Board-level shielding uses a conductive metal cover to help protect selected components or circuits on a printed circuit board from electromagnetic interference. It can also help contain emissions produced by components within the shielded area.
This targeted approach is often used when interference affects a specific part of a PCB, and screening the entire product housing would be unnecessary or impractical.
This guide explains how board-level shielding works, when it may be needed and the differences between shielding an individual PCB area and the complete electronic enclosure. It also covers common shield formats and the technical considerations to keep in mind when specifying a standard or custom solution.
What Is Board-Level Shielding?
Board-level shielding is a circuit-level method of controlling electromagnetic or radio-frequency interference. A metal can, cover, or frame-and-lid assembly is fitted over a defined section of a printed circuit board, creating a conductive barrier between the enclosed components and the surrounding electronics.
The shield may be used to contain energy produced by components such as oscillators, processors or switching circuits. It may also protect receivers, sensors and other sensitive circuitry from interference generated elsewhere on the board or outside the product.
This differs from screening the complete electronic enclosure. Instead of surrounding the entire assembly, board-level shielding focuses on an identified source of emissions or an area requiring protection. The shield’s dimensions, material, grounding, apertures, and contact with the PCB all influence its performance.
How Does Board-Level EMI Shielding Work?
A board-level shield creates a conductive barrier between selected electronic components and the surrounding environment. When properly incorporated into the PCB design, it may reduce the transfer of unwanted electromagnetic energy into or out of the enclosed area.
For example, a power conversion circuit could generate emissions close to a sensitive receiver or measurement circuit. Placing an appropriate shield around the source, the sensitive circuit, or both may help reduce interference between them.
The effectiveness of PCB shielding does not depend solely on the metal cover. Other important factors include:
- The shield material and thickness
- The frequencies involved
- Electrical contact and grounding arrangements
- Continuity around the shield perimeter
- Gaps, seams and apertures
- The position of tracks and components
- Heat generation and airflow
- The shield’s mounting method
Openings may be needed for cables, connectors, component adjustment or ventilation. These requirements should be considered carefully because gaps in the conductive barrier can affect shielding performance.
The complete circuit, enclosure and grounding strategy must therefore be reviewed together.
When Is Board-Level Shielding Needed?
Not every printed circuit board requires a shielding can. The decision should be based on the circuit design, operating environment, testing and the likely source or path of interference.
There are several situations in which board-level shielding may be considered.
When a Circuit Generates Unwanted Emissions
Processors, oscillators, switching circuits, power conversion components and other high-frequency electronics can produce electromagnetic energy during operation.
This does not mean that every such component must be covered. PCB layout, filtering, grounding and component placement should be considered first. Where these measures do not provide enough control, a board-level shield may form part of the solution.
When Sensitive Components Need Protection
Some parts of a circuit can be more susceptible to interference than others. Receivers, sensors, measurement circuits and low-level signal components may be affected by energy generated elsewhere on the PCB or by an external source.
A shield may help create separation between the sensitive section and the source of interference. The design still needs suitable grounding, component positioning and signal routing.
When Different Areas of the Same PCB Interfere
Interference does not have to come from another product. Components positioned close together on the same PCB may interact, particularly when the board contains a mixture of digital, analogue, radio-frequency, and power circuitry.
Localised shielding can help separate functional areas without requiring the complete assembly to be placed inside a metal enclosure.
When Space Is Limited
A fully screened product enclosure may be unsuitable due to its size, weight, material, or design. Board-level shielding focuses on a smaller area and can sometimes be accommodated within the existing housing.
Space must still be allowed for the shield footprint, component height, mounting points and any removable lid.
What Must Manufacturers Do to Meet EMC Requirements?
Before placing electrical or electronic equipment on the market in Great Britain, manufacturers must ensure it meets the essential electromagnetic compatibility requirements. The product must not generate electromagnetic interference at a level that prevents nearby radio, telecommunications or other equipment from working correctly. It must also have sufficient immunity to the interference expected during its intended use, allowing it to operate without unacceptable loss of performance.
Manufacturers must complete the appropriate conformity assessment, prepare supporting technical documentation and draw up a declaration of conformity. The applicable CE or UKCA marking must then be displayed visibly, legibly and permanently on the product. Where the nature of the product makes this impractical, the marking may be placed on its packaging or accompanying documentation.
The product must also carry suitable identification, such as a type, batch or serial number, along with the manufacturer’s name or registered trade mark and a contactable postal address. Relevant instructions must be supplied in English.
Technical documentation and the declaration of conformity must be retained for 10 years after the product is placed on the market. Manufacturers must also maintain procedures that ensure products made in a series continue to comply, particularly when the design, product characteristics or applicable technical standards change.
If a manufacturer believes a product does not comply, they must take appropriate corrective action. This may involve bringing the product into conformity, withdrawing it from sale or issuing a recall. Where the product presents a risk, the relevant market surveillance authority must be informed promptly. Manufacturers must also cooperate with enforcement authorities and provide the requested compliance information.
