Utilizing UV LEDs in Manufacturing

The UV-LED market is a relatively small segment of the overall LED market. It is estimated roughly to be $30 million annually, whereas, the overall LED market is already in the multibillion dollar range. The UV-LED market is expected to grow by 30% annually to about $100 million in 2016.  This late surge is due to breakthroughs in radiant power and intensity of UV-LED that will enable the displacement of mercury-vapor lamps altogether in the future. This could be due in part to recent achievements in product flux density of UV-LED chips beyond the flux density of 4W/cm2 at different wavelengths.

In manufacturing applications, the spectral ranges that are often used reside in the UV-A (315-400nm) and UV-B (280-315nm) range. Actually, 90% of the UV LED applications are based on these two ranges. The UV-A range is used in applications such as curing of adhesives, coatings and inks. Meanwhile, the UV-B range is often used for applications such as visual inspection systems on machine vision, and detecting. And, at the lower end, the UV-C spectral range (100-280nm) is  primarily used for air and water sterilization.

Since the curing process for manufacturing applications requires large and high-powered LEDs, it is often optimal to use LEDs in the range of 385, 395 and 405 nm. These ranges are preferred due to the ability to drive the LEDs at higher power with better efficiency.

Key UV LED Features & Benefits:

• Longer Life, >50,000 hours
• Stable power output throughout the life of the LED
• Instant on/off
• Emits no heat, able to cure heat-sensitive substrates
• Non-hazardous, contains no mercury
• Consumes less power
• Slower degradation when compared to conventional arc lamps
• No shutters needed
• No costly replacement parts required, greatly limits machine downtime
• Cost savings over product lifetime

To date, the migration from vapor lamps to UV LED is somewhat slow. Some contributing factors are life expectancy and efficiency. Typical UV LED life expectancy is about 2,000 hours to 5,000 hours compared to vapor lamps at 8,000 hours to 12,000 hours. But, recent advancement in the next generations of UV-LED has a life expectancy of 50,000 hours or 10 times that of the average UV LEDs. Meanwhile, the typical efficiency of UV LED is about 5% to 8%, which requires further development enhancements. Regardless, the UV LED adoption will grow as the gap narrows between UV-LEDs and vapor lamps. This will translate into a faster growing market in the future.

Reference:
http://www.ecnmag.com/articles/2010/04/key-benefits-next-gen-uv-led-tech

UV Light Applications for Manufacturers

Below the visible spectrum lies a band of wavelengths called ultraviolet (UV). Ranging from 100 to 400 nm, the radiation can effectively be used to sterilize cosmetics, perform forensic analysis, disinfect water and cure materials. More specific to manufacturing, UV rays take on roles designed to speed up the entire fabrication process.

Uses in Manufacturing
Ultraviolet curing is a process in which UV energy produced by a mercury discharge lamp is absorbed by a sensitizer, causing a reaction in the monomer which makes it hard and dry. This UV “curable” monomer includes a sensitizer which absorbs UV energy and initiates a polymerizing reaction. Manufacturers use this process to instantly cure or “dry” inks, coatings or adhesives throughout the engineering process.

At Norlux, for example, UV acrylate encapsulating resins are employed for achieving brighter chip-on-board (COB) LED assemblies. When cured with a DYMAX 2000-EC moderate intensity flood curing system, the Light-Cap family of encapsulates offer superior optical transmission during the life of the LED assembly. Their resistance to elevated operating temperatures results in reduced yellowing (a common phenomenon in brighter COB applications) compared to traditional encapsulating resins. UV/visible light curing coatings offer a wide range of high performance properties including lower stress and more durable wire bonds, superior adhesion, multiple viscosities, minimal shrinkage and low outgassing. Other characteristics described include good moisture resistance, optical clarity and excellent environmental resistance.

UV cured materials are widely used in circuit protection and electronic assembly applications, where products are electrically insulated and designed for various operations including: conformal coating, encapsulation, bonding, keypad coatings, thermal management, and masking. These materials are IPC approved, MIL-I-46058C and UL listed self-extinguishing graded, and are available in multiple viscosity grades depending on application method.

