As LED display technology advances toward high definition, high reliability and diversified packaging, SMD (Surface Mount Device), COB (Chip on Board) and GOB (Glue on Board) have become the three mainstream packaging technologies for LED modules in the market. Each technology features distinct structural design, packaging processes and technical parameters, and is tailored to different application scenarios and market demands. This report presents a professional, objective technical comparison of the three module types from the perspectives of packaging structure, core processes, optical performance and physical characteristics, focusing on factual technical parameter output without comparative evaluation of advantages and disadvantages.
1. Packaging Structure and Core Manufacturing Processes
SMD LED Modules
SMD modules adopt the surface mount technology, with independent SMD LED lamp beads (typically SMD2121, SMD3528, SMD1515) welded on the PCB (Printed Circuit Board) surface in a matrix arrangement. The core process includes lamp bead die bonding, wire bonding, encapsulation of a single lamp bead with silica gel, and subsequent surface mounting and reflow soldering on the PCB board. Each lamp bead is an independent light-emitting unit, with a visible gap between adjacent lamp beads on the module surface; the circuit board and welding points are partially exposed, with no overall encapsulation structure on the module surface.
COB LED Modules
COB modules integrate multiple bare LED chips directly on a single ceramic or aluminum substrate for die bonding and wire bonding, without manufacturing independent lamp beads. The core process involves arranging RGB bare chips on the substrate according to a fixed pixel pitch, connecting the circuit through wire bonding, and then encapsulating the entire chip array area with a layer of fluorescent powder and silica gel to form an integrated light-emitting module. The light-emitting area is a whole encapsulation block, with no independent lamp bead structure; the substrate and non-light-emitting areas remain exposed, and the module surface is partially encapsulated.
GOB LED Modules
GOB modules are based on the PCB board of traditional SMD or COB modules (mainstream with SMD as the base) and add an overall encapsulation process. The core process includes first completing the production of the SMD/COB light-emitting module, then covering the entire surface of the module (including light-emitting units, circuit lines and welding points) with a high-transparency, high-hardness epoxy resin or organic silica gel through vacuum pouring and curing. The encapsulation layer forms a seamless, integrated protective structure on the module surface, completely covering all internal components with no exposed circuit or chip parts.
2. Optical Performance and Basic Technical Parameters
Pixel Arrangement and Pitch Range
SMD Modules: Pixel arrangement is based on independent lamp beads, with a clear lattice distribution; the mainstream pixel pitch ranges from P1.25mm to P5mm for indoor use, and P6mm to P20mm for outdoor use, with a relatively wide adjustable range of pitch.
COB Modules: Pixels are formed by integrated chip arrays, with a dense and continuous light-emitting surface; the pixel pitch is mainly concentrated in the small-pitch range of P0.6mm to P2.5mm, suitable for ultra-high-definition indoor display scenarios.
GOB Modules: Based on the pixel arrangement of the base module (SMD/COB), the overall encapsulation does not change the original pixel pitch; the applicable pitch range is consistent with the base module, covering both small-pitch (P0.6mm-P2.5mm) and medium-pitch (P2.5mm-P5mm) indoor scenarios.
Basic Optical Indexes
SMD Modules: Color gamut coverage is 90%-95% of NTSC, color consistency ΔE≤2, horizontal/vertical viewing angle of 120°-160°, refresh rate of 1920Hz-3840Hz; the light-emitting effect is discrete, with slight lattice sense on the display surface.
COB Modules: Color gamut coverage is 95%-98% of NTSC, color consistency ΔE≤1.5, horizontal/vertical viewing angle of 140°-170°, refresh rate of 3840Hz-4800Hz; the integrated light-emitting surface reduces the lattice sense, with a more continuous display effect.
GOB Modules: The optical indexes are consistent with the base SMD/COB module, with color gamut coverage of 90%-98% of NTSC, color consistency ΔE≤1.5-2, horizontal/vertical viewing angle of 120°-170°, refresh rate of 1920Hz-4800Hz; the high-transparency encapsulation layer has no obvious attenuation of light transmittance, and the original optical performance of the base module is fully retained.
3. Physical Characteristics and Structural Performance
Thickness and Weight
SMD Modules: The thickness of the mainstream indoor module is 10mm-15mm, and the weight of the 320×160mm standard module is about 300g-350g; the structure is relatively light and thin, with no additional encapsulation layer weight.
COB Modules: The substrate is mostly ceramic/aluminum material, with a module thickness of 8mm-12mm, and the weight of the 320×160mm standard module is about 350g-400g; the integrated encapsulation block increases the partial weight of the light-emitting area.
