Chip makers and lighting specialists get switched on to new possibilities

Penetrating applications outside the mobile phone handset is no longer simply desirable for makers of high-brightness LEDs - it has become absolutely critical to ensure profitable growth.

Any doubts some may have held about that fact would have been dispelled by industry analyst Bob Steele at February s Strategies in Light conference in San Francisco. In his annual review and forecast of the HB-LED business, Steele declared that the recent rapid growth seen in the mobile applications sector had finally run out of steam.

In fact, for the first time since the dawn of the cell phone, sales of LEDs into this market sector fell slightly to $2.1 billion in 2005. A much bigger drop was only averted because many more cell phones were shipped last year than was originally expected. Since the entire HB-LED market is valued at just under $4 billion, it presents chip manufacturers, especially makers of GaN-based white devices, with a bit of a dilemma. While the still-huge mobile sector cannot be ignored, the falling prices of most white LEDs means that it will no longer generate meaningful revenue growth.

It is time to think beyond mobile phones, then. And that message was exactly the focus of this year s Strategies in Light. In the short term, it will likely be backlighting of large LCD screens that provides a new engine of growth for HB-LEDs of every hue, with automotive headlights likely to present a sizeable market for high-power white emitters beginning in the second half of next year.

But the fastest growing sector in Steele s analysis was illumination, which now represents a $250 million annual market for packaged HB-LEDs. Though dwarfed by the mobile sector, illumination offers much better profit margins for the cutting-edge chip makers, and Steele reckons that its value will quadruple by 2010.

One of the problems in solid-state lighting (SSL) has been that the makers of HB-LEDs and their potential customers in general lighting have not really been on the same wavelength. However, this communication problem is now showing signs of being overcome.

At the San Francisco conference, Niels Haverkorn from Philips Lighting described the chip and lighting communities as being at the "shaking hands and meeting" stage. Leonard Hordyk from TIR Systems, a Canadian lighting company that has focused on solid-state illumination in recent years, described two separate industries with different priorities: "The SSL industry is technology-focused, whereas the general lighting industry is application-focused."

Part of that distinction is the different view of technological innovation, necessary though it is. In the LED chip world this innovation is regarded as critically important, as the efficiency of new devices and the cost of each emitted lumen is pushed to the limit. In the lighting industry s view, such innovation can be a double-edged sword, however: "The semiconductor [innovation] life-cycle is very, very short," explained Hordyk, contrasting the cutting-edge-to-obsolescence- in-two-years world of Moore s Law with the much longer life-cycle inherent to lighting. "Whereas we [the lighting industry] want the same components to be available in 10 or 15 years time. The challenge is to bridge that gap."

Where lighting is focused on industry standards, long product cycles, standard color temperatures and light distribution, the LED industry is more familiar with proprietary standards, short product life-cycles and limited color and light distribution. So says Hordyk, although he is confident about future progress: "Over the next five years, we will be surprised by the number of applications enabled by SSL."

Now in full control of Lumileds Lighting, Philips is a critical player with a big foot in each side of the industry. Its current vision for SSL is to exploit the characteristics of LEDs in a way that adds extra atmosphere or "ambience" to the normal lighting experience - for example in the retail sector by responding to the likely mood of shoppers throughout the day by changing the light accordingly. Philips is also a big player in the medical industry, and hospitals are another environment where Haverkorn sees this kind of mood-altering light as a major application area.

Both of these applications could be seen as special projects outside of the more general residential illumination sector, and Haverkorn expects five more years of this type of activity before SSL moves into general use through what he described as the "unprecedented paradigm shift" offered by LEDs - a development in an industry that is simply not used to such rapid change.

Even when that does happen, the HB-LED industry should not view its produce as a replacement for the light bulb. "SSL will have a huge impact, but the light bulb won t go away," commented Haverkorn. "After all, people still buy candles over a century after the bulb was invented."

