Category Archives: LED Manufacturing

Rolla, MO-based Brewer Science introduced a line of conductive CNT ink materials that are surfactant free, require no additional rinse steps, and are compatible with a broad range of printed electronic substrates. Cure temperatures for desired conductivity results are between 115°C and 130°C. Inks with high concentrations of CNTs in low-viscosity solutions are available in aqueous and solvent-based systems, giving them broad compatibility and enabling the design of inks for a broad set of application technologies such as sensors, displays, and packaging integration. Formulations are available for Optomec’s Aerosol Jet® technology systems, Fujifilm Dimatix’s materials printer DMP-2800, spray coating, and drawdown bar coating. 

These CNT inks have achieved sheet resistance of 300 ohm/sq for 85%T (optical transmission) at 550 nm for transparent conductive applications.  For conductive trace applications, sheet resistance of 1 ohm/sq and conductivity of 75,000 siemens/meter have been achieved.  Films produced with these inks on polyethylene terephthalate (PET) have demonstrated both high adhesion and mechanical flexibility. Both adhesion and conductivity remain stable after repeated folding of the CNT-coated PET.

“This robust performance will enable flexible printed electronic device applications,” “These solutions contain no surfactants and require no additional post-process rinsing, which will speed commercial adoption by eliminating the cost of the extra rinse process steps and preventing generation of a CNT-contaminated waste stream,” said Jim Lamb, Director of Brewer Science’s Printed Electronics Technology Center. “Although we designed these materials for plastic printed electronics applications, they are also compatible with a wide range of substrates such as paper, glass, silicon, and metal.”

Materials are developed by Brewer Science’s Printed Electronics Technology Center as part of its CNT materials, applications, and device prototyping services at the Jordan Valley Innovation Center in Springfield, Missouri. “Brewer Science is focused on bringing the unique properties of CNTs for commercial electronics applications to customers in the next three to five years,” added Lamb.

 

November 12, 2012 – Wide bandgap semiconductor materials such as gallium nitride can significantly outperform traditional silicon-based devices in power electronics and light-emitting diodes (LEDs). On the other hand, they’re also vastly more expensive ($1900 for a 2-in. bulk GaN substrate, vs. $25-$50 for a 6-in. Si substrate), and silicon has the advantage of being easily integrated into volume manufacturing. So where’s the midpoint where GaN’s capabilities and extra costs align to make it the technology of choice, and for which application?

"The future of bulk GaN is going to come down to how it faces off against silicon substrates," stated Pallavi Madakasira, Lux Research analyst and the lead author of a new report which breaks down the manufacturing costs for ammonothermal and hydride vapor phase epitaxy (HVPE) processes for making bulk GaN, as well as for GaN epitaxy on both silicon and GaN substrates, and determined where the price/performance trade-off will land. "Bulk GaN wins in laser diodes and it can become relevant in LEDs and power electronics by boosting yield and performance."

Among the report’s findings:

— HVPE is the cheaper alternative. Costs for ammonothermal substrates (2-in.) will fall by more than 60% to $730/substrate in 2020. That’s a steeper curve and to half the anticipated cost of 4-in. HVPE substrates, which are seen falling 40% to $1340/substrate — but HVPE’s larger size from which more chips can be yielded makes it the more economical choice, Lux says. (It’s a mantra that has always driven, and continues to drive, cost reduction efforts in semiconductor manufacturing.)

— Performance boost is key. Bulk GaN can overcome high cost by boosting performance — lumen (lm) output in LEDs, or volt-amp (V-A) capacity in power electronics — by allowing the use of smaller dies and providing higher yields. In LEDs, GaN can match silicon with a 380% relative performance — an ambitious but realistic goal. For power electronics, performance at 360% of devices on silicon makes bulk GaN a winner.

— New materials are on the horizon. Emerging materials such as aluminum nitride (AlN) are ideally suited to very low wavelength, ultraviolet LED, green laser diode, and high-switching-frequency power electronics applications, and can be an effective alternative to bulk GaN.

