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Role Of Junction Temperature In LED Lighting

December 30, 2022

LED lights, a fixture in LED beacons, police car lights, fire trucks, EMT vehicles, traffic arrows and more, is one of the most advanced lighting technologies in the market today. It is also a common fact that they emit very little heat during operation. However, this is only the case externally. The actual heat emitted by an LED light can be judged by something known as junction temperature. Its importance in heat dissipation will be addressed in this blog.


What is the junction temperature in an LED?


Before defining junction temperature, it’s necessary to understand LED die and substrate. The die is responsible for emitting light when current passes through it. The substrate is the material on which the die is mounted, typically made of aluminum or ceramic. 
The junction temperature is the temperature at the meeting point of the die and substrate. It is one of the highest temperatures within the LED, hence it is a perfect measure of the actual heat dissipation of the device. 


Importance of junction temperature

Junction temperature is an important factor in LED lighting because it determines how efficiently the LED can convert electrical energy into light. The lower the junction temperature, the more efficient the LED will be. Junction temperature is affected by a number of factors, including the type of materials used to make the LED, the design of the LED, and how well it is cooled.


Effects of poor LED heat dissipation

There are two noticeable effects of high junction temperature/poor heat dissipation:

- When the LED emits light at higher temperatures and with warmer colours, such as red or amber, its output or brightness will be drastically affected. 

- It will reduce the lifespan of the LED, due to prolonged exposure to high temperatures.


Therefore, a quality LED will have lower junction temperatures, which can be achieved by creating a conductive path for the heat to flow away from the junction point using a heatsink.


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