The promotion and application of LED street lamps in cold regions needs to address the following key technical issues.
First, the thermal shock temperature changes may cause failure of LED devices
Since LED chips are packaged as solid solid devices, there is a mismatch between the expansion coefficient of the chip, the silicone (or resin), the metal support, and the leads, and the impact of the cold and heat shocks with large temperature differences in cold regions will make it difficult. In the process of temperature change, the silica gel expands and shrinks, and the internal stress of the device is too large.
This will cause the displacement of the LED wire bonding point to increase, leading to premature fatigue and damage of the lead. At the same time, the solder joints with poor bonding status may also be de-welded, which may cause the solder balls and chip electrodes to be de-soldered, and even cause the failure of the LED chip to fall off.
There are up to hundreds of LED devices used in LED street light. Usually, hybrid-type configuration methods are mainly used in series. If one LED fails, multiple LEDs will fail due to failure. Therefore, LEDs used in cold regions are used. In order to ensure the reliability of each LED device in a low-temperature operating environment, the street light fixtures must first set the packaging process parameters such as ultrasonic power, bonding pressure, bonding time and bonding temperature according to the temperature change characteristics of the lamp in a specific use environment.