Exploring the methods and applications of LED packaging
LED packages are: bracket row package, chip package, module package several, these packaging methods are common and commonly used by us.
A conventional conventional packaging method and application field
Bracket row package is the earliest use, used to produce a single LED device, this is our common lead-type light emitting diode (including piranha package), it is suitable for instrument indicator, city lighting project, advertising screen, retaining pipe, traffic Indicators, and some products and fields that are currently applied in China.
SMD (SMD) is a leadless package that is small and thin, suitable for keypad display lighting of mobile phones, backlighting for TVs, and electronic products that require lighting or indication. In recent years, SMD packaging has become increasingly large. With the development of size and high power, three or four Led chips in one chip package can be used to assemble lighting products. The module package is also a multi-chip package. Dozens or hundreds of LED chips are packaged on aluminum oxide or aluminum nitride substrates with a small size and a high packaging density. The internal wiring is a hybrid type, that is, There are multiple chips in series and several parallel circuits. This package is mainly to expand the power used as a lighting product. Due to the high density of the package and the large amount of heat generated during application, the heat dissipation of the module package is the primary issue for the application. The devices produced by the above packaging methods have a common feature for producing lighting fixtures: the number of thermal resistance paths is large, it is difficult to produce high-quality lighting fixtures, and the connection between the module itself and the radiator is relatively high. . At present, all the packaging methods are to mix the yellow phosphor (YAG) and the epoxy resin in different ratios, point directly to the blue LED chip, and heat and cure. This common practice has the advantage of saving material, the disadvantage is not conducive to heat dissipation, the phosphor will also be aging. Epoxy and phosphors are not good materials for heat conduction, and enveloping the whole chip will affect heat dissipation. This method is obviously not the best solution for manufacturing LED lighting fixtures.
At present, high-power chips produced abroad, white-light chips of more than 0.5 watts are all coated with a uniform layer of YAG phosphor paste on a blue chip, which looks like a yellow cube, except for the two golds used for soldering. The pad has no phosphor. This method can improve the light efficiency compared with the methods commonly used in the prior art. Therefore, it is widely used abroad.) Soldering this white chip to a designed circuit board can eliminate the need for coating. Phosphor process. Bringing convenience to lighting manufacturers, but the current domestic production of chip suppliers can not mass production of such LED white chips.
China is an early country to develop LED street lamps, and it is also used well in China. The reason is that the country attaches importance to the "low-carbon economy." In 2009, China introduced ten cities and thousands of LED street lamps. Many cities have experimental sections to test LED street lamps. Feasibility, China's application of street lamps as a breakthrough, and foreign (Osram, Japan, Samsung and other companies) is based on the indoor lighting as a breakthrough, these two routes who actually have more advantages, it is not yet clear. As far as China is concerned, LED lighting is the first application direction, which is due to the national conditions. The reason is that China's national income is relatively low, and the cost of LED interior lighting is relatively high, and ordinary people cannot accept it. The use of LED street lamps is the government's money, and LED street lamp manufacturing companies have taken a fancy to this point. In fact, the working conditions of LED street lamps are more demanding and demanding than that of indoor LED lighting fixtures. If quality clearance (heat dissipation, service life, color rendering, reliability, etc.) can be achieved, then it will be easier to make indoor LED lighting. Now. At present, foreign LED giants are introducing a large number of hundreds or even thousands of LED indoor lighting fixtures, the price between 20-75 US dollars, power from a few watts to 20 watts. However, the packaging methods they used are all mentioned earlier. The only Philips company that applied phosphors to the LED shades was named one of the most innovative LED lighting products in 2009.
The author believes that: All LED lighting lamps should be manufactured using multi-chip package and module package (module package is a high-density multi-chip package), and it is best that the LED chip is directly encapsulated in the lamp body, so thermal resistance The number of channels is at a minimum and good heat dissipation can be achieved. Or the circuit body coated with copper foil on the main body of the luminaire has a lower thermal resistance, and the power of the LED lighting is at least several watts or more, so all of them are used on multiple chips. The previous packaging process is not applicable and must be adopted. New methods and processes. It is difficult to create LED lamps with high quality and high reliability by assembling LED lamps with a plurality of packaged LED devices. It is hoped that technical personnel engaged in the manufacture of LED lamps can understand this point.
Second, the innovation of phosphor coating process
Module coating of phosphor coating, the current see is still the fluorescent paste directly coated on the chip, the same module phosphor is still more consistent, but for mass production may appear different modules With eyes to see the difference, it is better to use LED phosphor film or film, film and film can be large-scale production, good consistency, LED lights are multi-chip package, the light emitted by mixing with each other, after the fluorescence The powder film or diaphragm is converted to white light, and the color difference can be eliminated. The requirements for films and films are:
1 Through the light, the thickness is between 0.1----0.5mm, the phosphor is even and the appearance is smooth.
2 The light conversion efficiency is higher, the stability is better, the service life is longer, and the aging resistance is good.
3 can be made with a base film and no film, can also be made of thin slices, see the implementation conditions and costs. The requirements for the film base are colorless, transparent and anti-aging.
4 Easy to process and shape, arbitrary cutting and low cost.
Another method is to mix the phosphor and the transparent plastic in proportion, and directly produce a lampshade with fluorescent powder through an injection molding machine and a mold. The lampshade converts the blue light into white light. In this way, it is more convenient and convenient. Since the shade converts the mixed blue light, the output of the white light is no color difference, and the light is soft without glare.
Third, in order to better solve the problem of LED heat dissipation , lamp design and packaging should be taken into account together. The heat sink of the package and LED heat dissipation should be integrated to effectively reduce the number of thermal resistance paths. This is a very effective and effective method. Lamp cooling method.
At present, LED fluorescent lamps on the market do not have heat sinks. Such lamps cannot achieve high power, high quality, and long lifespan. The correct product design should consider the heat sink together. The industrialized production is the radiator of the LED fluorescent lamp. The semi-circular finned aluminum profile is extruded with a die, and the required length is cut according to the size of the power and then produced. Aluminium-based copper foil lines are fixed on the copper foil, and they are connected by gold wires or by a binding machine. Such a lamp has a good heat dissipation effect, and has only two thermal resistances, one to two thermal resistances less than the commonly used packaging methods, which effectively reduces the temperature of the chip and can play a role in improving the quality and life of the LED fluorescent lamp.
Another method is to design the ribs on the aluminum profiles, and mill as many rectangles as necessary. Paste the Pcb circuit boards with a regular (0.8-1.0mm thick) Pcb circuit board in accordance with the rectangular shape of the aluminum profile to open the square holes. Riveted in the aluminum profile, LED chip is fixed on the aluminum profile on the rectangular platform, and then use the gold wire to connect the circuit board and chip. This kind of production process is the best, with only one thermal resistance and the best heat dissipation effect. Manufacturers of LED lamps and lanterns should give priority to this kind of scheme, followed by the method of making copper foil lines on aluminum profiles. Only such innovation can effectively solve the problem of heat dissipation of LED strip-shaped lamps and lanterns, and can improve the quality and life of LED fluorescent lamps.
Constantly exploring and enhancing technology, the future development of LED lighting presents a bright future.
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