February 10, 2012 — Day 3 of the 2012 Strategies in Light conference continued the LED Manufacturing session. Presenters covered lithography for light emitting diode (LED) manufacture, advanced packaging, metrology and testing, high-performance materials, and other topics, such as the value of dimming.

First up, Thomas Uhrmann of EV Group with a review of the lithography and wafer bonding tools that they provide for HV manufacturing of LEDs. Nano-imprint is one of the applicable technologies identified on one chart, but only optical litho was discussed. Several different device structures are being scaled up in production, no longer limited to the original planar device. A variety of bonding schemes were shown, many driven by emerging 3D integration process flows. It remains to be seen whether there will be a process and materials convergence in our future.

Figure 1. Chip designs for GaN LEDs.

The subject switched to metrology and yield management with Mike Plisinski of Rudolph Technologies, focusing on epitaxial process metrology and feedback in LED production. MOCVD Epi process defects and variation are the largest LED cost drivers, impacting both yield and brightness directly.

Figure 2. Epi process defects and LED yield/brightness.

Dan Scharpf of Labsphere talked about optical testing of LEDs. Drive current, junction temperature, stray light and appropriate selection of sphere size are all important parameters for accurate testing that does places all products into the correct bin.

Ilkan Cokgor of Everlight Electronics led us into the LED Packaging session, speaking on packaging trends intended to drive down the cost per lumen. Specifically, he focused on performance and reliability improvements for PLCC packages because they are low cost but have not developed a reputation for reliability before now.

Figure 3. Advanced package — reliability improvement.

Ravi Bhatkal of Cookson took the packaging reliability story up a level to luminaire fabrication, including the introduction of SMT manufacturing methods to LED packaging. Issues in lead-free solder printing and reflowing were discussed. The talk provided some good guidance for engineers just starting to implement such processes.

Geoff Gardner, Lighting Marketing Manager for Dow Corning, talked about innovations in silicone technology as applied to LEDs. As the material most commonly used for the LED primary lens, thermal stability is critical for both transmittance and reflectance over the lifetime of the device. Silicones used in injection molding and screen printing have recently been brought to the market. The chemical physical and mechanical properties make silicones suitable if not preferred for a range of applications within LED modules and luminaries.

Figure 4. Material needs in lamps and luminaires.

Figure 5. Silicone technologies for LEDs.

Marc McClear of Cree, still well-known to those of us from the semiconductor materials business, opened the final session of the LEDs in Lighting track with The Next Big Thing. Among the discarded candidates discussed were LED droop, the green gap, remote phosphors and OLEDs. Rather, the correct answer is 3rd generation direct attach LED chip architecture as the vehicle that will deliver 200 lumens/watt for the industry. The payback time for installed fixtures will drop from 4.5 years to less than 1 year.

Figure 6. DOE LED roadmap.

Nadarajah Narendran, Director of the Lighting Research Center at RPI, gave a program overview of ASSIST, the Alliance for Solid-State Illumination Systems and Technology. In a philosophical observation worthy of “if a tree falls in the forest and no one hears it…” he opined that without a human eye to observe it, light is just another wavelength of radiation. “ASSIST recommends” is a series of publications that the organization has produced over the past decade to disseminate the research to its member companies and throughout the industry. Developing test methods, standards and educational curricula are among the ongoing activities that comprise its mission.

Figure 7. ASSIST publications.

Next on the agenda was Amy Olay (no relation) of the San Jose Department of Transportation talking about the energy savings programs associated with the city’s 62,000 streetlights with an annual operating budget of $6M. Implementation of a wireless control system in which each streetlight was its own node was chosen over hard wired designs for controlling power to and receiving operational data from the lamps. The longitude and latitude of each streetlight is known to itself, and it turns on and off based on its unique sunrise & sunset times, rather than using photocells. Warm white LEDs with a color temperature of 4500°K were found to be preferred by the public. The units could be reduced to 50% power without an adverse effect on safety or public perception. In a nod to scientific collaboration, the city can further dim these lights from midnight to 5am, which are the hours in which the James Lick Observatory above San Jose on Mount Hamilton conducts its astronomical research. The current deployment is for 2,000 streetlights, funded by federal stimulus money. An additional $30M in grants will be needed to complete the conversion to LED streetlights in San Jose.

