LEDs and Their Rapidly Changing Form Factor

From street lamps to industrial applications, LED use goes well beyond screwing an LED light into a desk lamp. Historically, retrofit LEDs have often emulated the form factor of the lamps they were replacing. Anything out of the ordinary was problematic, but this is rapidly changing.

There are hundreds of millions of fluorescent strips and industrial fixtures installed in varying locations and applications throughout North America. LED luminaires are replacing these fixtures rapidly, combining aesthetics, high performance and slim, modern form factors. Energy cost is easily lowered by up to 25 percent with these replacements, and ongoing bulb maintenance is becoming a thing of the past. 

LED Arrays

Adjusting form factors ultimately comes down to achieving the right amount of light output from a lighting fixture. While single LEDs might not meet the needs of applications that require high luminosity, multiple LEDs can be used effectively in arrays. And while the lighting fits the bill, the downside of arrays can include their size, their assembly price tag and their level of complexity when trying to match correlated color temperature (CCT).

The size of an array is dictated not only by the size of the LEDs used, but also involves the necessary space between devices for thermal considerations. This required space, in conjunction with the addition of optics and heat sinks, increases the overall size of the array. One way around this challenge is to increase the luminosity of the individual LEDs, using fewer bulbs to meet the required output. By integrating heat sink and power electronics with the LEDs, materials, time, cost and precious space are all reduced.

Weighing the Options

LEDs often do not age uniformly. While some may hit the threshold of losing 30 percent of output and become noticeably inferior, other LEDs in the array may hold their output levels over a longer period of time. Based on the faster aging of some LEDs over others, many users opt to completely replace the array.

Assembling LED arrays can be difficult and time consuming. Design engineers, therefore, are often faced with the choice between spending time dealing with assembly woes, or spending even more money on pre-assembled modules. One of the real benefits of arrays in pre-assembled modules is that there tends to be a high level of integration.

Trends in Changing Form Factors

As the technology advances and design engineers come across varying applications, LEDs are taking on various forms.

• Highly integrated slim-profile LEDs reduce bill of materials (BOM) and spread light more efficiently and broadly, making them suitable for use in environments that were previously too harsh for LEDs.
• Another trend in LED form factors is the shrinking of package sizes for the same output or lumen density that was originally inherent in a larger form factor. This is the case with OSRAM Opto Semiconductors' OSLON SSL, which comes in a small 3 x 3 mm package.
• A Bridgelux water resistant Outdoor Lighting Module (OLM) integrates LEDs, optics and environmental protection in a package that, when screwed to a heat sink, replaces high-pressure sodium (HPS) lamps. A single module can replace 50 or 70 W HPS lamps. And, a casting with two modules replaces 150 W HPS.

Although their packaging may be shrinking, LEDs today deliver big performance, thermal management and a substantial cost savings. This powerful combo is paving the way for even more new and exciting form factors in the not-too-distant future.