Study on the influences of the substrate parameters for thermal spreading resistance of light emitting diode

The life of light emitting diode (LED) has a great relationship with its thermal resistance. As a part of the total thermal resistance, thermal spreading resistance may also affect the reliability of LED. To study the influence of LED packaging substrate for thermal spreading resistance, this article analyzes the influence of different parameters for thermal spreading resistance of single heat source. Results show that the thermal conductivity, the thickness of substrate and the heat source area has great influence on thermal spreading resistance. But the convection coefficient is not so important. And the more the heat source deviates from the center of substrate, the greater the thermal spreading resistance will be. Secondly, based on LED devices with direct bond copper ceramics (DBC) substrate, thermal spreading resistance with two heat transfer layers are analyzed by analytical solution and simulation. The influences of different thickness of copper and ceramics for thermal spreading resistance and total thermal resistance are analyzed. Results show that with the increase of the thickness of copper and ceramics, the thermal spreading resistance and the total thermal resistance are decrease, and the effect of copper is more apparent. So the reasonable design of packaging substrate for LED packaging can reduce the thermal resistance and improve the performance of LED heat dissipation.