Let There Be Solid State Light
By Bob Hult, Bishop & Associates Inc.

It is hard to imagine a basic technology in general use today that has remained essentially unchanged over the 130 years since its development, but that describes the common light bulb. Huge advances have been made in communications, air travel, computing, and healthcare, but the common incandescent light bulb continues to be the predominant source of lighting in our homes. The modern bulb shares the basic construction of a resistive filament installed in a glass bulb that has most of the air removed. When current is passed through the thin wire, it heats up and begins to glow. Given the right combination of materials, environment, and current, it will incandesce, providing a bright white light. The replacement of candles and oil lamps with electric light bulbs forever changed our living and working habits.

The typical light bulb can operate for 750 to 2,000 hours before the filament fails. They are manufactured on fully automated equipment, making them very inexpensive and easy to replace. The problem is that they are terribly inefficient. The visible light they produce is estimated to be only about 10 percent of their energy output, with the remaining 90 percent emitted as infrared heat. A large percentage of the cooling costs in office buildings are attributed to removing the heat generated by light fixtures. The thin glass globe is very fragile, while the wire filament is sensitive to shock and vibration. Breakage of the bulb or burnout of the filament results in total failure of the lamp, a real problem in critical lighting and status indication applications. A series of emerging technologies combined with increasing environmental concerns have set the stage for the development of a better source of light.

The debate over global warming has stimulated examination of every source of carbon production, and much of this can be attributed to the production of electricity. Coal, oil, and even gas-fired generating stations produce hydrocarbons that enter the atmosphere and add to the contamination of our atmosphere. One result of this concern has been a focus on reducing our overall electrical energy consumption. Many devices have been designed to be more energy efficient, and our government is promoting the use of “Energy Star” rated appliances to reduce household energy consumption. The “green” movement is putting the spotlight on the entire energy production and consumption process. Alternative energy production, including wind and solar, are becoming mainstream sources, and reducing consumption at the user level is now a marketing advantage as individuals and businesses look for ways to cut costs. Highly inefficient incandescent light bulbs quickly became a prime target for a reduced energy-consuming alternative.

Fixtures that utilize fluorescent tubes have long been the preferred light source in commercial buildings and many retail stores. They produce more light (lumens) per watt then incandescent bulbs and much less wasted heat. Unlike light bulbs, which emit a point source of light, fluorescent tubes, up to six feet in length, produce softer, nearly shadow-less illumination.

The introduction of miniature folded or twisted fluorescent tubes, together with the integration of starter circuits built into the base of a standard Edison socket, opened the market for a fluorescent replacement for the standard light bulb. Consumers are able to replace a 60-watt light bulb with a compact fluorescent lamp (CFL) that consumes only 14 watts. The fact that the projected life of a CFL is 10,000 hours, perhaps 10 times that of a standard light bulb, is a nice side benefit to the average consumer, but it is a critical advantage in large buildings, where reducing the labor costs of maintaining thousands of lamps adds up to a significant savings.

The compact fluorescent lamp has made some serious inroads in the commercial and consumer lighting market as prices have come down, and utilities have begun offering rebates and even free bulbs. Electric utilities would prefer to slow the growth of consumption rather than be forced to increase expensive generation capacity. Given their lower energy consumption and much longer life, CFLs have become the low-cost leader over the life of the lamp. High-volume offshore production of CFLs continues to drive their cost closer to parity with incandescent lamps. Several countries, including Canada, have already established a deadline for the sales of conventional light bulbs, further encouraging their residents to make the switch to CFLs.

Nothing in life is perfect, including CFLs, which pose their own set of problems.

Great strides have been made in developing a fluorescent lamp that produces the warm color tones similar to incandescent lamps, but they are still perceived as cooler, with the potential to distort colors. More importantly, they are very difficult to dim, a large problem when replacing bulbs in ceiling fixtures. Circuitry in the base of the lamp can be a source of electromagnetic interference (EMI), and CFLs may not operate at subzero temperatures, a challenge in some outdoor applications. The biggest concern revolves around the fact that all fluorescent lamps contain small amounts of mercury, a highly toxic material. The thin glass tubes can be easily broken, exposing consumers to a potential health hazard. Packaging of CFLs encourage proper disposal of a discarded lamp, but few facilities exist, and questions remain about how many consumers will make the effort to seek out these sites. A massive transition to CFLs could result in huge quantities of these bulbs ending up in landfills, with the potential to contaminate the soil and water.

