The general principles that designers need to follow in the layout of the board are as follows.
(1) the best single-sided components placed. If you need two-sided placement of components, in the bottom (Bottom Layer) placed pin-type components, it may cause the circuit board is not easy to place, is not conducive to welding, so the bottom (Bottom Layer) is best placed only patch components , Similar to the common computer graphics card PCB layout on the device. Single-sided placement only on one side of the circuit board to do silk screen layer, easy to reduce costs.
(2) reasonable arrangements for the location of the interface components and direction. general
For example, the connector components connected to the circuit board and the outside (power supply, signal lines) are usually arranged at the edges of the circuit board, such as serial and parallel ports. If placed in the center of the circuit board, obviously not conducive to wiring, there may be obstacles because of other components and can not connect. Also in the placement of the interface should pay attention to the direction of the interface, making the cable can be successfully led away from the circuit board. After the interface is installed, it should use the interface component String (string) clearly marked the type of interface; for the power interface, should be marked voltage level, to prevent wiring errors caused by circuit board burned.
(3) high-voltage components and low-voltage components between the best to have a wide electrical isolation zone. That is, do not put the voltage level difference between the components placed together, this is conducive to electrical insulation, the signal isolation and anti-interference is also a great advantage.
(4) electrical connections are closely related to the components are best placed together. This is the modular layout of the idea.
(5) For components that are prone to noise, high frequency devices such as clock generators and crystal oscillators should be placed as close as possible to the clock input of the CPU. High current circuit and switching circuit is also prone to noise, when the layout of these components or modules should also be away from the logic control circuit and storage circuit and other high-speed signal circuit, if possible, try to use the control panel combined with the power board, To connect to improve the overall anti-jamming capability and reliability of the circuit board.
(6) Place the decoupling capacitor and filter capacitor as much as possible around the power supply and the chip. Decoupling capacitors and filter capacitor layout is to improve the circuit board power quality, improve the anti-jamming capability of an important measure. In practice, the printed circuit board alignment, pin wiring and wiring are likely to bring more
Large parasitic inductance, resulting in high frequency ripple and glitch in the power waveform and signal waveform, and placing a 0.1 F decoupling capacitor between the power supply and ground can effectively filter out these high frequency ripples and glitches. If the circuit board is using a chip capacitor, the chip capacitor should be close to the power supply pin components. For power conversion chips, or power input, it is best to arrange a 10 F or larger capacitor to further improve the power quality.
(7) The number of components should be close to the components of the border layout, uniform size, neat direction, not with the components, vias and pads overlap. The first pin of the component or connector indicates the direction; the sign of the positive and negative terminals should be clearly marked on the PCB and are not allowed to be covered; the power conversion components (such as DC / DC converters, linear conversion power supplies and switching power supplies) There should be enough space next to the cooling space and installation space, leaving enough outside the welding space.
