In today's global energy shortage and environmental pollution, LED has a broad application space for its energy saving and environmental protection. LED luminaires consist of LED devices, heat dissipation structures, drivers, and lenses. If the LED device does not dissipate well, its lifetime will also be affected. According to the test report of the Cree XLamp XR-E, the lower the temperature of the LED device, the longer the life of the LED lamp can be extended. Therefore, addressing thermal management issues has become a key in high-brightness LED applications.
However, the amount of heat from the LED source is not the main problem affecting the LED, and the concentration of heat (and thus the formation of hot spots) is the key to the problem. For general standard LED devices, the heat flux of a 1W LED device is about 100W/cm2, and the heat flux of a 3W LED device is as high as 300W/cm2, while the heat flux of a typical CUP is 60~130W/cm2. . The heat is concentrated in a wafer having a small size, the temperature of the wafer is raised, the distribution of thermal stress is uneven, the luminous efficiency of the wafer, and the emission efficiency of the fluorescent powder are lowered. When the temperature exceeds a certain value, the device failure rate increases exponentially. When a plurality of LEDs are densely arranged to form a white light illumination system, the heat dissipation problem is more serious.
The heat dissipation path of LED devices is mainly heat conduction and heat convection. Traditionally, the heat dissipation structure of an LED luminaire includes a substrate, a heat sink, and a heat sink. The substrate conducts thermal energy from the grains and is thermally conductive but not electrically conductive. The heat sink spreads heat away from heat build-up at the LED source and increases the efficiency of the heat sink. The heat sink can be thermally and efficiently dissipated in the air. However, the extremely low thermal conductivity of the substrate material tends to cause an increase in the thermal resistance of the device, resulting in a severe self-heating effect, which has a devastating effect on the performance and reliability of the device.
Microloops' Vapor Chamber enables ultra-high heat flux heat transfer to solve hot spots in high-power LEDs. The soaking plate is a vacuum chamber with a micro-structure on the inner wall. When the heat is transmitted from the heat source to the evaporation zone, the working medium inside the cavity will begin to produce liquid phase gasification in a low-vacuum environment. At this point the medium absorbs thermal energy and the volume expands rapidly, and the medium in the gas phase quickly fills the entire cavity. When the gas phase medium contacts a relatively cold area, condensation occurs. The condensation accumulates the heat accumulated during evaporation. The condensed liquid medium returns to evaporation by the capillary phenomenon of the microstructure. Heat source. This operation will be repeated in the cavity, which is how the soaking plate works. Since the microstructure can generate capillary forces when the working fluid evaporates, the operation of the soaking plate can be prevented from being affected by gravity.
Figure 1 shows the heat dissipation structure of an LED lamp using a soaking plate that removes the substrate and reduces a large portion of the thermal resistance. The LED devices can be closely packed and directly bonded to the soaking plate, and the LED devices and related circuits are directly packaged in a standard wire-bonding machine to form an independent light source.
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