As compact fluorescent lamps are ramping to huge production quantities, Light Emitting Diodes (LEDs) are setting the stage for the next evolution in lighting systems. LEDs have been used for years in signage, Christmas decorations, and automotive applications, but the development of high-power white LED technology has begun to open the door to general lighting applications on a massive scale. LEDs are manufactured using materials and processes similar to semiconductors and can be scaled to high-volume production.

LED illumination offers an unbeatable combination of exceptionally long life, minimal heat generation, and much reduced physical size, while consuming a small fraction of the energy required by an incandescent bulb. An entire spectrum of colors can be produced in molded plastic packages that resist damage from shock and vibration. A LED can operate upwards of 50,000 hours, and fails slowly by reducing output over time, rather than catastrophically. Unlike a light bulb that radiates in all directions, LEDs produce a highly directional beam, improving the efficiency of the useful light output. LEDs produce little IR or UV radiation, making them ideal for applications that are sensitive, such as artwork or food. Dimming LEDs using commonly installed low-cost triacs were a challenge to early iterations of LED lamp assemblies, but new drivers have been developed that allow direct replacement of incandescent lamps that use standard dimmers.

Although they produce little radiated heat, energy is concentrated at the diode junction and is not dissipated away as it is in incandescent lamps. Designers must ensure that the packaging of the LED provides a low resistance thermal path to guarantee that the chip junction remains below specified limits.

In order to achieve a desired level of light output, LED manufacturers have developed arrays of individual LEDs or multiple LED chips on a single substrate. The heat generated by so many LEDs in close proximity often requires the addition of external cooling features to achieve proper thermal management.

Arrays of high-power white LEDs packaged in assemblies that may include cooling fins are now on the market. Many of these lamps are designed to be directly plug-compatible with conventional light bulbs.

Major advances in high-power LED assemblies have enabled them to penetrate high-output, harsh environment applications. Osram, a major supplier of LEDs, recently introduced a modular assembly specifically designed for street lighting applications. Designed for a life of 50,000 hours, or more than 10 years of 12-hour-per-day operation, they offer significant savings in maintenance costs, as well as power consumption.

The reduced profile, energy consumption, and radiated heat of a typical LED lamp allow entirely new profiles of lighting fixtures.

In addition to inventing the light bulb, Edison introduced the concept of a simple screw-in socket that provides both mechanical support as well as electrical connection, making installation easy for the average consumer. Various sizes have been introduced over the years, but the basic design remains the same.

The standard Edison lamp socket is a classic example of what has become a commodity interface. Electronic connector manufacturers have generally chosen not to participate in this market due to low prices and little potential for innovation. This socket is relatively large but is in appropriate scale with the size of the mating incandescent bulb. Introduction of much smaller LED lamp assemblies changes this paradigm. The form factors of new solid-state light sources (luminaries) are emerging from a variety of manufacturers, but few, if any, universal socketing standards exist at this time. The ability to provide pluggable products that enable ease of installation, interchangeability, and upgradeability opens the door to huge new market potentials. Adoption of universal socket standards opens the door to a mass market at the industrial, commercial, and consumer levels.

This is where the opportunity to develop new products may exist for electronic connector manufacturers. Lighting systems using LED sources appear to be the long-term solution to addressing energy conservation efforts, but their tiny size and low power operation will also allow the design of entirely new lighting fixtures with smaller profiles and unique shapes. LED illumination offers the opportunity to break away from conventional lighting fixtures that are based on large heat-generating point sources of light. LED arrays can be packaged in thin panel forms or be integrated into products that require flexibility, durability, and long life. Flat panels of up to 2’ X 4’ now can be built with less than half-inch in depth. Light spreaders, similar to those used in LCD displays, distribute the light evenly over the entire surface.


Many solid-state lighting applications today involve strips of LEDs mounted on a narrow PCB board. Applications exist for plugging these strips together, as well as surface-mounted socket assemblies.

Molex and Tyco Electronics have established business and product development groups focused on exploring the possible form factors and applications of this evolving technology. In some cases, they are partnering with established lighting equipment suppliers to jointly develop LED lamp and socket assemblies. Connectors that allow simple connection to the unique features of solid-state lamps are being introduced. They are also working on solutions to the challenges of heat dissipation, color shift with aging of the LED, simplifying the integration process, as well as cost reduction.

Molex has been aggressive in exploring new LED-based product opportunities. They partnered with Leviton to introduce the Transcend™ LED light engine. This self-contained pluggable module features an integrated driver and radiant fins that simplifies the transition from incandescent to solid-state lighting in a variety of fixtures. The design allows flexibility of beam angle, input voltage, and color temperature. Modules can be connected directly to AC line voltage and are dimmable.

Two-inch reflector modules and three-inch surface pucks will be available by mid-2010.

