Several factors impact the life of LED

LED products of potential failure factors can be roughly divided into five kinds: chip failure, thermal stress failures, electrical stress failure, package failure and assembly failure. In these five cases, any state of affairs can trigger LED products failure in different level, and may also lead to other modes associated works, thus exacerbating the LED failure.

1         phosphor degradation.

LED phosphors efficiency reduce will cause the luminescence properties change, which perform as color temperature rise, when cooling is bad, phosphor is easy to aging, and will make the conversion of yellow phosphor composition decrease, lead to a drop in the LED light output and cause color deviation.

2.  Different phosphors degeneration.

    Different phosphors used in white light will degrade with heat and aging, But different decay rate caused different light colors. The purple and pink light LED manufacturing usually use organic phosphor composition, After several hours of operation will result in degradation of the output light color migration.

3     Resin degradation.

The main LED packaging materials are epoxy resin. Epoxy resin has excellent electrical insulation properties, the drawback is hygroscopic, heat resistance, easy to aging, easy change color on high temperature and short wave light, thus have a certain impact to LED life.  Epoxy resin material will aging by UV irradiation, reduce transparency, absorb some wavelengths of light, resulting in efficiency reduced.

4     Thermal stress.

Most of the LED sudden failure are caused by thermal stress. When the epoxy resin reaches the glass transition temperature, it will rapidly expand in the semiconductor and bonding contacts, causing mechanical stress, weaken epoxy resin, or even tear. Conversely, a low temperature will result in rupture of the package

The performance of LED lifetime mainly as luminous decay, Commonly we take the LED invalidation when the light output of LED decay to 70% or 50%. Because LED is a high-reliability device which’s life in general will be more than a few thousand hours or even more than ten thousand hours. Direct measurement of waiting for the light failure to specify a value in industry application is very difficult.The reliability of solid state lighting system is a very important parameter, a complete solid-state lighting system should have high quality, high reliability, low failure rate, high life and other characteristics etc.

The most important factors of stress include humidity, temperature, current, voltage, mechanical, chemical and optical radiation. Interaction of these stresses, applied to the LED products, the formation of various failure modes final impact product’s life.

Studies LED device failure in different environments is crucial to improve the reliability of LED devices. Through high and low temperature impact, increasing the load, recycling aging LED devices to measure and test the LED life, Depending on the conditions of use create different failure modes, in particular, taking the progressive failure into account.

First thing to note is that the LED light failure characteristics, traditional lamps generally measured after lit 100 hours, but for LED lamps is too short.Followed by the thermal characteristics of the LED, LED light, color and so on all is associated with the thermal features. In addition to the thermal characteristics of the LED itself, the heat dissipation design of LED lamp may also affect the life of LED.  Many luminaire thermal design varies greatly, resulting in some LED lighting efficiency is low, short life, this is actually not the problems of the LED, but the poor lighting design. For example, At -30 ° C in Russia, LED does unable to launch; then cooling is a serious problem of LED when in the equatorial regions. Environmental factors make LED life can not be guaranteed, which is the biggest problem. LED can reached 20,000 hours in the room, but in a different environment, it is not only to cooling but also waterproof, both of which are contradictory to some extent, these are presents a challenge to the lifetime of LED.