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Ten technical points to improve the luminous efficiency of LED explosion-proof lamps
First, what is the luminous efficiency of LED explosion-proof lamps?
The luminous efficiency of an LED explosion-proof lamp refers to the luminous efficiency of an electric light source. How much lumen flux is generated by consuming 1 W of electric power, that is, the ratio of luminous flux to power, in units of flow/watt (1 m/W). Generally, the higher the luminous efficiency, the better. Continuous improvement of the luminous efficiency of LED explosion-proof lamps can increase the light output intensity and make the utilization of resources higher. In general, LED explosion-proof lamp manufacturers use the principle of LED lights to improve the luminous efficiency, just like the following:
1. Using electrode optimization or electronic crystals to improve the extended characteristics of the device GaN LED current;
2. Improve the uniformity of current distribution;
3. Reduce the concentration effect of current;
4. Improve the light-emitting efficiency and conversion efficiency of the chip, improve the photoelectric effect of the device, and improve the performance of the product.
Second, the specific measures to improve the luminous efficiency of LED explosion-proof lamps:
1. The change of the shape of the lamp bead of the LED explosion-proof lamp : changing the rectangular appearance shape of the LED explosion-proof lamp is a method for effectively improving the luminous efficiency. It can be changed according to the optical principle.
2, LED explosion-proof lamp surface swearing technology: the internal and external geometry of the component is coarser than the total reflection of the light inside the component, improving the efficiency of the component. The roughening method basically forms a regular concave-convex shape on the geometrical shape of the component, and the structure of the regular distribution is also divided into two forms depending on the position, one is to set the concave-convex shape in the component, and the other is to The way is to make a regular bump shape above the component and a reflective layer on the back of the component. At present, if an ultraviolet component having a wavelength of 405 nm is used, an external quantum efficiency of 43% can be obtained, and the extraction efficiency is 60%. It is the external quantum efficiency and extraction efficiency of the current global location.
3, LED explosion-proof lamp chip adhesion technology: in order to reduce the absorption of light emitted by the GaAs substrate on the LED, some research institutions proposed that the transparent substrate is a paste technology. This is also one of the research directions of LED light chips.
4, LED explosion-proof lamp flip chip packaging technology: FlipChip structure instead of sapphire substrate GaN series of materials will be reversed of the traditional components, and a reflective layer with a higher reflectivity above the p-type electrode, so that the original component The light emitted from above is derived from the other illumination angles of the assembly and is taken from the edge of the sapphire substrate. Such a method can reduce the amount of light output on the electrode side by about twice as much as the conventional package. On the other hand, because the flip-chip structure can directly contact the heat dissipation structure in the package structure directly by the electrode or the bump, the heat dissipation effect of the component is greatly improved, and the luminous flux of the component is further improved.
5, LED explosion-proof lamp transparent substrate technology: remove the GaAs substrate, replaced by a fully transparent GaP crystal. The quantum efficiency was increased from 4% to 2530% due to the removal of the substrate absorption region within the chip. In order to further reduce the absorption of the electrode region, the transparent substrate type InGaAlP device is formed into a truncated inverted cone shape, which further improves the quantum efficiency.
6, LED explosion-proof lamp metal film reflection technology: that is, the MB process, first remove the GaAs substrate, and then simultaneously vaporize the Al metal film on the surface of the Si substrate surface, and then fuse together under a certain temperature and pressure. In this manner, the light that is irradiated from the light-emitting layer onto the substrate is reflected by the Al-based metal film layer to the surface of the chip, thereby improving the luminous efficiency of the device by 2.5 times or more.
7. Surface structure technology of LED explosion-proof lamp: Surface microstructure process is another effective technology to improve the light-emitting efficiency of the device. The basic point of this technology is to etch a large number of small structures on the surface of the chip with the size of light wavelength, each structure. It has a truncated tetrahedron shape, which not only expands the light-emitting area, but also changes the direction of refraction of light at the surface of the chip, so that the light transmission efficiency is significantly improved. Measurements indicate that for devices with a window layer thickness of 20 μm, the light extraction efficiency can be increased by 30%. When the window layer thickness is reduced to 10 μm, the light extraction efficiency will be improved by 60%. For the 585625nm wavelength LED device, after the texture structure is fabricated, the luminous efficiency can reach 30lm/w, and the value is close to the level of the transparent substrate device.
8. LED explosion-proof lamp flip chip technology: A GaN-based LED structure layer is grown on a sapphire substrate by MOCVD technology, and light emitted from the P/N junction light-emitting region is emitted through the upper P-type region. Due to the poor conductivity of P-type GaN, in order to obtain good current expansion, a metal electrode layer composed of NiAu is formed on the surface of the P region by evaporation. The lead of the P region is taken up through the metal film of the layer. To achieve good current spreading, the NiAu metal electrode layer should not be too thin. For this reason, the luminous efficiency of the device is greatly affected, and it is usually necessary to take into account both the current expansion and the light extraction efficiency. However, in any case, the presence of the metal film always deteriorates the light transmission performance. In addition, the presence of wire bonds also affects the light extraction efficiency of the device. The structure using the GaN LED flip chip can fundamentally eliminate the phenomenon that the light transmittance of the metal thin film is poor and the luminous efficiency is poor.
9, LED explosion-proof lamp chip bonding technology: With the gradual understanding of the bonding mechanism and the gradual maturity of bonding process technology, chips of different materials have been able to achieve mutual bonding, which may form some special purposes Materials and devices. A new structure can be formed by forming a silicide layer on a silicon wafer and bonding. Since the conductivity of the silicide is high, it can replace the buried layer in the bipolar device, thereby reducing the RC constant.
10, LED explosion-proof lamp laser stripping technology: laser stripping technology (LLO) is the use of laser energy to decompose the GaN buffer layer at the GaN / sapphire interface, thereby achieving the separation of the LED epitaxial wafer from the sapphire substrate. The technical advantage is that the epitaxial wafer is transferred to a heat sink with high thermal conductivity, which can improve current spreading in a large-sized chip. The n-face is the light-emitting surface: the light-emitting area is increased, the electrode block light is small, the microstructure is easy to be prepared, and etching, grinding, and dicing are reduced. More importantly, the sapphire substrate can be reused.