The new Molex Helieon™ LED light module targets mass-market adoption of LED lighting technology in general lighting applications. A joint effort between Molex and Bridgelux, the Helieon module is based on a multi-chip array in a pluggable format.

The module and socket are designed to permit maximum flexibility and adoption of future advances in the technology. The lamp module operates on low voltage and requires an external driver provided by the lamp manufacturer. The initial socket includes two contacts, but can accommodate up to six contacts to support future options. A variety of modules offer different beam widths in 60 and 100 watt equivalent outputs, while consuming 12 or 18 watts of power. A heat spreader is built into the module that conducts excess heat to external thermal management structures provided by the lamp manufacturer. Target customers are lamp manufacturers who are designing new fixtures that can take advantage of LED lighting sources.

Tyco Electronics is taking a holistic approach to the emerging LED market. Leveraging the resources available within the Tyco family of companies, they have created an integrated solid state lighting solutions business group that offers interconnects, circuit protection devices, thermal management expertise, optics, and device control.

They have released a series of connectors designed specifically to simplify the plugability of LED sources. In some cases, they are modifications of existing connectors, such as an inverted surface mount two-position Mini-CT connector that connects to surface mount pads on a metal clad PCB, and pokes through the board to the mating connector.

In other cases, they have created new interfaces, such as a solderless high intensity LED holder that includes options for a heat sink and snap-in lens carrier adapter. This low profile, small footprint socket simplifies the process of LED assembly and replacement.



Replacement of traditional fluorescent tubes with LED equivalents is gaining traction in large commercial buildings, where energy consumption, heat generation, and maintenance costs are major concerns. Retrofit tubes in the standard G-13 format generated the need for an end cap connector that joins the standard receptacle socket to an internal PCB on which a series of LEDs are mounted. A surface mount hold down provides stability during the tube insertion and extraction process.


The fact that many LED lighting assemblies are constructed on printed circuit boards prompted the introduction of a tool-less terminator for discrete wires. These connectors are through hole or surface mounted to the board, and feature IDC termination from 18 to 24 AWG solid or stranded wire.

Tyco has also introduced circular sealed connectors for outdoor lighting applications.


AVX also introduced a series of new connectors and accessories to support the solid-state lighting industry. They are offering both board-to-board and wire-to-board connectors that simplify the connection of modular LED assemblies. They also provide an extensive line of circuit protection devices.

The pace of new product announcements designed to facilitate LED lighting is accelerating as makers of power supplies, metal clad PCB material, drivers, and advanced LEDs recognize the potential of this market.


Even traditional backplane and card cage manufacturer ELMA has entered the market with their M-tube modular LED light tubes. Available in lengths of up to two meters, these tubes offer bright light in a variety of colors. 
 

Bishop & Associates Comments:

• It is estimated that up to 22 percent of electricity in the United States is consumed by lighting. Efforts to reduce the production of hydrocarbons through energy reduction and improved efficiency are driving demand for lighting devices that consume less energy.

• Efforts are currently underway to define standard LED lamp packages that will facilitate the market for universal sockets. Major lamp suppliers, including Phillips, General Electric, and Osram, are working with NEMA and ANSI to develop formal specifications. Standardization may come through formal standards writing organizations or industry acceptance of recently introduced formats that become de facto standards.

• At this point, LED equivalent bulbs are at least 10 times the cost of a conventional light bulb, but the price differential is expected to close rapidly as volume applications expand. The growth of this technology in signage, display, architectural, and general lighting represents huge potential for industry leaders willing to make an early commitment to exploring the possibilities.

• Solid-state lighting enables much smaller and thinner light fixtures that can fit into spaces that could not accept traditional lamps. Interior and exterior lighting will be free to pursue entirely new form factors.

• Displays using LED backlighting offer greater color fidelity and improved contrast ratio in a slimmer package. Many computer displays and high-definition TVs that utilize LED illumination are entering the market.

• Low power, direct current consumption allows LEDs to operate from energy generated by small solar panels, making it possible to provide lighting in regions that lack a power distribution system. The global potential could easily exceed the value of the existing light source market.

Robert Hult
Director of Product Technology, Bishop & Associates Inc.
Robert Hult has been in the connector industry for more than 36 years. Hult began his career as a sales engineer for Amphenol. He joined AMP in 1972 and served in several management positions through 1996. In 1997, Hult joined Foxconn as group marketing manager for Intel in Chandler, Arizona, U.S. Prior to joining Bishop & Associates, Hult was the regional application engineering manager for Tyco Electronics.

Hult graduated in 1968 from Bradley University with a bachelor of science degree in electronics technology and a minor in business.