In the past, in order to improve the luminous efficiency of white-ray SMD LEDs, engineers tried to develop large sized LED chips to achieve their goals. However, in fact, if white-ray LED chips continue to work under power supply higher than 1W, their luminous efficiency will reduce by 20%-30% on the contrary. In other words, if white-ray LEDs intend to have brightness several times larger than traditional LED chips and better voltage-current characteristic than fluorescent tubes, they need to overcome following shortages: temperature control, ensure the lifetime of LED chips, improve luminous efficiency and equalize luminescent characteristics.
The most effective method to control temperature rising is reducing the thermal resistance of LED chips during the package process. The commonly used method to extend the lifetime of white-ray SMD LEDs is applying small sized LED chips. For the equalization of luminescent characteristics, the most effective way is still optimize the package of white-ray LEDs. More specific methods are still in developing now.
The core solution is improving the cooling problem of package. Increasing power will result in drastically reduction of thermal resistance of LED chips to less than 10K/W. In order to solve this problem, many foreign G24 LED makers developed white-ray SMD LEDs with high heat-durability. In fact, high-powered LEDs will generate much more heat (more than 10 times) than low-powered LED chips. High working temperature will speed up the process of light attenuation. But the junction temperature of LED chips can exceed the allowable value and exert very limited influence on the light attenuation. After all, LED engineers started to notice that and spent more energy and money on the package cooling.
Using suitable materials can improve the service life of LED chips. For example, siliceous and ceramic packaging materials can increase the service life of LEDs by 10%. The spectrum of white-ray LED chips contains light with wavelength below 450nm, which is also known as short wavelength light. Traditional epoxy encapsulation materials will be easily destroyed by this kind of rays. Plus that the large amount of luminance of high-powered LED chips will also accelerate the deterioration of packaging materials. According to related testing reports, after 10,000-hour constant lighting, the brightness of high-powered white-ray LEDs is reduced by more than 50%, cannot meet the basic requirement of long lifetime of light sources.