COB and SOB LED Strip Technology

Overview

What are COB and SOB LED strips?

COB (Chip-on-Board) and SOB (SMD-on-Board) flexible LED strips are both designed to remove the visible "dots" of conventional LED tape, giving a smooth, seamless, unbroken line of light. Instead of a row of separate bright points, the whole surface of the strip glows evenly, so it can be seen directly or reflected in gloss surfaces without hotspots.

They reach that dot-free look in different ways. A COB strip bonds hundreds of tiny, unpackaged LED chips directly onto a slim flexible printed circuit (FPC) under one continuous layer of phosphor. An SOB strip solders closely packed, pre-binned mini-SMD LEDs onto a heavier copper board under a continuous diffusing silicone coat, giving a clean white look when off, tight colour consistency between reels and higher power over longer runs.

Our PF5000 series COB and SOB strips are available from 420 to 576 LEDs/m on 4, 8 and 10mm wide FPC, in 12V and 24V versions, with colour temperatures from 1800K to 6500K, CRI 80, 90 or 95, and in both fixed and tuneable white CCT. For high-output applications the 20mm wide Ultra High Intensity COB Flexistrip packs 3072 LEDs/m.

Continuous, dot-free light without needing a deep diffuser
Wide, even beam with no hotspots or striping on reflective surfaces
Colour temperatures from 1800K to 6500K, plus tuneable white
High colour rendering options: CRI 80, 90 and 95
Short cut intervals for accurate fitting to length

COB & SOB range at a glance

Technology: COB and SOB
LED density: 420 – 924 LEDs/m
Strip width: 4, 8, 10 and 20mm
Voltage: 12V and 24V
CCT: 1800K – 6500K, tuneable
CRI: 80, 90, 95
Power: 5W/m – 30W/m
Reel length: 5 metres

COB Selector Guide Technical Enquiry

The technology

How COB and SOB create a dot-free line

On a conventional SMD strip, each LED is a separate packaged component with its own phosphor, spaced several millimetres apart. Close up, or when reflected in a gloss surface, each one shows as a distinct bright spot, so SMD strip normally needs a deep profile and diffuser to blend the light.

On a COB (Chip-on-Board) strip, bare blue LED dies with no individual housing are bonded straight onto the FPC at very high density, then blanketed under a single continuous line of phosphor-loaded silicone. The phosphor converts the blue light to white along its whole length, so light leaves the strip as one continuous surface rather than individual points.

An SOB (SMD-on-Board) strip reaches the same dot-free result a different way. Ultra-small packaged mini-SMD LEDs, each with its own phosphor, are soldered closely together on the board, then covered with a thick, continuous layer of light-diffusing silicone. In effect it is a very high-density SMD strip under a seamless diffuser.

Simplified side view: flexible PCB (grey), LED chips (navy), phosphor and emitted light (gold).

Benefits

Advantages of COB and SOB LED strips

Why designers choose COB and SOB strip where the light itself is on show.

Dot-free appearance

A continuous phosphor surface gives an even line of light, even when the strip is directly visible or reflected in gloss worktops, glass or polished floors.

Fits shallow profiles

No need for a deep channel to blend individual LEDs, so COB suits slim aluminium profiles, shelf edges, coves and tight furniture recesses.

Wide, even beam

Light is emitted over a wide angle from the whole surface, giving soft, glare-free illumination and smooth wall washes without scalloping.

High colour quality

CRI 80, 90 and 95 options and colour temperatures from 1800K to 6500K, with tuneable white COB and SOB strip for adjustable colour temperature.

Short cut intervals

High chip density means cut points are closer together than on most SMD strip, so runs can be trimmed accurately to the space available.

Flexible and robust

Thin FPC bends easily around curves, and with no separate LED packages to knock off, COB strip is tolerant of handling during installation.

COB vs SOB

Same seamless look, different engineering

COB and SOB both remove the visible dots of standard SMD strip, but the way they are built affects appearance when switched off, colour matching, power and run length.

