As you might already know, shielding is the technique commonly used for controlling EMC – Electro-Magnetic Compatibility. The process involves the use of EMI shielding cans or screening covers for printed circuit boards (PCBs). These PCB shields help in protecting the target electronic device and its components from harmful radiations at the source. In simple words, metal enclosures are used to keep harmful interference out, as well as unwanted emissions inside. Now let’s better understand what PCB shielding is and what its common applications are.
What is Shielding?
Electro Magnetic Compatibility (EMC) means that a circuit has been designed with a shielding enclosure to prevent the disruption. Shielding, also known as EMC Shielding is any method used to protect a device from harmful interferences. This technique helps in preventing external signals from causing interferences, as well as avoids leaking of a stronger signal from internal components that could interfere with surrounding electronics. The shields designed for EMC cover PCB components like IC chips, connectors, and other elements to protect the components from harmful radiations at the source. The
Electromagnetic frequencies produced by the devices or the radiations from the outside source needs to be controlled for several reasons. These interferences can affect many sensitive electronics and can cause issues such as a total disruption of a safety-critical signal.
How does Shields work?
The EMI shield creates a Faraday cage around the enclosed RF components. To achieve this goal, a metallic enclosure is placed around and in close proximity to the components on a PCB. The top five sides of this metallic box are a shielding cover or metal can, while the bottom side is the ground plane within the PCB. This shield helps in protecting the device from unwanted radiation at the source. The metallic screen absorbs the electromagnetic interference, thereby preventing electromagnetic interference (EMI) or radio frequency interference (RFI) from impacting sensitive electronics.
The EMI shielding cans or screening covers for printed circuit boards (PCBs) come in standard sizes and are custom-made to suit specific applications. PCB shields can be designed using different techniques and various materials. The type of material used for EMC shielding depends on the type of electronics and frequencies involved. Materials commonly used for shielding include stainless steel, brass, nickel silver, and more. It is believed that tin-plated steel is the best choice for shielding below 100 MHz. For the applications that require above 200 MHz, tin-plated copper is the right choice.
Applications of Shielding
EMI/RFI affects a diverse range of devices, including all consumer and industrial electronics, as well as critical systems for military and healthcare services. PCB shields are commonly used in multiple industries such as communications, military, defense, aerospace, computer and electronics, hybrid circuits, telecommunications, automotive, and more. Shielding products are necessary for devices like medical instruments, smartphones, laser, office equipment, control systems, power semiconductor, RFID, strategic weapon systems, etc. The EMC shield manufacturers can also engineer and manufacture customized shielding parts, accessories, and components to eliminate or reduce electromagnetic interference. This helps in protecting electronic products from harmful radiation and improves device performance.