Advantages
UV curable materials provide manufacturers of electronics ease and flexibility in their conformal coating process. Because UV curable materials can be applied in a variety of ways including manual and automatic spray and dispensing, manufacturers are provided with different processing options while allowing them to meet cycle time and product specification requirements. For example, some Printed Circuit Board Assemblies (PCBAs) require environmental or dielectric protection or both. A PCBA manufacturer may set up a conformal coating line that has an automated spray/dispense system and a UV curing chamber. This curing methodology allows manufactures to eliminate thermal and room temperature curing methods, and also ensures that the material has reached full cure upon exit from the UV curing chamber. Other coating materials do not reach full cure for 48–72 hours.

LEDs as Alternatives to mercury arc lamps
UV LED technology is rapidly replacing traditional mercury or arc-based lights. In production curing operations, mercury-vapor lamps are hindered by short lifetime (2000-10,000 hrs.), slow warm-up and cool-down times, and wide spectral power distribution. The UV output of a mercury vapor lamp drops off rapidly over its operational life because some of its electrode material vaporizes, depositing a film on the inside of the quartz tube, which the UV cannot penetrate. This results in an unpredictable amount of UV output over time, which is a critical process parameter.

The mercury lamp has a main peak at 365 nm but several smaller peaks in the visible and infrared regions. The results are peaks in heat output, making working with plastics and other heat-sensitive materials a challenge. Due to the high voltage heat and environmental issues surrounding disposal of mercury bulbs, manufacturers now consider LED based UV curing. There seem to be too many variables to consider when dealing with traditional mercury or arc-based lights in standard curing processes.

UV LEDs bring such benefits as knowing precisely what power level is being delivered to the curing medium, as well as the other advantages LEDs are known for, such as the ability to pulse-width-modulate the output. The change from conventional curing technologies to UV LED allows system manufacturers to offer their users lower operating costs and higher quality products while enabling new capabilities and even reduced shipping and inventory storage due to the ability to print on thinner, heat-sensitive substrates.

Source: (http://ledsmagazine.com/features/9/2/5), (http://ledsmagazine.com/press/8554)

Integrating Touch User Interfaces with LED Lighting

Touch based user interfaces controls have become common for controlling consumer electronic, commercial, and industrial systems. Most recently, the architectural marketplace has been quick to incorporate touch controls with LED technology.  At the May 2012 Lightfair convention in Las Vegas, dozens of touch based light control systems were showcased.  In fact, the Illumination Engineering Society (IES) has an excellent overview topology (publication TM-23-11) on the structure of an LED control system that could feature a touch based interface.

Reprinted with permission from Lighting Control Protocols (TM-23-11) by the Illuminating Engineering Society of North America.

For this discussion, we’ll focus on the “front-end” of the diagram. The most common way to detect a touch is by indirectly sensing the conductive mass of the human finger. Sometimes referred to as “capacitive” touch, this technology relies on detecting an electric field disruption of an approaching finger with a sensing electrode below a dielectric decorative substrate like glass or plastic.  Successful specification, design, and implementation of a touch-based user interface require a basic understanding of the active elements that comprise the system.

The dielectric decorative substrate is best described as the surface that a user touches when interacting with the interface. Typically constructed of glass or plastic, it serves as the primary aesthetic element in the product’s user interface design. In the case of touchscreens, the decorative substrate is usually planer and constructed of glass. In the case of discrete touch points, the geometry is almost unlimited with touch points integrated into many surfaces (commonly injection molded decorated plastic). The decorative substrate can also be backlit for aesthetic or functional purposes.

The electronic carrier is the element containing the sensing electrode structure and interconnects for the touch user interface. Discrete touch points (fixed touch points behind decorative icons) frequently use rigid FR4 printed circuit boards and touch screen use transparent conductive electrodes. Electronic carriers can be in the form of an external circuit or integrated with the LED driver. When designing touch solutions, thinner is better. A thinner decorative substrate and a thinner electronic carrier result in better signal to noise ratios resulting in a more robust touch solution.

LED drivers that are microprocessor based become excellent candidates for an integrated touch control, particularly if the driver circuit is co-located with the user interface. Since many microprocessors can be configured as touch controllers, cost is reduced with a simple solution. Several manufacturers offer low-power touch controllers that are suitable for battery operated “touch” remote controls which can connect to the LED driver using a wireless protocol such as ZigBee.

