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(June 2011) posted on Tue May 31, 2011

Overstatements can confuse expectations.

By Dr. Nisa Khan

As president of LED Lighting Technologies, Dr. M. Nisa Khan consults in the solid-state lighting industry and educates consumers about LED lighting. She has a bachelor’s degree in physics and mathematics, and master’s and Ph.D. degrees in electrical engineering. Email her at nisa.khan@iem-asset.com

More and more, LED lamps have captured global attention in science, industry, government and the general population, as applications increasingly light up buildings, billboards, entertainment zones, signs, decorative lights and even television screens. The related excitement is so overpowering that, Samsung, a few years back, labeled one of its TV models as “LED TV,” but, frankly, the sets were mere LCD TVs with LED-based backlighting. Unfortunately, such overstatements often generate misleading expectations.

Many expect LED lamps will soon replace many everyday lamps, if not all of them. Others argue LEDs’ costs limit this predicted prevalence, but, in contrast, inexpensive – cheap -- LED offers crowd the Internet.

So, are LED lamps too expensive?

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The answer is yes and no. And, because reducing costs and energy consumption, and protecting natural resources is an imperative task for all, a grasp of the high costs’ underlying reasons is essential for LED manufacturers, resellers -- and end users.

Core challenge
Currently, high-brightness and high-quality LED lamps are too expensive for wide-ranging use. At heart is the binning issue, which arises from the wide-ranging light and electrical characteristics produced from the same wafer during manufacturing, especially when compared to the much smaller (and accepted) variations experienced in other lamp-building technologies.

Such LED lamp variations result from a complex set of issues that encircle semiconductor-material growth, processing and fabrication, which also affects the interdependent optoelectronic and thermal properties.

The laborious process of consistently binning LED chips, with a required degree of light parameters for different applications, comprises large and expensive testing equipment and significant manual intervention. The latter is necessary to measure such light parameters as luminance, flux, color, directivity and power consumption. This complex gauging determines the suitable bin.

Also, because the parameters are temperature- and drive-current dependent (which also affect LEDs’ lifespans), these matters become more complicated. The solid-state lighting (SSL) industry’s standards group member -- National Electrical Manufacturers Assn. (NEMA) -- provides specific testing procedures for each parameter.