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EMI Protection

As a manufacturer, it is important to ensure that your products are of the highest quality. Even if a display is merely a minor part of your product, it is integral that it operates reliably and efficiently. LCDs are used to communicate information from your hardware to your consumers, and LCD touch screens go a step further by being an interface for interaction. Ensuring that your displays work as effectively as possible needs to be ensured, and integrating EMI protection is one definite way to do this.

Electromagnetic Interference 

Before we go into how to protect your devices from EMI, let’s talk about what it is exactly. EMI stands for electromagnetic interference. It can also be called radio-frequency interference, or RFI when referring specifically to the EMI caused by radio waves. First, let’s establish a basic idea of what causes electromagnetic interference. When electrical components operate, they have electricity passing through them. Differences in voltage are enough to create an electric field, and the movement of electricity, or current, is what creates a magnetic field. Both of these are present in an electrical system working correctly, and due to this, form an electromagnetic field.

When an electromagnetic field from an external device is large enough to reach an electrical system, it can interfere with its functioning, and this is what is known as electromagnetic interference, or EMI. This isn’t only caused by external equipment, but can also be brought about by circuits within the same device. This can be caused by various home electronics and power lines.

Signals from components that broadcast wireless signals can also interfere with electrical systems. This includes signals from FM and AM radios, RADAR, Wi-Fi routers, smartphones and cellular networks, microwaves, and satellite signals. In cases like this, the interference is referred to specifically as radio-frequency interference, or RFI.

It’s also important to note that EMI doesn’t occur only from man-made sources. There are natural causes of EMI which include thunderstorms and solar flares. So no matter how free of external EMI sources your workplace is, you can’t control the natural ones. You can, however, protect your equipment from them.

Why should you worry about EMI?

As the name denotes, electromagnetic fields can interfere with electrical components and systems and cause disruptions in the function of these components, and even complete failure. LCD displays are some of the most susceptible components to EMI, and this is not limited to LCD touch screens in smartphones. The LCD displays in essential equipment such as heavy machinery, aircraft displays, and safety equipment, can be affected by EMI, and this constitutes a huge risk to the safety of not only personnel in the respective industries but civilians as well. This puts a lot of responsibility on touch screen display manufacturers.

Just because LCDs can be affected by EMI doesn’t mean you should forget that they are electrical components themselves. They can also produce EMI which can affect other components in a device, sometimes components more essential than themselves. Due to this, not only do you have to worry about shielding the LCD from electromagnetic fields produced by other components, but to prevent its electromagnetic fields from interfering with the other components in the system.

Essentially, EMI shielding is important for all components in a system that can create significant electromagnetic fields. Even minor electromagnetic fields can cause unnecessary disturbances in a system, if proximal enough to affect other components. We will specifically address those for LCD displays and LCD touch screens.

EMI’s Effect on LCD Displays

When an electromagnetic field is close enough to an LCD display, it can interfere with the way that data signals are sent to the display panel. What this means is that EMI can affect LCD displays by producing lines scrolling across the screen either horizontally or vertically, distortion of the color and saturation of images on the display, or it can cause complete failure of the display. As signal flow both to and from the display can be affected, the touch screen can also show signs of interference. This can be seen with false touches on the display, up to the touch screen being entirely responsive. In many cases, the LCD and the touch screen may display any mixture of these behaviors, making it essentially impossible to operate. This is completely unacceptable for critical machinery, making it evident why EMI protection should not be taken lightly.

Filtering Vs. Shielding  

emi filter infographicsemi shielding

There are two types of EMI protection. These are EMI filtering and EMI shielding. Combining these is one of the most effective means of reducing EMI.

EMI filtering involves selectively removing the unwanted electrical frequencies that constitute potential interference, yet still permitting the free movement of current. Filtering is utilized to suppress these frequencies at specific portions of the circuit. 

