As digital electronic devices play a central role in our lives, electromagnetic interference is becoming a concern. Electronic OEMs are implementing various techniques to reduce the effects of EMI on devices. The first level of shielding is always performed on the printed circuit board, which is an integral part of any electronic device and second on the entire system using a sturdy enclosure. The printed circuit boards contribute to the performance and current carrying properties of electronic devices. Thus, they must be shielded from electromagnetic interference. Generally, PCB designers achieve this through design techniques and additional shielding mechanisms, such as board level shielding. EMI gasket shielding is usually implemented around electronic devices. How do these shielding types work? How do they differ? Read the post to know the answers.
How EMI Gaskets Works
EMI gaskets are designed to electrically seal sturdy enclosures 6to protect electronic equipment from radio frequency interference (RFI) and electromagnetic interference. These gaskets create a conductive path in the seams and other openings of an electronic enclosure to ensure smooth current flow. EMI gaskets create Faraday Cage by electrically connecting the enclosure to the ground plane around the electronics and help prevent destructive EMI from interfering with the performance of electronics. These EMI shielding solutions are used for applications when their EMI exceeds 60dB.
EMI gaskets can be created from different materials, including metals, foam, plastic, and various elastomers. Based on their construction, the gaskets can be differentiated into the following:
- Beryllium Copper Gaskets: These are high-performance EMI shielding gaskets used around electronics to prevent EMI. Beryllium copper is an alloy with extraordinary high conductivity and excellent machinability. As a result, it can be easily converted into a gasket of any shape.
- Wire Mesh: Made of wire mesh, these EMI gaskets provide excellent EMI shielding and are suited for making permanent seals.
- Conductive Elastomer Gaskets: EMI gaskets of this type are made of conductive elastomers and feature embedded wires and metallic particles. They require pressure to assure safe EMI field.
- Silicone EMI Gaskets: These gaskets are made from silicone material and possess excellent tear and tensile strength, and compression set properties. Along with EMI, the gaskets can resist fire, water, ozone, and aging. Silicone EMI gaskets are the most common type of EMI gaskets used today and are effective for most types of electronics.
- EPDM Gaskets: These EMI gaskets can work excellent in high and low temperatures and possess excellent tensile strength than silicone gaskets. They can resist EMI as well as a wide range of environmental elements, which makes them ideal for a broad range of outdoor environments.
- Fluorosilicone EMI Gaskets: This material can resist oil, ozone, UV, and broad range of chemicals and environmental elements. Owing to its properties, it is quite common to see fluorosilicone EMI gaskets on electronic applications for the aerospace industry.
An Overview of Board Level Shielding
As said before, board level shields are used to minimize the effect of EMI on the printed circuit boards. Generally, board level shields are created as metallic enclosures of miniature level. They help isolate board-level components, reduce crosstalk, and curb the susceptibility of EMI, without affecting the performance.
Board level shields are often distinguished on the basis of design into:
- One-piece Board Level Shields: These shields possess one-piece construction, which protects the board on all six sides. The sixth side is always the ground plane of the board.
- Two-piece Board Level Shields: As the name suggests, these shields possess two-piece construction with a frame or fence and snap-on, snap-off cover, which protects the board on all six sides. The sixth side is always the ground plane of the board.
When it comes to a one-piece board level shield, the access to shielded components may be limited and feature rigid corners. However, two-piece board-level shields are more appropriate for applications where regular repair and inspection may be needed.
Side by Side Comparison of EMI Gaskets and Board Level Shielding
EMI gaskets and board level shields both are effective for reducing EMI. Sometimes, it is important to focus on one factor more than the other.
- EMI gaskets are designed for large electronic devices and board-level shielding is used for PCB.
- EMI gaskets are designed for EMI shielding and are environmentally sealed to keep out moisture and other elements. Made of durable plastic and metals, these gaskets are rigid and weigh more, which would add to the overall weight of the device. Against this, the board-level shielding is exclusively designed for EMI shielding. Board level shielding solutions like SnapShot is designed using metallized plastic, which doesn’t add to the weight of the PCB.
- EMI gaskets are difficult to remove for repair and maintenance. However, board-level shielding solutions like SnapShot with their snap-in-place can be easily removed for repair and inspection.
Although designed to perform the same task, these EMI shielding solutions differ in terms of size and shape. The choice of the right solution depends on your requirements. If you have been considering board level shielding solutions for your applications, you need to consider the solutions that offers you design flexibility, durability, and superior shielding effectiveness like SnapShot® EMI Shield. It provides consistent isolation across a wide frequency range and outperforms competitive options in shielding effectiveness from below 100 MHz to 12 GHz.
