Electronic Design - PCB design beginners need to pay attention to

PCB design is not an arbitrary thing, it has certain constraints and rules. As a beginner in PCB design, you should know the following precautions when your knowledge reserve and design experience are not enough!

Layout considers the whole

The success of a product depends on the internal quality and the overall aesthetics. Only when both are perfect can the product be considered successful.

On a PCB board, the layout of components must be balanced, dense and orderly, and not top-heavy or heavy.

Will the PCB be deformed?

Whether to reserve a craft edge?

Do you reserve MARK points?

Do you need to jigsaw?

How many layers of boards can guarantee impedance control, signal shielding, signal integrity, economy, and feasibility?

Avoid right-angle routing

When PCB routing, you should try to avoid right angles, acute angles and other phenomena. Generally, obtuse angles or arcs are used. As with the same layer, different layers should be wrapped as far as possible to avoid right angles and acute angles.

In PCB design, sharp angles and right angles should be avoided, unnecessary radiation is generated, and the process performance is not good.

The influence of right-angle routing on the signal is mainly reflected in three aspects:

One is that the corner can be equivalent to a capacitive load on the transmission line, which slows down the rise time;

2. the discontinuous impedance will cause signal reflection;

3. the EMI generated by the right-angle tip.

Power PCB layout and routing principles

When designing the power supply PCB, the following basic principles should be followed:

1. Choose the correct number of layers and copper thickness.

2. In the system design layout plan, the power circuit should be as close as possible to the load circuit. In particular, the power supply of the core processor should be as close as possible. If it is far away, transient response and line impedance may have problems.

3. The heat dissipation circuit should be as close as possible to the power circuit to reduce thermal resistance.

4. On the board with heat dissipation and convection, pay attention to the layout of large-sized passive devices (inductors, large capacitors), and do not obstruct the air convection between the chip and the MOSFET.

PCB package design considerations

Pay attention to the PCB package design: the pad center distance is equal to the pin center distance, and the direction of pin 1 should be consistent with the direction of pin 1 of the tray component during package design.

The silk screen cannot be covered by obscuration

The general requirements for silk screen design are as follows:

1. In order to ensure that all letters, numbers and symbols are easy to identify on the PCB, the line width of the silk screen must be greater than 5 mils, and the height of the silk screen should be at least 50 mils.

2. The silk screen is not allowed to overlap with the pad and the reference point.

3. White is the default silk screen ink color. If there are special requirements, it needs to be explained in the PCB drilling drawing file.

4. In high-density PCB design, the content of silk screen printing can be selected according to needs.

5. The arrangement direction of silk-screened strings is from left to right and from bottom to top.

Pay attention to later inspection

After the PCB wiring design is completed, it is necessary to carefully check whether the wiring design meets the rules formulated by the designer; at the same time, it is also necessary to confirm whether the rules formulated meet the requirements of the printed board production process. Generally check the lines and lines, line and component pads, Whether the distance between the line and the through hole, the component pad and the through hole, the through hole and the through hole is reasonable, whether it meets the production requirements, whether the width of the power line and the ground line is appropriate, whether there is a ground line in the PCB Wide place.