What are EMC Board Level Shields? 

EMC Board-Level Shields are conductive metal enclosures or cabinets placed over critical circuits and components (e.g., ICs, active components) on a PCB to provide board-level EMI shielding. The metallic shielding functions as a Faraday cage that blocks electromagnetic radiation signals from entering or exiting the shielded area of the PCB. This shielding technique protects critical circuits and components from external EMI and also prevents internally generated EMI (from components inside the enclosure) from affecting nearby electronic circuits, devices, or components. 

Figure: Board-level shielding and one-piece, two-piece shield design shown The conductive metal enclosure is usually made up of Copper, Stainless Steel, Nickel-Silver, Cold Rolled Steel, Beryllium Copper, Cold Rolled Steel, and Phosphor Bronze. The choice of material is based on the type of circuits and frequency of operation. The choice of material depends on the type of circuits and the frequency of operation. These enclosures come in various configurations, including one-piece, two-piece, multi-cavity, and custom designs, with different sizes and mounting options, such as surface mounting and through-hole mounting. Board-level shielding, or PCB-level shielding, is an EMI/RFI shielding technique that significantly contributes to improving the EMC performance of electronic devices. 

How does EMC board-level shielding work?  

EMC board-level shielding is based on the principle used in a Faraday cage. When electromagnetic radiation signals strike the metallic enclosure, creating a current flow within the body of the metallic screen. Note that the EMI shields are connected to the ground plane. So that the currents generated from EMI are absorbed by the ground connection or a virtual ground plane. Thereby, the board-level shielding absorbs the internally or externally generated EMI, protecting electronic components and devices from radiated EMI/RFI.  The effectiveness of the EMI shield depends on the shielding material used, shielding thickness, and shielding volume. 

Applications: Board-level shielding is used to attenuate EMI/RFI at the PCB level in various electronics applications, including mobile phones & tablets,  routers, wireless meters, 2-in-1 notebooks, medical devices, point of sale (POS) equipment, wireless speakers, drones, servers, wearables & IoT, and more.  

EMI shielding in PCBs is one of the common design solutions used by the PCB designer to mitigate EMI issues and meet the EMC requirements outlined in various EMC standards. 

Specification details of EMC board-level shielding components: 

Material: Represents the material by which the EMC shield cabinet has been made. Some commonly used materials to make EMI shielding covers include Stainless Steel, Nickel-Silver, Cold Rolled Steel, Brass, Copper, Beryllium Copper, and Phosphor Bronze. 

Type: Represents the type of RF shielding enclosure. They are available in clip type, cover type, and frame type. 

Mounting: Represents the RF shield cabinet designed for which type of mounting, for example, through-hole, surface mount, and snap fit. 

No of pieces: Represents the number of available pieces in the RF shield cabinet. Usually, the number of available pieces is one or two.  

Material thickness: Represents the material thickness of the RF shield. It is represented in mm. 

Dimension: Represents the dimension Length mm x Width mm x Height mm of the EMC shield cabinet.