Electronics Production | December 03, 2009

New material technologies are helping the growth of the lighting industry

Lighting technology is rapidly evolving with design and energy saving features being the fundamental drivers of the industry Many people will not know that the electroluminescence effect was first discovered at the beginning of the last century, but the manufacturing and material technologies were not there to exploit the discovery.
It took another 50 years before all the technology came together to launch the first LED. Initially it was just used as indicator lights for electronics, but since then LEDs have evolved into a major lighting technology that may change the future of general illumination.

LED encapsulations
Since the first introduction of LED’s in the late 60’s, tremendous improvements have been achieved, both in efficiency, colours and in lifetime. The early models came in pale yellow-amber colour with light output efficiencies of < 0.1 Lumen/watt, then later green and red LED’s were introduced and in the mid 90’s the first blue LED’s arrived, paving the way for white lighting.

Today efficiencies are up to 150 Lumen/watt and the lifetime is currently 30000 – 100000 hours, thus enabling LED to become the next generation of lighting. But all this progress had to deal with one critical limitation - the encapsulation and how to protect the LED from the environment.

Encapsulation materials based on proven Epoxy chemistry have been developed which could withstand the harsh conditions that often surround these LED’s. They must have UV and heat stability (LED’s chip temperatures can rise to140°C) and it is essential that there is 100% transparency with no yellowing of the encapsulation materials. Furthermore, good adhesion to a range of different substrates is a must, together with low curing stress and low ionic content of raw material features.

White solder masks
The requirements for a highly reflective white photosensitive solder mask are not only its appearance which helps to ensure that there are no short cuts in power, but also how it behaves when applied. Chemical resistance against immersion in tin and nickel gold chemicals and low discoloration after multiple soldering processes are essential.

In addition high resolution capability, good protective power with thin resistant layers and long term thermal resistance (2000h at 120°C) are standard for high reliability applications. These features – in Huntsman’s Probimer range for example – are particularly important in sectors such as automotive where the protection of the electrical circuits in all weather and temperature conditions are as critical as the protection of the electronic appliances from the heat of the car engines.

LD flex dielectrics and adhesives
Based on 100% flexible epoxy technology, Probelec LD flex products are used as dielectric insulation adhesives for lightning substrates. Applications vary for bonding substrates of various kinds like copper, aluminium, polyimide, polyamide, FR-4 and others. Standard products have a thermal conductivity of around 0.4 W/ mK but new developments will be of improved thermal conductivity.

Probelec LD Flex products are applied with standard well established application and process technologies. Normally the products are applied with standard screen printing or roller coating technology in thickness between 15-100 ÎĽm. After low temperature drying they form a tack free surface with good planarisation properties which can then be handled and laminated to the second substrate.

The Future: OLED’s and integration in Araldite HFC flexible composites
Energy saving in lighting applications is a main trend in the modern architectural world and in the building industry. Lighting consumes a staggering 20% of the global electrical energy consumption, therefore energy saving lighting technologies are on the rise and the most recent and most promising of these technologies are OLED's.

OLEDs are paper-thin, flexible and lightweight devices consuming up to 70% less energy compared to conventional light sources and making these the prime candidate for the next generation of lighting.

However, there has been one critical step to overcome: OLEDs are sensitive to moisture and even to oxygen and have to be protected from these in order to maintain a long lifetime. Therefore the success of OLEDs as a mass market product for general lighting and display hinges on the device encapsulation technology.

Huntsman is a member of the “Fast2Light consortium”, sponsored by the 7th framework programme of the EU. This consortium develops large area deposition processes for fabricating cost effective, roll-to-roll light emitting polymer OLED foils. In this collaboration, Huntsman is developing a new OLED barrier material that will significantly prolong the lifetime of OLEDs.

By integrating OLEDs into composite parts and combining the advantages of flexible, durable composites with the properties of thin, flexible, large surface OLEDs, new possibilities for designers and engineers are created and will be implemented in commercial products soon. Composites from now on can have additional functions.

Corporate logos, brand names or warning signs can be displayed; for example on the spoiler of a sports car or motorbike. Interior designers can add light sources onto flat carbon surfaces; for example on furniture; aerospace or on car interiors. And for the creative sports designer, he can add safety features as well as fashion light sources to items such as skis, snowboards and yachts.

When one considers the functionality, ergonomics and safety benefits of the combination of the two new technologies – Araldite HFC and Flexible Light Emitting Foil – the list of possible applications is endless.

Author: Dietmar Leibrock, Regional Sales Manager (Germany) at Huntsman Advanced Materials
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