GaN-on-silicon as a substrate will continue to proliferate as the low-cost option for wafers. Bulk GaN (GaN-on-GaN), while costing more, can be competitive at the device level under certain conditions, such as laser diodes. In other applications such as LEDs and power electronics, though, "it must race to become relevant" by proving it can make devices cost-competitive through higher yields and performance.

Substrate and epitaxy cost breakdownfor GaN-on-silicon and GaN-on-bulk GaN. (Source: Lux Research)

November 8, 2012 – Fujitsu Semiconductor says it has built a server power-supply unit with 2.5kW of output power using gallium nitride (GaN) power devices built on a silicon substrate, suitable for high-efficiency power supply units, and will ramp volume production of the GaN-based power devices in late 2013.

Compared with conventional silicon-based power devices, GaN-based power devices have lower on-resistance and can perform high-frequency operations, enabling more compact power supply units with improved conversion efficiency. Efforts to develop GaN-based devices for power applications have gathered momentum in recent months:

Fujitsu says it has been working on GaN since 2009 and started sampling the technology with select partners in 2011; since then it has been optimizing them for use in power supply units. Key to that work has been collaboration with Fujitsu Laboratories in several key initiatives: process technology for growing high-quality GaN crystals on a silicon substrate, optimizing the design of electrodes to control the rise of on-resistance during switching, and devising a circuit layout for power supply units that can support high-speed switching of GaN-based devices.

The fruits of those efforts are a prototype server power-supply unit with a GaN-based power-factor-correction circuit that achieves power output of 2.5kW — enough to be suitable for use in high-voltage, large-current applications. The company says it has established a 150mm-wafer volume production line at its Aizu-Wakamatsu plant, and will begin full-scale production of GaN power devices in the second half of 2013.

Efficiency comparison between Fujitsu’s GaN power device and
conventional Si-based power device. (Source: Fujitsu Semiconductor)

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November 2, 2012 – OLED revenues are currently being driven by display applications (e.g. smartphones), but there’s a new battleground slowly emerging: OLEDs for lighting applications where the technology could offer some advantages in design and efficiency for some applications — if panel makers are willing to make some sacrifices, according to a report from Yole Développement.

Conventional LED technology has paved the way in solid-state lighting, and has a large headstart; OLED has to overcome high costs and current lower efficiency, which are hampering market adoption and penetration. The firm sees OLEDs for lighting making initial inroads in specific lighting applications (automotive, general lighting) and in niche specialty and high-end lighting where it can offer some differentiation in design options. To crack more traditional lighting markets (commercial, office buildings, etc.), however, OLED technology will have to advance the technology and expand across different niche markets to achieve economies of scale and will decrease costs. Yole pegs this happening sometime in 2014, with the rise of larger substrates and better process control.

Pars Mukish, technology & market analyst for LED & OLED at Yole, then foresees an astonishing growth projection for OLED lighting panels: from a $2.8M market this year (2012) to nearly $1.7B by 2020, with general lighting applications representing more than 70% of that business.

OLED panels revenue for lighting applications. (Source: Yole Développement)

That won’t come easy, though. There are a number of materials and OLED structures being explored and in production, tweaked to improve performance and lifetime and also decrease manufacturing costs. Polymer materials for OLEDs continue to struggle (vs. small-molecule OLED materials) in demonstrating their capabilities to lower costs and improve performance to production-acceptable levels. Rigid glass is still the go-to substrate for OLED lighting panels, but work continues on other flexible OLED technologies including roll-to-roll processing, ultrathin glass, and encapsulation options.

To have a chance at fulfilling the aforementioned growth expectations for OLED lighting, OLED panel makers have to quickly identify the winning technology approaches and time-to-market strategies. "New business models are mandatory as the traditional lighting industry will be reluctant to integrate new technology as it could eat away at margins — OLED cost directly impacts the cost of OLED-based luminaires," points out Milan Rosina, Yole’s technology & market analyst for OLED & photovoltaics. The kicker: both the new OLED technology and its integration into production are brand-new to panel makers, who are unlikely to sacrifice existing LED lighting sales and complicate production just to deploy a new technology, he notes.

