Category Archives: LED Packaging and Testing

by Dr. Guillaume Chansin, Senior Technology Analyst, IDTechEx

Quantum dots have been developed since the early 80’s but it is only recently that they made an appearance in consumer products such as TVs and tablet computers. IDTechEx Research has published a new market report on quantum dots titled “Quantum Dots 2016-2026: Applications, Markets, Manufacturers”, and as part of this study we have looked at their impact on the display industry. Is this the technology that will enable LCD to rival OLED?

Expanding color gamut

The key selling point for quantum dots is that they enable a much wider color gamut with minimal re-engineering of the LCD panels. They do this by modifying the backlight (and to some extent the color filters) inside the LCD stack.

A conventional LCD backlight uses ‘white LEDs’ which are really blue LEDs with a yellow phosphor. As a result, the white light that is produced has a strong blue peak and much weaker red and green components.

Quantum dots can be used as “downconverters”, the same way that phosphors convert blue wavelength to longer wavelengths. They key difference is that quantum dots have very narrow emission spectra and the wavelength can be tuned by changing the size of the dots. In other words, with quantum dots it is possible to have strong emission peaks in all three primaries: red, blue, and green.

The ideal solution would be to deposit the quantum dots directly on the LED (“on-chip”). But the current generation of materials degrade quickly at high temperature so they need to be physically separated from the chip (future generation materials may enable ‘on-chip’ thanks to high heat and moisture resistance).

Two workarounds are currently available. The first one is to place a tube filled with quantum dots between the LEDs and the light guide plate. QD Vision is the company commercializing this solution. While the tube can be fitted in large displays, it is not the best solution when it comes to mobile displays. The picture below shows an iMac retrofitted with a tube by QD Vision.

Source: IDTechEx Research.

Source: IDTechEx Research.

Back in 2013, QD Vision partnered with Sony to launch the first quantum dot LCD TV. QD Vision has now found more partners, including TCL launching a range of TVs and Philips commercializing the first quantum dot monitor this year.

The other integration option is to add the quantum dots as a film, an approach designed by Nanosys. The company has partnered with 3M to offer a diffuser sheet loaded with quantum dots. Because the diffuser sheet is part of a conventional backlight anyway, the display manufacturers do not need to change anything in the design of the backlight: the 3M solution is a direct drop-in replacement. Amazon was the first customer when it launched tablets with premium displays (the Kindle HDX).

The cadmium question

Quantum dots appear to offer a simple way to dramatically improve the performance of LCD panels. But there are some challenges to get the technology adopted.

First, the cost. A quantum dot film can add a significant cost to the display panel. Using tubes from QD Vision is probably more cost effective which is probably why several Chinese TV manufacturers are adopting this solution.

Second, consumers will have to be convinced that it will be worth paying a premium. Supporters of quantum dots say that it is currently the only way to obtain TV displays that are compliant with the Rec. 2020 standard. But while the specifications are impressive, it is worth noting that most consumers are not aware of the limitations of their existing LCD devices (whether TV, laptop, or tablet).

Third, the best quantum dots are made with Cadmium, an element which is usually banned in the European Union under the RoHS regulations. QD Vision and 3M have requested an exception to introduce cadmium in TVs because of the benefits in terms of lower energy consumption (thereby reducing carbon emissions). But some organizations, including Nanoco, are calling for the exception to not be extended. Nanoco supplies indium based quantum dots so would benefit from a complete ban on cadmium. Some are quick to retort that Indium is a potential carcinogen and might also be banned in the future.

While this debate is much needed to fully assess the risks, there is no denying it has also been damaging to the whole industry. Giving quantum dots a bad reputation is not the best way to get the technology widely accepted.

Nanoco has licensed their cadmium-free quantum dots to Dow Chemicals. But the optical performance of these quantum dots is not on par with the ones made with cadmium. The company believes that eventually they will be able to offer a similar level of performance. Meanwhile, Nanosys has also started to produce cadmium-free quantum dots and has licensed their technology to Samsung.