Norlux has extensive experience in the design of LED Drivers and has developed touch controls for the Architectural market. From simple on-off switching to full wireless intensity, color, and saturation control, Norlux is your one-stop partner for LED lighting and control solutions.

References
IES (Illumination Engineering Society) publication TM-23-11 (http://www.ies.org/PDF/Store/TM-23-11_FINAL.pdf)

LED Downlights – A Hot Trend in Architectural Lighting

With advancements in lighting technology, LED downlighting is an exciting option for architects and builders today. More people are becoming aware of the numerous benefits of choosing LED downlighting, and how it brings a modern dimension to home and office lighting. There is no doubt that a well-placed LED downlight can create a sophisticated, elegant and highly customized look in commercial or residential buildings. They excel at highlighting architectural features of interest, while drawing attention away from less exciting elements. LED downlights are widely used in bedrooms, sitting rooms, reception areas, display cases, cabinets, offices, art displays, bars, hotels and lobbies.

So why are LEDs becoming so popular in architectural lighting applications? With near perfect lighting effects, LED downlights depict an atmosphere of comfort and warmth. Add a dimmable function, and they not only adjust light output to fit any desired mood, but also conserve energy and lengthen the LED lifespan in the process. Beyond mere aesthetics, the inherent attributes of LEDs and their resultant benefits make them an ideal candidate for downlighting. 

• Lifespan: LED downlights are ultra-durable with a lifetime of over 35,000 hours (average), which is roughly equivalent to a lifespan of 20-25 years with normal usage.
  
• Temperature: LED downlights produce less heat than traditional lights, increasing safety by minimizing fire risk.
• Energy Efficiency: With high efficacy of LEDs and a long lifetime, LED downlights can save 70% on energy bills when replacing conventional recessed lights and incandescent lights.
• Maintenance: LEDs do not require much maintenance inherent with frequent lamp replacements. The low operating temperature of LEDs helps reduce air conditioning and maintenance costs as well, saving money long term.
• Color: LEDs for lighting applications have been designed to achieve a warm, white light that ranges > 90 on the color rendering index (CRI), and are described as “eye comfortable”. This light brings out the details of the decor, subtly improving aesthetics and mood.
• Safety and health: LEDs emit no ultraviolet rays or toxic substances (mercury). There are no environmental hazards to be concerned with when disposing LEDs either; heightening the overall “green” aspect of any space. Moreover, the lack of Infra-Red and Ultra-Violet rays emitted by LEDs means the light is healthier and less harsh, putting inhabitants at ease.

While some might balk at the slightly higher price of LED downlights, such amounts can be recovered relatively quickly since consumers are assured of significant energy saving over the lifespan of the product. LED users will enjoy excellent quality of light for their home or building, at a more affordable monthly power rate.

Increasingly, more professional manufacturers and suppliers of LED down lights have emerged. Now one can choose the right LED downlights with affordable prices and guaranteed quality for not only commercial applications but residential lighting as well. Contact Norlux today for a consultation on your LED lighting project.

LEDs and Aviation Illumination, Ascending to New Heights

The Aviation industry and airfield signage specifically, utilize LED lighting technology more than most other applications today, both in the military and commercial sectors. “Their attributes are well-known – crisp lighting, energy efficiency, long lifetimes, low voltage requirements, compact size, fast on/off time, shock resistance and no color filter requirements. Applications for LED illumination in aviation range from wing-tip lights to indicator lights on flight decks to pilot guidance lights on airfields to mood lighting in aircraft cabins” (Les, 2009). Here at Norlux, we develop light engines, drivers, and power supplies for both air and ground based aviation applications; and business we do with companies within the aviation realm is certainly thriving. It seems LEDs found a perfect application fit to showcase their many well-known attributes.

