In various LED lighting solutions, COB and CSP LED stand for the two most popular options. COB is a module-level LED circuit board that directly bonds the dies onto the aluminum PCB, copper-core PCB, or ceramic PCB. While a CSP LED is a micro SMD (surface-mount device) LED whose electrodes are directly on the chip bottom without a lead frame or metal casing. They are suitable for different applications. PCBONLINE, a one-stop LED PCB manufacturing, PCB assembly, and box-build assembly manufacturer, is here to provide a clear explanation of COB vs CSP LED.
What is COB
- Pros: Excellent heat dissipation, high light density, and good light uniformity
- Cons: Individual chips cannot be replaced or driven separately for repair
COB is chip on board, where LED chips are die-bonded directly onto a PCB (a metal or ceramic substrate), followed by bonding and encapsulation (potting) to form an integrated light source. The COB bonding methods include wire bonding and flip-chip bonding.
On the COB, dozens or even hundreds of bare chip are arranged on the LED circuit board in the round, regular hexagon, regular octagon, or square shape. This is for uniform light, balanced heat distribution, and convenient manufacturing.
According to the different arrays of the LED dies, COB LEDs are used for different applications of different power.
- Round array: Using 16-48 LED dies evenly distributed in a circle. Applied for spotlights and downlight of 5W to 50W.
- Regular hexagonal array: High-density light mixing. Applied for industrial lighting > 100W.
- Square and regular octagonal arrays: To match with rectangular reflectors or lenses. Applied for square COB modules or stage lighting chip arrays.
In the COB structure, there's no individual packaging. When all LED chips are directly bonded on the circuit board, they are encapsulated with a phosphor glue, which serves both light color conversion and protection.
What is CSP LED
- Pros: Smaller and thinner SMD device, lower thermal resistance
- Cons: High requirements for encapsulation and protection; heat dissipation is highly dependent on PCB design; slightly higher difficulty in optical design
CSP is a chip-scale package, and CSP LED means the size of the packaged LED device is nearly the same as the die. Its size ratio is ≤ 1.2:1. When the CSP LED leaves the component factory, it is an independently packaged light-emitting component.
Its bottom is covered with conductive solder pads, insulation layer, and protective layer. Electrodes are directly on the chip bottom (metal pads), allowing for direct reflow soldering onto the PCB.
Compared with other SMD LEDs (2835, 3528, and even 5050), a CSP LED is smaller and thinner, and can be mounted like 0402 or 0603 resistors. This is because the CSP LED's electrodes are directly on the chip bottom without a traditional lead frame.
Besides, CSP LEDs' thermal resistance is higher, reaching 2 to 5K/W. However, as a CSP LED is also surface-mounted on the PCB, its thermal dissipation heavily relies on the PCB, so it requires a high-thermal-conductivity PCB.
What's more, as CSP LEDs emit light from dot matrix light sources, it is easy for halos to occur. To improve light uniformity in CSP LEDs, the PCB design can:
- Use a diffuser or light guide plate to scatter light multiple times, eliminating bright spots.
- Adopt optical lens arrays to overlap and blend the light spots from various LEDs.
- Reduce LED spacing to increase the light overlap ratio, minimizing dark areas.
- Use a phosphor encapsulation layer to simulate the uniform light mixing effect of COB.
Difference between COB and CSP LED
Let's see the differences between COB and CSP LED from the following table.
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Feature
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COB LED
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CSP LED
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Structural level
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Module level - LED die directly on the PCB
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Device level - individually packaged micro-LED
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Is it an independent component?
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No, must be bonded to the PCB
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Yes, it can be surface-mounted
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Lighting emission form
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Surface light source
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Dot matrix light source
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Heat dissipation method
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Directly conducted to the PCB substrate
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Conducted to the PCB through the solder pads
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Appearance size
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One module contains multiple chips, in a round/regular hexagon/regular octagon/square shape shape
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Each CSP is a single LED, with a ratio of ≤ 1.2:1
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Packaging form
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No package / encapsulated as a whole)
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Chip-level package, with solder pads on the bottom
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Light uniformity
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Very high
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Relatively inferior
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Luminous flux density
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High
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Medium-high
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Reliability / Lifespan
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High
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Medium
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Secondary optics requirement
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Hardly required
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Necessary
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Suitable production process
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Module assembly
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SMT automated mounting
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Common applications
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COB light panels, floodlights, lighting modules
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Mini LED, cell phone backlights, automotive lights, display screens
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COB vs CSP LED: Which is Better?
Is COB inherently better than CSP LED? Both have their pros and cons, and "which one is better than" depends on the application scenario.
However, we can say that in traditional lighting and luminaire applications, such as downlights, floodlights, and track lights, COB is a better option than CSP LED in performance.
Below, you can find which is more suitable for the different applications.
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Application scenario
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Recommended LED
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Reason
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Home & commercial lighting
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COB
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Uniform light, good heat dissipation, and low cost.
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Industrial lighting/floodlights
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COB
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High-power integration
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Photography lights/stage lights
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COB
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Soft surface light source, non-glaring
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Mobile phone flashlights/automotive headlights
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CSP
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Miniaturization, high brightness, array design
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Mini LED backlights/displays
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CSP
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Micro-pitch packaging, individually addressable control
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Smart wearables/micro-light modules
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CSP
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Small package size, suitable for high-density layout
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In LED PCB design, COB and CSP LEDs also require different considerations.
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COB
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CSP LED
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Optical thinking
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Creating a single bright surface
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Creating many small bright points
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Thermal thinking
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Integrated heat conduction
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Distributed heat conduction
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Driving method
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Multiple chips share a current channel
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Each chip can be driven independently
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Process Trend
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Mature, stable
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Miniaturization, controllable development direction
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Partner with PCBONLINE for One-stop COB and CSP LED PCBs
PCBONLINE is commited to mid and high-end PCB manufacturing and assembly, including COB and CSP LED applications. We are especially good at high-power/high-current LED PCBAs because we have rich experience in thermal management and large/small current seperation.
Founded in 2005, PCBONLINE has two large advanced PCB manufacturing bases, one PCB assembly factory, stable supply chains, and an R&D team to provide you with solar light system circuit boards under one roof.
PCBONLINE has strong LED PCB manufacturing, PCB assembly, and box-build assembly capabilities, and rich technical experiences.
PCBONLINE manufactures various COB and CSP LED PCBs, including aluminum PCBs, copper-based PCBs, and ceramic PCBs.
We can indepently wire bond or flip-chip bond LED dies onto the PCB and encapsulte for COB LED PCB assembly.
In R&D, PCBONLINE excels in thermal dissipation design and electrical management, and we also take care of details in mold design, reflow/wave soldering oven temperature control, and production flow design.
We can adjust the light temperature, wavelength, and power according to your requirements.
We can provide customized SMD LED devices, including CSP LED, through our ling-term cooperation with our local component factory parters.
High-quality LED PCBA manufacturing certified with ISO 9001:2015, IATF 16949, RoHS, REACH, UL, and IPC-A-610 Class 2/3.
If you want to get R&D assistance or get a quote for your COB or CSP LED light project, PCBONLINE is pleased to receive your message and provide help and PCBA manufacturing services. Please email info@pcbonline.com to reach out to us. We will provide one-on-one engineering support throughout your project.
Conclusion
COB provide uniform light, good heat dissipation, low cost, and soft light quality. While CSP LED has a small size and precision packaging, and is suitable for high-density or controllable arrays. Contact us to order turnkey COB or CSP LED PCB assembly for any LED applications.
