Coatings and shields are an important part of electronic devices, printed circuit boards (PCBs), and so on. Both these techniques offer protection to the board components, wires, and so on from electromagnetic interference (EMI) as well as other external parameters. However, coating is different from shielding. Coating is done in the form of paints or sprays, while EMI shields are in the form of a metal can attached onto the board. Coatings are also done on device enclosures to prevent crosstalk and noise. But what is EMI coating on PCBs? Is it different from EMI shielding or are these terms used interchangeably? This post discusses the details of EMI coating for PCBs and more.
Are EMI Coatings Really Effective?
Coatings or shields are nowadays used for almost all devices and boards. For most devices, Faraday cages, which laid the foundation of coatings and shields, are still used. They help block electric signals. However, with advancements in electronics, devices are shrinking in size and with multiple functionalities. Such devices need new age PCBs which are flexible, small in size, and can accommodate several components. Several components on a single board implies increased mixing of signals which leads to electromagnetic interference. Thus, coatings and shields have gained prominence. Conductive coatings are used for two reasons – create signal barrier to block noise and protect the components and devices from contamination, spillage, and other external parameters. These coatings are conductive metal layers or films done by spraying or brushing. Shields, on the other hand are soldered on metal cans that have proven to be more effective than EMI coatings.
Drawbacks of EMI Coatings
Here are some issues with EMI coatings which can be overcome by EMI shields.
- Coatings develop scratch issues which may spoil the wiring or components and device functioning.
- These coatings are not removable, and once removed cannot be reapplied. This makes it difficult to rework on a PCB such as adding or deleting components.
- Coating films cannot be recycled and hence is not a sustainable solution.
- Coatings are mainly suited for enclosures to block signals rather than using for intricate PCB designs or targeted components.
Why Use EMI Shields for PCBs?
EMI shields used for PCBs are an advanced version of conventional coating techniques, and offer several benefits. Here are some of them.
- EMI shields developed nowadays are made of a layer of conductive metal, while there is a non-conductive layer made using thermoplastics such as polyetherimide.
- These are absolutely flexible and can be removed when required. They are just as easy to reuse or reapply.
- You can create these EMI shields based on the board size and dimensions, which makes them customizable.
- The materials used can be recycled and hence EMI shields are a more sustainable solution then EMI coating or paints.
- EMI shields, depending on the materials used, have a wide operating temperature range and offer a good isolation for a wide frequency range from below 1 GHz to 12 GHz and beyond.
It is necessary to use shielding techniques for your PCBs to mitigate EMI and increase the efficiency of your device. EMI shields serve as the best option in controlling EMI and have several other advantages. Ensure you source them from known manufacturers and suppliers. XGR Technologies offers SnapShot ™ EMI shields made of a thin polyetherimide film on the interior and tin on the exterior surfaces. The non-conductive interior surface reduces electromagnetic coupling. These super lightweight shields are easy to use and reinstall if you need to make any changes to the board. If you need further information on these EMI shields, you can contact the XGR Technologies team via phone or email.