Upgrading old or obsolete lighting technologies pose challenges within the aviation industry, and inching towards the future is never as easy as it seems. “Work is progressing to leverage the advantages of LED lighting in the aviation industry and to overcome challenges presented by the technology, such as in the areas of thermal management and in retrofitting the technology into existing lighting systems” (Les, 2009). Raleigh-Durham International Airport offers a great example of the costs in time and money to overhaul their entire runway lighting system in order to take advantage of what LED technology provides. “Officials at Raleigh-Durham International Airport (RDU) in North Carolina realized they were spending a lot of money maintaining an antiquated airfield lighting system. The lighting fixtures were subpar. The cable was old and cracking and meg-ohm readings for many of the circuits were at zero, which meant the airport had to keep pumping up the power to feed the lights. Signage was also a problem. Some were very bright; others rather dim. Some signs were even bright and dim within the same unit” (Nordstro, 2010). "The FAA wasn't very happy with us," recalls Steve Pittman, deputy airport director of Facilities, Engineering and Maintenance. "They didn't demand that we upgrade our lighting system, but they did suggest we do something about our signage lighting" (Nordstro, 2010). “RDU took the hint and initiated a $20 million project to convert its incandescent airfield lighting system to LED technology. Over the last two+ years, roughly 230 signs and 3,200 bulbs were changed - everything from taxiway edge and centerline lighting to runway centerline lights, obstruction lights, touchdown zone lights, runway end identifier lights, and elevated and in-pavement guard lights” (Nordstro, 2010). The makeover, as it turns out, was nothing short of spectacular. “Everything that can be LED is LED. It's an amazing look at night" (Nordstro, 2010).

So why make the change to LED lights? Costs in terms of man-hours as well as dollars are a driving force. “A primary benefit of LED lights is the lack of maintenance required once they are installed” (Airport Technology.com, 2008). “LEDs are a very efficient light source [for aircraft] and can significantly reduce seat-mile costs and schedule upsets because of their dramatically increased reliability over filament lights” (Les, 2009). Cost savings and energy efficiency always lead the list of attributes associated with LEDs. “With the former incandescent lighting system, RDU maintenance crews were replacing bulbs twice a year per fixture. Operations crews were constantly checking the airfield for burned out lights. There were operational consequences as well. Airfield pavement sections had to be closed when bulbs were replaced. Electrical circuits were tied together in haphazard and confusing ways, which made maintenance time-consuming and costly” (Nordstro, 2010). “Replacing every bulb in every light at least twice a year was not only a safety issue, it was quite costly in parts and labor. Subsequent analysis showed that moving from incandescent lighting to LEDs would save approximately $400,000 per year in energy and maintenance costs including labor and parts” (Nordstro, 2010).

Energy efficiency and the “green” aspects of LEDs are always attractive elements to any application, and aviation lighting is no different. “LEDs are the hot item in lighting these days, both due to their energy saving properties and also the expected long life of the light source” (Airport Technology.com, 2008). Solar-powered LEDs are also a viable option, especially for some smaller airfields. As a versatile lighting alternative for “temporary runways, remote airfields without grid access, or as an emergency-response application, solar-powered LED lights offer distinct advantages. Self-contained, portable and wireless solar LED lights can be installed and operational in a matter of hours to provide bright and reliable lighting” (Airport Technology.com, 2008). "With a quick set-up, no scheduled maintenance and complete freedom from the costs and logistical restrictions associated with installing and operating a grid or generator-powered system, solar LED lights offer a versatile and cost-effective alternative for a variety of applications” (Airport Technology.com, 2008).

With the ten- to twelve-year lifespan of LEDs (on average), users employing LED lighting technologies can reallocate manpower and funds away from expensive and time-consuming maintenance duties onto more customer-centric tasks. It goes without saying that in the transportation/aviation industry “organizations that are responsible for large assets, the move to green technology is important” to keep business competitive, solvent and on the cutting edge of technology (Airport Technology.com, 2008).

Sources:
http://www.photonics.com/Article.aspx?AID=37892 
Caren B. Les, Photonics.com – June 2009

http://airportimprovement.com/content/story.php?article=00203http://airportimprovement.com/content/story.php?article=00203
Robert Nordstro, Airport Improvement Magazine - September 2010

http://www.airport-technology.com/features/feature46764/
Author Unknown, Airport Technology.com – December 2008

LED Thermal Management

It can be a huge challenge to keep electronic products running cool, and LED lighting products are no exception.  An LED’s light output is determined by the amount of current applied to the LED and the subsequent management of the heat emitting from the LED.  The higher the electrical current, the more heat generated at the LED junction.  This heat can lead to output deterioration, which limits the amount of light that can be generated by an LED, reducing the life of the LED over time.