EMI shielding involves using any form of conductive barrier to block or reflect electromagnetic fields. This includes the use of gaskets or films. An electromagnetic wave received by the EMI shield will reflect a large proportion of the energy from the field, and convert the remainder to heat energy,

EMI Protection Methods

LCD displays and LCD touch screens can easily be shielded from EMI by several methods and the incorporation of special materials or components into the product by touch screen display manufacturers. 

The principal concept behind EMI protection is the use of conductive materials to attenuate the electromagnetic field that emanates from the component. This can be applied to LCDs in several manners.

EMI film is one means to achieve EMI protection for a display. This is a transparent, yet conductive film which is applied to the surface of an LCD display. This film is applied either behind or in front of the glass of the display, and a lamination process is used to apply the film completely flat with the screen, just like a natural layer to the glass. This renders it essentially unnoticeable. When an electromagnetic signal reaches the screen, it is conducted or caught by the film and attenuated before reaching the LCD touch screen below it. However, it is important to know that using EMI film is a passive, low-level means to protect against EMI. This is more of EMI filtering than absolute shielding, as it works mainly to prevent the display from affecting other components, though it has some very basic protection against external EMI.

An EMI mesh is a type of EMI gasket, and it is commonly used. The mesh is made of a conductive material that is woven or knitted. This is very flexible and can be placed around the edges of the display, to effectively seal any seams or gaps which could allow for electromagnetic fields to reach the internal components. 

EMI gaskets are a suitable means of shielding from EMI in bigger devices. An EMI gasket is constructed of conductive materials and made to enclose the components with a casing. By doing this, it creates a large protective shield, which prevents electromagnetic fields from reaching the components within, and prevents the electromagnetic waves from the components from affecting anything outside. A gasket will not prevent interaction between the components within it, however, so it is important to shield them individually. This can be achieved by shielding components, particularly those that do not require transmission or reception of RF waves, in a small conductive enclosure. Applying an EMI filter to the conductors for components, such as Bluetooth radios or RF transmitters, can also help to filter out electrical noise and potential EMI.

The underside of a display can have a sheet of copper or any other metal placed, to isolate the LCD from the components underneath, and minimize their interaction with one another in terms of EMI. Copper is the preferred metal as it is a good conductor of electricity.

Electromagnetic interference can even be prevented by modifying minor parts of the manufacturing process to be conductive. For instance, EMI tape can be used not only to hold components together but as it is constructed with conductive elements, it can hold any electromagnetic current that reaches the device and prevent it from inducing a current in the delicate components beneath it. 

A silver epoxy bus bar is another often overlooked means of shielding components from EMI. The epoxy contains silver, which allows it to act as more than just as an adhesive, but to be able to conduct electrical currents as well.

These methods are all kept in mind during the production of LCD displays, and pre-existing LCD displays or LCD touch screens can be enhanced by these methods without having to return to the drawing board.

Protect Your Displays with E3 Displays

It is of utmost importance to ensure that your LCD displays and LCD touch screens are not affected by EMI, and can hold in the electromagnetic fields they produce, to prevent them from interfering with other components in a system.

All the methods above can be easily applied to LCDs that have already been manufactured, or new designs can be developed and have EMI protection in mind from the very start. LCD touch screens can be as easily shielded from EMI as regular displays, without any compromise in input quality.

Regardless of what industry you are in, complying with all regulations involving controlling electromagnetic radiation from your product doesn’t need to be stressful. We can ensure quality products that will leave your clients and customers entirely satisfied, and most importantly, safe.

We’re a global design and manufacturing company that helps the world’s most innovative companies define the future of their business display needs. With over 20 years of combined experience in display technology, E3 Displays has everything you need to develop and manufacture your custom touch display all in one place. With customer-centric solutions featuring strategic planning, competitive pricing, longevity, and support, we ensure the best products on the market to help you scale. In the end, displays are a centerpiece in any hardware that provides a very important visual message in your product. We want to ensure that the visual entity exceeds your optical and performance requirements.

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