QLED as the next generation OLED?

While the main focus is currently on enhancing backlights for LCD panels, some are already looking beyond. Quantum dots can also be used to make emissive displays. So-called quantum dot LED (QLED) are similar to OLED with an active layer made with quantum dots.

Market forecast for quantum dot devices and components (Source: IDTechEx report “Quantum Dots 2016-2026: Applications, Markets, Manufacturers”)

Market forecast for quantum dot devices and components (Source: IDTechEx report “Quantum Dots 2016-2026: Applications, Markets, Manufacturers”)

This technology is still in very early stage but promises to offer the same benefits in terms of color gamut to OLED technology. QLED will in theory provide better colors and efficiency than OLED because of the narrower emission peaks. QLED can be considered as the next generation OLED.

Whether it is for downconversion or ultimately QLED, quantum dots have the potential to significantly disrupt the display industry. IDTechEx Research forecasts that quantum dots will enables a market of devices and components worth over $11bn by 2026, with a large chunk of the revenues in display applications. Quantum dots have already made serious inroads in the industry; don’t be surprised to find them in your next TV. For more information, read the full global analysis of the technology and application landscape in the report “Quantum Dots 2016-2026: Applications, Markets, Manufacturers” at www.IDTechEx.com/qd.

Orlando, FLorida – At the Meeting of the International Microelectronics Assembly and Packaging Society (IMAPS 2015), imec and CMST (imec’s associated lab at Ghent University) present a novel technology for thermoplastically deformable electronics enabling low-cost 2.5D free-form rigid electronic objects. The technology is under evaluation in Philips LED lamp carriers, a downlight luminaire and a omnidirectional lightsource, to demonstrate the potential of this technology in innovative lighting applications.

Miniature LED dome test vehicle with integrated low power LEDs. (a) Device before forming. (b) Device after vacuum forming using a 40 mm half sphere.

Miniature LED dome test vehicle with integrated low power LEDs. (a) Device before forming. (b) Device after vacuum forming using a 40 mm half sphere.

Thanks to its energy-efficiency, excellent light quality, and high output power, light emitting diode (LED) technology is becoming the sustainable light source for the 21st century. But in addition, it also allows to design unprecedented, innovative lighting solutions. Imec and CMST’s new thermoplastically deformable electronic circuits now add a new dimension to the possibilities to fabricate novel lamp designs as well as smart applications in ambient intelligence and wearables.

The innovative technology is based on meander-shaped interconnects, a robust technique to realize dynamically stretchable elastic electronic circuits including LEDs. These are then embedded in thermoplastic polymers (e.g. polycarbonate). Following production on a flat substrate, using standard printed circuit board production equipment, the circuit is given its final form using thermoforming techniques such as vacuum forming, high pressure forming or even injection molding. Upon cooling, the thermoplastic retains its shape without inducing large internal stresses in the circuits. The method, based on standard available production processes, does not require large investments, reducing the cost of fabrication. The resulting designs have a low weight and low complexity, a high resilience, a low tooling and material cost, and a higher degree of manufacturer independence due to the standard industrial practices that are used.

The production process was developed in collaboration between the industrial and academic partners involved in the FP7 project TERASEL: imec, CMST (Ghent University), ACB, Holst Centre, Niebling Formtechnologie; Sintex NP and Philips Lighting BV. TERASEL is a European effort focusing on the development, industrial implementation and application of large-area, cost-effective, randomly shaped electronics and sensor circuit technologies.

Applied Materials, Inc. today unveiled two new systems that enable the volume production of high-resolution, thin and lightweight flexible OLED displays for mobile products and TVs. The Applied AKT-20K (TM) TFE PECVD (thin-film encapsulation; plasma enhanced chemical vapor deposition) and Applied AKT-40K (TM) TFE PECVD tools deliver breakthroughs in materials engineering to deposit thin-film encapsulation barrier layers that are crucial for protecting extremely sensitive OLED devices. These systems allow display makers to replace the rigid insulating front glass on the devices and bring to market bendable and curved displays for a new generation of consumer products.

