In order to extend the lifetime of LED chips, the most commonly applied method is to change sealing materials, mixing fluorescent materials within them. Siliceous sealing material is more effective in slowing down the material deterioration and lighting attenuation than traditional epoxy resin sealing materials used on blu-ray/ultraviolet LED chips.
The epoxy resin sealing material can absorb around 45% rays with wavelength of 400-450nm, while siliceous sealing materials absorb less than 1% rays within this range. According to estimation, the lifetime of LED chips using epoxy resin packaging materials (light attenuation reach 50%) is less than 10,000 hours, while siliceous package could extend this period to more than 40,000 hours. This is almost equivalent to the service life of the entire lighting device. In another word, the corresponding LED lamp is in no need to replace the LED chips during its operation lifetime. However, siliceous resin is a kind of high elasticity soft materials. Special production technologies must be used during the production process. In addition, dust could be easily attached to siliceous resin materials. Thus developing improved surface characteristic technologies are necessary in the future.
Although siliceous sealing materials can ensure a 40,000-hour service life of LED chips, but the lighting application industry have a different view. The main debate is on the service life of traditional incandescent lamps and fluorescent lamps, which has been defined as “brightness dropped to less than 70%”. As we mentioned before, the approximate time of 50% light attenuation of LED lights is 40,000 hours. If calculated as the specification of 70%, then the lifetime of LED chips will recued to 20,000 hours. There are two major countermeasures for this condition:
- Limit the heat generation of white-ray LEDs;
- Stop using the resin encapsulation;
It is generally believed that, the LEDs’ service life could be extended to 40,000 hours (30% light attenuation) by using above two methods. Cooling PCBs is a mostly used method to limit the temperature rising of white-ray LED chips. Basically, the encapsulation resin material will rapidly deteriorate in the high temperature state and under highlight. Stop using resin package can completely eliminate the deterioration, since led tunnel light rays are reflected in the encapsulating resin. Using special resin reflecting plates which are able to change the traveling direction of light from chip side surfaces, the entire light extraction will be sharply dropped. This is the main reason that all LED manufacturers choose to use ceramic and metal based package.