Industry news


High power LED packaging technology

From: Data:07/08/2016

Abstract: the main is to introduce the high power LED chip package technology. Including the high power LED packaging requirements, the key technology of the package, the form of packaging, high power LED packaging technology process is simple. LED

process design including the design of the chip and the chip package. At present, high power LED packaging technology and its cooling technology is a hot research topic in today's society. Because of the high power LED packaging process is relatively simple, but the actual process is very complex. And LED packaging technology directly affects the service life of LED. So in the process of large power LED package, to take into account many factors, such as light, heat, electricity, machinery and many other factors. Considering the high power LED light decay, thermal to take into account the high power LED heat dissipation problem, electrical to take into account the design of high power LED drive power, machinery to take into account the encapsulation process LED packages and so on optics.

1 high power LED package requirements and key technology LED (high power)

with long life, low pollution, low power consumption, energy saving and anti shock, etc.. Compared with the traditional lighting appliances, (high power) LED not only has good color, high optical efficiency, high light efficiency, but also can meet the different needs of high color index. In spite of this, the high power LED packaging process has strict requirements.

embodied in: low cost; (2) system to maximize the efficiency; third, easy replacement and maintenance; (4) and a plurality of LED can realize modularization; the heat transfer coefficient higher simple requirements.

according to the high power LED packaging technology to consider various factors, the key technology in the package also put forward several points. Mainly include:

(1) in the high power LED heat dissipation: considering the low thermal resistance package. LED chip is a solid-state semiconductor device, is the core part of LED light source . Due to the large power LED chip size is different, and in the drive mode is used to drive the constant current mode. Can directly convert electric energy into light energy so the LED chip needs to absorb most of the electrical energy input during the light process, which will generate a lot of heat in the process. So, for large power LED chip cooling technology is an important technology of LED packaging technology, but also in the high power LED package must be solved in the process of key issues. The heart of

(2) LED is a semiconductor chip, one end of the chip is attached to a support , one end is a negative electrode, and the other end is connected to the positive electrode of the power supply. So the high rate of light taking an important key technology of package structure is high power LED package. In the LED chip light emitting process, in the launching process, due to the refractive index at the interface will bring the different photon reflection loss and may cause total reflection loss, so it can be relatively high transparent adhesive in the chip surface is coated with a layer of refraction rate.

this layer of transparent plastic must have its high transmittance, high refractive index, good mobility, easy to spray, thermal stability, and so on. At present, a transparent adhesive layer commonly used epoxy resin and silica gel of the two kinds of materials.

2 LED encapsulation

with the development of science and technology, LED packaging forms have many kinds of, pin package surface, chip package and chip on board assembly direct encapsulation and encapsulation type package.

small power LED package is generally used in the form of pin LED package. Pin LED package is also relatively common. Ordinary light-emitting diode are basically the use of pin package. Pin type LED package heat is emitted from the anode pin rack to the PCB board, the heat dissipation problem is also relatively good solution. But there are some disadvantages, that is, the thermal resistance is relatively large, the service life of LED is short.

surface mount chip package (SMT) is a new type of LED package, it is the LED device has been packaged to a fixed position of the packaging technology. SMT packaging technology has the advantages of high reliability, easy automation, high frequency characteristics. LED SMT package form is the most popular in the electronics industry, a kind of chip packaging technology.

board on chip direct installed type (COB) led packaging technology is a direct mount technology, the chip is directly bonded on the printed circuit board, and wire suture. Finally, organic glue chip and wire protective packaging process. COB technology is mainly used in high power LED array. Have a high degree of integration.

system package (SIP) LED packaging technology is developed in recent years, the technology.

it is mainly in line with the requirements of the system portable and miniaturization of the system. Compared with other LED packages, the integration of SIP package is the highest, and the cost is relatively low. A plurality of LED chips can be assembled in one package.

in the actual application process, according to the requirements of the experiment, the author uses is the form of SMT package. Due to the high power LED packaging process, to take into account the factors of high power LED heat dissipation, I use the aluminum substrate cooling mode of the traditional way. We found through the practical application, SMT packaging technology to meet the requirements of the actual cooling. Specific physical aluminum substrate heat sink in the physical diagram shown in figure 1.

3 high power LED process LED

package is a multi-disciplinary process technology. As the research content involves optical, thermal and electrical, mechanical, materials, semiconductor etc.. So the packaging technology of high power LED is a complicated and comprehensive subject. Good LED package needs to consider the factors of the various disciplines into. Here is a brief introduction of the LED packaging process flow. Its flow chart is shown in figure 2. LED

light emitting body is a chip, different chip prices are different, the size of the form is not a. The chip size is not the same, which brings some difficulties to the LED package. In the selection of the stent is also put forward a test.

stent and the choice of the shape of the plastic mold determines the size of the finished product LED package. Support LED chip, so the stent should be selected according to the size of the actual length of LED wafer. The choice of

solid crystal glue is mainly to consider its bond strength, and its particle size. The degree of thickness of the coated solid crystal glue also determines the thermal resistance of the package LED.

the author chooses the solid crystal glue as the silver colloid. Compared with the insulating rubber, the silver colloid has a low thermal resistance. The size of thermal resistance determines the light efficiency of LED. Similarly, silver glue has another characteristic, that is, good thermal conductivity.

welding line process can use mechanical and manual welding line, due to the experimental production of the LED package is less, so the use of artificial welding line. As early as the high-power microscope, the polarity of the chip using gold wire welded to the bracket two pins on the corner. The welding process should be patient and careful. The entire LED packaging process is in accordance with the process shown in Figure 2.

4 conclusion LED

packaging process must take into account a variety of factors, each link must be carefully considered. The thermal resistance affects the efficiency of LED. Effects of heat dissipation conditions and color stability on the performance of LED. We have to choose the right material in the LED packaging process. Improve the existing device structure, to seek a better way of LED heat dissipation, reduce the thermal resistance of LED and so on. (heat dissipation substrate, phosphor , potting glue) material selection is very important in the packaging process, but the thermal interface, optical interface is equally important. For LED lamps , not only to consider the above factors, but also the LED drive power supply, module integration, the application of the field are set together to consider. Therefore, the research for high power LED packaging technology in this area, go15