5 Popular Light Fixture Heatsinks, What Is The Difference?
by PengLight | Date: 18th-Mar, 2023
One of the biggest technical challenges of LED lighting fixtures currently is the issue of heat dissipation. Poor heat dissipation can cause the weakness of LED drivers and electrolytic capacitors which prevents lighting fixtures from further developing and resulting in early light decay. Only by quickly transmitting the heat out can reduce the luminaire temperature effectively, as well as protect the power supply from working in a prolonged high-temperature environment. Also, it helps to avoid the early light decay of LED light sources due to long-term high-temperature operation.
Because LED light sources do not have infrared rays and ultraviolet rays, the light source itself has no radiation heat dissipation function. The lighting fixture can only transmit heat via the heat sink that is closely attached to the LED chip board. Therefore, the heat sink must have the functions of heat conduction, heat convection, and heat radiation.
For any heatsink, in addition to quickly transmitting heat from the heat source to the surface of the radiator, the most important thing is to dissipate heat to the air by convection and radiation. Heat conduction only solves the way of heat transfer, while heat convection is the main function of the heat sink. The heat dissipation performance is mainly determined by the heat dissipation area, shape, and the ability of natural convection intensity. Heat radiation is only an auxiliary function. Generally speaking, if the distance from the heat source to the surface of the heat sink is less than 5mm, then as long as the thermal conductivity of the material has a coefficient greater than 5, the heat can be transmitted, and the rest of the heat dissipation must be dominated by heat convection.
As most LED luminaires still use LED chips with low voltage (VF = 3.2V) and high current (IF = 200-700mA), which generate more heat during operation, LED luminaires must use aluminum alloys with high thermal conductivity. Usually, there are die-cast aluminum heat sinks, extruded aluminum heat sinks, and stamped aluminum heat sinks. The die-cast aluminum heat sink is a technology of pressure casting parts. Liquid zinc-copper-aluminum alloys are poured into the feeding port of the die-casting machine, and the die-casting machine is used to cast the heat sink into the shape specified by the pre-designed mold.
Without further ado, let’s check the following 5 popular light fixture heatsinks.
Die-cast Aluminum Heatsink
A die-cast aluminum heatsink is a type of heat sink made from aluminum that has been cast using a die-casting process. The die-casting process involves injecting molten aluminum into a mold or die under high pressure, which results in a highly precise and consistent shape.
Die-cast aluminum heatsinks are commonly used in electronic devices and LED light fixtures to dissipate heat generated by electronic components such as transistors, LED chips, diodes, and integrated circuits. The heatsink’s shape and size are designed to maximize surface area and increase airflow, allowing heat to be efficiently transferred away from the electronic components and into the surrounding environment.
The die-casting process also allows for complex shapes and designs to be created, which can further improve the heatsink’s performance. The production cost is controllable, but the heat dissipation fins cannot be made thinner, and it is difficult to maximize the heat dissipation area. The commonly used die-casting materials for LED light fixture heatsinks are ADC10 and ADC12.
Extruded Aluminum Heatsinks
Extruded aluminum heatsinks are a type of light fixture heatsinks in which liquid aluminum is extruded through a fixed mold, and then the bar is cut into the required shape by machining. The heatsinks are often designed with fins or ridges that increase the surface area, allowing for greater heat dissipation. They are widely used in LED lights to dissipate heat generated by LED chips, and power supplies, to dissipate heat generated by components.
Though the post-processing cost is relatively high compared to the die-cast aluminum heatsink, the heat dissipation fins can be produced much thinner, and the heat dissipation area can be expanded to the greatest extent. When the heat dissipation fins work, air convection is automatically formed to diffuse heat, and the heat dissipation effect is better. The most commonly used materials for LED lighting are AL6061 and AL6063.
Stamped Aluminum Heatsinks
The stamped aluminum heatsink is made by punching and pulling up the steel and aluminum alloy plates with a punching machine and mold to make it into a cup-shaped heatsink. The heatsinks are then attached to the light fixture using screws or other fasteners. The popular items we can see using stamped aluminum heatsinks are LED downlights and LED spotlights.
The inner and outer periphery of the heat sink formed by stamping is smooth, but the heat dissipation area is limited due to the absence of wings. Commonly used aluminum alloy materials are 5052, 6061, and 6063. The quality of stamping parts is very small, and the material utilization rate is high, which is a low-cost solution.
The heat conduction of the aluminum alloy radiator is relatively ideal, and it is more suitable for an isolated switching constant current power supply. For non-isolated switching 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 lamps, in order to pass CE or UL certification.
Plastic-clad Aluminum Heatsink
The plastic-clad aluminum heatsink consists of a heat-conducting plastic shell and an aluminum core. The heat-conducting plastic shell and aluminum core are molded together in one step using an injection molding machine, with the aluminum heat sink being embedded and requiring prior mechanical processing. The heat generated by the LED chip is quickly conducted to the thermally conductive plastic through the aluminum heat sink, and the thermally conductive plastic uses its multiple fins to create air convection for heat dissipation, as well as its surface radiation to dissipate some of the heat.
