COB strip — chip-on-board, where the diodes are bonded directly to the board and covered by a continuous phosphor layer — has moved from a novelty to the default choice for a lot of architectural work. It solves a real problem completely. It also costs more and brings its own constraints, and both sides deserve a straight answer before you specify it.
What is actually different
A conventional SMD strip has discrete packages — 2835, 5050, 2216 — soldered at intervals along the tape. Each package is a bright point, and the gaps between them are what you see as dots. A COB strip bonds many small dies directly to the board and covers the whole run with a continuous layer of phosphor. There is no gap and no visible emitter, so the strip reads as one unbroken line of light.
What you gain
- Genuinely dot-free at any distance — no need for opal diffusers or deep profiles to blend emitters
- Shallower profiles — because the light source is already diffuse, the strip can sit closer to the diffuser, which allows slimmer and cheaper channel
- Higher packing density — the same footprint can carry more dies, so lumens per metre is often higher
- Better on reflective surfaces — polished stone, glass and stainless show every dot; they do not show COB
- Uniform colour — no batching visible between adjacent packages
For a specifier working on reception desks, mirror surrounds, cove lighting and any close-view surface, COB removes an entire category of complaint. Our 24 V COB strip and the RGB 768-LED COB are both aimed at that use case.
What you pay for it
| Trade-off | Detail | Mitigation |
|---|---|---|
| Unit cost | Typically 30–60 % more per metre than SMD | Use COB only where the dot-free look is visible |
| Heat concentration | Dies are close together, so heat per square mm is higher | Aluminium profile is not optional above ~10 W/m |
| Repairability | One failed die spoils a segment; no field rework | Keep spare short lengths; design with cut points accessible |
| Efficiency ceiling | Phosphor layer absorbs some output; lm/W can trail the best SMD | Compare lm/W, not just lm/m |
| Dimming linearity | Some drivers dim COB non-linearly at the bottom end | Test the driver pair at 1–5 % before specifying |
Why the heat point matters more than the datasheet suggests
Because COB packs emitters tightly, the thermal load per unit area is higher than SMD at the same wattage. Two strips both rated 12 W/m are not thermally equivalent if one is COB. Run COB at full power in an enclosed void without a heatsink and the output will drop measurably within the first year, while the strip still “works” — which makes it a warranty argument rather than a failure you can photograph.
The practical rule: above about 10 W/m, COB goes in an aluminium channel, not on adhesive. Our profiles are sized for exactly this, including the shallow models that COB makes possible in the first place.
When SMD is still the better buy
- Long runs where the light is hidden from view — the dot pattern is invisible, so you are paying for nothing
- High-output requirements where the absolute best lm/W matters more than uniformity
- Tight budget projects where the strip sits more than about 100 mm behind a diffuser
- Applications needing field repairability, such as temporary sets and touring equipment
Specification notes that actually differ
Most of a COB spec reads like any other strip — voltage, W/m, CRI, IP, CCT — but four items need asking:
- Die count and arrangement — affects both density and how the strip behaves when cut
- Phosphor uniformity — ask whether colour is binned along the length, not just batch
- Bend tolerance — COB tolerates less bending than SMD; check the minimum radius for the profile you are using
- Cut increment — often coarser than SMD, which matters for exact-length installations
Decision checklist
- Is the light source visible, or within about 100 mm of a diffuser? If not, COB may be unnecessary
- What is the surface behind the strip? Reflective surfaces push you toward COB
- Is there a heatsink? Above 10 W/m, COB needs one
- What is the cut increment versus the required lengths?
- Does the driver dim COB cleanly at the low end?
- Compare lm/W between the COB and SMD options, not just lm/m
We supply COB and SMD strip side by side, so we can tell you which one a given installation actually needs — including when the cheaper option performs identically in service. Send the mounting detail and the viewing distance and we will do that comparison for your project.