| One-hundred-and-thirty years ago, Thomas Edison | | | | whole lot different than making a computer |
| completed the first successful sustained test of | | | | motherboard. The companies making the LEDs |
| the incandescent light bulb. With some incremental | | | | themselves are generally not in the lighting |
| improvements along the way, Edison's basic | | | | business, or it is a minor part of their business. |
| technology has lit the world ever since. This is | | | | They tend to be semiconductor houses that are |
| about to change. We are on the cusp of a | | | | happy cranking out their product, which is why |
| semiconductor-based lighting revolution that will | | | | prices on high-output LEDs has fallen so much in |
| ultimately replace Edison's bulbs with a far more | | | | the last 15 years. |
| energy-efficient lighting solution. Solid state LED | | | | LED bulbs themselves are expensive in part |
| lighting will eventually replace almost all of the | | | | because it takes a number of LEDs to get |
| hundreds of billions of incandescent and | | | | wide-area illumination instead of a narrow beam, |
| fluorescent lights in use around the world today. In | | | | and the assembly cost adds to the overall price. |
| fact, as a step along this path, President Obama | | | | In addition, assemblies consisting of arrays of |
| last June unveiled new, stricter lighting standards | | | | LEDs create more opportunities for product |
| that will support the phasing out of incandescent | | | | defects. |
| bulbs (which already are banned in parts of | | | | An LED light consists of four essential |
| Europe). | | | | components: an LED circuit board, a heatsink, a |
| To understand just how revolutionary LED light | | | | power supply, and a shell. The lights start out as |
| bulbs are as well as why they are still expensive, | | | | bare printed circuit boards (PCB) and high |
| it is instructive to look at how they are | | | | luminance LED elements arrive from separate |
| manufactured and to compare this to the | | | | factories which specialize in making those |
| manufacture of incandescent light bulbs. This | | | | components. LED elements themselves create a |
| article explores how incandescent light bulbs are | | | | bit of heat, so the PCB used in lighting fixtures is |
| made and then contrasts that process with a | | | | special. Instead of the standard non-conductive |
| description of the typical manufacturing process | | | | sandwich of epoxy and fiberglass, the circuit |
| for LED light bulbs. | | | | board is laid out on a thin sheet of aluminum |
| So, let's begin by taking a look at how traditional | | | | which acts as a heatsink. |
| incandescent light bulbs are manufactured. You will | | | | The aluminum PCB used in LED lighting is coated |
| find that this is a classic example of an automated | | | | with a non-conducting material and conductive |
| industrial process refined in over a century of | | | | copper trace lines to form the circuit board. |
| experience. | | | | Solder paste is then applied in the right places and |
| While individual incandescent light bulb types differ | | | | then Surface Mount Technology (SMT) machines |
| in size and wattage, all of them have the three | | | | place the tiny LED elements, driver ICs, and other |
| basic parts: the filament, the bulb, and the base. | | | | components onto the board at ultra high speeds. |
| The filament is made of tungsten. While very | | | | The round shape of a traditional light bulb means |
| fragile, tungsten filaments can withstand | | | | that most LED printed circuit boards are circular, |
| temperatures of 4,500 degrees Fahrenheit and | | | | so for ease of handling several of the smaller |
| above. The connecting or lead-in wires are | | | | circular PCBs are combined into one larger |
| typically made of nickel-iron wire. This wire is | | | | rectangular PCB that automated SMT machinery |
| dipped into a borax solution to make the wire | | | | can handle. Think of it like a cupcake tray moving |
| more adherent to glass. The bulb itself is made of | | | | from one machine to the next along a conveyor |
| glass and contains a mixture of gases, usually | | | | belt, then at the end the individual cupcakes are |
| argon and nitrogen, which increase the life of the | | | | snapped free from the tray. |
| filament. Air is pumped out of the bulb and | | | | Let's take a look at the manufacturing steps for a |
| replaced with the gases. A standardized base | | | | typical LED light bulb meant to replace a standard |
| holds the entire assembly in place. The base is | | | | incandescent bulb with an Edison Screw. You will |
| known as the "Edison screw base." Aluminum is | | | | see that it is a very different process from the |
| used on the outside and glass used to insulate the | | | | highly automated processes used to manufacture |
| inside of the base. | | | | our familiar incandescent bulbs. And, despite what |
| Originally produced by hand, light bulb | | | | you might imagine, people are still very much a |
| manufacturing is now almost entirely automated. | | | | necessary part of manufacturing process, and not |
| First, the filament is manufactured using a process | | | | just for testing and Quality Assurance either. |
| known as drawing, in which tungsten is mixed | | | | Once the larger sheets of LED circuit boards have |
| with a binder material and pulled through a die (a | | | | passed through a solder reflow oven (a hot air |
| shaped orifice) into a fine wire. Next, the wire is | | | | furnace that melts the solder paste), they are |
| wound around a metal bar called a mandrel in | | | | broken up into the individual small circuit boards |
| order to mold it into its proper coiled shape, and | | | | and power wires manually soldered on. |
| then it is heated in a process known as annealing, | | | | The small power supply housed in the body of |
| softening the wire and makes its structure more | | | | the light bulb goes through a similar process, or |
| uniform. The mandrel is then dissolved in acid. | | | | may be delivered complete from another factory. |
| Second, the coiled filament is attached to the | | | | In either case, the manufacturing steps are the |
| lead-in wires. The lead-in wires have hooks at their | | | | same; first the PCB passes through SMT lines, |
| ends which are either pressed over the end of | | | | then it goes to a manual dual in-line package (DIP) |
