LED packaging process Due to the different structure of the LED, there are some differences in the packaging process, but the key processes are the same. The main processes of LED packaging are: die bonding → wire bonding → sealing glue → cutting feet → grading → packaging.
Key technology of high-power light-emitting diode packaging
2.1 Requirements for packaging technology. High-power LED packaging involves light, electricity, heat, structure and technology, and these factors are both independent and influential. It is only the purpose of packaging, electricity, structure and technology are the means, heat is the key, and performance is the concrete manifestation of the packaging level. Considering process compatibility and reducing production costs, the LED package design and chip design should be carried out at the same time. Otherwise, after the chip is manufactured, the chip structure may be adjusted due to the needs of the package, which may prolong the product development cycle and cost, or even Will not be able to achieve mass production.
2.2 Package structure design and heat dissipation technology The photoelectric conversion efficiency of light-emitting diodes is only 20% to 30%, and 70% to 80% of the input electrical energy is converted into heat. The heat dissipation of the chip is the key. Low-power light-emitting diode packaging generally uses silver glue or insulating glue to bond the chip in the reflector cup, complete the internal and external connections by welding gold wires (or aluminum wires), and finally encapsulate with epoxy resin.
2.3 Optical design technology Different use products have different requirements on the color coordinate, color temperature, color rendering, light intensity, and spatial distribution of light-emitting diodes. In order to improve the light extraction efficiency of the device and achieve a better light extraction angle and light distribution curve, the chip reflector and lens need to be optically designed.
2.4 The choice of potting glue The role of potting glue has two points: (1) Mechanically protect the chip and gold wire; (2) As a light guide material, it can lead out more light. During packaging, the loss caused by the light emitted from the light-emitting diode chip mainly includes: (1) the reflection loss of photons at the exit interface of the light-emitting diode chip due to the difference in refractive index (ie Fresnel loss); (2) optical absorption; (3) Total internal reflection loss. Therefore, coating a layer of transparent optical material with a relatively high refractive index on the surface of the chip can reduce the loss of photons at the interface and improve the light extraction efficiency. Commonly used potting adhesives are epoxy resin and silica gel. Epoxy resin has low viscosity, good fluidity, moderate curing speed, no bubbles after curing, smooth surface, good gloss, high hardness, good moisture-proof, waterproof and dust-proof performance, resistance to damp heat and atmospheric aging, low cost, and luminous Diode packaging is preferred. Silica gel has the characteristics of high light transmittance, good thermal stability, high refractive index, low moisture absorption, and low stress. It is better than epoxy resin, but the cost is higher.
2.5 Phosphor powder coating amount and uniformity control technology The luminous efficiency and light quality of high-power white light emitting diodes are related to the choice of phosphor powder and the process. The choice of phosphor includes the matching of excitation wavelength and chip wavelength, particle size and uniformity, excitation efficiency and so on. The phosphor coating is adjusted according to the luminescence distribution of the blue chip to make the mixed white light uniform, otherwise a blue-yellow circle phenomenon will occur, which will seriously affect the quality of the light source and greatly reduce the excitation efficiency.
