The Components of LEDs and How They Work

June 29, 2017

 

Everything happens for a reason. For some people, thinking this way makes it easier to deal with relationship problems, financial crisis, disease, death, and even natural disasters such as earthquakes. The saying that everything happens for a reason is the modern and new age version of the old religious saying: It’s God’s will. However, this is not the case when it comes to science. Every phenomenon that is happening around us have a specific scientific reason. Imagine the reason behind why the sun rises in the east and sets in the west, and why the moon changes shape from new moon to first quarter, and then to full moon, and from full moon to last quarter. This phenomenon is often called as the cause-effect relationship, in which one event (the cause) makes another event happen (the effect).

In LEDs, this cause-effect relationship explains why these tiny bulbs can generate very bright lights that can surpass other lighting devices such as the traditional incandescent bulb. So for this week, we’re going to briefly discuss in this article about the major components of LEDs, and how they work.

LED Components

1

Epoxy Lens/Case – The epoxy lens has three major functions. First, it is designed to allow most of the light to escape from the semiconductor. Second, it focuses the light (view angle) and lastly, it protects the LED semiconductor from outside elements. The epoxy totally embeds the entire unit which makes the LED virtually indestructible. There are no loose or moving parts within the solid epoxy enclosure. Non-diffused lenses that do not have glass particles in the epoxy produce a narrow viewing angle of +/-12 degrees from the centre.

Wire Bond – The wire bond is typically an interconnection between the anode (positive side) and the cathode (negative side).

Reflective Cavity – Light extraction in LEDs is one of the most its important aspect. The reflective cavity’s purpose is to make the LED’s light be brighter by focusing its light into a single point.

Semiconductor Die – It is a small block of semiconducting material, on which a given functional circuit is fabricated. It is the heart of any electronic products and contains a lot of integrated circuits and full of intelligence associated with it.

Anvil and Post – There are two leads of an LED that are used to supply input voltage. The longer lead is positive and known as Post, and the smaller is negative known as Anvil. So basically, the anvil and the post determines the polarity of the two the leads. The Anvil is also used to physically hold the chip, provide some heat-sinking, and provide some directivity to the emitted light.

How LEDs Work

Unlike the incandescent lamp that gets it light by heating the tungsten filament through passing an electric current in it for it to glow with visible light, LEDs get their light through a phenomenon called electroluminescence. Electroluminescence is a phenomenon wherein a material emanates a light when an electrical current is passed through it. This happens when electrons are sent through and fill the electron holes. An electron hole exists where an atom lacks electrons and therefore has a positive charge. Semiconductor materials like germanium or silicon are among those materials that can be “doped” to create and control the number of electron holes. Doping is the adding of other elements to the semiconductor material to change its properties. By doping a semiconductor, you can make two separate types of semiconductors in the same crystal and the boundary between the two types is called a p-n junction. A p-n junction only allows the current to pass through it in one way or direction, which is why they are used as diodes. As electrons pass through one crystal to the other they fill electron holes and they emit photons or what we call “light”.

Thanks to the advance technology now, we can have a better understanding on how these tiny little things can generate very bright lights. Through LEDs, we can say somehow that the saying “everything happens for a reason” is true.


 





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