Characteristic	Standard SMD strip	COB strip	SOB strip
Light source	Packaged SMD LEDs, spaced apart	Bare blue LED dies bonded to the board	Packaged mini-SMD LEDs, closely spaced
Phosphor / cover	Phosphor in each LED package	One continuous phosphor-silicone layer	Phosphor in each LED, under a continuous diffusing silicone layer
Lit appearance	Individual dots	Dot-free	Dot-free
Unlit appearance	Visible LEDs	Solid yellow phosphor line	Clean white or frosted finish
Colour consistency	Good, binned LEDs	Can vary slightly between production batches	Very consistent, pre-binned LEDs for close reel-to-reel matching
Board & power	Wide range	Thin, very flexible FPC; standard widths suit low to medium power	Heavier copper FPC; suits higher power per metre
Run length	Depends on voltage and power	Best for shorter single-feed runs	Longer single-feed runs with less voltage drop
Thermal	Heat spread across separate LEDs	Heat concentrated in a narrow line; mount on aluminium profile	Heavier copper tracks help spread heat
Tuneable white	Available	Available	Available

Choose COB if…

You need a slim, highly flexible strip for tight furniture accents, under-cabinet lighting or short runs
The strip will be hidden in a profile when switched off
You want a dot-free line of light at a cost-effective price
You need very high output from a wide-format strip, such as our 20mm 3072 LEDs/m Flexistrip

Choose SOB if…

The strip is on view when switched off, such as exposed on a wall or ceiling, and a yellow line would look out of place
You are lighting a large or multi-room project and need close colour matching across reels, including extensions ordered later
You need higher power and brightness over longer runs with fewer power feeds

What else to consider

Standard SMD strip is still a cost-effective choice where the strip is hidden and the light is bounced or diffused. When specifying COB or SOB, also consider density (higher gives a smoother line and more output), power per metre (match to your profile's heat dissipation), voltage (24V allows longer runs with less voltage drop) and CRI (90+ for retail, hospitality and display lighting).

Ask an Engineer

3072

Max LEDs per metre

CRI 95

Highest colour rendering

1800–6500K

Colour temperature range

15.5mm

Shortest cut interval

Where COB strips excel

COB and SOB strips are used wherever a clean, continuous line of light is part of the design.

Architectural coves

Ceiling coves, wall grazing and recessed lines where the strip or its reflection is on view.

Retail & display

Shelf edges, display cabinets and showcases where high CRI brings out true product colour.

Kitchens & furniture

Under-cabinet and plinth lighting over gloss surfaces that would otherwise show every LED dot.

Hospitality

Bar fronts, back-bar shelving and signage edges with warm, even accent lighting.

Luminaire OEMs

Linear light engines for slim luminaires, mirrors and backlit panels in shallow housings.

High-output lighting

Wide-format, high-density COB strip for task and general lighting where lumen output matters.

FAQ

COB LED strip questions

SMD strip uses individually packaged LEDs spaced along the circuit, which can show as visible dots of light. COB (Chip-on-Board) strip mounts hundreds of tiny LED chips directly onto the flexible PCB and covers them with a continuous phosphor layer, giving a smooth, dot-free line of light without a diffuser.

SOB strip solders ultra-small packaged mini-SMD LEDs, each with its own phosphor, closely together on the board and covers them with a thick, continuous layer of diffusing silicone, so the line appears dot-free like COB. Because the LEDs are pre-binned it gives very consistent colour between reels, and its heavier copper board suits higher power and longer runs.

The continuous phosphor layer that turns the blue LED chips' light into white is yellow in colour, so an unlit COB strip shows as a solid yellow line. If the strip will be on view when off, SOB strip, with its white or frosted silicone finish, or a profile with an opal diffuser, gives a cleaner look.

For large or multi-room projects SOB is usually the better choice. Its pre-binned LEDs give close colour matching across multiple reels, including extensions ordered later, and its heavier copper board allows longer runs with fewer power feeds. COB is ideal for slim, flexible installations and shorter runs.

COB strip is dot-free without a diffuser, so it works well in shallow channels and coves. An aluminium profile is still recommended at higher power ratings to help dissipate heat and protect the strip, and an opal cover can soften glare further.

24V strip carries half the current of 12V for the same power, so voltage drop is lower and longer runs can be fed from one end with consistent brightness. 12V is useful for shorter runs or where a 12V supply is already available.

Yes. COB strips can be cut at the marked cut points, which are much closer together than on most SMD strips. For example, our 20mm wide 3072 LEDs/m Flexistrip can be cut every 15.5mm.

COB and SOB LED Strip Technology