What GOB is
GOB stands for glue on board. A layer of transparent epoxy is poured over the LED array after soldering, filling the space between the lamps and covering the surface. It is not a film; it is a cured layer about 0.3 to 0.5 mm thick.
The scratch test
A key dragged across a bare module catches the top of one lamp and lifts it partly off its pad. The module still works, but that pixel is now vulnerable. On the coated module the key slides across the epoxy. There is a visible scratch in the coating; the lamp underneath is untouched.
The water test
Ten millilitres of water on the bare module sits between the lamps and starts to wick along the PCB within a minute. On the coated module it beads and stays on the surface. This is why GOB is popular for outdoor and semi-outdoor installs where cleaning involves a hose.
What it costs you
- Price: typically 8 to 15 percent more than the same module without coating.
- Repair: replacing a single lamp is harder because the epoxy has to be cut away. Some factories will replace the whole module instead.
- Appearance: a coated surface is slightly glossier and can show reflections at shallow angles.
Where it is clearly right
Outdoor signage, stadium perimeter, anything at hand height in a public space, and installations cleaned with water. The mechanical protection is real and it extends the life of a module that would otherwise take hits.
Where it is unnecessary
A high-mounted indoor wall in an office lobby, above head height, cleaned with a dry microfibre cloth. You are paying 10 percent for protection the screen will never need.
How to check whether it is really GOB
Look at the module edge. Real GOB has a continuous layer that reaches the frame and a slight meniscus at the boundary. A sprayed conformal coating looks thinner, leaves the lamp tops exposed, and often has a visible spray pattern under angled light.