In recent years, with the LED in the device materials, chip technology, packaging process technology and other aspects of continuous improvement, especially the gradual maturity of the chip and phosphor coating technology diversification, a new chip size package CSP ( Chip Scale Package technology came into being. Due to its unit area of the luminous flux maximization (high light density) and the maximum cost of chip and packaging BOM cost (low package cost) so that it is expected to open in the lm / $ subversive breakthrough. Recently, CSP in the industry caused a greater discussion, it is not only a variety of packages, but also by industry expectations, is considered a "ultimate" package.
First, the status of white LED package
       At present, lighting has become the main market for LED drivers. From the LED lighting market penetration can be seen, LED lighting market has experienced a replacement lamp, integrated LED lighting, and the next generation of intelligent lighting applications three stages of development. According to a number of industry analysis company predicted that by 2020 in the LED lighting market penetration rate will reach 70%, LED integrated light source in the lamp design will play an increasingly important role.
       Throughout the development of white LED packaging process, in order to meet the needs of LED applications continue to update, LED package also experienced from high-power package to the small and medium-power package center of gravity shift. And promote the trend of the main reasons for this trend, it is from 0.2W ~ 0.9W low-power LED for diffuse (diffuse) light demand; LCD TV LED backlighting the rapid industrialization; bulb and lamp and other alternative lamps On behalf of the rapid penetration of the lighting market; and 5630,4014,2835,3030 PLCC standardization and other market applications to promote. At the same time, with the commercial lighting and special lighting diversification needs, the next package trend is high-density package, and COB, CSP is to achieve high-density package representative form.
1, low-power SMD will still play an important role
       Over the past few years, the performance of small and medium-power LED chip has been rapidly improved, packaging costs continue to improve, so that the luminous efficiency (lm / W), especially in the cost-effective (lm / $) is better than ceramic high-power package. Coupled with its application for diffuse light sources, will remain mainstream in linear and surface light sources. At the same time, with the EMC and SMC and other high temperature, resistance to yellowing material in the QFN stent in the introduction of the stent package is a high-power expansion, has exceeded 2W level, forcing the ceramic high-power package to more power (3W ~ 5W) application Advance.
2, COB vigorously penetrate the business according to the market
        At the same time, another package form of COB gradually in the compact light-emitting surface, high light density applications reflect its unique advantages. COB can be a direct array of multiple chips arranged in the highly reflective metal or ceramic substrate, eliminating the single LED discrete packaging and then integrated; COB package design is simple, with good light and color space uniformity The improvement of its high-reflection metal or ceramic substrate material effectively solves the reliability problem such as the lifetime of MR16, PAR Reflector and other applications. With the flip-chip chip mature and no gold wire on the design of the flexibility, as well as the substrate material cooling and reflectivity increase, dozens or even hundreds of LED integrated into the same substrate has become possible, and thus To further achieve a high optical density, ultra-high power LED package, so that alternative ceramic metal halide lamp possible.
3, high-power discrete LED further miniaturization
        Over the past few years, Lumileds, Cree, OSRAM and other high-power LED suppliers have focused efforts to improve the original ceramic packaging technology, by virtue of its advanced high-power flip chip or vertical structure chip, gradually miniaturization of the package to reduce due to expensive ceramics Substrate and lower production costs brought about by the cost pressure, and enhance the chip to withstand high current density. For example, Cree's X-lamp series, without reducing or even increasing the luminous flux from the original 3535 to 2525, and then further reduced to 1616, approaching the size of the chip itself, or called Near Chip Scale Package ( NCSP). And the natural evolution of the next generation discrete (Discrete) high-power LEDs may be a CSP that will completely eliminate the ceramic substrate.
Second, the next generation of white packaging trends
        What is the CSP package? What is the difference with the NCSP? What are the advantages? IPC standard J-STD-012 CSP package is defined as the package area is not greater than 20% of the chip area.
1, CSP and NCSP (free substrate vs with substrate)
       When the ceramic substrate size and chip size is almost the same size, it gradually lost to help LED heat (thermal diffusion) function. On the contrary, if the removal of the ceramic substrate, then remove a layer of thermal interface, is conducive to the rapid conduction of heat to the circuit board. At the same time, with the flip chip mature, ceramic substrate as an insulating material on the PN electrode line re-distribution (re-distribution) function is no longer needed. In addition to the mechanical structure and thermal expansion mismatch on the LED play a protective role, the ceramic substrate on the chip isolation and thermal conduction of the important function has been basically lost.

        The GGI or AuSn eutectic soldering required to remove the substrate while the traditional ceramic package is solid can be changed to a low cost SAC solder. And with flip chip, remove the gold line and wire step, reducing the cost of packaging.

2, the advantages of white CSP
         In addition to the potential cost reduction advantages mentioned above, in the design of the lamp, due to the CSP package size greatly reduced, can make the lamp design more flexible, the structure will be more compact and simple. In the performance, due to the small SMD surface of the CSP, high light density characteristics, easy to optical point of control; the use of flip chip electrode design, so that the current distribution more balanced, suitable for greater current drive; Droop effect of the slow, The light absorption, so that CSP has to further enhance the luminous efficiency of the space. In the process, sapphire phosphor and chip MQW area to increase the distance, lower phosphor temperature, white light conversion efficiency is higher.
3, CSP process technology