The vibrant color and low power consumption of OLED displays have driven their rapid adoption in smartphones, with flexible OLED now the fastest growing display segment in the mobile industry. The new TFE systems (20K for 925 x 1500mm and 40K for 1250 x 2200mm) address different display market segments to meet the growing demand for more versatile, thinner and lighter small- and large-area flexible OLEDs.

“The advances in size, resolution, picture quality and form factor creates considerable market opportunities for display makers to bring new flexible products to market,” said Dr. Brian Shieh, vice president and general manager of Applied’s Display Products Group. “Flexible OLEDs must be robust enough to meet the real-life demands of consumers, and the Applied AKT-20K TFE system, already in production, allows panel makers to accelerate the introduction of flexible and curved mobile applications that will change the shape of the screens we use every day.”

Key to the Applied AKT TFE product line is the capability to extend the lifetime of flexible OLEDs by offering diffusion barrier films with very low water and oxygen penetration. These high-performance films, deposited at low temperatures of <100°C, address the susceptibility of OLED material to degrade when exposed to environmental elements. In addition, the systems’ unique vision alignment technology ensures accurate and precise mask positioning and deposition, allowing display manufacturers to eliminate photolithography and etch process steps and reduce production costs.

Richard Friend of the Cavendish Laboratory, at the University of Cambridge and colleagues, have blended poly(9,9-dioctylfluorene) (F8) and a poly(para-phenylenevinylene) (PPV) copolymer known as Super Yellow (SY) and used cesium carbonate in their LED’s negative electrode to minimize quenching and give them ultrahigh efficiency devices.

Balancing the charges in the emissive layer of a polymer light emitting diode (PLED) maximizes light output from the device, the researchers report. Many teams have attempted to achieve perfect charge balance by introducing hole transport layers, that carry the “opposite” of electrons, positive holes, using electron injection layers and tuning polymer blends to improve energy transfer. There is, however, always a trade-off between electronic and optical properties. Friend and his colleagues hoped that PLEDs with ultrahigh luminous efficiency, low operating voltage and reasonably large current density should be possible.

By blending the right polymers at the right levels (in this case 9 parts F8 to 1 part SY), the team has now been able to manipulate how well holes can move, hole-mobility, by exploiting the difference in energy levels, the molecular orbitals, of the polymers. Additionally, they swapped the conventional calcium-aluminum negative electrode, cathode, system for one containing a thin layer of cesium carbonate. This layer allows electrons to be efficiently injected into the LED in order to stimulate light emission.

The team reports an ultrahigh efficiency in their device of approximately 27 candelas per amp. In comparison a device based only on SY rather than the polymer blend lights up to only about 12.5 cd/A. This “excellent performance” for the blended device, the team suggests, arises because of the intrinsic hole trapping nature of the blend system, which they explain is further enhanced by accomplishing a perfect charge balance via efficient electron injection.

“The next step could be further optimization of the performance by varying the thickness of the emissive layer and calcium carbonate,” explains team member Muhammad Umair Hassan. “Our experiments reveal that this optimization is very important.”

LG Innotek, a leading global materials and components manufacturer, today announced that the company started to produce high-power LED packages (H35C4 Series) featuring 180lm/W, which are the highest efficacy in the world.

LG Innotek improves the efficacy of high-power LED packages by 13% compared to the previous packages. The Company said that the H35C4 Series will be supplied to the global market in October.

LG Innotek used its proprietary vertical LED chip technology to optimize the manufacturing and mixing process of the fluorescent substance that produces the light for its LED chips, thus improving the performance of their LED packages. This performance is at least 10% better than all other competing products.

These LED packages boast a efficacy of 152lm/W at 85℃, 700mA under the actual usage environment of most LED packages. It beats the efficacy of competing products by 10lm/W or more.

