Analysis of characteristics and technical parameters of high-power LED lamp beads

  High-power LED lamp beads are a type of LED lamp beads. Compared with low-power LED lamp beads, high-power LED lamp beads have higher power, brighter brightness, and higher prices. The rated current of low-power LED lamp beads is 20mA, and those with a rated current higher than 20mA can basically be considered high-power. The general power numbers are: 0.25w, 0.5w, 1w, 3w, 5w, 8w, 10w, etc. The main brightness unit is lm (lumen), and the low-power brightness unit is generally mcd (millicandela, 1cd=1000mcd), which is the luminous intensity I.

    1cd=1lm/sr (lumen/steradian)=1 candlelight. Explained as: the luminous flux emitted by the light source within the solid angle dΩ in the specified direction or the luminous flux dΦ transmitted by the light source, the quotient of the two is the luminous intensity I (unit: candela, cd). The outer cover can be made of PC tube, high temperature resistance of 135 degrees.

    High power LED product categories:

    At present, as an emerging green, environmentally friendly, energy-saving light source, it is widely used in car lights, flashlights, lamps and other places. The reason why LED high power is called this is mainly for low-power LED. There are three classification standards:

    The first type is divided into 0.5W, 1W, 3W, 5W, 10W...100W according to the power size, which varies according to the total power of the molded product after packaging.

    The second type can be divided into: large-size epoxy resin packaging, piranha-like epoxy resin packaging, aluminum substrate (MCPCB) packaging, TO packaging, power SMD packaging, MCPCB integrated packaging, etc. according to its packaging process.

    The third type can be divided into low light attenuation high-power products and non-low light attenuation high-power products according to their light attenuation levels.

    Of course, since high-power LEDs have many parameters, there are different classification standards based on different parameters, which will not be described here. High-power LEDs are still a type of LED packaging product, and are the most important link in the transition of semiconductor lighting to the field of general lighting.

    High-power LED product application considerations

    During the application of high-power LED products and devices, heat dissipation, electrostatic protection and welding have a great impact on their characteristics, which need to be paid great attention by application-end customers.

    1. Heat dissipation of high-power LED products :

    Due to the limitations of current semiconductor light-emitting diode chip technology, the photoelectric conversion efficiency of LEDs needs to be improved, especially for high-power LEDs. Because of their high power, more than 60% of the electrical energy will be released as heat (with the development of semiconductor technology, the photoelectric conversion efficiency will gradually increase). This requires end customers to do a good job of heat dissipation when using high-power LED products to ensure the normal operation of high-power LED products.

    1. Heat sink requirements

    Appearance and material: If the sealing requirements of the finished product are not high and it can directly convect with the external air environment, it is recommended to use an aluminum or copper heat sink with fins.

    2. Effective heat dissipation surface area:

    For 1W high-power white LEDs (other colors are basically the same), our company recommends that the total effective heat dissipation surface area of ​​the heat sink be ≥50-60 square centimeters. For 3W products, the recommended total effective heat dissipation surface area of ​​the heat sink is ≥150 square centimeters. For higher powers, the amount will be increased based on the situation and test results, and the heat sink temperature should be kept at no more than 60°C.

    3. Connection method:

    When connecting the high-power LED substrate to the heat sink, please ensure that the two contact surfaces are flat and in good contact. To strengthen the bonding between the two contact surfaces, it is recommended to apply a layer of thermal grease (thermal conductivity of thermal grease ≥ 3.0W/mk) on the bottom of the LED substrate or the surface of the heat sink. The thermal grease is required to be applied evenly and in an appropriate amount, and then fixed with screws.

    2. Electrostatic protection of high-power LED products

    LED is a semiconductor device and is sensitive to static electricity. Especially for white, green, blue and purple LEDs, it is necessary to prevent and eliminate static electricity.

    1. Generation of static electricity:

    ① Friction: In daily life, static electricity can be generated when any two objects of different materials come into contact and then separate. The most common way to generate static electricity is by friction. The better the insulation of a material, the easier it is to generate electricity by friction. In addition, static electricity can also be generated when any two objects of different materials come into contact and then separate.

    ② Induction: For conductive materials, since electrons can flow freely on its surface, if it is placed in an electric field, positive and negative ions will be transferred due to like charges repelling each other and opposite charges attracting each other, and electric charges will be generated on its surface.

    ③Conduction: For conductive materials, since electrons can flow freely on its surface, if it comes into contact with a charged object, charge transfer will occur.

    2. The harm of static electricity to LED:

    ① Due to the heat generated by the instantaneous electric field or current, the LED is partially damaged, which is manifested as a rapid increase in leakage current. It can still work, but the brightness is reduced and the life is shortened.

    ② The electric field or current destroys the LED's insulation layer, rendering the device unable to work (completely destroyed), resulting in a dead light.

    3. Static electricity protection and elimination measures:

    For the entire process (production, testing, packaging, etc.), all employees who have direct contact with LEDs must take measures to prevent and eliminate static electricity, mainly including:

    1. The workshop is equipped with anti-static floor and grounded.

    2. The workbench is an anti-static workbench and the production machine is well grounded.

    3. The operator should wear anti-static clothing, anti-static wristbands, gloves or footbands.

    4. Use ion fan.

    5. Take proper grounding measures for the soldering iron.

    6. The packaging is made of anti-static material.

    3. Welding of high-power LED products

    1. When soldering, please note that it is best to use a constant temperature soldering iron. The soldering temperature should be below 260°C, and the contact time between the soldering iron and the LED pad should not exceed 3S.

    2. For high-power LEDs encapsulated with silicone, the maximum heat-resistant temperature of silicone is 180°C, so the soldering temperature of the LED should not exceed 170°C. Use a low-temperature soldering iron and low-temperature solder paste (wire) for soldering, and the contact time between the soldering iron and the LED pad should not exceed 3S at a time.

    Scope of application:

    Mainly used in hotels, plazas, bars, parks, playgrounds, public places and all lamps that require light sources.

    Classification:

    The reason why LED high power is called this is mainly for low power LED. At present, I have summarized three classification standards:

    The first type is divided into 0.5W, 1W, 3W, 5W, 10W...100W according to the power size, which varies according to the total power of the molded product after packaging.

    The second type can be divided into: large-size epoxy resin packaging, piranha-like epoxy resin packaging, aluminum substrate (MCPCB) packaging, TO packaging, power SMD packaging, MCPCB integrated packaging, etc. according to its packaging process.

    The third type can be divided into low light attenuation high-power products and non-low light attenuation high-power products according to their light attenuation levels.

    Of course, since high-power LEDs themselves have many parameters, there will be different classification standards based on different parameters, which will not be discussed here.

    High-power LED is still a kind of LED packaging products, and it is the most important link for semiconductor lighting to move towards the field of general lighting. A deep understanding of high-power LED packaging and mastering various technical parameters and characteristics are important for understanding LED lighting and display products.