High-power LED has many advantages such as energy saving and environmental protection, but at the same time, because of its high power, a large amount of heat generated cannot easily be dissipated in time and it is easy to cause the light source to decline. The overheating of the chip makes the service life greatly shortened. After power-on, about 30% of the electrical energy is converted into light energy, and the rest is converted into thermal energy. Therefore, it is a key technology to design so many thermal energy as soon as possible. Thermal energy needs to be dissipated through thermal conduction, thermal convection, and thermal radiation. Only by releasing heat as quickly as possible can the temperature of the cavity in the LED lamp be effectively reduced, the power supply can be protected from working under a persistent high-temperature environment, and the premature aging of the LED light source due to long-term high-temperature work can be avoided.
The thermal management of high-power LED lamps mainly includes three aspects: chip level, package level and system integrated heat dissipation level. Among them, the chip is the main heating component, and its quantum efficiency determines the heating efficiency, and the substrate material determines the heat transfer efficiency of the chip; for packaging, the packaging structure, materials, and processes directly affect the heat dissipation efficiency; the system integrated heat dissipation level is also called the external Radiator, mainly including heat sink, heat pipe, fan, temperature equalizing plate, etc. The main heat dissipation technologies of high-power LED lamps include heat sinks, heat pipes, temperature equalizing plates, thermally conductive double-sided adhesive, thermally conductive silicone sheets, thermally conductive silicone grease, etc.
In the design of the heat dissipation structure of high-power LED lamps, a good heat conduction path should be to reduce the thermal resistance between the PCB, the heat transfer medium, and the heat sink, and increase the effective contact surface between the three, and select a suitable heat transfer medium with a higher thermal conductivity. Speed up the efficiency of heat conduction.
The heat source of high-power LED lamps mainly comes from two parts: light source and power supply. The heat of the light source part should usually pay attention to the effective contact area between the bonding surface of the light source PCB and the heat sink. The larger the effective contact area, the better the heat dissipation. In addition, it should be noted that the thermal conduction interface between different media is as smooth as possible. The bonding between the thermal conductors should be sufficiently close, and the gap between the contact surfaces of the fittings should be as small and small as possible.
The natural convection heat dissipation method of high-power LED lamps also requires effective heat dissipation area, so in general, proper roughening of the outer wall of the heat dissipation body can increase the effective heat exchange area. In addition, when spraying different colors of paint, the spray thickness and such The thermal conductivity and heat radiation performance of the paint is good or bad. Generally, in order to increase the heat transfer area of the radiator, we use a fin structure. The effective heat exchange area is usually 50%-60% of the total area of the lamp. The "fin-type" heat sink can determine the effective heat exchange performance according to the fin efficiency and fin spacing.
In natural convection, the power supply also heats up, because the power supply of bulbs and spotlights is generally placed inside the lamp cavity, and heat dissipation treatment can be carried out by using thermally conductive potting glue or thermally conductive mud and other media. For the superposed thermal field, it may be recommended to increase the air layer between the power supply and the LED light source and the PCB bonding platform, so that it forms an air barrier to weaken the superposition effect of the thermal field.
In addition, thermal radiation is a kind of energy transfer that all objects are performing at any time, and different materials have different radiation intensities. Generally, the radiation intensity of cool-colored objects is lower than that of warm-colored objects, and the radiation intensity of rough objects is greater than that of smooth objects. In general, the radiation heat transfer of bulbs and spotlights is relatively small and can be ignored.