Understanding CoB LEDs | Lumileds

What are CoB LEDs?

LUXEON CoB Finder

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A CoB LED (or chip-on-board LED) is a single device with many LED chips mounted on a thermally efficient substrate placed below a uniform phosphor coating.

Anyone who walks through a store or home with recessed or track lighting likely experiences light from a chip-on-board LED (CoB). CoBs are widely used because they emit a bright white light output from a compact light source and are very efficient in a broad range of applications.

So what is a CoB LED, and how is it different from other types of LEDs?

CoB (chip-on-board) refers to the way in which the LED unit is constructed. The basic elements of white CoB LEDs are:

• An electrical power supply to provide the energy to drive the LED
• The light-emitting chip or ‘die’. This is sometimes referred to as the blue light pump, and is made of a semiconductor material, indium gallium nitride (InGaN), which emits blue photons when energized
• A phosphor coating which converts the blue light to white. The chemical composition of the phosphor is controlled to produce light of a specific color temperature

CoB LED: Space-Saving Array of Multiple LED Chips

A CoB LED is a single device with many LED chips mounted on a thermally efficient substrate, or board. Each chip is a bare die – that is, the chip does not have its own leadframe, phosphor coating or lens. This means that the chips can be mounted extremely closely together on the substrate. The close placement of the LED chips allows for high intensity or light density to be emitted from a smaller area than is possible with single packaged LEDs. The CoB LED manufacturer then applies a uniform phosphor coating to the entire array of chips to convert the blue light to the required white color temperature.

Advantages of a CoB LED

A single CoB LED can contain hundreds of chips forming a dense array. This dense array enables a CoB LED to produce more light output from a smaller area than is generally possible with an array of packaged LEDs.

Using a single LED can result in simpler design and product as well as providing optical advantages for uniform light and efficient optics.

Electrical design is simpler because the CoB LED only requires a single two-wire power supply to the entire array of chips. The positive and negative terminals on a CoB LED are clearly visible in the picture of LUXEON CoB Core Range products above. By contrast, an array of packaged LEDs requires dedicated power supply traces to be routed on the PCB to each LED unit.

Production is simpler because the number of units to be soldered to the board will be lower if a CoB LED is used instead of an array of packaged LEDs.

Optically, a broad range of optics, usually reflectors, can be used with CoBs of different sizes to determine the direction and width of the beam such as with a spot or flood lamp.

Finally, a CoB LED’s color is potentially more consistent because a single phosphor coating is applied to the entire array of chips, whereas in an array of packaged LEDs, each LED unit has its own phosphor coating.

An example of CoB LEDs of various sizes is shown below.

CoB LEDs from Lumileds

COB (Chip-on-Board) LEDs are increasingly popular due to their efficiency, compact size, and superior lighting quality. However, selecting the right COB LEDs can be challenging, especially if you're unfamiliar with the key factors to consider. In this guide, we’ll highlight the eight most common mistakes to avoid when choosing COB LEDs, ensuring you make an informed decision for your lighting needs.

1. Ignoring the Lumen Output

The lumen output is a critical measure of the brightness of an LED. It's essential to match the lumen output with your lighting requirements. Choosing COB LEDs with inadequate lumen output can result in insufficient illumination, while excessively high lumens can lead to unnecessary energy consumption and glare.

2. Overlooking Color Temperature

Color temperature, measured in Kelvin (K), affects the ambiance and functionality of the lighting. Lower color temperatures (K-K) provide a warm, cozy light, ideal for residential settings. Higher color temperatures (K-K) emit a cooler, more vibrant light, suitable for commercial and industrial spaces. Selecting the wrong color temperature can impact the atmosphere and usability of the space.

Tunable White COB LED 20W -K

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3. Disregarding Beam Angle

The beam angle determines the spread of light from the LED. A narrow beam angle (15°-30°) is perfect for focused lighting applications, such as spotlights or task lighting. A wider beam angle (60°-120°) is better for general illumination. Not considering the beam angle can lead to uneven lighting and shadowed areas.

4. Not Considering Heat Dissipation

Heat dissipation is crucial for the longevity and performance of COB LEDs. Poor heat management can lead to reduced efficiency and a shorter lifespan. Ensure that the COB LEDs you choose have adequate heat sinks or cooling mechanisms to manage heat effectively.

5. Ignoring the CRI (Color Rendering Index)

CRI measures the ability of a light source to reveal the true colors of objects. COB LEDs with a high CRI (80 and above) provide more accurate color representation, essential for applications like retail, photography, and medical environments. Overlooking CRI can result in lighting that distorts colors and affects the visual experience.

6. Failing to Check Power Requirements

Different COB LEDs have varying power requirements. Ensure that your power supply matches the voltage and current requirements of the LEDs. Using an incompatible power supply can lead to poor performance, flickering, or even damage to the LEDs.

7. Overlooking the Importance of Drivers

LED drivers regulate the power supply to the LEDs, ensuring consistent performance and protecting against power fluctuations. Selecting COB LEDs without considering the quality and compatibility of the drivers can lead to reliability issues and shortened LED lifespan.

8. Neglecting Manufacturer Reputation and Reviews

Not all COB LEDs are created equal. Manufacturer reputation and customer reviews provide valuable insights into the quality and reliability of the products. Opt for reputable manufacturers with positive reviews to ensure you're getting high-quality COB LEDs that meet your expectations.

FAQs About Choosing COB LEDs

Q: What is the lifespan of COB LEDs?

A: COB LEDs typically have a lifespan of 30,000 to 50,000 hours, depending on usage and heat management. Proper installation and adequate cooling can maximize their lifespan.

Q: Can COB LEDs be dimmed?

A: Yes, many COB LEDs are dimmable. However, you need to ensure that the LED driver and dimmer switch are compatible with dimming functions.

Q: Are COB LEDs energy-efficient?

A: COB LEDs are highly energy-efficient, providing more lumens per watt compared to traditional lighting sources. They are an excellent choice for reducing energy consumption and lowering utility bills.

Q: How do I choose the right beam angle for my application?

A: Consider the purpose of the lighting. For accent or task lighting, a narrow beam angle is ideal. For general illumination, a wider beam angle is preferable to ensure even light distribution.

Q: Do COB LEDs require special fixtures?

A: COB LEDs can be used with a variety of fixtures. However, it's important to ensure that the fixtures are designed to manage heat dissipation effectively to maintain the performance and longevity of the LEDs.

By avoiding these common mistakes and considering the key factors highlighted in this guide, you can select the right COB LEDs for your needs, ensuring optimal performance, energy efficiency, and longevity. Make informed choices and enjoy the benefits of superior lighting with COB LEDs.