​Design engineer explains the first part of high-quality PCB design

The circuit board manufacturer explained part of the experience summary on pcb diagram wiring, and the content in this paper is mainly applicable to high-precision analog systems or low-frequency digital systems.

This paper is a part of experience summary about pcb diagram wiring, which is mainly applicable to high-precision analog systems or low-frequency (<50 mhz) digital systems.

1. Layout of components

Reasonable component layout is the basic premise to design a high-quality pcb diagram. Requirements for component layout mainly include installation, stress, heating, signal and aesthetics.

1.1 Signal

Signal interference is the most important factor in pcb layout design. Several basic aspects are: weak signal circuit and strong signal circuit are separated or even isolated; The AC part is separated from the DC part; The high frequency part is separated from the low frequency part; Pay attention to the direction of the signal line; Layout of ground wire; Appropriate shielding, filtering and other measures. These have been repeatedly emphasized by a large number of scholars, and will not be repeated here.

1.2. Heating

For high-power devices with severe heat generation, in addition to ensuring heat dissipation conditions, attention should be paid to placing them in proper positions. Especially in the precise analog system, we should pay special attention to the adverse effects of the temperature field generated by these devices on the fragile preamplifier circuit. Generally, the part with very large power shall be made into a module separately, and certain thermal isolation measures shall be taken between it and the signal processing circuit.

1.3. Installation

It refers to a series of basic requirements put forward in specific applications to install the circuit board into the chassis, shell and slot smoothly, avoid space interference, short circuit and other accidents, and make the designated connector in the designated position on the chassis or shell. I will not repeat it here.

1.4. Force

The circuit board shall be able to withstand various external forces and vibrations during installation and operation. For this reason, the circuit board should have a reasonable shape, and the positions of various holes (screw holes, special-shaped holes) on the board should be reasonably arranged. Generally, the distance between the hole and the plate edge shall be at least greater than the diameter of the hole. At the same time, it should be noted that the weakest section of the plate caused by profiled holes should also have sufficient bending strength. The connectors on the board that directly "extend" out of the equipment shell shall be reasonably fixed to ensure the reliability of long-term use.

1.5. Aesthetic

Not only the orderly placement of components, but also the graceful and smooth routing should be considered. Since ordinary laymen sometimes emphasize the former to one-sided evaluate the advantages and disadvantages of circuit design, for the sake of product image, the former should be given priority when the performance requirements are not harsh. However, in high-performance occasions, if you have to use double-sided boards, and the circuit board is also packaged in it, you should give priority to the aesthetics of wiring. The next section will specifically discuss the "aesthetics" of cabling. The circuit board assembly and circuit board processing manufacturers explain some experience summary about pcb diagram wiring. The contents in this paper are mainly applicable to high-precision analog systems or low-frequency digital systems.