A COB LED is a light-emitting device in which multiple bare LED dies are mounted closely together on a shared substrate and electrically connected as one compact light source. COB stands for chip on board. Instead of packaging every LED die inside a separate housing, the manufacturer integrates the dies into a single array with a common light-emitting surface.
COB is therefore a type of LED packaging technology—not an alternative to LED. Its main value is that it combines many small emitters into one concentrated source that can be paired with a reflector, lens, holder, driver, thermal interface, and heat sink. Lumileds describes the same core architecture as multiple LED chips mounted on a thermally efficient substrate beneath a uniform coating.
How Does a COB LED Work?
Every LED die contains a semiconductor junction that emits light when forward current flows through it. In a COB LED, multiple dies are attached directly to a shared substrate, interconnected in a defined series-parallel circuit, and protected by an encapsulant. The substrate supports the dies electrically and creates a thermal path from the junctions toward the cooling system.
A typical COB LED light source includes:
- multiple bare LED dies;
- a ceramic, metal, or application-specific substrate;
- die-attach material and electrical interconnections;
- positive and negative terminals or multiple channel contacts;
- an encapsulant, phosphor layer, or protective optical material;
- a defined light-emitting surface, commonly called the LES;
- mounting features that connect the COB to a holder or heat sink.
In a white COB LED, blue-emitting dies are commonly covered by a phosphor material that converts part of the blue light into a broader spectrum perceived as white. The phosphor formulation and die combination influence correlated color temperature (CCT), color rendering, chromaticity, and spectral distribution.
Colored and specialty-spectrum COB LEDs can use different die wavelengths, phosphor systems, or multiple channels. This allows one compact source to be designed around red, blue, far-red, near-infrared, ultraviolet, tunable-white, or multi-wavelength requirements, depending on the application and device architecture.
What Does “Chip on Board” Mean?
“Chip on board” describes the packaging method. The word chip refers to the bare semiconductor die. The word board refers to the shared substrate on which those dies are mounted and interconnected.
This distinction is important for product designers. A COB LED is more than a group of loose chips placed on a finished lamp PCB. It is an integrated light-source component with a defined circuit, emitting area, thermal path, mechanical outline, and set of operating conditions. The completed COB is then connected to a driver and installed in the larger lighting or equipment assembly.
Closely spaced dies make the individual light points appear as one source when viewed through the encapsulant and optical system. The result is a concentrated emitting area that can simplify beam formation compared with an array of separately packaged LEDs.
What Is the LES of a COB LED?
The light-emitting surface (LES) is the active area from which the COB produces light. It is one of the most important COB selection parameters because it directly affects optical design.
A smaller LES can create higher luminance and support tighter beam control when matched with the right reflector or lens. A larger LES can support greater total output or a broader source geometry, but it requires a correspondingly designed optic. Two COB LEDs with similar power ratings may behave very differently if their LES dimensions, flux density, beam geometry, and thermal characteristics are different.
When replacing one COB with another, compare the LES diameter or dimensions together with the substrate outline, mounting pattern, electrical position, optical center, and holder compatibility.
COB LED vs SMD LED: What Is the Difference?
Both COB and SMD are LED packaging methods. The difference lies in how the dies are packaged and how the light source is integrated into the system.
An SMD LED normally contains one or several dies inside an individual surface-mount package. The packaged LEDs are then placed on a PCB using SMT assembly. A COB LED integrates multiple bare dies into one larger package-level light source before it is installed in the final assembly.
| Design factor | COB LED | SMD LED array |
|---|---|---|
| Basic structure | Multiple bare dies on one shared substrate | Multiple individually packaged LEDs mounted on a PCB |
| Emitting geometry | One concentrated LES | Separate light points distributed across the board |
| Optical approach | Often paired with one reflector or lens system | Can use individual, grouped, or board-level optics |
| Circuit flexibility | Circuit is largely defined inside the COB; multi-channel versions require dedicated contacts | LED count, spacing, and circuit routing can be arranged on the application PCB |
| Thermal design | Heat is concentrated beneath one high-output source | Heat can be distributed across a larger board area |
| Assembly | COB, holder, thermal interface, heat sink, driver, and optic form one system | SMT placement and reflow are commonly used for the LED array |
| Typical design advantage | Compact high-output source and simplified optical alignment | Flexible emitter placement, channel layout, service, and form factor |
Choose COB when the product needs a compact, optically concentrated source. Choose SMD when distributed light points, flexible PCB geometry, independent channels, or scalable board-level layouts are more important. Many products also combine the two approaches in different subsystems.
LEIENDA supplies both COB integrated light sources and SMD LED package families for projects with different optical, electrical, and mechanical requirements.
Is a COB LED the Same as a COB Strip or COB Display?
No. These products share a chip-on-board principle, but they serve different markets and use different structures.
