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August 2014 • SMT Magazine 37 Silicon oxide and aluminium oxide are the top choices for utilization in electronic applications. Mixed oxides and nitrides, such as silicon oxynitride, are also gaining popularity. To achieve better barrier properties, multiple layers of organic and inorganic materials have shown promise. " " LED lighting is currently hindering commercial adoption of OLEDs. Ongoing research has fo- cused on increasing the lifetime and luminous efficacy of OLED light bulbs. While laboratory experiments have delivered favorable results for luminous efficacy (more than 100 lumens/watt) and lifetime (100,000 hours), technical diffi- culties still persist for mass manufacturing and commercialization. Furthermore, printed light- ing has not been adopted as widely as printed displays. The most important factor for the potential wide-scale adoption of printed light- ing lies in the fact that it enables new form factors. OLED lighting surfaces can be made flexible, which opens up numerous possibilities of applications on curved surfaces, wearable de- vices, and so on. The devices could be made as a transpar- ent surface, so it could be used as a room divider and reflect as mirror. In addition, OLED lighting panels are compact and thin with dimmable fea- tures. In printed lighting, OLED lighting holds maximum po- tential for adoption as it is not only safe per environmental regulations, but also offers low energy consumption. Compa- nies such as Philips and Os- ram Opto Semiconductors are working on the printed OLED lighting sector. However, the cost of OLED and technical attributes such as efficiency, stability, and operation life- time will initially hinder the adoption of print- ed lighting. Printed and flexible OLED lighting is expected to gain traction in the luxury and design lighting segment where cost is of lesser importance than aesthetic features. Wide-scale adoption of such decorative lighting is expected. The other key application areas of printed electronics are in memory and batteries, which can be enabling technologies for next genera- tion wearable electronics that have garnered a lot on interest in recent years. the Challenge of Encapsulation Organic substances used in printed electron- ics are inherently prone to reacting with mois- ture and air. There is thus a need to properly encapsulate the materials. Encapsulation is a major challenge faced by OEMs. Different prod- ucts require different levels of encapsulation, which is normally measured using the water va- por transmission rate (WVTR) that is specified in grams per square meter per day. While RFID and electrophoretic displays require WVTR to be around 10-2g/m2/day, some demanding ap- plications, such as organic PV and OLEDs require the WVTR to be around 10–6g/m2/day. Various technologies have emerged in encapsulation and most are thin-film encapsulations. Glass provides the best bar- rier properties, but cannot be used for thin-film applica- tions. Moreover, the cost of flexible glass is higher than other materials and it re- quires high-temperature pro- cessing, which can affect de- vice fabrication. Polymer ma- terials, such as polyethylene terephthalate (PET) and poly- ethylene naphthalate (PEN) are normally used as the base substrate. Organic and inorganic materials are also being used for effective barrier proper- ties. Silicon oxide and alumin- ium oxide are the top choices for utilization in electronic appli- cations. Mixed oxides and nitrides, such as sili- con oxynitride, are also gaining popularity. To achieve better barrier properties, multiple layers of organic and inorganic materials have shown promise. Impurities, such as desiccant, can also be introduced in the barrier layers for absorbing water molecules in the vicinity, which enhanc- es the barrier capability. During barrier film fab- rication, pin-hole defects can arise, which affect the barrier performance. This challenge can be solved using nanomaterials that force wa- ter molecules to traverse a difficult path inside PE: tRaDItIONaL PROCEssEs ENaBLINg NEXt-gENERatION ELECtRONICs continues FEaTuRE

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