As the power density of chips continues to increase, especially the development of semiconductor lighting technology, new and higher requirements are placed on the optical, thermal, electrical and mechanical structures of LED packages.
The development of high-efficiency technology can foresee that existing packaging processes and packaging materials are not suitable for future packaging requirements. As the quantum efficiency of the chip increases, the amount of heat generated is reduced, and the effective current density of the active layer of the chip is greatly increased. The overall heat generation of the chip is reduced, so the heat dissipation area requirement for the package form is also reduced. The heavy heat dissipation package structure currently used will undergo a large change, so the efficiency of the LED chip is greatly reduced, and the chip area is greatly reduced, thereby changing the package. In such a way that the light output of a single device is greatly increased, the area of a single high-efficiency LED chip is now greatly reduced (250 mil 2 = 60 LM). The lack of heat and the high luminous flux requirements for a single LED source make integrated packaging mainstream. The thermal aggregation effect of the integrated packaged LED device makes the overall thermal conductivity of the LED device extremely important. Packaging technology that can significantly reduce thermal resistance may become the mainstream of LED chip packaging technology. Flip-chip reflow soldering technology will solve the problem of chip yield and cost, which will revolutionize the cost of packaging and make non-gold wire soldering. The technology of flip chip packaging technology is applied on a large scale. Of course, silica gel molding technology like PC hardness and aspherical secondary optical lens technology will become the basis of LED packaging technology. The directional quantitative dispensing process, the graphic coating process, the secondary electrostatic spray powder process, the film lamination method, the three-primary phosphor coating process, the chip deposition pressurization method and the like, all of which will be applied in the LED packaging process. It will improve the light extraction efficiency and light color distribution of LED devices.
The development trend of SMD
The SMD package, short for Surface Mounted Devices, means: surface mount device, which is one of the SMT (Surface Mount Technology) components. At present, SMD is the largest product of packaging technology. In particular, the 2835 package type currently occupies the mainstream lighting market. It is predicted that SMD will be the mainstream of LED in the next five years, but will gradually reduce the ratio, but there will still be opportunities to maintain half of the country. In the future, SMD will have the following trends to meet the competition of other technologies:
a) Medium power becomes the mainstream packaging method. At present, most of the products on the market are high-power LED products or low-power LED products. Although they have their own advantages, they also have insurmountable defects. The medium-power LED products that combine the advantages of both have emerged as the mainstream packaging method.
b) The application of new materials in packaging. Materials such as Epoxy Molding Compound, thermoplastic PCT, modified PPA, and ceramic-like plastics will be widely used due to higher and better environmental resistance such as high temperature resistance, UV resistance, and low water absorption.
c) Compared with PPA or ceramic substrate, EMC packaging scheme is mainly made of epoxy resin material, which makes it easier to realize large-scale large-scale production demand, and the expansion of throughput can further reduce manufacturing cost, and epoxy resin material application. More flexible, not only can the size be easily redesigned, but also the material is smaller and easier to cut. The design of the terminal components is more flexible and flexible. The finished terminal light source assembly can drive high watts in a small volume. The number, especially in the light source of 0.2W~2W, is very competitive.
The development trend of COB
At present, COB applications are gradually gaining popularity. With the advantages of low thermal resistance, good light type, no soldering, and low cost, COB applications will continue to penetrate in the future. The COB packaging process has many advantages, and the link surface soldering is removed. The COB packaging process directly fixes the LED bare chip to the pad, so the heat dissipation area is larger than the conventional packaging process, and the material has a high thermal conductivity. , heat dissipation is good. This is also a factor that guarantees the highest weight among the high reliability factors of the COB package. The COB package eliminates the need for the lamp bead surface reflow soldering process, which no longer causes the high temperature in the reflow oven of the conventional packaging process to fail the LED chip and the bonding wire. In addition, the integrated packaged light engine with other components is also a great advantage of COB. The integrated packaged light engine may be one of the mainstream of future COB technology.
SIP (System in Package) is a new type of package integration developed on the basis of the system chip System on Chip (SOC) in order to meet the requirements of portable development and system miniaturization of the whole machine in recent years. For SIP-LEDs, not only can multiple light-emitting chips be assembled in one package, but also various types of devices (such as power supplies, control circuits, optical microstructures, sensors, etc.) can be integrated into one. For a complex, complete system. Compared with other package structures, SIP has good process compatibility (can use existing electronic packaging materials and processes), high integration, low cost, more new functions, easy block testing, short development cycle, etc. . Of course, the parameters of COB in terms of light efficiency and luminous density are also the focus of attention. According to reports, under the high light color quality of Ra>80 and R9>0, the current highest COB data of domestic COB is as high as 162lm/W, the highest lumen density. It can reach 88lm/mm2, but under the light efficiency of 105lm/W, the lumen density can reach 220lm/mm2, which is still quite different from the creek of 280lm/mm2 in the United States, but it is close to the level of international manufacturers.