Designers need to account for temperature factors in the early stages of the design process to mitigate heat’s potential adverse effects.  Thankfully, the effects of heat in an LED system can be understood through calculation and simulation.  A model that is used frequently is the thermal circuit model.  These thermal circuit models are similar to resistor circuits using Ohm’s law.  An LED’s power dissipation is modeled as a current source, thermal resistances are modeled as resistors, and the ambient temperature is modeled as a voltage source.  The thermal resistance must be minimized to increase an LED’s light output or its useful ambient temperature range for a given power dissipation.

Minimizing the thermal resistance can be done in a number of ways.  Conduction, convection, and radiation are the three means of heat transfer.  Conduction and convection are typically used to transfer heat from LEDs to ambient temperature.  Convection requires the movement of air, which in many instances requires a mechanical means of moving air, such as a fan.  In many cases, fans are not an acceptable way of cooling LEDs in light fixtures due to noise and reliability concerns.  Conduction, however, is the transfer of heat from one solid to another, and is typically the way LED systems are cooled.  Conduction requires the accurate design of heat sinks to properly cool an LED system in its intended environment.  This is where the thermal circuit model is valuable.  The thermal resistance value of a heat sink can be calculated for the specific LED system and its temperature environment.  This information allows for the proper selection criteria for a standard heat sink or provides the information needed to design an effective thermal management system.

Designers at Norlux are experienced in LED thermal management and the design of thermal systems.  If you are facing challenges regarding LED performance and LED heat dissipation, contact Norlux for a solution that’s ahead of the curve.

Undercabinet Lighting: A Great Application for LEDs

Incumbent technologies such as halogen and fluorescent lighting have dominated the undercabinet fixture market for years. Of course, both of these light sources are known to have some significant deficiencies. Halogen lighting is an energy hog, gets extremely hot, and has a short lamp life. Fluorescent tubes have poor dimming capability (if any at all), contain harmful mercury, and are available in a limited number of lengths. LEDs, on the other hand, are more than just a buzzword in the lighting industry nowadays. The attributes of LEDs and the corresponding benefits they provide make them an ideal candidate for undercabinet applications.
 

Heat:

Typical halogen undercabinet fixtures will run between 70°C – 90°C. This adds heat to an already hot cooking area, can cause cabinet discoloration and delaminating, and can dry-out or melt perishables stored on the shelving above. By comparison, LED fixtures will typically run at less than 40°C and are safe to touch.

Size:

LEDs are extremely small and low profile. This characteristic allows lighting designers to create lower profile fixtures, which are easier to conceal. In addition, LEDs can be arranged to create a fixture of any length.

Life and Power:

When utilized 4 hours per day, the average life of a halogen bulb is approximately 4 years. By comparison, LEDs in the same application will typically maintain more than 70% of their initial intensity after 34 years of use. Also, at the same 4 hours per day, consuming power at $0.10 per KWH, a single 22˝ LED undercabinet fixture will save its owner $7.68 per year in energy costs.

Optical:

In an undercabinet application, light is required everywhere from the front edge of the counter top to where the wall meets the cabinet. This is typically a 130° range when viewed from the light source. All light falling outside this range is undesirable and wasted. Due to the fact that LEDs are directional in nature, a fixture designer can better focus the light where it is needed using asymmetric engineered diffusers or any number of optic techniques.

Dimming:

Most people consider dimming an absolute must for kitchen applications. Electronically speaking, LEDs are extremely versatile and can be designed into circuits utilizing diverse dimming methods. One can even design an undercabinet system that can be dimmed using common off-the-shelf dimmers.

Environment:

LEDs do not contain harmful elements such as mercury or lead. This provides environmentally responsible designers and manufacturers the opportunity to produce a "green" product, which can even meet strict RoHS standards.

For more information, please contact Norlux at 630-784-7500 or visit us at www.norluxcorp.com.