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Luminosity check: LED market grows, but higher-brightness apps need manufacturing boost |
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Nov 26, 2007 at 12:47 PM |
A new report reveals that although the light-emitting diode (LED) sector continues to experience gangbuster unit-volume growth, industry revenues are only increasing in single digits, and high-brightness and ultra-high-brightness LEDs (HB-, UHB-LEDs) need advanced production technologies to achieve their potential.
Yole Development and the European Photonics Industry Consortium have jointly issued a market study focused on LED manufacturing and technologies, which forecasts that the overall LED market will produce 40 billion devices and hit $4.7 billion in 2007, with low-end applications accounting for about 83% of the total, according to report author Philippe Roussel of Yole.
"The market is still dominated by portable device backlighting applications (mobile phones, PDAs, GPS, etc.), but higher-brightness LEDs are strongly expected to address other very promising markets, like automotive, LCD display backlights, and finally, general lighting," he told Chip Shots. "Only higher LED luminous efficiency will open the general-lighting market doors."
He says that recent announcements from LED manufacturers show some very impressive results on the lumens per watt efficiency parameter, with as high as 150 lm/W proven in the labs (although he cautions that these results were achieved with low-current operation, generally 20 mA). Roussel points out that the "efficiency of an LED is strongly linked to the input power: the higher the input power, the lower the efficiency. No more than 70 lm/W has been demonstrated...using high-power LED (>1 W)."
"Today's high-power LEDs are generating an average of 75% of heat versus only 25% of light," he continues, citing "several parameters that have to be dramatically improved, such as internal quantum efficiency, electrical losses, extraction efficiency, and phosphor conversion quality." In order to achieve these step-function improvements and create 150 lm/W LEDs that generate more than 50% of light over heat, new volume manufacturing technologies must be developed and implemented.
Roussel lists key manufacturing technologies already being used or investigated: new growth-material substrates, laser lift-off and temporary bonding, flip-chip with reflecting back-contacts, transparent top-contacts, photonic crystal and surface texturing, dicing/scribing, binning, and UV LED and RGB phosphors' composition/deposition.
Advanced nanopatterning of photonic crystals can be done with a combination of deep reactive-ion etching (DRIE) and nanoimprint lithography (NIL), a techique which will lead to increased extraction efficiencies, according to Roussel. Using a whole-wafer template, the can imprint patterns the entire substrate in one step, with 50--300 nm resolution and 250-nm depth, at a cost of <20 cents per wafer and a throughput of at least 20 wafers per hour. Production time-to-market is expected by next year.
Molecular Imprints and Obducat have both sold NIL tools into the LED space. During a panel focused on nanoimprint and printed electronics technologies that I moderated at the recent Small Times NanoCon event, company CEOs Mark Melliar-Smith (MII) and Patrik Lundstrom (Obducat) agreed that they expect between 30 and 50 NIL tools to be sold to HB-/UHB-LED manufacturing concerns over the next five years.
Several different thin-wafer handling solutions are available, says Roussel. The techniques are split between those that use temporary bonding and those with no intermediate layer. The temp-bonding camp includes those with and without a rigid support carrier, and those that employ wax (TEL) or adhesive tapes with a thermal, solvent, or UV release (EV Group, Suss). As for those approaches that don't require an intermediate layer, techniques vary between those using vacuum forces or rigid borders (Allvia, Semitool) or a mobile electrostatic carrier (IZM).
One thing missing from the UHB-LED success spectrum is green, as in green emitters. There is what Roussel calls a "green gap": "Efficient green emitters at 555 nm are required for several solid-state lighting applications, including digital light processing projectors, large-scale projection systems, color displays, and controllable RGB (red, green, blue) light. A green gap, however, falls between the two LED device material systems: aluminum indium gallium phosphide (AlGalInP) and gallium indium nitride (GalInN) that are used to produce visible-spectrum solid-state light sources." The gap "will need to be filled to achieve performance goals for general illumination."
Bridging the green gap should help the LED community more than double revenues over the next five years. Yole and Epic expect the global market to near 100 billion units and top $10 billion in sales by 2012, with the HB-/UHB-LED segment accounting for more than $4 billion of the total---a not-insignificant amount of green of another sort.
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