Before we delve into the meat of the topic “how LED lights are made”, just look around for a second.
LED lights, those tiny electronic wonders, are everywhere.
Starting from acting as indicator lights in microwave ovens and stereos to being a staple component in digital display items like watches and calculators, LED lights have carved their presence almost everywhere.
Who knew the research on lasers would lead to such a massive technological breakthrough?
Though electroluminescence was discovered as early as 1907, the development of the violet LED by Herbert P. Maruska and Jacques Pankove in 1972 led to the bright blue LED light movement in 1993.
Did you know? The LED lighting market is expected to reach $105.66 billion by 2025.
The Ins and Outs of How LED Lights are Made
LED lights differ from light bulbs, essentially, in how they produce light.
Edison light bulbs are just wires, connected to a source of energy, emitting light when heated.
LED lights work on the principle of electronic excitation instead of heat generation. It works through diodes that act as electrical “valves” transferring electrons from a region of high electronic density to another of low electronic density.
The idea is simple: the more electrons passing through the “junction” or the border between the two regions, the brighter the light emitted. The process is made possible only when the valve is on.
Each LED light is made up of multiple light-emitting diodes (LEDs) – the most basic yet ultimate component of an LED light.
If you understand how an LED is built, you know how an LED light is made.
A Quick Look into the LED Manufacturing Process
While the complete process is complicated and outside the scope of this article, here’s the gist of how an LED is made.
Diodes are made of ultra-thin layers of semiconductor material with varying electronic densities, also known as “wafers”, to facilitate the flow of electrons from an electron-rich region to an electron-scarce one.
“How is a semiconductor wafer produced?”
The semiconductor materials or components, such as gallium, phosphor, and arsenic, are mixed and forced into a solution under high temperature and pressure conditions.
The solution is layered with liquid boron oxide, also known as liquid encapsulation or Czochralski crystal growth method, to block its turning into gas.
Finally, a rod is dipped into the solution and pulled out slowly that allows the solution to cool and solidify into crystals on the end of the rod as ingots (or boule).
This ingot is then sliced into semiconductors wafers.
The most commonly used semiconductors used for LED lightings are gallium phosphide (GaP), gallium arsenide (GaAs) and gallium arsenide phosphide (GaAsP).
While semiconductors are naturally crystalline substances, they need impurities in high quantities to be able to conduct electricity.
Imagine a chocolate chip cookie where the semiconductor is the cookie and the impurities are the chocolate chips on it (well, something like that). While the substance here is the cookie itself, the chips are what make it worthwhile.
Or, in other words, while the semiconductor already possesses the light-emitting potential, it is the impurities, or as per industry-speak, called “dopants”, that serve as catalysts to put it into action. It is the dopants that create the excess or deficit of electrons.
The impurities usually used in the LED manufacturing process are nitrogen and zinc, or even silicon, germanium or tellurium in some cases.
LED Lights: Adding the Impurities
Adding impurities is done through a process called Liquid Phase Epitaxy where the wafer is slid under reservoirs of molten GaAsP (or the material used). This is used to grow extra layers of material on the wafer on which patterns are created using photo-resist, a light-sensitive compound, solidified under low-temperature of about 215 degrees Fahrenheit or 100 degrees Celsius.
Following that, the wafer is put in a heated, vacuum chamber where molten metal evaporates on the pattern created by the photo-resist. Soon after, the photo-resist is cleaned off with acetone. So, only the residue of metal impurities remain.
One 2-inch semiconductor wafer can yield 6,000 dies. Can you see now why diodes are usually so small?
To complete the diode, the layers of the semiconductor wafer are connected by wires that not only stick onto the semiconductor but also can withstand soldering or heating. Gold and silver are used for the purpose – they work well with gallium on the wafer surface.
LEDs go inside plastic molds, like those lucite paperweights with objects floating inside. But the whole design depends on the specific purpose it is meant to serve, either with a connector or a lens at the end.
That’s pretty much it.
But it’s only scratching the surface.
For the knowledge seekers, if you want to know more about it, read Klaus Gillessen’s Light-Emitting Diodes: An Introduction (a good resource).
For high-quality LED lights, check out our shop.