PCB Technical - Briefly describe what principles should be followed when making PCB circuit boards

Briefly describe what principles should be followed when making PCB circuit boards

When the schematic diagram is drawn and ready to be printed into a PCB circuit board, certain principles should be followed in the layout of the circuit board. The circuit board layout is not arbitrary. In addition to considering interference, the length of the line and the size of the board are particularly important.

When making a PCB circuit board, the size of the PCB board must first be considered. Assuming that the PCB board size is too large and the circuit layout is too long when converting the PCB board, the impedance will increase, the anti-noise ability will be reduced, and the production cost will eventually increase; if it is too small, it will lead to poor heat dissipation and the components It is easy to interfere with each other. Before the schematic diagram is made into a PCB board, the board size must be determined first, and then the location of the special components must be determined. Finally, according to the functional units of the circuit, all the components of the circuit are laid out.

When we determine the location of special components, we need to follow some principles:

The lines between high-frequency components are as short as possible to reduce distribution parameters and mutual electromagnetic interference. Two components that are easy to interfere with each other should be far away, and the input and output components should not be too close. Components or wires with large potential differences can be increased in distance to avoid accidental short circuits caused by discharge. High-voltage components should be placed in places that are not easily touched by hands during debugging.

If the weight of the component exceeds 15g, then the bracket should be mounted before welding. The bulky and heat-generating components are best installed on the chassis floor of the complete machine, rather than on the circuit board., Under the same heat dissipation problem, the thermal element should be far away from the heating element. Regarding the distribution of adjustable components such as potentiometers, inductance coils, capacitors, and micro switches, the requirements of the whole machine must be taken into consideration.

The printing process needs to reserve the bracket and board positioning holes in advance. When the PCB circuit board components are laid out, they should conform to the anti-interference design. According to the circuit process, arrange the positions of the various functional components to ensure that the signal flow and direction are as consistent as possible after the layout.

During the layout, the core components should be the center of the spread layout. When arranged, they are neat and tidy, and the leads and connections of the components are as short as possible. Circuits in high-frequency environments should consider the distribution parameters between components. General circuits should be arranged in parallel as much as possible, in addition to being beautiful, it is also convenient for soldering and production.

The margin between the edge components of the PCB circuit board is not less than 2mm. Under normal circumstances, a rectangle is the best shape for a circuit board, with an aspect ratio of 3:2 or 4:3. When the size of the printed circuit board is >200*150mm, this is the mechanical strength of the PCB board. Of course, the above are only relatively common and need to pay attention to issues. There are still many things that need to be paid attention to before PCB production, which needs to be accumulated through continuous practice, and industrial boards should pay more attention to details.