1. How to deal with PCB sensitive circuit
(1) the power cord
According to the size of printed circuit board current, as far as possible to thicken the power line width, reduce loop resistance. In particular, we should pay attention to the power supply direction in the power line and ground line, which is opposite to the transmission direction of data and signals, that is, the power supply mode that pushes forward from the final stage is helpful to enhance the anti-noise ability
(2) the ground
The principle of design is) to separate digital from analog. If there are both logic and linear circuits on the circuit board, keep them as separate as possible. The ground of the low-frequency circuit should be grounded in parallel with a single point as far as possible. High frequency circuit should use multi-point series grounding, ground wire should be short and rent, high frequency components around the use of large areas of grid foil. The grounding wire should be thickened as much as possible. If the grounding wire is very flexible, the grounding potential changes with the change of current, so that the anti-noise performance is reduced. Therefore, the grounding wire should be thickened so that it can pass three times the allowable current on the printed board. If possible, the grounding wire should be above 2 ~ 3mm. The ground wire forms a closed loop. Printed circuit board is composed of only digital circuit, and its grounding circuit is arranged into a cluster loop, which can improve the anti-noise ability.
2. What interference elements are there in PCB
The source refers to the component, device or signal that produces interference, which is described in mathematical language as follows: du/dt, where di/dt is large, is the source of interference. If: thunder and lightning, relay, SCR, motor, high frequency clock can become interference source. Propagation path refers to the path or medium through which interference propagates from the source of interference to the sensitive device. The typical interference transmission path is the conduction through the wire and radiation in space. Sensitive components refer to objects that are easily disturbed. Such as: A/D, D/A converter, SCM, digital IC, weak signal amplifier.
3. It can be divided into radiation and conduction interference
A radiative interference is an interference source that USES space as a medium to jam its signal into another electrical network. Conduction interference refers to the interference of signals from one electrical network to another by using conductive media as media. In high-speed system design, integrated circuit pins, high-frequency signal lines and various connectors are common radiation interference sources in PCB board design. The electromagnetic wave emitted by them is electromagnetic interference (EMI), which will affect the normal operation of themselves and other systems. Baineng is a leading electronic industry service platform in China, which is subordinate to qinji group. It provides online solutions of electronic industry supply chain, such as components, sensor procurement, PCB customization, BOM order matching, material selection, etc., to meet the comprehensive needs of small and medium-sized customers in the electronic industry in one stop.
4. How to deal with sensitive components in PCB
Components should be placed in accordance with the production and maintenance convenience. Capacitance polarity should be consistent. Heating components and sensitive components to be placed apart from the distance. Wet sensitive components tend to be encapsulated in tape-and-reel systems, with each reel containing a large number of components. When compared to pin components in IC trays, the key issue is longer exposure to moisture. Exposure time must be increased to dry storage time during setup and treatment.