tin before soldering. The components are placed on the board and fixed with tape before soldering.
10: The ADC circuit traces should be separated from the traces of other digital circuits or signal lines (especially clocks). Parallel and traverse are strictly prohibited.
11: The oscillating crystal should be as short as possible and surrounded by the ground wire, but be careful not to increase the load capacitance due to the small spacing.
12: Single and double panels must have at least 50% metal layer, and the multilayer board has at least four metal layers to prevent local overheating and fire.
13: The signal line should be as thick and consistent as possible, and the ground line should be added between the signal line and the input and output lines.
14: When the device pins are in contact with the ground wire, it is better not to use a large area of copper. Instead of using a grid, the whole board is covered with copper to prevent skinning and mesh.
15: If there is a large area of copper on the PCB, it is necessary to open a small opening of less than 3. 5mm on the ground, which is equivalent to a grid.
16: In order to avoid over-length traces, jumpers should not be placed under the large components such as IC manifolds for easy plugging and unplugging.
17: The layout and wiring should fully consider the heat dissipation and ventilation of the device. The heat source should be close to the edge of the board and the distance between the test points should be designed.
18: In multilayer anti-electromagnetic interference design, 20H rule and 3W rule should be applied to overcome boundary radiation coupling and logic current flux interference.
19: It is better not to use the same parallel direction for the double signal line, and to control the minimum parallel length, such as JOG trace or sine and cosine trace.
20: The interference caused by the change of the upper and lower edges of the signal in the low-frequency line is much larger than the interference caused by the frequency, so pay attention to the crosstalk problem.
21: High-speed signal lines should be properly terminated, and it is best to keep their impedance constant during transmission and to maximize the width of the line.
22: Don't forget to add filtering and coupling capacitors between the power supply and ground of the integrated block to eliminate interference.
In the case of the increasing density of modern integrated devices, the layout of PCB layout directly affects the performance of the product, and even the key to the success of the design. As one electronic expert said: Ten devices may also have the possibility of numerous arrangements. But if there is a little error, its performance may be a hundred times apart!