Thus the key to OLED technology’s future in more mainstream lighting applications, the Yole analysts say, boils down to how and when panel makers can establish vertical integration strategies and figure out how to push the new technology through existing distribution channels. And above all, find that "spark" niche market (or markets) that will pave the way to economies-of-scale, which will open up the conversations to convey opportunities and advantages for OLED technology in general consumer lighting applications.

FlexTech Alliance announced the completion of a development project with Etched in Time, Inc. (EITI), for a plasma etch system that is compatible with a wide array of roll-to-roll equipment.  The result of the project is a tool that can be used in the manufacture of a broad range of products including LED lighting or solar panels fabricated on plastic substrates.

The purpose of this FlexTech Alliance funded project was to create a plasma etching tool for dielectric films that offers a number of manufacturing advantages for flexible electronics. For example, plasma etching is cleaner than a wet etching manufacturing process due to the lack of chemicals to dispose after use. Additionally, incorporating the system into a roll-to-roll process allows large area and flexible products to be fabricated at low cost.

After the successful system development, the final step of the project was installation of the EITI plasma tool into the roll-to-roll flexible processing equipment at Binghamton University’s Center for Advanced Microelectronics Manufacturing (CAMM), where the follow-on work will take place of fine tuning processes with the new system for different materials.  

The new tool has gained commercial traction since the project completion. For example, a joint venture has been established between EITI and the Solar Product Lab (SPL) at Arizona State University to build and install a demonstration tool to etch silicon nitride for solar cell production.
“Not only will this project refine the manufacturing process of printed, flexible electronics through the continued work at CAMM,” commented Michael Ciesinski, CEO of the FlexTech Alliance. “Etched in Time has also been very resourceful using the results of this project and their design and build expertise to adapt the technology for commercial markets.”

Additional applications of the tool include texturizing a silicon surface during the manufacture of solar cells fabricated with multi crystal silicon, a material currently in wide industry use.

October 15, 2012 – Researchers at the National Institute of Advanced Industrial Science and Technology (AIST) and the Chemical Materials Evaluation and Research Base (CEREBA) say they have evaluated molecules within a sealed organic light-emitting diode (OLED) in operation using laser spectroscopy, measuring both selectively and nondestructively

Their work, published in August in Applied Physics Letters, involves a method improving upon a laser spectroscopic technique to measure molecular vibrations at the interface of an organic layer inside the OLED device — specifically, evaluating a signal enhancement phenomenon that occurs at the interface with a concentrated electric field.

The problem with evaluating OLED devices, as with many other types of sensitive electronics components: the method itself often involves destroying the device or impacting its performance (e.g. introducing contaminants). Measuring OLED device degradation, particularly in devices with multiple and overlapping internal layers, is particularly difficult — yet much more needs to be known about the inner workings of OLED layer degradation to learn how to extend the device’s lifetimes for application in displays or lighting.

Key to AIST’s work is using "sum frequency generation" (SFG) spectroscopy, which employs wavelength-tunable lasers to collect information on specific interfaces of organic substances in complex organic devices. Specifically it has pursued two-color SFG spectroscopy to measure vibrational changes at the surface and interfaces in a solid; one tunable visible laser would still collect signals from multiple organic lasers, but implementing two lasers creates a "double resonance" that can be used to enhance and isolate signals from a targeted organic layer. They also tweaked the SFG spectrometer to maintain measurement resolution even at 1/100 laser power of conventional SFG spectrometers.

"By investigating in detail the ‘fingerprints’ of organic layers in an OLED device, the alteration and degradation of molecules in the operating device as well as the change in the electric field inside the device can be elucidated," AIST explains. Their goal is to determine, at the molecular level, the driving mechanisms of OLED devices and their degradation — and also seek ways to apply the work to other organic electronics fields, such as solar cells and transistors.

CERERA was established at AIST specifically to establish design and manufacturing technologies for OLED materials and devices, including evaluation and analysis techniques.