Through optimizing “white conversion technology”, the lifespan of the product has also in-creased greatly. According to the expected lifespan based on LM-80, the LED lighting reliability evaluation criteria used by the US Environmental Protection Agency (EPA), the average lifespan of LG Innotek’s product is 150,000 hours. This is almost three times longer than existing products, which have a lifespan of 51,000 hours.

In addition, LG Innotek has established a product line-up that encompass all ranges of color temperatures and rendering, including warm white (2700K), neutral white (5000K), cool day-light (6500K), and High CRI (CRI>90). Customers can apply these products for their use in LED lighting.

LG Innotek will further stay focused on developing high performance and value product such as High Power LED Package featuring more than 5 watt and UV LED. The company also has a plan to enhance its LED lighting line-up for automotive as well mobile application.

As a response to meet the increasing demands (higher heat/brightness characteristics) of cutting-edge LED technologies, Shin-Etsu Silicones of America (SESA), a U.S. subsidiary of Shin-Etsu Chemical Co. Ltd. of Japan, has recently introduced its new optically clear LIMS (Liquid Injection Molding System) X-34-1972-3 material.

With a transparency of 95%, the new material is ideal for expanding LED applications in street lighting, automotive, and exterior illumination. Notably, its high temperature resistance, compared to thermoplastic resins, allows molded silicone optics to be positioned in close proximity to the LED light source without yellowing or cracking over extended operating life spans.

According to SESA’s North America Marketing Manager, Eric Bishop, “Next-generation HBLED systems are getting hotter as light output continues to increase. The advanced engineering properties of our X-34-1972-3 material delivers unparalleled heat resistance and clarity at these higher operating temperatures.”

Bishop also noted that the material has been tested in-house and at customers with promising results.

The optically clear LIMS X-34-1972-3 material will be on display during SESA’s open-house demonstration at their LIMSTM Technical Center in Akron, Ohio on Monday, October 12 (1:00 pm – 5:00 pm). The informal event will feature the production of 100% silicones magnifying lenses and the opportunity to network with industry suppliers and associates.

X-34-1972-3 properties:

  • Viscosity (A/B): 450/450 Pa.s
  • Hardness: 70 A
  • Tensile Strength: 7.5 MPa
  • Tear Strength: 12kN/m
  • Refractive Index: 1.41
  • Transparency: 95%

Researchers at Aalto University and VTT Technical Research Centre of Finland have succeeded in developing a method which helps to improve the relative uncertainty in measuring the luminous efficacy of LEDs from the approximate five percent of today to one per cent in the future. The results were just published in the Light: Science & Applications journal.

Thus far, solutions based on incandescent lamps have been used in photometry, i.e. in measuring light detected by the human eye, explains Tomi Pulli, a doctoral student at Aalto University.

“The photometers that lamp manufacturers use for calibrating their devices have been produced and calibrated for incandescent lamps, which results in errors when measuring the efficacy of LEDs. In our research, we used a LED lamp with a well-defined spectrum and a PQED detector, which we developed together with VTT MIKES Metrology and European partners, and whose spectral responsivity can be determined highly accurately. Therefore, there was no need for the problematic optical filters used in applications based on incandescent lamps. Indeed, accurately determining and analyzing the spectrum of the LED was the most challenging and crucial part of the research,” he revealed.

The detector used in measurements by Pulli and his co-researchers measures the illuminance of LEDs in a very small area. According to Professor Erkki Ikonen, the head of research, the next step will be to move onto measurements corresponding to real-life conditions for lighting.

“LED lamps emit light to all directions. In order to measure the luminous efficacy, we thus use a device called an integrated sphere, which takes into account light coming from different directions,” he specifies, and reminds that the history of LEDs is still short when compared to incandescent and fluorescent lamps. Therefore, there is still little information available on their actual efficacy and aging properties. Indeed, it is essential to determine luminous efficacy as accurately as possible so that such lamps can be introduced in the market that transform as much electrical energy into light useful to the human eye as possible.

