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resulting in the non-uniform distribution of thermal stress and the decrease of chip luminous efficiency and fluorescent powder laser efficiency
Due to the global energy shortage and environmental pollution, LED display screen has a wide application space with its characteristics of energy saving and environmental protection, and the application of LED luminescent products in the lighting field is attracting the attention of the world.Generally speaking, whether the work of LED lamp is stable, the quality is good or not, and the lamp itself heat dissipation is crucial, the current market of high brightness LED lamp heat dissipation, often use natural heat dissipation, the effect is not ideal.LED lamp made by LED light source is composed of LED, heat dissipation structure, driver and lens. Therefore, heat dissipation is also an important part. If LED cannot heat dissipation well, its life will be affected.
Heat management is a major problem in high brightness LED applications
Because the p-type doping of group III nitride is limited by the solubility of Mg acceptor and the high start-up energy of holes, heat is particularly easy to generate in the p-type region.The main ways of heat dissipation of LED devices are heat conduction and heat convection.The extremely low thermal conductivity of the Sapphire substrate material leads to the increase of the thermal resistance of the device, resulting in a serious self-heating effect, which has a devastating impact on the performance and reliability of the device.
The effect of heat on high-brightness leds
The heat is concentrated in the chip with small size, and the temperature of chip increases, resulting in the non-uniform distribution of thermal stress and the decrease of chip luminous efficiency and fluorescent powder laser efficiency.When the temperature exceeds a certain value, the device failure rate increases exponentially.Statistics show that reliability decreases by 10% for every 2℃ increase in element temperature.The heat dissipation problem is worse when multiple leds are arranged in a dense array to form a white-light lighting system.Heat management has become a prerequisite for high brightness LED applications.
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 active layer saturation must correspondingly increase the size of the p-n junction;Increasing the input power will inevitably raise the temperature of the junction, thus reducing the quantum efficiency.The improvement of single-tube power depends on the device's ability to export heat from the p-n junction. If the chip size is increased separately, the junction temperature will continue to rise under the condition that the existing chip material, structure, packaging technology, on-chip current density is kept unchanged and the same heat dissipation conditions are maintained.