Top: Schematic drawing of the structure of the multilayered OLED device and the directions of the incident and emitted lights used for SFG spectroscopy. Bottom: Spectral changes in an operating multilayered OLED device, with +8 V application (light emission), no voltage application, and –5 V application. (Source: AIST)

by Mark Danna, VP of business development, Owens Design

Continuing a series of columns for SST, Mark Danna from Owens Design highlights common mistakes that can cause an outsourced partnership to fail and detail a methodology for approaching an outsourcing agreement that can minimize the risk and costs involved and help ensure a successful partnership.

October 12, 2012 – One of the toughest things about getting started on a tool development design and build project is that in most cases the overall requirements for tool functionality and performance have not been focused yet. Nevertheless, the group tasked with tool development responsibility is told to get moving on the project because "we are already late." In fact, from the point of view of most of those involved, the picture of what is needed is still kind of fuzzy and none of the critical details are well-defined.

It is, however, possible to launch the project, get it off the ground, and make progress while still clarifying tool specifications and requirements. A disciplined phased approach to the program can resolve many of these open issues (technical, commercial and market-related) in the first phase of any project.

For example, at the start of most tool development projects there usually is a gap between desired tool functionality and target tool cost. The engineers want to design the tool to meet all potential market requirements and perform at the highest level. The marketing group wants a tool that meets a specific set of market requirements and can be produced at the lowest cost possible. Very early in the program a functional/cost trade-off analysis needs to be done — and well understood — by both parties before tool specifications and performance can be agreed upon and finalized. One of the most critical parts of finalizing the tool specification is to really understand how the functionality of the tool will be validated at the end of the program. Without an agreed-upon functionality test, tool performance cannot be validated and the specification is meaningless.

Unfortunately, not all tool functionality can be nailed down in the first phase of the tool development project. For some projects, it is standard procedure for final tool production launch to begin before the overall tool characterization has been completed. During this process, if overall tool functionality changes significantly, tool specification changes are the inevitable result and most likely will affect overall tool design. Going into this phase with a tool design that can accommodate a wide range of design parameters can minimize the risk of a total design restart. The trade-off, of course, is that this increase in functionality will most likely lead to an increase in overall tool cost. By thinking about these potential issues early on, it may be possible to minimize the impact of design-related change by having the ability to easily change the design to meet the tool requirements once overall tool functionality has been solidified.

A lack of clarity early on in design requirement can exist whether the project is handled as an in-house development project or is outsourced. If it’s an outsourced project, the selection of a design-and-build partner and its ability to help clarify and focus the development effort is critical to the overall success of the program. While there is always a desire in a tight economy to keep as many costs in-house as possible, the money spent engaging the right outsource design-and-build partner at the beginning is likely to end up benefiting the project budget long-term. Where a typical equipment OEM may produce a new tool every couple of years, a good outsource partner might go through this development process 10-20 times per year. As a result, this outsource design-and-build partner will have established and proven procedures that can take that fuzzy picture at the beginning of the project and put it into focus.

Time must be committed early in the development phase of a project to bring the fuzzy parameters into focus. Tool cost vs. functionality trade-offs must be well understood by all stake holders. By leveraging either in-house or outside expertise in project planning and management, as well as design input from the very beginning, one can end up saving a lot of time, money, and aggravation.

Mark Danna is VP for new business development at Owens Design.

October 11, 2012 – Soitec and Shin-Etsu Handotai (SEH) have extended their cooperation in Soitec’s Smart Cut technology with an extended 10-year licensing agreement, including a new level of joint technology cooperation, to facilitate development and wafer supply of silicon-on-insulator (SOI) wafers.

Under the agreement, Soitec and SEH will cross-license Smart Cut-related patents. SEH will continue to use Soitec’s technology to manufacture SOI wafers, and now will extend the technology to other "silicon-on-anything" materials and address a broader range of applications. (SOA is defined as any material on top of which is a thin film of plain silicon.) Soitec and Sumitomo Electric, for example, have been working to develop gallium nitride (GaN) engineered substrates for LEDs, using the Smart Cut method.

