LED Strip Heat: Profiles, Derating and Adhesive
Why a sealed aluminium profile halves LED strip life, how to calculate junction temperature, when to derate, and why adhesive tape fails above 40 °C.
HFY Applications Engineering · Published November 6, 2026 · 3 min read
LED strip life is set by junction temperature, and a strip in a sealed profile runs 15–20 °C hotter than the same strip in free air. At 12 W/m in a 15 mm sealed profile the surface reaches 70–75 °C, which roughly halves time to L70. Derating to 70% current or specifying a ventilated profile recovers most of the lost life.
Key points
- Every 10 °C above 85 °C junction temperature roughly halves time to L70.
- A sealed profile is the single largest cause of premature strip failure — and it is a design decision, not a defect.
- Adhesive tape is rated to about 40 °C; above that, mechanical clips are the only reliable fixing.
- Derating to 70% current costs 30% of flux and roughly doubles life.
Where the heat goes
An LED converts 30–45% of its input to light and the rest to heat. At 12 W/m, that is roughly 7 W of heat per metre that must leave through the FPC, the adhesive and whatever the strip is mounted on.
| Mounting | Typical surface temperature at 12 W/m, 25 °C ambient | Relative life |
|---|---|---|
| Bare strip in free air | 45–50 °C | Baseline |
| 15 mm sealed aluminium profile | 70–75 °C | ~50% |
| 20 mm ventilated profile | 55–60 °C | ~85% |
| Extruded into silicone neon (no substrate) | 60–65 °C | ~70% |
| On a steel beam, adhesive only | 65–70 °C | ~60% |
The number that matters is not the profile size but whether air can move past it. A large profile with a closed diffuser and no vents performs worse than a small ventilated one.
The calculation, in one line
For a first estimate:
Tj ≈ T_surface + 1 °C per LED of power at 0.025 WAt 480 chips/m and 12 W/m, that is about 1 °C. The dominant term is the surface temperature, which is why measuring it with an infrared thermometer beats any calculation.
Three fixes that work
- Ventilate the profile. A 2 mm slot at each end and a diffuser that does not seal removes 10–15 °C. This is free and almost never done.
- Reduce wattage per metre. 8 W/m of high-efficacy strip often delivers the same illuminance as 14 W/m of a cheaper strip, at 60% of the heat. The relevant property is lm/W, not W/m.
- Derate the current. Running at 70% typically doubles time to L70 and costs about 30% of flux. For a 10-year installation this is usually the right trade.
Adhesive: the quiet failure
3M 300LSE and Tesa 4965 are the tapes used on good strip. Both are pressure-sensitive acrylics with a service range to about 90 °C, but their shear strength falls sharply above 40 °C — the tape does not melt, it creeps. On a warm ceiling, a 600 g/m strip creeps off the surface over a season.
Rules:
- Clean with isopropyl alcohol, not a household cleaner, and let it flash off.
- Apply 2 kg of pressure per 25 mm with a roller; hand pressure is not enough.
- Above 40 °C surface temperature or on a ceiling, use aluminium clips or a profile.
- Never rely on adhesive on a dusty or textured surface — plasterboard and brick need mechanical fixing.
What this means for a specification
A “50,000-hour” strip in a sealed profile is a 25,000-hour installation. If the maintenance access is difficult, specify L80 at the calculated temperature and derate, and put the driver where someone can reach it. The relationship between temperature and rated life is covered in LED strip lifetime, and the practical sealing trade-offs that also affect heat are in IP ratings.
For high-output runs, the COB LED strip page states the power per metre for each density so the heat load can be calculated before the profile is chosen.
This article describes general manufacturing practice for machined and fabricated components. It is not a substitute for a drawing-specific engineering review — tolerances, material selection and process capability depend on the individual part.