Shielding Method in High Speed PCB Design

While the transmission rate of high-speed PCB fabrication design and wiring system is steadily accelerating, it also brings some anti-interference vulnerability. This is because the higher the frequency of transmitting information, the sensitivity of signals increases, and their energy becomes weaker and weaker at the same time. At this time, the wiring system is more susceptible to interference. Interference is everywhere. Cables and equipment will interfere with other components or be seriously interfered by other sources of interference, such as: computer screens, mobile phones, electric motors, radio relay equipment, data transmission and power cables, etc. In addition, potential eavesdroppers, cybercriminals, and hackers are on the rise, as their interception of UTP cable information transmissions can cause enormous damage and loss.

Especially when using high-speed data networks, the time required to intercept large amounts of information is significantly lower than the time required to intercept low-speed data transmissions. The twisted wire pairs in the data twisted pair can rely on their own twisting to resist external interference and crosstalk between the wire pairs at low frequencies, but at high frequencies (especially when the frequency exceeds 250MHz), only rely on Twisted wire pairs can no longer achieve the purpose of anti-interference, and only shielding can resist external interference.

The cable shield acts like a Faraday shield, allowing interference signals to enter the shield but not the conductor. Therefore, data transmission can run without problems. Because shielded cables have lower radiated emissions than unshielded cables, network transmissions are prevented from being intercepted. Shielded networks (shielded cables and components) can significantly reduce the level of electromagnetic energy radiation that enters the surrounding environment and may be intercepted.

Shielding options for different interference fields There are two main types of interference fields: electromagnetic interference and radio frequency interference. Electromagnetic interference (EMI) is primarily low-frequency interference, with motors, fluorescent lights, and power lines being common sources of EMI. Radio frequency interference (RFI) refers to radio frequency interference, mainly high frequency interference. Radio, television broadcast, radar, and other wireless communications are common sources of radio frequency interference. For resisting electromagnetic interference, braided shielding is the most effective because it has a lower critical resistance; for radio frequency interference, foil shielding is the most effective, because braided shielding depends on the change of wavelength, and the gap it produces makes high-frequency signals free Incoming and outgoing conductors; and for high and low frequency mixed interference fields, the combined shielding method of foil layer and braided mesh with broadband coverage function should be used. Generally, the higher the mesh shielding coverage, the better the shielding effect.

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