Potentiometers, adjustable capacitors, key switches, adjustable inductors and other regulating devices are often used in the design of circuit boards. We may adjust these devices after designing the whole circuit board, Some devices such as keys may also become the opening keys of the circuit board. Therefore, when designing such devices, they should be placed on the edge of the circuit board or other easily accessible places.
When designing various USB interfaces, simulation downloader interfaces or other plug-in devices, such devices are usually arranged on the central axis of symmetry of the circuit board in order to prevent the irreparable risk of stress concentration on the circuit board.
Heat dissipation principle of high power devices
In the layout of the circuit board, if there are easy heating elements, these elements should be placed at the edge of the circuit board or in the area with few other components, and sometimes heat sinks should be added. At the same time, the temperature sensitive devices will be far away from the heating elements, so as not to affect the accuracy and stability of the system.
1. If there are analog circuits and digital circuits in the circuit at the same time, the two circuits shall be isolated by isolation devices and arranged in modular areas. 2. When there are both low-frequency circuit and high-frequency circuit in the circuit, isolate the high-frequency and low-frequency circuit on the basis of not affecting the high-frequency circuit. 3. When strong and weak electrical signals appear in the circuit, it is also necessary to isolate the two signals, such as optocoupler isolation and transformer isolation, so as to prevent the interference of strong current to weak current.
On the circuit board, there is often a circuit to prevent voltage track collapse, such as 10uF capacitor and 104 capacitor. The two devices should be close to the power port of the corresponding components. 2. Keep the connection between the two high-frequency devices as short as possible. 3. The EMI filter shall be kept as close as possible to the EMI source.
Aesthetic and manufacturability principles
Aesthetics means that the design of the whole circuit board should be kept properly dense, and the core controller is in the center, and the other sub circuits are evenly distributed around it. Manufacturability means that the designed circuit board should fully consider the processing capacity of the foundry, and the position of components should be appropriate and match with the shell during welding and assembly.
Principle of easy replaceability
The principle of easy replaceability usually refers to easy maintenance during later maintenance. Easy disassembly shall be considered for the layout of easily damaged devices such as crystal oscillator.
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Seven principles of device layout in circuit board design