The Smart Cut wafer bonding/layer-splitting technology was developed by Michel Bruel at CEA-Leti in 1991 and spun out into Soitec in 1992. A pilot line was created in 1996, and SEH was the first company to license the technology a year later. "We have worked side by side with SEH for more than 15 years, and together we have established Smart Cut as the industry standard for manufacturing SOI," stated Paul Boudre, COO of Soitec. With an increasing need to develop new materials that can extend performance and energy efficiency for today’s (and tomorrow’s) electronics devices, "we look forward to manufacturing new products such as planar FD-SOI and SOI for FinFETs."

"We are very excited about the business opportunities for SOI products, and we look forward to working with Soitec to extend the global supply chain for new products, such as FD-SOI and SOI for FinFETs, which are showing potential benefits in mobile and embedded applications," stated Nobuo Katsuoka, SEH director, SOI process engineering department.

October 10, 2012 – Azzurro and Epistar say they have achieved GaN-on-Si based LEDs utilizing Epistar’s high-brightness LED structures and Azzurro’s patented technology for 150mm GaN-on-Si. The joint project, completed in four months, transferred Epistar’s existing LED structures built on sapphire to the GaN-on-Si material system. The companies characterized the achievement as "one step further towards implementation in mass production."

Using templates with strain engineering, Azzurro’s technology enables epitaxy engineers to quickly transfer LED structures to GaN-on-Si, the company says. A patented and proprietary buffer stress management enables better homogeneity (<4 nm wavelength homogeneity) for LED epi wafers, helping to reduce binning and increase yield.

"We are very excited about the outcome of this joined exercise which has exceeded all expectations regarding speed and cost of migration. The success helps us to utilize GaN-on-Si which is a game changer for the industry," stated Epistar chairman Lee Biing-Jye. "The technology to enable the LED industry to tap into the advantages of the volume, cost-effectiveness, and maturity of silicon foundries is ready with our strain-engineered templates," added by Erwin Wolf, CEO of Azzurro.

The promise of GaN-on-Si is to match the performance of sapphire-based devices, but using silicon equipment long commercially proven in the semiconductor industry to scale up operations, boost yields, and ultimately lower costs. In fact, the semiconductor industry is progressing toward consensus on building-block standards for automating LED production on 6-in [150mm] wafers. Toshiba is planning to ramp LED production using GaN-on-Si 200mm substrates by year’s end, through a collaboration with Bridgelux.

imec, meanwhile, has its own research program to develop GaN-on-Si power devices on 200mm wafers. Last year it produced successful wafers, and has also developed the prerequisite fabrication process with standard CMOS processes and tools. (Days ago ON Semiconductor joined that imec program, as it builds a GaN processing line in Belgium.)

October 8, 2012 – Solvay Specialty Polymers USA LLC has extended its line of high-performance polyester compounds with a new version targeting light-emitting diode (LED) TVs with higher heat and light stability.

Seeking to reduce product costs, TV manufacturers are finding ways to reduce the number of LEDs by sending more amps through the devices to hike brightness. (Another cost-lowering strategy: go the other way and give up some brightness in LED backlit models.) This raises the junction temperatures, though, and some materials can’t handle the higher heat and light output, e.g. discoloring more quickly in applications such as reflector cups.

Solvay’s new "Lavanta" 5115 WH 011 high-performance polyester line of liquid-crystal polymers, is a 15% glass fiber-reinforced injection molding compound developed specifically for LED electronic packaging applications that utilize surface mount technology. It has high reflectivity (>95%) with excellent whiteness retention even after thermal and light aging, translating to better reliability for LEDs that operate at high junction temperatures — e.g. filling very thin-walled sections required for low-profile, side-view LEDs. It also offers dimensional stability due to its low moisture absorption and exceptional weld line strength, according to the company.

The company plans to expand the Lavanta line with an enhanced version possessing even greater heat and light stability for longer product life and reliability. In addition to LED TV applications, the material is targeted for general lighting for indoor and outdoor applications.