Thermal Management Challenges in LED Lighting Systems

• Junction heat, accounting for 60–70% of the total heat, directly impacts the performance of the LED chip.
• The driver circuit heat contributes 20–30%, which affects electronic components.
• Optical losses, which make up around 10% are primarily absorbed by lenses and reflectors.

The light output intensity and efficiency of LEDs are highly sensitive to temperature. Studies show that while LED efficiency is around 42% at a board temperature of 30°C, it drops to 30% at 50°C and may decline to approximately 20% under typical operating temperatures of 80–100°C. For every 1°C increase in junction temperature, the rate of luminous degradation rises by about 0.5%/K. In some LEDs, when the case temperature reaches 130°C, the output may be reduced by 80% or more. Furthermore, a 10°C increase in junction temperature can potentially halve the LED's lifespan.

The Role of Thermal Interface Materials in Enhancing LED Luminance

Thermal interface materials (TIMs) improve LED luminous efficiency by establishing efficient heat conduction pathways that rapidly dissipate heat generated by the LED chip into the environment, thereby lowering the chip temperature. The underlying mechanisms can be broken down as follows:

1. Reduction of Interfacial Thermal Resistance
Multiple interfaces exist within an LED package—between the chip and substrate, substrate and heat sink, and heat sink and environment. Contact thermal resistance at these interfaces is a critical factor affecting heat dissipation efficiency. High-performance TIMs fill microscopic gaps at these interfaces, forming continuous thermal conduction channels.

2. Optimization of Thermal Management System Design
TIMs help construct low-resistance thermal pathways from the chip to the environment. Studies indicate that with appropriate TIMs and thermal management strategies, the thermal resistance of an LED chip can be reduced to as low as 0.2°C/W. For instance, an LED module using nano-silver solder exhibits a total thermal resistance of 4.82 K/W, compared to 8.75 K/W with conventional solder.

3. Direct Impact on Optical Performance
The selection and application of TIMs directly influence the optical characteristics of LEDs. Research has shown that effective thermal management significantly enhances LED light output power and spectral intensity. For example, LEDs assembled with nano-silver solder maintain superior optical performance even after aging, demonstrating that excellent heat dissipation capability contributes directly to improved luminous efficacy.