Choosing an LED technology is like choosing the right winter coat to wear: there are different models that provide more or less features depending on what you might need. Once you decide the features you want from your LED, you can easily choose the package type accordingly. The “package type” refers to the way an LED’s semiconductor die–similar to the filament in an incandescent–is packaged inside LED devices for different applications. The LED package can be very basic, like with the DIP LEDs, or it can be very versatile to handle lots of different needs, such as with the SMD package. Modern LED technology as we know it was developed in 1962 by Nick Holonyak with his invention of the DIP LED, and the LED industry has been innovating it ever since. The following article is meant to be a brief overview of the major types of LED package technology that are commercially available today.
Dual In-Line Package LED technology has been around for more than 50 years, and is likely what you think of when you picture an LED. Though it is old, DIP LEDs are far from outdated as they are still used extensively today for large signs and displays. The widespread use of DIP LEDs came about due to their long life-span and intense brightness. DIP LEDs are highly recognizable by their “pill” or “bullet” shaped design (≤5mm wide), and the long contacts that extend from the bottom of the LED which can be easily soldered or inserted into a bread board. The LED’s plastic and epoxy casing actually serves as a lens that can focus the light coming from the diode. The shape of the outer casing also includes a flat edge on one side that always indicates the cathode side of DIP LEDs.
These lights, when used for residential or home use, are typically found in electronics as indicator lights because of their low cost, high brightness, and ease of install. DIP Diodes can be bought in bulk by electronics manufacturers to fulfill many purposes; and because of their plug-and-play nature, can be easily soldered to any kind of circuit board. This gives electronic devices the ability to send information to the user without the need for an actual display on the device.
These LEDs will typically produce between 3 and 4 lumens per LED. They typically run at between 5v to 24v, with 12v being the most common voltage. They individually pull between 0.05 and 0.08 watts. This generates between 35 and 80 lumens per watt, depending on the actual LED.
The SMD chips, or "Surface Mounted Device" chips, have become very popular due to their versatility. SMD LEDs have been used to create everything from light bulbs to strip lights, and even missed call indicators on cell phones. These chips are much smaller in comparison to the DIP technology, which tends to give them the added versatility over DIP diodes. SMD technology also supports chips with more complicated designs, such as SMD 5050 chips (depicted to the left), that have RGB capabilities on a single chip. This is very powerful for color combinations, as opposed to the DIP technology, which can only display one color per device. The technology does not take the bullet shaped design from DIP LEDs, and is closer to that of a flat, square computer chip. It is also worth noting that SMD chips can have more than just two contacts (one anode and one cathode). SMD chips can have 2, 4 or 6 contacts, depending on the number of diodes on the chip. With the SMD design, there is an individual circuit for each diode. For example, SMD 5050 chips have 3 diodes on the chip, which translates to 3 circuits and a total of 6 contacts.
SMD chips have been a very important development for the LED industry because of the ability to put 3 diodes on the same chip. When a chip includes a red, green, and blue diode, you have a chip that can create any color you want by adjusting the level of output from each individual diode on the chip. Because they are very bright and can change colors, these chips are used extensively for LED strip lights and light bulbs. SMD LED chips come in a wide variety of sizes, the most common of which are SMD 3528 and SMD 5050S. SMD 3528 chips are only 3.5mm wide, and SMD 5050 chips are 5 mm wide. SMD LEDs can also be made much smaller than the 3528 and 5050 chips. Some of these chips are made very small, to go in high end electronics such as cell phones and laptop computers as indicator lights. Any cell phone you see that has a little light that stays on after the screen turns off is powered by a small SMD LED.
SMD chips that we see in light bulbs and strip lights will typically produce between 4 to 5 lumens per diode on a chip (such as a 3528, single diode chip). These chips will typically run at either 12v or 24v, with 12v being the most common. Individually these chips can pull between 0.05w to 0.08w (single diode, 3528) up to between 0.15w to .24w (three diode, 5050). This means these chips can produce between 50 and 100 lumens per watt depending on the particular chip.
The most recent LED development has been "Chip On Board" or COB technology. COB and SMD can be similar because like SMD, COB chips have multiple diodes on the same "wafer" or chip. However, this is where the similarities end. In fact, on every COB chip there are multiple diodes; typically 9 or more. The other big difference between COB and SMD technology lies in the fact that while SMD requires a circuit for every diode included on the chip, COB devices only have 1 circuit and 2 contacts for the entire chip regardless of the number of diodes. This single circuit design, regardless of the number of diodes on the chip, leads to simplicity for the rest of any COB LED device. Perhaps even more important than the simplicity aspect, COB also leads to improved lumen-per-watt ratios in comparison to other LED technologies such as DIP and SMD. Unfortunately, the big draw back from the single circuit design of COB chips stems from the fact that multiple channels are necessary to adjust individual levels of light output to create color changing effects. What this basically means is that COB technology, while very powerful and efficient in single-color applications, cannot be used to create color changing bulbs or lights.
Before COB technology, LED spot lights and flood lights were historically considered "non-standard lamps" because they required multiple LED sources to produce a high lumen output. Since the advent of COB chips in the LED arena, a large lumen count can be produced from a single source using a COB chip. This was never possible before COB, but has been a revolution for people who want to lower their energy bill but also need a standard lamp. Besides spot lights and floodlights, COB chips have been put into all kinds of bulbs and used for a number of other applications as well. In fact, COB technology is used for any small device with a flash such as a Smartphone or camera. The principle is that COB chips produces a large amount of lumens for very little energy, which is very important for any device that runs on a battery. Many Smartphones have a small 2x2 or 3x3 COB matrix to produce their camera flash. Point-and-shoot cameras similarly support a small COB chip that will use little energy and produce a large amount of light.
COB chips vary widely in their applications and thus different chips will require different wattage, voltage, and will produce vastly different lumen counts. However, it can be said of COB chips that the ratio of lumens per watt is very high, typically 80 lumens per watt minimum to well over 1oo lumen per watt.
Since the creation of COB chips, a variant has come along called MCOB or "Multiple Chip On Board". MCOB devices are very similar to COB chips in their application and are more or less just multiple COB chips together in series. MCOB devices differ from COB because they are better for low wattage situations. They also do not fulfill the standard lamp requirement for spot light and floodlights, as mentioned earlier in the COB section of this post. While MCOB devices do not meet the requirements to become a standard lamp, they produce a lot of light and are great for low wattage situations like A19 bulbs. In fact, A19 bulbs are currently the most common use of MCOB technology. If you buy an LED A19 bulb in the near future, it will likely be an MCOB bulb.
MCOB is a very new technology at this point that not many manufacturers are producing, but it will likely catch on for much more than just A19 bulbs. There are many applications for a high lumen count that MCOB can fulfill, and likely innovators will use the technology to create new products that the market has never seen before. The world of LED lighting is exciting when we see that it is changing and evolving right before our eyes. Soon we may have yet another technology that is a contender in the LED market!