Shielding electronic devices from electromagnetic radiation
Today’s product designers face a number of challenges when it comes to designing electronic devices for consumers as well as for the business-to-business (B2B) markets. As these devices become increasingly smaller and more complex in nature, shielding them against electromagnetic interference gets more difficult.
High-frequency radiation, particularly radio waves, emanating from gadgets like cell phones, not only produces cross-talk between devices, but also has a negative impact on the health of people. In an effort to minimise such interference, engineers design the printed circuit boards (PCBs) of the devices in a way that the components remain isolated from one another.
All reputed brands in the industry focus on the careful selection and use of proper EMI shielding materials, as this is not only crucial for effective shielding, but also important in order to meet a wide range of application challenges that today’s designers face.
Types of EMI shielding
Device failure caused by interference or ‘noise’ from electromagnetic energy is increasing due to the growing number of products that contain sensitive electronic components.
• Reflection: The primary mechanism of electromagnetic shielding involves reflection. In order to be able to reflect the radiation, the shield needs to be electrically conductive. Since metals have this property, they are good shielding materials; however, they are bulky. In order to overcome this shortcoming, sheets with metal coatings that are created by electroplating, electroless plating or vacuum deposition, are generally used. Absorption: The secondary aspect of shielding involves the absorption of radiated energy. In order to facilitate absorption, the material should have electric and/or magnetic dipoles – the separation of positive and negative charges. Magnetic dipoles can be provided by materials with high levels of magnetic permeability. Super permalloy, mumetal and iron oxide are some of the materials that are excellent for absorption.
Multiple reflections: This process involves the reflection off various surfaces and interfaces. To be effective, this mechanism requires a large surface area. Shields made of foam or porous materials are good for multiple reflections. Composite materials