PRODUCTS OPTOELECTRONICS How LiFi systems are lighting the way NEW 30° BEAM ANGLE SMD LEDS


built upon LiFi enabling an alternative connectivity option – ideal for use in areas sensitive to radio frequency such as hospitals, power plants, schools etc. or areas with poor or no WiFi connection (e.g. multi-tenancy buildings, underground). The provision of reliable wireless communication is


Great quality light as well as a fast and stable broadband connection are what you can expect from the first wave of LiFi-enabled commercial products made available earlier this year such as the Philips Powerbalance gen2 and Philips LuxSpace downlight, which are available in Europe, Middle East and some Asian countries. With huge scope across professional and B2B markets,


LiFi systems are addressing segments from banking & government, to healthcare and hospitality. Not only this, Signify foresees the potential for growth into consumer markets. Whether an employee, resident or even a guest in the smart building of the future – people can enjoy the double benefit of quality, energy efficient LED light through a secure, stable and fast connection. With each light point equipped with a built-in modem that controls the light at speeds invisible to the human eye but detectable by a LiFi USB access key/dongle plugged into the socket of a laptop or tablet. The LiFi USB dongle returns data to the luminaire through an infra-red link. With a wide range of benefits and use cases, the first is


another huge benefit of LiFi – something traditional WiFi can struggle to accommodate at times due to a congested network. By having guaranteed bandwidth, a stable data rate per each user is provided. It also provides a broad spectrum - the light spectrum is 10,000 times bigger than the radio frequency spectrum (which WiFi relies on), meaning that LiFi offers plenty of bandwidth for connecting many IoT devices. Signify’s LiFi offers scalable capabilities for numerous users – this translates to up-to 15 users within the coverage beam of one light point. Where security is a priority, such as in banks, Government


buildings or large data centres, LiFi can provide stable and consistent connectivity with an added layer of security. This extra layer comes from the simple fact that light cannot penetrate walls. Seeing the connection is within line of sight, this security is enabled with the personal USB access key (this can also be administered on a controlled distribution). Additionally, it’s important to consider the areas in which


radio waves are not permitted due to health concerns, or the possibility of interference with sensitive technologies (e.g. elementary schools in France where radio waves are not permitted, or in some areas of hospitals and clinics with extremely sensitive equipment). With the above in mind, the scope for LiFi to become a staple of smart city infrastructures is a foreseeable possibility – and with so many use cases, LiFi provides a good alternative or supplement to WiFi. ww.signify.com


A new range of narrow angle, surface-mount LEDs has been introduced by OMC, in a variety of package styles and all popular LED wavelengths. The new SMD emitter series features integrated lenses moulded into the package, which provides a 300


output beam.


Applications for visible wavelengths include signalling and indication, in which the beam needs to be visible over greater distances, while the company’s infrared wavelength versions are used for sensing and data- communication over greater distances and with higher precision than using standard, wide-angle SMD components. Traditional through-hole (non-surface-


mount) LEDs are commonly produced with narrow output angles as the LED body is generally moulded around the leadframe using an optical epoxy or silicone. The LED body itself then acts as the lens, focusing the light into beam angles as narrow as 50 300


, with being a common requirement for many


GRAPHENE NANOFLAKE-BASED FILMS DEVELOPED AS THERMAL INTERFACE MATERIALS


Researchers at Chalmers University of Technology in Sweden have developed a new approach to cooling electronics using graphene nanoflake-based film. Theoretical studies have indicated that the graphene- based thermal interface materials can outperform those with carbon nanotubes, metal nanoparticles and other fillers owing to graphene’s geometry, mechanical flexibility and lower interfacial thermal resistance at the graphene–base material interface. XG Science have semi-commercial results improving the


thermal conductivity of polycarbonate using graphene nanoplatelets, with higher aspect ratios yielding better results, according to IDTechEx Research report Graphene, 2D Materials and Carbon Nanotubes 2016-2026. Johan Liu, Professor of Electronics Production at


Chalmers University of Technology in Sweden, and his team described experiments in which they managed to increase the efficiency of heat transfer by 76 per cent. The graphene-based film was enhanced by adding functionalised amino-based and azide-based silane molecules. They are now getting closer to pilot-scale production.


There are many potential uses of this kind of film. There has been an increasing interest in new and advanced materials for thermal interface materials (TIM) and heat conduction in all areas of the electronics market, including aerospace, automotive, consumer, communications, industrial, medical, and military.


Aiping Yu at the Centre for Nanoscale Science and


Engineering, Departments of Chemistry and Chemical and Environmental Engineering, University of California Riverside has researched Graphite Nanoplatelet−Epoxy Composite Thermal Interface Materials. Fully exfoliated graphene has been shown to outperform SWCNTs. Further improvements can stem from improving the chemistry between graphene and the host polymer. Graphite has been commercially available as a TIM for 10


years. It does not change with time or temperature cycling by releasing volatiles or creeping. This means in LED lighting applications there is no fogging. The high stability means it is used in chip-testing equipment. It can work at higher temperatures than polymeric TIMs, so enables the performance of higher power density lighting displays. It is electrically conductive, so for some applications a dielectric coating must be used, to make it electrically insulating and prevent short-circuiting. Pyrolytic Graphite Sheet (PGS) is a thermal interface


material made from a highly oriented graphite polymer film. It is synthetically made and has high thermal conductivity (700-1950 W/m.K). It is very thin, making it suitable for providing thermal management in limited spaces, and very lightweight. This material is flexible and can be cut into customisable shapes.


www.IDTechEx.com


indication and sensing applications. However, with the move to surface-mount components, some design versatility was lost as the LED body is generally injection moulded from non-optical material which is pre- manufactured before the LED die is mounted, and does not therefore form a lens in the same way. As a result, the majority of SMD packages do not incorporate any lensing, emitting light in a wide beam angle which generally exceeds 100°. Using a proprietary post die-mount


encapsulation process, OMC is able to cost- effectively integrate narrow angle lensing into a range of surface-mount emitters, and can now offer 300


beam angles for all standard


LED wavelengths, including infrared. OMC’s Commercial Director, William Heath


says: “Providing a clear human-machine interface is vital, as is ensuring precision and accuracy in a sensing system, and so the selection of the correct light-emitting components is a key design task. Narrow angle SMD LEDs are very much in demand across a wide spectrum of applications, such as sensing and communications, signalling and indication, but are less commonly available than wide angle devices, particularly for custom wavelengths and CCT/CRIs. This new series of 300


surface-mount LEDs opens up


design possibilities for engineers, and in addition to standard devices.” www.omc-uk.com


30 NOVEMBER 2018 | ELECTRONICS / ELECTRONICS


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