What is Board Level RF Shielding?

Board-Level Shielding (BLS) is a technique used to protect sensitive electronic components on a printed circuit board (PCB) from electromagnetic interference (EMI) and radio frequency interference (RFI). Board Level Shielding works by enclosing specific areas of the PCB with a conductive shield, usually made from metal, that acts as a barrier to block or contain electromagnetic radiation.

How does Board-Level Shielding Work? 

Board Level Shielding operates on the principle of the Faraday cage, which is a conductive enclosure that blocks external electric fields. When electromagnetic waves encounter the metal shield, the electrons in the conductive material rearrange themselves to cancel out the incoming fields. This prevents the external electromagnetic waves from penetrating the shielded area and affecting the components inside. 

The shield reflects most of the incoming electromagnetic waves due to the conductive properties of the metal. Some of the energy that passes through the shield is absorbed by the material itself, which further reduces the amount of interference that reaches the components inside. The effectiveness of the shield depends on factors such as the material used, thickness of the shield, and the frequency of the interference. 

Types of Interference:

• Radiated EMI: Radiated EMI consists of electromagnetic waves that travel through the air and can interfere with electronic devices. BLS helps block these waves from entering or leaving the shielded area, ensuring that sensitive components are not affected by nearby sources of EMI. 

• Conducted EMI: Conducted EMI travels through conductive paths, such as power lines or signal cables, and can cause interference in electronic circuits. While BLS primarily targets radiated EMI, it also helps reduce conducted EMI by preventing the emission of radiated energy that could induce currents in nearby conductive paths. 

• Radio Frequency Interference (RFI): RFI is a specific type of EMI that occurs at radio frequencies, typically in the range of 10 kHz to 300 GHz. RFI can disrupt wireless communication, signal processing, and other high-frequency operations. BLS effectively blocks RFI, ensuring that the electronic device’s functionality is not compromised by nearby radio frequency sources. 

Understanding Board-Level Shield Design and Implementation

Board-Level Shields are available in different material types and configurations. The choice of material for the shield is one of the most important factors that determines the effectiveness of an EMI/RFI Shield. Common materials include aluminum, stainless steel, nickel-silver, cold-rolled steel, beryllium copper, and phosphor bronze. These materials are chosen for their conductivity, mechanical strength, and ability to provide effective shielding across a wide range of frequencies. 

BLS can be implemented in several configurations, each suited to different applications:

1. One-Piece Shields: A single metal enclosure that covers the components needing protection. It provides effective shielding with minimal seams, reducing the risk of EMI/RFI leakage. 

2. Two-Piece Shields: Consists of a metal frame and a removable cover, allowing easy access to the shielded components for testing and repairs without damaging the PCB. 

3. Multi-Cavity Shields: This design integrates multiple compartments within a single shield, each protecting different sections of the PCB. This approach saves space and reduces overall shield weight while still providing effective EMI/RFI protection.

4. Peel Shields: A shield design with a peelable top section, allowing easy access to the components without the need for desoldering, making it ideal for situations where infrequent access is needed.

The shield can be mounted to the PCB using various techniques, including surface-mount, through-hole, snap-fit, and clip mounting. The choice of mounting method depends on the specific application and the design of the PCB.

How does Board Level Shielding Help with EMC and Enhancing Signal Integrity?

• Suppression of Emissions: By containing the electromagnetic emissions from high-frequency circuits, BLS helps ensure that the device does not emit excessive EMI that could interfere with other electronic systems in the vicinity. This is crucial for compliance with electromagnetic compatibility (EMC) regulations.

• Protection from External EMI/RFI: BLS also protects the device’s internal components from external sources of EMI/RFI. This ensures that the device functions reliably even in environments with high levels of electromagnetic activity, such as industrial settings or crowded wireless communication environments.

• Reducing Crosstalk: BLS helps reduce crosstalk between adjacent circuits on the PCB by isolating sensitive components from each other. This isolation is essential for maintaining signal integrity, especially in high-speed digital circuits and RF communication systems.

• Improving Device Performance: By preventing EMI/RFI from affecting critical components, BLS helps ensure that the device performs as intended, with minimal signal distortion, data loss, or communication errors.

Board-level shielding is an important part of modern electronics. By creating a conductive barrier around sensitive components, BLS ensures that electronic devices can operate reliably in complex and high-interference environments, safeguarding both the device's performance and the integrity of nearby electronic systems.

Click here to see Board Level Shielding Solutions for EMI / RFI on everything RF.