Haverkorn and Hordyk both see the tunability of white-light illumination as perhaps the key attribute that will allow it to make an impact in the home. At Strategies in Light, Hordyk demonstrated the power of tunable white light using TIR s 1000 lm LEXEL SS lighting system. Unlike conventional illumination, where the color temperature of the light source changes when the lamp is dimmed, the tunability of TIR s system means that the color temperature can be maintained independent of brightness, thanks to a feedback mechanism. Alternatively, the color temperature can be tuned according to preference over the course of the day and night.

Compared with recent years, the Strategies in Light meeting was less focused on laboratory-based chip innovation, with a greater emphasis on production devices, standards, test procedures and calibration. Though subtle, the change may indicate a maturation of the SSL business. Undeniably important though the lm/W metric is, many other factors come into play with the subtleties of general lighting, a fact that Haverkorn was keen to stress. His view is that there is no real lm/W "tipping point" at which SSL suddenly becomes viable, because there are so many other factors that contribute to illumination.

While Cree, Nichia and Lumileds have all been keenly promoting their latest progress recently, their emphasis has been on production devices rather than any "hero" results from the laboratory. Lumileds launched its latest high-power (around 3 W) K2 LEDs in late January. The white versions of K2 emit up to 140 lm, and Lumileds SSL offering is now based around these devices.

Meanwhile, Nichia has developed a 100 lm/W efficacy lamp based around its 6 lm output devices that operate at 20 mA, and plans to begin volume manufacturing of these small chips later this year. Having reached the milestone earlier than expected, Nichia has adjusted its technology roadmap and now plans to pass 150 lm/W in 2007.

Nichia s US rival Cree has made similarly high-efficacy devices in the laboratory, but is focusing on mid-power designs when it comes to general lighting applications. According to Cree s Mark McClear, it is the 1 W devices that offer the "sweet spot" combination of good lm/W efficacy, overall brightness and manageable thermal effects: "350 mA (1 W) is the optimal drive current for light output, power dissipation and the overall cost and complexity of the design," said McClear. Rather than record laboratory results for LED chip efficacy, Cree has instead talked up its production XLamp packaged devices, which produce 47 lm/W at 350 mA.

Although Cree s view of the "sweet spot" was not shared by everyone at the February conference, it does appear that the company is finding some success with the approach. For example, its 1 W XLamp products are now featuring in a range of residential luminaires made by the lighting specialist Permlight Products. The Permlight "Embryten" fixtures are designed for use in hallways, stairwells and bathrooms, and come with a consumer-friendly price tag.

Permlight buys both Nichia and Cree chips for its luminaires, but because of subtle differences in the white colors produced, it uses them for different types of applications in the home. Cree s XLamps feature in lamps used to illuminate floors, stairs and counters, whereas products incorporating Nichia chips are used in ceiling lights because the warmer white color from the Japanese company is said to work better with natural skin tones.

Unsurprisingly, California is at the cutting edge of residential SSL, with high-end homebuilders now incorporating LED lighting into new-build houses as a matter of course. Permlight s Fernando Lynch says that all types of LED fixture - interior and exterior - are now available. He thinks that SSL has passed the "litmus test" already, offering those who install the products a pay-back time of just 24 months on reduced energy bills.

Progress Lighting - one of the leading residential lighting companies in the US - agrees. It is launching a range of LED-powered products featuring Cree and Nichia chips this summer. "Now is the time for LED systems to illuminate our homes - not two to five years from now," says Jim Decker, vice-president of brand management at Progress.

Some new state laws could also help that penetration. Title 24 in California dictates that up to 50% of the lighting in new homes must come from high-efficacy sources such as LEDs and halogen lamps. Even more recently, the title 22 law on hazardous waste has added further LED-friendly restrictions by outlawing unauthorized dumping of mercury-containing fluorescent lamps.

With the respective priorities of the lighting and LED industries now becoming clearer, the future manufacturing supply chain of SSL is becoming more defined. Communication between the two is clearly an essential part of that process. Bill Kennedy from GaN LED specialist Toyoda Gosei is one of many to have issued a rallying call for interested parties to join the SSL section of the National Electrical Manufacturers Association industry group to ensure that the improved communication throughout the supply chain continues.