An Introduction to LED Module Technology

LEDs are rapidly replacing traditional light sources in applications where their unique characteristics can be best put to use such as their small size, low power consumption, low self-heating, high reliability, rapid on/off cycling or dimming capabilities, and they are resistant to shock and vibration due to their solid-state composition. Some LED features that can also be considered disadvantages depending on the application are the narrow viewing angle (beam size), near monochromatic light, limited wavelength selection, and they require a limiting resistor with a voltage drive.

Grouping individual LEDs into modules that in turn can be grouped into larger assemblies to create high-output, flexible configuration lighting systems has revolutionized LED lighting by expanding the breadth of applications they can be adapted to. Let's get into Led modules a bit more.

What are LED modules?

LED modules typically are constructed of a series of surface-mount LEDs soldered to a copper circuit layer that is separated from a base, which is frequently aluminum and typically rigid although flexible base materials are now being used, by an electrically isolating, heat conductive dielectric material making for a very compact, durable light assembly. A dielectric is used to isolate the LED from the conductive base material because, in most cases, the back of the LED which is the heatsink area is often electrically connected to the LEDs anode or cathode. Generally, electrical interconnection is made via a removable wire connector soldered to the LED module's conductive copper layer or via wire leads. High-power LED modules which are generally LED modules made up of surface-mount LEDs with a power consumption of 0.5 watts or more, are the latest thing in lighting today due to their high brightness and relative efficiency.

What are the advantages of using LED modules?

LED modules, like the discrete LEDs they are made from, offer cool lighting with a very long life expectancy (10,000+ hours) as compared to traditional lighting like halogen bulbs. LEDs while quite a bit more efficient then halogen light sources, are not as efficient as fluorescent lighting but have many other advantages over fluorescent lighting such as the ability to function in cold environments and switch on and off rapidly and have dimming capabilities. The sheer variety of available LEDs, their exceptionally small size, and the ability to widely vary the base layer shapes and sizes offers designers and engineers alike a degree of freedom when designing high-power LED modules and systems not typically available when working with more traditional lighting technologies.

Efficiency versus brightness

Efficiency of an LED is the measure of the maximum light output, often expressed as total brightness in optical units of lumens or candela (candlepower) versus the maximum electrical power consumption expressed in units of watts. Efficiency versus brightness is one of the more important considerations to be made when choosing LED modules or their component LEDs and too often the power consumption of an LED is misunderstood to mean the LEDs brightness. A 2 watt LED sounds brighter than a 1 watt LED but if the 2 watt LED outputs 35 lumens and the 1 watt 45 lumens, then the 1 watt LED is actually brighter. Output power is no indication of efficiency either. Some of the more powerful LEDs marketed today have power consumption ratings of 5 watts with an output power of 120 lumens or more each which is considered an ultra bright LED but when compared with a 1 one watt LED outputting 40 lumens we see it is not very efficient at a little less than half as efficient as the 1 watt LED. Increased output power and decreased efficiency leads to the generation of the subject of the next paragraph: Heat.

Heat is a major LED module design consideration

Many people think of LED lighting as "cool" technology, both figuratively and literally and while the light output itself is not physically hot the LED itself does in fact produce heat during normal operation, although typically a lot less than a comparable light bulb such as halogen types. As mentioned above, the amount of heat is proportional to the efficiency at which an LED can produce visible light versus power consumption. All LEDs produce some amount of heat and some LEDs produce quite a bit of heat, especially true of today's high-power surface mount LEDs . LEDs generally produce heat backwards through the chip unlike incandescent sources that direct heat outward through the light beam and while most thru-hole and lower power surface-mount LEDS do not need additional cooling, the higher power LEDs generally do and often come mounted to individual heatsinks. Grouping these high-power LEDs together to create a high-output LED module amplifies the amount of heat that must be dealt with. Often in LED modules, the dielectric material used to insulate the conductive copper circuit layer from the aluminum base also helps to conduct heat from the back of the LEDs to the aluminum base which in these cases, acts as a heat sink. Active cooling of the base/heatsink may be employed depending on the amount of heat that must be conducted away from the heatsink. Heat management is a major concern when choosing the LEDs, dielectric properties, and base layer materials that go into LED modules. Almost all high-power LEDs require additional heat sinking to properly cool the LEDs and prevent damage.

The lifecycle of LEDs and LED modules.

Less efficient LEDs generate more heat and have shortened life cycles. The definition of the "life" of an LED is usually defined as the time it takes for the LED to drop to 70% light output. While a typical LED or LED module may have 10,000 to 50,000 hours of life a typical 5 watt 120 lumen high-power LED has about 5,000 hours of life which is considerably shorter. In certain applications where the efficiency and lifetime of an LED is not a concern but maximum brightness is, such as in hand-held torches, these super high output LEDs are ideal.

Color has a temperature?

Fluorescent lighting is generally cool light both in terms of thermal output and color temperature. Color temperature-wise, LED output can be warm or cool depending on the type of LEDs used which is also another feature of their use over traditional lighting which tends to be warm, fluorescents excepted. In certain applications, it is more desirable to have light that is warm, typically when incandescent lamps are being replaced such as in architectural or accent lighting and in other applications cooler lighting is required particularly in display or signage lighting as well as safety marker lighting where color shifts from yellower light are undesirable.

LED Modules = Design Freedom

LED modules may be configured in a myriad of shapes and sizes including pucks (circles), rectangles, squares, flexible strips, and more dictated by the types of LEDs used, the light output characteristics required (such as lumen output, beam width, etc...), and the intended applications. Lenses, light pipes, and other optics may be employed on top of the LEDs to produce particular lighting effects depending on the application. Individual LED modules can be connected together along cable either as off the shelf system with precut cable lengths or in the field during installation with specific cable sizes between modules to create a very flexible custom system of lights. LED modules can also be built with flexible base layers instead of rigid aluminum, making bendable strips of LEDs capable of being utilized in a host of low-profile, high light output requirement applications such as architectural lighting, display lighting, accent lighting, or safety lighting. As brightness requirements have gone up so too have improvements in heatsinking and active cooling technologies allowing the use of increasingly brighter, high-power LED modules in a wide variety of applications including hand-held torch lights, safety lighting, signage, display lighting, automotive, aerospace, and nautical marker lighting, and medial lighting.

As technology continues to increase the efficiency and brightness of LEDs their replacement of traditional light sources will likely explode into more and more applications where their unique characteristics lead to better designs and more economical products.

International Light Technologies has long been a world-wide leader in a diverse selection of off the shelf and custom light sources including LEDs and LED modules as well as precision light measurement instrumentation.