The reason why LED lamp beads are affected by high temperature and lead to package failure
The life expectancy of LED lamp beads is predicted to exceed 50,000 hours. But this life refers to the theoretical life, the life of the lamp beads at 25 ℃. In the actual use process, harsh environments such as high temperature and high humidity will be encountered, which will magnify the defects of LED lamp beads, accelerate the aging of materials, and cause LED lamp beads to fail quickly.
The effect of temperature on the reliability of LED lamp bead packaging
Through experimental research on high-humidity environment, it is found that the intrusion of moisture not only reduces the luminous efficiency of LEDs, but also may lead to catastrophic failure of LED lamp beads. Through 85℃/85%RH high temperature and high humidity accelerated reliability experiments, it is found that moisture plays an important role in the formation of delamination defects. The delamination phenomenon reduces the light efficiency of LEDs, and the surface roughness of different chips is different. different failure modes.
The reason why the temperature makes the LED lamp beads and the system fail is:
1. Due to the mismatch of thermal conductivity between packaging materials, the uneven temperature gradient and temperature distribution, cracks may occur inside the material or delamination may occur at the interface between the materials. These cracks and delamination will cause the light efficiency to drop. The delamination between the chip and the phosphor layer can reduce the light extraction efficiency. The delamination between the phosphor layer and the potting silica gel can reduce the light extraction efficiency by more than 20%. . Delamination between the silicone and the substrate can even cause the gold wire to break, resulting in catastrophic failure.
2. High temperature will accelerate the degradation of packaging materials and reduce performance;
3. The junction temperature will have a great impact on the performance of the LED lamp beads. Excessive junction temperature will cause the phosphor layer to burn black and carbonize, which will drastically reduce the luminous efficacy of the LED lamp beads or cause catastrophic failure.
In addition, due to the mismatch between the refractive index and thermal expansion coefficient between the silica gel and the phosphor particles, too high temperature will reduce the conversion efficiency of the phosphor powder, and the higher the proportion of phosphor powder doped, the more severe the decrease in luminous efficiency.
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