Thermal design of LED lamps

- Aug 24, 2017-

According to the functional needs of the lighting fixtures and the safety level of the lamps and lanterns, we will divide the whole luminaire into three parts to design the whole heat dissipation shell. Light source, drive, radiator.
The heat dissipation effect of the heat sink is mainly determined by the heat sink and the heat sink in the contact part of the heating object. Excellent performance of the radiator, its performance should meet three requirements: fast absorption, heat resistance small, to heat fast.

Endothermic fast: That is, endothermic bottom and LED module between the heat resistance is small, can quickly absorb its generated heat.
In order to achieve this effect, the requirements of the heat-absorbing bottom and LED modules as close as possible, so that metal materials and LED modules direct contact, it is best to leave no gaps.
The overall thermal resistance of the radiator is the accumulation of the contact surface of the LED module, and the heat conduction impedance inside the endothermic bottom is one of the most noticeable parts. In order to effectively transfer the absorbed heat to as many fins as possible, as a result, we also need to have a better transverse heat conduction capacity at the bottom of the endothermic, when we design the luminaire, we first meet the thickness of the endothermic bottom, and consider the installation hole of the LED module as reinforcement, and also strengthen the overall and mechanical strength of the luminaire.

Thermal resistance small: In order to enhance the heat absorption capacity, I hope the heat sink and LED module tightly combined, without leaving any gaps, die-casting surface this is impossible to achieve. There must be a gap between the endothermic bottom and the LED module, which is where the heat-conduction ointment comes in. But the thermal resistance of heat transfer paste is always higher than the processing of metal materials, the use of it is only expedient, not the real solution, in order to fundamentally improve the heat sinks endothermic capacity, we must improve the bottom surface smoothness. Flatness is measured by the height of the surface of the largest drop, usually the bottom of the heat sink can be slightly treated to reach 0.1mm below, the use of milling machine or multi-channel wire drawing treatment can be reached 0.03mm, heat sink heat sinks more flat thermal resistance, the more conducive to heat absorption, but because it can not be perfect, the application of heat-conductive paste has become the LED module installed to the radiator must step, thus achieving the best effect of endothermic.

Go hot: Because we will be led module of endothermic bottom and fin die-casting, that is, can be absorbed from the LED group of energy quickly conduction to the Fin section, the entire lamp body and fins are exposed to the upper part of the air, and our fin direction is parallel to the road, the need to emit hot air and airflow in the direction of the same, not because of the flow of air and the formation of eddy currents caused by the heat of the stranded, and then by the flow of airflow smoothly away and distributed, to the fastest speed of heat distribution.

Current LED main cooling technology
Aluminum extrusion Technology (FIN)
Generally used aluminum extruded materials are AL6063, which has good thermal conductivity (about 200w/m. K) and processability. Advantages and Disadvantages: Easy processing, low cost, mature technology. The disadvantage is the installation is limited more, easy deformation.
Second, aluminum die-casting technology
The commonly used die-casting aluminum alloy is ADC12, suitable for making thin castings, but the heat conduction rate is poor (about 96w/m. K). Advantages and Disadvantages: can be integrated without gap design, waterproof effect is good. The disadvantage is the mold cost is higher, the heat dissipation effect is general, the lamp body is bulky.
Third, heat pipe technology (copper pipe)
The heat pipe and fin fins are generally used. Fin material is generally AA1020 (AL, CA. 200w/m. k) or c1100 (Cu, ca. 400w/m. k), the material structure of heat conductive tubing is complex and has almost perfect heat conduction rate (about 80000~110000 W. k). Pros and Cons: good cooling effect, light weight. The disadvantage is that there is a certain demand for space, can not bear the impact of greater intensity, and the cost is higher.