This article is part of the wiring diagram on the PCB experience, the paper mainly applies to high-precision analog systems or low frequency (<50MHz) digital systems.
1. Component layout
Component layout is reasonable to design a high-quality PCB diagram of the basic premise. The main requirements on the arrangement of components installed, force, heat, signals, six aesthetic requirements.
1.1 Installation
Refers to the specific application, in order to successfully install the circuit board into the chassis, shell, slot, space will not interfere, short circuit, and to specify the connector at the specified location on the chassis or housing put forward a series of basic requirements. Not repeat them here.
1.2 Force
Board should be able to withstand the installation and work suffered various external and vibration. To this end the board should have a reasonable shape, various hole plate (screw holes, Hole) position to make reasonable arrangements. General hole and edge distance at least greater than the diameter of the hole. Also note that the weakest section of the plate-shaped hole caused should also have sufficient bending strength. Board direct "stretched out" connector enclosure especially reasonable fixed, to ensure long-term reliability.
1.3 heat
For high-power, severe fever devices, in addition to ensure heat dissipation, but also pay attention to be placed in the appropriate location. Especially in precision analog systems, should pay particular attention to the adverse effects of these devices generate temperature field on the fragile preamp circuit. General power of a very large part should be made into a separate module, and to take certain measures and thermal isolation between the signal processing circuit.
1.4 Signal
The most important factor interfering signals in PCB layout to be considered. Several fundamental aspects: weak signal separation circuit and even strong signal circuit isolation; exchange part of the DC part separately; high frequency part and low frequency part separately; attention to the signal line; ground arrangement; proper shielding, filtering and other measures. These are a large number of treatises repeatedly stressed before, not repeated here.
1.5. Appearance
Only to consider the orderly placement of components, but also to consider graceful traces. As the general layman sometimes more emphasis on the former, in order to design a one-sided evaluation of the merits of the circuit, in order to the image of the product, while not demanding performance requirements to give priority to the former. However, in the case of high-performance, dual panel if you have to, but the board also encapsulated inside, usually invisible, priority should be given emphasis on aesthetics traces. The next section will discuss specific wiring "aesthetic."
