A PCB shielding can, also known as an electromagnetic interference (EMI) shield, is a metallic enclosure designed to protect sensitive electronic components on a printed circuit board from external electromagnetic radiation and prevent internal emissions from interfering with other devices. These shields are essential in high-frequency applications such as wireless communication devices, medical equipment, and aerospace electronics, where EMI can cause signal degradation, data errors, or complete system failure.

The primary function of a PCB shielding can is to create a Faraday cage—a conductive enclosure that blocks electromagnetic fields by reflecting or absorbing them. This is achieved through the use of conductive materials such as tin-plated steel, copper, or aluminum, which have high electrical conductivity and magnetic permeability. The choice of material depends on the frequency range of concern: copper is effective for high-frequency EMI (above 1 GHz), while steel is better for low-frequency magnetic fields.

Design considerations for PCB shielding cans include size, shape, and sealing. The can must enclose the target components tightly to minimize gaps, as even small openings can allow EMI to leak through. Shielding cans are often designed with a lid that snaps or solders onto a base frame, ensuring a continuous conductive path around the components. For components with leads or connectors, feedthrough filters (such as  feedthrough capacitors) are integrated into the shield to prevent EMI from traveling along wires.

Integration with the PCB is critical for effective shielding. The base of the shielding can is typically soldered to the PCB’s ground plane, creating a low-impedance path for electromagnetic energy to dissipate. This ground connection ensures that any EMI intercepted by the shield is safely routed away from sensitive components. Additionally, the shield’s height and footprint must be designed to fit within the PCB’s layout, avoiding interference with other components or connectors.

Shielding effectiveness (SE) is a key performance metric, measured in decibels (dB) and indicating the reduction in EMI achieved by the can. SE depends on factors such as material thickness, conductivity, and the quality of the seal. For example, a 0.2mm thick tin-plated steel shield can provide SE of 60-80 dB at frequencies up to 1 GHz, effectively blocking most EMI in consumer electronics.

Customization is common in PCB shielding can design. Shields can be stamped or formed into complex shapes to accommodate irregularly sized components or tight PCB layouts. They may include features like ventilation holes (covered with conductive mesh to maintain shielding) for heat dissipation, or notches to fit around tall components. In some cases, multiple shielding cans are used on a single PCB to isolate different sections, such as analog and digital circuits, which generate and are sensitive to different types of EMI.

Environmental and mechanical factors also influence design. Shielding cans in automotive or industrial PCBs must withstand vibration, temperature extremes, and corrosion, requiring materials with high tensile strength and protective coatings. Solderability is another consideration, as the shield must form a reliable bond with the PCB during assembly—often using solder paste or reflow soldering processes.

Testing PCB shielding cans involves measuring SE using techniques like the reverberation chamber method or the TEM cell method, which quantify the shield’s ability to block EMI across a range of frequencies. Engineers also conduct environmental tests to ensure the shield maintains performance under temperature cycling, humidity, and vibration. Compliance with standards such as CISPR (International Special Committee on Radio Interference) and FCC regulations ensures that the shielded PCB meets global EMI/EMC requirements.