Board-Level Shielding or a Fully Shielded Enclosure?
Neither approach is automatically better. The appropriate option depends on where the interference originates, which components are affected and how the complete product is constructed.
| Consideration | Board-level shielding | Complete enclosure shielding |
| Area covered | Selected components or PCB sections | Most or all electronics within the housing |
| Typical purpose | Localised emissions control or circuit protection | Broader product-level screening |
| Space required | Allowance on and above the PCB | Affects the complete product housing |
| Component access | Depends on whether the lid is removable | Usually requires opening the main housing |
| Design focus | Circuit-level requirements | Complete enclosure and product requirements |
| Customisation | Based on PCB footprint and component layout | Based on the dimensions and construction of the complete assembly |
A design may use both methods. A screened product enclosure could provide broader protection, while board-level shields separate particularly noisy or sensitive sections within it.
The decision should follow investigation and testing rather than assumption.
What Types of PCB Shielding Cans Are Available?
PCB shielding cans can be manufactured in several formats. The right option depends on whether components require access, the space available and how the shield will be assembled.
One-Piece Shielding Cans
A one-piece can provides a straightforward cover around the selected circuit area. It may suit applications where regular access to the enclosed components is not required.
The design must account for the shield footprint, component clearance and mounting arrangement. Manufacturing and servicing requirements should also be considered before choosing a permanent or semi-permanent format.
Frames with Removable Lids
A separate frame and lid can provide access to the components inside the shield. This may be useful when inspection, adjustment, testing or rework is required after the frame has been mounted.
The quality of contact between the frame and lid is an important part of the design. We offer a range of options, including PCB frame mounting and fingered lids, for relevant board-level applications.
Custom Board-Level Shields
A standard shielding may not suit every PCB. A custom design service may be needed when the PCB has unusual dimensions, restricted clearances, specific access requirements or components of different heights.
A custom design can account for the available footprint and mechanical constraints. Its suitability must still be assessed as part of the complete electronic design.
What Should Be Considered Before Specifying a Board-Level Shield?
Selecting a shield solely based on its external dimensions can lead to problems during assembly or testing. The electrical, mechanical and thermal requirements should be considered together.
Before approaching a manufacturer, gather as much of the following information as possible:
- The suspected interference source: Identify which component or circuit may be producing unwanted emissions.
- The area requiring protection: Establish whether the aim is to contain emissions, protect sensitive components or achieve both.
- The available PCB footprint: Provide the maximum length and width that can be allocated to the shield.
- Component height: Record the tallest component inside the proposed shielded area and allow suitable clearance.
- Access requirements: Determine whether enclosed parts require inspection, adjustment, testing, or repair.
- Grounding arrangements: Consider how the shield will connect with the PCB ground structure.
- Required openings: Identify cables, connectors, ventilation points and adjustment access that may pass through the shield.
- Temperature and airflow: Check whether enclosed components produce heat and how the shield could affect cooling.
- Assembly method: Consider how the shield will be mounted and how this fits the production process.
- Quantities: State whether the requirement is for a prototype, a small batch or an ongoing production run.
- Test information: Share any relevant EMC observations, test results or known frequency concerns.
Material selection may also influence manufacturability and screening performance. We provide a separate comparison of material screening properties for further technical context.
Can Board-Level Shielding Be Added After a PCB Has Been Designed?
It may be possible to add PCB shielding after the initial board design, but the available options are often more limited.
An existing layout may not have sufficient space for the shield footprint or appropriate grounding points. Nearby components, connectors and the product housing can also limit the available height and access.
Considering board-level shielding earlier gives the designer more control over:
- Component positioning
- Grounding points
- Shield dimensions
- Access to enclosed components
- Thermal management
- Assembly and manufacturing
Where a shield needs to be added to an existing design, the cause of the interference should be investigated first. Prototype manufacture and testing may then help determine whether the proposed arrangement is suitable.
Should You Choose Standard or Custom Board-Level Shielding?
A standard shield may be appropriate when its dimensions, height, mounting method and access arrangement suit the PCB. This can provide a practical solution without requiring a new design.
Custom board-level shielding may be more suitable where:
- The PCB has an unusual layout
- Space is tightly restricted
- Standard dimensions do not cover the required components
- A particular lid or access arrangement is needed
- Openings or other mechanical features must be included
- Prototype or specialist production requirements apply
We manufacture a range of board-level RFI and EMI screening solutions, including screening cans, frames, and lids for various PCB applications. Standard and custom options can be considered based on the project’s dimensions and requirements.
Discuss Your PCB Shielding Requirements with Perancea
Effective board-level shielding starts with a clear understanding of the PCB, the interference concern and the mechanical limits of the application.
We have extensive experience in electronic enclosures, RFI/EMI screening and fine-tolerance sheet metalwork. The team can discuss your PCB dimensions, component clearances, access requirements, quantities and preferred construction to identify an appropriate standard or custom option.
Discuss your PCB shielding requirements with us by sending your drawings, project details, or an initial specification to the team.