COB LED Light Source
A COB LED light source is a localized emitter designed to work with a driver, thermal system, and optic. It is commonly used in spotlights, downlights, stage lighting, equipment light sources, and other products that need a compact emitting area.
COB LED Strip
A COB LED strip mounts many small dies along a flexible circuit and covers them with a continuous encapsulant or phosphor layer. Its purpose is to create a linear, dot-free lighting effect. Strip voltage, cut length, flexible-circuit construction, and installation profile are central selection factors.
COB LED Display
A COB LED display mounts dense red, green, and blue dies onto a display board to form pixels. Pixel pitch, contrast, protection, and display resolution drive this design. It is a display-packaging application rather than a COB lighting emitter.
For B2B sourcing, use the complete product name—such as COB LED light source, COB LED strip, or COB LED display—so suppliers evaluate the correct architecture.
What Are the Main Advantages of COB LEDs?
Compact High-Output Source
Closely packed dies allow a COB LED to deliver substantial output from a relatively small emitting area. This can reduce the space required for the light source and support compact luminaires or equipment.
More Uniform Source Geometry
Because the dies share one emitting area, a COB can produce a visually continuous source after phosphor, encapsulation, and optical mixing. This helps reduce the multiple-shadow effect that can occur when separate high-power emitters are spaced apart.
Simplified Optical Integration
A single LES provides one optical reference point. Designers can align a reflector, lens, mixing chamber, or light guide around that source instead of controlling many separate focal points.
Fewer Board-Level Light-Source Components
One COB can replace an array of individually packaged LEDs in suitable designs. This can simplify component placement and board routing, although the complete product still needs the correct driver, protection, holder, connector, thermal interface, and heat sink.
Flexible Spectral Architecture
The shared substrate can accommodate different die types and circuit arrangements. This makes COB useful for custom white-light spectra, multi-wavelength combinations, specialty colors, red and near-infrared sources, and independently controlled channels when the package is designed for them.
What Are the Limitations of COB LEDs?
Heat Is Concentrated in One Area
The compact light source also creates concentrated heat. Electrical power that is not converted into optical output must travel from the LED junctions through the substrate, thermal interface, and heat sink. A complete thermal design therefore considers drive current, ambient temperature, thermal resistance, case temperature, junction-temperature limit, interface material, heat-sink capacity, and airflow.
The COB datasheet and application brief should guide the mounting and temperature-measurement method. For example, Lumileds’ COB application guidance uses a defined case-temperature point when evaluating junction temperature in the assembled system.
The Internal Circuit Offers Less Board-Level Freedom
The series-parallel arrangement is built into the COB. The system driver must match its forward voltage, current, power, and channel configuration. An SMD array gives the PCB designer more freedom to change emitter count and routing, while a COB provides a more integrated circuit.
Optics and Mechanics Are Closely Linked
LES position, substrate dimensions, mounting holes, holder geometry, and reflector alignment work together. A mechanically similar replacement may still change the beam if its LES or optical center differs.
Service Usually Occurs at the Source Level
Individual dies inside a COB are not normally field-replaceable. Product service is planned around replacing the COB, holder assembly, or complete light engine rather than repairing one die.
Handling Requires Process Control
The emitting surface, encapsulant, electrical pads, and substrate can be damaged by contamination, mechanical pressure, electrostatic discharge, or incorrect mounting. Assembly instructions should define storage, handling, thermal-interface application, fastening, soldering or connector use, and cleaning compatibility.
What Types of COB LEDs Are Available?
COB products are commonly organized by optical goal and system architecture rather than by one package number.
| COB type | Main design goal | Key selection factors |
|---|---|---|
| White-light COB | General, architectural, retail, studio, or task lighting | CCT, CRI, chromaticity, luminous flux, efficacy, LES, voltage, current, and thermal resistance |
| High-density or small-LES COB | Concentrated output and tighter beam control | LES, luminance, center-beam intensity, optic compatibility, heat flux, and case temperature |
| Tunable-white COB | Adjustable CCT or dim-to-warm behavior | Channel circuit, CCT range, color path, driver compatibility, and mixing uniformity |
| Color or specialty-spectrum COB | Monochromatic, UV, IR, horticultural, inspection, or equipment light sources | Peak wavelength, FWHM, radiant output, spectral distribution, channel ratio, and safety requirements |
| Multi-channel COB | Independent control of multiple colors or wavelengths | Number of channels, pad layout, current per channel, control method, and thermal balance |
| Custom COB module | Application-specific dimensions, spectrum, power, or interface | Mechanical drawing, target output, circuit, substrate, LES, optics, operating environment, and production requirements |
These categories can overlap. A horticultural COB may also be multi-channel, while a studio-lighting COB may combine high density with tunable white. Start with the application’s optical result, then define the electrical, thermal, and mechanical architecture.
