In the luminaire solution using LV LED light source, since the LED light source works in a low voltage (VF=3.2V), high current (IF=300～700mA) working state, it generates a lot of heat, and the traditional luminaire has a small space and a small area. It is difficult for the Housing to dissipate heat quickly. Although a variety of heat dissipation schemes were adopted, the results were not satisfactory and became an unsolvable problem for LED lighting fixtures. We are always looking for materials that are easy to use, have good thermal conductivity, and low-cost heat dissipation materials.
At present, after the LED light source is powered on, about 30% of the electric energy is converted into light energy, and the rest is converted into heat energy. Therefore, to export so much heat energy as soon as possible is a key technology in the structural design of LED lamps. The heat energy needs to be dissipated through heat conduction, heat convection, and heat radiation. Only by dissipating heat as soon as possible can the cavity temperature in the LED lamp be effectively reduced, and the power supply can be protected from working in a long-lasting high temperature environment, and the premature aging of the LED light source due to long-term high temperature operation can be avoided.
The heat dissipation path of LED lighting
Because the LED light source itself does not have infrared or ultraviolet rays, the LED light source itself has no radiation heat dissipation function. The heat dissipation method of the LED lighting fixture can only export heat through the Housing closely combined with the LED lamp bead plate. The Housing must have the functions of heat conduction, heat convection, and heat radiation.
Any Housing, in addition to being able to quickly conduct heat from the heat source to the surface of the Housing, the main thing is to dissipate heat into the air by convection and radiation. Heat conduction only solves the way of heat transfer, and thermal convection is the main function of the Housing. The heat dissipation performance is mainly determined by the heat dissipation area, shape, and the ability of natural convection intensity. Thermal radiation is only an auxiliary function.
Generally speaking, if the distance from the heat source to the surface of the Housing is less than 5mm, as long as the thermal conductivity of the material is greater than 5, the heat can be exported, and the rest of the heat dissipation must be dominated by thermal convection.
Most LED lighting sources still use low voltage (VF=3.2V) and high current (IF=200～700mA) LED lamp beads. Due to the high heat during operation, aluminum alloy with higher thermal conductivity must be used. Usually there are die-cast aluminum Housing, extruded aluminum Housing, and stamped aluminum Housing. Die-casting aluminum Housing is a technology of pressure casting parts. The liquid zinc, copper, and aluminum alloy is poured into the inlet of the die-casting machine, and the die-casting machine is die-casted to cast a Housing with a shape limited by a pre-designed mold.
Die-cast aluminum Housing
The production cost is controllable, the heat dissipation wing cannot be made thin, and it is difficult to enlarge the heat dissipation area. The commonly used die-casting materials for LED lamp heat sinks are ADC10 and ADC12.
Extruded aluminum Housing
The liquid aluminum is extruded through a fixed die, and then the bar is machined and cut into the required shape of the Housing, and the post-processing cost is relatively high. 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. Commonly used materials are AL6061 and AL6063.
Stamped aluminum Housing
It is made into a cup-shaped Housing by punching and pulling up steel and aluminum alloy plates through a punch and die. The inner and outer periphery of the punched Housing is smooth, and the heat dissipation area is limited due to no wings. Commonly used aluminum alloy materials are 5052, 6061, and 6063. The quality of stamping parts is small and the material utilization rate is high, which is a low-cost solution.
The heat conduction of aluminum alloy Housing is ideal, and it is more suitable for isolated switching constant current power supply. For non-isolated switch constant current power supplies, it is necessary to isolate AC and DC, high-voltage and low-voltage power supplies through the structural design of the lamp in order to pass CE or UL certification.
Plastic-clad aluminum Housing
It is a heat-conducting plastic shell aluminum core Housing. The thermal conductive plastic and the aluminum heat sink are formed on the injection molding machine at one time, and the aluminum heat sink is used as an embedded part, which needs to be machined in advance. The heat of the LED lamp bead is quickly transferred to the thermally conductive plastic through the aluminum heat dissipation core. The thermally conductive plastic uses its multiple wings to form air convection for heat dissipation, and uses its surface to radiate part of the heat.
Plastic-coated aluminum Housing generally use the original colors of thermally conductive plastics, white and black, and black plastic plastic-coated aluminum Housing have a better radiation heat dissipation effect. Thermally conductive plastic is a kind of thermoplastic material. The fluidity, density, toughness and strength of the material are easy to be injection molded. It has good resistance to cold and heat shock cycles and excellent insulation properties. The emissivity coefficient of thermally conductive plastic is better than that of ordinary metal materials.
The density of thermally conductive plastic is 40% lower than that of die-cast aluminum and ceramics. The weight of the plastic-clad aluminum can be reduced by nearly one-third for the same shape of the Housing. Compared with the all-aluminum Housing, the processing cost is low, the processing cycle is short, and the processing temperature is low; The finished product is not fragile; the customer-provided injection molding machine can carry out the design and production of the differentiated appearance of the lamp. The plastic-clad aluminum Housing has good insulation performance and is easy to pass safety regulations.
High thermal conductivity plastic Housing
The high thermal conductivity plastic Housing has developed rapidly recently. The high thermal conductivity plastic Housing is an all-plastic Housing. Its thermal conductivity is dozens of times higher than that of ordinary plastic, reaching 2-9w/mk. It has excellent heat conduction and heat radiation capabilities. ; A new type of insulating and heat-dissipating material that can be applied to various power lamps, and can be widely used in various LED lamps of 1W～200W.