Traditionally LEDs were viewed as an excellent lighting alternative offering significant energy savings, albeit with inferior visual performance compared to some lighting options.

Over the past few years, the energy savings LEDs provide have continued to grow at an impressive pace. In fact today´s LEDs are more than twice as efficient as LEDs from just five years ago, offering 25-30% energy savings compared to CCFLs and up to 80% savings compared to incandescent bulbs. These eye-catching energy savings have been accompanied by significant space savings and enhanced visual performance.

Key developments in LED manufacturing, specifically enhanced equipment, improved processes and superior materials, have allowed the latest generation of LEDs to provide a powerful combination of excellent LED  light output, visual performance and space savings. Let’s look at each development closer.

LED MANUFACTURING TRENDS

Enhanced Equipment 

Over the past 10 years, equipment used to manufacture LED dies has undergone dramatic improvements. LED manufacturers have shifted from class 10,000 clean room to highly sophisticated class 1,000 clean rooms for all production processes. This change ensures that no particles bigger than .5um per cubic foot are allowed inside the room as opposed to a class 10,000 clean room, where up to 70 such particles would enter the same space. A Laminar Flow Clean Room consistently pushes airflow from top to bottom from an air purified HEPA filtered machine, refreshing the air inside and further preventing contamination.

Vapor Phase Epitaxy has also helped advance LED performance. Metalorganic Chemical Vapor Deposition (MOCVD) machines are no used to create die substrates.  The multi-reactors systems that have replaced them provide up to 20% superior wavelength uniformity, while generating more consistent color performance and cost savings.

Due in large part to this enhanced equipment, the structural efficiency of LEDs has improved from 50 to 70% ten years ago to over 90% today. The enhanced structural efficiency in turn creates superior visual performance.

Improved Processes 

Two major process improvements have led to a significant increase in visual performance particularly for white LEDs. Five years ago, LEDs could only achieve a color-rendering index (CRI) of 50 to 60. In particular, there were issues with producing warm white light. Improvements in manufacturing processes and in binning have dramatically enhanced visual performance. 

To create visually appealing warm white light, several steps were added to the manufacturing process. A red die is placed in the same package as the blue die, which is then coated with a highly engineered phosphor coating, resulting in significantly better visual performance. Tweaking the thickness and consistency of the phosphor coating delivers specific gradients of white.

A second significant process improvement was the shift from sapphire substrate to thin-film based die production. Rather than growing dies in a crystal format, they are now made via a thin film process, which can be controlled on a molecular level, greatly enhancing wavelength uniformity and thus visual performance.

Superior Materials 

The wafers used to create LED dies have also undergone significant improvements in recent years. Whereas 10-15 years ago three and four inch wafers were common, today they have doubled in size. As the optimally-performing die materials are at the center, rather than at the edges of the wafer, six inch wafers produce up to twice the volume of high quality LED die chips and do so with 30 to 50% cost savings.

TRENDS IN LED PERFORMANCE 

Enhanced equipment, improved processes and superior materials have led to a higher volume of consistently high-quality LED chips for manufacturer use. These quality chips provide key performance benefits including even greater energy savings, space savings and superior visual performance all at a lower cost than was previously possible.

Energy Savings 

Whereas 10 years ago output provided was 15lm/W, today 50 to 60 lm/W can be achieved in a standard 20mA LED. Refined production processes have created 300% greater energy efficiency over the past ten years and a further 10% improvement is expected within the next three to four years.

Space Savings 

Energy savings in turn can create space savings as the same amount of light output can be generated in a much smaller package. The availability of more efficient dies and more precise technology makes it possible to create highly efficient packages that are significantly smaller than ever before. For example, 10 years ago a 15 lumen LED would require a package area of roughly 10mm where as today that same 15 lumens can be achieved in 75% less space. LEDs continue to provide 30-50% space savings compared to incandescent bulbs and compact fluorescents.

Figure 1. Technology advancements have made possible the creation of high-power LEDs that produce three times the light output as a standard LED from 10 years ago, in a package that is 50% smaller.

Visual Performance 

Previously, LEDs could only achieve a color rendering index (CRI) of only 50 to 60 compared to the over 99 CRI provided by incandescent bulbs. However, technological advancements such as the process improvements mentioned above have increased LED CRI up to 90, visually very similar in performance to lighting alternatives.

Enhanced binning procedures have also supported greater visual precision and consistency. Years ago LED manufactures would have lists of BIN codes with variations of 75nm or even higher. Today a tolerance of only 25nm is achievable. As a result, manufactures can bin in 5nm (rather than 10nm) increments allowing end users to consistently achieve precisely the color and wavelength they require.

The trend is moving toward creating a wafer of 100% optimized material with consistent wavelength performance. Today roughly 80% of the wafer is used – up from 50% a few years ago.

Lower Cost
Enhanced equipment, improved processes and superior materials have not only generated energy and space savings and enhanced visual performance, they have also generated cost savings. Over the past three to four years packaged LED prices have fallen 20 to 30%. 

Cost savings have also been generated by the emerging trend of plug-and-play packages. These modules save engineers significant amounts of time as highly efficient LED arrays are already integrated with a metal core PCB and soldering pads without the need to add resistors or split voltage.

Conclusion
Enhanced manufacturing has led to superior LED performance. This has allowed LEDs to move beyond indication lighting and into a wide range of new applications. As we learn to more fully take advantage of all the inherent potential in LED technology, these applications will continue to grow beyond the bulb into new, creative formats that allow us to interact with light in entirely new ways.

About the Author

Jonathan Domingo is a Product Development Engineer at Lumex, a leading provider of LED and LCD technology. During his seven years of fieldwork in optoelectronics, he has helped design custom LED and LCD solutions for leading brands in industries ranging from appliances to aviation to consumer electronics.