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LED The basics of Chip-on-Board (COB) LEDs

| Author / Editor: Luke James / Erika Granath

The Chip-on-Board (COB) LED is one of the latest and most advanced entrants to the LED market, but what is it that makes these LEDs much brighter, consume less power, and output a higher quality beam than the older LED technologies?

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Chip-on-Board or "COB" refers to the mounting of a bare LED chip in direct contact with a substrate (such as silicon carbide or sapphire) to produce LED arrays.
Chip-on-Board or "COB" refers to the mounting of a bare LED chip in direct contact with a substrate (such as silicon carbide or sapphire) to produce LED arrays.
(Source: SUMBULBS)

LED technology is constantly being improved to improve performance, create more use cases, and make it more versatile. Now more than ever, LED is a more popular light source to traditional incandescent lights, primarily because they can last a lot longer—up to 25 times longer—and use less energy.

LED lights come in a variety of different models and types, such as the surface-mounted device (SMD) type or the chip-on-board (COB) type.

What is a COB LED?

COB refers to the mounting of an LED chip directly in contact with a substrate, such as silicon carbide (SiC) or sapphire, to produce LED arrays. COB LEDs are a newer and more advanced entrant to the market, and they have a number of notable advantages over older LED technologies.

COB technology exhibits a much higher lumen density, for example. This is achieved through the use of several diodes—often nine or more—whereas older LED iterations commonly use only one (DIP LEDs) or three (SMD LEDs). Utilising more diodes in an LED means that there will be a higher and more uniform light intensity whilst footprint is simultaneously reduced. COB technology also makes use of a single circuit design with two contacts regardless of how many diodes are on the chip, making LEDs far simpler.

Other advantages of COB LEDs include:

  • A highly compact, small size design;
  • Greater intensity, particularly at close distances;
  • High uniformity even when at close working distances;
  • A simpler single circuit design; and Superior thermal performance for increased stability and reliability.

How COB LEDs differ from SMD LEDs?

Comparision of LED array packing density (10mm X 10mm)
Comparision of LED array packing density (10mm X 10mm)
(Source: Lightspot)

The mounted surface device (SMD) LED is the most common type of LED available on the market. This type of LED is permanently fused to a printed circuit board (PCB) and is highly popular due to its versatility. Light bulbs, string lights, mobile phone torches, and video game controllers are just a few examples of where SMD Les can be found.

One of the SMD LED’s most distinct features is the number of contacts and diodes it uses—it can have more than two contacts and up to three diodes on a single chip, each with its own circuit with its own anode and cathode. This can lead up to two, four, or six contacts in a chip.

It is this configuration that makes SMDs more versatile (especially when compared to COBs). The SMD LED can include a red, green, and blue diode, and these can be used to create virtually any color on the spectrum by adjusting the output level. In contrast, COB LEDs cannot be used to create color-changing bulbs. This is because of the single circuit design that uses only two contacts; to create the color changing effect, multiple channels are required.

Whilst their inability to change colour means that COB LEDs have fewer applications than SMD LEDs, they are more useful where ultra-bright LED light is needed, such as in phone torches, ultra-bright handheld rechargeable torches, and car headlights and light strips.

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