With the rapid development of electronic technology, printed circuit boards are widely used in various fields, almost all electronic devices are included in the respective printed circuit boards. To ensure the normal operation of electronic equipment, to reduce electromagnetic interference between each other, reduce the adverse effects of electromagnetic pollution on human and ecological environment, electromagnetic compatibility design can not be ignored. This article describes the design methods and techniques of printed circuit boards.
In the printed circuit board design, layout and circuit wiring components are connected to two key aspects. [1]
layout

Layout, the circuit device is placed on the printed circuit board layout area. Whether the layout is reasonable not only affects the back of the wiring work, but also has an important impact on the performance of the entire board. To ensure circuit functionality and performance after, to meet manufacturability, testing and maintenance requirements, elements should be uniform, neat, compact cloth on the PCB, minimize and shorten the leads and connections between the various components in order to obtain uniform packing density.
Process according to circuit arrangements each functional circuit units position, input and output signals, high and low cross-section as much as possible, signaling the shortest route.
Functional distinction

Position components shall supply voltage, digital and analog circuits, speed, speed, current size grouping, in order to avoid mutual interference.
When the circuit board installed digital and analog circuits, ground, and power supply system completely separate the two circuits, when conditions will be digital and analog circuit arranged in different layers. The board needs to be laid quickly, while medium-speed and low-speed logic circuit, should be placed within close range of connectors; and the low-speed logic and memory, should be placed away from the connector within range. This will help reduce the common impedance coupling, radiation and reduce crosstalk. Clock circuits and high-frequency circuits are the main source of radiation harassment must be separate arrangements, away from sensitive circuitry.