EMI shielding, or Electromagnetic Interference shielding, refers to the practice of blocking or weakening the electromagnetic fields (EM fields) that can interfere with the operation of electronic devices.
EMI can affect the normal functioning of electronic circuits, leading to malfunctions, data loss, reduced performance, and disruptions to safety-critical signals. Sources of EMI can include nearby electronic devices, power lines or radio waves.
EMI shielding helps insulate sensitive electronic components from external interference while also preventing the device’s output from affecting other nearby electronic devices.
Ways to Shield
Here are three examples of the most effective types of EMI shielding.
Enclosures: Metallic enclosures or housings that surround sensitive electronics.
Gaskets & Seals: Conductive gaskets or seals are used to close gaps in enclosures and prevent leakage of EM fields. Custom molded silicone rubber is commonly used for this purpose.
Grounding & Shielding Tapes: Electrically conductive adhesive transfer tapes (ECATTs), metal foil tapes and metallized fabric shielding tapes for electric vehicle battery systems designed specifically to block electromagnetic interference (EMI) across a wide range of frequencies.
Coatings: Conductive coatings or paints are applied to non-metallic surfaces to create a shielded surface.
Applications
Automotive/EV: For vehicles, EMI shielding is used to ensure clear audio and video signals in entertainment systems, and for electric vehicle battery systems. They protect electronic control units (ECUs), such as engine and monitoring, braking systems and airbag deployment. Shielding is also crucial for the safe operation of radar, lidar, and cameras used in many driver assistance systems.
Consumer electronics: For electronics such as smartphones, laptops, and other gadgets, EMI shielding is needed to prevent interference with wireless communications and other nearby devices. It helps protect internal components such as CPUs, and memory from interference that could cause malfunction or data corruption. For TV and audio equipment, shielding helps minimize interference that could cause distortions or impact quality.
Industrial electronics: EMI shielding is used in industrial control systems to protect from interference from motors, power lines, and other machinery. EMI shielding in robotic systems ensures precise control and operation which are important in environments with high electromagnetic activity. Inverters, converters and other power electronics use shielding to insulate from other control circuits.
Medical devices: Shielding is critical in medical equipment to ensure accurate readings and safe operations, especially in environments like hospitals where many devices operate at the same time. Pacemakers and other implantable devices may need die-cut components to help shield from external electromagnetic fields to ensure they function correctly. EMI shielding is essential for reliable data collection in patient monitoring equipment.
Military and Aerospace: High standards for EMI shielding are required to protect equipment from external electromagnetic pulses and ensure reliable communication and safety. Shielding protects GPS and other navigation systems from interference, ensuring reliable positioning and guidance. Systems such as RADAR and electronic warfare systems require strict EMI shielding to be able to operate effectively.
Standards and Reliability
Many industries have specific standards and regulations governing EMI shielding to ensure that electronic devices operate safely and effectively without causing or suffering from interference.
For example, any electronic device designed for use in military applications must meet the standards of MIL-STD-285. This standard outlines the EMI shielding effectiveness requirements for military devices. The minimum effectiveness under MIL-STD-285 is 100 dB at frequencies between 20 and 10,000 hertz.
Additionally, EMI shielding is crucial for maintaining the reliability and safety of modern electronic devices, particularly as the density of electronic components increases and devices operate at higher frequencies.