Due to the global energy shortage and environmental pollution, LED display has a broad application space because of its characteristics of energy saving and environmental protection. In the field of lighting, the application of LED luminous products is attracting the attention of the world. Generally speaking, the stability and quality of LED lamps are related to the heat dissipation of the lamp body itself. At present, the heat dissipation of high brightness LED lamps in the market often adopts natural heat dissipation, and the effect is not ideal. LED lamps made by LED light source are composed of LED, heat dissipation structure, driver and lens. Therefore, heat dissipation is also an important part. If LED can not heat well, its service life will also be affected.

Heat management is the main problem in the application of high brightness LED

Because the p-type doping of group III nitrides is limited by the solubility of Mg acceptors and the high starting energy of holes, heat is particularly easy to be generated in the p-type region, and this heat must be dissipated on the heat sink through the whole structure; The heat dissipation ways of LED devices are mainly heat conduction and heat convection; The extremely low thermal conductivity of sapphire substrate material leads to the increase of thermal resistance of the device, resulting in serious self heating effect, which has a devastating impact on the performance and reliability of the device.

Effect of heat on high brightness LED

The heat is concentrated in the small chip, and the chip temperature increases, resulting in the non-uniform distribution of thermal stress and the decrease of chip luminous efficiency and phosphor lasing efficiency; When the temperature exceeds a certain value, the device failure rate increases exponentially. Statistical data show that the reliability decreases by 10% every 2 ℃ rise in component temperature. When multiple LEDs are densely arranged to form a white lighting system, the problem of heat dissipation is more serious. Solving the problem of heat management has become a prerequisite for the application of high brightness LED.

Relationship between chip size and heat dissipation

The most direct way to improve the brightness of power LED display screen is to increase the input power, and in order to prevent the saturation of active layer, the size of p-n junction must be increased accordingly; Increasing the input power will inevitably increase the junction temperature and reduce the quantum efficiency. The improvement of single transistor power depends on the ability of the device to export heat from the p-n junction. Under the conditions of maintaining the existing chip material, structure, packaging process, current density on the chip and equivalent heat dissipation, increasing the chip size alone will increase the junction temperature.