Sam Klepper of Redwood Systems wrapped up the conference by introducing us to the digital age of lighting. Being dimmable turns out to be a significant feature of LEDs that is not fully exploited. Dimming an LED by 30% reduces power consumption by 50% with no adverse effect. Dimming a CFL by 30% reduces power consumption by only 20%, and reduces the lifetime of the lamp. The digital control system that takes advantage of all of the features of LED lighting brings with it the capability to add a number of other functions of interest to building managers with little additional effort. For example, motion sensors used to turn off lights in unoccupied rooms can also indicate room occupancy for spontaneous roving team meetings searching for an available conference room. The same sensors can provide security warnings for restricted areas or after-hours tresspassers.

Figure 8. Key challenges in facilities.

Figure 9. Commercial electricity use by building type.

Observation from the exhibition floor: I’m accustomed to walking up and down the aisles and wondering how I might use the product being exhibited to build my own product. At this show, the dominant thought was “I wonder how that would look in my living room.” In that sense, it was a bit more like Home Depot than the technology conference that it was. On the other hand, it is so much more interesting to see all of the ready-to-install luminaire designs than it is to see bin after bin of bare and packaged chips and assembly components.

Next year is going to be a tough one for the LED industry, since the 2013 Strategies in Light conference will be held on February 12-14. I think it’s safe to say that not everyone will be able to get home in time for Valentine’s Day to keep peace in the family.

Michael A. Fury, Ph.D., is director & senior technology analyst, Techcet Group in North Plains, OR.

Read Fury’s other reports from Strategies in Light:

• Day 2: LED manufacturing highlights
• Day 1: LED lighting report, new start-ups

Visit the new LEDs Manufacturing Channel on ElectroIQ.com!

February 9, 2012 — Day 2 of the 2012 Strategies in Light conference, and the first day of technical sessions, began with an adrenaline rush. The challenge posed to the audience was to identify the first ever Super Bowl TV commercial to feature a light emitting diode (LED) light. The first respondent would win $100, and it took only a few mental CPU cycles for someone to correctly shout out “Audi.” The conference has over 4,000 advance registrations, with a total of 5,000 attendees expected for conferences and to view the record 170 exhibitors.

Read Fury’s report from Day 1: Strategies in Light: Day 1, LED Lighting Report, New Start-ups

and from Day 3: Lithography, direct-attach LED architectures, packaging trends

The session was opened by Ella Shum, LED practice director at Strategies Unlimited. One prognosis is that China will soon be taking over the global sign market; it commanded 87% of the W/W market in 2011. Many smart phones are going to OLED displays. It was suggested that the iPhone will not go OLED until someone other than Samsung commands the majority of OLED manufacturing capacity. Even though the LED lighting market is growing at a 20% CAGR to 2016, the LED chip market is flat (CAGR -0.2%) because of price pressure even as unit growth is strongly positive.

Ling Wu, Secretary General of the Chinese Solid State Lighting Alliance, provided an overview of their strategy as captured in the next Five Year Plan. Energy savings is the dominant driver, with a target of 100B kWh saved. The 20M rural families still without electricity are driving a market for off-grid LED lighting.

Eric Kim of Soraa, Inc. took a holistic approach to LED lighting for space illumination. Readers are referred to an article in today’s (Feb 08, 2012) Wall Street Journal on the company. Unlike most LEDs that use blue emission to pump phosphors for their range of colors, the Soraa products use violet light to pump a different set of phosphors, giving characteristics distinct from others in the market.

Editor of LEDs Magazine Tim Whitaker provided his observations on the European LED lighting industry. General lighting LED market share is just shy of 10% in 2011, in spite of being two years into a mandated conversion roadmap away from incandescents. This transition is expected to inject €20B into the European economy.

