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Every high-power LED module needs a heatsink. The module’s aluminum MCPCB spreads heat, but it cannot dissipate it alone — without an external heatsink, even a single 350mA LED will overheat within seconds. We carry 188 heatsinks ranging from 19mm to 100mm in square and round form factors. This guide explains how to choose the right one.
Thermal Resistance: The Key Spec
Heatsink performance is rated in °C/W (degrees Celsius per watt of heat). Lower is better — it means less temperature rise per watt.
Our range:
- Smallest (19mm Square x 10mm): 21.1 °C/W
- Largest (100mm Square x 35mm): 1.4 °C/W
A taller heatsink of the same footprint always has lower °C/W than a shorter one, because the extra height adds fin surface area. Do not choose a heatsink by physical size alone — always check the °C/W rating.
Sizing Formula
Three steps:
- Calculate power dissipation: P = Vf × I × number of LEDs
- Set your temperature budget: 40°C rise above ambient is a good target for long LED life
- Calculate required thermal resistance: R = temperature rise / P
Choose a heatsink with a °C/W rating at or below the calculated R value.
Worked Examples
| Module | Current | Vf Total | Power (W) | R Needed (40°C rise) | Minimum Heatsink |
|---|---|---|---|---|---|
| Single white Rebel Star | 350mA | 3.2V | 1.12W | 35.7 °C/W | Any — even 19mm Square (21.1) is sufficient |
| Tri-Star (3 LEDs) | 350mA | 9.6V | 3.36W | 11.9 °C/W | 30mm Square × 20mm (10.5) or larger |
| Quad (4 LEDs) | 350mA | 12.8V | 4.48W | 8.9 °C/W | 35mm Square × 20mm (9.2) or larger |
| 7-Up Round (7 LEDs) | 350mA | 22.4V | 7.84W | 5.1 °C/W | 50mm Square × 25mm (4.7) or larger |
| 7-Up Round ES | 700mA | 22.4V | 15.7W | 2.5 °C/W | 70mm Square × 30mm (2.5) or 80mm+ |
Margin matters. If your calculation says 5.1 °C/W, a heatsink rated exactly 5.1 leaves zero margin. Size up one step — the cost difference is small, the reliability improvement is significant.
Module-to-Heatsink Compatibility
The heatsink must be at least as large as the module footprint:
| Module Form Factor | Minimum Heatsink |
|---|---|
| Z 5mm, 10mm Square, Rectangular | 19mm Square |
| Star, Tri-Star, Side Emitter (20mm) | 25mm Square or 40mm Round |
| Quad (23mm) | 25mm Square or 40mm Round |
| 25mm Round/Square, Star/O | 25mm Square |
| 7-Up Round (40mm) | 40mm Round or 45mm+ Square |
Available Sizes
| Footprint | Heights Available | °C/W Range |
|---|---|---|
| 19mm Square | 10mm | 21.1 |
| 25mm Square | 10–20mm | 13.7–17.8 |
| 30mm Square | 10–20mm | 10.5–14.5 |
| 35mm Square | 10–35mm | 7.0–12.1 |
| 40mm Square | 7–10mm | 10.2–11.5 |
| 40mm Round | 25–40mm | 6.9–8.6 |
| 45mm Square | 20–25mm | 5.7–6.4 |
| 50mm Square/Round | 10–35mm | 4.5–7.6 |
| 54mm Square | 15–25mm | 4.4–5.7 |
| 60mm Square/Round | 20–35mm | 2.95–4.1 |
| 70mm Square | 20–35mm | 2.3–3.25 |
| 80mm Square | 25–30mm | 2.25–2.45 |
| 90mm Square | 20mm | 2.5 |
| 100mm Square | 20–35mm | 1.4–2.1 |
Mounting the Module to the Heatsink
Two methods:
- Thermal tape (Bergquist BOND-PLY, 9 pre-cut configurations) — Peel-and-stick. Convenient for prototyping and low-power applications. Adds a small amount of thermal resistance.
- Mechanical fastening (screws + thermal compound) — Best thermal contact. Required for high-power applications (above ~5W) where thermal tape’s added resistance becomes significant.
See Best Practices for Fastening LED Modules for detailed guidance.
