With the rapid development of LED lighting technology, in many cities in China, there are many LED street lights in road lighting. Especially after the luminous efficacy of high-power LED devices exceeds 100 lm/W, LED street lamps have been widely recognized as the development trend of road lighting. In 2009, several cities in China organized the evaluation and testing of LED road lighting products. Most of the LED street lamp products made significant progress in key technical indicators such as light distribution curve and system light efficiency, and the compliance and energy saving effects of road lighting standards. Other aspects have met the requirements of relevant standards and specifications.
Despite the rapid development of LED street light technology, most LED street lamp manufacturers neglect the special technical requirements in the cold application environment during product development. A common misconception is that LEDs in the cold area are good for heat dissipation and are not prone to failure. As everyone knows, in the cold application environment, there are more stringent technical requirements for LED street lamps, mainly in the following two aspects:
1. The temperature in the cold region is low, and the temperature difference is large. The sudden thermal shock and long-term low temperature work have stricter quality requirements for the device;
2. LED street lights used in cold areas must consider preventive measures to prevent ice condensation.
In view of the above reasons, the promotion and application of LED street lamps in cold regions need to solve the following key technical problems.
First, the temperature change of thermal shock may cause the failure of LED devices
Due to the solid components of the solid state after the LED chip is packaged, there is a mismatch between the expansion coefficients of the chip, the silicone (or resin), the metal bracket and the lead, and the influence of the thermal shock of the cold region is large. During the temperature change of silica gel, the expansion and contraction are intensified, and the internal stress of the device is too large, which will cause the displacement of the LED wire bonding point to increase, and the lead wire to be fatigued and damaged prematurely. At the same time, the solder joints with poor bonding state may be de-soldered, which may cause the solder balls and the chip electrodes to be desoldered, and even the LED chip may be delaminated.
As for LED streetlights, there are hundreds of LED devices, which are usually connected in series. If one LED fails, it will cause multiple LEDs to fail. Therefore, LEDs used in cold regions are used. Street lamps must first set reasonable process parameters such as ultrasonic power, bonding pressure, bonding time and bonding temperature according to the temperature variation characteristics of the lamps in a specific use environment to ensure the reliability of each LED device under low temperature operating conditions. .
Second, the reliability of LED drive device low temperature operation
Another key technical challenge is the reliability of LED street light drives in low temperature operating environments. At present, most LED street lamp driving power sources exhibit different types of soil and water dissatisfaction in the cold and low temperature environment. The more prominent characteristics are the low temperature failure and the high failure rate in the long-term low temperature operation environment.
Shenzhen Yetnorson Technology Co., Ltd. , http://www.yetnorson.com