HHV develops an innovative process of coating on plastics to provide EMI shielding

Hind High Vacuum Co. Pvt. Ltd. (HHV), a vacuum science and Technology Company with major clients like HAL, ISRO, BARC, Titan etc, announced that it has indigenously developed an innovative process of coating on plastics to provide Electromagnetic Radiation Interference (EMI) shielding. This was entirely developed by HHV’s team of scientists at its Bangalore facility as a part of its ongoing ‘Make in India’ initiative.

These coatings will find application in the field of Electronics, telecommunications, medical instrumentation, Flat Panel displays, membrane switches, sensors, Aircraft canopies etc.

EMI can disrupt electronic devices, equipment and systems that are used in critical applications viz. Medical, military, aerospace, touch screens, navigation to name a few. The causes of EMI include both manmade and natural. The results can range from temporary disturbances and data losses to system failure and even loss of life.

Traditionally EMI shielding materials include flexible metal sheets that can fit into the electronic housing or enclosure. Aluminium, copper and steel are commonly used. Coatings made of metallic inks are also applied to interiors of electronic enclosures to provide EMI shielding. The biggest challenge one faces is when the display panel of the electronic device which is made of plastic or acrylic material has to be made EMI resistant. The metal sheet cannot cover the display panel as it has to be transparent.

“HHV scientists have overcome this limitation by developing a process of coating a material which is conducting as well as transparent. The special process uses ion assisted magnetron sputtering technique under a high vacuum” said Prasanth Sakhamuri, Managing Director of HHV. “The process uses Indium Tin Oxide (ITO) which can be deposited on plastics. These are used as transparent EMI / RFI shielding coatings. The most common plastic or polymer substrates that are in use are Polycarbonate and PMMA (Acrylic). These coatings can be used to eliminate interference of stray electromagnetic rays that can damage sensitive devices”.

ITO coatings can be applied by this technique on to flexible substrates such as PET and Kapton which are widely used in scientific research and LCD / OLED manufacturing processes. The ITO coated substrates can further be patterned to create a circuit of required resistance and can be connected to external sources using conductive paints, inks or tapes. ITO coatings on plastics also find applications as low-E windows, which have a high transmission of visible light while reflecting IR radiation.

ITO coatings can also be index-matched along with an Antireflection Coating layer in applications such as LCD displays to reduce reflectance at various interfaces.

In order to achieve a high transmission and low resistivity, ITO coatings can be carried out at high temperature on glass substrates. But since there is temperature limitation on plastic substrates, the ion-assisted process which has been developed comes handy. Ion-assisted process involves the use of energetic ions that bombard the growing film, greatly enhancing its structural properties. Especially while working with low melting point materials like plastics where the substrate temperature has to be kept low, the alternative is to use an ion beam, which supplies the required energy. For an ion-assisted process, a low energy and high current ion beam is beneficial and such a process also provides high environmental stability of the ITO films in addition to the high transmission and low resistivity.

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