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designs of LEDs - The semiconductor crystal
Silicium belongs to the most frequent elements of the earth's crust. It occurs however not purely, but as SiO2 (silicium dioxide or quartz)and must be converted by precipitation processes into pure silicium.
Lattice defects in this crystal disturb however the movement of the electrons and in such a way that the crystalline pure silicium must be “cleaned?by a fusion procedure (Zohnenschmelz or Czochralski process) and "pulled" into large single crystals. These crystals has a diameter of 10-20 cm and a length of up to 2 meters. So a purity can be achieved by one foreign atom on 10 to high 9 Siliciumatomen.
This pure crystal is cut now into thin disks, called Wafern. Wafer costs today approx. around 1000, - Eur. The DOPING crucial for LEDs (addition of additives) can be achieved either with pulling the crystal or with the Wafern by vaporizing with 1000°C with the foreign atoms or by the bombardment with ions of the additive in small accelerators.
Now the endowed Wafern are cut into some hundred small “chips? which exhibit a thickness of only approx. 250 µm. These tiny small and hardly with free eye visible pieces of semiconductor crystal are responsible for the light generation of our LED.
Light emitting diodes are used into many different designs.
Mainly however plastics and synthetic resin applications for the lens are used. In addition, glass or metal housings is used with bright LEDs. LEDs zum Einsatz.
The plastic body, which is formed like a lens and lies over the crystal, lowers the limit angle of the total reflexion and bundles, therefore increases the radiating power.
With stronger LEDs also glass lenses are used. Metal housings, mostly from aluminum, take over mainly the task of the heat dissipation, thus cooling.
Generally, the LED can be used the same way as other general purposed semiconductors. However, the following prcautions must be taken to protect the LED.
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