- SMD module: A packaged LED soldered to the board with an exposed joint and bracket
- GOB module: A finished SMD face flooded with a clear potting compound
- COB module: Multiple bare dies bonded to the substrate under one encapsulant
- Cabinet fit: Both ship in standard cabinets and use the same signal chain
- Common cabinet sizes: 500 x 500 mm and 500 x 1000 mm front-service panels
Two starting points, one goal
Both constructions exist because a bare SMD face has a weak point. Discrete LEDs stand on solder joints, and those joints are what fail when a module is knocked, wiped hard, or left in humid air for years. Each approach shields that face, and they start from opposite ends of the line.
GOB, glue on board, is a secondary process. The module is built as a normal SMD module, tested, cleaned, then flooded with a transparent potting compound that cures into a continuous layer over the diodes and the board. COB, chip on board, is a primary process: the die are attached and wire-bonded directly to the substrate, then covered by a single encapsulant, so there is no packaged LED, no bracket and no exposed pad to protect.
What the surface layer changes in service
On a GOB module the potting layer shields the diode bodies and the joints beneath them, which is exactly where impact and moisture attack begin. That makes the face tolerant of handling, of cleaning and of the small knocks of transport and rigging.
The potting edge is also where the limit shows. Compound meets the module frame at a boundary, and that seam decides long-term moisture resistance. On a COB module the encapsulant is part of the package, not poured over it, so the surface is continuous across the board. That continuity helps where dust settles and has to be wiped, and it removes the crevice a potting edge creates.
Heat and the layer in the way
Heat leaves an LED through the board, so anything between the die and the board matters. COB shortens that path: the chip sits on the substrate and the encapsulant is thin, which keeps thermal resistance low and suits walls that run continuously. GOB keeps the packaged LED in place, and its potting layer sits above the package, adding a thin insulating film over a path that was already indirect.
In ordinary indoor duty the difference is small. In a wall that runs all day, or in a cabinet with limited airflow, it becomes a real design input. If a GOB build is proposed for continuous operation, ask how the thermal design accounts for the potting layer, and ask what brightness the cabinet is rated for when the room runs warm instead of at a comfortable temperature.
Repair, spares and one dead pixel
A GOB module keeps the electrical structure of SMD, so a single failed diode can be reached by opening the potting locally, replacing the part and re-sealing the area. The work is slower than on a bare SMD module and needs a technician who has done it, but it can happen on site with the module in place.
A COB module is repaired at board level, which usually means returning it to a workshop with die-rework equipment. In exchange, the surface tolerates handling that would destroy an SMD face. The trade is a slower local repair against a faster module swap, and the right choice follows from how fast the wall must return to full image and how far the site sits from support.
What the face looks like under light
An SMD face is a grid of point sources, and the visible structure between the LEDs is part of how the image reads up close. Potting a GOB module softens that structure by diffusing light slightly at the surface, which reduces emitter harshness without changing the grid beneath.
COB produces a continuous emitting surface, so the gaps between pixels disappear and the image reads as one plane. That tends to cut glare at shallow angles and looks calmer on camera, which is why broadcast and control-room walls lean that way. The smoothness can also make high-contrast content look flatter, and whether that is an improvement is a judgement about the content, not a property of the technology.
Choose by site condition, not by label
Neither construction is the higher grade. High-touch locations, rental stock that travels, humid interiors and dusty halls punish the module face, and a potted face answers that directly. Rooms that run continuously, where close viewing and image calm matter, and where the wall is never touched point the other way.
Put the site conditions in front of the supplier and ask for the construction that follows from them, with the reasoning written down. Also ask what the warranty covers on the face, how a repair is carried out in practice, and what spares are held. Those three answers separate a construction choice from a marketing label.
| Criterion | GOB | COB |
|---|---|---|
| Face protection | Potted layer over SMD | Continuous encapsulant over bare die |
| Thermal path | Indirect (package + potting) | Short (die on substrate) |
| On-site repair | Local open-and-reseal possible | Module swap; board rework off site |
| Surface look | Diffused point grid | Continuous plane, lower glare |
| Best for | High-touch, travel, humidity | Continuous duty, camera, close view |
Two processes, one goal
GOB floods a finished SMD face with clear adhesive; COB bonds bare chips under the substrate with one encapsulant layer. GOB adds armour to a mature design; COB removes the package that needed the armour.
Different thermal paths
COB shortens the chip-to-substrate path, suiting continuous walls. GOB keeps the package and adds a glue film on top, so ask how the cabinet sheds heat when room temperature runs high.
Surface and look
GOB softens the dot matrix; COB reads as a continuous plane with lower grazing-angle glare, which is why broadcast and control-room walls lean COB.
Putting this into practice: gob vs cob led modules
- List what the field will punish Note impact, moisture, dust, heat, and touch frequency. Surface protection must answer the dominant failure mode.
- Decide the duty cycle Intermittent use is fine for either; continuous running leans toward COB's shorter thermal path, so review the GOB cabinet's thermal design instead of assuming.
- Confirm the service path GOB can be locally re-encapsulated; COB is usually whole-module swap with board-level repair off site. Match to how fast the wall must recover.
- Ask for surface warranty and a sample Ask for warranty wording on the surface, not just the module, and view a sample in your real ambient light before a large order.
- Put the conditions to the supplier Require a structure choice based on the site with the reasoning in writing, plus spares and service practice.
Misconceptions about gob vs cob led modules
“GOB loses brightness through the glue.” — The glue is specified for transmission. It changes the thermal path and surface look, both worth confirming on a sample.
“COB is always the premium choice.” — Neither is superior. High touch frequency, transport, and moisture lean toward an encapsulated face; continuous running and close viewing lean COB.
“COB is field-repairable.” — Chip-level repair needs workshop equipment; the on-site action is a whole-module swap, so spares become part of the purchase.
Verification points for gob vs cob led modules
- List the failure modes the site actually punishes: impact, moisture, dust, heat, touch
- Decide the duty cycle: intermittent use favours either; all-day running favours the shorter thermal path
- Confirm the repair route and spare holding for the construction you choose
- Ask for the warranty wording on the face, not just the module
- Request a sample under your real ambient light before committing a large order
What to carry forward on gob vs cob led modules
GOB protects a finished SMD module with a poured layer; COB removes the packaged LED and seals bare chips under a continuous surface. GOB favours impact and moisture resistance with local repair; COB favours heat path, surface continuity and image calm with workshop repair. Choose from what the site will do to the face, then confirm the repair route and the spares before the order.