As a society, we are fascinated by how things are put together. What goes into their components? How are those components then assembled into a whole? As one of the top LED lighting manufacturers in the United States, Garden Light LED wanted to take this opportunity to walk you through the process of how an LED light is created.
The television show How It’s Made featured LED lighting on a recent program, but it was more focused on how the fixture is created, and not on the LED itself. So here is a supplement to that video, walking you through the steps taken to create the LED bulb that will ultimately go into a wide variety of fixtures, from the tube lighting such as the ones seen in the episode, to spotlights, water lighting, garden lighting, path lighting, and many more.
- A Semiconductor Wafer is Created.
This forms the core of what will become the LED light. The materials used to form the wafer depend entirely on what color it will be: gallium arsenide (GaAs), gallium phosphide (GaP), or gallium arsenide phosphide (GaAsP) all have different wavelengths, and will produce different colors. In many cases, to achieve the right color, mixes of two or more of the gasses are used. These gases are put into a chamber, and using a combination of extremely high heat and pressure, they are liquefied. To keep the solution together, often a solution of liquid boron oxide is formed in a layer over the top.
Once the liquid is a uniform composition, a rod is dipped in and slowly pulled back out again, allowing the solution to cool and crystalize as it emerges, forming a long, thin, cylindrical ingot. From there, the rid is sliced into extremely thin wafers, and then polished until it is absolutely smooth, which is important in the next phase of the process.
- Adding Layers.
One single layer of the semiconductor isn’t going to be enough to produce the required light color or strength. Instead, new layers of crystal have to be grown on top of the existing wafers – which is why they have to be perfectly smooth. The slighting imperfection can degrade the performance or life of the LED significantly. The more uniform and perfect the surface of each layer is, the more they will all act together as one, single crystal. Imperfections encourage the crystals to all “do their own thing” which is not a desired result.
- Adding Metal Contacts.
The next step in the process is to add the metal contacts that will conduct electricity through the semiconductor crystals. The pattern used for the metal is determined in the design phase, before the lights go to manufacture, and varies based on whether the LED is going to be used singly, or in combination with other diodes. The patterns are created with a light-sensitive compound called photoresist, which is deposited in drops onto the wafer’s surface while it spins, and then is hardened using a brief, low-temperature baking process. A mask is then laid over the top of the material and exposed to ultraviolet light, which is what forms the desired pattern. Exposed areas are washed away, and a contact metal is evaporated onto the remaining pattern, filling in the exposed areas. This process takes place under high heat, and in a vacuum chamber, and can take several hours to allow the metal and semiconductor wafer to completely bond together at a chemical level. Once the diode comes out of that process, it is then cut apart, either by snapping it along a crystal plane, or by using a diamond saw; each small segment produced is known as a “die”.
- Mounting and Packaging.
In this stage, the individual dies are mounted to the appropriate package. The dies are mounted to metal leads that are usually around two inches long, and wires are added to connect the dies to the circuit; the wires are usually gold, as it is soft enough to deform slightly and adhere to the surface of the other metals.
Once the LED dies are wired, the entire assembly is sealed in plastic. The wires and die are suspended in a mold that is the exact shape and size of the final package, and a liquid plastic or epoxy is poured in. once that liquid cures, the entire assembly is removed from the mold, and the LED is complete.
Creating LED lights is a highly technical process, where every step must be precisely executed in order to meet the extremely stringent quality control requirements that Garden Light LED has for our lights. Once the LEDs themselves are created, they then move into the process where they are inserted into the wide range of outdoor lighting fixtures we create.
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