Among many green light application solutions, LED is a light source technology that is more energy-saving and easier to assemble and design than other light source solutions. Among them, the high-power white LED is the most frequently used light-emitting component in the application of lighting sources. However, Although white LED in luminous efficiency, single power performance in all aspects of research and development have progress, in fact, there are still white light LED uniformity of light, the life of packaging materials and other issues, especially in the application of chip cooling restrictions, the development of LED light source applications must first Improve the problem ...
High-power white LED used for daily lighting purposes, in fact, the increasing emphasis on environmental light, has become the primary choice for the development of environmentally friendly light source. However, in fact there are still many technical bottlenecks for white LEDs that need to be overcome. At present, relevant improvement solutions have been put in place to enhance the white LED design bottlenecks in terms of uniformity of illumination, lifetime of packaging materials, heat dissipation enhancement, etc., and focus on functions and performance Improvement.
Demand for environmentally friendly light sources to increase high-power white LED applications qualify
LED light source favored the main reason, nothing more than long product life, light - electricity conversion efficiency, material characteristics can be embedded in any plane and other characteristics. However, in the development of daily lighting sources, due to the need to achieve practical "lighting" needs, the original purpose of the LED can not directly correspond to lighting applications, must be from the chip, package, carrier board, production technology and external circuits in all aspects of strengthening, In order to achieve the lighting needs of high-power, high brightness lighting effects.
To observe the market demand level, the white LED developed for the lighting application market can be said to be a product project with a higher dosage in the future. However, in order to achieve the utility function, the white LED must be improved in key functions for lighting applications. One is to strengthen the LED chip, for example, to increase its light-to-electricity conversion efficiency, or increase the chip area, so that a single LED's luminous flux (flux) reached its design limit. Second, it is a more eclectic design, if continue to increase the size of a single LED chip is more difficult under the premise of using multiple LED chips packaged in the same light source module, but also can reach the above approach to practical technical solutions .
Multi-chip package to meet the low-cost, high-brightness design requirements
View on industry practice needs, due to mass production flexibility, design difficulty and control product yield / cost issues, LED chips continue to increase the cost and yield will face the design bottleneck. A flash chip design area may encounter difficulties, not technically and production technology can not be done, but in terms of cost and efficiency considerations, the large area of ​​the LED chip cost is higher, but also for the actual manufacturing needs change Lower design flexibility.
Instead, the multi-chip integrated packaging method is used to make the equidistant arrangement of a plurality of LED chiplets on the carrier board. The chips are connected by wire bonding and integrated with the optical packaging material to form a light source module product, and more Chip package can be used in chip testing, the use of secondary processing integrated into a large chip equivalent light source module, but in the production of more flexible than the single-chip design LED light source components to be more flexible.
At the same time, multi-chip LED chip module solutions, the production costs can also be significantly reduced because of chip costs, equal to monolithic design equivalent flux, with lower cost development options.
Multi-chip integrated light module still need to consider the cost-benefit maximization
Another development direction is to continue to increase the area of ​​LED chips, through a large area to obtain high brightness, high luminous flux output. However, too large LED chip area will appear as expected design problems, the common improvement program to modify the crystal structure, made in the chip surface to improve; but the related improvement programs also easily affect the cooling efficiency of the chip itself, especially in the light source Most of the LED modules to be used are driven under high power to obtain higher luminous flux, which will result in that the high heat collected by the chip junction during the light-emitting process of the chip is not easily dissipated and the application flexibility of the module products and the active / passive Thermal design.
The general design, according to the analysis adopted 7mm2 chip size, the luminous efficiency of the best, but 7mm2 large chip in the yield and light performance control is not easy, the cost is relatively high; instead of using multi-chip, such as 4 Chip or 8 low-power chip, secondary processing in the carrier with the package material to form a LED light source module, is more able to quickly develop the desired brightness, power LED light source module performance of the product design.
For example, Philips, OSRAM, CREE and other light source products manufacturers, the introduction of 4,8 or more small LED chip package LED light source module products. However, this type of high-brightness LED chip architecture using a few components also caused some design issues, such as: multiple LED chip package that must be built with a built-in insulating material, in order to avoid the LED chips each short circuit phenomenon; this process is relatively There are many programs in a monolithic design, so even if the cost savings can be achieved over a monolithic solution, the cost gap between the two solutions is reduced due to the extra insulation process.
Improve the surface of the chip application process can also be enhanced LED light output
In addition to increasing the chip area or number is the most direct way, there is another kind of light-emitting performance improvement for the material properties of the chip itself. For example, an uneven surface structure can be fabricated on an LED sapphire substrate. Using this uneven surface to enhance LED light output, a texture surface crystalline structure is established on the surface of the chip.
OSRAM is to use this program to develop ThinGaN high brightness products, first in the InGaN layer to form a metal film material, and then stripping process, so that the surface after stripping can indirectly get higher light output! OSRAM claims that this technology allows the same chip to obtain 75% light extraction efficiency.
On the other hand, Japan OMRON development thinking is quite different, the same is committed to squeezing out the light extraction efficiency of the chip, OMRON that try to use planar light source technology, with LENS optical system chip light source for reflection, guidance and control for the traditional x2 bomb Type package structure of LED products common loss of light to further improve the design of its structure, the use of double-layer reflective effect and thus control and strengthen the LED light extraction, but the packaging technology is relatively more complex and costly, so most of the only LCDTV backlight module design.
LED lighting applications still need to improve the components of light fades and life issues
If you look forward to LED lighting into everyday lighting applications, its application to overcome the problem will be more! Because the daily lighting source will have a long time to use the situation, often open a continuous use for hours, or even dozens of hours, then the LED will be turned on for a long time due to the components of the heat caused by the chip's luminous attenuation, life expectancy reduction, Components must be better solutions for heat treatment in order to ease the light failure problems premature
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