Since long time, the biggest technical problem of LED lighting fixtures is the heat dissipation.Poor heat dissipation has led to LED driving power and electrolytic capacitors becoming shortcomings for the further development of LED lighting fixtures, and the cause of the premature decline of LED light sources.
In the lighting solution using LV LED light source, because the LED light source works in a low voltage (VF=3.2V), high current (IF=300～700mA) working state, it produce a lot of heat, and the space of traditional luminaries is narrow and small. The heat sink has difficulty dissipating heat quickly. Although a variety of heat dissipation method were used, the results were not satisfactory, which became an unsolvable problem for LED lighting fixtures. The search for easy-to-use, good thermal conductivity, and low-cost heat dissipation materials is always a work in progress.
At present, after the LED light source is powered on, about 30% of the electrical energy is converted into light energy, and the rest is converted into heat energy. Therefore, to export so much heat as soon as possible is the key technology of LED lighting structure design, heat energy needs to be distributed through heat conduction, thermal convection, thermal radiation. Only to export heat quickly can effectively reduce the temperature of the cavity within the LED lighting, to protect the power supply is not in a sustained high-temperature environment, to avoid the LED light source due to long-term high-temperature work and premature failure.
The heat dissipation path of LED lighting
Because the LED light source does not have infrared and ultraviolet rays, it does not have a radiation heat dissipation function. The heat dissipation path of the LED lighting fixture can only export heat through the radiator closely combined with the LED lamp bead plate. The heat sink must have the functions of heat conduction, heat convection, and heat radiation.
Any heat sink, besides being able to quickly conduct heat from the heat source to the surface of the radiator, the main thing is still to rely on convection and radiation to distribute heat into the air. Thermal conductivity only solves the path of heat transfer, and thermal convection is the main function of the radiator, heat dissipation performance is mainly determined by the heat dissipation area, shape, the ability of natural convection strength, thermal radiation is only a secondary role.
Generally speaking, if the distance from the heat source to the surface of the radiator is less than 5mm, as long as the thermal conductivity of the material is > 5, the heat can be exported, and the rest of the heat dissipation must be dominated by thermal convection.
Most LED light source still use low voltage (VF = 3.2V), high current (IF = 200 to 700mA) LED chips, which must use aluminum alloy with high thermal conductivity due to high heat during operation. There are usually die-cast aluminum heat sink, extruded aluminum heat sink, and stamped aluminum heat sink.
Die-cast aluminum heat sink is a pressure casting technology, liquid zinc-copper-aluminum alloy is poured into the inlet of the die-casting machine, die-cast by the machine, casting out the shape of the heat sink limited by the pre-designed mold.
Die-cast aluminum heat sink
LED lamps heat sink normally used die-casting materials for ADC10 and ADC12.The unit cost not high but tooling cost not low, the heat sink wing can not be made thin, it is difficult to make the heat sink area large.
For some integrated design the die-casting heat sink has more advantages because it’s various shapes
Extruded aluminum heat sink
The liquid aluminum is extruded through a fixed die, and then the bar is machined and cut into the required shape of the radiator, the processing cost is higher. The radiating wing can be made many and thin, and the heat dissipation area is expanded to the maximum. When the radiating wing is working, air convection is automatically formed to diffuse heat, and the heat dissipation effect is better. Usually used materials are AL6061 and AL6063.
The extruded aluminum heat sink is widely used on the led down light, led track light, led ceiling light because of its high performance & low cost.
Stamped aluminum heat sink
It is a heat sink made of steel and aluminum alloy by stamping and pulling up the sheet through a punch and die to make it cup and cylinder type. The heat sink formed by stamping has smooth inner and outer periphery but limited heat dissipation area because of no wings.
Normally used aluminum alloy materials are 5052, 6061, 6063. the quality of the stamped parts is very small, and the material utilization rate is high, which is a low-cost solution.
The thermal conductivity of stamp aluminum heat sink is good and more suitable for isolated switching constant current power supply. For non-isolated switching constant current power supply, it is necessary to do a good job of isolating AC and DC, high voltage and low voltage power supply through the structural design of the luminaire in order to pass CE or UL certification.
Plastic-clad aluminum heat sink
It is a kind of heat sink with aluminum core in thermal conductive plastic shell. The heat of the LED beads is quickly conducted to the heat-conducting plastic through the aluminum heat sink core, and the heat-conducting plastic uses its multiple wings to form air convection heat dissipation, using its surface to radiate part of the heat.
Plastic clad aluminum radiator generally use the original color of the thermal conductive plastic white and black, black plastic plastic clad aluminum radiator radiation heat dissipation effect is a little better. Thermally conductive plastic a thermoplastic material, material fluidity, density, toughness, strength are easy to injection molding, with good resistance to cold and thermal shock cycle characteristics, excellent insulation properties. Thermal conductive plastic radiation coefficient is better than ordinary metal materials.
The density of thermally conductive plastic is 40% smaller than that of die-cast aluminum and ceramic, and the weight of plastic-coated aluminum can be reduced by nearly one-third for the same shaped radiator; compared with all-aluminum radiators, the processing cost is low, the cycle is short, and the temperature is low; the finished product is not fragile; the customer can have his own injection molding machine for the production of differentiated shape design of lamps and lanterns. The heat sink with aluminum cladding has good insulation performance and can easily pass safety regulations.
High thermal conductivity plastic heat sink
High thermal conductivity plastic heat sink recently developed rapidly, it is an all-plastic heat sink, its thermal conductivity is dozens of times higher than ordinary plastic, up to 2-9w / mk, with excellent heat conduction, thermal radiation capabilities; can be applied to a variety of power lights of new insulating heat dissipation materials, can be widely used in 1W ~ 200W of various types of LED lamps.
High thermal conductivity plastic withstand voltage level up to AC 6000V, suitable for non-isolated switch constant current power supply, HVLED’s high voltage linear constant current power supply. HVLED adopts high voltage (VF = 35-280VDC) and low current (IF = 20-60mA) working condition, so the heat generation of HVLED lamp bead board is reduced. High thermal conductivity plastic heat sink is available with traditional injection and extrusion machines.
It can be one-time molding, with good finishing of finished products. Significantly improve the production efficiency, high flexibility of modeling design, can give full play to the designer’s design concept. High thermal conductivity plastic radiator is made of PLA (corn starch) polymerization, full degradation, no residue, no chemical pollution, production process without any heavy metal pollution, no sewage, no waste gas, totally in line with global environmental protection requirements.
High thermal conductivity plastic heat sink can be designed with many precision cooling wings, the cooling wings can be made many and very thin, the maximum expansion of the heat dissipation area, cooling wings work automatically form air convection diffusion of heat, heat dissipation effect is better. the heat of the LED lamp beads through the high thermal conductivity plastic directly to the cooling wings, through air convection and surface radiation rapid heat dissipation.
Our LED lighting product will choose the suitable heat sink according to the design and style of the light. The extruded aluminum heat sink is mostly widely use on the led lighting products now.