So far, the portion of LEDs has been around 10 percent globally, but the amount is increasing at a rapid pace, Ikonen explains. Lighting amounts to approximately 20 percent of the electricity consumption in the world. Once the share of LEDs increases close to 50 percent, an improvement of as little as one percent in the accuracy of measuring the luminous efficacy of the lamps introduced in the market will mean saving billions of euros each year.

Imagine illuminating your home or business with flat, inexpensive panels that are environmentally friendly, easy on your eyes, and energy-efficient because they create minimal heat.

Now imagine how those panels could be used if they were as flexible as paper or cloth; the technology could be bent into shapes, fit the interior or exterior curves of vehicles, even be incorporated into clothing.

In “Flexible organic light-emitting diodes (OLEDs) for solid-state lighting” a team of researchers at Pohang (Republic of Korea) University of Science and Technology reports on advances in three key areas — flexible electrodes, flexible encapsulation methods, and flexible substrates — that make commercial use of such technology more feasible and closer to implementation. The article appears in the current issue of the Journal of Photonics for Energy, published by SPIE, the international society for optics and photonics.

Figure 9 from a new article in the Journal of Photonics for Energy is a schematic illustration of OLED structures with encapsulation: (a) conventional glass lid and (b) thin-film encapsulation. Credit: Min-Ho Park et al., Pohang University

Figure 9 from a new article in the Journal of Photonics for Energy is a schematic illustration of OLED structures with encapsulation: (a) conventional glass lid and (b) thin-film encapsulation. Credit: Min-Ho Park et al., Pohang University

OLEDs show promise as a future light source because of their thinness, light weight, energy efficiency, and use of environmentally benign materials. Companies such as Philips and LG Chemical have begun producing flat OLED panels that produce non-glare, UV-free light but very little heat, with no need for lamp shades or diffusers.

“The future trend in OLEDs is to make them on plastic substrates for flexibility, durability, and light weight. In this work, the authors review the technical challenges and solutions in this important subject,” said Franky So, Walter and Ida Freeman Distinguished Professor in Materials Science and Engineering at North Carolina State University, and an associate editor of the journal.

Min-Ho Park and other researchers at Pohang tested a variety of transparent electrodes as flexible alternatives to currently available devices based on indium tin oxide (ITO), which is brittle and increasingly expensive, and identified next steps toward making flexible solid-state lighting commercially feasible:

  • development of a flexible electrode that has high electrical conductivity, high bending stability, few defects, smooth surface texture, and high work function
  • reduction in the water-vapor transmission rate of materials used, to counter the vulnerability of OLEDs to moisture.

OLEDs produce light by sending electricity through one or more thin layers of an organic semiconductor, which may be composed of any of a variety of materials and as small a as a molecule. The semiconductor is sandwiched between a positively charged electrode and a negatively charged one. These layers are deposited on a supporting surface called a substrate, and protected from exposure to the air by a thin layer of encapsulants (traditionally glass).

The Pohang team demonstrated good electrical, optical, and mechanical performance with flexible electrodes fabricated using graphene, conducting polymers, silver nanowires (AgNWs), and dielectric-metal-dielectric (DMD) multilayer structures.

However, various obstacles still remain with these devices’ durability, conductivity, surface roughness, and fabrication cost. Current flexible substrates and encapsulation methods are being explored, with the goal of reducing cost and processing time, and increasing durability.

Researchers from Holst Centre (set up by TNO and imec), imec and CMST, imec’s associated lab at Ghent University, have demonstrated the world’s first stretchable and conformable thin-film transistor (TFT) driven LED display laminated into textiles. This paves the way to wearable displays in clothing providing users with feedback.