| the filament or, in larger bulbs, spot-welded. | | | | assembly line where a long row of factory |
| Third, the glass bulbs or casings are produced | | | | workers add one component at a time. DIP |
| using a ribbon machine. After heating in a furnace, | | | | refers to the two parallel rows of leads projecting |
| a continuous ribbon of glass moves along a | | | | from the sides of the package. DIP components |
| conveyor belt. Precisely aligned air nozzles blow | | | | include all integrated chips and chip sockets. |
| the glass through holes in the conveyor belt into | | | | While LED lights burn several times longer than |
| molds, creating the casings. A ribbon machine | | | | incandescent or CFLs and require less than half |
| moving at top speed can produce more than | | | | the energy, they need some form of passive |
| 50,000 bulbs per hour. After the casings are | | | | heatsink keep the high-power LEDs from |
| blown, they are cooled and then cut off of the | | | | overheating. The LED circuit board, which is made |
| ribbon machine. Next, the inside of the bulb is | | | | from 1.6-2mm thick aluminum, will conduct the |
| coated with silica to remove the glare caused by | | | | heat from the dozen or so LED elements to the |
| a glowing, uncovered filament. The label and | | | | metal heatsink frame and thus keep |
| wattage are then stamped onto the outside top | | | | temperatures in check. Aluminum-backed PCBs |
| of each casing. | | | | are sometimes called "metal core printed circuit |
| Fourth, the base of the bulb is also constructed | | | | boards," and though made of a conductive |
| using molds. It is made with indentations in the | | | | material the white coating is electrically isolating. |
| shape of a screw so that it can easily fit into the | | | | The aluminum PCB is screwed in place within the |
| socket of a light fixture. | | | | heatsink which forms the lower half of the LED |
| Fifth, once the filament, base, and bulb are made, | | | | light bulb. |
| they are fitted together by machines. First, the | | | | After this, the power connector board is fixed in |
| filament is mounted to the stem assembly, with | | | | place with adhesive. The small power supply |
| its ends clamped to the two lead-in wires. Next, | | | | converts 120/240V AC mains power to a lower |
| the air inside the bulb is evacuated, and the casing | | | | voltage (12V or 24V), it fits in the cavity behind |
| is filled with the argon and nitrogen mixture. | | | | the aluminum PCB. |
| Finally, the base and the bulb are sealed. The base | | | | Shell assembly consists of locking the shell in place |
| slides onto the end of the glass bulb such that no | | | | with screws. A plastic shell covers the power |
| other material is needed to keep them together. | | | | supply and connects with the metal heatsink and |
| Instead, their conforming shapes allow the two | | | | LED circuit board. Ventilation holes are included to |
| pieces to be held together snugly, with the lead-in | | | | allow hot air to escape. Wiring assembly for plug |
| wires touching the aluminum base to ensure | | | | socket requires soldering wires to the bulb socket. |
| proper electrical contact. After testing, bulbs are | | | | Then shell is attached. |
| placed in their packages and shipped to | | | | Next, the completed LED light is sent to burn-in |
| consumers. | | | | testing and quality control. The burn-in test |
| Light bulbs are tested for both lamp life and | | | | typically lasts for 30 minutes. The completed LED |
| strength. In order to provide quick results, | | | | light bulb is then powered up to see if it is working |
| selected bulbs are screwed into life test racks and | | | | properly and burned in for 30 minutes. There is |
| lit at levels far exceeding normal. This provides an | | | | also a high-voltage leakage and breakdown test |
| accurate measure of how long the bulb will last | | | | and power consumption and power factor test. |
| under normal conditions. Testing is performed at | | | | Samples from the production run are tested for |
| all manufacturing plants as well as at some | | | | high-voltage leaks, power consumption, and power |
| independent testing facilities. The average life of | | | | factor (efficiency). |
| the typical household bulb is 750 to 1,000 hours, | | | | The finished bulbs pass through one final crimping |
| depending on wattage. | | | | step as the metal socket base is crimped in place, |
| LED light bulbs are built around solid-state | | | | are bar-coded and identified with lot numbers. |
| semiconductor devices, so the manufacturing | | | | External safety labels are applied and the bulb is |
| process most closely resembles that used to | | | | inked with information, such as brand and model |
| make electronic products like PC mother boards. | | | | number. Finally, all that's left is to fix on the clear |
| A light-emitting diode (LED) is a solid state | | | | plastic LED cover which is glued in place. |
| electrical circuit that generates light by the | | | | After a final check to make sure all the different |
| movement of electrons in a semiconductor | | | | parts of the LED light are tight, then it is packed |
| material. LED technology has been around since | | | | into individual boxes, and bulbs are shipped out. |
| the late 1960s, but for the first 40 years LEDs | | | | So, if you have wondered why LED light bulbs are |
| were primarily used in electronics devices to | | | | so expensive today, this explanation of how they |
| replace miniature light bulbs. Within the last decade, | | | | are manufactured and how that compares to the |
| advances in the technology finally boosted light | | | | manufacture of traditional light bulbs should help. |
| output high enough for LEDs to begin to seriously | | | | However, it also reveals why the cost will fall |
| compete with incandescent and fluorescent light | | | | pretty dramatically over the next few years. Just |
| bulbs. As with many technologies, as the cost of | | | | as the cost of manufacturing other |
| production falls each successive LED generation | | | | semiconductor-based products has fallen |
| also improves in light quality, output per watt, and | | | | dramatically due to standardization, automation |
| heat management. | | | | and other key steps along the manufacturing |
| The computer industry is well suited to | | | | learning curve, the same inexorable forces will |
| manufacture LED lighting. The process isn't a | | | | drive down the costs of LED light bulb production. |