The Myth About LED Heat: Where It Really Goes

THE MISCONCEPTION

There’s a common belief that LED lighting “doesn’t get hot.” After all, you can touch the front of a lit LED panel or strip and feel no warmth. Compared to halogen or incandescent bulbs, which can burn your fingers, LEDs seem almost magical — efficient, cool, and effortless.

But here’s the truth: LEDs absolutely generate heat. They just manage it differently. The difference lies not in the absence of heat, but in where that heat goes and how it’s dissipated.

UNDERSTANDING HOW LEDS PRODUCE LIGHT

To understand why LEDs behave differently, we need to look at how they produce light.
An LED (Light Emitting Diode) is a semiconductor device. When an electrical current passes through the diode, electrons recombine with holes in the semiconductor material, releasing energy in the form of photons — visible light.

However, not all of that electrical energy is converted into light. Even the most efficient LEDs on the market achieve around 40–60% electrical-to-optical conversion efficiency. The remaining energy is converted into heat within the LED junction — the microscopic point where light is generated.

Unlike older technologies, LEDs do not emit infrared radiation (which we perceive as radiant heat) from the front of the lens. Instead, heat builds up inside the semiconductor and must move out through conduction, traveling into the printed circuit board (PCB) or aluminium substrate that supports the LED.

WHERE THE HEAT ACTUALLY GOES

Because of their design, LEDs emit almost no forward heat — which is why they’re safe to touch on the surface. But inside, thermal energy is constantly being produced and must be removed through a defined thermal pathway.

1. Junction to Board (Conduction): Heat begins at the LED junction and moves into the metal core printed circuit board (MCPCB) or aluminium backing.
2. Board to Housing (Conduction): The MCPCB is bonded to a thermally conductive frame or extrusion, usually aluminium, which spreads and dissipates the heat over a larger surface area.
3. Housing to Air (Convection): The heat is then transferred from the housing or frame into the surrounding air.

This thermal chain — junction, board, housing, air — determines the LED’s performance, efficiency, and lifespan. Poor design at any point in this chain can cause the LED to overheat, leading to reduced light output, colour shift, or early failure.

WHY THERMAL MANAGEMENT MATTERS

LED chips are sensitive to temperature. The key measurement is junction temperature (Tj) — the temperature at the LED’s core. If the junction temperature exceeds the manufacturer’s limit (often around 85°C for most standard LEDs), performance and longevity drop dramatically.

High junction temperatures can cause:

• Reduced luminous efficacy: The LED produces less light per watt of power.
• Colour shift: White LEDs can drift towards yellow or blue.
• Accelerated degradation: The phosphor layer and encapsulant materials age faster.
• Shortened lifespan: A 10°C increase in junction temperature can halve an LED’s operational life.

Good thermal management ensures the heat has a clear, low-resistance path to escape. That’s why quality LED fixtures are built with extruded aluminium housings, integrated heat sinks, and high-grade thermal adhesives or pads — all designed to move heat away efficiently.

THE ROLE OF ALUMINIUM FRAMES AND MOUNTING SURFACES

Architectural and display lighting systems often use LEDs mounted directly onto aluminium profiles, frames, or tension system extrusions. In these applications, the aluminium serves a dual purpose — both structural and thermal.

Aluminium is an excellent conductor of heat (with a thermal conductivity of around 205 W/m·K), allowing it to spread thermal energy quickly and evenly. This prevents localised hotspots and helps maintain a uniform temperature across the lighting system.

When LEDs are bonded correctly to aluminium profiles using thermally conductive adhesive or direct mechanical contact, the entire frame becomes part of the passive cooling system. This is particularly important in enclosed environments such as backlit lightboxes or architectural luminaires, where airflow is limited.

COMMON DESIGN MISTAKES

Many lower-cost or poorly designed LED products fail not because of cheap diodes, but because of inadequate thermal design. Common issues include:

• Insufficient heat sinking or ventilation.
• Use of plastic housings with poor thermal conductivity.
• Inadequate bonding between LED board and frame.
• Lack of airflow in sealed enclosures.
• Overdriven LEDs with no current regulation.

These flaws trap heat at the junction, leading to premature dimming, colour drift, or total failure — all avoidable with proper engineering.

THE BOTTOM LINE: LEDS DON’T ELIMINATE HEAT — THEY RELOCATE IT

So, the next time you hear someone say “LEDs don’t get hot,” remember this: they do — just not where you expect.

While the front lens remains cool and touch-safe, the real heat is travelling through the back of the LED into the circuit board, frame, and ultimately the air around it. Managing that heat is what separates a reliable lighting system from a short-lived one.

In short, LEDs don’t eliminate heat; they relocate it. The performance, stability, and longevity of your lighting depend entirely on the quality of the materials, the design of the housing, and the thermal management built into the system.

Good LED lighting isn’t just about brightness — it’s about controlling what you can’t see: the flow of heat behind the light.