LED Failure Mechanisms and Lifetime Typically, LEDs do not absolutely croak as most traditional crystallise sources do; instead, their optical skill degrades monotonically over time. In other words, opepaced at a constant disgust live the amount of light emitted by an LED would simply decrease over time. The rate of adulteration is primarily determined by the driving force current and operational temperature of the LED, and the lifetime to a particular amount of humiliation give notice be approximated by: [pic] Where C and n atomic number 18 constants (depending on the selected level of humiliation), IF is the drive current, Ea is the thermal activation energy of the LED, k is Boltzmans constant, and Tj is the spliff temperature of the LED. The above relationship covers a across-the-board range of degradation mechanisms. The primary degradation mechanisms in LEDs are: 1) Defects in the see-through structure of the semiconductor material in and near the PN stick called dislocations or dark line deformitys. This defect effectively subjects the quantum energy of the LED. GaN-based LEDs are more immune to this effect. 2) admixture diffusion from the electrodes and join into the semiconductor material.
The effect is that higher drive currents are needed, thusly producing higher internal temperatures, both of which reduce lifetime. 3) Reduced exertion of phosphors in phosphor-coated LEDs. For example, the Stokes efficiency of the phosphors stooge be degraded by the absorption of contaminates. 4) insulation of metals in the cacoethes sink bond, often called voi ding. 5) moisture absorption into the semi! conductor. 6) motionless discharge (ESD) due to poor manipulation and assembly can produce latent defects leading to deepen degradation. 7) Weak or cold wire bonds to the electrodes. These tend to memorialize immediately or within a few hours of operation.If you motivation to get a full essay, order it on our website: OrderCustomPaper.com
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