Proper thermal management- extracting excess heat from a lighting system- is required to create a reliable and efficient design. If heat is not removed from the system effectively, the LED will overheat causing changes to the key characteristics of the light:

• The color of the LED can shift in response to an increase in temperature
• The brightness of the LED can vary due to changes in current caused by temperature variations
• The reliability of the LED depends on the die temperature- higher temperatures decrease reliability
• The materials used to encapsulate the LED can change in response to temperature and become less transparent

Heat can also impact other portions of the lighting system and lead to additional problems:

• Heat can change the optical transmission properties of the lens and reduce efficiency
• The driver circuit can also be effected by heat, reducing efficiency, reliability and current stability further impacting the LED’s lighting characteristics
• The mechanical connections in the system will be stressed due to expansion and contraction as temperature varies. This can lead to mechanical interconnect failures impacting system efficiency and reliability.

The better the thermal management design is at removing heat from the system, the more stable the light quality from the LED and optical sub-systems will be. The more heat extracted from the system, the harder the LEDs can be driven; resulting in more light output and possibly a reduction in the number of LEDs needed to achieve the desired level of light output. The overall effects of a good thermal solution lead to a lower cost and more reliable system.

Each part of the design can contribute to a high-quality, cost effective thermal solution. OSRAM Opto Semiconductor’s LEDs have a higher thermal resistance (specified by TJC) allowing more heat to remain in the system; reducing the complexity of the thermal solution without reducing system reliability. Many of our LED driver partners base their solutions on highly efficient switching regulator technology to increase efficiency and reduce heat generation while also using thermally conductive packages to help with heat extraction.