Imagine living an entire day without the use of your cell phone, desktop, laptop, television, tablet, or radio. Sounds difficult, doesn’t it? That’s because we, as a society, have become overly reliant on electronics. Nearly every US citizen owns one or more devices nowadays. And there is no doubt that they make our lives more convenient. But with the good comes the bad, and in the case of consumer electronics, nearly all of them emit electromagnetic interference (EMI) capable of disrupting other pieces of electrical equipment. This EMI is also responsible for various health problems. That’s why engineers constantly endeavor to curb the interference effects through the use of innovative shielding methods like shielded windows. These components provide an EMI screen as part of a shielded enclosure to protect against radiated emissions and susceptibility. Find more information below:
Application of EMI Shielded Windows
Shielded windows are commonly used in consumer electronics like LCD, LED, plasma, vacuum, and fluorescent. They possess high transparency levels, which make them ideal for viewing display devices. Engineers also use shielded EMI windows in the construction of front panels of an enclosure to impart benefits such as impact protection, display color matching, contrast enhancement, anti-glare and anti-reflective surfaces. If the windows are big enough, they are capable of providing transparent EMI shielding, which is highly prized by architects of shielded rooms, computer rooms, secure communication cabins, and MRI rooms.
Product Presentation
Shielded EMI windows are available as per the specifications of the customer. When it comes to architectural use, the sizes of these components can range from a mere 1 cm2 to as big as 1 X 2 meters. There are plenty of customization options to look forward to, from silk-screened EMI windows to products featuring information and logos.
Shielding Mechanism
A powerful EMI shield without any compromise on optical transparency – that’s what shielded windows are primarily used for. To achieve this, engineers use a vapor-deposited transparent conductive coating like gold or indium tin oxide to coat the surface of a clear optical substrate like glass, polycarbonate, or acrylic. Alternatively, they can get the same results by using a fine woven wire mesh embedded in the clear optical substrate.
For terminating the window to the shielded enclosure, a continuous low resistance conductive edge is applied around it – something like a conductive gasket or a conductive buss bar. Some manufacturers may even use extended wire mesh.
Design Considerations
Optical Substrates
- Engineers prefer acrylic substrates due to their versatility. Since they are available in different colors, engineers use acrylic materials to match display outputs for improved contrast enhancement. Acrylics can easily be molded to make them suitable for front panels that require holes, cutouts, steps, The material is highly scratch-resistant and can withstand flames.
- For rugged applications, polycarbonates are the best choice for their endurance and impact resistance. Despite the light transmission of 85 percent falling short of other substrates, polycarbonates have tremendous flammability rating. Moreover, they are hard and resistant to both scratches and chemicals.
- Glass surfaces are quite durable and capable of withstanding increased temperatures. Thus, it is the perfect material for applying vapor coatings like indium tin oxide for electromagnetic shielding.
- Some spectacle lens manufacturers use Allyl Diglycol Carbonate (ADC) because of its impact-resistance and toughness. However, it fails to protect against notches or scratches.
Shielding Media
- Most engineers prefer fine wire meshes because they offer the best shielding along with high-quality optical properties. The wires are normally composed of copper or stainless steel. The more the density of the wire, the better the shielding performance. But optical clarity and light transmission take a hit in the process. For optimum shielding, the recommended wire count is roughly 80 to 100 wires for every inch. This wire gets blackened and plated so that wire crossovers get fused, thereby delivering consistent EMC performance.
- The application of materials like gold, indium tin oxide, and other transparent vapor deposited conductive coatings does not provide foolproof EMI resistance. However, unlike fine wire meshes, they help maintain optical clarity without any degradation in fringing or resolution.
EMI shielded windows are an integral part of a shielded enclosure. Not only do they maintain high optical transparency but they are capable of delivering excellent shielding performance. No wonder they are employed by various industries to limit the effects of electromagnetic interference and protect different electrical components and devices. With electronics use becoming more widespread with each passing day, the importance of EMI shielded windows is bound to increase as well.
