Discussion on light LED package technology

Discussion on light LED package technology

Light LED package includes: bracket row packaging, chip packaging, module packaging, these packaging methods are common and commonly used by us.

conventional existing packaging methods and application areas

The bracket row package was the first to be 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 lights, urban lighting projects, advertising screens, barrier tubes, and traffic. Indicator lights, and some products and fields that are currently widely used in our country.

SMD light LED package (SMD) is a leadless package, small and thin, very suitable for keyboard display lighting of mobile phones, backlight lighting of TV sets, and electronic products that require lighting or instructions. In recent years, SMD package has become larger With the development of size and high power, three or four LED chips are encapsulated in one patch, which can be used to assemble lighting products. Module packaging is also a kind of multi-chip packaging. Dozens or hundreds of LED chips are packaged on an alumina or aluminum nitride substrate with a small size and high packaging density. The internal wiring is a hybrid type, namely There are multiple chips connected in series and several circuits connected in parallel. This kind of package is mainly to expand the power and use it as a lighting product. Due to the high packaging density of the module package, the heat generated during application is large, and heat dissipation is the primary problem to solve the application. The devices produced by the above packaging methods have a common feature when used in the production of lighting lamps: the number of thermal resistance channels is large, it is difficult to produce high-quality lighting lamps, and the connection between the module itself and the radiator has relatively high requirements. . All current packaging methods are to mix yellow phosphor (YAG) and epoxy resin uniformly in different proportions, directly point them on the blue-emitting LED chip, and then heat and cure. The advantage of this common approach is to save materials, but the disadvantage is that it is not conducive to heat dissipation and the phosphor will also age. Because epoxy resin and phosphor are not materials with good thermal conductivity, and wrapping the entire chip will affect heat dissipation. This method is obviously not the best solution for manufacturing LED lighting fixtures.

At present, the high-power chips produced abroad, the white light chips above 0.5 watts are all coated with a uniform layer of YAG phosphor paste on the blue chip, and it looks like a yellow cube on the outside (except for the two gold chips used for welding). The pad has no phosphor. This method can improve the light efficiency than the previous commonly used method, so it is widely used abroad.) When packaging, only the white light chip is soldered on the designed circuit board, eliminating the need for coating Phosphor process. This brings convenience to lighting manufacturers, but the current domestic chip suppliers cannot produce such LED white light chips in large quantities.

my country is the country that developed LED street lights earlier, and it is currently used well in the country. The reason is that the country attaches importance to the “low-carbon economy.” Feasibility, my country is a breakthrough in the application of street lights, while foreign countries (OSRAM, Nichia, Samsung, etc.) are using indoor lighting as a breakthrough. Which of these two routes has more advantages is still unclear. As far as our country is concerned, the application direction of LED street lamp lighting is the result of national conditions. The reason is that my country’s national income is low, and the cost of LED indoor lighting is relatively high, which ordinary people cannot accept. The use of LED street lights is the government’s money, and LED street light manufacturers have taken a fancy to this point. In fact, the working conditions of LED street lights are more demanding and more demanding than indoor LED lighting fixtures. If the quality can be achieved (heat dissipation, service life, color rendering, reliability, etc.), then it is easier to make indoor LED lights. NS. At present, foreign LED giants are launching hundreds or even thousands of LED indoor lighting fixtures, the price is between 20-75 US dollars, and the power ranges from a few watts to 20 watts. But the packaging methods they use are all mentioned above. The only Philips company that coats phosphors on the LED lampshade was rated as one of the most innovative LED lighting products in 2009.

The author believes that all LED lighting fixtures should be manufactured with multi-chip packaging and module packaging (module packaging is a high-density multi-chip packaging), and it is best that the LED chip is directly packaged on the main body of the lamp, so that the thermal resistance The number of channels is the least, and better heat dissipation effect can be achieved. Or a circuit body coated with copper foil is made on the main body of the lamp, its thermal resistance is also low, and the power of the LED lighting must be at least a few watts or more, so they are all used in multi-chips. The previous packaging process is not applicable and must be used. New methods and processes. Using multiple packaged LED devices to assemble LED lights is difficult to produce high-quality and highly reliable LED lights. I hope that technical personnel engaged in the manufacture of LED lights can understand this.

The innovation of phosphor coating process

For the phosphor coating of the module light LED package, what we have seen so far is that the phosphor paste is directly coated on the chip. The phosphor of the same module is still relatively consistent, but for mass production, different modules may appear. The better way is to use LED phosphor film or diaphragm. The film and diaphragm can be produced on a large scale with good consistency. LED lights are all multi-chip packages. The light emitted is mixed with each other and undergoes fluorescence. The powder film or film is converted into white light, and the chromatic aberration can be eliminated. The requirements for films and diaphragms are:

  1. It can transmit light, the thickness is between 0.1 —- 0.5mm, the phosphor is uniform, and the appearance is flat.
  2. High light conversion efficiency, good stability, long life, and good aging resistance.
  3. Can be made with or without a base, and can also be made into a thin sheet, depending on the implementation conditions and cost. The film base is required to be colorless, transparent and anti-aging.
  4. Convenient processing and forming, arbitrary size cutting, low cost.

Another method is to mix phosphor and transparent plastic in proportion, and directly produce a lamp shade with phosphor through an injection molding machine and a mold, and the lamp shade converts blue light into white light. This is more trouble-free and more convenient. Since the lampshade converts the mixed blue light, the output white light has no chromatic aberration, and the light is softer and will not produce glare.

Maturity of heat sink Technology used in light LED package

In order to better solve the problem of LED heat dissipation, the design and packaging of the lamp should be considered together, and the light LED package and the heat sink for LED heat dissipation should be integrated to effectively reduce the number of thermal resistance. This is a very effective and improved method. Ways to dissipate heat from lamps.

The current LED fluorescent lights on the market do not have a heat sink, and such lamps cannot achieve high power, high quality and long life. The correct product design should also consider the heat sink. Industrial production is to extrude a semi-circular finned aluminum profile with a die for the heat sink of the LED fluorescent lamp, and then cut the required length according to the size of the power, and then make it. Aluminum-based copper foil circuit, the chip is fixed on the copper foil, connected with gold wire or fixed with a bonding machine. This kind of lamp has good heat dissipation effect, only two thermal resistances, one or two thermal resistances less than common packaging methods, effectively reducing the temperature of the chip, and improving the quality and life of the LED fluorescent lamp.

Discovery and operation of new materials

Another method is to design protrusions on the aluminum profile, mill out many rectangles as needed, and use ordinary (0.8-1.0mm thick) PCB circuit boards to open rectangular holes according to the rectangle of the aluminum profile, and paste or paste the PCB circuit boards. Riveted on the aluminum profile, the LED chip is fixed on the rectangular projection on the aluminum profile, and then the circuit on the LED PCB board is connected to the chip with a gold wire. This kind of production process is the best, with only one thermal resistance, and the best heat dissipation effect. Manufacturers producing LED lights should give priority to this scheme, followed by the method of making copper foil lines on aluminum profiles. Only such an innovation can effectively solve the heat dissipation problem of LED strip lamps and improve the quality and lifespan of LED fluorescent lamps.

Constantly exploring and improving technology, the future development of LED lighting is showing a trend of bright sunshine.

 

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