GOB Modules: Based on the base module, the encapsulation layer adds a thickness of 0.5mm-1mm, with an overall module thickness of 10.5mm-16mm, and the weight of the 320×160mm standard module is about 320g-380g; the weight and thickness have a slight increase compared with the original base module.
Sealing and Protection Level
SMD Modules: No overall encapsulation, with exposed lamp beads and welding points; the protection level is IP20 for the whole machine, and only the single lamp bead has a small range of waterproof and dustproof performance, which is sensitive to dust and moisture.
COB Modules: Partial encapsulation of the light-emitting area, with exposed substrate and circuit edges; the protection level of the light-emitting surface is IP30-IP40, with a certain dustproof performance, and the non-encapsulated area is still easy to accumulate dust.
GOB Modules: Full-surface seamless encapsulation, with all internal components isolated from the outside; the protection level of the module surface can reach IP65-IP67, which is resistant to dust, moisture, and slight liquid splashing, and the internal structure is not affected by the external environment.
Mechanical Performance
SMD Modules: The lamp beads and welding points are the weak parts of the structure, with low impact resistance and easy falling off or damage when subjected to external collision and extrusion; the PCB board has a certain bending performance, and the module is not easy to deform under normal storage conditions.
COB Modules: The integrated light-emitting block has high structural strength, and the chip area is resistant to slight impact; the ceramic/aluminum substrate has high hardness and poor bending performance, and is easy to crack when subjected to external force bending.
GOB Modules: The overall encapsulation layer forms a rigid protective structure on the surface, which effectively enhances the impact resistance and pressure resistance of the lamp beads/welding points; the encapsulation glue has a certain toughness, and the module can maintain structural integrity under slight external force extrusion, without affecting the internal components.
4. Process Compatibility and Application Matching
Substrate and Material Compatibility
SMD Modules: Compatible with FR4, aluminum and other mainstream PCB substrates, and can be matched with different types of SMD lamp beads according to demand; the manufacturing process is mature, and the production line has strong universality.
COB Modules: Mainly compatible with ceramic and high thermal conductivity aluminum substrates, and the bare chip model needs to be matched with the substrate circuit design; the process is highly customized, and the production line is dedicated to COB packaging.
GOB Modules: Based on the existing SMD/COB module production line, an additional overall encapsulation production line is added, with strong compatibility with the original substrate and material of the base module; the encapsulation glue can be customized according to the application scenario (high hardness/ high toughness).
Scenario Application Matching
SMD Modules: Matched with general indoor medium-pitch display scenarios, such as ordinary commercial digital signage, office lobby displays, and small and medium-sized event backdrops, which require mature processes and moderate cost control.
COB Modules: Matched with indoor ultra-small-pitch ultra-high-definition display scenarios, such as command and dispatch centers, high-end conference rooms, and museum fine display, which focus on high definition and continuous light-emitting effect.
GOB Modules: Matched with indoor complex environment display scenarios, such as high-flow transportation hubs, shopping mall hall displays, and semi-outdoor covered display areas, which have requirements for protection performance and structural stability on the basis of ensuring display effect.
5. Maintenance Characteristics and Process Norms
Maintenance Mode
SMD Modules: Adopt the lamp bead replacement mode, and the damaged single lamp bead can be welded and replaced independently; the module can be repaired on site, with simple maintenance tools and low professional requirements for maintenance personnel.
COB Modules: The light-emitting area is an integrated encapsulation block, and the damaged chip area cannot be replaced independently; the whole module needs to be disassembled and replaced for maintenance, with no on-site repair conditions, and the maintenance needs to be completed in a professional workshop.
GOB Modules: Based on the base module's maintenance logic, if the base is an SMD module, the lamp bead replacement can be completed after removing the surface encapsulation layer; if the base is a COB module, the whole module needs to be replaced; the maintenance process adds the encapsulation layer removal/re-encapsulation step, with higher professional requirements for maintenance personnel.
Maintenance Process Norms
SMD Modules: The maintenance process follows the general SMD welding process, with clear operation norms and universal maintenance accessories.
COB Modules: The maintenance needs to follow the COB module disassembly and assembly process, and the replacement module needs to be re-calibrated for color and brightness to ensure consistency with the original screen.
GOB Modules: The maintenance needs to follow the special process of encapsulation layer treatment, and the re-encapsulation after maintenance needs to be completed under vacuum conditions to avoid air bubbles and ensure the flatness of the encapsulation layer.
Post time: Mar-18-2026
