An Analysis of the Deadly Problem of High Brightness LED Life
October 23, 2017
1.Thermal management is the main problem in high brightness LED applications
Since the p-type doping of the group III nitride is limited by the solubility of the Mg acceptor and the higher starting energies of the holes, the heat is particularly susceptible to the p-type region, which must pass through the entire structure to dissipate on the heat sink; LED devices are mainly heat conduction and thermal convection; Sapphire substrate material very low thermal conductivity led to increased device thermal resistance, resulting in a serious self-heating effect on the device performance and reliability of a devastating impact.
2.The impact of heat on high brightness LED
The heat concentration is concentrated in the chip with very small size, the chip temperature is increased, the non-uniform distribution of thermal stress is caused, the chip hair rate and the lasers lance efficiency decrease. When the temperature exceeds a certain value, the device failure rate increases exponentially. Statistics show that the temperature for each rise 2 ℃, reliability decreased by 10%. When multiple LEDs are arranged to form a white light system, the heat dissipation problem is more serious. Solving heat management issues has become a prerequisite for high brightness LED applications.
3.The relationship between chip size and heat dissipation
The most straightforward way to improve the LED is to increase the input power, and in order to prevent the saturation of the active layer must be increased accordingly p-n junction size; increase the input power is bound to increase the junction temperature, thereby reducing the quantum efficiency. The increase in single-tube power depends on the ability of the device to derive heat from the pn junction. The size of the chip is increased by maintaining the current chip material, structure, packaging process, constant current density on the chip, and equivalent cooling conditions. The temperature will continue to rise.