Causes of packaging failure of LED lamp beads affected by high temperature
Publish：Shenzhen Teng Jie Optoelectronics Technology Co., Ltd. Time：2022-08-12
Analysis of the causes of package failure caused by high temperature of LED lamp beads, and it is predicted that the life of LED lamp beads will exceed 50000 hours. However, this life refers to the theoretical life and the service life of lamp beads at 25 ℃. In the actual use process, it will encounter high temperature, high humidity and other harsh environments, amplify the defects of LED lamp beads, accelerate the aging of materials, and make the LED lamp beads quickly fail. The influence of temperature on the packaging reliability of LED lamp beads through the experimental research on high humidity environment, it is found that the invasion of moisture not only makes the LED light efficiency decline, but also may lead to the catastrophic failure of LED lamp beads. Through the high temperature and high humidity reliability acceleration experiment at 85 ℃ / 85% RH, it is found that moisture plays an important role in the formation of delamination defects. The delamination phenomenon causes the light efficiency of led to decrease, and different chip surface roughness leads to different failure modes.
The reasons why the temperature makes the LED lamp beads and the system fail are:
1. Due to the mismatch of thermal conductivity between packaging materials and the uneven temperature gradient and temperature distribution, cracks may occur inside the materials or delamination may occur at the interface between materials. These cracks and delaminations will cause the light efficiency to decrease. The delamination between the chip and the phosphor layer can reduce the light extraction efficiency. The delamination between the phosphor layer and the potted silica gel can reduce the light extraction efficiency by more than 20%. The delamination between the silica gel and the substrate may even cause the gold wire to break and cause catastrophic failure.
2. High temperature will accelerate the degradation of packaging materials and reduce the performance.
3. Junction temperature has a great influence on the performance of LED beads. Too high junction temperature will cause the phosphor layer to burn black and carbonize, resulting in a sharp reduction in the luminous efficiency of LED beads or a catastrophic failure. In addition, due to the mismatch of refractive index and thermal expansion coefficient between silica gel and phosphor particles, too high temperature will reduce the conversion efficiency of phosphor, and the higher the proportion of phosphor doped, the worse the light efficiency
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