Where Are COB LEDs Used?
COB LEDs are selected when a product benefits from a compact, concentrated, and optically unified light source. Common application groups include:
- spotlights, track lights, downlights, and accent lighting;
- stage, studio, photography, and entertainment lighting;
- flashlights, searchlights, and portable high-output equipment;
- horticultural and research lighting;
- machine-vision, inspection, sensing, and specialty illumination;
- UV curing and other wavelength-specific industrial systems;
- red, far-red, and near-infrared equipment light sources;
- custom optical instruments and LED light engines.
The application name is only the starting point. The design team still matches the spectrum or color quality, LES, output, beam, drive conditions, duty cycle, cooling, safety controls, and mechanical interface to the complete product.
How Do You Choose a COB LED for a B2B Project?
A productive COB LED RFQ describes the required light and the system around it. Include the following information:
- Application and optical target: State what the light source must illuminate, detect, activate, or display. Include beam geometry, working distance, illuminated area, and target output.
- Spectrum or color quality: For white light, define CCT, CRI, chromaticity tolerance, and any R9 or TM-30 requirement. For colored, UV, or IR sources, define peak wavelength, tolerance, FWHM, radiant output, and spectral shape.
- LES and mechanical envelope: Provide the preferred LES, maximum substrate size, thickness, mounting-hole pattern, optical center, connector or pad location, and available heat-sink space.
- Electrical architecture: State forward-voltage range, operating current, rated power, dimming method, driver type, and single- or multi-channel requirements.
- Thermal conditions: Include ambient temperature, duty cycle, case-temperature target, heat-sink arrangement, airflow, thermal-interface material, and available derating strategy.
- Optics and holder: Identify the reflector, lens, holder, mixing chamber, or light guide already selected—or provide the required beam so the source and optic can be evaluated together.
- Reliability and handling: Define operating hours, switching or pulsing behavior, environmental exposure, ESD controls, storage conditions, and required qualification data.
- Commercial project details: Add the project stage, sample quantity, forecast volume, timeline, target market, and documentation needed for product integration.
These inputs allow the supplier to evaluate the COB, driver, thermal path, optic, and mechanical assembly as one light-source system.
How LEIENDA Supports COB LED Development
Founded in 2011 and based in Shiyan, Bao’an, Shenzhen, LEIENDA develops and manufactures high-power SMD LEDs, COB light sources, and application-specific LED assemblies.
LEIENDA’s COB development includes specialty-spectrum and multi-wavelength directions such as red/blue, far-red, and red/near-infrared light sources. For projects that need a purpose-built source, the engineering discussion can cover wavelength, spectrum, power, voltage, color, dimensions, board structure, multi-wavelength combinations, and multi-channel configurations.
Some equipment projects need more than a standalone COB emitter. LEIENDA can also discuss the relationship between the LED package, PCB or FPC light board, and integrated module through its LED light-board and module solutions.
Frequently Asked Questions
Is COB LED better than LED?
COB is a type of LED packaging, so the more useful comparison is COB versus SMD, DIP, or another light-source architecture. COB is a strong choice for a compact, concentrated emitting area. SMD is often better for distributed emitters, flexible board layouts, and independently arranged channels.
Does a COB LED need a driver?
Yes. A COB LED requires a compatible current-controlled driver. Select the driver around the COB’s forward-voltage range, operating current, power, dimming method, and number of channels.
Does a COB LED need a heat sink?
High-output COB LEDs generally operate as part of a designed thermal system that includes a thermal interface and heat sink. Size the cooling system from the electrical load, thermal resistance, ambient conditions, case-temperature target, and junction-temperature limit.
What is the difference between COB wattage and light output?
Wattage describes electrical input, while light output describes the resulting luminous flux or radiant flux. Two COBs at the same wattage can produce different output because of die technology, spectrum, temperature, drive conditions, phosphor, and optical design.
Can a COB LED produce multiple wavelengths?
Yes. A COB can integrate different die wavelengths or channels on one substrate. The package design defines the wavelength combination, electrical circuit, channel control, optical mixing, and thermal balance.
Can a COB LED be replaced with another COB of the same wattage?
Wattage alone is not enough for substitution. Compare the forward voltage, current, LES, substrate dimensions, mounting pattern, optical center, spectrum or CCT, output, thermal resistance, case-temperature limit, and holder or optic compatibility.
Discuss Your COB LED Requirements
If your project needs a compact white-light source, a specialty wavelength combination, or a custom COB LED module, send LEIENDA the application, target spectrum or CCT, optical output, power and electrical conditions, LES and board dimensions, thermal environment, channel requirements, sample quantity, and forecast volume.
Submit your drawings and operating requirements through the LEIENDA contact page to start a COB LED evaluation.
