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on October 24, 2023
Electrostatic protection design on the PCB using multilayer circuit boards, multilayer pcb fabrication can be divided into three levels of protection technology: components, circuit boards, system components.
First, component-level protection
Component-level protection is to prevent ESD coupled to the interference-sensitive circuits, commonly used transient suppression devices and filters used for protection.
The use of transient suppression devices mainly depends on the sensitivity, response voltage threshold, response time and several other major parameters: sensitivity determines whether the device is able to resist a certain degree of interference; response voltage threshold determines the device can play a protective ability of the circuit location; response time determines the protection effect, the shorter the response time, the better the protection effect.
Filtering device lies mainly in the two main links: frequency determines whether it can protect the protected circuit; placed in a position that determines the protective effect, the most conducive to the interference into the system before filtering it out, so that the placement of the system can be re-radiation of the internal.
Second, the circuit board level protection
In general, companies, multi-layer printed circuit boards have a fixed ground layer, so the ability to work on safety and protection is better than single- and double-layer boards, so that the ground layer as close as possible to the wiring layer, so that the arrangement of the students can be used by the use of ESD coupling to the low-impedance ground layer, you can get a significant impact on the reduction of ESD energy to reach the signal line. PCB factory Can refer to these rules of the following issues for instructional design:
1. Reduce the loop area, signal control line safety loop and power supply loop are required to be sure to pay attention to;.
2. Power supply layer and grounding layer arranged close to each other. This arrangement is more common, can play a good role in absorbing interference and suppressing radiation.
Minimize the length of the cable. Because there is a fixed ground layer and power layer in the multilayer board, so the placement of the device and wiring is relatively free, but also can reduce the high-frequency signal lines on the surrounding devices of radiation interference
4. Components with similar functions should be as close as possible. These devices are basically the same in terms of anti-interference, near the layout can be better focused and targeted protection and unified processing;
5. signal lines can be selected as close as possible to the ground wire, ground plane and corresponding to a circuit; and
6. Transient suppression devices for protection are connected directly to the enclosure ground as far as possible. This is because the electrostatic discharge can generate a large amount of current, the high current into the system ground can cause serious ground bounce, or even damage components.
7. PCB board stacking, connecting devices should leave enough ground pins. Adequate grounding pins can effectively reduce the ground impedance, reduce interference ditch current, maintain stable system operation.
Third, the system equipment level protection
For the entire device, when the internal components and PCB board is fixed, the protection of the entire system is particularly important. The following rules can be used in the design.
1, can be completely shielded from ESD radiation sensitive components and circuits, through the information shielding shell multi-point grounding can be absorbed by the students of the ESD current control to provide a low impedance channel. Can not really do the ice wall of the circuit requires us to carry out an effective insulation, so that the direct impact of discharge and radiation coupling have the existence of a certain protective effect;.
2. Connection cables inside the device should try to avoid keys, gaps, etc.. And place interference to affect the entire system;
3. For each input and output interfaces to increase the interference suppression protection device. Because these places can be directly contacted, often prone to static electricity, need to focus on protection. The protective devices are dependent on the interface only;
4. that the case connections of said maximizing devices are low impedance.
5. touch buttons require special treatment, placing contacts generated by static electricity directly on the sensitive digital circuit discharge;
6. connectors with housings made of different metal materials.
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