Conformal Shielding – A New Innovative Technology in The RFI/EMI Shielding Space
Mobile devices have become smaller, yet smarter. The complex design of these high- speed digital devices produce a considerable amount of electromagnetic and radio frequency noise, subsequently triggering a variety of intra-system issues such as unwanted coupling between integrated components, line coupling and crosstalk. These in turn affect the normal operation of the system. All these are creating considerable challenges for electronics designers, especially those working at the printed circuit board (PCB) level. There are a range of electromagnetic interference (EMI) and radio frequency (RFI) shielding methods that can be used to keep sensitive PCB components and modules isolated from each other. These methods help diminish the levels of unwanted radiation and the havoc it causes. However, one technology has gained in prominence in this space in the recent years and that is conformal shielding technology.
Benefits of Conformal Shielding
Conformal shielding enables designers to achieve the following RFI shielding goals:
- It helps to cut down the amount of radiated power
- Keeps EMI and RFI interference at the minimum level
- Helps to eliminate the sensitivity to board placement
- Besides keeping a device’s sub-systems isolated from each other, conformal coating also keeps the PCB protected from environmental hazards
- The biggest advantage of using conformal shielding is that you can apply this protective coating even after the primary design phase is over. This facility makes it a practical option for designers who haven’t anticipated the incorporation of shielding feature at the time of conception.
Three Ways of Applying Conformal Coating
Conformal shielding is described as a batch process which complements the
fit, forms and functions of PCB design. Three major conformal shielding techniques include sputtering, painting, and plating.
Spluttering: This involves the application of a thin layer of copper (Cu) on the outside surface of the PCB components. Generally, a physical vapor deposition (PVD) magnetron machine is used to apply this metallic coat. The process is typically carried on in a vacuum chamber. The idea is to stimulate the metal to release atoms inside the chamber. Various parts of the PCB components eventually get covered with these atoms. The entire process is conducted in a plasma environment because it helps to excite the ions, and release more atoms.
Conductive paints have been used in industrial applications since long. For example, the aerospace industry has been leveraging this method to protect vital components from undesired noise. Painting involves coating the surfaces of desired components with an epoxy coating, comprising metal flakes of silver (Ag). Gold (Ag), copper (cu) and other metals are also used. The metal flakes are suspended in a solvent solution, and this metal-mixed solution is then sprayed over the targeted area. The solvent evaporates eventually, but the metals stay on giving a solid coating over the component surfaces.
Plating is a popular shielding process for the electronic industry. It proves to be the most effective when used for PCB components. Before actual plating, the module surface is prepared through a few roughening steps. This preparation helps metal coatings to perfectly adhere to the module. Thanks to its excellent conductivity, copper is used as a major coating material. Copper is also preferred for its low price. A nickel layer is also added on top of the copper coating to prevent the oxidation of copper. While copper acts as the primary shielding layer, the nickel layer functions as a protective agent against environmental hazards and takes care of cosmetic improvement.
Conformal technology offers a highly sophisticated EMI and RFI shielding mechanism for any electronic component that is sensitive to energy radiations. According to experts, the technology can be used to build a true ‘plug-and-play’ solution for the creation of a robust board design and product layout. By minimizing circuit board’s vulnerability to electromagnetic radiations, this technology speeds up the design process, subsequently accelerating time-to-market and lowering the cost of RF implementation.