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Let's take a look at the manufacturing steps for a typical LED light bulb meant to replace a standard incandescent bulb with an Edison Screw. You will see that it is a very different process from the highly automated processes used to manufacture our familiar incandescent bulbs. And, despite what you might imagine, people are still very much a necessary part of manufacturing process, and not just for testing and Quality Assurance only.
Once the larger sheets of LED circuit boards have passed through a solder reflow oven (a hot air furnace that melts the solder paste), they are broken up into the individual small circuit boards and power wires manually soldered on.
The small power supply housed in the body of the light bulb goes through a similar process, or may be delivered complete from another factory. In either case, the manufacturing steps are the same; first the PCB passes through SMT lines, then it goes to a manual dual in-line package (DIP) assembly line where a long row of factory workers add one component at a time. DIP refers to the two parallel rows of leads projecting from the sides of the package. DIP components include all integrated chips and chip sockets.
While LED lights burn several times longer than incandescent or CFLs and require less than half the energy, they need some form of passive heatsink keep the high-power LEDs from overheating. The LED circuit board, which is made from 1.6-2mm thick aluminum, will conduct the heat from the dozen or so LED elements to the metal heatsink frame and thus keep temperatures in check. Aluminum-backed PCBs are sometimes called "metal core printed circuit boards," and though made of a conductive material the white coating is electrically isolating. The aluminum PCB is screwed in place within the heatsink which forms the lower half of the LED light bulb.
Shell assembly consists of locking the shell in place with screws. A plastic shell covers the power supply and connects with the metal heatsink and LED circuit board. Ventilation holes are included to allow hot air to escape. Wiring assembly for plug socket requires soldering wires to the bulb socket. Then shell is attached.
Next, the completed LED light is sent to burn-in testing and quality control. The burn-in test typically lasts for 30 minutes. The completed LED light bulb is then powered up to see if it is working properly and burned in for 30 minutes. There is also a high-voltage leakage and breakdown test and power consumption and power factor test. Samples from the production run are tested for high-voltage leaks, power consumption, and power factor (efficiency).
After a final check to make sure all the different parts of the LED light are tight, then it is packed into individual boxes, and bulbs are shipped.
So, if you have wondered why LED light bulbs are so expensive today, this explanation of how they are manufactured and how that compares to the manufacture of traditional light bulbs should help. However, it also reveals why the cost will fall pretty dramatically over the next few years. Just as the cost of manufacturing other semiconductor-based products has fallen dramatically due to standardization, automation and other key steps along the manufacturing learning curve, the same inexorable forces will drive down the costs of LED light bulb production.
