Some people say that HEAT is the number one enemy of LEDs. Theoretically, the electro-optical conversion efficiency of the LED is about 54% (the estimated result under ideal conditions), but any omissions in the manufacturing process and any defects in the material will cause its energy conversion efficiency to drop. Based on the current level of LED technology development, the electro-optical conversion efficiency is basically less than half of the theoretical value, and in practical applications, most of them are even less than 1/4 of the theoretical value, and the remaining electric energy will be released in the form of heat energy. , This is the reason why the LED generates heat.
Among all the solutions, the heat-conducting plastics with the characteristics of uniform heat dissipation and light weight are prepared into the heat-dissipating parts of the LED: such as lamp holders, cooling and heat-dissipating lamp cups and shells, which are currently one of the most respected methods. Compared with metal materials, thermally conductive plastics consume less energy and produce less pollution in production, are more environmentally friendly, and have the characteristics of high safety factor and flexible design. With the improvement of LED light efficiency and the reduction of heat generation, the requirements for LED heat dissipation will gradually decrease, and thermally conductive plastic heat sinks will be able to meet the heat dissipation requirements of most conventional LED lamps.
Most polymer materials themselves are thermally insulating materials. To obtain materials with excellent thermal conductivity, one is to make polymer materials with high thermal conductivity; the other is to fill and modify the polymer through blending methods to form composite materials to improve Thermal conductivity of polymers.
For plastic manufacturers, the former is more technically difficult and costly, while the latter is easier to implement. According to statistics, the thermal conductivity of general plastics is only about 0.2 W/(m·K). If the plastic is filled with thermally conductive fillers, the thermal conductivity can be 1W/(m·K)～20 W/(m·K) About 5-100 times the thermal conductivity of traditional plastics.
The matrix of thermally conductive plastic is PA6/PA66, PPS, TPE, PC, PE, PP, etc.; thermally conductive fillers can be divided into two categories: thermally conductive inorganic insulating fillers and thermally conductive non-insulating fillers. Thermally conductive inorganic insulating fillers include Al2O3, BN, AlN, MgO, etc. These fillers can ensure the thermal conductivity of the composite material and maintain the electrical insulation of the resulting products, so they have been widely used. Non-insulating thermally conductive plastic fillers include metal powder, graphite, carbon black, carbon fiber, etc., which have high electrical and thermal conductivity. The former is mixed with the plastic matrix to make a thermally conductive insulating plastic, and the latter is a thermally conductive non-insulating plastic.
For filled thermally conductive polymer materials, if the filler has high thermal conductivity and good electrical insulation, the thermal conductivity of the composite material depends on the molecular chain vibration of the polymer matrix and the interaction of lattice phonons and filler lattice phonons. ; If the filler has electrical conductivity, the heat conduction in the composite material depends on the result of the interaction between the heat transfer of electrons and the lattice vibration of the polymer and the filler.
As mentioned above, the importance of thermally conductive plastics for LED lamps is self-evident. With the increasing demand for plastics in LED lights, light radiators, electric vehicles, medical equipment and light vehicles, the prospects are very optimistic.
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