Plastic-clad aluminum heat sinks generally use their original colors of heat-conducting plastics, which are white and black. The black plastic-clad aluminum heat sink has a slightly better heat dissipation effect. Thermal conductive plastic is a thermoplastic material that is easy to injection mold due to its fluidity, density, toughness, and strength. It has good resistance to cold and heat shock cycle characteristics, and excellent insulation performance.
The thermal radiation coefficient of heat-conducting 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, and the weight of plastic-coated aluminum can be reduced by nearly one-third for the same shape of the heatsink.
Compared with an all-aluminum heatsink, plastic-clad aluminum heatsinks have the advantage of low processing cost, short processing cycle, low processing temperature, and the finished product is not fragile. The customer’s own injection molding machine can carry out a distinct design and production of LED lamps. The plastic-clad aluminum radiator has good insulation performance and is easy to pass safety regulations, such as EMC and LVD.
High Thermal Conductive Plastic Heatsink
High thermal conductive plastic radiator has developed rapidly recently. It is an all-plastic heatsink and its thermal conductivity is dozens of times higher than that of ordinary plastic, up to 2-9w/MK. Also, it has excellent heat conduction and heat radiation capabilities. It is a new type of insulation and heat dissipation material that can be applied to various light fixtures from 1W to 200W.
The withstand voltage level of high thermal conductivity plastic can reach AC 6000V, which is suitable for non-isolated switch constant current power supply and high voltage linear constant current power supply of HVLED. Make this kind of LED lighting fixture easy to pass strict safety inspections such as CE, TUV, and UL.
High thermal conductive plastic heatsinks are produced by traditional injection molding or extrusion molding machines. Once formed, the finished product has a high finish. They can be designed with many precise heat dissipation fins. The heat dissipation fins can be made many and thin, and the heat dissipation area is expanded to the maximum. When the heat dissipation fins work, air convection is automatically formed to diffuse heat, and the heat dissipation effect is better. The heat of the LED lamp beads is directly sent to the heat dissipation fins through the high thermal conductivity plastic, and the heat is quickly dissipated through air convection and surface radiation.
High thermal conductive plastic heatsinks are lighter in density than aluminum. The density of aluminum is 2700kg/m3, while the density of plastic is 1420kg/m3, which is almost half of that of aluminum. Therefore, the weight of a plastic heatsink with the same shape is only 1/2 of that of aluminum. Moreover, the processing is simple, and the molding cycle can be shortened by 20-50%, which also reduces the driving force of the cost.
Passive Heatsinks Versus Active Heatsinks
A passive heatsink is a type of cooling system used to dissipate heat from a component or device without the use of any external power source. They’re made of aluminum or copper and rely on natural convection to dissipate heat. The heat generated by the component such as LED chips is transferred to the heatsink through thermal conduction and then dissipated into the surrounding air by natural convection.
Passive heatsinks are widely used in electronic devices such as computers, power supplies, and LED lights, where noise-free operation and low power consumption are essential. They are a good option for low-power LED light fixtures that do not generate a lot of heat. The 5 popular heat sinks we mentioned above are all passive heatsink types.
Active heatsinks use a fan to increase airflow and improve heat dissipation. They are cooling systems that use a combination of passive and active cooling methods to dissipate heat from electronic components. They typically consist of a heatsink, a fan, and a thermal interface material. The heatsink is a metal structure that absorbs heat from the component, and the fan blows air over the heatsink to increase the heat dissipation rate. The thermal interface material helps to improve the contact between the component and the heatsink, allowing for better heat transfer.
Active heatsinks can be also used in high-power LED fixtures and grow lights. They are generally more effective at dissipating heat than passive heatsinks, but they are also more expensive and can be louder due to the fan. In some cases, it also requires more maintenance if the fan is not working and resulting in higher operating temperature.
In general, the choice between passive and active light fixture heatsinks depends on the specific requirements of the LED light fixture. If the fixture generates a lot of heat, an active heatsink may be necessary to prevent overheating and ensure the longevity of the LED chips. If the fixture is low-power and does not generate much heat, a passive heatsink is enough.
Some Things to Consider When Choosing the Best Light Fixture Heatsinks
1. Material: Aluminum is the most common material used as light fixture heatsinks due to its excellent heat dissipation properties. However, now many lighting suppliers also use iron as the radiator. It further reduces the material cost but heat dissipation is not as good as aluminum. By the way, copper material is an excellent thermal conductor, they are highly effective at dissipating heat. The only disadvantage is that they are expensive and heavy.
2. Size: The size of the heatsink should be proportional to the size of the LED light fixture. A larger heatsink will provide better heat dissipation and ensure a cooler environment thus improving light longevity. For example, the size of the heat sink used for 10w flood lights and 100w flood lights are very different.
3. Fin design: The fin design of the heatsink affects the airflow and heat dissipation. A heatsink with a larger surface area and more fins will provide better cooling.
4. Thermal conductivity: The thermal conductivity of the heatsink material affects how quickly heat is transferred away from the LED. A higher thermal conductivity material will provide better cooling.
5. Compatibility: The heatsink should be compatible with the LED light fixture and its mounting system. Normally it should be designed at the first step with the light fixture together.
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