Everyday life we ??in the application of LED lighting products often occur from time to time issue such kind, LED products in the beginning when the product is working properly, but after some time there will be light dark light, flashing, fault, intermittent light other phenomena, caused serious damage to the product. Reasons for this phenomenon caused roughly:
1. Applications, the welding process problems, such as welding temperature soldering time is too long, did not make anti-static work, etc., more than 95% of these problems are caused by the packaging process.
2. LED itself cause quality or production processes. Prevention methods are:
1 good solder process control.
(2) aging of the product tested.
Aging is an important guarantee for the reliability of electronic products, the production of the final product is an essential step. LED products can improve performance after aging and contribute to post-use performance and stability. LED aging test in product quality control is a very important part, but it is often overlooked in many cases, can not be correct and effective aging. LED aging tests are based on product failure rate curve that is characteristic of the bathtub curve measures taken in order to improve product reliability, but this method is not required, after aging test at the expense of the life of a single LED products for the price.
LED aging methods include constant voltage constant current aging and aging. A constant current source is a current at all times constant. Has a frequency problem, it is not a constant. It is AC or pulsating current. AC or pulse current source can be designed to a valid value constant, but the power supply is not called “constant current source.” Aging is the most constant LED current job characteristics, LED aging is the most scientific way; overcurrent impact of aging is the manufacturers latest used as a means of aging through the use of adjustable frequency, current adjustable constant current source for such aging in order to determine in a short life expectancy of LED quality, and can pick out a lot of the hidden dangers of conventional aging can not be singled out LED. Effectively prevent failure-PTC thermistor temperature LED current limiting device used in recent years, light emitting diodes (referred to as LED) have made tremendous progress in the development: for indicator development from pure light output of 100 lumens high power LED . Soon after, LED lighting costs will be reduced with the traditional cold cathode fluorescent lamp (referred CCFL) similar levels. This makes it the LED’s growing interest in the following applications: automotive lighting, LED light sources inside and outside the building, as well as laptop or TV LCD screen backlight. High-power LED technology development to improve the design stage of the cooling requirements. Like all other semiconductor Like, LED can not be overheated, so acceleration output weaken, or cause the worst condition: completely ineffective. Compared with incandescent lamps, although the high-power LED with higher efficiency, but the input power is still a sizeable part of the light energy into heat energy instead. Thus, reliable operation requires a good heat dissipation, and requires consideration in the design phase high-temperature environments.
Design LED drive circuit size, we must also consider the temperature factors: its forward current must be selected to ensure that even if the ambient temperature reaches the maximum value, LED chip is not overheating. As the temperature increases, the need to reduce the maximum allowable current, that is derated to achieve cooling. LED manufacturers to derating curve into their product specifications.