The light-emitting diode of an LED package radiates light and heat according to the input power. However, the surface area of an LED package is quite small,and the package itself is expected to release little heat into the atmosphere.An external radiator such as a heat sink is thus required.The heat dissipation structure up to the connection portion of the external radiator uses mainly heat conduction.
This document provides technical data regarding the heat dissipation structure of the CL-L270 Series light-emitting diodes. It explains that due to the small surface area of the LED package, an external radiator such as a heat sink is required for efficient heat release.
The datasheet details the internal package structure and thermal resistance values, specifically noting a junction-to-case thermal resistance (Rj-s) of 78 °C/W. It also provides guidelines for thermal design outside the package, including formulas to calculate allowable external thermal resistance based on ambient temperature and driving current to ensure the junction temperature does not exceed the absolute maximum rating of 120°C.
| Junction-to-case thermal resistance (Rj-s) | 78 °C/W |
|---|---|
| Absolute maximum junction temperature (Tj) | 120°C |
An external radiator such as a heat sink is required because the surface area of the LED package is quite small and it cannot release much heat into the atmosphere on its own.
The junction temperature is calculated using the formula Tj = Rj-s * Pd + Ts, where Rj-s is thermal resistance, Pd is input power, and Ts is soldering temperature.