Wearable devices such as healthcare monitors and activity trackers are now a part of everyday life for many people. Today’s wearables are separate devices that users must remember to wear. The next step forward will be to integrate these devices into our clothing. Doing so will make wearable devices less obtrusive and more comfortable, encouraging people to use them more regularly and, hence, increasing the quality of data collected. A key step towards realizing wearable devices in clothing is creating displays that can be integrated into textiles to allow interaction with the wearer.

“Wearable devices allow people to monitor their fitness and health so they can live full and active lives for longer. But to maximize the benefits wearables can offer, they need to be able to provide feedback on what users are doing as well as measuring it. By combining imec’s patented stretch technology with our expertise in active-matrix backplanes and integrating electronics into fabrics, we’ve taken a giant step towards that possibility,” says Edsger Smits, Senior research scientist at Holst Centre.

The conformable display is very thin and mechanically stretchable. A fine-grain version of the proven meander interconnect technology was developed by the CMST lab at Ghent University and Holst Centre to link standard (rigid) LEDs into a flexible and stretchable display. The LED displays are fabricated on a polyimide substrate and encapsulated in rubber, allowing the displays to be laminated in to textiles that can be washed. Importantly, the technology uses fabrication steps that are known to the manufacturing industry, enabling rapid industrialization.

Following an initial demonstration at the Society for Information Display’s Display Week in San Jose, USA earlier this year, Holst Centre has presented the next generation of the display at the International Meeting on Information Display (IMID) in Daegu, Korea, 18-21 August 2015. Smaller LEDs are now mounted on an amorphous indium-gallium-zinc oxide (a-IGZO) TFT backplane that employs a two-transistor and one capacitor (2T-1C) pixel engine to drive the LEDs. These second-generation displays offer higher pitch and increased, average brightness. The presentation will feature a 32×32 pixel demonstrator with a resolution of 13 pixels per inch (ppi) and average brightness above 200 candelas per square meter (cd/m2). Work is ongoing to further industrialize this technology.

The world’s first stretchable and conformable thin-film transistor (TFT) driven LED display laminated into textiles developed by Holst Centre, imec and CSMT.

The world’s first stretchable and conformable thin-film transistor (TFT) driven LED display laminated into textiles developed by Holst Centre, imec and CSMT.

RayVio Corporation, a developer of deep ultraviolet (UV) LEDs and integrated solutions, announced today that they are expanding their international sales force, and manufacturing capacity. The facility expansion at the original site is scheduled to be complete by year-end.

RayVio’s current Silicon Valley headquarters houses their wafer growth, chip fabrication, packaging and test R&D and proto-typing capability. The expansion of this facility will enable RayVio to reduce cycle time and produce in excess of two million LED units annually through the installation of additional manufacturing and test equipment. Combined with its contract manufacturing strategy, RayVio is poised to keep pace with the increasing demand of the fast growing deep UV LED market.

The demand is being driven by a host of industrial and consumer applications ranging from water disinfection to consumer medical devices serving multiple global markets.

“Our proven, novel technology platform is producing best in class performance, and at the same time we are executing against our cost reduction roadmap, allowing our downstream partners to make their products a reality,” says Dr. Doug Collins, Vice President of Engineering and Operations.

Until recent achievements in both performance and cost, UV LED solutions were limited to niche applications. With the availability of high optical power UV LEDs, and competitive system level pricing to alternative UV sources, the UV LED industry is seeing a major uptake in solutions being provided.

“RayVio’s superior performance and cost effective solutions have accelerated the mass adoption of UV LED enabled industrial and consumer devices,” says Dr. Robert C. Walker, RayVio co-founder and CEO.  “With the funding we received earlier this year, we have the capital required to grow the company aggressively. By expanding our international sales force and increasing our manufacturing and research capabilities, we will be well positioned to maintain a leadership role.”

RayVio came out of stealth mode at the beginning of 2015 after closing their $9.3M series B round of financing.  They are currently sampling selected customers, and are working closely with industry leading partners in the UV LED curing, medical device and water, surface and air disinfection markets.