Product
High-power LEDs are sensitive components. Heat dissipation and reliability are the main factors affecting the application of high-power LEDs. So what should be paid attention to when using high-power LED light sources?
Heat dissipation
Due to the limitations of semiconductor light-emitting diode chip technology, the photoelectric conversion efficiency of LEDs needs to be improved, especially for high-power LED lamp beads. Because of their high power, about 60% of the electrical energy will be converted into heat energy for release (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 applying high-power LED products to ensure the normal operation of high-power LED lamp beads.
1. Heat sink requirements.
Appearance and material: If the sealing requirements of the finished product are not high, it can directly convect with the external air environment. It is recommended to use aluminum or copper heat sinks with fins.
2. Effective heat dissipation surface area:
For 1W high-power LED white light (other colors are basically the same), some users use heat sinks, and the total effective heat dissipation surface area is ≥50-60 square centimeters. For 3W products, the total effective heat dissipation surface area of the heat sink is recommended to be ≥150 square centimeters. For higher powers, the area should be increased according to the situation and test results. Try to ensure that the heat sink temperature does not exceed 60℃.
3. Connection method:
When connecting the high-power LED lamp bead substrate to the heat sink, please ensure that the two contact surfaces are flat and in good contact. To strengthen the bonding degree of the two contact surfaces, it is recommended to apply a layer of thermal conductive silicone grease (thermal conductivity of thermal conductive silicone grease ≥3.0W/m.k) on the bottom of the LED substrate or the surface of the heat sink. The thermal conductive silicone grease is required to be applied evenly and in an appropriate amount and then fixed with screws.
Static electricity protection
Because LED is a semiconductor device, it is more sensitive to static electricity, especially for white, green, blue, and purple LED lamp beads, so it is necessary to prevent and eliminate static electricity
1. Generation of static electricity:
Friction: In daily life, any two objects of different materials can generate static electricity when they come into contact and then separate, and the most common way to generate static electricity is frictional charging. The better the insulation of the material, the easier it is to generate frictional charging. In addition, any two objects of different materials can also generate static electricity after contacting and then separating.
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 repulsion and opposite attraction, and charge will be generated on its surface.
Conduction: 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 lamp beads:
Due to the heat generated by the instantaneous electric field or current, the LED lamp beads are partially injured, which is manifested as a rapid increase in leakage current. They can still work, but the brightness is reduced (the white light will change color) and the life is damaged.
Because the electric field or current destroys the insulation layer of the LED lamp beads, the device cannot work (completely destroyed), which is manifested as 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 LED lamp beads must take measures to prevent and eliminate static electricity, mainly including:
The workshop is laid with anti-static flooring and grounded.
The workbench is an anti-static workbench, and the production machine is well grounded.
The operator wears anti-static clothing, anti-static wristbands, gloves or footbands.
Use ion blowers, and take grounding measures for soldering irons.
The packaging is made of anti-static materials.
Welding
Please pay attention to the selection of constant temperature soldering irons when welding. The welding temperature is 260℃, and the contact time between the soldering iron and the LED pad should not exceed 3S at a time (note that the soldering iron must be grounded during welding, and the operator must wear an anti-static wristband or blow an ion blower)
The four-drive circuit follows the volt-ampere characteristic curve of the diode. If the drive voltage floats, the corresponding drive current drifts greatly, which is easy to damage the lamp beads. Therefore, it is recommended to use a more stable constant current drive power supply or IC instead of a constant voltage drive power supply or IC.