Ned Tozun of d.light Design is turning to LED solutions for off-grid household lighting in third world rural areas. There is still a surprisingly large population that has no access to electricity, or unreliable limited access. The primary means for night lighting are kerosene lanterns and electric bulbs powered by lead acid batteries that must be carried to a local diesel generator  for daily recharging. In India, the government subsidy to keep kerosene prices affordable is ~$6B, approximately the same as the national budget for education. The sociological benefits from relatively low-tech implementations of solar chargers and LED lighting at night extend to increased study time and improved health for children due to the elimination of kerosene (which is typically several grades below what is available in the US in terms of adulterated effluents).

Figure 1. Population without electricity.

Overheard mid-morning: “I’m surrounded by a bunch of technical propeller-heads talking about LED chip manufacturing and I’m not sure I can keep up.” Funny, I felt like I was surrounded by marketeers who were excited about upside market potential but had no idea what the inside of a fab looks like, at least through the morning plenary session. Fortunately, I was able to take refuge all afternoon in the LED Manufacturing track, where my propeller spun freely.

Seth Coe-Sullivan of QD Vision opened the session on phosphors with his overview of the only company focused on quantum dots exclusively for the lighting industry. Their quantum dots can operate in both photoluminescent and electroluminescent (for QLEDs) modes. The underlying physics is said to provide greater efficiency and spectral purity than phosphor technology.

Iain Black of Philips Lumileds Lighting talked about the challenges of LED manufacturing from the perspective of rapidly delivering products to market that are responsive to rather fast changes in consumer mood. One important element is to move the product customization point as late in the production process as possible, allowing many products to draw from a common substock. Lumileds manufactures on 150mm wafers; most LED fabs still run smaller wafers.

Karen Savala, President of SEMI Americas gave the supplier-side perspective on consolidation, expansion and long-term planning for LED manufacturing. Global manufacturing is normalized to 4” wafer equivalents; capacity is expected to reach 2M wafers/month this year. Sapphire LED substrates are expected to reach 50% 6” wafers in 2014, and this wafer size is where the SEMI Standards activity is focused for LED.

Figure 2. LED dedicated fabs, 10-year span. SOURCE: SEMI Opto/LED Fab Forecast, November 2011.

Jacob Tam, President of TSMC Solid State Lighting Ltd., explored the question of whether a large semiconductor manufacturer can accelerate LED cost reduction. He started with a very nice spider chart comparing the state of manufacturing in the two technologies. Various manufacturing and design tools were compared between the two, but in the end he remained quite silent on the details of what TSMC had in mind for its own LED manufacturing future. One expectation is that binning control will be much tighter when leveraging TSMC’s process control experience.

Figure 3. The fundamental differences between semiconductors and LEDs.

James Broderick of US DOE talked about the government-industry roadmap for improving solid-state lighting manufacturing in the US. The underlying motivator is the creation of sustainable US manufacturing jobs. The metrics call for OEM lamps priced at $5 by 2020, compared to $23 today. There are ~$45M in projects funded today, with a planned pathway to $114M. A funded KLA inspection tool tested at Philips Lumileds reduced production costs by 10%.

Figure 4. DOE funding by program pathway.

Raja Parvez, CEO of Rubicon Technology spoke about the move to larger diameter sapphire wafers. Solid state lighting is the largest consumer of their products, followed by silicon on sapphire and optical windows (aerospace). Rubicon expects 6” wafer share to be 70% by 2020, with a subsequent trend to 8”, following the semiconductor trend.

Figure 5. Sapphire wafer diameter trends. SOURCE: Yole Developpement.

LED chip manufacturers transitioning to larger-diameter substrates to reduce cost  –Several chip manufacturers announced plans to move into volume production on 6" substrates in 2011  –We have been supplying R&D volumes of 8" epi-polished wafers and are ready for high-volume production.

Abdul Lateef of Plasma-Therm talked about the advancements of front end PECVD deposition in adapting to LED manufacturing. Real time process control using optical emission interferometry is one of the innovations contributing to higher production repeatability and yield, with a control resolution of 50nm.

Michael A. Fury, Ph.D., is director & senior technology analyst, Techcet Group in North Plains, OR.

Visit the new LEDs Manufacturing Channel on ElectroIQ.com!