1. Why do LED Lights Need Heat Sink?

Although LEDs are highly efficient light sources, only 20%-40% of the energy consumed is converted into light, and the remaining energy is transformed into heat. This heat will radiate from the LED, but in the absence of external assistance, the rate of heat dissipation is very slow. The accumulated heat will cause the LED chip’s core temperature (junction temperature) to rise sharply. An increase in junction temperature accelerates light degradation, shortens lifespan, causes color temperature drift, and in extreme cases, can even cause the LED core to break down.

To efficiently predict the lifespan of LEDs, the Illuminating Engineering Society of North America (IESNA) has developed the LED lifespan testing method TM-21, titled “Projecting Long-Term Lumen Maintenance of LED Light Sources.” This method uses a combination of experiments and mathematical models to predict changes in luminous flux at different junction temperatures. The theoretical formula is:

f(t)=Bexp(-αt)

The prediction method is based on a mathematical model derived from actual experimental data. The process is as follows:

First, conduct experiments on the LED at three different temperatures (55°C/85°C/other temperatures) for at least 6,000 hours (recommended 10,000 hours), with luminous decay data collected every 1,000 hours. Shortening the interval (e.g., 500 hours) can improve the accuracy of the prediction.

Once the parameters are determined, the lifespan of the LED can be effectively calculated using the mathematical model. For example, when f(t) = 0.7, the corresponding time t can be calculated, which is the LED’s L70 lifespan (the time when the light output drops to 70% of the initial light output).

The following graph is drawn using TM-21.

Through past tests and calculations, the following performance comparison table for LEDs at different junction temperatures has been summarized. This clearly shows the critical role of heat dissipation for LEDs.

Junction Temperature (°C)	Luminous Output Maintenance (After 3,000 Hours)	Lifespan (L70, hours)	Color Temperature Shift (3000K LED)	Safety
25 (Ideal)	≥95%	100,000+	≤50K	Safe
85 (Recommended)	≥90%	50,000–80,000	100–200K	Safe
120 (Overheating)	60%-70%	10,000–20,000	300–500K	Risky
150 (Severe Overheating)	≤50%	≤3,000	500K+	Risk of Damage

2. Common Types of LED Heat Sinks and Their Characteristics

(1) Extrusion Heat Sink

Material Characteristics: Commonly uses 6063 aluminum alloy, density about 2.7 g/cm³, thermal conductivity ~200 W/m·K, Lightweight and corrosion-resistant.

Structure Parameters: Fin height 10–50 mm, thickness 1–3 mm. Can be designed with radial, parallel fins, or branch structures.

Thermal Conductivity: Approximately 200–210 W/m·K.

Manufacturing Cost: Moderate, with one-time mold costs and low cost for mass production.

Advantages: 1. Good thermal conductivity. 2. High strength and lightweight.

Disadvantages: 1. Extrusion limits the complexity of the shapes. 2. High initial mold investment.

(2)Die Casting Heat Sink

Material Characteristics: ADC12, A380 die-cast aluminum alloys, density about 2.7 g/cm³, thermal conductivity 90–120 W/m·K (lower than extruded aluminum).

Structure Parameters: Can form complex shapes, typically fins ≥1.5 mm thick.

Thermal Conductivity: Approximately 96–120 W/m·K.

Manufacturing Cost: High (mold costs), but suitable for large-scale production to reduce per-unit cost.

Advantages: 1. Flexible shapes, can integrate with the lamp body. 2. High strength, corrosion-resistant.

Disadvantages: 1. Lower thermal conductivity than pure aluminum. 2. High mold cost, not suitable for small-batch production.

(3)Skiving Fin Heat Sink

Material properties: Pure aluminum (such as 1060, 1070) or high-purity aluminum alloy is mostly used, with a density of approximately 2.7 g/cm³, a thermal conductivity of up to 220–240 W/m·K, high material purity, and excellent thermal conductivity.

Structural parameters: Fin height can be customized to 5–60 mm, thickness is thin, generally 0.5–2 mm, fin spacing is small and uniform, and it can be designed into straight fin, stepped and other structures, with high overall flatness.

Thermal conductivity: Approximately 220–240 W/m·K.

Manufacturing cost: Relatively high; it belongs to precision processing technology, single-piece production takes a long time, small-batch production cost is relatively high, and mass production requires process optimization to control costs.

Advantages: 1. High thermal conductivity and excellent heat dissipation efficiency. 2. Fins are thin with small spacing, resulting in a large heat dissipation area. 3. Fin height and shape can be flexibly customized according to requirements.

Disadvantages: 1. Complex processing technology and relatively low production efficiency. 2. High requirements for material purity, leading to high cost. 3. The overall structural strength is relatively low, and it is easily damaged by external forces.

(4)Heat Pipe Heat Sink

Material properties: Copper tubes contain working fluid (such as deionized water), combined with aluminum fins or copper fins.

Structural parameters: Heat pipe diameter is 6–10 mm, and multiple pipes can be connected in parallel for heat transfer.

Thermal conductivity: The equivalent thermal conductivity can reach 10000–100000 W/m·K (depending on the structure).

Manufacturing cost: Medium to high (heat pipe manufacturing + fin processing).

Advantages: 1. High efficiency in long-distance heat transfer. 2. Suitable for LED lamps with limited space or scattered heat sources.

Disadvantages: 1. Higher cost than single metal heat sinks. 2. Complex structure.

The above are the types of heat sinks that have stood the test of time and are reliable in practice. These heat sinks are all passive heat dissipation. If a more extreme heat dissipation effect is desired, fans can be added to combine active and passive heat dissipation.

3. Recommended Heat Sink Selection for Different Types of LED Lights

A good heat sink should balance cost and performance. While ensuring adequate cooling, different heat sinks can be selected based on whether cost or performance is prioritized.

LED Type and Power	Application Scene	Cost-Effective Cooling Solution	Best Performance Cooling Solution
Indoor LED (5–30W)	Home, Office	Simple extrusion heat sink(moderate cooling, low cost)	Well-structured extrusion heat sink (low cost)
Medium-Low Power Outdoor LED (30–100W)	Streetlights, Floodlights	Die casting heat sink (moderate cost)	Heat pipe fin combo
Medium-High Power Outdoor LED (100–300W)	Streetlights, Floodlights	Aluminum skiving fin heat sink (stable and durable)	Heat pipe fin combo + active cooling
High Power Industrial or Stage Lights (300W+)	Industrial or Stage Lighting	Large aluminum skiving fin heat sink + fan (increased cost)	High-efficiency heat pipe combo + forced air cooling (cheaper and stable than liquid cold plate)