Production of LED luminaires
Today LED lighting systems are considered to be the best solution, both in terms of energy efficiency and service life.
Unlike ordinary luminaires utilizing incandescent lamps or gas discharge lamps, light-emitting diodes (LEDs) are the light source in LED luminaires. The luminous efficiency of modern LED luminaires (even after accounting for all internal losses) may exceed 100 lm/W, which is 8-10 times higher than the luminous efficiency of luminaires with incandescent lamps and higher than the same parameter for the majority of luminaires with gas discharge lamps (approximately 50-60 lm/W).
The guaranteed service life of modern white LEDs is 50,000 hours, while their rated service life is up to100,000 hours. Compare these parameters with the service life of incandescent lamps (1,000 hours) and of daylight lamps (4-5,000 hours).
LED luminaires are characterized not only by extraordinary luminosity, but also by radically new production technology.
LEDs are the basis of LED luminaires, and LED production is the most complex operation (technologically). It includes the growth of composite films on the surface of a sapphire or silicon carbide substrate. This operation requires especially pure gases, while the cost of equipment for epitaxy (the method of gas deposition used, during which the crystal material is directly grown on the substrate surface) may reach 2 million dollars.
After that the planar processing of the grown films is carried out, and the р-n structure of the LEDs is formed. Several thousand of LED microchips are obtained from a single substrate. Then phosphor-covered chips are binned (sorted) by luminous flux, voltage, colour temperature and other parameters.
The chips produced are placed into a housing and fitted with so called primary optics, which forms the baseline LED light intensity distribution curve (LIDC).
Only after that the LED is ready and may be used in the production of luminaires. Conventionally speaking, it is the landmark that separates the “semiconductor” part of LED luminaire production technology from the “lighting” one. That’s why LED manufacturers usually don’t produce luminaires – it’s simply not their “business”.
Meanwhile, the LEDs from the world’s leading manufacturers are used by producers of LED luminaires and lamps all around the globe. Such LEDs have the highest luminous efficiency (i.e. “luminous flux / wattage” ratio) and are characterized by high quality and long service life. The current level of luminous efficiency for modern serial LEDs is 130-160 lm/W, and it’s only the beginning.
There are approximately ten leading LED manufacturers, whose LEDs are used in production of LED lamps and luminaires. Their products are widely used in LED lighting manufactured all around the world. First of all, there is Nichia Corporation (Japan), which developed high-brightness white-light LEDs in 1996 and thus created the trend in LED lighting. The top places in the world list are also occupied by Samsung (South Korea), Osram (Germany), Cree (USA), Philips (Netherlands). And only two manufacturers - Cree and Philips – also produce luminaires.
It should be noted here that the use of the highest quality LEDs is an essential, but not sufficient condition for production of quality LED luminaires. Other fixture components such as electronic parts of the power supply (driver), optical system, etc. should also be of high quality, not to mention the construction of the luminaire and especially the heat removal.
And despite all their superior characteristics, LEDs have one significant drawback – their luminous flux and service life begin to decrease dramatically in high temperature conditions.
We can say that the heat removal problem is a common thread running through the whole manufacturing chain of LED luminaires: at the LED level it is heat removal from the р-n junction area to the LED housing; on the fixture level it is heat removal from the LED to the printed-circuit board (PCB) and then from PCB to the radiator, which at finally dissipates the heat to its surroundings. And whichever LEDs are used, inefficient heat removal may literally destroy the luminaire.
Taking into account that the service life of LED luminaire components should be several times higher than the service life of standard luminaire components, quality control plays a critical role in the process.
For example, the Russian company, AtomSvet, one of the leading national manufacturers of LED luminaires for severe and extreme operational conditions, uses quality control in all the manufacturing stages (in warehousing, as well as in goods inwards for production).
That is why top Russian companies seek to certify their production and quality management system for conformance to the ISO 9001:2008 international standard. This requirement is defined by life itself or rather, the market.
The luminaire production starts with the manufacture of the LED module – a PCB with LEDs soldered onto it. One of the advanced trends is the use of PCBs produced with aluminum oxide technology (ALOX). The essence of this technology lies in the formation of a dielectric on the surface of the metal and within it. PCBs manufactured with the use of this technology have a high heat conductivity and perform the heat removal efficiently. The Russian manufacturer, AtomSvet, for instance, uses such boards in its new product lines of luminaires.
Secondary optics cover the LEDs mounted on the board, and produce the required light intensity curve. During the final assembly step the LED module (or several modules) are mounted together with other fixture components in the aluminum housing and usually covered with the protective polycarbonate or borosilicate glass from the front.
Such a complex three-component optical system (primary and secondary optics, protective glass) has its own disadvantages, for instance a relatively high level of light losses, which mostly negates the high parameters of LED luminous flux. That’s why luminous flux of the luminaire is always lower than the total luminous flux of the LEDs. Consumers should pay special attention to this fact, which is not always made clear by LED lighting manufacturers.
One of the ways to reduce optical loss is to create multi-lenses, which simultaneously perform the functions of the secondary optics and protective glass. Just such an innovative method has been used in AtomSvet luminaires from the very beginning of their batch production in 2009. The use of such optical system additionally guarantees high-grade dust and moisture protection, as well as high values of impact resistance and vibration resistance. Years of successful operation show that such method is fruitful, and today other Russian manufacturers of LED luminaires have also started using it.
Thus, production of LED luminaires is a complex and high-tech process which has many pitfalls of various kinds. When choosing the manufacturer of LED luminaires, one should pay attention not only to the claimed parameters, but also to the type of LEDs used, the availability of product certificates (not only GOST, but also European ones - СЕ, GS, ENEC) and certificates of tests performed by independent organizations. And, finally, the quality is guaranteed in case of a long (at least 3-5 years) presence of the manufacturer on the LED lighting market, as well as the presence of a list of successfully implemented projects supported by positive consumer comments.
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